Digitized by the Internet Archive in 2020 with funding from Getty Research Institute https://archive.org/details/practicalmetalwoOObyrn THE PRACTICAL METAL-WORKER’S ASSISTANT: COMPRISING METALLURGY CHEMISTRY, TnE ARTS OP WORKING ALE METALS AND ALLOYS, FORGING OP IRON AND STEEL, HARDENING AND TEMPERING, MELTING AND MIXING, CASTING AND FOUNDING, WORKS IN SHEET METAL, THE PROCESSES DEPENDENT ON THE DUCTILITY OP THE METALS, SOLDERING, AND THE MOST IMPROVED PROCESSES, AND TOOLS EMPLOYED BY METAL-WORKERS. WITH THE APPLICATION OP THE ART OF ELECTRO-METALLURGY MANUFACTURING PROCESSES: COLLECTED FROM ORIGINAL SOURCES, AND FROM THE WORKS OF HOLTZAPFFEL, BERGERON, LEUPOLD, PLUMIER, NAPIER, SCOFFERN, CLAY, FAIRBAIRN, AND OTHERS. BY OLIYEE BYRNE. A NEW, REVISED, AND IMPROVED EDITION. TO WHICH IS ADDED -AKST APPENDIX, CONTAINING THE MANUFACTURE OF RUSSIAN SHEET IRON. By JOHN PERCY, M.D., F.R.S. THE MANUFACTURE OF MALLEABLE IRON CASTINGS, AND IMPROVEMENTS IN BESSEMER STEEL. By A. A FESQUET, Chemist and Engineer. With Six Hundred and Nine Engravings , illustrating every Branch of the Subject. PHILADELPHIA : HENRY CAREY BAIRD, INDUSTRIAL PUBLISHER, 406 Walnut street. 187 2 . co/vs TS J2.0S- 377 I87 2 - Entered according to Act of Congress, in the year 1864, by HENRY CAREY BAIRD, In the Office of the Clerk of the District Court in and for the Eastern District of Pennsylvania. STEREOTYPED BY 8. A. GEORGE, 607 SANSOM STREET, PHILADELPHIA. COLLINS, PRINTER. THE GETTY CfcMTER LIBRARY PREFACE. The Practical Metal-Worker’s Assistant, as now pre¬ sented to the public, possesses some very valuable and essential features not found in former editions, and which, it is believed, will render it even more useful in the future than it has been in the past, great as has been its popularity. Dr. Percy’s treatise on the Manufacture of Russian Sheet- Iron and Professor Pesquet’s treatises on the Manufacture of Malleable Iron Castings and Improvements in the Manufacture of Bessemer Steel, are one and all important, especially in this country, at the present moment, when a new era is opening upon us, under the beneficent and wise policy which gives some heed to our industries, and is producing such magnificent results. Under this policy, as is most evident, the various departments of the Iron and Steel manufacture are advancing with rapid strides towards such a position as, it is believed, must within two decades, if not sooner, place them at the head of those industries throughout the world. Not only in these, but in all of the other branches of metal working, must this volume prove an important aid to the practical workman. Philadelphia, March 1, 1872. (7) (Fig. 16), by means of which the flame and gaseous products evolved during the process may escape ; but the plashes of metal thrown up by jets of air are, for the most part, prevented from escaping by the serpentine form of these outlets in the con¬ verting vessel. Having thus minutely described this apparatus, let us follow its author through the process. When the chamber is about half-filled with fluid metal drawn from a smelting or remelting furnace, atmos¬ pheric air, either in a cold or heated state, or gaseous products capable of evolving combustion of the carbon contained in the iron, is blown or forced into and among the fluid metal; and this is found suf¬ ficient to keep up the required temperature during the process. The size and number of jets or tuyere-pipes required for this purpose vary according to the quantity of metal operated upon at a time, and also with the condition and quality of the metal ; thus forge, pig, or refined plate metal, will not require so much oxygen to complete its carbonization and conversion into malleable iron, as is required for the conversion of crude iron of the quality known as No. 1 or No. 2 foundry-iron. To these qualities of metal a tuyere is required having an outlet larger by about twenty per cent, than is used for the white qualities of iron. The patentee hesitates, however, in giving any fixed rule where so much de¬ pends upon the force or pressure of the blast and the quality of the iron, preferring to give the following example from his own practice as a guide to the workmen. “ When using foundry-iron of the quality No. 2,” he says, "I run one ton into the converting vessel, in which it rises to the height of about a foot above the orifices of the tuyere pipes; and then force into the fluid metal, atmospheric air in its natural state, under a pressure of about ten pounds to the square inch, employing from six to twelve tuyere- pipes for its distribution, the united area of the pipes being two square inches. The quantity of blast admitted by this area of inlet, will in general be found sufficient to effect the conversion of the crude iron into a malleable condition in about thirty minutes. Where a mixture of oxygen gas with atmospheric air or steam, or steam alone; or where other gaseous fluids capable of evolving oxygen are preferred in lieu of atmospheric air; then the size of RECENTLY PATENTED REFINING PROCESSES. 67 the tuyere-pipes should be regulated according to the quantity of oxygen present, diminishing the area of the pipes where the oxy¬ gen is in excess, and increasing the area where the quantity is short of the above proportion.” When the vessel is new, or newly lined, it may be heated by the waste gases of the blast-furnaces, or any other convenient means, previous to the crude iron being poured in. The patentee sums up the substance of his discovery in the following terms: “ It is well known that molten crude iron, under ordinary circum¬ stances, will soon become solidified unless a powerful fire is kept up, and is applied direct to the fluid metal, or to the exterior of the vessel containing it. It is also well known that if the quantity of carbon which is usually associated with crude iron is dimin¬ ished, that the temperature necessary to maintain its fluidity also rises in like manner, so that when iron has lost the whole or the greater part of its combined carbon, the metal can only be kept in a fluid state by the heat of powerful furnaces. But I have dis¬ covered that if atmospheric air or oxygen is introduced into the metal in sufficient quantities, it will produce a vivid combustion among the particles of fluid metal, and retain and increase its tem¬ perature to such a degree that the metal will continue fluid during its transition from crude iron to the shape of cast-steel or mallea¬ ble iron without the application of fuel, the high temperature being obtained by the oxygen uniting with and causing a com¬ bustion of the carbon in the crude iron, and by the combustion of small portions of the iron itself.” As a matter of convenience, the patentee suggests, while re¬ serving his right to apply modifications of the apparatus described, that the converting vessel should be placed near to the discharge- hole of the blast or remelting furnace, from which the crude iron is to be drawn; that the interior of the chamber should be heated by burning gases, or by introducing wood-charcoal or coke at the passages p (Fig. 16); and that a blast of air be turned on through the tuyere-pipes, by which their combustion may be kept up and the vessel dried before turning the crude metal into it. For this operation the vessel is placed in the position shown by Fig. 16, having a movable gutter leading from the tap-hole of the smelting furnace into the upper end of one of the passages p, the tuyere pipes being now in operation. As soon as the metal covers the orifices of the tuyere-blocks, a violent ebullition is produced, the air dividing into globules, and diffusing itself among the particles of fluid iron, and thus coming in contact at numerous points with the carbon consumed in the crude iron, and producing thereby a vivid combustion, while the gaseous products escape by the pas¬ sages p. In about fifteen minutes from the time of commencing the pro cess, large frothy slags are thrown violently out of the passages p, accompanied by a rush of bright flame. After a few minutes’ duration this eruption ceases, but copious flame still continues to 68 THE PRACTICAL METAL-WORKER’S ASSISTANT. escape by the passages. At this stage of the process the crude metal has thrown off the bulk of its impurities, and is, in all prob¬ ability, in the state of cast-steel; its exact state, however, can be ascertained by turning the handle-shaft f so as to bring the vessel round on its axis, as in Fig. 17, when a portion of the metal may be discharged into an ingot-mould, wdiere it is quickly cooled and examined. If not sufficiently decarbonized, the vessel is restored to its original position, and the process continued until completed, —from five to ten minutes’ blowing being generally found sufficient to convert the metal from the condition of cast-steel to malleable iron. When it is necessary to suspend the operation of blowing for a short time, the vessel should be brought into a position half¬ way between Figs. 16 and 17, so that the orifice of the tuyere- pipes maybe above the surface of the metal, otherwise the tuyeres will be stopped up with the fluid metal. The whole process of conversion from crude pig-iron No. 1 to malleable iron, occupies from thirty to thirty-five minutes, varying according to the quality of the pig; but the exact point when the process should cease, will soon be acquired by the workmen, since the color and volume of the flame issuing from the passages vary with the condition of the metal, thus forming a good guide for the workmen; while the facility with which trial-ingots may be taken affords an in¬ fallible test. The heat, in some cases, is so excessive that the metal, even when reduced to malleable iron, is still so far above the melting point that its temperature requires to be reduced before casting. For this purpose, the vessel is brought into the position half-way between that shown in Figs. 16 and 17, the tuyeres being above the surface of the metal, the supply of air stopped, and a fire-brick placed over the orifice of the passage p, so as to prevent the heat from escaping with too much rapidity. In this way the tempera¬ ture gradually subsides, and the metal is brought into a proper state for casting; or, if that is preferred, for taking out of the ves¬ sel in masses after cooling down by stirring. We have now to deal with a part of the refining process in which it occurs to us that Mr. Bessemer has been altogether mis¬ understood, both by those who have criticised his inventions most severely, and by the general public. The notion generally enter¬ tained, we believe, is that by means of combustion alone, and with¬ out fuel, that gentleman professes to produce malleable iron. This is not so. He only professes to have discovered, that the rapid union of carbon and oxygen which takes place at the temperature which has now been attained, still further increases the tempera¬ ture of the metal, while the diminished quantity of carbon present allows a part of the oxygen to combine with the iron, which un¬ dergoes combustion, and is converted into an oxide. At the excessive temperature which the metal has now acquired, he continues, the oxide undergoes fusion, and forms a powerful solvent of those earthy bases that are associated with the iron RECENTLY PATENTED REFINING PROCESSES. 69 The violent ebullition which is going on mixes most intimately the scoria and metal, every part of which is thus brought in con¬ tact with the fluid oxide, which will thus wash and cleanse the metal most thoroughly from the silica and other earthy bases which combined with the crude iron, while the sulphur and other atile matters which cling so tenaciously to iron at ordinary tem¬ peratures are driven off, the sulphur combining with the oxygen and forming sulphurous acid gas,—producing by this means a purer iron by the application of atmospheric air to the fluid metal than could be produced in the puddling-furnace by a large con¬ sumption of that costly material. Beyond that, the process recom¬ mended very much resembles the mechanical appliances by which malleable iron is produced by the older methods: namely, by sub¬ jecting the ingots at a welding heat to a forge-hammer or squeezer of a peculiarly powerful construction. During the interval occupied in cooling down the boiling metal, the workman has to prepare his ingot-moulds. A convenient mode of doing this is to place them in an iron truck, mounted on wheels, which may be moved under the spout of the vessel, and passed out under the arched openings left in the furnace. The ingots thus prepared, are now in a fit state for being hammered, tilted, or rolled into bars, rods, or plates. In some cases the ingots are found to contain cells and cavities; in this case they are sub' jected at a welding heat to the action of squeezers, or they art) subjected, in a suage or die, to repeated blows under a powerful hammer, so that the parts are forcibly driven together, and the cells welded before being subjected to the rolling-mill or tilt- hammer. The squeezers, and other apparatus recommended by Mr. Besse¬ mer, differ considerably from those generally in use. The squeezer has transverse grooves, both on the upper and lower jaws, as repre¬ sented in Fig. 18: A A being the grooves or hollows, B an ingot Fig. 18. placed between the jaws. In this operation the ingot, or mass of metal, is brought to such a temperature in a suitable furnace as 70 THE PRACTICAL METAL-WORKER’S ASSISTANT. will .sufficiently soften it to admit of its being pressed into a solid homogeneous body. The same effect may be produced by hammering the ingot on a suage or die, as illustrated in Fig. 19, where P represents the lower portion of a steam-hammer, having a grooved block Q fitted into it; a similar block N is se¬ cured to a heavy mass of metal 0, which forms the bed of the hammer; M being a wrought-iron hoop, lined with steel, which is made so as to slide up or down by means of the rods S. The workman, having heated the ingot G, holds it with a pair of tongs in the groove of the lower block, while the upper one falls upon it with such force as is necessary. By the use of these grooved surfaces, or suages, the ingot of metal less liable to be crushed than when ham- 1S mered between two parallel flat surfaces, which give no support to its sides. In this operation the work¬ man will move the ingot backwards and forwards, turn it over on its side, and so work and compress the metal while at a welding heat, as thoroughly to solidify the iron and render it fit for Fig. 20. the tilt hammer or rolling-mill. Other modifications of the steam-hammer are mentioned by Mr. Bessemer, all however having one principle, viz., that the ingot is placed upon a block or anvil, supported on both sides by strong rests, while the hammer falls into the groove formed by these sup¬ ports. By this means the tendency of the ingots to crush out lat¬ erally is prevented, while the metal is left at liberty to expand itself in length, thus undoubtedly encouraging the fibrous condition insep¬ arable from malleable iron. This effect is produced by many modifications of apparatus, the details of which are unimportant, provided the dies or suages are so constructed, and the ingot of spongy or cellular metal so confined, that when the hammer is brought forcibly in contact with it the tendency is to have its various parts forcibly squeezed, pressed, or driven together, the pores closed, and the surfaces united or welded together. In the probationary state of these patented processes it is im¬ possible to draw any decided conclusions as to their probable re¬ sults. There is that in Mr. Bessemer’s process which has strongly impressed the public mind, and which only the conviction of com¬ plete success or failure will satisfy. While the popular view has thus, sometimes with little knowledge of the subject, magnified the discovery far beyond its merits, there have not been wanting others who would divest it of any merit whatever, and treat it as alto¬ gether unworthy of serious consideration. As in most other cases, truth seems to lie between these extremes. We have already seen that the principal impurities in cast-iron RECENTLY PATENTED REFINING PROCESSES. 71 consist of carbon, sulpliur, phosphorus, silicon, and some other substances of less importance. These substances, Mr. Bessemer asserts, combine with oxygen at a high temperature, forming vola¬ tile compounds, which are incapable of again entering into com¬ bination with the metal. The principle of Mr. Bessemer’s process is to take advantage of this tendency of the substances to unite with oxygen. By forcing atmospheric air into the fluid metal, in¬ tense combustion is produced; the volatile gases unite with the oxygen, and disappear through the channels prepared for their exit. This, say some of the objectors, is unsound in theory—that practically neither sulphur nor phosphorus, the two substances most injurious to iron, are separated by the process. In support of these views, a writer in the “ Birmingham Jour¬ nal,” to whom we are indebted for some excellent remarks on this process, some of which have been imported into these pages, thus reiterates his objections. Recurring to objections formerly urged against the process in the pages of the same journal, the writer says: “Especially important too, is it, that accurate chemical analysis should be resorted to, to show the composition of this iron, and to prove that the new process will truly purge it of sulphur and phosphorus, as we understand Mr. Bessemer to say it will—ele¬ ments, the presence of one per cent, of which is fatal to the quality of the iron. “ So far as we are aware, this important information has not been communicated to the public; and so long a time has now elapsed that we despair of receiving it from the quarter it was most natu¬ rally expected from. In the hope of contributing to the settle¬ ment of a question which has already too long disturbed the public mind, we have imposed upon ourselves a task which we think should have been spared us, and present to our readers such an analysis of Mr. Bessemer’s iron as we have been daily hoping to see published by that gentleman himself. The specimen we have experimented upon possesses those physical properties which, from repeated descriptions, the public are sufficiently familiar with. The iron consists of an agglutinated mass of large brilliant crys¬ talline grains, possessed of a very imperfect malleability ; flatten¬ ing under the blow of a hammer ; but almost invariably cracking at the edges. It is wholly destitute of a fibrous structure, and only after having been repeatedly heated and drawn out in a smith’s forge, exhibits the properties of an inferior wrought iron. On analysis it was found to have the following composition: Iron.98‘9 Phosphorus.P08 Sulphur.0J6 Carbon.0‘05 Silicon.traces 100-12 72 THE PRACTICAL METAL-WORKER’S ASSISTANT. “ This composition is so accordant with the physical properties of iron, that, the composition being given, the chemist would have no difficulty in predicating its more marked characteristics. Its crystalline structure and fusibility are very satisfactorily accounted for. In order more exactly to illustrate the nature of the change effected by Mr. Bessemer’s treatment, we append an analysis of refined iron produced at a large establishment in the neighborhood of Birmingham. We are indebted to the courtesy of Dr. Percy for this analysis. It was made in his laboratory by one of his assistants, Mr. Dick. The iron was obtained only a few months ago, and may be regarded as representing the average composition of refined iron as made at the present moment in this neighbor¬ hood : Iron.95’14 Carbon (combined).3‘07 Phosphorus.0’734 Silicon.0‘63 Sulphur.0T57 Manganese.trace Residue, insoluble in hydrochloric acid . 053 100261 The residue, insoluble in hydrochloric acid, yielded: Silica .0-3 Alumina, with a little peroxide of iron . . 0‘14 0-44 “ In contrasting the change effected by Mr. Bessemer’s treatment with that of the refinery, the following particulars force themselves strongly upon our notice. Mr. Bessemer’s method removes most effectually the carbon and silicon, while in the refinery these are but little diminished. The carbon is eliminated with a perfection which we should scarcely have thought possible, but we are with¬ out information as to the sacrifice at which this has been effected. The amount of iron oxidized by the vivid combustion which Mr. Bessemer induces, we are unable to ascertain. The point which most prominently strikes the chemist in Mr. Bessemer’s iron, is the large amount of phosphorus which it contains—an amount utterly fatal, we fear, to the value of Mr. Bessemer’s method. His treatment, we suspect, does not sensibly diminish the amount of this element; but this, too, is a point on which we must be dependent on Mr. Bessemer. We have had no opportunity of examining the slag produced in the treatment; but we learn from an eminent chemical authority, that at least one sample of it con¬ tains no sensible amount of phosphoric acid. We have previously explained that it is by the puddling process that the phosphorus and sulphur are mainly removed ; the chemical examination of the tap-cinder of the puddling furnace disclosing an abundance of phosphoric acid. As yet, so far as we can learn, Mr. Bessemer has RECENTLY PATENTED REFINING PROCESSES. 73 done nothing towards the removal of this pernicious element, phos¬ phorus ; and in this important respect his process must be re¬ garded as a failure.” We have elsewhere incidentally alluded to the strange oversight committed by the objectors to Mr. Bessemer’s process—all allusion to his hammering and squeezing processes are invariable suppressed; consequently certain magical results are expected, to which, as it appears to us, he does not lay claim. On the contrary, his specifi¬ cation distinctly claims the peculiar squeezing and hammering process already described; lateral compression and elongated fibrous expansion being the results sought for. It is true, he only mentions this portion of his improvements incidentally, when he claims for the new process facilities for forming large masses of iron capable of producing bars that could not have been obtained by the old process by means of powerful machinery not yet matured, whereby great labor will be saved and the operation greatly expedited. It is obvious, therefore, that great importance is attached by the pat¬ entee to the subsequent operations. Nevertheless, with all our desire to see Mr. Bessemer’s process crowned with success, we can¬ not avoid seeing that it has yet much to overcome. Early in Oc¬ tober, Mr. Bessemer sent ingots of his pneumatically refined iron to the Dowlais iron-works, where it was operated upon, the result being a fair-faced iron, equal, apparently, on the outer surface, to any ever rolled. It stood the lever or dead test well; but the sharp blow of the ram, and the sharp squeeze of the eccentric straightener, it could not bear, for which its steely or crystalline structure prob¬ ably accounts. Practical men observed, that along the surface of the rail a stratum of fibrous iron—evidently the result of elongation through the rolls—presented itself; and this was considered great encouragement for Mr. Bessemer to prosecute his idea to perfection. In reference to this railway bar, Mr. Bessemer states, that it was rolled direct from a ten-inch square ingot, having passed through the rolls fourteen times. The metal was not previously piled or in any way wrought; but, notwithstanding the extremely difficult sec¬ tion, not the smallest portion of the flange was torn up. To render the fabrication of the same form of rail practicable on the old plan, twice-rolled iron is used to form the flange, and ten shillings per ton extra is being paid for it in consequence. The process is stated to have been successfully applied to the manufacture of iron for tin-plating. The best puddle-iron has heretofore failed to produce the requisite toughness, and charcoal- smelted iron has in consequence been used for this purpose at a considerable extra cost per ton; but we have examined sheets rolled from ingots prepared by the new process, remarkable for their thinness, and affording proofs of the great ductility and tough¬ ness of its product. We have also inspected, as instances of the extreme tenacity capable of being produced by this process, rolled out metal of such extreme thinness and pliability as to bear, when annealed, a close 74 THE PRACTICAL METAL-WORKERS ASSISTANT. resemblance in fabric to paper, with much greater toughness and tenacity. We shall conclude these remarks by quoting the concluding portion of Mr. Bessemer’s address to the British Association :— “ One of the most important facts,” he says, “ connected with the new system of manufacturing malleable iron is, that all the iron so produced will be of that quality known as charcoal iron; not that any charcoal is used in its manufacture, but because the whole of the processes following the smelting of it are conducted entirely without contact with, or the use of, mineral fuel. The iron result¬ ing therefrom will, in consequence, be perfectly free from those in¬ jurious properties which that description of fuel never fails to impart to iron that is brought under its influence. At the same time, this system of manufacturing malleable iron offers extraordi¬ nary facility for making large shafts, cranks, and other heavy masses; it will be obvious that any weight of metal that can be founded in ordinary cast-iron by the means at present at our dis¬ posal may also be founded in molten malleable-iron, and be wrought into the forms and shapes required, provided that we increase the size and power of our machinery to the extent necessary to deal with such large masses of metal. A few minutes’ reflection will show the great anomaly presented by the scale on which the con secutive processes of iron-making are at present carried on. The little furnaces originally used for smelting ore, have from time to time increased in size, until they have assumed colossal proportions, and are made to operate on 200 or 300 tons of materials at a time, giving out ten tons of fluid metal at a single run. The manufac¬ turer has thus gone on increasing the size of his smelting furnaces, and adapting to their use the blast apparatus of the requisite pro¬ portions, and has, by this means, lessened the cost of production in every way ; his large furnaces require a great deal less labor to produce a given weight of iron, than would have been required to produce it with a dozen furnaces; and in like manner he dimin¬ ishes his cost of fuel, blast, and repairs, while he insures a uniform¬ ity in the result that never could have been arrived at by the use of' a multiplicity of small furnaces. While the manufacturer has shown himself fully alive to these advantages, he has still been under the necessity of leaving the succeeding operations to be carried out on a scale wholly at variance with the principles he has found so advantageous in the smelting department. It is true that hitherto no better method was known than the puddling pro¬ cess, in which from 400 to 500 weight of iron is all that can be operated upon at a time, and even this small quantity is divided into homoeopathic doses of some 70 lbs. or 80 lbs., each of which is moulded and fashioned by human labor, carefully watched and tended in the furnace, and removed therefrom one at a time, to be carefully manipulated and squeezed into form. When we consider the vast extent of the manufacture, and the gigantic scale on which the early stages of the progress are conducted, it is astonishing REFINING AND WORKING OF IRON. 75 that no effort should have been made to raise the after processes somewhat nearer to a level commensurate with the preceding ones, and thus rescue the trade from the trammels which have so long surrounded it.” CHAPTER IV. REFINING AND WORKING OF IRON. The iron furnaces of the United States are, generally speaking, superior to those of England or the rest of Europe. On this point and for the smelting of iron we refer our readers to “ Overman on the Manufacture of Iron,” and will here introduce one of the many American improvements in refining. This is a method of making wrought-iron directly from the ore, patented by Alex¬ ander Dickerson, of Newark, N. J., 22d July, 1850. We have seen some of the iron produced—it is apparently of the best qualitv. Of this furnace, Fig. 21 represents a side view when complete. Fig. 22, a longitudinal section of the same. Fig. 23, top view of Fig. 23. Fig. 21. cylinders, partly open. Figs. 24, and 25, large and small water piates occupying places F and E respectively, through which small jets of water continually flow, to prevent the flame from burning the 76 THE PRACTICAL METAL-WORKER’S ASSISTANT. cylinders. L and M, two upright cylinders, standing on the water plates ; and between which cylinders in space B are placed in equal Fig. 24. Fig. 25. Fig. 22. alternate layers, the pulverized ore and charcoal, or 25 per cent, in weight of anthracite if that is substituted for charcoal. The escape heat passes through an opening P in the arch freely through space C between the masonry work I) and the outer cylin¬ der L, and also within the inner cylinder M through space A, whereby the ore mixed with the coal is completely and uniformly surrounded by the flame of heat and deoxidized, and yet perfectly protected from the air, flame and noxious gases. When thus deox¬ idized, one charge of the ore, by elevating valve R, is readily pre¬ cipitated on the preparatory bottom G; where it is stirred and freed from the small particles of coal that accompany it from the cylin¬ ders. It is then passed over on the puddling bottom G, where it is further stirred and made up into balls, when it is ready for the hammer or rolls. In the fire chamber 0, the heat and flame may be produced from w r ood, anthracite or bituminous coal. The whole furnace much resembles an elongated ordinary pud¬ dling furnace, with the addition of a preparatory bottom, over which are placed the cylinders and their appendages. While in operation, the cylinders are charged from the top with the ore and coal pulverized and mixed. The cylinders are kept at a red heat. The ore is thoroughly deoxidized in them, and de¬ posited from them in successive charges on the preparatory and puddling bottoms, as rapidly as the balls are taken from the latter for the hammer or rolls. Thus the operation is continuous and economical, as only the escape heat of the furnace is employed in the cylinders. REFINING AND WORKING OF IRON. 77 The whole is easily managed and worked, the operation is steady, and the product certain and uniform. The iron produced is represented to be extremely pliable, ductile, and malleable, and applicable to all the arts. It is produced at a saving of about 40 per cent, of any other process. A ton and a half of anthra¬ cite coal, and two and half to three tons of ore make a ton of blooms in twelve hours. A furnace complete costs from $1,200 to $1,500. Manufacture of Malleable Iron. —Formerly, wrouglit-iron was obtained either directly from the ore, or from cast-iron, by a process still in extensive operation, in which wood charcoal is re¬ quired. Puddling. —The crude cast-iron is remelted in quantities of from half a ton to one ton, in a furnace called the chafery, or re¬ finery, blown with blast; it is kept fluid for about half an hour, and then cast into a plate about four inches thick, which is purer, finer in the grain than pig metal, and also much harder and whiter; it is then called refined metal. The plate when cold is broken up, and from two to four hundred weight of the fragments, with a certain proportion of lime, are piled on the hearth of the puddling furnace, which is a reverberatory furnace without blast. In about half an hour the iron begins to melt, and whilst it is in the semi-fluid state, the workman stirs and turns it about with iron tools; he also throws small ladles full of water upon it from time to time. In this condition the metal appears to ferment, and heaves about from some internal change; this is considered to arise from the escape of the carbon in a volatilized form, which ignites at the surface with spirits of blue flame: in about twenty minutes the pasty condition gives way, and the iron takes a granulated form without any apparent disposition to cohesion ; the fire is now urged to the utmost, and before the metal becomes a stiff conglomerated mass, the workman divides it into lumps or balls of about fifty pounds in weight. These balls are taken out one at a time, and shingled, or worked under a massive helve or forge-hammer, that weighs six or eight tons, and is moved by the steam-engine: this compresses the ball, squeezes out the loose fluid matter, and converts it into a bloom, or short rudely-formed bar. The bloom is then raised to the welding heat in a reheating furnace, and again passed under the hammer, or through grooved rollers, or it is submitted to both processes, by which it is elongated into a rough bar. The shingling is sometimes performed by large squeezers, somewhat like huge pliers, or by roughened rollers that also serve to compress the iron; but the ponderous flat-faced helve is considered the more effectively to expel the dross and foreign matters from the bloom, and to weld the same more perfectly at every point of its length. The machine for compressing and rolling puddler’s balls, in¬ vented by John E'. Winslow of Troy, New York, is very effective and possesses many advantages, of which may be mentioned: 1. 78 THE PRACTICAL METAL-WORKER’S ASSISTANT. Great expedition in shingling puddler’s iron, one of these machines being sufficient to do the work of twenty-five puddling furnaces. 2. The saving of shinglers’ wages; no waste of iron; turning out the blooms while very hot, enabling the roller to reduce them to very sound bars. 3. The ends of the blooms are thoroughly up¬ set, a very small amount of power operates the machine, and little or no expense for repairs. The nature of the first part of this invention consists in rolling and compressing puddler’s balls or loops of iron into blooms, etc,, by means of a rotating cam-formed compresser, combined with two or more rollers placed near to one another, and at the same distance from the axis of motion of the compresser, so that the compression and elongation of the loops will be due entirely to the eccentricity of the compresser, the whole being so geared that the rollers shall turn in the direction opposite to the motion of the compresser, that the loop may be rotated and retained between the rollers and the compresser: the surfaces of the rollers are formed with slight pro¬ jections to take hold of and turn the loop of iron, and the surface of the cam-formed compresser with teeth, which are very large at first, or on that part of the compresser which first acts on the loop, to squeeze out the impurities, and at the same time insure the turning of the loop, and then gradually diminished until the surface becomes quite or nearly smooth to finish the bloom. And the second part of this invention consists in combining with the compresser and rollers two cheeks, one on each side, and provided with springs that force them towards one another that they may yield to the ends of the loop of iron as it is lengthened out by the action of the compresser and rollers, and at the same time to make sufficient resistance to give a proper form to the ends of the blooms, etc. And the third part of this invention consists in combining with the compresser and rollers a feeder or sliding frame, operated by a projection on the compresser or the shaft thereof, to carry in the ball of iron between the compresser and roller, as that part of the compresser which is recessed for that purpose comes round to the • proper place for the introduction of the ball, and the discharge of the bloom ; and also in combining in like manner a follower for discharging the bloom after it has been completed. (a) represents the frame of the machine properly adapted to the intended purpose, but which may be varied at pleasure. In ap¬ propriate boxes ( bb ) between the standards of this frame run the journals of an eccentric roller (c), the periphery of which is cam- formed and provided with cogs, for the purpose of squeezing the ball of iron and forcing out the impurities, and gradually reducing its diameter and elongating it. Below this squeezing roller are arranged two fluted rollers (dd) whose journals are fitted to ap¬ propriate boxes in the frame. These rollers constitute the concave on which the ball of iron rests during the operations of the squeezer ; cog wheels (efg h ) being employed to connect the shaft REFINING AND WORKING OF IRON. 79 of the rollers with the shaft of the squeezer in such a manner that the peripheries of the two rollers (dd) shall turn in the same direction, and that of the squeezer in a reverse direction, and thus cause the ball or mass of iron during the operation of squeezing to rotate about its axis, or nearly so,—the requisite power for this purpose being communicated to the machine from some first mover in any efficient manner. One of the bottom rollers ( d ) has a strong flancli (i) on one side which projects sufficiently to pass within the periphery of that part of the squeezer which acts on the iron, 80 THE PRACTICAL METAL-WORKER’S ASSISTANT. after it has "been so much elongated as to have one of its ends ap* proach the flanch, and therefore towards the end of the operation of the squeezer that end of the bloom or mass of iron which is towards this flanch will be upset by it and properly formed. On the side of the machine opposite to the flanch (i) is a hammer (j) on the end of the bar (k) which slides in collars (l). The face of this hammer is smooth, and made as hammers for working iron usually are, and its edges are adapted to the peripheries of the two rollers ( dd) and to that part of the periphery of the squeezer which acts on the bloom at the time the hammer is to strike the ends of the bloom. A strong helical spring surrounds the bar (It) of the hammer, one end bearing against one of the collars (J), and the other against the back of the hammer, so that its tension will always force the hammer towards the flanch ( i) of the roller (d) ; and towards the outer end, the said bar (It) is provided with a spur (m), the inner face of which is slightly rounded to bear against the face of a cam (n), so formed that at each revolution of the bottom rollers it gives the hammer two blows upon the bloom, and at every revolution of the rollers the spring is liberated and the ham¬ mer strikes the bloom, and thus upsets the ends, the flanch ( i ) in this part of the operation performing the office of an anvil; the face of the cam is then made in the form of an inclined plane to draw back the hammer preparatory to another operation. Instead of forcing the hammer towards the bloom by a spring and drawing it back by a cam, this arrangement may be reversed by making the spring simply of sufficient length to draw back the hammer, and reversing the cam that it may force the hammer to¬ wards the bloom at the required time. And if desired, a lever, operated in any desired manner, such as by a cam or crank, may be used to operate the hammer instead of a cam, and under this latter modification the spring may be dispensed with altogether by connecting the hammer bar with the lever. The bars are next cut into short pieces, and piled in groups of four to six; they are again raised to the welding heat in a reheat¬ ing furnace, and passed through other rollers to weld them through¬ out their length, and reduce them to the required sizes; and some¬ times the processes of cutting and welding are again repeated in the manufacture of still superior kinds of iron. A similar process of manufacture is still carried on, partly with wood charcoal, in place of coals and coke; the iron thus manufac¬ tured, called charcoal iron, is much purer, but it is also more ex¬ pensive in England; it is sometimes, by way of distinction, left in ridges from the hammer, when it is called dented iron. The rollers or rolls of the iron works are turned of a variety of forms, according to the section of the iron that is to be produced; in general one pair is used exclusively for each form of iron re¬ quired ; although in the imaginary sketch, Fig. 27, it is supposed that the shaded portion represents the upper edge of the bottom roll; and that the top roll, which is not drawn, almost exactly meets the REFINING AND WORKING OF IRON. 81 bottom one, with the exception of the grooves, and which are in general turned partly in each roll, in the manner denoted by the black figures. Fig. 27. a b c d e f g h i One pair will have a series of angular grooves for square iron, gradually less and less, as a, b, c, Fig. 27, so that the bar may be rapidly reduced without the necessity for altering the adjustment of the rolls, which would lose much valuable time ; the flat bars are prepared square, and then flattened in grooves, such as that at d ; round, or bolt iron, requires semicircular grooves, e ; but round iron often shows a seam down one side, from the thin waste spread out between the rolls being afterwards laid down without being welded, when the iron is turned one quarter round and sent again through the rollers: therefore the best round works are mostly forged from square bars. Figs./and g are described as angle, and T iron; these are par¬ ticularly used in making boilers, the ribs of iron steam-vessels; also frames, sashes, and various works requiring strength with lightness. Plain cylindrical rollers serve for producing plate and sheet iron, which vary in thickness from one inch to that of writing-paper, and rolls turned like Fig. i, are employed for curvilinear ribbed plates, or the corrugated iron, an elegant application lately patented for roofs. Other rollers composed of two series of steeled discs, placed upon spindles, are used to slit thin plates of iron about six inches wide, into a number of small rods for the manufacture of nails, and similar rods are also made of larger sizes called slit iron, they always exhibit two ragged edges, and from being tied up in small parcels, are also known as bundle iron. Figs. 28 29 30 31 32 Figs. 28, 29, 30 and 31, represent four amongst numerous other sections of railway iron; these bars are produced in rollers turned with counterpart grooves; as before, the shaded portions represent fragments of the lower rollers, and the upper rollers are supposed to occupy the spaces immediately adjoining the section of the rails. For these also, three, four, or more grooves, varying gradually from that of the roughly prepared bar, to that of the finished rail, are employed, and this in like manner saves the necessity for adjusting the distance between the rollers during the progress of the work. 6 82 THE PRACTICAL METAL-WORKER’S ASSISTANT. All the foregoing rolls are supposed to be concentric, and to pro¬ duce parallel bars and plates of the respective sections; but in making fish-bellied railway bars (no longer used), taper plates for coach springs, and similar tapered works, the rollers, whether plain or grooved, are turned eccentrically, so as to make the works re¬ spectively thicker or deeper in the middle, as in Fig. 82; this re¬ quires additional dexterity on the part of the workman to introduce the material at the proper time of the revolution, upon which it is unnecessary to enlarge. * The general effect of the manufacture of malleable iron is to de¬ prive the cast-iron of its carbon; this is doner in the puddling fur¬ nace ; the original crystalline structure gives way to the fibrous, from the working under the hammer and rollers, by which every individual particle or crystal is drawn* out as it were into a thread, the multitude of which constitute the fibrous bar or metallic rope, to which it has some resemblance except in the absence of twist. The rod may now be bent in any direction without risk of fracture ; and the superior kinds, even when cold, may be absolutely tied in a knot, like a rope, when a sufficient force is applied. Should it however occur that the first operation, or shingling process, were imperfectly performed, the error will be extended in a proportional degree throughout the mass, which will account for the general continuance of any imperfection throughout the bar of iron, or a considerable length of the wire in which the reduc¬ tion or elongation is further extended; and to which evil all metals and alloys subjected to these processes of elongation are also liable. Malleable iron is divided into three principal varieties. First, red-short iron; secondly, cold-short iron; thirdly, iron partaking of neither of these evils, and which may be so far denominated pure malleable iron. The first kind is brittle when hot, but extremely soft and ductile whilst cold. This is considered to result from the presence of a little carbon. The cold-short withstands the greatesl degree of heat without fusion, and may be forged under the heaviest hammers when hot, but it is brittle when cold. This is attributed to the presence of a little silex. The third kind is considered to be en¬ tirely free from either carbon or silex, etc., and to be the pure sim¬ ple metal; but in the general way the characters of iron are intermediate between those described. From one and a half to two tons of pig-iron have been used to produce one ton of malleable iron ; but the average quantity is now from twenty-six to twenty-seven tons for each twenty tons of produce. The forge pig, ballast, and white cast-iron, is the kind principally used, as it contains least carbon, the whole of which should be ex- expelled in the,conversion of the cast metal into wrought-iron. It appears to be unnecessary to attempt any minute description of the different marks and qualities of iron. First, as these de¬ scriptions have been minutely given in many works ; and secondly, manufacture of steel. 83 as in common with most other articles, the quality of iron governs the price. I will only add, that little can be known of the character of iron from its outside appearance, beyond that of its having been well or ill manufactured, so far as regards its formation into bars. The smith is principally guided by the fracture when he breaks down the iron, that is, when the bar is nicked on opposite sides with the cold chisel, laid across the anvil upon a strip of iron near to the cut that it may stand hollow, and the blows of the pane of the sledge-hammer are directed upon the cut. The judgment will be partly formed upon the force thus re¬ quired in breaking the iron; the weakest and worse kinds will yield very readily,—when small, sometimes even to the blow of the chisel alone, and will then show a coarse and brilliant appear¬ ance, entirely granular or crystalline. This iron would be called very common and bad. If, on the other hand, the iron breaks with difficulty, and the line of separation, instead of being moder¬ ately flat, is irregular, or presents what may be called a hilly sur¬ face, the sides of which have a fibrous structure and a sort of lead- colored or a dull-gray hue, this kind will have a large proportion of fibre, and it will be called excellent tough iron. Other kinds will be intermediate, and present partly the crystalline and partly the fibrous appearance, and their relative values will depend upon how nearly they approach the one or other character. Another trial is the extent to which iron, when slightly nicked, may be bent to and fro without breaking. The coarse brittle kind will scarcely bend even once, whereas superior kinds, especially stub, charcoal, and dented irons, will often endure many deflections before fracture, and when nicked on the outside only and doubled flat together, will bend as an arch and partly split open through the centre of the bar, somewhere near the bottom of the cut made with the chisel, the entire fracture presenting the beautiful fibrous appearance and dull leaden hue before described. CHAPTER V. manufacture of steel. Steel is manufactured from pure maiieao e iron by the process called cementation. The Swedish iron from the Dannemora mines, marked with the letter L in the centre of a circle, and called “ Hoop L,” is generally preferred. Irons of a few other marks are also used for second-rate kinds of steel. The bars are arranged in a furnace that consists of two troughs, about fourteen feet long and two feet square. A layer of charcoal-powder is spread over the bottom, then a layer of bars, and so on alternately. The full 84 THE PRACTICAL METAL-WORKER’S ASSISTANT. charge is about ten tons. The top is covered over first with char¬ coal, then sand, and lastly with the waste or slush from the grind¬ stone trough, applied wet, so as to cement the whole closely down, for the entire exclusion of the air. A coal fire is now lighted below and between the troughs; and at the end of about seven days the bars are found to have in¬ creased in weight the one hundred and fiftieth part, by an absorp¬ tion of carbon, and to present, when broken, a fracture more crys¬ talline, although less shining, than before. The bars, when thus converted, are also covered with blisters, apparently from the ex¬ pansion of the minute bubbles of air within them ; this gives rise to the appellation, blistered steel. The continuance of the process of cementation introduces more and more carbon, and renders the bars more fusible, and would ultimately cause them to run into a mass if the heat were not checked. To avoid this mischief a bar is occasionally withdrawn and broken to watch the progress ; and the work is complete when the cementation has extended to the centre of the bars. The con¬ version occupies, with the time for charging and emptying the furnace, about fourteen days. A very small quantity of steel is employed in the blistered state, for welding to iron for certain parts of mechanism, but not for edge-tools. The bulk of the blistered steel is passed through one of the two following processes, by which it is made either into shear-steel or cast-steel. Shear-steel is produced by piling together six or eight pieces of blistered-steel, about thirty inches long, and securing the ends within an iron ring, terminating in a bar about five feet long by way of a handle. They are then brought to a welding heat in a furnace, and submitted to the helve or tilt hammer, which unites and extends them into a bar called shear-steel, from its having been much used in the manufacture of shears for cloth mills, and also German steel, from having been in former years procured from that country. Sometimes the bars are again cut and welded, and called double-shear steel, from the repetition. This process of working, as in the manufacture of iron, restores the fibrous character, and retains the property of welding: the shear steel is close, hard, and elastic ; it is much used for tools, composed jointly of steel and iron; its superior elasticity also adapts it t(? the formation of springs, and some kinds are prepared expressly for the same under the name of spring-steel. In making cast-steel, about twenty-six or twenty-eight pounds of fragments of blistered-steel, selected from different varieties, are placed in a crucible made of clay, shaped like a barrel, and fitted with a cover, which is cemented down with a fusible lute that melts after a time the better to secure the joining. Either one or two pots are exposed, to a vivid heat, in a furnace like the brass-founders’ air-furnace, in which the blistered-steel is thoroughly melted in the course of three or four hours; it is then removed by the workman MANUFACTUKE OF STEEL. 85 in a glowing state, and poured into a mould of iron, either two inches square for bars, or about six by eighteen inches, for rolling into sheet-steel. For large ingots the contents of two or more pots are run together in the same mould, but it requires extremely great care in managing the very intense temperature, that it shall be alike in both or all the pots. The ingots are reheated in an open fire much like that of the common forge, and are passed under a heavy hammer weighing several tons, such as those of iron-works; the blows are given gently at first, owing to the crystalline nature of the mass, but as the fibre is eliminated the strength of the blows is increased. Steel is reduced under the heavy hammer to sizes as small as three-quarters of an inch square. Smaller bars are finished under tilt hammers, which are much lighter than the preceding, move considerably quicker, and are actuated by springs instead of grav¬ ity alone; these condense the steel to the utmost. Rollers are also used, especially for steel of round, half-round, and triangular sec¬ tions, but the tilt hammer is greatly preferred. Cast-steel is the most uniform in quality, the hardest, and alto¬ gether the best adapted to the formation of cutting tools, especially those made entirely of steel; but much of the cast-steel will not endure the ordinary process of welding, but will fly in pieces under the hammer when struck. In respect, to steel, the same general remarks offered upon iron may be repeated, namely, that price in a great measure governs quality. Steel when broken does not show the fibrous character of iron, and in general the harder or harsher the steel, the more irregular r»r the less nearly flat will be its fracture. The blistered-steel should appear throughout its substance of an uniform appearance, namely, crystalline and coarse, much like infe¬ rior iron, but with less lustre and less of the bluish tint; when but partially converted, the film of iron will be readily distinguished in the centre. The blistered-steel when it has been once passed through the fire and well hammered, assumes as may be supposed a much finer grain, as in fact the operation converts it (although in the small way) into shear-steel. Shear-steel breaks with a much finer fracture, but the crystalline appearance is still readily distinguished. Cast-steel is in general the finest of all in its fracture, and unless closely inspected, its separate crystals or granulations should be scarcely observable, but the ap¬ pearance should be that of a fine, light slaty-gray tint, almost with¬ out lustre. The quality of steel is considerably improved, especially as re¬ gards cutting tools, when after being forged it is hammer-hardened, or well worked with the hammer until quite cold, as this tends to close the “ pores” and to make the material more dense; above all things excess of heat should be avoided, as it makes the grain coarse and shining, almost like that of bad iron, and which deteri¬ oration can be only partially restored, by good sound hammering under a peculiar management. The particular degrees of heat at 86 THE PRACTICAL METAL-WORKER’S ASSISTANT. which different samples of iron and steel, bearing the same name, should be worked, can only be found by trial; and it would be hardly possible to describe the shades of difference. It would have been incompatible with the nature of this work to have entered more largely into the manufacture of iron and steel, or to have attempted the notice of all the various alloys of steel which have received many attractive denominations, especially when so much has been already written on the subject. Of all the works published on the manufacture of iron and steel, those of the most importance are “Overman on Iron,” Lesley’s “Iron Manufacturers’ Guide,” Truran’s “Manufacture of Iron,” “ Reports of Experiments on Metals for Cannon,” by Officers IT. S. Army, Captain Rodman’s Reports on the same subject, “ Karsten on Iron,” and Dr. Hartmann’s “ Iron Manufacturers’ Hand Book,”* the two latter in German, and the collection of Mushet’s papers, which have appeared in the “Philosophical Magazine” at various times subsequent to 1798, and were collected and published by himself under the title “Papers on Iron and Steel.” Of the more brief and popular accounts of this subject, the best are Aikin’s Dictionary of Chemistry and Mineralogy; three vol¬ umes on the Manufactures in Metal, in Lardner’s Cyclopedia; and Ure’s Dictionary of Manufactures and Mines, which contain a very large store of information on the metals generally. The reader will also consult with advantage Aikin’s “Illustrations of Arts and Man¬ ufactures,” and an admirable article in Appleton’s “New American Cyclopedia.” CHAPTER VI FORGING IRON AND STEEL. In entering upon this subject, which performs so important and indispensable a part in every branch of mechanical industry, it is proposed first to notice some of the general methods pursued, com¬ mencing with the heaviest works, and gradually proceeding to those of the smallest proportions. This arrangement however shall not prevent us for greater convenience, giving in a chapter subse¬ quent to this general view, a very thorough one on Wrought-Iron in large Masses, alone. After this, the management of the fire, and the degrees of heat required for various purposes, will be described; and then the ele¬ mentary practice of forging will be attempted: those works made principally in one piece will be first treated of, and afterwards such as are composed of two or more parts, and which require the opera¬ tion o f welding. * A translation of this important work will shortly appear, from the In¬ dustrial Press of Henry Carey Baird, Philadelphia. FORGING IRON AND STEEL. 87 The heaviest works of all, are generally heated in air furnaces of various descriptions, some of which resemble but greatly exceed in size those employed in the works where iron is manufactured, and in which the process of forging may be truly considered to commence with the very first blow given upon the ball, as it leaves the puddling furnace for being converted into a bloom. At these works, in addition to the ordinary manufacture of bar, plate, and hoop iron in all their varieties, the hammer-men are em¬ ployed in preparing masses, technically called “uses," which mean pieces to be used in the construction of certain large works, by the combination or welding of several of these masses. A square shaft, to be used at an iron-works, was made by laying together sixteen square pieces, measuring collectively about twenty-six inches square, and six feet long. These were bound together, and put into a power¬ ful air furnace, and the ends of the group were welded into a solid mass under the heavy hammer weighing five tons; the weld was afterwards extended throughout the length. The paddle-shafts of the largest steam-ships are wrought by successive additions at the one end, as follows: A slab or use is welded on one side close to the end, and when drawn down to the common thickness, the additional matter becomes thrown into the length; the next use is then placed on the adjoining side of the as yet square shaft, and also drawn into the length, and so on until the full measure is attained. These ponderous masses are managed with far more facility than might be expected by those who have never witnessed such inter¬ esting proceedings. First, the “heat" has a long iron rod attached to it in continuation of its axis, to serve as a “porter ” or guide rod; the mass is suspended under a traversing crane at that point where it is nearly equipoised: the crane not only serves to swing it round from the fire to the hammer, but the traverse motion also moves the work endways upon the anvil, and small changes of elevation are sometimes affected by a screw adjustment in the suspending chain. The circular form is obtained by shifting the work round upon its axis by means of a cross lever fixed upon the porter, and moved by one or two men, so as to expose each part of the circum¬ ference to the action of the helve ; this is readily done, as the crane terminates in a pulley, around which an endless band of chain is placed, and the work lies within the chain, which shifts round when the work is turned upon the anvil: the precision of the forg¬ ings produced by these means is very surprising. (See p. 110). A similar mode of work is adopted on a smaller scale for many of the spindles, shafts, and other parts of ordinary mechanism, which are forged under the great hammer, often of several bars piled to¬ gether and fagoted; a suitable term, as they are frequently made of a round bar in the centre, and a group of bars of angular section, called mitre iron, around the same, which are temporarily wedged within a hoop, somewhat after the manner of a fagot of wood. Such works are likewise made of scrao-iron, which consists of a strange 88 THE PRACTICAL METAL-WORKER’S ASSISTANT. heterogeneous medley of odd scraps and refuse from a thousand works, scarcely two pieces of which are alike. A number of these fragments are enveloped in an old piece of sheet iron, and held together by a hoop, the mass is raised to the welding heat in a blast or air furnace, and the whole is consolidated and drawn down under the tilt-hammer; one long bar that serves as the porter being welded on by the first blow. The mingling of the fibres in the scrap-iron is considered highly favorable to the strength of the bar produced. The scrap-iron is sometimes twisted during the process of manufacture, to lay all the filaments like a rope, and prevent the formation of spills, or the longitudinal dirty seams found on the surface of inferior iron. Sometimes the formation of the scrap-iron is immediately followed by the production of the shafts and other heavy works for which it is required; at other times the masses are elongated into bars sold under the name of scrap-iron, although it is very questionable if all the iron that is so named is produced in the manner implied. The long furnaces are particularly well suited to straight works and bars, but when the objects get shorter and of more complex figures, the open fire or ordinary smith’s hearth is employed. This, when of the largest kind, is a trough or pit of brickwork about six feet square, elevated only about six inches from the ground; the one side of the hearth is extended into a vertical wall leading to the chimney, the lower end of which terminates in a hood usually of stout plate iron, which serves to collect the smoke from the fire. The back wall of the forge is fitted with a large cast-iron plate, or a back, in the centre of which is a very thick projecting nozzle also of iron, perforated for admitting the wind used to urge the fire; the aperture is called the tuyere. The blast is sometimes supplied from ordinary bellows of various forms; at other times, by three enormous air-pumps, which lead into a fourth cylinder or regulator, the piston of which is loaded with weights, so as to force the air through pipes all over the smithy, and every fire has a valve to regulate its individual blast; but the more modern and general plan is the revolving fan, also worked by the engine, the blast from which is similarly distributed. In some cases the cast-iron forge back is made hollow, that a stream of water may circulate through it from a small cistern; the water-back is thereby prevented from becoming so hot as the others, and its durability is much increased. In other cases the air, in its passage from the blowing apparatus, flows through chambers in the back plate so as to become heated in its progress, and thus to urge the fire with hot blast, which is by many considered to effect a very great economy in the fuel. Some heavy works of rather complex form, such as anchors, are most conveniently managed by hand forging; many of these require two gangs of men with heavy sledge-hammers, each consisting of six to twelve men, who relieve each other at short intervals, as the work is exceedingly laborious. Their hammers are swung round FORGING IRON AND STEEL. 89 and made to fall upon one particular spot with great uniformity; the conductor of this noisy, although dumb concert so far as relates to voice, stands at a respectful distance, and directs the blows of his assistants with a long wooden wand. The Hercules, or crane, used for transferring the work from the fire to the anvil, which is at about the same elevation as the fire itself, is still retained. The square shanks of anchors are partly forged under a vertical hammer of very simple construction, called a “ monkey .” It con¬ sists of a long iron bar running very loosely through an eye or aperture several feet above the anvil, and terminating at foot in a mass of iron, or the ram. The hammer is elevated by means of a chain, attached to the rod and also to a drum overhead, which is put into gear with the engine, and suddenly released by a simple contrivance, when the hammer has reached the height of from two to five feet, according to circumstances. The ram is made to fall upon any precise spot indicated by the wand of the foreman, as it has a horizontal range of some twenty inches from the central posi¬ tion, and is guided by two slight guy rods, hooked to the ram and placed at right angles; the guys are held by two men, who watch the directions given. This contrivance is far more effective than the blows of the sledge-hammers, and although now but little used is perhaps more suitable to such purposes than the helve or lift- hammer, which always ascends to one height, and falls upon one fixed spot. The square shank of the anchor, and works of the same section, are readily shifted the exact quarter circle, as the sling-chain is made with flat links, each a trifle longer than the side of the square of the work, which, therefore, bears quite flat upon one link, and, when twisted, it shifts the chain the space of a link, and rests as before. Many implements and tools, such as shovels, spades, mattocks, and cleavers, are partly forged under the tilt-hammer; the prepara¬ tory processes, called moulding, which include the insertion of the steel, are done by ordinary hand forging. The objects are then spread out under the broad face of the tilt-hammer, the workman in such cases being sometimes seated on a chair suspended from the ceiling, and, by paddling about with his feet, he places himself with great dexterity in front or on either side of the anvil with the progressive changes of the work: the concluding processes are mostly done by hand with the usual tools. A similar arrangement is also adopted in tilting small-sized steel. With the reduction of size in the objects to be forged, the num¬ ber of hands is also lessened, and the crane required for heavy work is abandoned for a chain or sling from the ceiling; but, for the majority of purposes, two men only are required, when the work is said to be two-handed. The principal, or the fireman, takes the management of the work both in the fire and upon the anvil; he directs and assists with a small hammer of from two to four pounds weight; the duty of his assistant is to blow the bellows and wield so THE PRACTICAL METAL-WORKER’S ASSISTANT. the sledge-hammer, that weighs from about ten to fourteen pounds, although sometimes more, and from which he derives his name of hammer-man. As the works to be forged become smaller, the hearth is gradually lessened in size, and more elevated, so as to stand about two and a half feet from the ground; it is now built hollow, with an arch beneath serving as the ash-pit to receive the cinders and clinkers. The single hearths are made about a yard square, and those forges which have two fires under the same hood, measure about two yards by one; a double trough, to contain water in the one com¬ partment and coals in the other, is usually added, and the ordinary double bellows is used. In proportion as the hearth is more elevated, so is the anvil likewise, that in ordinary use standing about two feet or two and a half feet from the ground, its weight being from two to four hundred-weight. Numerous small works are forged at once from the end of the bar of iron, which then also serves the office of the porter required for heavy masses; but when the small objects are cut off from the bar, or the pieces are too short to be held in the hand, tongs of different forms are needful to grasp the work. These are made of various shapes, magnitudes, and lengths according to circumstances ; but the annexed figures will serve to explain some of the most general kinds, although variations are continually made in their form to meet peculiar cases. Figs. 33 and 34 are called flat-bit tongs; these are either made to fit very close, as in Fig. 34, for thin works, or to stand more open, Figs. 34. 35. 36. 37. 38. 39. 40. Fig. 33. as in Fig. 33, for thicker bars, but always parallel; and a ring, or coupler, is put upon the handles, or reins, to maintain the grip upon the work; others of the same general form are made with hollow, half-round bits; but it is much better they should be angular, like the ends of Fig. 35, as then they serve equally well for round bars, FORGING IRON AND STEEL. 91 or for square bars held upon their opposite angles. Tongs that are made long, and swelled open behind, as in Fig. 35, are very excel¬ lent for general purposes, and also serve for bolts and similar objects with the heads placed inwards. The pincer tongs, Fig. 36, are also applied to similar uses, and serve for shorter bolts. Fig. 37 represents tongs much used at Sheffield, amongst the cutlers; they are called crook-bit tongs; their jaws overhang the side so as to allow the bar of iron or steel to pass down beside the rivet, and the nib at the end prevents the rod from being displaced by the jar of hammering; these are very convenient. Fig. 38, or the hammer tongs, are used for managing works punched with holes, such as hammers and hatchets: as the pins enter the holes, and maintain the grasp, they should be made stout and long, so as to admit of being repaired from time to time, as the bits get de¬ stroyed by the fire. Fig. 39, or hoop tongs, are very much used by ship-smiths, for grasping hoops and rings, which may be then worked either on the edge, when laid flat on the anvil, or on the side when upon the beak-iron: and lastly, Fig. 40 represents the smith’s ptliers, or light tongs, used for picking up little pieces of iron, or small tools and punches, many of which are continually driven out upon the ground in the ordinary course of work; they are also convenient in hardening small tools. In addition to the hearth, anvil, and tongs, the smithy contains a number of chisels, punches, and swages or striking tools, called also top and bottom tools, of a variety of suitable forms and gen¬ erally in pairs; these may be considered as reduced copies of the grooves turned in the rollers, and occasionally made on the faces of the tilt-hammers of the iron-works for the production of square, flat, round, T form iron, angle iron, and railway bars, as referred to. The bottom tools of the ordinary smith’s shop, have square tangs to fit the large hole in the anvil; in using them the fireman holds the work upon the bottom tool, and above the work he places the top or rod tool, which is then struck by the sledge-ham¬ mer of his assistant. In fitting the hazel rods to the top tools the rods are alternately wetted in the middle of their length, and warmed over the fire to soften them, that portion is then twisted like a rope, and the rod is wound once round the head of the tool and retained by an iron ferrule or coupler; a rigid iron handle would jar the hand. When these tools are used for large works, a square plate of sheet-iron, with a whole punched in the middle of it, is put on the rod towards the tool, to shield the hand of the workman from the heat; and it not unfrequently happens with such large works that the rod catches fire, and the tool is then dipped at short intervals in the slake trough to extinguish it. The smith who works without any helpmate is much more circum¬ scribed as to tools, and he is from necessity compelled to abandon all those used in pairs, unless the upper tools have some mechani- 92 THE PRACTICAL METAL-WORKERS ASSISTANT. cal guide to support and direct them. In addition to the anvil he only uses the fixed cutter and heading tools; he may occasionally support the end of the tongs in a hook attached to his apron¬ string, or suspended from his neck, whilst he applies a hand-chisel, a punch, or a name-mark in the left hand, and strikes with the hammer held in the right. The method is however ample for a variety of small works, such as cutlery, tools, nails, and small iron¬ mongery, which are wrought almost exclusively by the hand- hammer. Attempts to work small tilt-hammers with the foot have been found generally ineffective, as the attention of the individual is too much subdivided in managing the whole, neither is his strength sufficient for a continued exertion at such work; but the “ Oliver which we shall now describe, is one of the best tools of this class. The Oliver, or Small Lift-Hammer.— Fig. 41 represents a species of lift-hammer worked by the foot. The hammer head is about two and a half inches square and ten long, with a swage tool having a conical crease attached to it, and a corresponding swage is fixed in a square cast-iron anvil block, about twelve inches square, and six deep, with one or two round holes for punching, etc. The hammer handle is about two to two and a half feet long, and mounted in a cross spindle nearly as long, supported in a wooden frame between end screws, to adjust the groove in tho hammer face to that in the anvil block. A short arm, five or six inches long, is attached to the right end of the hammer axis, and FORGING IRON AND STEEL. 98 from this arm proceeds a cord to a spring pole overhead, and also a chain to a treadle a little above the floor of the smithy. When left to itself the hammer handle is raised to nearly a ver¬ tical position by the spring, and it is brought down very readily with the foot, so as to give good hard blows at the commencement of moulding the objects, and then light blows for finishing them. The machine was used when the author first saw it, in making long stout nails, intended for fixing the tires of wheels, secured within the felloes by washers and riveting;- the nails were made very nicely round and taper, and were forged expeditiously. For single hand-forging, the fire becomes still further reduced in size, and proportionally elevated from the ground. A portable forge of suitable dimensions for such work, and made entirely of iron, is represented in Fig. 42. The bellows are placed beneath the hearth and worked by a treadle. This forge is also occasionally fitted with a furnace for melting small quantities of metal, and with various apparatus for other applications of heat, such as soldering, either with a small charcoal fire, or a lamp and blowpipe, which are likewise urged with the 94 THE PRACTICAL METAL-WORKER’S ASSISTANT. "bellows. These applications, and also that of hardening and tem¬ pering tools, which will be severally returned to at their respective places, are much facilitated by the bellows being worked with the foot, as it leaves both hands at liberty for the management either of the work or fire, with the so-called fire-irons, which include a poker, a slice or shovel, and a rake, in addition to the supply of tongs of some of the former shown. The forge represented is sufficiently powerful for a moderate share of those works which require the use of the sledge-hammer ; but, when the latter tool is used, the anvil should not fall short of one hundred pounds in weight; and the heavier it is, the less it will rebound under the hammer. Management of the Fire : the degrees of heat.— The ordi¬ nary fuel for the smith’s forge is coal, and the kinds to be pre¬ ferred are such as are dense and free from metallic matters, as these are generally accompanied with sulphur, which is highly detrimental. Copper is usually forged in a coke fire—silver and gold in those made of charcoal; but the hearths do not materially differ from those used for iron. Compressed peat charcoal has been strongly recommended on account of its freedom from sulphur—one of the greatest enemies in nearly all metallurgic operations. The fire is sometimes made open, at other times hollow, or like a tunnel; and the larger the fire is required to be, so much the more distant is it situated from the tuyere iron. Before lighting the fire, the useful cinders are first turned back on the hearth, and the exhausted dust or slack is cleared away from the iron back and thrown into the ash-pit; a fair-sized heap of shavings is then lighted, and allowed to burn until the flame is nearly extinguished, when the embers are covered over with the cinders, and the bel¬ lows are urged A dense white smoke first rises, and, in two or three minutes, the flame bursts forth, unless the fire be choked, when the poker is carefully passed into the mouth of the tuyere. The work is now laid on the fire, and covered over with green or fresh coals, which are beaten around the tuyere and the work, the blast being continued all the while; the whole mass will soon be in a state of ignition. A heap of fresh coals is always kept at the outside wall of the fire, and they are gradually advanced at intervals into the centre of the flame to make up for those con¬ sumed. In making a large hollow fire, after a good-sized fire has been lighted in the ordinary way, the ignited fuel is brought forward on the hearth to expose the tuyere iron, into the central aperture of which the poker is introduced. A mass of small wetted coal is beaten hard round the poker to constitute the stock, the magnitude of which will depend on the distance at which the fire is required to stand off, and a second stock is also made opposite the first, the two resembling two hills with the lighted fuel lying between them. The durability of the fire will depend on the stocks being hard FORGING IRON AND STEEL. 95 rammed, which, for large works, is often done with the sledge¬ hammer. The work is now laid in the hollow just opposite the blast-pipe, and covered on its two sides and top with thin pieces of wood, and a heap of wetted coals is carefully banked up around the same and beaten down with the slice or shovel. When care¬ fully done, the heap is made to assume the smooth form of an em¬ bankment of earthwork. The bellows are blown gently all the time, and the work is not withdrawn until the wood is consumed, and the flame peeps through at each end of the aperture, so as to cake the coals well together into a hard mass; after which the work may be removed or shifted about without any risk of breaking down the fire. In localities where wood is scarce, small iron rods are placed around the principal mass, often designated the heat ; the small rods are first withdrawn when the fire has burned up, to allow room for the removal of the work. Sometimes when a fire is required only for hardening, the cen¬ tering of the arch is made entirely of wood, either in one or several pieces : and in this manner it may be built of any required form, as angular for knees, circular for hoops, and so on (although such works are usually done in open fires, which resemble the above in all respects, except the covering-in or roof): small coal is thrown at intervals into the hollow fire to replace -that which is burned, and by careful management one of these combustible edifices will last half a day, or even the entire day, without renewal. Occa¬ sionally, the stock around the tuyere iron will serve with a little repair for a second day, if, when the fire is turned back at night, that part is allowed to remain, and the fire is extinguished with water. When a small hollow fire is required, the same general methods are less carefully followed, and an iron tube introduced amidst the coals, makes a very convenient muffle or oven for some purposes. In forging, the iron or steel is in almost every case heated to a greater or less degree, to make it softer and more malleable by lessening its cohesion; the softening goes on increasing with the accession of temperature, until it arrives at a point beyond that which can be usefully employed, or at which the material, whether iron or steel, falls in pieces under the blows of the hammer, but which degree is very different with various materials, and even with varieties bearing the same name. Pure iron will bear an almost unlimited degree of heat. The hot short iron bears much less, and is in fact very brittle when heated. Other kinds are intermediate. Of steel, the shear-steel will gen¬ erally bear the highest temperature, the blistered-steel the ne^t, and the cast-steel the least of all. But all these kinds, especially cast-steel, differ very much according to the processes of manu¬ facture, as some cast-steel may be readily welded, but it is then somewhat less certain to harden p erfectly. Without attempting any refined division, I may add, the smith commonly speaks of five degrees of temperature, namely: 96 THE PRACTICAL METAL-WORKER’S ASSISTANT. The black-red heat, just visible by daylight; The low-red heat; The bright-red heat, when the black scales may be seen; The white-heat, when the scales are scarcely visible-; The welding-heat, when the iron begins to burn with vivid sparks. Steel requires on the whole very much more precaution as to the degree of heat, than iron. The temperature of cast-steel should not generally exceed a bright-red heat; that of blistered and shear-steel that of a moderate white-heat. Although steel cannot in consequence be so far softened in the fire as iron, and is therefore always more dense and harder to forge ; still from its su¬ perior cohesion it bears a much greater amount of hard work under the hammer when it is not over-heated or burned; but the small¬ est available temperature should be always employed with this material, as in fact with all others. It has been recommended to try by experiment the lowest de¬ gree of heat at which every sample of steel will harden, and in forging always to keep a trifle below that point. This proposal however is rarely tried, and still less followed, as the usual attempt is to lessen the labor of forging by softening the steel so far as it is safely practicable. Iron is more commonly worked at the bright-red and the white- heats, the welding-heat being reserved for those cases in which welding is required; or others in which, from the great extension or working of the iron, there is risk of separating its fibres or laminae, so as to cause the work to become unsound or hollow from the disrupture of its substance; whereas the same processes being carried on at the welding temperature, the work would be kept sound, as every blow would effect the operation of welding rather than that of separation. The cracks and defects in iron are generally very plainly shown by a difference in color at the parts when they are heated to a dull-red. This method of trial is often had recourse to in examining the soundness both of new and old forgings. When a piece of forged work is required to be particularly sound, it is a common practice to subject every part of the ma¬ terial in succession to a welding heat, and to work it well under the hammer, as a repetition of the process of manufacture to in¬ sure the perfection of the iron; this is technically called taking a heat over it —in fact, a heat is generally understood to imply the welding heat. For a two-inch shaft of the soundest quality, two and a half inch iron would be selected, to allow for the reduction in the fire and the lathe. Some also twist the iron before the ham¬ mering to prevent it from becoming “ spilly” The use of sand sprinkled upon the iron is to preserve it from absolute contact with the air, which would cause it to waste away from the oxidation of its surface, and fall oft' in scales around the anvil. If the sand is thrown on when the metal is only at the full ORDINARY PRACTICE OF FORGING. 97 red heat it falls off without adhering; but, when the white heat is ap¬ proached, the sand begins to adhere to the iron; it next melts on its surface, over which it then runs like fluid glass, and defends it from the air. When this point has been rather exceeded, so that the metal nevertheless begins to burn with vivid sparks and a hissing noise like fireworks, the welding temperature is arrived at, and which should not be exceeded. The sparks are, however, considered a sign of a dirty fire or bad iron, as the purer the iron the less it is subject to waste or oxidation, in the course of work. In welding two pieces of iron together, care must be taken that both arrive at the welding heat at the same moment; it may be necessary to keep one of the pieces a little on one side of the mo§t intense part of the fire (which is just opposite the blast), should the one be in advance of the other. In all cases, a certain amount of time is essential, otherwise, if the fire be unnecessarily urged, the outer case of the iron may be at the point of ignition before the centre has exceeded the red heat. In welding iron to steel, the latter must be heated in a considerably less degree than the iron, the welding heat of steel being lower from its greater fusi¬ bility. But the process of welding will be separately considered under a few of its most general applications, when the ordinary practice of forging has .been discussed, and to which we will now proceed. ORDINARY PRACTICE OF FORGING. The general practices of forging works from the bar of iron or steel are, for the most part, included in the three following modes: the first two occur in almost every case, and frequently all three together, namely: By drawing-down, or reduction; By jumping, or up-setting; otherwise, thickening and shortening; By building-up, or welding. When it is desired to reduce the general thickness of the object, both in length and width, then the flat face of the hammer is made to fall level upon the work; but, where the length or breadth alone is to be extended, the pane or narrow edge of the hammer is first used, and its blows are directed at the right angles to the direction in which the iron is to be spread. To meet the variety of cases which occur, the smith has hammers in which the panes are made in different ways—either at right angles to the handle, parallel with the same, or oblique. In order to obtain the same results with more precision and effect, tools of the same characters, but which are struck with the 7 98 THE PRACTICAL METAL-WORKER’S ASSISTANT. sledge-hammer, are also commonly used. Those with flat faces are made like hammers, and usually with similar handles, except that, for the convenience of reversing them, they are not wedged in; these are called set-hammers ; others, which have very broad faces, 3 re called flatters; and the top tools, with narrow round edges like the pane of the hammer, are called top-fullers. They all have the ordinary hazel rods. When the sides of the object are required to be parallel, and it is to be reduced both in width and thickness, the flat face of the hammer is made to fell parallel with the anvil, as represented in Fig. 43, or oblique, for producing taper pieces, as in Fig. 44, and. action and reaction being equal, the lower face of the work re¬ ceives the same absolute blow from the anvil as that applied above by the hammer itself. It is not requisite, therefore, to pre¬ sent every one of the four sides to the hammer, but any two at right angles to each other. This is only true for works of moderate dimensions; in large masses, such as anchors, the soft doughy state of the metal acts as a cushion, and greatly lessens the recoil of the anvil, and on this account such works are presented to the ham¬ mer on all four sides. It is also very injudicious in such cases to continue the exterior finish, or battering-off, too long, as this ex¬ tends the outer case of the metal more than the inner part, and sometimes separates the two. When imperfect forgings are broken in the act of being proved, the inner bars are sometimes found not to be even welded together, and the outside part is a detached sheath, almost like the rind or bark of a tree. In twisting the work round the quarter circle, some practice is called for, in order to retain the rectangular section, and not to allow it to degenerate into the lozenge or rhomboidal form, which error it is difficult to retrace. This indeed may be considered the first stumbling-block in forging, and one for which it is difficult to provide written rules. Of course in converting a round bar into a square with the ham¬ mer, the accuracy will depend almost entirely upon the change of exactly ninety degrees being given to the work, and this the experienced smith will accomplish with that same degree of feeling, or intuition, which teaches the exact distances required upon the finger-board of a violin, which is defined by habit alone. In the original manufacture of the iron, the carefully turned grooves, a, b, c, of the rollers, page 81, produce the square figure with great truth and facility; and under the tilt-hammer the two opposite sides are sure to be parallel, from the respective parallel¬ ism of the faces of the hammer and anvil; and the tietrs, from constant practice, apply the work with great truth in its second position. So that under ordinary circumstances the prepared ma¬ terials are true and square, and the smith has principally to avoid losing that accuracy. First, he must acquire the habit of feeling when the bar lies per¬ fectly flat upon the anvil, by holding it slenderly, leaving it almost ORDINARY PRACTICE OF FORGING. 99 to rotate in liis grasp, or in fact to place itself. Next, lie must cause the hammer to fall flat upon the work; with which view he will neither grasp its handle close against the head of the hammer, nor at the extreme end of the handle, but at that intermediate point where he finds it comfortably to rebound from the anvil, with the least effort of, or jar to his wrist. And the height of the wrist must also be such as not to allow either the front or back edge of the hammer-face to strike the work first, which would in¬ dent it, but it must fall fair and parallel, and without bruising the work. Figs. 43. 44. 45. It would be desirable practice to hammer a bar of cold iron, or still better one of steel, as there would be more leisure for obser¬ vation, the indentations of the hammer could be easily noticed; and if the work, especially steel, were held too tightly, or without resting fairly on the anvil, it would indicate the error by addi¬ tional noise and by jarring the wrist; whereas, when hot, the false blows or positions would cause the work to get out of shape, with¬ out such indications. As to the best form of the hammer, there is much of habit and something of fancy. The ordinary hand-hammer is represented in Figs. 48 and 44, but most tool makers prefer the hammer without a pane, and with the handle quite at the top, the two forming almost a right angle, or from that to about eighty degrees; and sometimes the head is bent like a portion of a circle. Similar but much heavier hand-hammers, occasionally of the weight of twelve or fourteen pounds, are used by the spade-makers for planishing; but the work being thin and cold, the hammer rises almost ex¬ clusively by the reaction, and requires little more than guidance. Again, the farriers prefer for some parts of their work, a hammer the head of which is almost a sphere; it has two flat faces, one rounded face for the inside of the shoe, and one very stunted pane at right angles to the handle, used for drawing down the clip in front of the horse-shoe; in fact, nearly a small volume might be written upon all the varieties of hammers. To return to the forging: the flat face of the hammer should not only fall flat, but also centrally upon the work; that is, the centre of the hammer, in which point the principal force of the blow is concentrated, should fall on the centre of the bar otherwise that edge of the work to which the hqjnmer might lean would be the more reduced, and consequently the parallelism of the work would 100 THE PRACTICAL METAL-WORKER’S ASSISTANT. be lost. It would also be bent in respect to length, as the thinned edge would become more elongated, and thence convex; and when the blows were irregularly scattered, the work would become twisted or put in winding, which would be a still worse error. I will suppose it required to draw down (the technical term for reduction), six inches of the end of a square or rectangular bar of iron or steel; the smith will place the bar across the anvil with perhaps four inches overhanging, and not resting quite flat, but tilted up about a quarter or half an inch at the near side of the anvil, as in Fig. 44, but less in degree, and the hammer will be made to fall as there shown, except that it will be at a very small angle with the anvil. Having given one blow, he will as the only change, twist the work a quarter turn, and strike it again; then he will draw the bar half an inch or an inch towards him, and give it two more similar blows, and so on until he arrives at the extreme end, when he will recommence; but this will be done almost in the time of reading these w'ords. The descent of the hammer, the drawing the work towards himself (whence perhaps the term), and the quarter turn backwards and forwards, all go on simultaneously and with some expedition. At other times the work is drawn down over the beak iron, in which case the curvature of this part of the anvil makes it less material at what angle the work is held or the blows given, provided the two positions be alike. In smoothing off the work, the position of Fig. 43 is assumed; the work is laid flat upon the anvil, and the hammer is made to fall as nearly as possible horizontally; a series of blows are given all along the work between every quarter turn, the hammer being directed upon one spot, and the work drawn gradually be¬ neath it. The circumstances are exactly the same as regards the sledge¬ hammer, which is used up-hand for light work ; the right hand be¬ ing slid towards the head in the act of lifting the hammer from off the work, and slipped down again as the tool descends; and the conditions are scarcely altered when the smith swings the hammer about in a circle, the signal for which is “about sledge whereas when, in either case, the blows of the sledge hammer are to be dis¬ continued, the fireman taps the anvil with his hand-hammer, which is, I believe, an universal language. In drawing down the tang or taper-point of a tool, the extreme end of the iron or steel is placed a little beyond the edge of the anvil, as in Fig. 44 by which means the risk of indenting the anvil is entirely removed, and the small irregular piece in excess beyond the taper is not cut off until the tang is completed. Fig. 45 shows the position of the chisel in cutting off the finished ob¬ ject from the bar of which it formed a part; that is, the work is placed betwixt the edge of the anvil, and that of the chisel imme¬ diately above the same; the twq resemble in effect a pair of shears Sometimes the edge of the anvil alone is used for small objects, ORDINARY PRACTICE OF FORGING. 101 first to indent, and then to break off the work, but this is likely to injure the anvil, and is a bad practice. When it is required to make a set-off, it is done by placing the intended shoulder at the edge of the anvil: the blows of the ham¬ mer will b'e effective only where opposed to the anvil, but the re¬ mainder of the bar will retain its full size and sink down, as repre¬ sented in Fig. 46. Should it be necessary to make a shoulder on both sides, a flat-ended set hammer, struck by the sledge, is used for setting down the upper shoulder, as in Fig. 47, as the direct blows of the hammer could not be given with so much precision. In each of these cases some precaution must be observed, as other¬ wise the tools, although so much more blunt than the chisel, Fig. 45, will resemble it in effect, and cripple or weaken the work in the corner. On this account the smith’s tools are rarely quite sharp at the angles. This mischief is almost removed when the round fullers, Fig. 48, are used for reducing the principal bulk, and the sharper tools are only employed for trimming the angles with moderate blows. When the iron is to be set down, and also spread laterally, as in Fig. 49, it is first nicked with a round fuller as upon the dotted line at a, and the piece at the end is spread by the same tool, upon a Fig. 49. the short lines of the object, or parallel with the length of the bar. The first notch greatly assists in keeping a good shoulder at the bottom of the part set down, and the lines are supposed to repre¬ sent the rough indications of the round fuller before the work is trimmed up. There is often considerable choice of method in forging, and the skillful workman selects that method of proceeding which will pro¬ duce the result with the least portion of manual labor. Thus an ordinary screw-bolt, that I will suppose to measure five-eighths of an inch in diameter in the stem, and one inch square in the head, may be made in either of the three following ways adverted to in the outset: 102 THE PRACTICAL METAL-WORKER’S ASSISTANT. First, by drawing-down:—A bar of iron is selected one inch square, or of the size of the head of the bolt, and a short portion of the same is set down, according to Fig. 48, by a pair of fullers that are convex in profile as shown, and also slightly concave upon the line at right angles to the paper. This prepares the shoulder or joining of the two dimensions. The bolt is made cylindrical, and of proper diameter between the rounding tools, Fig. 50; and lastly, it is cut off with the chisel, as in Fig. 45, so much of the original square bar as suffices for the thickness of the head being allowed to remain. Secondly, by jumping:—A piece of bolt-iron of five-eighths of an inch in diameter, or of the size of the stem of the bolt, is cut off somewhat longer than the intended length: “a short heat" is taken upon it, that is, the extreme end alone is made white-hot, then placed perpendicularly upon the anvil, and the cold end is struck with the hammer as in driving in a nail. This thickens the metal or upsets it, and makes a thick conical button. The head is completed by driving the bolt into a heading tool with a circular hole of five-eighths diameter. The thickened part of the head prevents the piece from passing through, and the lump is flattened out by the hammer into an irregular button or disk, which is afterwards beaten square to complete the bolt. Figs. 51, 52, and 58, explain these processes. The latter is a single tool, but the heading tool, Fig. 54, with several holes, is also used. Figs. 50 53 52 51 In upsetting the end of the work, if more convenient, it may be held horizontally across the anvil and struck on the heated ex j tremity with the hand hammer; or it can be jumped forcibly upon the anvil, when its own weight will supply the required momen¬ tum. If too considerable a portion of the work is heated, it will either bend, or it will swell generally; and therefore to limit the enlargement to the required spot, should the heat be too long, the neighboring part is partially cooled by immersing it in the water trough, as near to the heat as admissible. ORDINARY PRACTICE OF FORGING. 103 Thirdly, the same bolt may be made by building-up or welding: -—An eye is first made at the end of a small rod of square or flat iron ; by bending it round the beak iron, as in Fig. 55, it is placed around the rod of five-eighths round iron, and the curled end is cut off with the chisel, as in Fig. 56, enough iron being left in the ring, which is afterwards welded to the five-eighths inch rod to form the head of the bolt, by a few quick light blows given at the proper heat. The bolt is then completed by any of the tools already described that may be preferred. A swage at the angle of sixty degrees, Fig. 57, will be found very convenient in forming hex¬ agonal heads, as the horizontal blow of the hammer completes the equilateral triangle, and two positions operate on every side of the hexagon; Fig. 57 is essential likewise in forging triangular files and rods. Of these three modes of making a bolt, and which will apply to a multitude of objects somewhat analogous in form, the first is the most general for small and short bolts; the second for small but longer kinds; and the third is perhaps the most common for large bolts, although the least secure; it is used for bolts for ordinary building purposes, but is less generally employed for the parts of mechanism. For works of the same character, in which a considerable length of two different sections or magnitudes of iron are required, the method by drawing down from the large size would be too expen¬ sive ; the method by upsetting would be impracticable ; and there¬ fore a more judicious use is made of the iron store, and the object is made in two parts, of bars of the exact sections respectively. The larger bar is reduced to the size of the smaller, generally upon the beak iron with top fullers, and with a gradual transition or taper extending some few inches, as represented in Fig. 58; the two pieces are scarfed or prepared for welding, but which part of the subject is for the present deferred, in order that the different examples of welding may be given together. The Fig. 58 is also intended to explain two other proceedings very commonly required in forging. Bars are bent down at right angles as for the short end or corking of the piece, Fig. 58, by lay¬ ing the work on the anvil, and holding it down with the sledge¬ hammer, as in Fig. 59 ; the end is then bent with the hand-hammer, and trimmed square over the edge of the anvil; or when more pre¬ cision is wanted, the work is screwed fast in the tail-vice, which is one of the tools of every smith’s shop, and it is bent over the jaws of the vice. When the external angle, as well as the internal, is required to be sharp and square, the work is reduced with the fuller from a larger bar to the form of Fig. 60, to compensate for the great extension in length that occurs at the outer part, or heel of the bend, of which the inner angle forms as it were the centre. The holes in Fig. 58, for the cross bolts, are made with a rod- punch, which is driven a little more than half way through from the one side whilst the work lies upon the anvil, so that when 104 THE PRACTICAL METAL-WORKER’S ASSISTANT. turned over, the cooling effect of the punch may serve to show the place where the tool must be again applied for the completion of the hole; the little bit or burr is then driven out, either through the square hole, in the anvil that is intended for the bottom tools, or else upon the bolster, Fig. 61, a tool faced with steel, and having an aperture of the same form and dimensions as the face of the punch. Figs. 59 58 Fig. 64 shows the ordinary mode of making the square nuts for bolts. A flat bar is first nicked on the sides with the chisel, ihm punched, and the rough nuts if small, are separated and stiuig upon the end of the poker (a slight round rod bent up at the en 1), for the convenience of managingdhem in the fire, from which they are removed one at a time when hot, and finished on the triblet, Fig. 65, which serves both as a handle, and also as the means of perfecting the holes. For making hexagon nuts, the flat bar is nicked on both edges with a narrow round fuller; this gives a nearer approach to the hexagon: the nuts are then flattened on the face, punched, and dressed on the triblet within the angular swage, Fig. 57, before adverted to. Thick circular collars are made precisely in the same way, with the exception that they are finished externally with the hammer, or between top and bottom rounding tools of correspond¬ ing diameter. It is usual in punching holes through thick pieces, to throw a little coal-dust into the hole when it is partly made, to prevent the punch sticking in so fast as it otherwise would: the punch generally gets red-hot in the process, and requires to be immediately cooled on removal from the hole. In making a socket, or a very deep hole in the one end of a bar, ‘ome difficulty is experienced in getting the hole in the axis of the bar. and in avoiding to burst open the iron; such holes are pro¬ duced differently, by sinking the hole as a groove in the centre of a flat bar by means of a fuller; the piece is cut nearly through from the opposite side, folded together lengthways, and welded. The ORDINARY PRACTICE OF FORGING. 105 hole thus formed will only require to be perfected by the introduc¬ tion of an appropriate punch, and to be worked on the outside, with those tools required for dressing off its exterior surface, whilst the punch remains in the hole to prevent its sides from being squeezed in : this method is very good. For punching square holes, square punches and bolsters are used, and Fig. 62, the split bolster, is employed for cutting out long rectangular holes or mortises, which are often done at two or more cuts with an oblong punch. Mortises, when of still greater length, are usually made by punch¬ ing a hole of their full width at each end, and cutting out a strip of metal between them, by two long incisions made with the rod- chisel ; at other times one cut only is made, and the mortise is opened out ; this retains all the iron, but makes the ends narrower than the middle. In finishing a mortise, a parallel plate or drift is inserted in the slit; the drift is laid across the chaps of the vice, whilst the bar of iron lies partly between its jaws, in order that the blows of the hammer may be effective, on the upper and under surfaces of the one rib at the same time. The drift serves as a temporary anvil; the other rib is completed in the same manner, and the work is finally closed to its true width upon the anvil, the drift still lying in the mortise. When a thick lump is wanted at the end of a bar, it is often made by cutting the iron nearly through and doubling it backwards and forwards, as in Fig. 63; the whole is then welded into a solid mass as the preparatory step. Fig. 66. Fig. 67. A piece with three tails, such as Fig. 66, is made from a large square bar; an elliptical hole is first punched through the bar, and the remainder is split with a chisel, as in Fig. 67, the work at the time being laid upon a soft iron cutting plate in order to shield the chisel from being driven against the hardened steel face of the an¬ vil ; the end is afterwards opened into a fork, and moulded into shape over the beak-iron, as indicated by the dotted lines. The concave lines about the object are principally worked with the fuller, or half-round set-hammer; and in making all the holes, narrow oval punches are used as described at the commencement, and the slits are enlarged into circular holes by conical mandrels ; these bulge the metal out, and the holes are more judiciously formed in this manner than if the metal were wasted by cutting out great circular holes, which would sever a large quantity of the fibres and reduce the strength 106 THE PRACTICAL METAL WORKER’S ASSISTANT. The mandrels are left in the holes whilst the parts around them are finished, which tends to the perfection of both parts; as the holes more closely copy the mandrels, and the marginal parts are better finished when the apertures are for the time rendered solid. Supposing a hole to be wanted in the cylindrical part of the work that should be finished between the rounding tools, the mandrel could not be allowed to remain in; and therefore a short piece of iron is forged or drawn down to the size of the hole, cut oft" in length to the diameter of the part, and inserted in the hole to preserve it from being compressed, yet without interference with the completion of the cylindrical portion; which accomplished, this little bit, called by the un-mechanical name of a devil, is driven out, unless by a very careless use of the welding temperature it should have been permanently fastened in. Towards the conclusion a long mandrel is passed through the two holes in the fork of Fig. 66, to show whether their common axis is at right angles to the main rod, otherwise the one or other arm is drawn out, or upset, accord¬ ing as the work may err in respect to deficiency or excess of length. Such a piece as Fig. 66, if of large dimensions, would be made in two separate parts, and welded through the central line or axis. Should it happen the two arms are not quite parallel, that is, when viewed edgeways should they stand oblique to each other, or to the central bar, an error that could scarcely be corrected by the hammer alone; the work would be fixed in the vice with the two tails upwards, and the one or other of these would be twisted to its true position by a hook wrench or set, made like the three sides of a square, but the one very long to serve as a lever; it is applied exactly in the manner of a key, spanner, or screw wrench, in turn¬ ing round a bolt or screw. The hook wrench is constantly used for taking the twist out of work, or the error of winding, as the hammer can only be successfully employed for correcting the cur¬ vatures of length. Some bent objects, such as cranks and straps, are made from bar- iron, bent over specific moulds, which are sometimes made in pairs like dies, and pressed together by screw contrivances. When the moulds are single, the work is often retained in contact with the same, at some appropriate part, by means of straps and wedges; whilst the work is bent to the form of the mould by top tools of suitable kinds. Objects of more nearly rectilinear form are cut out of large plates and bars of iron with chisels ; for example, the cranks of locomotive engines are faggoted up of several bars or uses laid together, and pared to the shape; they are sometimes forged in two separate parts, and welded between the cranks, at other times they are forged out of one parallel mass, and afterwards twisted with a hook-wrench, in the neck between the cranks, to place the latter at right angles. The notches are sometimes cut out on the anvil whilst the work is red-hot; or otherwise bv machinery when in the cold state. ON WROUGHT-IRON IN LARGE MASSES. 107 A very different method of making rectangular cranks and similar works is also recommended, by bending one or more straight bars of iron to the form, the angles, which are at first rounded, are perfected by welding on outer caps. In this case the fibre runs round the figure, whereas when the gap is cut out, a large propor¬ tion of the fibres are cut into short lengths, and therefore a greater bulk must be allowed for equal strength: this method is however seldom used. All kinds of levers, arms, brackets and frames, are made after these several methods, partly by bending and welding, and partly by cutting and punching out; and few branches of industry pre¬ sent a greater variety in the choice of methods, and which call the judgment of the smith continually into requisition. CHAPTER VII. ON WROUGHT-IRON IN LARGE MASSES. The manufacture of wrought-iron in large masses cannot boast of a very early origin. Although we read in the most ancient of Books that Tubal Cain, before the Flood, was an instructor of every artificer in brass and iron, it would doubtless have puzzled even that great founder of the iron trade, had he been furnished with an order to make the large masses of wrought-iron required for a “Niagara,” “New Ironsides,” “Roanoke,” or “Great Eastern” steam-ship; and he would have been equally at a loss with many modern craftsmen, had he been requested to forge a monster gun or a double-throw crank-shaft for engines of 1000 horse-power. Were he again permitted to visit the world, the mighty machinery at work on every hand would compel the admission that his trade had made great strides during his absence. These advances in the manufacture of wrought-iron in large masses have taken place almost entirely within the present century, if not, indeed, within the last thirty years. Up to that period, the improvements upon Tubal Cain’s (we presume original) inventions were of so limited a nature, that, in the year 1820, the manufacture of a shaft—say of about 6 inches diameter, and weighing 15 or 20 cwt.—required the concentrated exertions of a large establishment, and was considered a vast triumph if successfully accomplished; whereas we are now accustomed to forgings of 20 and 30 tons’ weight, as matters of every-day occurrence, scarcely exciting the slightest notice. Nor do we stop even here: much larger masses will no doubt, ere long, be manufactured for the construction of iron ships, which in future years, owing to the increased size and strength of the plates, will be built upon a scale that would but recently have been deemed 108 THE PRACTICAL METAL-WORKER’S ASSISTANT, fabulous. This consideration, combined with the requirements of rapid communication, which demand more colossal engines, call for renewed energy in conducting this important manufacture. It may, perhaps, not be out of place to mention here, as a fact having few parallels in other branches of the industrial arts, that, almost without exception, all the improvements that have latterly crowded upon each other in this trade have originated with the ‘•hammermen” or workmen themselves, and have been worked without even the protection of an exclusive patent-right. Our subject naturally divides itself into two chief heads, viz., the materials of which forgings are made, and the tools with which the manu¬ facture is accomplished. We purpose treating of the latter first. Description of Forge-tools. —A forge has necessarily three principal divisions, viz., the furnace, the crane, and the hammer; and they compose the chief fixtures. The furnace (Fig. 68) is, in this country, of the ordinary reverberat¬ ing description, strongly bound together with plates and binders of iron, of a proportionate size to the description of work intended to be per¬ formed. A very great deal more depends upon the furnace than might be supposed by those who are not thoroughly conversant with the practical working of one. Variations in the slightest detail in their construction or working are followed by such great differences in the results, that even a good and experienced fur- naceman, if set to manage a strange Fig. ea. ON WROUGHT-IRON IN LARGE MASSES. 109 furnace, will find some difficulty until lie has made himself thoroughly acquainted with its peculiarities. The selection of a proper description of fire-brick with which to construct the furnace is a matter of considerable importance. With¬ out attempting to enter into the merits of different fire-bricks, w*e would observe that the question of expense is infinitesimal when compared with the consequences of using cheap and inferior bricks, which would be costly at the lowest price, from the great wear and tear upon them, and from the annoyance and loss caused by the often-repeated stoppages for repairs. It is, therefore, the wisest and best economy always to use the very best fire-bricks that money can procure. In some cases where large work is intended to be made, a furnace, with a grate at each end, and having the stack or chimney in the centre, has been tried; but, as it has not been generally introduced, we presume it possesses few, if any, ad¬ vantages over the ordinary furnace. In fact, for the largest forg¬ ings that have ever been made, furnaces with single grates have proved successful, where double-grated furnaces have failed. The sketch we have given in Fig. 68 is a furnace such as is gener¬ ally used, and which is found very effective for the purposes required. With anthracite coal, furnaces with closed ash-pits, and blown with a fan, are used, and which answer very well. Mr. Mallet, in his work on the “Construction of Artillery,” page 114, states, that “at length the limit is found when with our present known modes of working wrought-iron (even with the heaviest and best appliances) we can no longer add to its size. The limit is reached by the failure of power to heat the mass, or the required part of it, to the welding heat. The time required for the piece to remain in the furnace to effect this, continually in¬ creases as its bulk grows, and with it the sources through which heat is lost and dissipated; but a certain proportion of iron is burned away, or melted from the surface at the part requiring to be brought to welding, as equals the weight of the 'slab’ or mass laid on, and the labor is then in vain: the work, like that of the embroidery of Penelope, becomes an endless task, and the limit has been reached beyond which the piece can be forged no bigger. The point at which this limit is reached can be stretched a good deal by the extreme skill of the operative forge man, and the skil¬ ful construction of his furnace; but, however great these may be, the limit is at length reached by all; and, with our existing tools, in Great Britain is probably reached in every case at a diameter (of a cylindrical mass) of about four feet, and about twenty feet in length.” There is considerable truth and force in these observations as applied to existing machinery: but the paragraph seems to con¬ vey the impression that we are not expected to exceed the limits laid down by Mr. Mallet. We should be sorry to indorse this opinion, or to believe that we have even approached the maxi- 110 THE PRACTICAL METAL-WORKER’S ASSISTANT. mum size in our forgings, having so frequently and so recently seen that which is in one year deemed impracticable in the manu¬ facture of forgings, accomplished with the utmost ease in the suc¬ ceeding one; while the necessary requirements of that year are again followed by still further improvements, even where inven¬ tion and mechanical skill had apparently reached their highest development. And so it will continue to the end of the chapter. We might as well attempt to obstruct the progress of the engi¬ neer, and say to him, " Thus far canst thou go, but no farther ” a-s attempt to limit the sizes to which forgings may be made in future years. If larger forgings are required, and money is forthcoming to pay the cost of their manufacture, the work will not stand still for the want of workmen to undertake it, or machinery wherewith to handle it, however large it may be. The only real obstacle to the production of forgings of larger size is the cost; the bugbear set up in the above extract, that more iron is wasted than is added, being but another mode of accounting for inexperience and bad workmanship. Crane. —The crane is a very useful auxiliary in the working of the forge. Without its aid it would be impossible to fabricate those large masses of iron, the almost daily manufacture of which has ceased to excite surprise at their magnitude. The crane (Fig. 69), as is well known, is composed, first of a strong upright, either in¬ dependently fixed in a solid foundation in the ground, or dependent on the walls or roof of a building; next, of the top pieces, called “ cheeks,” and the “ stays,” to which is attached a winch of ordinary construction; and a strong pair of blocks, with a chain lead¬ ing to the winch. It is necessary that the blocks should be capable of working backward and forward on the cheeks, which is technically called ‘‘ racking out,” or "in,” from the fact that a rack and pinion-wheel are generally employed to effect the object. The crane must also be so placed that the centre is exactly equidistant from the centre of the furnace-door and the centre of the anvil, its use being to swing "the piece” from the furnace to the anvil, and vice versa. Cranes have generally been made of wood, although very few sorts of wood are capable of resisting the great heat to which cranes for forging are subjected. Others, however, have lately ON WROUGHT-IRON IN LARGE MASSES. Ill been made of iron, or of a mixture of iron and wood. Cast-iron, being comparatively brittle, is decidedly objectionable and unsafe, in consequence of the great weight they have to bear, and the ex¬ cessive jar of the forge-hammer. There is less objection to wrought- iron, which, if rightly proportioned, is we believe the best material v . 7n for the purpose. Hammers. —We now come to what is, perhaps, the most important, or, at any rate, what is con¬ sidered the most im¬ portant tool in the forge, viz., the hammer; and we purpose giving a slight description of the various sorts in use at the present time, including the beauti¬ ful direct-acting tool known as the Nasmyth or steam-hammer. We are unable, in the limits of this work, to consider the merits, or give any description of the various improvements that have been attempted on the original steam-hammer; some of them being confined to matters of detail, while others introduce defects so palpable, that we gladly return to the original Nasmyth. The most ancient form of forge-hammer was probably that technically called the “ tennant-helve,” Fig. 70, known in France as the “ Marteau frontal,” from its being lifted at the front end. This hammer is a heavy mass of cast-iron, which was lifted by project¬ ing arms, fixed in a ring of iron, called the “cam-ring,” falling through a certain space by its own gravity. The pivots behind, on which it rested, were of a Fig< 7 ^ curved form, to allow its being easily worked. This was, and still is in many works, a very effective tool, performing its work with regularity, and seldom get- ing out of order. The “ tennant-helves ” being found inconvenient for certain de¬ scriptions of work, the “ tilt-hammer,” Fig. 71, was introduced. In¬ stead of being raised at the front end, this hammer is depressed by a similar “ cam-ring” from a part projecting behind. It is composed Fig. 72. Another improvement on of wood and iron, the shank being of good tough oak, wedged into a ring in which it works; the hammer-head being also wedged on to the shank. The shank is surmounted by a beam of wood, which, acting as a powerful spring, gives greater force and rapidity to the blow. This form of hammer was peculiarly adapted to the “ tilting” of the different sorts of steel, the original “tennant-helve,” was to 112 THE PRACTICAL METAL-WORKER’S ASSISTANT. lift the helve between the head of the hammer and the pivots on which it worked (Fig. 72), an advantage being thus given to the hammerman, which the tilt also possesses, by enabling him to go all round the end of his hammer. But the last and greatest im¬ provement was that known to the trade as the “ belly-helve,” Fig. 73; a not verv euphonious name, but one which indicates the nature of the tool. It was lifted, as its name indicates, under the bottom part of the helve, by means of a “ bray,” which could be length¬ ened or shortened ac¬ cording to the size of the “ piece” to be acted upon. With some of the largest size a very effectual blow is struck with a piece of iron of from 3 feet to 4 feet in diameter—the “helve” being raised, and the “bray” being lengthened in proportion. This hammer also permits the hammer¬ man to go completely round his hammer, to inspect the work under operation. For plain ordinary work it is not surpassed in efficiency, even by the direct-acting steam-hammer. It is of very great im¬ portance that the foundation be perfectly firm, and capable of re¬ sisting the force of the blows to which it is subjected. The most usual way of securing this end, is by placing under the anvil-block Fig. 74 . —which of itself is a very massive cast¬ ing, weighing, with the cup upon which it rests, from twelve to fifteen tons — a considerable mass of timber, carefully placed and fitted cross-wise. This foundation must be strongly secured, for unless the anvil- block is very firm, a considerable por¬ tion of the blow will be dissipated, and its value lost. We come, lastly, to Nasmyth’s steam- hammer, Fig. 74, a * tool which has de¬ servedly come into very general use. Although many of the very largest forgings have been made by the old-fashioned helves, especially the “belly-helve” above described; nevertheless, the in- ON WROUGHT-IRON IN LARGE MASSES. 113 vention lias been of immense importance, not only to the forge- masters, but in many other branches of manufacture. The steam- hammer, like other great inventions, has its faults as well as its merits. The first great; merit of the steam-hammer is, that it is a simple direct-acting machine, dispensing with much of the cum¬ brous wheel-work required with the old helves. It takes up little room, and requires no “ gagger,” as the attendant workman is called, who attends to the hammer. The presence of the “ gagger” we object to, not so much on account of the expense, which is partly counterbalanced, in the case of the steam-hammer, by the necessity of employing an engineer; but on account of the almost insufferable torture from heat which the “ gagger” has to endure: for if the “gag” is not inserted and the hammer stopped at the critical moment, a valuable piece of work may be damaged. Another of the excellences of the steam-hammer is, that the blow can be varied according to the size of the “ piece” under operation, and the force of the blow required. This is not, practically, such a great advantage as might at first appear; but in small works it is of considerable importance. We would, however, ourselves rather see the different sizes and classes of work effected under different sized hammers—with hammers perfectly proportioned to each description of work. Excepting in very large establishments, however, where there are a considerable number of hammers em¬ ployed, this cannot always be accomplished. The consequence is that the hammer is used more as a squeezer, frequently crushing the iron at the heart instead of drawing it in a sound manner under a hammer proportioned to its size. Where the works, therefore, are not extensive, or where the number of hammers is limited, the facility of regulating the stroke by the steam-hammer is an im¬ portant advantage in many descriptions of work. Another advan¬ tage is, that the hammer is always working parallel with the “piece” under operation, which is not the case with the old-fashioned helves, in using which the hammerman has to resort to many ingenious plans, such as employing thickness pieces, for overcoming this difficulty. The hammerman is saved a great deal of trouble in regulating his tools' by using the steam-hammer. With the old-fashioned helve, almost every different heat requires an alteration of the tools employed; with the steam-hammer there is no necessity for any such change. This of itself is a considerable advantage. With the Nasmyth hammer he is also enabled to work on each side of the hammer, as it can be placed in such a position as to be accessible on both sides. There are, however, a few defects even in this beautiful tool; and the first which presents itself to our mind is, that the same quantity of steam is consumed in striking a blow of one foot upon a piece, say of three feet diameter, as is required for a blow of three feet upon a piece one foot diameter; for, the stroke of the hammer being fixed, the cylinder takes the same quantity of steam in lifting the 8 114 THE PRACTICAL METAL-WORKER’S ASSISTANT. hammer the last foot as it does in lifting it the whole of the stroke. This might, no doubt, be remedied by some arrangement for raising or lowering the cylinder according to the height of the “ piece” upon which the blow is to be struck, which would be somewhat similar to the arrangement in operating with the belly-helve, already described. Another defect, but one which attempts have been made to remedy in some modifications of the steam-hammer, arises from the difficulty of swinging the “ piece” to be .operated upon, from the furnace to the hammer, one of the legs of the hammer being sometimes in the way. This difficulty might be overcome by allowing the hammer to stand upon one strong leg, which would in many cases be a considerable improvement. We have, also, a great objection to the amount of gearing connected with the work¬ ing of the valves. They are certainly very beautiful, and of most ingenious construction: but in all forging tools it is desirable that the greatest simplicity, combined with the greatest strength, should always be the first consideration. Arrangements have lately been made, we believe, for dispensing with these valves, and introducing in their place a simple balance-valve capable of being worked with great ease, and not so liable to get out of order. We have thus given some slight description of the different hammers employed in a forge. It has not been our intention to enter into very minute details upon this subject, nor to advance any very decided opinion as to the relative merits of the different imple¬ ments ; for we are aware that opinions greatly differ upon these points. The improvements that have taken place in this descrip¬ tion of tools during the last fifteen years have been very great; but we are prepared to witness still greater developments of me¬ chanical application in connection with this branch of the art. Materials.— We now propose to give a short description of the materials consumed in the forge, the chief of which are the coals and the iron. It is of considerable importance that care should be used in the selection of the fuel for the manufacture of forgings, as great difference exists in this important mineral, some being very much more suitable for the manufacture than others. The best bituminous for the purpose is a strong, dense, durable coal, possess¬ ing a good body, and having a dull, dirty appearance. Coal of this kind with a bright clean look, easily broken, as a general rule is not suitable. Of course it is desirable that the coal should be as free from sulphur as possible, and that it should not contain any large proportion of those foreign matters which, having an affinity for iron, fuse on the bars in the shape of clinkers. We now come to the consideration of the best description of iron for this manufacture. Scrap-iron is that most generally used; but, far from agreeing with the generally received opinion that it is the best, we think that it is the very w'orst description of iron for the purpose; and for more reasons than one. Engineers usually re¬ quire, in their contracts with the forge-master, that their forgings shall be made from the best scrap-iron; and it is, of course, the ON WROUGHT-IRON IN LARGE MASSES. 115 duty of the forge-master to comply with the terms of his instruc¬ tions and contract. Let us first endeavor to see how this almost universal belief in the superiority of scrap-iron has arisen. At the time when small forgings were first attempted to be made as an article of commerce, the manufacture of iron was in such an im¬ perfect state, and the quality so indifferent, that large quantities of the best iron had to be imported from Sweden and Eussia, and for a long time the strap-iron was of a quality that could not be approached by our own iron of that period. Since that time, the use of Eussian and Swedish iron has been almost entirely discontinued, except for the manufacture of steel; the greater part of the scrap-iron now pro¬ duced, therefore, is of a very different quality to that formerly known as best scrap-iron. This material was deservedly considered the most proper material for the manufacture of forgings that could then be procured; but it must be borne in mind that, at the date we speak of, the forgings were so limited in size that the practical evils result¬ ing from the use of scrap-iron, which we are about to explain, were not so perceptible. In the ordinary manufacture of bar-iron it is the practice, in most works, in order to obtain it of the toughest and best description, to work and re-work it several times over. The number of workings the iron undergoes is marked by the number of “ best” stamps that it bears, as “ best, best best,” “ treble best,” etc., each “ best” indicat¬ ing a better quality, an extra working, and with a correspondingly higher price. But this progressive improvement has its limits, as will be perceived, from a series of experiments which were insti¬ tuted by the writer with the object of testing the correctness and limits of this improvement. Taking a quantity of ordinary fibrous puddled-iron, and reserv¬ ing samples marked No. 1, we piled a portion five feet high, heated and rolled the remainder into two bars marked No. 2; again re¬ serving two samples from the centre of these bars, the remainder were piled as before, and so continued until a portion of the iron had undergone twelve workings. The following table shows tho tensible strain which each number bore: No. 1 puddled bar 43,904 lbs. U U 2 re-heated . . 52,864 3 ‘ 59,585 “ 59,585 “ 57,344 “ 61,824 “ 59,585 “ 57,344 “ 57,344 “ 54,104 “ 51,968 '• 43,904 “ It will thus be seen that the quality of the iron regularly m- “ 4 rt 5 “ 6 “ 7 “ 8 “ 9 “ 10 “ 11 “ 12 116 THE PRACTICAL METAL-WORKER’S ASSISTANT. creased up to No. 6 (tlie slight difference of No. 5 may perhaps he attributed to the sample being slightly defective); and that from No. 6 the descent was in a similar ratio to the previous increase. From these experiments it appears that scrap-iron, or any other iron, highly refined, is the very worst material for the construction of large forgings which can be used; and that if we take, in the first instance, a strong fibrous fresh-puddled iron, the ordinary workings required in the process of forging will be sufficient to improve it to the average maximum of strength required ; whereas highly refined iron, such as Lowmoor or Bowling, although the very best description for many purposes, has already reached the highest point in its strength, from which it is more likely to be deteriorated by additional workings. It may then be asked—how can we hope, with any degree of success, to manufacture large forgings, which require to be worked over perhaps a score of times, each working beyond a given num¬ ber tending to vitiate the iron ? We can conceive that this deteri¬ oration does not penetrate the iron to any great depth; that few forgings are heated more than six times in one place before fresh iron is added; and that the various layers thus successively added to the rpass protect the under portion from the deteriorating in¬ fluences of the successive heatings. It is also to be observed that any crystallization which might take place, commences from the outside of the mass; and as this is the portion which is most immediately acted upon by the blows of the hammer, the fibre is elongated in a greater degree, and thus restored to its original quality. As a proof of this, we may instance the manufacture of the monster gun, which was built up in seven distinct layers, the forging of which took seven weeks. At the meeting of the British Association at Glasgow, in Sep¬ tember, 1855, a question was raised in the mechanical section as to the causes of the deterioratiou of the metal of which the artil¬ lery of the present day was constructed. On this question a long and interesting discussion ensued, both in reference to the compara¬ tive weakness of cast-iron as now produced, and the adaptation of forged and malleable iron as being stronger and better adapted for this purpose. The accounts received from the Baltic and Black Seas of the bursting of guns' and mortars of recent construction, indicated that something was wrong. These failures gave rise to conjectures on the part of the Government as well as of the public ; and, in order to trace the cause of this apparent weakness to its source, an inquiry was institued by the authorities at Woolwich; and subsequently the Association appointed a Committee to co¬ operate with the Government in the investigation of this very im¬ portant question. In order that no time might be lost, the secre¬ tary of the section was directed to issue circulars to engineers, iron¬ masters, and manufacturers, requesting that they would forward to the members of the Committee such opinions and observations as ON WROUGHT-IRON IN LARGE MASSES. 117 they deemed advisable, in regard to the material itself, and to its treatment preparatory to the manufacture of ordnance.” It is to be regretted that these circulars were not made more general, and that more of them were not addressed to practical forge-masters; for we observe, among the replies elicited, the name of one man only practically and intimately connected with the manufacture of large masses of wrought-iron ; and his reply is the only one indicating any hope of success in the application of wrought-iron for ordnance purposes. All the other writers who no¬ ticed wrought-iron at all (for many passed it by without the slightest attention) most unequivocally condemned it, and came to the con¬ clusion, that “ the tendency to crystallization which the long-con¬ tinued heating produces is such, that powerful ordnance cannot be manufactured advantageously from malleable iron.” It was, perhaps, fortunate that the manufacturers of the monster gun were not aware of the adverse opinions thus pronounced against wrought-iron for ordnance; otherwise, they might have been discouraged in their attempt, aud what must now be consid¬ ered the successful manufacture of large wrought-iron ordnance might have been postponed. The following table of the tensile strength of the iron before it entered into the composition of the gun; of the iron cut from it, and as it now is in the gun, both transverse and longitudinal to the grain; and of the borings from the gun, worked over again in different ways,—tend to show that, so far from deterioration or crystallization having taken place, the metal was improved by its long-continued heating and working: Breaking Sample bars Experiment Description of Iron. strain in lbs. Aver- 4 ins. long per sq. in. age. elongated. No. 1. Original iron of which the gun was made 4S*384 . ^ in. No. 2. Ditto ditto 50624 40504 h in. No. 3. Cut across the grain from muzzle of gun 41*644 •• § in. No. 4. Ditto ditto 43*904 .. f in. No. 5. Ditto ditto 50*624 43*390 £ in. No. 6. Cut with the grain from muzzle of gun 48*384 .. | in. No. 7. Ditto ditto 50*624 .. § in. No. 8. Ditto ditto 62*864 50*624 £ in. No. 9. Borings from gun worked over with coal 60*584 .. \ in. No. 10. Ditto ditto 62*824 61*704 ^ in. No. 11. Borings from gun worked over with cliarcl. 76*584 76*584 ^ in. No. 12. Swedish iron as imported, | sq. . 60*564 60*584 \ in. From the above experiments it will be seen that the original iron put into the gun was of no extraordinary strength, which is accounted for by the fact that it was designedly selected, in conse¬ quence of the experiments already quoted, from what is commonly known as “ No. 2 iron,” or iron once worked over from the pud¬ dling-process, though of considerable strength and body, and com¬ mercially called “ common iron.” This iron, after seven weeks heating and shaping into a gun, was, as we have already stated, so far from being deteriorated by this “ long exposure to great heat,” as to be actually improved in quality; for we find that the aver¬ age of the trials gives an increase of tensile strength from 49'504 118 THE PRACTICAL METAL-WORKER’S ASSISTANT. lbs. per square inch to 50-624 lbs., both trials being longitudinal with the fibre or grain of the iron. The strength of the iron across the grain can hardly be regarded as of much importance, although it exhibits a remarkable amount of cohesion, for it was laid in the direction of the strain, and there¬ fore the cut transverse to the grain might have been expected to possess less cohesion in that direction than if the grain had been placed in its position accidentally. If we follow this question further, and examine the result of working over again the borings from this forging, we find that the tensile strength is increased from 49*504 lbs. per square inch to 61-704 lbs. when treated with coke, and 76’584 lbs. when worked with charcoal; and we think with results such as these—without parallel in any English make of iron, even under the most favor¬ able circumstances—we may be allowed to assert that the myth commonly called “ crystallization from long exposure to great heats,” does not apply to the fabrication of this the largest forging ever made. We have given these details to illustrate and enforce the preference given to puddled-iron over scrap-iron; but there is another very important reason why scrap-iron should not be used for the manufacture of forgings—scrap-iron is composed of many various qualities of. iron, and all of them have their own special welding points. When worked together, one portion that is less refined is too much heated, and consequently deteriorated, before the more highly refined portions are at a welding heat; and we are thus placed in the awkward dilemma of either burning the one, or of being unable to weld the other. It may be said that this objection is a mere theoretical one, and that, practically, no such difficulty exists. This, however, is not the case, for the dif¬ ference of temperature at which puddled-iron and a highly-refined iron weld is very considerable; although, from the difficulty of finding a really good pyrometer for these extreme heats, we are unable to give exact data in degrees. If any proof were required of this, which is a matter of every-day economy, it is only neces¬ sary to inquire into the heating of iron for our rolling-mills. It is a well-established fact, that, in the mixing of different descrip¬ tions of iron in the piles for that purpose, the hardest and most refined iron is always placed outside, and the puddled or common iron inside. Were a contrary practice pursued, and puddled-iron oi ordinary quality placed at the outside, and the highly-refined or scrap placed in the centre of the pile, the outer or puddled-iron would be wasted and destroyed before the inner portion was suffi¬ ciently hot to weld. We may also call attention to the various qualities found among scrap-iron, some being what are termed “hot-short,” and others “cold-short.” We have before quoted a writer on the subject of the manufacture of wrought-iron for ordnance, who has stated that the limit has been reached beyond which forgings cannot be made ; assigning reasons for those limits according to his own ideas and ON WROUGHT-IRON IN LARGE MASSES. 119 experience, tlie principal one being the assumed difficulty of heat¬ ing such large masses. Now, if we take strong puddled-iron in place of the “ scrap,” which has hitherto been the material generally used, we effect, as we have shown, a saving of say about 20 per cent, in the heat required to unite soundly the various slabs or por¬ tions of which the “ piece” is composed; in other words, by this simple substitution of the material used, we increase, to the extent of about 20 per cent., the suppositious limits of the writer from whom we have quoted, but the accuracy of whose conclusions we challenge. Manufacture. —But scrap-iron, though, as we have endeavored to show, the worst for our purpose, is the material from which forgings are generally made; and we must say a word or two as to its preparation. It is necessary, in the first place, that the small pieces of scrap-iron should undergo a cleaning process. For this purpose, they are generally placed in a large drum or vessel, which is caused to rotate at a considerable velocity by machinery; and they are thus, to a certain extent, freed from oxide and various other superficial impurities, that would otherwise injure the material for forging purposes. In some works, where large quantities of scrap-iron are consumed for this and other purposes, the scrap is usually carefully selected; and none but blue and clean iron, pure as when it came from the manufacturer’s hands, is permitted to be used for forgings, the rusty and dirty iron being set aside for con¬ version to more common purposes, such as the manufacture of “bar-iron,” “grate-bars,” etc. The scrap-iron, having been thus cleaned or selected, is divided into lumps or masses of various descriptions, by being piled in quantities generally varying from 100 to 200 lbs. in weight on a slate or tile. These piles are charged into a reverberating furnace, commonly called a “heating” or “balling” furnace. After re¬ maining about one hour and a quarter, they are sufficiently heated to be forged out into slabs or “ blooms.” The piling of the iron is an operation requiring considerable skill and experience, for if the pile is not solidly put together, it will fall down in the furnace, and perhaps become attached to others. About ten to eighteen of these piles, according to their size, constitute a charge or “ heat;” and a good workman will turn out six charges per day, or about 3 tons 10 cwt. to 4 tons. Larger descriptions of slabs are used for many purposes; and several of those described are again piled together, subjected to the heating process, and hammered to the required shape. In some forges the same workman “shingles” or hammers his iron from the scrap-pile, and heats it in the same furnace in which he heats his forgings; but this is by no means a judicious arrangement. It is much better, especially with large work, that there should be a division of these operations, and that a certain number of men, of inferior skill, and consequently of less value, should heat and “ shingle” the iron for the first processes, and de¬ liver it to the more highly-paid and skillful hammerman in a further 120 THE PRACTICAL METAL-WORKER’S ASSISTANT. advanced and more convenient shape. There is another, and by no means inconsiderable advantage to be obtained by this arrange¬ ment. A much larger amount of work can be accomplished with the same number of men and tools, than in the case where the two classes of work are completed by one workman. These slabs vary in shape and size, according to the nature of the work for which they are intended; and are delivered to the hammerman accord- iugly. In large forgings, each particular piece requires different treat¬ ment, according to the shape and use for which it is intended. On this depends the question of the best manner of making it. For instance, a screw-shaft, which is subject to torsion, requires that the iron should be put together in a manner very different from the mode in which a crank or cross-head is prepared. We will take the case of shafts. The most ancient method of forging them was to take a certain number of slabs or plates of iron, made into a pile thus, (Fig. 75), and after heating them, to hammer them into Fig. 75. End View, Fig. 75. Front View. the round shape required. As it soon became necessary to make larger shafts, however, and as this pile could not conveniently be increased, an improvement was introduced, which consisted in taking a pile of slabs as before, and drawing a portion only of the mass into the shape required (see Fig. 7 6), leaving a lump on the end on which to place more slabs as needed; then drawing a little more at A to the required shape, adding more and more slabs as occasion required. This method is still practised at many works, and with considerable success; but it requires the utmost care and circumspection, both in regard to workmanship and materials. This is the method by which shafts are generally made in the north of England and Scotland, and in America. Fig. 76. Front View. Another plan is to lay up a faggot of square bars sufficient to make the required shaft (Fig. 77). This is a considerable improve¬ ment upon the slab-plan, there being much less risk of false weld- ON WROUGHT-IRON IN LARGE MASSES. 121 ings and careless workmanship ; and for this reason, when slabs are used, if the heat has not been sufficient to give a perfect weld to the iron, or if any oxide or dirt should intrude, the flaw or de¬ fect would run more across the shaft than in the faggot, where indeed any flaw from such causes would run longitudinally with the shaft, and consequently would not interfere in any thing like the same degree with its strength. But this method also requires great care and attention; for if the faggot of square bars be made too large at one heat, the interior of the mass cannot be sufficiently Fig. 77. Front view. - — L ^ ^ ^ / ' " — - ~ - --_ _ ^ *->» -- ■ " —•■ _ - ^ heated to allow of the iron being welded at the centre. I have Fig. 77. End view. Fig. 78. End view. often seen a broken steamboat shaft which has never been united at all at the heart, the bars from which it was made being in the same shape and state as when they were placed in the faggot. To avoid this great evil it is necessary to be especially careful not to pack faggots too large at once, but to make, in the first instance, a moderate-sized one, which, after being worked perfectly sound, has another layer of bars packed round it, and so on with further layer*, until the necessary size is attained with perfect soundness. Thus Fig. 78, A being the original faggot after it has been made sound and solid, has the bars, as shown, packed round it; it is then again heated and hammered into the required shape. The third method of manufacturing large shafts is commenced 122 THE PRACTICAL METAL-WORKER’S ASSISTANT. by making a round core or heart, B, and taking bars of a V form to pack round it (Fig. 79). This is a method of forging railway Fig. 79 . r n d view. ax ^ es which is frequently adopted. It was also the method adopted, with some variations, in forging the monster gun at the Mersey Iron Works. In a previous page we have given the tensile strength of the iron before it was forged into the gun, and its condition after undergoing that process; and it may be satisfactory if we give some details of the manner in which this large forging was worked. We have already stated that it was built up in seven distinct layers or slabs, and that the forging occupied seven weeks. Nor will this time seem unreasonable when its dimensions and weight are remembered. The chief points to be considered by the de¬ signer of the gun were, to obtain sound weldings; to place the iron, with its fibres, in the proper direction for resisting the most severe strains to which it could be exposed ; and to take care that, while working one part of the forging, other portions were not wasted under the action of the furnace by burning or crystalliza¬ tion. The first operation was to prepare a core of suitable dimen¬ sions, and nearly the whole length of the gun. This was done by taking a number of rolled bars, about six feet in length, welding them together, and drawing them out until the proper length was obtained. A series of V -shaped bars were now packed round the core, the whole mass heated in a reverberatory furnace, and forged under the largest belly-helve hammer. Another series of bars were now packed on, and the mass was heated again, and worked per¬ fectly sound. Another longitudinal series of bars were still re¬ quired over the whole length of the forging, which were added ; and the mass now presented a forging about fifteen feet in length and thirty-two inches in diameter, but requiring to be augmented to forty-four inches at the breach, tapering down to twenty-seven inches at the muzzle. This was accomplished by two layers of iron, placed in such a manner as to resemble hoops, laid at right angles to the axis of the mass; and, after two more heatings and careful welding, the forging of the gun was completed. After each important addition, a “ securing” heat was given to prevent flaws. It would be foreign to our purpose here to deal with this implement otherwise than as a mass of forged iron. Its di- ON WROUGHT IRON IN LARGE MASSES. 123 mensions, as given by Captain Yandaleur, in his report, are as follow: Ft. Ins. Length.15 10 Diameter at base.3 7| Diameter at muzzle.2 31- Diameter at trunnions.3 3| Length of bore.13 4 Diameter of bore.0 13'05 Its present weight is 21 tons 17 cwt. 1 qr. 14 lbs. The original weight, before boring, was 25 tons. The furnace employed was a reverberatory one; and the hammer, as we have seen, was the great belly-helve tilt-hammer, weighing 10 tons. As already inti¬ mated, the iron bored out of the gun was tough, sound, and per¬ fectly homogeneous, some of the borings being curled like a watch- spring seven times round ; and, when worked up again, it bore the test applied to prove its strength, as reported at page 117; and Messrs. .Horsfall have the satisfaction of having produced a forging which the scientific world had hitherto deemed impracticable. Shafts have sometimes been made after another method, which we consider very injudicious. Many specimens of this mode of manufacture have come under the notice of the writer in the shape of broken shafts, where the unsoundness, arising from the method of working adopted, has been so great as to make it a matter of surprise that the shaft had done any duty at all. The method in question was to forge four large square bars, proportioned, of course, to the size of the shaft required; packing them together (Fig. 80). This faggot was of such immense size, Fig. 80. Front view._ that the furnace and hammer employed were altogether insufficient to produce sound work. As a Fig. so. End view. Fig. si. necessary consequence, when the shafts so made were broken, the fracture had an appearance sim¬ ilar to Fig. 81, being only welded on the circumference; while the four fissures at the centre were sufficient, in many cases, to receive a man’s hand, while a rod of iron could be inserted from one end to the other. Crystallization.— A great deal has been said and written with reference to a supposed deterioration, or, as it has been called, ‘* crystallization” of iron, when rolled in large masses, from long- continued and frequent heatings. It has also been asserted that the 124 THE PRACTICAL METAL WORKER’S ASSISTANT. iron, while lying in the furnace, is continually attracting carbon from the grate, until, in course of time, it becomes carburetted,— that is, reconverted into pig-iron. When this theory was first pro¬ pounded, the writer determined to test its accuracy; and that in the presence of the gentlemen by whom it had been promulgated. A small knob, or corner, was accordingly detached from a large forging which had been over-heated or burnt. It broke off with a large flaky appearance very similar to some descriptions of lead ore. This was pronounced to be very similar in its nature to cast- iron, and in the so-called crystallized state. Proceeding to the smiths’ department, the iron was heated in the fire, and drawn down to about three times its original length. It worked well under the hammer; and when broken again in the usual way, was as beautifully fibrous as the iron from which it was originally made. This experiment led to the conclusion that the iron acted upon was very different in its nature from cast-iron, and certainly failed in sustaining the crystallization theory. It may be well, however, in the first place, to consider what is the meaning attached to this term “ crystallization.” It has been generally used to signify that the structure or composition of the iron has entirely changed its character and assumed a new form. Mr. Mallet, in page 110 of his work before quoted, thus describes this change: “With the same iron and the same volume of forging, however, the size of the crystals appears to be large and more developed in proportion to the time that the mass is maintained hot and in pro¬ cess of forging. This time is necessarily greater as the mass is so; and as the operation of reducing it to the required form is more complex or laborious. In fact, as in cast-iron, we saw that the crystals were larger the longer the mass required to cool; so in wrought-iron, they are larger the longer the mass is kept hot: and thus it happens that in very large and massive forgings, requiring often to be maintained perhaps for weeks, at temperatures varying from welding-heat down to dull redness, crystals are developed within the mass of a size tending materially to diminish, in some places, the average cohesion of the iron, where their planes of cleavage produce partial planes of weakness. The size of these crystals is occasionally surprising ; the broadest and flattest planes of cleavage frequently running in the direction in which surfaces of the integrant slabs, or portions of iron of which the mass has been formed, have been welded together. The author has observed crystals to deposit flat planes as large as the surface of a half-crown piece in forgings under seven tons weight.” We have little doubt that in many instances this statement is perfectly correct; we, however, at the same time declare our belief that cases are referred to where the greatest carelessness and inat¬ tention on the part of the workmen have been exhibited. We think, moreover, that some experiments which have taken place, and others which are still making, under the direction of Mr. Mallet, will ON WROUGHT IRON IN LARGE MASSES. 125 induce "him to alter his opinion on this point. To one of these we may here allude in support of this view: a sample bar has been planed out of the body of a large wrought-iron mortar piece made for him, and the sample shows a highly fibrous development, very different in appearance from the specimens described by Mr. Mallet in the above extract—a description, be it observed, which may be at any time observed in a forge on examining a piece of burnt iron or in an exposed corner which has been subjected to very great but not necessarily continued heat. It seems to us that all wrought-iron is, more or less, crystalline in its structure; and that the difference between what we call fibrous and crystallized iron only consists in the degree of fineness in the crystals, and perhaps in the manner in which they are laid together; the presence, also, of foreign matters, such as silicon, in some form, may also have its influence. Whatever the cause may be, however, it is known that a piece of good fibrous iron will break, under the smith’s hammer, with a long silky appearance; if suddenly fractured by an irresistible blow, the same piece of iron will break crystalline, but the crystals will be very fine and close, and of a good color. In some experiments made at Woolwich, in the year 1842, to test the effect of shot against wrought-iron plates, and determine whether wrought-iron was a suitable material for ships of war, it was found that the toughest and most fibrous plate-iron, when struck by shot, was instantaneously crystallized; while the pieces struck out were so hot, that the fragments, even after passing a considerable distance through the air, could not be handled with the naked hand; in many cases the fracture had that blue appear¬ ance, which is indicative of considerable heat. A 68-pounder wrought-iron gun burst with the first charge at Woolwich, on the 12th of July, 1855; on examination, the iron was pronounced to be crystallized, and its nature changed, by long exposure to great heat. This crystalline appearance was, most probably, the result of the very sudden disruption, as in the ex¬ periments with the iron plates; and, according to our view of the case, is traceable to bad workmanship. A considerable portion of the bars of which the forging was composed had never been welded at all; and no doubt the fracture commenced with these false weldings. The crystalline appearance, where the iron was torn from the solid mass, arose, at any rate, to a great extent, from the sudden fracture. Other causes, no doubt, assisted; among which the selection of iron too highly-refined may be included. From this crystalline ap¬ pearance, the authorities of the Ordnance Department arrived at the conclusion, that large masses of iron, from long-continued heat ing, have a tendency to crystallize, and lose the properties peculiar to wrought-iron. Acting on this hypothesis, they put a stop to what were called "Nasmyth’s experiments” at Patricroft, pro¬ nouncing the manufacture of a wrought-iron gun of large size im¬ possible—a theory which the successful manufacture of a much 126 THE PRACTICAL METAL-WORKER’S ASSISTANT. larger piece has since practically shown to be incorrect. As we have before shown, a bar of iron, planed transversely from a piece cut off the end of the gun, broke with a fibrous texture, and with a very slight tendency to crystallization; and that crystal by no means of a large character. This sample had never been treated or altered in the slightest degree since it was cut off the gun, and it would be pronounced " excellent best iron.” A portion of this was afterwards rolled down to three-eighths of an inch round bar-iron, and it was bent cold in all ways without giving way in the slightest degree. Having thus endeavored to explain the meaning of the term “ crystallization,” let us now endeavor to trace the causes which produce this result. The change in the structure of the mass of iron, when it occurs during the process of heating, is usually produced from the furnace being urged to a much greater heat than is necessary for welding the iron; in fact, the outside first, and, if the heat be not checked, the whole of the mass, is reduced to a pasty or partially fluid con¬ dition. The structure of the iron is thus entirely changed; and in the process of cooling the mass, crystallization takes place in the same manner as with other substances wffiich crystallize in passing from the fluid to the solid state. Under these circumstances, the iron may be injured—in other words, it may be burned: but we are not to suppose that such a result is either inevitable or by any means common; on the contrary, the heat necessary to produce the evil is with difficulty obtained in our ordinary furnaces, under the most favorable circumstances. Some years ago the experiment was tried at the Mersey Steel Works of fusing wrought-iron, with the idea of casting it into such shapes as “ cranks,” “ cross-heads,” and other forms required by engineers. They succeeded perfectly in obtaining excellent castings : but it was found that the deterioration of the structure of the iron in passing from the fluid to the solid state was such, that the work produced had little more strength than ordinary cast-iron. Of course, the manufacture was at once given up. But in the appear¬ ance of the fracture of the ingots resulting from Mr. Bessemer's experiments at Baxter-house, there was a great similarity between it and the results obtained in melting scrap wrought-iron. Mr. Mallet, in his work (Note R, page 251), says:—"Late ex¬ perience has shown me that in very large cylindrical masses of forged wrought-iron (i. e. of three feet diameter and upwards), amongst the other abnormal circumstances involved in their pro¬ duction, is that of their frequently rending or tearing internally in planes nearly parallel with, and about the axis, though not always in it, presenting a character similar to those described in section 217 ; the cause appears to be, that in the progress of cooling such a mass the exterior cools first and becomes rigid, while the internal portions are still red-hot and soft. The external parts contract as they cool, but they already grasp, in perfect contact, the still hot ON WROUGHT IROE IN LARGE MASSES. 127 interior; the exterior therefore cannot contract fully, but becomes solid under constraint circumferentially, partly itself extended in virtue of its compressing the still hot and soft interior. The latter at length also becomes cold and rigid; but its contraction is now- resisted by the rigid arch of the exterior with which it is surrounded. The contraction of the interior, therefore, is limited to taking place radially outwards from the centre; and thus the mass rends itself asunder in some one or more planes parallel to the axis of the cylinder. “Inacylindric mass of forged iron, varying from 24 to 36 inches in diameter, rents of 18 inches in width across a diameter were found, with jag- F >g- 82 * ged counterpart surfaces clearly torn as¬ under, and about fths of an inch apart at the widest or central part; the fact is most instructive as to the enormous in¬ ternal strains that must exist from like causes in cast-iron guns and mortars of large size.” We give a sketch (Fig. 82) of the form of this forging, showing the faults or “ fis¬ sures” that were found in it, and which no doubt took place from contraction after the piece had left the hammerman’s hands perfectly sound. When the forging was cooling, the part D would of course cool first; and as there was no great differential diameter between D and B, the differential con¬ traction was not greater than the elas¬ ticity of the materials permitted; but the sudden and great difference in the diam¬ eters B and A caused the forging at B to be comparatively cool; whilst the forg¬ ing at A had very considerable heat, the parts of the forging at B and D, being nearly cold, became rigid and unalter¬ able, constituting a very strong arch, which prevented the forging from con¬ tracting in a regular manner. If this forging had been of one uni¬ form cylindrical shape, these fissures would not have taken place, as the con¬ traction would have been uniform throughout, at the same time the conducting power of iron is sufficient to allow of the heat passing from the interior to the outside with sufficient rapidity to prevent any fissure or unsoundness taking place in the forging. Mr. Mallet proceeds to say—“It is probably from this cause that more or less hollowness is found in the centre of almost every large 128 THE PRACTICAL METAL-WORKER’S ASSISTANT. forging, greater in proportion as the forging is larger. The difficulty is one not easily overcome. Very slow, and, as far as possible, uni¬ form cooling of the whole mass in an annealing oven, suggests itself as one remedy; but this has disadvantages in enlarging the crystal¬ line development of the metal, or providing a central cylindrical opening, so as to cool the circumference and the centre together.” Here, at last, we come to a tangible danger to be feared in the manufacture of large forgings, provided that due care and atten¬ tion be not paid to its proper manipulation. But this danger is also common to castings, being created not by equal, but by dif¬ ferential contraction. There is nothing more to be dreaded in casting metals of any sort, but more especially those in which the contraction is great, than that any part of the casting should be suddenly reduced or increased in size. "When this is the case, what the founders call “ a draw” evidently takes place; and the same result is observed in large forgings, from the cooling of the smaller portions before the larger. In such a case as this, let us fol¬ low the practice of the engineer and founder, who, from experi¬ ence and long practice, discourage such shapes as are found im¬ practicable, and make such modifications in their plans as shall do away with these differential results. Whilst Mr. Mallet’s work was passing through the press, and without any communication from him, the maker of the forgings he mentions, after three failures, overcame the difficulty in the manner proposed: viz., by making a cylindrical opening in the centre, which allowed the interior of the forgings to cool as rapidly as the external ring, and which permitted the necessary contrac¬ tion without producing fissures. To endeavor to overcome the difficulties incident to an important manufacture, which is still in its infancy, appears to be much preferable to the theory and max¬ ims of the “Ilow-not-to-do-it” school, who would sit quietly down under a difficulty without attempting to remove it. In the Report, made by a Committee of the Franklin Institute, on the bursting of the wrought-iron gun on board the United States steam-frigate “Princeton,” the following facts were elicited: “1. The iron of which the gun was principally made u r as capa¬ ble of being rendered of a good quality by sufficient working. “2. From the state in wffiich the iron v r as put into the gun, it was not in a proper condition for the purpose to which it w r as ap¬ plied. “3. The metal, as it existed in the gun, was decidedly bad. “4. As to the manufacture of the gun, the welding w r as imperfect. “These facts relate exclusively to the gun submitted to the ex¬ amination of the committee, and they are derived from immediate experiments and observation. But besides giving these to the public, the committee felt themselves bound to express the opinion, that in the present state of the arts the use of v r rought-iron guns of large calibre, made on the same plan as the gun now under ex¬ amination, ought to be abandoned for the following reasons: ON WROUGHT-IRON IN LARGE MASSES. 129 " 1. The practical difficulty, if not impossibility, of welding such a large mass of iron, so as to insure perfect soundness and uni¬ formity throughout. “ 2. The uncertainty that will always prevail in regard to imper¬ fections in the welding. And, “ 3. From the fact that iron decreases in strength from long ex¬ posure to the intense heat necessary in making a gun of this size, without a- possibility of restoring the fibre by hammering with the hammer at present in use in this country. At the same time the committee would not wish to be understood as expressing any opinion whether the construction of a safe wrought-iron gun upon some other plan is practicable or otherwise, in the present state of the arts, inasmuch as this subject has not been referred to them by the Department.” We are sorry that Mr. Mallet thinks it necessary to add to this Report, which he quotes at length in his valuable work on the “ Construction of Artillery,” the following remarks: “Nothing can more strikingly show the deteriorating effects of forging in large masses (however done) upon the tenacity of wrought-iron, than the fact of the preceding Report, nor the un¬ certainty of the process as respects welding. That the latter diffi¬ culty may be greatly mitigated (though it cannot be removed) by pre-eminent skill on the part of the hammerman, is proved by the success of the Mersey Steel Company in the duplicate perfected by them of the gun which failed for the ' Princeton,’ and still more in the stupendous and apparently perfect forging they have now almost finished into a gun for the Government, no doubt by far the largest ever made in one piece, being 131 feet length of chase, 13 inches calibre, 14 or 15 inches thick at the charge, and about 9 inches at the muzzle, a solid shot of which will weigh 300 lbs.” Mr. Mallet thus gives the weight of his authority (for which we entertain the greatest respect) to sentiments which, in our opinion, hardly need any further refutation than the facts which he himself mentions. The several failures in the manufacture of wrought-iron guns should not be a matter of surprise; 'for it is hardly reasonable to expect immediate success in any new fabrication. How many failures, it might b.e asked, occurred before cast-iron guns were brought to the comparative perfection they have now reached? When we consider that an attempt has been successfully made to construct two of the largest guns ever attempted of wrought-iron, without having had any failure to record, we think it hardly pro¬ bable that failure should occur where sufficient skill in workman¬ ship is used, and with it added experience. It would, indeed, be somewhat strange, if, with additional experience, less successful results were to be obtained than in the first comparatively novel experiments. One of the most common forms of real crystallization results from what is technically called “ hammer-hardening.” In the yeai 9 130 THE PRACTICAL METAL-WORKER’S ASSISTANT. 1854, at the meeting of the British Association in Liverpool, a paper was read by the writer of this article on the subject of crys¬ tallization of iron under certain circumstances. He selected a piece of good, tough, fibrous bar-iron, which he tested by treating in the usual manner. He then heated it to a full red heat, and hammered it by light, rapid, tapping blows, until it was what is called “black-cold.” After it was allowed to cool, he again broke it, and found that the structure of the iron was entirely changed; and that, instead of bending nearly double without fracture, and, when the fracture did occur, breaking with a fine, silky fibre, an entire alteration had taken place, and the bar was of a rigid, brit¬ tle, sonorous character, incapable of bending in the slightest de¬ gree, but breaking with a glassy, crystallized appearance. By simply heating the bar to the same red-heat again, the fibre w&s restored exactly as before. This change in the structure of iron has been observed in railway axles and chains; and we believe that it is now customary, in some manufactories, to anneal such articles as are exposed to any jar or percussion, at regular periods, and with a beneficial result. Now this crystallization is particu¬ larly to be dreaded in forgings, for, unless great care is used, this error of “ hammer-hardening” will often take place—sometimes from the vanity of the forge-man, who is naturally desirous to turn out a pretty well-finished forging; at other times, as is more gen¬ erally the case, from the requisition of the engineer, who, without thinking of the result, wishes to have his forging delivered to him as nearly as possible to the finished size ; and when, as is often the case, a very small allowance or margin is given between the forged and finished dimensions, the forge-man is under the necessity of working his iron much colder than is consistent with a due regard to strength. It is very true that some forge-men will work much nearer to the sizes given them than others, and still avoid the dan¬ gerous error of cold-hammering; but when certain dimensions are a sine qua non, inferior workmen, to keep anywhere near the mark, must “ cold-hammer” their work; for none but a first-rate work¬ man, and one who has every confidence in his own powers, dare bring his iron down to the required size at full heat. Some engineers, and we have known instances among the most eminent, in ordering their forgings, have made the remark —“ Pray take care not to finish the work too cold, for we do not care for a fine polish to our forgings;” and this language we would urge all engineers to use. Such an instruction shows a true appreciation of the danger of cold-hammering, and a knowledge of his craft, which it is the object of this work to convey to all. But while we have a very strong objection to cold-hammered forgings, we should be sorry to be understood as encouraging that slovenly description of forging, which leaves the pieces so clumsy and unsightly as to require more than a necessary amount of cutting or turning. This is an error that ought also to be avoided. If proper care and attention were paid to the quality of the material used, as well as GENERAL EXAMPLES OF WELDING. 131 to the workmanship, we should have fewer break-downs in our sea-going steamers, and might, with perfect safety and great advan¬ tage, reduce the weight of those parts that are made of wrought- iron. In the selection of forgings, the cheapest are generally a long way from being the least costly; for the extra weight of mate¬ rial used, often brings the actual cost up to a level with the dearer, but better-finished and lighter forgings. Where cheapness of first cost is the rule, though accepted as the cheapest, it will, in all probability, be the dearest in the end. In concluding this chapter, we would observe, that the opin¬ ions and facts here developed (although the result of long practical experience) have been put together at a short notice, during the pressure of onerous business engagements, which permitted but little time to be devoted to the subject. The author does not for a moment pretend to treat this important subject in the scientific manner that it deserves ; but, when requested, he gave his humble assistance to further, though in a slight degree, the development of knowledge on a subject which has hardly ever received the attention of those practically competent to write upon it; but which, he is convinced, is of great and growing importance to the country, as a national manufacture in which it stands proudly pre¬ eminent. Should, however, the few remarks which we have put together awaken more inquiry, and further investigation of the subject, by those who have leisure and ability to pursue it, the author will re¬ joice that his humble endeavors have not been altogether in vain. CHAPTER VIII. GENERAL EXAMPLES OF WELDING. The former illustrations of forging have been to some extent de¬ scriptive of such works as could be made from a single bar of iron, on purpose that the examples to be advanced in welding or joining together two pieces of iron by heat, technically called “shutting together ,” or “ shutting-up,” might be collected at one place. There are several ways of accomplishing this operation, and which bear some little analogy to the joints employed in carpentry; more particularly that called scarfing, used in the construction of long beams and girders by joining two shorter pieces together end¬ ways, with sloping joints, which in carpentry are interlaced or mortised together in various ways, and then secured by iron straps or bolts. In smith’s work, likewise, the joinings are called scarfs, but from the adhesive nature of the iron when at a suitable tem 132 THE PRACTICAL METAL-WORKER’S ASSISTANT. perature, the accessories called for in carpentry, such as glue, bolts, straps and pins, are no longer wanted. The example, Fig. 58, was left unfinished, but we will proceed to show the mode of joining the two cylindrical ends of the work. The scarfs required for the “shut, 1,1 are made by first upsetting or thickening the iron by blows upon its extremity, to prepare it for the loss it will sustain from scaling off, both in the fire and upon the anvil, and also in the subsequent working upon the joint. It is next rudely tapered off to the form of a flight of steps, as shown in Figs. 88 and 84, and the sides are slightly beveled or pointed, as in Fig. 84, the proportions being somewhat exceeded to render the forms more apparent. The two extremities are next heated to the point of ignition; and when this is approached, a little sand is strewed upon each part, which fuses and spreads something like a varnish, and parti¬ ally defends them from the air; the heat is proper when, notwith¬ standing the sand, the iron begins to burn away with vivid sparks. The two men then take each one piece, strike them forcibly across the anvil to remove any loose cinders, place them in their true positions, exactly as in Fig. 83, and two or three blows of the small hammer of the principal or fireman stick them together; the assistant then quickly joins in with the sledge-hammer, and the smoothing off and completion of the work are soon accomplished. It is of course necessary to perform the work with rapidity, and literally “ to strike whilst the iron is hotthe smith afterwards jumps the end of the rod upon the anvil, or strikes it endways with the hammer; this proves the soundness of the joint, but it is mostly done to enlarge the part, should it during the process have become accidentally reduced below the general size. The sand appears to be quite essential to the process of welding, as although the heat might be arrived at without its agency, the surface of the metal woqld become foul and covered with oxide when unprotected from the air—at all events common experience shows that it is always required. The scarf joint, shown in Figs. 83 and 84, is commonly used for all straight bars, whether flat, square or round, when of medium size. GENERAL EXAMPLES OF WELDING. 133 In very heavy works the welding is principally accomplished within the fire: the two parts are previously prepared either to the form of the tongue or split joint, Fig. 85, or to that of the butt joint, Fig. 86, and placed in their relative positions in a large hollow fire. When the two parts are at the proper heat, they are jumped together endways, which is greatly facilitated by their suspension from the crane, and they are afterwards struck on the ends with sledge-hammers, a heavy mass being in some cases held against the opposite extremity to sustain the blows; the heat is kept up, and the work is ultimately withdrawn from the fire, and finished upon the anvil. The butt joint, Fig. 86, is materially strengthened, when, as it is usually the case for the paddle shafts of steam vessels and similai works, the joint whilst still large is notched in on three or four sides, and pieces called stick-in pieces, dowels, or charlins, one of which is represented by the dotted lines, are prepared by another fire, and laid in the notches; the whole, when raised to the weld¬ ing heat, is well worked together and reduced to the intended size; this mingles all the parts in a very substantial manner. For the majority of works, however, the scarf joint, Fig. 83, is used, but the stick-in pieces are also occasionally employed, especially when any accidental deficiency of iron is to be feared. When two bars are required to form a T joint, the transverse piece is thinned down as at a, in Fig. 87; for an angle or corner the form of b may be adopted; but c, in which each part is cut off ob¬ liquely, is to be preferred. The pieces a, b, c, are represented up¬ side down, in order that the ridges set down on their lower sur¬ faces may be seen. In most cases when two separate bars are to be joined, whatever the nature of the joint, the metal should be first upset, and then set down in ridges on the edge of the anvil, or with a set hammer, as the plain chamfered or sloping sur¬ faces are apt to slide asunder when struck with the hammer, and prevent the union. When a T joint is made of square or thick iron, the one piece is upset, and moulded with the fuller much in the form of the letter; it is then welded against the flat side of the bar: such works are sometimes welded with dowel or tenon joints, but all the varieties of method cannot be noticed. There are many works in which the opposite edges, or the ends of the same piece, require to be welded. In these the risk of the two parts sliding asunder scarcely exists, and the scarfs are made with a plain chamfer, or simply to overlap or fold together with¬ out any particular preparation. Of the last kind Fig. 63 may be taken as an example, in which the parts have no disposition to separate. In this and similar cases the smith often leaves the parts slightly open, in order that the very last process before welding may be the striking the whole edgeways upon the anvil, to drive out any loose scales, cinders or sand, situated between the joints : which if allowed to remain 134 THE PRACTICAL METAL-WORKER’S ASSISTANT. would be either inclosed amidst the sound parts of the work, or would partially prevent the union. In works that have accidentally broken in the welded part, the fracture will be frequently seen to have arisen from some dirty matter having been allowed to remain between them, on which account, shuts or welded joints extending over a large surface are often less secure than those of smaller area, from the greater risk of their becoming foul. In fact, throwing a little small coal be¬ tween the contiguous surfaces of "work not intended to be united, is a common and sometimes a highly essential precaution to pre¬ vent them from becoming welded. The conical sockets of socket chisels, garden spuds, and a variety of agricultural implements, are formed out of a bar of flat iron, which is spread out sideways or to an angle, with the pane of the hammer, and then bent within a semi-circular bottom tool also, by the pane of the hammer, to the form of Fig. 88; after which the sockets are still more curled up by blows on the edges, and are Figs. 88 89. perfected upon a taper-pointed mandrel, so that the two edges slightly overlap at the mouth of the socket, and meet pretty uni¬ formly elsewhere, as in Fig. 89, and lastly, about an inch or more at the end is welded. Sometimes the welding is continued through¬ out the length, but more commonly only a small portion of the extremity is thus joined, and the remainder of the edges are drawn together with the pane of the hammer. In making wrought-iron hinges, two short slits are cut length¬ ways and nearly through the bar, towards its extremity. The iron is then folded round a mandrel, set down close in the corner, and the two ends are welded together. To complete the hinge, it only remains to cut away transversely, either the central piece or the two external pieces to form the knuckles, and the addition of the pin or pivot finishes the work. Musket barrels, when made entirely by hand, were forged in the form of long strips about a yard long and four inches wide, but taper both in length and width, which were bent round a cylin¬ drical mandrel until their edges slightly overlapped. They were then welded at three or four heats by introducing the mandrel within them instantly on their removal from the fire at the proper heat, in order to prevent the sides of the tube from being pressed together by the blows of the hammer. They have been subsequently and are now universally welded by machinery, at one heat; and whilst of the length of only one foot, as on removal from the fire the mandrel is quickly intro¬ duced, and the two are passed through a pair of grooved rollers. They are afterwards extended to the full length by similar means, GENERAL EXAMPLES OF WELDING. 135 but at a lower temperature, so that the iron is not so much injured as when thrice heated to the welding point. The twisted barrels are made out of long ribands of iron wound spirally around a mandrel, and welded on the r edges by jumping them upon the ground, or rather on an anvil embedded therein. The plain stub barrels are ma le in this manner, from iron manu¬ factured from a bundle of stub-nails, welded together and drawn out into ribands, to insure the possession of a material most thor¬ oughly and intimately worked. The Damascus barrels are made from a mixture of stub-nails and clippings of steel in given pro¬ portions, puddled together, made into a bloom, and subsequently passed through all the stages of the manufacture of iron already explained: to obtain an iron that shall be of unequal quality and hardness, and therefore display different colors and markings when oxidized or browned. Other twisted barrels are made in the like manner, except that the bars to form the ribands are twisted whilst red-hot like ropes, some to the right, others to the left, and which are sometimes again laminated together for greater diversity. They are subsequently again drawn into the ribands and wound upon the mandrel, and frequently two or three differently-prepared pieces are placed side by side to form the complex and ornamental figures for the barrels of fowling-pieces, described as “stub-twist, wire-twist, Damascus- twist ,” etc. A method amongst others of the formation of the Damascus gun- barrels : By arranging twenty-five thin bars of iron and mild steel in alternate layers, welding the whole together, drawing it down small, twisting it like a rope, and again welding three such ropes, for the formation of the riband, which is then spirally twisted to form a barrel, that exhibits, when finished and acted upon by acids, a diversified laminated structure, resembling when properly man¬ aged an ostrich feather. When the illumination by gas was first introduced in the large way, the old musket-barrels, laid by in quiet retirement from the fatigues of war, were employed for the conveyance of gas; and by a curious coincidence, various iron foundries desisted in a great measure from the manufacture of iron ordnance, and took up the peaceful employment of casting pipes for gas and water. The breech ends of the musket-barrels were broached and tapped, and the muzzles were screwed externally to connect the two without detached sockets. From the rapid increase of gas illu¬ mination, the old gun-barrels soon became scarce, and new tubes with detached sockets, made by the old barrel-forgers, were first resorted to. This led to a series of valuable contrivances for the manufacture of the wrought-iron tubes, under which the tubes were first bent up by hand-hammers and swages, to bring the edges near together; and the} 7- were welded between semi-circular swages, fixed respectively in the anvil, and the face of a small tilt- hammer worked by machinery, by a series of blows along the 136 THE PRACTICAL METAL-WORKER’S ASSISTANT. tube, either with or without a mandrel. The tube was completed on being passed between rollers with half-round grooves, which forced it over a conical or egg-shaped piece at the end of a long bar, to perfect the interior surface. Various steps of improvement have been since made. For in¬ stance, the skelps were bent at two squeezes, first to the semi- cylindrical and then to the tubular form (preparatory to welding), between a swage-tool five feet long worked by machinery. The whole process was afterwards carried on by rollers, but abandoned on account of the unequal velocity at which the greatest and least diameters of the rollers travelled. In the present method of manufacturing the patent welded tube, the end of the skelp is bent to the circular form, its entire length is raised to the welding heat in an appropriate furnace, and as it leaves the furnace almost at the point of fusion, it is dragged by the chain of a draw-bench, after the manner of wire, through a pair of tongs with two bell-mouthed jaws. These are opened at the moment of introducing the end of a skelp, which is welded without the agency of a mandrel. By this ingenious arrangement wrought-iron tubes may be made from the diameter of six inches internally and about one-eighth to three-eighths of an inch thick, to as small as one-quarter of an inch diameter and one-tenth bore ; and so admirably is the joining effected in those of the best description, that they will withstand the greatest pressure of gas, steam or water, to which they have been subjected, and they admit of being bent both in the heated and cold state almost with impunity. Sometimes the tubes are made one upon the other when greater thickness is required; but these stout pipes, and those larger than three inches, are compara¬ tively but little used. The wrought-iron tubes of hydrostatic presses, which measure about half an inch internally, and one- fourth to three-eighths of an inch thick in the metal, are fre¬ quently subjected to a pressure equal to four to?is on each square inch. Various articles, with large apertures, are made not by punch¬ ing or cutting out the holes, but by folding the metal around the beak iron and finishing them upon a triblet of the appropriate figure. Thus the complete smithy is generally furnished with a series of cones turned in the lathe, for making rings, the ends of which are folded together and welded, such as Fig. 90. The same rings when made of such cast-steel as does not admit of being welded, are first punched with a small hole and gradually thinned out by blows around the margin until they reach the diameter sought. But this, like numerous other works, requires considera¬ ble forethought to proportion the quantity of the material to its ultimate form and bulk, so that the work may not in the end be¬ come either too slight or too heavy. Chains may be taken as another familiar example of welding. In these the iron is cut off with a plain chamfer, as from the annu- GENERAL EXAMPLES OF WELDING. 137 lar form of the links their extremities cannot slide asunder when struck. Every succeeding link is bent, introduced, and finally welded. In some of these welded chains the links are no more than half an inch long, and the iron wire one-eighth of an inch diameter. Several inches of such chain are required to weigh one pound. These are made with great dexterity by a man and a boy at a small fire. The curbed chains are welded in the ordinary form and twisted afterwards, a few links being made red-hot at a time for the purpose. The massive cable-chains are made much in the same manner, although partly by aid of machinery. The bar of iron, now one, one and a half, or even two inches in diameter, is heated, and the scarf is made as a plain chamfer by a cutting machine; the link is then formed by inserting the end of the heated bar within a loop in the edge of an oval disk which may be compared to a chuck fixed on the end of a lathe mandrel. The disk is put in gear with the steam-engine; it makes exactly one revolution, and throws itself out of motion; this bends the heated extremity of the iron into an oval figure. Afterwards it is detached from the rod with a chamfered cut by the cutting machine, which at one stroke makes the second scarf of the detached link, and the first of that next to be curled up. The link is now threaded to the extremity of the chain, closed together, and transferred to the fire, the loose end being carried by a traverse crane. When the link is at the proper heat, it is re¬ turned to the anvil, welded, and dressed off between top and bot¬ tom tools, after which the cast-iron transverse stay is inserted, and the link having been closed upon the stay, the routine is recom¬ menced. The work commonly requires three men, and the scarf is placed at the side of the oval link, and flatway through the same. In similar chains made by hand it is perhaps more cus¬ tomary to weld the link at the crown, or small end. The tires of wrought-iron wheels for locomotive engines and carriages, are in general bent to the circle by somewhat analogous means to those employed in chain-making, as are likewise the skelps for the twisted barrels of guns. The latter only require a mandrel or spindle with a winch-handle at the one extremity, and a loop for the end of the skelp, which is wound in contact with the mandrel by means of a fixed bar placed near the same. Such barrels are coiled up in three lengths, which are joined together after the spirals are welded. Wheels for railways display many curious examples of smith¬ ing ; thus some, except the nave, are made entirely by welding; others are partly combined with rivets; in all the nave or boss is a mass of cast-iron usually poured around the ends of the spokes. The common practice of welding the tires of railway wheels is now as follows: the tires are cut off with ridges in the centre, so as in meeting to form two angular notches, into which two thin iron wedges are subsequently welded radially; the four parts thus j38 the practical metal-worker’s assistant. united together in the form of a cross, make a very secure joint without the necessity for upsetting the iron, which would distort the form of the tire. The succeeding illustration of the practice of forging will be that of the formation of a hatchet, Figs. 91 and 92, which like many similar tools is made by doubling the iron around a mandrel, to form the eye of the tool; it will also permit the description of some other general proceedings and likewise the introduction of the steel for the cutting edge. D H In making the hatchet, a piece of flat iron is selected of the width of A E, and twice the length of A D ; it is thinned and extended sideways before it is folded together, to form the projections near B and F, by blows with the pane of the hammer or a round-edged fuller, on the lines A B to E F, but the metal must be preserved of the full thickness at the part A E, to form the poll of the hatchet, although a piece of steel is frequently welded on at that part as a previous step. The work is then bent round a mandrel, Figs. 93 and 94, exactly of the section of the eye as seen in Fig. 92, and the work is welded across the line B F; the mandrel is again in¬ troduced, and the eye is perfected. A slip of shear-steel, equal in length to D II, is next inserted be¬ tween the two tails of the iron, as yet of their original size, up to the former weld, and all three are welded together between C, G, D. II: the combined iron and steel are now drawn out sideways, by blows of the pane of the hammer on and between C D and G II, to extend them together to I J. The tool is then flattened and smoothed with the face of the hammer, and the edges are pared with straight or circular chisels to the particular pattern, and trimmed with a round-faced hammer, or a top fuller. In smoothing off the work, the smith pursues his common method of first removing with a file the hard black scales that appear like spots when the work is removed from the fire; he then dips the hammer in the slake trough, and lets fall upon the anvil a few drops of the water it picks up, the explosion of which when the red-hot metal is struck upon it, makes a smart report and detaches the scales that would be otherwise indented in the work. It should be observed that the mandrel, Fig. 93, is pur- GENERAL EXAMPLES OF WELDING. 139 posely made very taper, and is introduced into the hole from both sides, so that the eye may be smaller in the middle; when therefore the handle of the tool is carefully fitted and wedged in, the handle is, as it were, dove-tailed, and the tool can neither fly off* nor slip down the handle; the same mode is also adopted for the heads of hammers. In spades, and many similar implements, the steel is introduced between the two pieces of iron of which the tools are made; in others, as plane irons and socket chisels, it is laid on the outside, and the two are afterwards extended in length or width to the required size. The ordinary chisel for the smith’s shop is made by inserting the steel in a cleft, as in Fig. 85, and so is also the pane of a hammer; but the flat face of the hammer is sometimes stuck on whilst it continues at the extremity of a flat bar of steel; it is then cut off, and the welding is afterwards completed. At other times the face of the hammer is prepared like a nail, with a small spike and a very large head, so as to be driven into the iron to retain its position, until finally secured by the operation of welding. In putting a piece of steel into the end of an iron rod to serve for a centre, the bar is heated, fixed horizontally in the vice, and punched lengthways with a sharp square punch for the reception of the steel, which is drawn down like a taper tang or thick nail, and driven in; the whole is then returned to the fire, and when at the proper heat united by welding, the blows being first directed as for forming a very obtuse cone, to prevent the piece of steel from dropping out. For some few purposes the blistered steel is used for welding, either to itself or to iron; it is true the first working under the hammer in a measure changes it to the condition of shear-steel, but less efficiently so than when the ordinary course of manufacture is pursued, as the hammering is found to improve steel in a remark¬ able and increasing degree. For the majority of works in which it is necessary to weld steel to iron, or steel to steel, the shear, or double shear, is exceedingly suitable; it is used for welding upon various cutting tools, as the majority of cast-steel will not endure the heat without crumbling under the hammer. Shear-steel is also used for various kinds of springs, and for some cutting tools requiring much elasticity. It is more usual to reserve the cast-steel for those works in which the process of welding is not required, although of late years mild cast-steel, or welding cast-steel, containing a smaller proportion of carbon has been rather extensively used; but in general the harder the steel the less easily will it admit of welding, and not unfrequently it is altogether inadmissible. The hard or harsh varieties of cast-steel, are somewhat more manageable when fused borax is used as a defence instead of sand, either sprinkled on in powder or rubbed on in a lump: and cast- Bteel otherwise intractable may be sometimes welded to iron by first 140 THE PRACTICAL METAL-WORKER’S ASSISTANT. heating the iron pretty smartly, then placing the cold steel beside it in the fire, and welding them the moment the steel has acquired its maximum temperature, by which time the iron will be fully up to the welding heat. When both are put into the fire cold alike, the steel is often spoiled before the iron is nearly hot enough, and therefore it is generally usual to heat the iron and steel sepa¬ rately, and only to place them in contact towards the conclusion of the period of getting up the heat. In forging works either of iron or steel, the uniformity of the hammering tends greatly to increase and equalize the strength of each material; and in steel, judicious and equal forging greatly lessens also the after-risk in hardening. When cast-steel has been spoiled by overheating, it may be par¬ tially recovered by four or five reheatings and quenchings in water, each carried to an extent a little less and less than the first excess; and lastly, the steel must have a good hammering at the ordinary red heat. Some go so far as to prefer for cutting tools the steel thus recovered, but this seems a most questionable policy, although the change wrought by this treatment is really remarkable; as the fragment broken off from the bar in the spoiled state, and another from the same bar after part restoration and hardening, will ex¬ hibit the extreme characters of coarse and fine. The hammering I suspect to be the principal requisite, and in superior tools it should be continued until the work is nearly cold, to produce the maximum amount of condensation before harden¬ ing ; but no hammering will restore the loss of tenacity consequent upon the over-heating, or even the too frequent heating, of steel, without excess. Concluding Remarks on Forging ; and the Applications of Heading Tools, Swage Tools, Punches, etc.— With the utmost care and unlimited space, it would have been quite impos¬ sible to have conveyed the instructions called for, in forging the thousand varieties of tools, and parts of mechanism the smith is continually called upon to produce; and all that could be reason¬ ably attempted in this place, was to convey a few of the general features and practices of this most useful and interesting branch of industry. It is hoped, that such combinations of these methods may be readily arrived at as will serve for the majority of or¬ dinary wants. The smith in all cases selects or prepares that particular form and magnitude of iron, and also adopts that order of proceeding, which experience points out as being the most exact, sound, and economical. In this he is assisted by a large assortment of vari¬ ous tools and moulds for such parts of the work as are often re¬ peated, or that are of a character sufficiently general to warrant the outlay, and to some of which I will advert. The heading tools, Figs. 53 and 54, are made of all sizes and varieties of form; some with a square recess to produce a square beneath the head, to prevent the bolt from being turned round in GENERAL EXAMPLES OF WELDING. 141 the act of tightening its nut; others for countersunk and round- headed bolts, with and without square shoulders: many similar heading tools are used for all those parts of work which at all resem¬ ble bolts, in having any sudden en¬ largement from the stem or shaft. The holes in the swage block, Fig. 95, are used after the manner of heading tools for large objects ; the grooves and recesses around its margin, also serve in a variety of works as bottom swages beyond the size of those fitted to the anvil. At the opposite extreme of the heading tools, as to size, may be noticed those constantly employed in producing the smallest kinds of nails, brads and rivets, of various denominations, some of which heading tools divide in two parts like a pair of spring forceps to release the nails after they have been forged. The forge used by the nail-makers is built as a circular pedestal with the fire in the centre and the chimney directly over it; the rock-staff of the bellows extends entirely around the forge, so that one of the four or five persons who work at the same fire is con¬ tinually blowing it, whence the fire is always at a heat proper for welding, and which keeps the nails sound and good. These kinds are called wrought nails and brads, in contradistinction to similar nails cut out of sheet-iron by various processes of shearing and punching, which latter kinds are known as cut brads and nails, and will be adverted to hereafter. The top and bottom rounding tools, Fig. 50, are made of all diameters for plain cylindrical works: and when they are used for objects the different parts of which are of various diameters, it requires much care to apply them equally on all parts of the work, that the several circles may be concentric and true one with the other, or possess one axis in common. To insure this condition some of these rounding tools are made of various and specific forms, for the heads of screws, for collars, flanges or enlargements, which are of continual occurrence in machinery; for the orna¬ mental swells or flanges about the iron work of carriages, and other works. Such tools, like the pair represented in Figs. 96 and 97, are called swage or collar tools ; they save labor in a most important degree, and are thus made. A solid mould, core or striker, exactly a copy of the work to be produced, is made of steel by hand-forging, and then turned in the lathe to the required form, as shown in Fig. 98. The top tool is first moulded to the general form in an appro¬ priate aperture in the swage block, Fig. 95, it is faced with steel like a hammer, and the core, Fig. 98, is indented into it; the blows Fig. 95. 142 THE PRACTICAL METAL-WORKER’S ASSISTANT. of the sledge-hammer not being given directly upon the core, but upon some hollow tool previously made; otherwise the core must be filed partly flat to present a plane surface to the hammer. The bottom tool, which is fitted to the anvil, is made in a similar man¬ ner, and sometimes the two are finished at the same time whilst Figs. 96 100 103 102 not, with the cold striker between them; their edges are carefully rounded with a file so as not to cut the work, and lastly they are hardened, under a stream of water. In preparing the work for the collar tools, when the projection is inconsiderable, the work is always drawn down rudely to the form between the top and bottom fullers, as in Fig. 48; but for greater economy, large works in iron are sometimes made by fold¬ ing a ring around them as in Fig. 56. The metal for a large ring is occasionally moulded in a bottom tool, like Fig. 99, and coiled up to the shape of Fig. 100, after which it is closed upon the central rod between the swages, and then welded within them. The tools are slightly greased, to prevent the work from hanging to them, and from the same motive their surfaces are not made quite flat or perpendicular, but slightly conical, and all the angles are obliterated and rounded. The spring swage tool, represented in Fig. 101, is used for some small manufacturing purposes; it differs in no respect from the former, except in the steel spring which connects the two parts; it is employed for light single hand-forgings. Other workmen use swage tools, such as Fig. 102, in which there is a square recess in the bottom tool to fit the margin of the top-tool so as to guide it exactly to its true position. In practice the recess in the bottom tool would be deeper, and taper or larger above to guide the tool more easily to its place; but if so drawn the figure would have been less distinct. This kind also may be used for single hand works, and is particularly suited to those which are of rectangular section, as the shoulders of table-knives; these do not admit of being twisted round, which movement furnishes the guide for the position of the top-tool in forging circular works. GENERAL EXAMPLES OP WELDING. 143 The smith has likewise a variety of punches of all shapes and sizes, for making holes of corresponding forms; and also drifts or mandrels, used alone for finishing them, many of which, like the turned cones, are made from a small to a large size to serve for objects of various sizes. Two examples of the very dexterous use of punches, are in the hands of almost every person, namely ordi¬ nary scissors and pliers. The first are made from a small bar of flat steel; the end is flat- Figs. 104 105 tened and punched with a small round hole, which is gradually opened upon a beak-iron, Fig. 103, attached to the square hole of the anvil; the beak-iron has a shallow groove (accidentally omitted) for rounding the inside of the bows. The remaining parts of the scissors are moulded jointly b}^ the hammer, and bottom swage tools; but the bows are mostly finished by the eye alone. In some pliers, the central half of the joint is first made; the aperture in the other part is then punched through sideways, and Figs. 106 107 sufficiently bulged out to allow the middle joint to be passed through, after which the outsides are closed upon the centre. This proceeding exhibits, in the smallest kinds especially, a surprising degree of dexterity and dispatch, only to be arrived at by very great practice; and which in this and numerous other instances of manufacture could be scarcely attained but for the enormous de- 144 THE PRACTICAL METAL-WORKER’S ASSISTANT. maud, which enables a great subdivision of labor to be success¬ fully applied to their production. Figs. 104, 105, 106 and 107 represent the ordinary trip and tilt hammer used in this country. The drawings are taken from those manufactured at the Lowell Machine Shop, Lowell, Mass., of which W. A. Burke is the superintendent. The smaller trip-hammers are mounted with iron bed-pieces firmly bolted on large timber, furnished with a cast-iron stake, adapted to drawing and swaging spindles, bolts, and other small work, balance wheels on cam-shaft, and a husk adjustable by bolts and screws; the hammer-head weighing from thirty to one hundred and twenty-five pounds, driven by a belt. The heavy trip-hammer, manufactured in this shop, has a very heavy strong cast-iron frame, adjustable husk, cast-iron stake, driven by belt with balance-wheel on cam-shaft, and suited to a hammer-head weighing from one hundred and twenty-five to four hundred pounds. CHAPTER IX. HARDENING AND TEMPERING. General View of the Subject. —When the malleable metals are hammered or rolled, they generally increase in hardness,, in elasticity, and in density or specific gravity; which effects are pro¬ duced simply from the closer approximation of their particles, and in this respect steel may be perhaps considered to excel, as the process called hammer-hardening, which simply means hammer¬ ing without heat, is frequently employed as the sole means of har¬ dening some kinds of steel springs, and for which it answers re¬ markably well. After a certain degree of compression, the malleable metals assume their closest and most condensed states; and it then be¬ comes necessary to discontinue the compression or elongation, as it would cause the disunion or cracking of the sheet or wire, or else the metal must be softened by the process of annealing. The metals, lend, tin, and zinc, are by some considered to be perceptibly softened by immersion in boiling water: but such of the metals as will bear it are generally heated to redness, the co¬ hesion of the mass is for the time reduced, and the metal becomes as soft as at first, and the working and annealing may be thus alternately pursued, until the sheet metal, or the wire, reaches its limit of tenuity. The generality of the metals and alloys suffer no very observ¬ able change, whether or not they are suddenly quenched in water HARDENING AND TEMPERING. 145 from the red heat. Pure hammered iron, like the rest, appears after annealing, to be equally soft whether suddenly or slowly cooled; some of the impure kinds of malleable iron harden by im¬ mersion, but only to an extent that is rather hurtful than useful, and which may be considered as an accidental quality. Steel however receives by sudden cooling that extreme degree of hardness combined with tenacity, which places it so incalculably beyond every other material for the manufacture of cutting tools; especially as it likewise admits of a regular gradation from extreme hardness to its softest state, when subsequently re-heated or tempered. Steel therefore assumes a place in the economy of manufacture un¬ approachable by any other material: consequently we may safely say that without it, it would be impossible to produce nearly all our finished works in metal and other hard substances; for although some of the metallic alloys are remarkable for hardness, and were used for various implements of peaceful industry, and also those of war, before the invention of steel, yet in point of absolute and enduring hardness, and equally so in respect to elasticity and ten¬ acity, they fall exceedingly short of hardened steel. Hammer hardening renders the steel more fibrous and less crys¬ talline, and reduces it in bulk; on the other hand, fire hardening makes steel more crystalline, and frequently of greater bulk; but the elastic nature of hammer hardened steel will not take so wide nor so efficient a range as that which is fire hardened. If we attempt to seek the remarkable difference between pure iron and steel in their chemical analyses, it appears to result from a minute portion of carbon; and cast-iron, which possesses a much larger share, presents, as we should expect, somewhat, similar phenomena. Iron semi-steelified ...... Soft cast-steel capable of welding . . . Cast-steel for common purposes Cast-steel requiring more hardness Steel capable of standing a few blows, but quite unfit for drawing . . . . . First approach to a steely granulated fracture White cast-iron ....... Mottled cast-iron ...... Carbonated cast-iron . . . . . . Super-carbonated crude iron . . . . contains one 150th of carbon. “ 120th “ “ 100th “ “ 90th “ 50th “ “ 30th to 40th. “ 25th “ 20th “ “ 15th “ “ 12th “ For the mode of analysis for ascertaining the quantity of carbon in cast-iron and steel, invented by M. Y. Regnault, Mining Engi¬ neer, see Annales de Chimie et de Physique, for January, 1889; also Journal of the Franklin Institute, vol. xxv. p. 327. It is stated that the analysis is very easy and exact, and may be completed in half an hour. Moreover, as the hard and soft conditions of steel may be re¬ versed backwards and forwards without any rapid chemical change in its substance, it has been pronounced to result from internal 10 146 THE PRACTICAL METAL-WORKER'S ASSISTANT. arrangement or crystallization, which maybe in a degree illustrated and explained by similar changes observed in glass. A wine-glass, or other object recently blown, and plunged whilst red hot into cold water, cracks in a thousand places, and even cooled in warm air it is very brittle, and will scarcely endure the slightest violence or sudden change of temperature; and visitors to the glass-house are often shown that a wine-glass, or other article of irregular form, breaks in cooling in the open air from its un¬ equal contraction at different parts. But the objects would have become useful, and less disposed to fracture, if they had been allowed to arrange their particles gradually during their very slow passage through the long annealing oven or leer of the glass-house, the end at which they enter being at the red heat, and the opposite extremity almost cold. To perfect the annealing, it is not unusual with lamp-glasses, tubes for steam-gages, and similar pieces exposed to sudden transi¬ tions of heat and cold, to place them in a vessel of cold water, which is slowly raised to the boiling temperature, kept for some hours at that heat and then allowed to cool very slowly : the effect thus produced is far from chimerical. For such pieces of flint glass intended for cutting, as are found to be insufficiently an¬ nealed, the boiling is sometimes preferred to a second passage through the leer: lamp-glasses are also much less exposed to frac¬ ture when they have been once used, as the heat, if not too sud¬ denly applied or checked, completes the annealing. Steel in like manner when suddenly cooled is disposed to crack in pieces, which is a constant source of anxiety; the danger in¬ creases with the thickness in the same way as with glass, and the more especially when the works are unequally thick and thin. Another ground of analogy between glass and steel appears to exist in the pieces of unannealed glass used for exhibiting the phe¬ nomena formerly called double refraction, but now polarization of light; an effect distinctly traced to its peculiar crystalline structure. In glass it is supposed to arise from the cooling of the external crust more rapidly than the internal mass ; the outer crust is there¬ fore in a state of tension, or restraint, from an attempt to squeeze the inner mass into a smaller space than it seems to require; and from the hasty arrangement of the unannealed glass the natural positions of its crystals are in a measure disturbed or dislocated. Jt has been shown experimentally, that a re-arrangement of the particles of glass occurs in the process of annealing, as, of two pieces of the same tube each 40 inches long, the one sent through the leer contracted one-sixteenth of an inch more than the other, which was cooled as usual in the open air. Tubes for philosophi¬ cal purposes are not annealed, as their inner surfaces are apt to become soiled with the sulphur of the fuel; they are in conse¬ quence very brittle and liable to accident. The unannealed glass, when cautiously heated and slowly cooled, HARDENING AND TEMPERING. 147 ceases to present the polarizing effect, and the steel similarly treated ceases to be hard; and may we not therefore indulge in the speculation, that in both cases a peculiar crystalline structure is consequent upon the unannealed or hardened state ? In the process of hardening steel, water is by no means essen¬ tial, as the sole object is to extract its heat rapidly, and the follow¬ ing are examples, commencing with the condition of extreme hardness, and ending with the reverse condition. A thin heated blade placed between the cold hammer and anvil, or other good conductors of heat, becomes perfectly hard. Thicker pieces of steel, cooled by exposure to the air upon the anvil, be¬ come rather hard, but readily admit of being filed. They become softer when placed on cold cinders, or other bad conductors of heat. Still more soft when placed in hot cinders, or within the fire itself, and cooled by their gradual extinction. When the steel is encased in close boxes with charcoal powder, and it is raised to a red-heat and allowed to cool in the fire or furnace, it assumes its softest state ; unless, lastly, we proceed to its partial decomposition. This is done by enclosing the steel with iron turnings or filings, the scales from the smith’s anvil, lime, or other matters that will abstract the carbon from its surface; by this mode it is super¬ ficially decarbonized, or reduced to the condition of pure soft iron, in the manner practised by Mr. Jacob Perkins, of Massachusetts, in his most ingenious and effective combination of processes, employed for producing in unlimited numbers absolutely identi¬ cal impressions of bank notes and checks, for the prevention of forgery. These methods of treating steel will be hereafter noticed. A nearly similar variety of conditions might be referred to as existing in cast-iron in its ordinary state, governed by the magni¬ tude, quality, and management of the castings; independently of which, by one particular method, some cast-iron may be rendered externally as hard as the hardest steel; such are called chilled iron castings ; and, as the opposite extreme, by a method of annealing combined with partial decomposition, malleable iron castings may be obtained, so that cast-iron nails may be clenched. Again, the purest iron, and most varieties of cast-iron, may, by another proceeding, be superficially converted into steel, and then hardened, the operation being appropriately named case-hardening. 1 therefore propose to illustrate these phenomena collectively, under three divisions: first, the hardening and tempering of steel: secondly, the hardening and annealing of cast-iron; and thirdly, the process of case-hardening. Practice of hardening and tempering Steel. —It may per¬ haps be truly said, that upon no one subject connected with me¬ chanical art does there exist such a contrariety of opinion, not unmixed with prejudice, as upon that of hardening and tempering steel; which makes it often difficult to reconcile the practices fol¬ lowed by different individuals in order to arrive at exactly similar ends. The real difficulty of the subject occurs in part from the 148 THE PRACTICAL METAL-WORKER’S ASSISTANT. mysteriousness of the change ; and from the absence of defined measures, by which either the steps of the process itself, or the value of the results when obtained, may be satisfactorily measured; as each is determined almost alone by the unassisted senses of sight and touch, instead of by those physical means by which numerous other matters may be strictly tested and measured, nearly without reference to the judgment of the individual, which in its very nature is less to be relied upon. The excellence of cutting-tools, for instance, is pronounced upon their relative degrees of endurance, but many accidental circum¬ stances here interfere to vitiate the strict comparison : and in respect to the measure of simple hardness, nearly the only test is the resist¬ ance the objects offer to the file, a mode in two. ways defective, as the files differ amongst themselves in hardness; and they only serve to indicate in an imperfect manner to the touch of the individual, a general notion without any distinct measure, so that when the opinion of half a dozen persons may be taken, upon as many pieces of steel differing but slightly in hardness, the want of uniformity in their decisions will show the vague nature of the proof. Under these circumstances, instead of recommending any partic¬ ular methods, I have determined to advance a variety of practical examples derived from various sources, which will serve in most cases to confirm, but in some to confute one another; leaving to every individual to follow those examples which may be the most nearly parallel with his own wants. There are, however, some few points upon which it may be said that all are agreed; namely, The temperature suitable to forging and hardening steel differs in some degree with its quality and its mode of manufacture; the heat that is required diminishes with the increase of carbon: In every case the lowest available temperature should be employed in each process, the hammering should be applied in the most equal manner throughout, and for cutting tools it should be continued until they are nearly cold: Coke or charcoal is much better as a fuel than fresh coal, the sulphur of which is highly injurious: The scale should be removed from the face of the work to expose it the more uniformly to the effect of the cooling medium: Hardening a second time without the intervention of hammering is attended with increased risk; and the less frequently steel passes through the fire the better. In hardening and tempering steel there are three things to be considered; namely, the means of heating the objects to redness, the means of cooling the same, and the means of applying the heat for tempering or letting them down. I will speak of these sepa¬ rately, before giving examples of their application. The smallest works are heated with the flame of the blowpipe, and are occasionally supported upon charcoal; but as the blowpipe is used to a far greater extent in soldering, its management will be described in the chapter devoted to that process. HARDENING AND TEMPERING. 149 For objects that are too large to be heated by the blowpipe, and too small to be conveniently warmed in the naked fire, various pro¬ tective means are employed. Thus, an iron tube or sheet-iron box inserted in the midst of the ignited fuel is a safe and cleanly way ; it resembles the muffle employed in chemical works. The work is then managed with long forceps made of steel or iron wire, bent in the form of the letter U, and flattened or hollowed at the ends. A crucible or an iron pot about four to six inches deep, filled with lead and heated to redness, is likewise excellent, but more particu¬ larly for long and thin tools, such as gravers for artists, and other slight instruments; several of these may be inserted at once, although towards the last they should be moved about to equalize the heat; the weight of the lead makes it desirable to use a bridle or trevet for the support of the crucible. Some workmen place on the fire a pan of charcoal dust, and heat it to redness. Great numbers of tools, both of medium and large size, are heated in the ordinary forge fire, which should consist of cinders rather than fresh coals; coke and also charcoal are used, but far less gen¬ erally ; recourse is also had to hollow fires, the construction of which was explained at page 94 ; but the bellows should be very sparingly used, except in blowing up the fire before the introduc¬ tion of the work, which should be allowed ample time to get hot, or, as it is called, to “ soak.” Which method soever may be resorted to for heating the work, the greatest care should be given to communicate to all the parts requiring to be hardened a uniform temperature, and which is only to be arrived at by cautiously moving the work to and fro to expose all parts alike to the fire; the difficulty of accomplishing this of course increases with long objects, for which fires of proportionate length are required. It is far better to err on the side of deficiency than of excess of heat; the point is rather critical, and not alike in all varieties of steel. Until the quality of the steel is familiarly known, it is a safe precaution to commence rather too low than otherwise, as then the extent of the mischief will be the necessity for a repetition of the process at a higher degree of heat; but the steel, if burned or over-heated, will be covered with scales, and what is far worse, its quality will be permanently injured; a good hammering will, in a degree, restore it; but this in finished works is generally imprac¬ ticable. Less than a certain heat fails to produce hardness, and in the opinion of some workmen has quite the opposite effect, and they consequently resort to it as the means of rapid annealing; not, however, by plunging the steel into the water and allowing it to remain until cold, but dipping it quickly, holding it in the steam for a few moments, dipping it again and so on, reducing it to the cold state in a hasty but intermittent manner. There is another opinion prevalent amongst workmen, that steel which is “ pinny,” or as if composed of a bundle of hard wires, is 150 THE PRACTICAL METAL-WORKER’S ASSISTANT. rendered uniform in its substance if it is first hardened and then annealed. Secondly, the choice of the cooling medium has reference mainly to the relative powers of conducting heat they severally possess: the following have been at different times resorted to with various degrees of successcurrents of cold air; immersion in water in various states, in oil or wax, and in freezing mixtures; mercury, and flat metallic surfaces have been also used. Plain water, at a temperature of 40° Fahrenheit, has been recommended. On the whole, however, there appears to be an opinion that mercury gives the greatest degree of hardness; then cold salt and water, or water mixed with various “ astringent and acidifying mattersplain water follows; and lastly, oily mixtures. I find but one person who has commonly used the mercury. Many presume upon the good conducting power of the metal, and the non-formation of steam, which causes a separation betwixt the steel and water, when the latter is employed as the cooling me¬ dium. I have failed to learn the reason of the advantage of salt and water, unless the fluid have, as well as a greater density, a superior conducting power. The file-makers medicate the water in other ways, but this is one of the questionable mysteries which is never divulged,—although it is supposed that a small quantity of white arsenic is generally added to water saturated with salt. One thing, however, may be noticed, that articles hardened in salt and water are apt to rust, unless they are laid for a time in lime- water, or some neutralizing agent. With plain water, an opinion very largely exists in favor of that which has been used over and over again, even for years, provided it is not greasy: and when the steel is very harsh, the chill is taken off plain water to lessen the risk of cracking it. Oily mix¬ tures impart to thin articles, such as springs, a sufficient and milder degree of hardness, with less danger of cracking, than from water; and in some cases a medium course is pursued by covering the water with a thick film of oil, which is said to be adopted occa¬ sionally with scythes, reaping-hooks, and thin edge-tools. A so-called natural spring is made by a vessel with a true and a false-bottom, the latter perforated with small holes; it is filled with water, and a copious supply is admitted beneath the partition ; it ascends through the holes, and pursues the same current as the heated portions, which also escape at the top. This was invented by the late John Oldham, of Dublin, Engineer to the Bank of England, and was used by him in hardening the rollers for trans¬ ferring the impressions to the steel-plates for bank-notes. Sometimes when neighboring parts of works are required to be respectively hard and soft, metal tubes or collars are fitted tight upon the work, to protect the parts to be kept soft from the direct action of the water, at any rate for so long a period as they retain the temperature suitable to hardening. The process of hardening is generally one of anxiety, as the HARDENING AND TEMPERING. 151 sudden transition from heat to cold often causes the works to be¬ come greatly distorted if not cracked. The last accident is much the most likely to occur with thick massive pieces, which are, as it were, hardened in layers,—as although the external crust or shell may be perfectly hard, there is almost a certainty that towards the centre the parts are gradually less hard; and when broken, the inner portions will sometimes admit of being readily filed. When in the fire the steel becomes altogether expanded, and in the water its outer crust is suddenly arrested, but with a tendency to contract from the loss of heat, which cannot so rapidly occur at the central part; it may be therefore presumed that the inner bulk continues to contract after the outer crust is fixed, and which tends to tear the two asunder, the more especially if there be any de¬ fective part in the steel itself. An external flake of greater or less extent not unfrequently shells off in hardening; and it often happens that works remain unbroken for hours after removal from the water, but eventually give way and crack with a loud report, from the rigid unequal tension produced by the violence of the process of hardening. The contiguity of thick and thin parts is also highly dangerous, as they can neither receive nor yield up heat in the same times. The mischief is sometimes lessened by binding pieces of metal around the thin parts with wire, to save them from the action of the cooling medium. Sharp angular notches are also fertile sources of mischief, and where practicable they should be rejected in favor of curved lines. As regards both cracks and distortions, it may perhaps be generally said that their avoidance depends principally upon ma¬ nipulation, or the successful management of every step: first, the original manufacture of the steel, its being forged and wrought so that it may be equally condensed on all sides with the hammer, otherwise when the cohesion of the mass is lessened from its be¬ coming red hot, it recovers in part from any unequal state of den¬ sity in which it may have been placed. Whilst red hot it is also in its weakest condition. It is there¬ fore prone to injury, either from incautious handling with the tongs, or from meeting the sudden cooling action irregularly, and therefore it is generally best to plunge works vertically, as all. parts are then exposed to equal circumstances, and less disturbance is risked than when the objects are immersed obliquely or sideways into the water,—although for swords, and objects of similar form, it is found the best to dip them exactly as in making a vertical downward cut with a sabre, which for this weapon is its strongest direction. Occasionally objects are clamped between stubborn pieces of metal, as soft iron or copper, during their passage through the fire and water. Such plans can be seldom adopted, and are rarely fol¬ lowed, the success of the process being mostly allowed to depend exclusively upon good general management. 152 THE PRACTICAL METAL-WORKER’S ASSISTANT. In making the magnets for needles ten inches long, one-fourth of an inch wide, and the two-hundredth part of an inch thick, this precaution entirely failed; and the needles assumed all sorts of distortions when released from between the stiff bars within which they were hardened. The plan was eventually abandoned and the magnets were heated in the ordinary way within an iron tube, and were set straight with the hammer after being let down to a deep orange or brown color. Steel, however, is in the best con¬ dition for the formation of good permanent magnets when per¬ fectly hard. In all cases the thick unequal scale left from the forge should be ground off before hardening, in order to expose a clean metallic surface, otherwise the cooling medium cannot produce its due and equal effect throughout the instrument. The edges also should be left thick, that they may not be burned in the fire; thus it will frequently happen that the extreme end or edge of a tool is in¬ ferior in quality to the part within, and that the instrument is much better after it has been a few times ground. Thirdly, the heat for tempering or letting down. Between the extreme conditions of hard and soft steel there are many interme¬ diate grades, the common index for which is the oxidation of the brightened surface, and it is quite sufficient for practice. These tints, and their respective approximate temperatures, are thus tabulated: 1. Very pale straw yellow 2. A shade of darker yellow . 3. Darker straw yellow t 4. Still darker straw yellow . 5. A brown yellow .... 6. A yellow, tinged slightly with purple 7. Light purple .... 8. Dark purple .... 9. Dark blue ..... 10. Paler blue ..... 11. Still paler blue .... 12. Still paler blue, with a tinge of green 430 deg. 450 “ 470 “ 490 “ 500 520 “ 530 “ 550 “ 570 “ 590 “ 610 “ 630 “ | Tools for metals. | Tools for wood, and screw | taps, etc. 1 Hatchets chipping chisels, > and other percussive J tools, saws, etc. Springs. Too soft for the above pur¬ poses. ! The first tint arrives at about 430° F., but it is only seen by comparison with a piece of steel not heated: the tempering colors differ slightly with the various qualities of steel. The heat for tempering being moderate, it is often supplied by the part of the tool not requiring to be hardened, and which is not therefore cooled in the water. The workman first hastily tries with a file whether the work is hard; he then partially brightens it at a few parts with a piece of grindstone or an emery stick, that he may be enabled to watch for the required color; which attained, the work is usually cooled in any convenient manner, lest the body of the tool should continue to supply heat. But when, on the contrary, the color does not otherwise appear, partial recurrence is had to the mode in which the work is heated, as the flame of the caudle, or the surface of the clear fire applied, if possible, a HARDENING AND TEMPERING. 153 little below the part where the color is to be observed, that it may not be soiled by the smoke. A very convenient and general manner of tempering small ob¬ jects is to heat to redness a few inches of the end of a flat bar of iron about two feet long; it is laid across the anvil, or fixed by its cold extremity in the vice; and the work is placed on that part of its surface which is found by trial to be of the suitable tempera¬ ture, by gradually sliding the work towards the heated extremity. In this manner many tools may be tempered at once, those at the hot part being pushed off into a vessel of water or oil, as they severally show the required color, but it requires dexterity and quickness in thus managing many pieces. Vessels containing oil or fusible alloys carefully heated to the required temperatures have also been used, and I shall have to describe a method called “ blazing-off resorted to for many articles, such as springs and saws, by heating them over the naked fire until the oil, wax, or composition in which they have been hardened ignites; this can only occur when they respectively reach their boiling temperatures and are also evaporated in the gaseous form. The period of letting down the works is also commonly chosen for correcting, by means of the hammer, those distortions which so commonly occur in hardening; this is done upon the anvil, either with the thin pane of an ordinary hammer, or else with a hack¬ hammer, a tool terminating at each end in an obtuse chisel edge which requires continual repair on the grindstone. The blows are given on the hollow side of the work, and at right angles to the length of the curve; they elongate the concave side, and gradually restore it to a plane surface, when the blows are dis¬ tributed consistently with the position of the erroneous parts. The hack-hammer unavoidably injures the surface of the work, but the blows should not be too violent, as they are then also more prone to break the work, the liability to which is materially lessened when it is kept at or near the tempering heat, and the edge of the hack-hammer is slightly rounded. Common Examples of Hardening and Tempering Steel.—• Watchmakers’ drills of the smallest kinds are heated in the blue part of the flame of the candle; larger drills are heated with the blowpipe flame, applied very obliquely, and a little below the point; when very thin they may be whisked in the air to cool them, but they are more generally thrust into the tallow of the candle or the oil of a lamp; they are tempered either by their own heat, or by immersion in the flame below the point of the tool. For tools between those suited to the action of the blowpipe and those proper for the open fire, there are many which require either the iron tube, or the bath of lead or charcoal described at page 149, but the greater number of works are hardened in the ordinary smith’s fire, without such defences. Tools of moderate size, such as the majority of turning tools, carpenters’ chisels, and gouges, and so forth, are generally heated 154 THE PRACTICAL METAL-WORKER’S ASSISTANT. in the open fire; they require to be continually drawn backwards and forwards through the fire, to equalize the temperature applied, they are plunged vertically into the water, and then moved about sideways to expose them to the cooler portions of the fluid. If needful, they are only dipped to a certain depth, the remainder being left soft. Some persons use a shallow vessel filled only to the height of the portion to be hardened, and plunge the tools to the bottom; but this strict line of demarkation is sometimes dangerous, as the tools are apt to become cracked at the part, and therefore a small vertical movement is also generally given, that the transition from the hard to the soft part may occupy more length. Razors and penknives are too frequently hardened without the removal of the scale arising from the forging; this practice, which is not done with the best works, cannot be too much deprecated. The blades are heated in a coke or charcoal fire, and dipped into the water obliquely. In tempering razors, they are laid on their backs upon a clear fire, about half-a-dozen together, and they are removed one at a time, when the edges, which are as yet thick, come down to a pale straw color. Should the backs accidentally get heated beyond the straw color, the blades are cooled in water, but not otherwise. Penknife blades are tempered, a dozen or two at a time, on a plate of iron or copper about twelve inches long, three or four wide, and about a quarter of an inch thick ; the blades are arranged close together on their backs, and lean at an angle against each other. As they come down to the temper, they are picked out with small pliers and thrown into water if necessary; other blades are then thrust forward from the cooler parts of the plate to take their place. Hatchets, adzes, cold chisels, and numbers of similar tools, in which the total bulk is considerable compared with the part to be hardened, are only partially dipped; they are afterwards let down by the heat of the remainder of the tool, and when the color indic¬ ative of the temper is attained, they are entirely quenched. With . the view of removing the loose scales, or the oxidation acquired in the fire, some workmen rub the objects hastily in dry salt before plunging them in the water, in order to give them a cleaner and whiter face. In hardening large dies, anvils, and other pieces of considerable size, by direct immersion, the rapid formation of steam at the sides of the metal prevents the free access of the water for the removal of the heat with the required expedition; in these cases, a copious stream of water from a reservoir above is allowed to fall on the surface to be hardened. This contrivance is frequently called a “ float,” and although the derivation of the name is not very clear, the practice is excellent, as it supplies an abundance of cold water ; and which, as it falls directly on the centre of the anvil, is sure to render that part hard. It is, however, rather dangerous to stand near such works at the time, as when the anvil face is not perfectly HARDENING AND TEMPERING. 155 welded, it sometimes in part flies off with great violence and a loud report. Occasionally the object is partly immersed in a tank beneath the fall of water, by means of a crane and slings; it is ultimately tem¬ pered with its own heat, and dropped in the water to become en¬ tirely cold. Oil, or various mixtures of oil, tallow, wax, and resin, are used for many thin and elastic objects, such as needles, fish-hooks, steel pens and springs, which require a milder degree of hardness than is given by water. For example, steel pens are heated in large quantities in iron trays within a furnace, and are then hardened in an oily mixture; generally they are likewise tempered in oil, or a composition the boiling point of which is the same as the temperature suited to letting them down. This mode is particularly expeditious, as the temper cannot fall below the assigned degree. The dry heat of an oven is also used, and both the oil and oven may be made to serve for tempers harder than that given by boiling oil; but more care and observation are required for these lower temperatures. Saws and springs are generally hardened in various composi¬ tions of oil, suet, wax and other ingredients, which, however, lose their hardening property after a few weeks’ constant use: the saws are heated in long furnaces, and then immersed horizontally and edge-ways in a long trough containing the composition; two troughs are commonly used, the one until it gets too warm, then the other for a period, and so on alternately. Part of the composition is wiped off the saws with a piece of leather, when they are removed from the trough, and they are heated one by one over a clear coke fire, until the grease inflames; this is called “ blazing off.” The composition used by an experienced saw-maker is two pounds of suet and a quarter of a pound of bees-wax to every gallon of whale-oil; these are boiled together, and will serve for thin works and most kinds of steel. The addition of black resin, to the extent of about one pound to the gallon, makes it serve for thicker pieces and for those it refused to harden before; but the resin should be added with judgment, or the works will become too hard and brittle. The composition is useless when it has been constantly employed for about a month; the period depends, how¬ ever, on the extent to which it is used, and the trough should be thoroughly cleansed out before new mixture is placed in it. The following recipe is recommended: Twenty gallons of spermaceti oil; Twenty pounds of beef suet rendered ; One gallon of neat’s-foot oil; One pound of pitch ; Three pounds of black resin. These last two articles must be previously melted together, and then added to the other ingredients; when the whole must be heated in a proper iron vessel, with a close cover fitted to it, until 156 THE PRACTICAL METAL-WORKERS ASSISTANT. the moisture is entirely evaporated, and the composition will take fire on a flaming body being presented to its surface, but which must be instantly extinguished again by putting on the cover of the vessel. When the saws are wanted to be rather hard, but little of the grease is burned off; when milder, a larger portion; and for a spring temper, the whole is allowed to burn away. When the work is thick, or irregularly thick and thin, as in some springs, a second and third dose is burned off, to insure equality of temper at all parts alike. Gun-lock springs are sometimes literally fried in oil for a con¬ siderable time over a fire in an iron tray; the thick parts are then sure to be sufficiently reduced, and the thin parts do not become the more softened from the continuance of the blazing heat. Springs and saws appear to lose their elasticity, after hardening and tempering, from the reduction and friction they undergo in grinding and polishing. Towards the conclusion of the manufac¬ ture, the elasticity of the saw is restored principally by hammer¬ ing, and partly by heating it over a clear coke fire to a straw color: the tint is removed by very diluted muriatic acid, after which the saws are well washed in plain water and dried. Watch springs are hammered out of round steel w r ire, of suitable diameter, until they fill the gage for width, which at the same time insures equality of thickness; the holes are punched in their extremities, and they are trimmed on the edge with a smooth file; the springs are then tied up with binding-wire, in a loose open coil, and heated over a charcoal fire upon a perforated revolving plate, they are hardened in oil, and blazed off. The spring is now distended in a long metal frame, similar to that used for a saw blade, and ground and polished with emery and oil, between lead blocks; by this time its elasticity appears quite lost, and it may be bent in any direction; its elasticity is, how¬ ever, entirely restored by a subsequent hammering on a very bright anvil, which “puts the nature into the spring .” The coloring is done over a flat plate of iron, or hood, under which a little spirit-lamp is kept burning; the spring is continually drawn backwards and forwards, about two or three inches at a time, until it assumes the orange or deep blue tint throughout, ac¬ cording to the taste of the purchaser; by many the coloring is considered to be a matter of ornament, and not essential. The last process is to coil the spring into the spiral form, that it may enter the barrel in which it is to be contained; this is done by a tool with a small axis and winch handle, and does not require heat. The balance-springs of marine chronometers, wdiich are in the form of a screw, are wound into the square thread of a screw of the appropriate diameter and coarseness; the two ends of the spring are retained by side screws, and the whole is carefully en¬ veloped in platinum-foil, and tightly bound with wire. The mass is next heated in a piece of gun barrel closed at the one end, and HARDENING AND TEMPERING. 157 plunged into oil, which hardens the spring almost without discol oring it, owing to the exclusion of the air b} r the close platinum covering, which is now removed, and the spring is let down to the blue, before removal from the screwed block. The balance or hair-springs of common watches are frequently left soft; those of the best watches are hardened in the coil upon a plain cylinder, and are then curled into the spiral form between the edge of a blunt knife and the thumb, the same as in curling up a narrow ribbon of paper, or the filaments of an ostrich feather. Thirty-two hundred balance springs weigh about an ounce. The soft springs are worth 60 cents each ; the hardened and tempered springs, $1.26 each. This raises the value of the steel, originally less than four cents, to $2000 and $8000 respectively. But springs also include the heaviest examples of hardened steel works uncom¬ bined with iron : for example, bow-springs for all kind of vehicles, some intended for railway use, measure 3| feet long, and weigh 50 pounds each piece; two of these are used in combination; other single springs are 6 feet long, and weigh seventy pounds. The principle of these bow-springs will be immediately seen, by con¬ ceiving the common archery bow fixed horizontally with its cord upwards ; the body of the carriage being attached to the cord sways both perpendicularly and sideways with perfect freedom. In hardening them they are heated by being drawn backwards and forwards through an ordinary forge fire, built hollow, and they are immersed in a trough of plain water: in tempering them they are heated until the black red is just visible at night; by daylight the heat is denoted by its making a piece of wood sparkle when rubbed on the spring, which is then allowed to cool in the air. The metal is nine-sixteenths of an inch thick, and some consider five- eighths the limits to which steel will harden properly, that is suffi¬ ciently alike to serve as a spring; their elasticity is tested far beyond their intended range. Great diversity of opinion exists respecting the cause of elastic¬ ity in springs; by some it is referred to different states of elec¬ tricity ; by others the elasticity is considered to reside in the thin blue, oxidized surface, the removal of which is thought to destroy the elasticity, much in the same manner that the elasticity of a cane is greatly lost by stripping off its silicious rind. The elastic¬ ity of a thick spring is certainly much impaired by grinding off a small quantity of its exterior metal, which is harder than the inner portion; and perhaps thin springs sustain in the polishing a proportional loss, which is to them equally fatal. It has been stated that the bare removal of the blue tint from a pendulum spring, by its immersion in weak acid, caused the chronometer to lose nearly one minute each hour; a second and equal immersion scarcely caused any further loss. It is supposed springs get stronger, in a minute degree, during the first two or three years they are in use, from some atmospheric change; when the springs are coated with gold by the electrotype process, no 158 THE PRACTICAL METAL-WORKERS ASSISTANT. such change is observable, and the covering, although perfect, may be so thin as not to compensate for the loss of the blue oxidized surface. Less Common Examples of Hardening, and Precautionary Measures. —English writers are famous all over the world for dis¬ tributing between themselves and their friends the inventions and discoveries of the rest of mankind. One of the leading points of Jacob Perkins’s discovery is disposed of in an original manner in the following paragraph. I thought I was up to every mode in which they drag in their friends; but this mode is new to me. One of the most serious evils in hardening steel, especially in thick blocks, or those which are unequally thick and thin, is their liability to crack, from the sudden transition; and in reference to hardening razors, a case in point: Mr.-mentions it as the ob¬ servation and practice of one of his workmen, “that the charcoal fire should be made up with shavings of leather and upon being asked what good he supposed the leather could do, this workman replied, “that he could take upon him to say that he never had a razor crack in the hardening since he had used this method, though it was a frequent occurrence before.” When brittle substances crack in cooling, it always happens from the outside contracting and becoming too small to contain the interior parts. But it is known that hard steel occupies more space than when soft; and it may easily be inferred that the nearer the steel approaches to the state of iron, the less will be this in¬ crease of dimensions. If, then, we suppose a razor or any other piece of steel to be heated in an open fire with a current of air passing through it, the external part will, by the loss of carbon, become less steely than before ; and when the whole piece comes to be hardened, the inside will be too large for the external part, which will probably crack. But if the piece of steel be wrapped up in the cementing mixture, or if the fire itself contain animal coal, and is put together so as to operate in the manner of that mixture, the external part, instead of being degraded by this heat, will be more carbonated than the internal part, in consequence of which it will be so far from splitting or bursting during its cooling that it will be acted upon in a contrary direction, tending to render it more dense and solid. The cracking which so often occurs on the immersion of steel articles in water, does not appear to arise so much from any decar¬ bonization of the surface merely, as from the sudden condensation and contraction of a superficial portion of the metal, while the mass inside remains swelled with the heat, and probably expands for a moment, on the outside coming in contact with the water. The file-makers, to save their works from clinking or cracking partly through in hardening, draw the files through yeast, beer- grounds, or any sticky material, and then through a mixture of common salt and animal hoof roasted and pounded. This is cor¬ roborative of the above, as in the like manner it supplies a little HARDENING AND TEMPERING. 159 carbon to tbe outside, and also renders the steel somewhat harder and less disposed to crack ; the composition also renders the more important service of protecting the fine points of the teeth from being injured by the fire. An analogous method is now practised in hardening Murphy’s axletrees, which are of wrought-iron, with two pieces of steel welded into the lower side, where they rest upon the wheels and sustain the load. The work is heated in an open forge fire, quite in the ordinary way, and when it is removed, a mixture, principally the prussiate of potash, is laid upon the steel; the axletree is then immediately immersed in water, and additional water is allowed to fall upon it from a cistern. The steel is considered to become very materially harder for the treatment, and the iron around the same is also partially hardened. These are, in fact, applications of the case-hardening process which is usually applied to wrought-iron for giving it a steely ex¬ terior, as the name very properly implies. Occasionally, steel which hardens but imperfectly, either from an original defect in the material, or from its having become deteriorated by bad treat¬ ment, or too frequent passage through the fire, is submitted to the case-hardening process in the ordinary way, by inclosing the objects in iron boxes, as will be explained. Jacob Perkins’s admirable process of transfer engraving may be thus explained. A soft steel plate was first engraved with the re¬ quired subject in the most finished style of art, either by hand or mechanically, or the two combined, and the plate was then hard¬ ened. A decarbonized steel cylinder was next rolled over the hardened plate by powerful machinery until the engraved impres¬ sion appeared in relief, the hollow lines of the original becoming ridges upon the cylinder. The roller was reconverted to the con¬ dition of ordinary steel and hardened, after which it served for returning the impression to any number of decarbonized plates, every one of which became absolutely a counterpart of the original; and every plate, when hardened, would yield the enormous num¬ ber of 150,000 impressions without any perceptible difference between the first and the last. In the event of any accident occurring to the transfer roller, the original plate still existed, from which another or any required number of rollers could be made, and from these rollers any num¬ ber of new plates, all capable of producing as many impressions as above cited. The present practice at the Bank of England, introduced by the late Mr. John Oldham, and now under the superintendence of his son, Mr. Thomas Oldham, is to anneal at one time four cast-iron boxes, each containing from three to six steel plates, surrounded on all sides with fine charcoal mixed with an equal quantity of chalk and driven in hard. The reverberatory furnace employed has a circular cast-iron plate or bed upon which the four boxes are fastened by wedges, 160 THE PRACTICAL METAL-WORKER’S ASSISTANT. and as the plate revolves very slowly and continually by the steam- engine employed in working the printing-presses and other ma¬ chinery, the plates are exposed in the most equal manner to the heat, and when the proper temperature is attained all the apertures are carefully closed and luted, to extend the cooling over a space of at least forty-eight hours. The surfaces of the cylinders and plates are thus rendered ex¬ ceedingly soft, to the depth of about the 32d of an inch, “ so as to become more like lead than any thing else,” and thus much of their surfaces must be turned or planed off; the device is raised in the transfer-press upon the natural soft steel of the rollers, under a pressure of some tons, and these are hardened without any inten¬ tional application of the case-hardening process, as the simple steel is undoubtedly very superior in all respects to that which has been decarbonized and reconverted. The plates themselves are used in the soft state, as they then admit of reparation by the transfer rollers; and the process is found to be more economical, as the risk of warping is avoided, and they may be easily repaired. The dates and numbers are at present printed as a second process by letter-press printing, with the machines invented by the late Mr. Bramah, and which have been engraved and described in different books. In hardening engraved plates, rollers, dies, and similar works, it is of the greatest importance to preserve the surface unimpaired, and as steel is very liable to oxidation at the red heat if exposed to the air for even a few seconds, and which oxidized scale will in some cases nearly remove, or at any rate injure, the subject produced upon its surface, it is of great importance to conduct the heating and cooling with the most complete exclusion of the air. Mr. Thomas Oldham has, more recently, introduced a mode of proceeding which appears as near to perfection as possible, and by it, instead of the works acquiring the ordinary black and gray tints, and a minute roughness, like the surface of the finest emery paper, the steel comes out of the water as smooth to the touch as at first, and mottled with all the beautiful tints seen on case-hard¬ ened gun-locks. The method is simply as follows : The work to be hardened is inclosed in a wrought-iron box with a loose cover, a false bottom, and with three ears projecting from its surface about midway ; the steel is surrounded on all sides with car¬ bon from leather, driven in hard, and the cover and bottom are carefully luted with moist clay. Thus prepared, the case is placed in the vertical position, in a bridle fixed across a great tub, which is then filled with water almost to touch the false bottom of the case. The latter is now heated in the furnace as quickly as will allow the uniform penetration of the heat. When sufficiently hot, it is removed to its place in the hardening tub, the cover of the iron box is removed, and the neck or gudgeon of the cylinder is grasped, beneath the surface of the carbon, with a long pair of tongs, upon which a coupler is dropped to secure the HARDENING AND TEMPERING. 161 grasp. It only remains for the individual to hold the tongs with a glove whilst a smart tap of a hammer is given on their extremity ; this knocks out the false bottom of the case, and the cylinder and tongs are instantly immersed in the water; the tongs prevent the cylinder from falling on its side, and thus injuring its delicate but still hot surface. For square plates, a suitable frame is attached by four slight claws, and it is the frame which is seized by the tongs: the latter are sometimes held by a chain, which removes the risk of accident to the individual. In some cases, the work assumes a striated and mackled appearance, evident to the touch as well as the sight, and which is to be attributed to an imperfect manufacture of the steel. Mr. Oldham informs me that in the Paris Mint, the dies are in¬ closed in the soot of burnt wood; and that in the Royal mint the dies are hardened by a powerful jet of water. He also adds, that his workpeople have the impression that steel is reduced to its softest state by enclosure with lime and ox-gall. Various methods have been likewise attempted to prevent the distortions to which work is liable in the operation of hardening, but without any very advantageous results; for instance, it has been recommended to harden small cylindrical wires, by rolling them when heated between cold metallic surfaces to retain them perfectly straight. This might probably answer, but unfortunately cylindrical steel wires supply but a very insignificant portion of our wants. Another mode tried by Dr. Wollaston was to inclose the piece of steel in a tube filled with Newton’s fusible alloy, the whole to be heated to redness and plunged in cold water: the object was re¬ leased by immersion in boiling water, which melted the alloy, and the piece came out perfectly unaltered in form, and quite hard. This mode is too circuitous for common practice, and the reason why it is to be always successful is not very apparent. Is not this a base attempt to drag in Newton and Wollaston? To these men the English attribute every thing. Jacob Perkins was an American to whom all the credit is due. The two Oldhams were Irishmen, Brunei was a Frenchman, and Bramah was a German. Mr. Perkins resorted to a very simple practice with the view of lessening the distortion of his engraved steel plates by boiling the water in which they were to be hardened to drive off the air, and plunging them vertically; and as the plates were required to be tempered to a straw color, instead of allowing them to remain in the water until entirely cold, he removed them whilst the inside was still hot, and placed them on the top of a clear fire until the tallow with which they were rubbed, smoked; the plate was then returned to the water for a few moments, and so on alternately until they were quite cold, the surface never being allowed to exceed the tempering heat. From various observations, it appears on the whole to be the 11 162 THE PRACTICAL METAL-WORKER’S ASSISTANT. best in thick works thus to combine the hardening and tempering processes, instead of allowing the objects to become entirely cold, and then to reheat them for tempering. To ascertain the time when the plate should be first removed from the water, Mr. Perkins heated a piece of steel to the straw color, and dipped it into water to learn the sound it made; and when the hardened plate caused the same sound, it was considered to be cooled to the right degree, and was immediately withdrawn. I will conclude these numerous examples and remarks by one of a very curious, massive, and perfect kind, in which the hardening is sure to occur without loss of figure, unless the work break under the process. I refer to the locomotive wheels with hardened steel tires, which may be viewed as the most ponderous example of hardening, as the tires of the eight-foot wheels weigh about 10 cwt., and consist of about one-third steel, and there seems no reason why this diameter might not be greatly exceeded. The materials for the tires are first swaged separately, and then welded together under the heavy hammer at the steel-works, after which they are bent to the circle, welded, and turned to certain gages. The tire is now heated to redness in a circular furnace: during the time it is getting hot, the iron wheel, previously turned to the right diameter, is bolted down upon a face-plate; the tire ex¬ pands with the heat, and when at a cherry-red, it is dropped over the wheel, for which it was previously too small, and is also hastily bolted down to the surface plate, the whole load is quickly im¬ mersed by a swing crane into a tank of water about five feet deep, and hauled up and down until nearly cold; the steel tires are not afterwards tempered. The spokes are forged out of flat bars with T formed heads; these are arranged radially in the founder’s mould, whilst the cast- iron centre is poured around them: the ends of the T heads are then welded together to constitute the periphery of the wheel or inner tire, and little wedge-form pieces are inserted where there is any deficiency of iron. The wheel is then chucked on a lathe, bored, and turned on the edge, not cylindrically, but like the meeting of two cones, and about one quarter of an inch higher in the middle than on the two edges. The compound tire is turned to the corresponding form, and consequently larger within or under-cut, so that the shrinking secures the tire without the possibility of obliquity or derangement, and no rivets are required. It sometimes happens that the tire breaks in shrinking when by mismanagement the diameter of the wheel is in excess. HARDENING CAST AND WROUGHT-IRON. 163 CHAPTER X. HARDENING CAST AND WROUGHT-IRON. The similitude of chemical constitution between steel, which usually contains about one per cent, of carbon, and cast-iron that has from three to six or seven per cent., naturally leads to the expectation of some correspondence in their characters, and which is found to exist. Thus some kinds of cast-iron will harden almost like steel, but they generally require a higher temperature; and the majority of cast-iron, also like steel, assumes different degrees of hardness, according to the rapidity with which the pieces are allowed to cool. The casting left undisturbed in the mould, is softer than a similar one exposed to the air soon after it has been poured. Large castings cannot cool very hastily, and are seldom so hard as the small pieces, some of which are hardened like steel by the moisture combined with the moulding sand, and cannot be filed until they have been annealed after the manner of steel, which renders them soft and easy to be worked. Chilled iron-castings present as difficult a problem as the harden¬ ing and tempering of steel; the fact is simply this, that iron cast¬ ings, made in iron moulds under particular circumstances, become on their outer surfaces perfectly hard, and resist the file almost like hardened steel; the effect is however superficial, as the chilled exterior shows a distinct line of demarkation when the objects are broken. The production of chilled castings is always a matter of some uncertainty, and depends upon the united effect of several causes; the quality of the iron, the thickness of the casting, the tempera¬ ture of the iron at the time of pouring, and the condition or temperature of the iron mould, which has a greater effect in “ striking in” when the mould is heated than if quite cold: a very thin stratum of earthy matter will almost entirely obviate the chilling effect. A cold mould does not generally chill so readily as one heated nearly to the extent called “black-hot:” but the re¬ verse conditions occur with some cast-iron. The hard portion varies from less than one-sixteenth to more than one-fourth of an inch in thickness. There is this remarkable difference between cast-iron thus hard¬ ened, and steel hardened by plunging whilst hot into water; that whereas the latter is softened again by a dull red-heat, the chilled castings on the contrary are turned out of the moulds as soon as the metal is set, and are allowed to cool in the air; yet although the whole is at a bright red heat, no softening of the chilled part takes place. This material has been employed for punches for red- hot iron; the punches were fixed in cast-iron sockets, from which 164 THE PRACTICAL METAL-WORKER’S ASSISTANT. they only projected sufficiently to perforate the wheel tires in the formation of which they were used, and from retaining their hard¬ ness they were more efficient than those punches made of steel. Chilled castings are also commonly employed for axletree boxes, and naves of wheels, which are finished by grinding only; also for cylinders for rolling metal, for the heavy hammers and anvils or stithies for iron works, the stamp-heads for pounding metallic ores, etc. Cannon balls, as well as ploughshares, are examples of chilled castings; with balls the chilling is unimportant, and occurs alone from the method essential to giving the balls the required perfec¬ tion of form and size. Malleable iron-castings are at the opposite extreme of the scale, and are rendered externally soft by the abstraction of their carbon, whereby they are nearly reduced to the condition of pure malleable iron, but without the fibre which is due to the hammering and rolling employed at the forge. The malleable iron-castings are made from the rich iron, and are at first as brittle as glass or hardened steel; they are enclosed in iron boxes of suitable size, and surrounded with pounded iron¬ stone, or some of the metallic oxides, as the scales from the iron forge, or with common lime, and various other absorbents of carbon, used either together or separately. The cases, which are sometimes as large as barrels, are luted, rolled into the ovens or furnaces, and submitted to a good heat for about five days, and are then allowed to cool very gradually within the furnaces. The time and other circumstances determine the depth of the effect; thin pieces become malleable entirely through; they are then readily bent, and may be slightly forged; cast-iron nails and tacks thus treated admit of being clenched, thicker pieces retain a central portion of cast-iron, but in a softened state, and not brittle as at first; on sawing them through, the skin or coat of soft iron is perfectly distinct from the remainder. This mode is particularly useful for thin articles that can be more economically and correctly cast, than wrought at the forge, as bridle-bits, snuffers, parts of locks, culinary and other vessels, pokers and tongs, many of which are subsequently case-hardened and polished, as will be explained, but malleable cast-iron should never be used for cutting-tools. Case-Hardening Wrought and Cast-Iron. —The property of hardening is not possessed by pure malleable iron; but I have now to explain a rapid and partial process of cementation, by which wrought-iron is first converted exteriorly into steel, and is subse¬ quently hardened to that particular depth; leaving the central parts in their original condition of soft fibrous iron. The process is very consistently called case-hardening, and is of great import¬ ance in the mechanical arts, as the pieces combine the economy, strength, and internal flexibility of iron, with a thin casting of steel; which, although admirable as an armor of defence from wear or deterioration as regards the surface, is unfit for the formation of HARDENING CAST AND WROUGHT-IRON. 165 cutting edges or tools, owing to the entire absence of hammering, subsequent to the cementation with the carbon. Cast-iron obtains in like manner a coating of steel, which surrounds the peculiar shape the metal may have assumed in the iron-foundry and work¬ shop. The principal agents used for case-hardening are animal matters, as the hoofs, horns, bones, and skins of animals; these are nearly alike in chemical constitution; they are mostly charred and coarsely pounded; some persons also mix a little common salt with some of the above. The work should be surrounded on all sides with a layer from half an inch to one inch thick. The methods pursued by different individuals do not greatly differ; for example, the gunsmith inserts the iron work of the gun- lock, in a sheet-iron case in the midst of bone-dust (often not burned), the lid of the box is tied on with iron wire, and the joint is luted wth clay; it is then heated to redness as quickly as possible, and retained at that heat from half an hour to an hour, and the contents are quickly immersed in cold water. The objects sought are a steely exterior, and a clean surface covered with the pretty mottled tints, apparently caused by oxidation from the partial admission of air. Some of the malleable iron castings, such as snuffers, are case- hardened to admit of a better polish; it is usually done with burnt bone-dust, and at a dull red heat; they remain in the fire about two or three hours, and should be immersed in oil, as it does not render them quite so brittle as when plunged into water. It must be remembered they are sometimes changed throughout their sub¬ stance into an inferior kind of steel, by a process that should in such instances be called cementation, and not case-hardening, con¬ sequently they will not endure violence. The mechanician and engineer use horns, hoofs, bone-dust, and leather, and allow the period to extend from two to eight hours, most generally four or five; sometimes for its greater penetration, the process is repeated a second time with new carbonaceous materials. Some open the box and immerse the work in water direct from the furnace; others, with the view to preserve a better surface, allow the box to cool without being opened, and harden the pieces with the open fire as a subsequent operation; the carbon once added, the work may be annealed and hardened much the same as ordinary steel. When the case-hardening is required to terminate at any par¬ ticular part, as a shoulder, the object is left with a band or projec¬ tion, the work is allowed to cool without being immersed in water the band is turned off, and the work when hardened in the open fire is only affected so far as the original cemented surface remains. A new substance for the case-hardening process, but containing the same elements as those more commonly employed, has of late years been added, namely, the prussiate of potash (a salt consisting 166 THE PRACTICAL METAL-WORKER’S ASSISTANT. of two atoms of carbon and one of nitrogen), which is made from a variety of animal matters. It is a new application without any change of principle; the time occupied in this steelifying process is sometimes only min¬ utes instead of hours and days, as for example when iron is heated in the open fire to a dull red, and the prussiate is either sprinkled upon it or rubbed on in the lump, it is returned to the fire for a few minutes and immersed in water; but the process is then exceedingly superficial, and it may if needful be limited to any particular part upon which alone the prussiate is applied. The effect by many is thought to be partial or in spots, as if the salt refused to act uniformly; in the same manner that water only moistens a greasy surface in places. The prussiate of potash has been used for case-hardening the bearings of wrought-iron shafts, but this seems scarcely worth the doing. In the general way, the conversion of the iron into steel, by case-hardening, is quite superficial, and does not exceed the six¬ teenth of an inch; if made to extend to one-quarter or three-eighths of an inch in depth, to say the least it would be generally useless, as the object is to obtain durability of surface, with strength of in¬ terior, and this would disproportionately encroach on the strong iron within. The steel obtained in this adventitious manner is not equal in strength to that converted and hammered in the usual way, and if sent in so deeply, the provision for wear would far exceed that which is required. Let us compare the case-hardening process with the usual con¬ version of steel. The latter requires a period of about seven days, and a very pure carbon, namely, wood charcoal, of which a minute portion only is absorbed; and it being a simple body, when the access of air is prevented by the proper security of the troughs, the bulk of the charcoal remains unconsumed, and is reserved for future use, as it has undergone no change. The hasty and partial process of cementation is produced in a period commonly less than as many hours with the animal charcoal, or than as many minutes with the prussiate of potash; but all these are compound bodies (which contain cyanogen, a body consisting of carbon and nitrogen), and are never used a second time, but on the contrary the process is often repeated with another dose. It would be, therefore, an interesting inquiry for the chemist, as to whether the cyanogen is absorbed after the same manner as carbon in ordinary steel, or whether the nitrogen assists in any way in hastening the admission of the carbon, by some as yet untraced affinity or decomposition. It may happen that the carbon is not essential, as the Indian steel or wootz is stated to contain alumina, silex, and manganese. This hasty supposition will apply less easily to cast-iron, which contains from three to seven times as much carbon as steel, and although not always hardened by simple immersion, is constantly under the influence of the case-hardening process; unless we adopt APPLICATION OF IRON TO SHIP-BUILDING. 167 the supposition, that the carbon in cast-iron which is mixed with the metal in the shape of cinder in the blast furnace, when all is in a fluid state, is in a less refined union than that instilled in a more aeriform condition in the acts of cementation and case hardening. CHAPTER XI. ON THE APPLICATION OF IRON TO SHIP-BUILDING. There is probably no branch of industry in which the use of iron is more important than that of ship-building. The strength, ductility, and comparative lightness of this material are all in its favor; and, although much has been done in the application of iron to this important purpose, a great deal more remains to be accomplished. Vessels composed of iron plates have been employed for more than fifty years in the navigation of canals; but it is not more than twenty-five or twenty-six since they were first introduced as sea-going vessels. It is true that the late Mr. Aaron Manby pro¬ jected an iron vessel in 1820, which was built in the ensuing year, and early in 1822 was navigated by Captain (since Admiral Sir Charles) Napier from London to Havre, and on to Paris; this, however, was not a sea-going vessel, but an iron steamer con¬ structed for the Seine, and which for many years navigated that river between Paris and Rouen. From this period little appears to have been done in furtherance of the application of iron to the construction of ships till 1829-30, when the introduction of a new system of traction at high veloci¬ ties on canals led to new developments; and from this time to the present, iron, as a material for ship-building, has been extensively used, and is increasingly in demand. From 1829 to 1832, iron ship-building may be considered to have been experimental; and the trials conducted by Mr. Fairbairn on the Forth and Clyde Canal,* simultaneously with those of Mr. John and Mr. McGregor * Laird at Liverpool, led to a new era in the history of ship-building. Among the first iron vessels for sea-going purposes was one of small tonnage, built at Manchester for the Forth and Clyde Canal Company. She was built with paddle-wheels on the quarter near the stern, and propelled by two high-pressure engines of, collectively, 30 horse-power. This vessel attained great speed, considering the date at which she was built; and for many years traded between Grangemouth and the coast of Fife, round to Dundee. Previously to the building of the “ Manchester,” another small vessel, called the “ Lord Dundas,” was constructed for the same * Vide “Remarks on Canal Navigation,” by W. Fairbairn. Longman, 1831. 168 THE PRACTICAL METAL-WORKER’S ASSISTANT. company. She was strictly experimental, and was propelled by a locomotive engine of 16 horse-power, with 8-inch cylinders. Such was the lightness of her construction, that the plates were only l-14th of an inch thick, riveted to light T iron, which formed the ribs of the hull. This vessel had stern paddles, and was of the following dimensions:— Length, 68 feet. Breadth on beam, 11 feet 6 inches. Depth, 4 feet 6 inches. Diameter of paddle-wheel, 9 feet. Whole weight, including engine, paddle-wheel, etc., 7 tons 16 cwt. Draught of water with cargo on board, 16 inches. The “ Lord Dundas” was built in 1830, conveyed through the streets of Manchester on trucks, and launched into the Irwell, where numerous trials took place in regard to her speed in narrow channels, such as canals; including such other direct experiments as were likely to result from vessels of this kind propelled by steam. Subsequently to these trials she was navigated to Liver¬ pool, and from thence to Glasgow via the Isle of Man. As this voyage was rather a perilous one, when the slightness of the vessel’s build and the thinness of her sheathing-plates are considered, and as it was among the first—if, indeed, it were not the very first— which indicated the necessity of adjusting the compass in order to neutralize the local attraction of the material by which it was sur¬ rounded, we may probably be permitted to give a brief narrative of the circumstances as they occurred during the voyage. The "Lord Dundas” sailed from Liverpool at four a.m. on a fine morning in June, 1831, and steered direct for the floating-light. She made the light in good »time, notwithstanding a thick haze in the atmos¬ phere, which, during the forenoon, thickened into a dense fog. To¬ wards one o’clock land was descried upon the starboard bow, show¬ ing apparently that she had made considerable deviation in a west¬ erly direction. A dispute arose as to what land it was—one party contending that it was the western side of the Isle of Man ; the other, better acquainted with that side of the island, that it was « not. After a considerable contest and examination of the charts, it was at last discovered that the little vessel was on the north of Morecambe Bay, approaching the coast of Cumberland. On the discovery of this error, and in consequence of the frail bark show¬ ing symptoms of weakness, from the effects of the swell which was rolling in from the west, it was considered desirable to look out for shelter; and consequently her course was altered in the direc¬ tion of the Island of Peel Foundry, where she was sheltered for the night. On the following morning she crossed to Ramsey, where the question of the variation of the compass was investi¬ gated, and rectified by the simple process of nailing a block of iron to the deck, in the immediate vicinity of the compass—by this means neutralizing the local attraction of the iron by which APPLICATION OF IRON TO SHIP-BUILDING. 169 it was surrounded. After this, the remainder of the voyage from Ramsey to Greenock was effected in a direct course with perfect safety. We have noticed these circumstances as illustrating the imper feet state of our knowledge, as respects the influence of large masses of iron upon the ship’s compass. It has been ascertained that the angle-iron and T iron ribs, when carried above the deck so as to form part of the bulwarks, had a remarkable effect upon the compass, each of them forming, as it were, a separate magnet, whose influence, unless neutralized by some greater magnetic power, caused a considerable deviation of the needle, so that it indicated a point wide of the magnetic north; and as this deviation altered with every change of the position of the vessel, no reliance could be placed upon it. Captain Johnson and Professor Airey, by an in¬ teresting series of experiments, ultimately settled this question, and provided a remedy in the adjustment and correction of the compass on board iron ships. The object contemplated by this light vessel and light machinery was, to ascertain how far quick speeds could be attained upon canals by steam-power. As much as fourteen miles an hour had been accomplished by horses, with a tractive power of 352 lbs. by dyna¬ mometer, and that without the least appearance of surge;* but the experiments made with the “Lord Dundas” steamer indicated a very different law, and, under the most favorable circumstances, never exceeded more than eight to eight and a half miles an hour, and that with an enormous swell washing over the banks of the canal in every direction. In fact, the object for which the boat was built was never attained, and it was found impossible to effect by steam what was done by horses. It nevertheless led to a mor$ important and a greatly-enlarged branch of industry—namely, th< construction of iron vessels upon a large scale for ocean traffic. These experimental vessels, the “Lord Dundas” and the “Man¬ chester,” already mentioned, in conjunction with the “Alburka,” and some other vessels, by Messrs. J. Laird and Co., of Liverpool, may be considered as the first successful attempts in iron ship¬ building. Shortly after the completion of these vessels, several large establishments were founded for this branch of construction, amongst whom may be enumerated Messrs. W. Fairbairn and Co., Millwall, and Messrs. Ditchburn and Mare, Blackwall, London; Messrs. Laird and Co., Liverpool; Messrs. Tod and McGregor, G lasgow; and several others, all of whom were engaged for many years in the construction of iron ships. In this chapter we shall be unable to go much into detail, and must confine ourselves to a few general observations in connection with the more important application of iron as a material of con¬ struction for ocean steamers and sailing vessels, exposed to all the changes and vicissitudes of wind and tides in the open sea. * “ Remarks on Canal Navigation,” page 57. 170 THE PRACTICAL METAL-WORKER’S ASSISTANT. Fig. 108. Fig. 108 exhibits a half cross section of one of Her Majesty’s frigates of the second class, and will, to a certain extent, illustrate the principles of construc¬ tion. It will be seen that the iron-ship is composed of a series of frames or ribs, placed at various distances apart; these are connected together in the interior of the vessel by transverse beams, mostly of iron, but sometimes of wood, which support the decks. Over the exterior of the ribs the iron sheathing-plates are riveted, so as to form a continuous water-tight cov¬ ering over the entire ex¬ terior of the vessel. Ribs.— One of the ribs is shown at a a a, Fig. 108 ; and its section will be seen in Fig. 109, which is a longi¬ tudinal section through the line b b ; it consists of a vertical plate c, to which two angle-irons are riveted, one at the top and the other at the bottom. On the lower angle-iron the sheath- upper, interior plates, some of which in large vessels are riveted diagonally, so as to form stringers and braces from the keelsons round the bilge to the upper decks. These ribs are placed at dis- tances of about fifteen inches ing plates d are riveted; and on the Fig. 109. to eighteen inches apart, according Fig. HO. F 1 '-o La 1 4 JO > J to their position in the direc¬ tion of the length of the ship. 5 Other kinds of frames might be used with double f angle-iron, as shown at e e, ^ in the annexed sketch (Fig. 110), but they are more expensive; and from the increased complexity of construction, the extra strength obtained does not compensate for the difference of cost. Although the frames shown APPLICATION OF IRON TO SHIP-BUILDING. 171 in Fig. 109 have come into general use as the most effective and easy of construction. Keels.— This part of the vessel requires to be made exceedingly strong to resist the pressure or violent shocks to which it is sub¬ jected, when a vessel grounds. It is made in various ways, generally with a false keel, which is riveted on below the ribs by two angle-irons. The false keel is intended to receive the first shock in grounding; and is so arranged that it may even be carried away without material injury to the true keel. Fig. Ill shows a method in which it will be seen that the sheathing-plates a a are bent downwards so as to grasp the side of the keel, which consists of a massive plate of iron; whilst the angle-iron of the ribs is bent upwards at right angles, and is firmly riveted to the vertical keel plate. Fig. ill. Fig. 112. Decks. —The floorings are supported upon beams extending from one side of the vessel to the other, and attached at either end to the ribs or side frames. In the section, Fig. 108, the two upper decks are supported upon wooden beams, as in an ordinary wooden vessel; but wrought-iron beams may be sub¬ stituted for these with great advantage, as shown at g g. These deck-beams have been made of vari¬ ous forms, the best of which for large ves¬ sels is probably that shown in Fig. 112, which consists of angle irons riveted to the top and to the bottom of a thin vertical plate. In some cases a vertical plate, with w Jk Fig 113. two angle-irons at the top and one at the bottom, is used, and has 172 THE PRACTICAL METAL-WORKER’S ASSISTANT. the advantage of greater simplicity, though the material is not so well distributed. The box beam (Fig. 113) is employed for sup¬ porting the shafts and paddle-boxes of steamers, etc. Riveting of the Plates. —In all wrought-iron constructions, the mode of joining two plates together is the same. When the article can neither be produced at once from the rolling-mill nor the steam-hammer, and except in the comparatively few cases where parts are welded together, they are universally united by rivets. A series of holes being made through both pieces, a small bolt, with a head upon one side, is passed through each, and then quickly hammered down on the other side to another head, so as to grasp the parts tightly between them. These rivets are usually employed in a red-hot state, both because they are then more easily ham¬ mered down, and because in cooling they contract and draw the parts together with great force. Since the introduction of this process, the greatest improvement has been the substitution of the riveting-machine, invented by Mr. Fairbairn; by means of which the object is secured in consider¬ ably less time and at less cost, and which completes the union of the plates with much greater perfection than could possibly be done by the hand. But this new and very superior process has not as yet been successfully applied to the riveting of plates for ships. On comparing the strength of plates with their riveted joints, it will be necessary to examine the sectional areas taken in a line through the rivet-holes with the section of the plates themselves. It is perfectly obvious that in perforating a line of holes along the edge of a plate, we must reduce its strength; it is also clear that the plate so perforated will be to the plate itself, nearly as the areas of their respective sections, with a small deduction for the irregularities of the pressure of the rivets upon the plate; or, in other words, the joint will be reduced in strength somewhat more than in the ratio of its section through that line to the solid sec¬ tion of the plate. For example, suppose two plates, each two feet wide and three-eighths of an inch thick, to be riveted together with ten three-fourth inch rivets. It is evident that out of two feet, the length of the joint, the strength of the plates is reduced by per¬ foration to the extent of seven and a half inches; and here the strength of the plates will be to that of the joint as 9 : 6.187*, which is nearly the same as the respective areas of the solid plate and that through the rivet-holes; or as 24 : 16 - 5f. From these foots it is evident that the rivets cannot add to the strength of the plates, their object being to keep the two surfaces of the lap in contact. It may be said that the pressure or adhesion of the two surfaces of the plates would add to the strength; but this is not found to be the case to any great extent, as in almost every in¬ stance the experiments indicate the resistance to be in the ratio of their sectional areas. * The ratio of the areas. f The ratio of the breadth of metal APPLICATION - OF IRON - TO SHIP-BUILDING. 173 Fig. 114. oaoooaolol Fig. 115. C O O o qpoooi o ooo ooo When this great deterioration of strength at the joint is taken into account, it cannot but be of the greatest importance that in structures subjected to such violent strains as ships, the strongest method of riveting should be adopted. To ascertain this, a long series of experiments were undertaken by Mr. Fairbairn, some of the results of which will be of interest here. The joint ordinarily employed in ship-building is the lap- joint, shown in Figs. 114 and 115. The plates to be united are made to overlap, and the rivets are passed through them, no covering-plates being re¬ quired, except at the ends of the plate where they butt against each other. It is also a common practice to countersink the rivet-heads on the exterior of the vessel, that the hull may present a smooth surface for her passage through the water. This system of riveting is shown in Fig. Ill, where the rivets of the sheathing-plates are countersunk. This system of riveting is only used when smooth surfaces are required; under other circumstances their introduction would not be desirable, as they do not add to the strength of the joint, but to a certain ex¬ tent reduce it. This reduction is not observable in the experi¬ ments ; but the simple fact of sinking the head of the rivet into the plate, and cutting out a greater portion of metal, must of neces¬ sity lessen its strength, and render it weaker than the plain joint with raised heads. There are two kinds of lap-joints, those said to be single-riveted (Fig. 114) and those which are double-riveted (Fig. 115). At first the former were almost universally employed, but the greater strength of the latter has since, led to their general adoption in the larger descriptions of vessels. The reason of the superiority is evident. A riveted joint gives way either by shearing off the rivets in the middle of their length, or by tearing through one of the plates in the line of the rivets. In a perfect joint the rivets should be on the point of shearing just as the plates were about to tear- but in practice the rivets are usually made slightly too strong. Hence it is an established rule to employ a certain number of rivets per lineal foot. If these are placed in a single row, the rivet-holes so nearly approach each other that the strength of the plates is much reduced; but if they are arranged in two lines, a greater number may be used, and yet more space left between the holes, and greater strength and stiffness imparted to the plates at the joint. 174 THE PRACTICAL METAL-WORKER’S ASSISTANT. The results of Mr. Fairbairn’s experiments upon the two forms of joint are given in the following summary: Cohesive strength of plates. Breaking-weight in lbs. per sq. in. Strength of single-riveted joints of equal section to the plates, taken through the line of rivets. Breaking-weight in lbs. per sq. in. Strength of double-riveted joints of equal section to the plates, taken through the line of rivets. Breaking-weight in lbs. per sq. in. 57,724 45,743 52,352 61,579 36,606 48,821 58,322 43,141 58,286 50,983 43,515 54,594 51,130 40,249 53,879 49,281 44,715 53,879 43,805 37,161 47,062 Mean _ 52,486 41,590 53,635 The relative strengths will therefore be— For the plate.1000 Double-riveted joint. . . .1021 Single-riveted joint .... 791 From the above it will be seen that the single-riveted joints have lost one-fifth of the actual strength of the plates, whilst the double- riveted have retained their resisting powers unimpaired. These are important and convincing proofs of the superior value of the double joint; and in all cases where strength is required, this de¬ scription of joint should invariably be used. Comparing these results with those of a former analysis, we have— 1000 : 1021 and 791* 1000 : 933 and 731 Mean . . . 1000 : 977 and 761 which in practice we may safely assume as the correct value of each. Exclusive of this difference, we must, however, deduct thirty per cent, for the loss of metal actually punched out for the reception of the rivets; and the absolute strength of the plates will then be, to that of the riveted joints, as the numbers 100, 68, 46. In some cases, where the rivets are wider apart, the loss sustained is, how¬ ever, not so great; but in boilers and similar vessels where the rivets require to be close to each other, the edges of the plates are weakened to that extent. Taking into consideration the various circumstances affecting the experimental results, we may fairly * The cause of the increase of strength in the double-riveted plates may be attributed to the riveted specimens being made of best iron ; whereas the mean strength of the plates is taken from all the irons experimented upon, iome of inferior quality, which will account for the high value of the double- riveted joint. APPLICATION OF IRON TO SHIP-BUILDING. 175 assume the following relative strengths as the value of plates with their riveted joints. Taking the strength of the plate at.100 The strength of the riveted joint would then be . 70 And the strength of the single riveted joint . . 56 Wood and iron as materials for ship-building. — We shall consider this point under three heads — Strength, Durability, Economy. To ascertain the superiority of iron over wood in regard to strength, let us consider the strains to which a vessel is subjected. Let us take, for example, a vessel of similar dimensions to the “ Great Western” (the first steamer that successfully crossed the Atlantic), 212 feet long between the perpendiculars, 35 feet beam, and 23 feet from the surface of the main deck to the bottom of the sheathing attached to the keel. Now, considering a vessel of this Fig. 116. magnitude, with its machinery and cargo, to weigh 3000 tons, in¬ cluding her own weight; and supposing, in the first instance, that she is suspended upon two points, A and B, resting on the bow and stern, at a distance of 210 feet, as shown in Fig. 116 ; we should then have to calculate, from some formula yet to be determined by experiment, the ultimate strength of the ship. To determine this formula with accuracy is a work of research. In the meantime, we are fortunate in having before us that which applies with so much certainty to tubular bridges and tubular girders; and all that is required in this case will be to ascertain the correct sectional area of the plates, to prevent the tearing asun¬ der of the bottom, and the quantity of material necessary to resist the crushing force along the line of the upper-deck on the top. It is true that the necessary data have yet to be determined; but the iron ship-builder cannot be far wrong if he assumes the weight W in the middle (Fig. 116) to be equal to the united weights of the ship and cargo. This, in the case before us, would give 'an ultimate power of resistance of 3000 ton3 in the middle, or 6000 tons equally distributed along the ship, with her keel down¬ wards. Assuming these tests, or the calculation derived therefrom, to be correct, let us now bring the vessel into a totally different po- 176 THE PRACTICAL METAL-WORKER’S ASSISTANT. sition, as in Fig. 117, having the same weight of cargo on board, and supported by a wave, which, for the sake of illustration, we may consider as supporting the vessel upon a single point in the middle. Fig. 117. In this position we find the strain reversed; and in the place of the lower part of the hull of a ship being in a state of tension, it is, on the contrary, in a state of compression, and the whole of those parts below the neutral axis are subjected to that strain. On the other hand, the upper part is in a state of tension; and that tension, as well as the compressive strain below, will be found to vary in degree in the ratio of the distances from the centre of the neutral axis a (Fig. 117), round which the forces of tension and compression revolve. In this supposed position we may venture to calculate the strengths, in order to ascertain the limit or maxi¬ mum of security, and act as if the vessel were placed in trying circumstances,—either contending with the rolling seas of a hur¬ ricane, or suffering the actual suspension of either portion when taking the ground. In these critical positions, we arrive at the conclusion, that calculations founded upon the formula for wrought- iron tubular beams will determine the strength and resisting powers of an iron ship, and that under every contingency and every cir¬ cumstance in which the vessel can be placed. Moreover, it will give a wide margin of security under all those forms and con¬ ditions of peril to which every vessel navigating the ocean is exposed. We are fully aware that many thousand vessels are now afloat that would not stand one-third of the tests which we have taken; but that is no reason why we should not endeavor to effect more judicious distribution of the material, in order to attain the maximum strength, where human life and the fortunes of the public are at stake. To show that we have not selected tests which no vessel would stand, we append the following incidents: In hauling an iron steamer of nearly 400 tons burthen out of a temporary basin, she grounded on the extreme end of the bank, and was left, as the tide receded, with forty feet of her stern en¬ tirely without support, and her bow buried in the opposite bank. . On the return of the tide, the vessel floated, and immediately after¬ wards she proceeded on her voyage. A large steamer, the “ Vanguard,” ran foul of a reef of rocks on the west coast of Ireland, and continued exposed to the swell of the Atlantic beating her upon them for several days, with com- APPLICATION OF IRON TO SHIP-BUILDING. 177 paratively little injury, excepting only the corrugation of tlie plates along her bottom. She appears to Have rested upon a number of small hard rocks from the stem to the full part of the vessel just under the paddle-wheels, and from that part to the stern to have been quite unsupported, except at one place where the keel was broken. Mr. Clark, who went to examine her, states that “ although she was beating hard for so many days, no part of her engines was deranged. Her engines were kept constantly at work, and, in his opinion, are now in as permanent working order as ever they were. Had the ‘ Vanguard’ been built of wood instead of iron, she could not have been saved.” "The ‘Royal George,’ one of the iron steamers running between Liverpool and Glasgow—a vessel of unusual length in proportion to her beam—got on a rock near Greenock at high water, when loaded with about 150 tons of dead weight besides her engines and coals, and was left there high and dry during a whole tide without sustaining any injury. She rested nearly on her centre ; and all who saw her were of opinion that no timber vessel could have re¬ mained in that position without breaking her back.” * We might adduce numerous other instances in which iron ves¬ sels have, without material injury, stood the strains which must have caused a timber vessel to go to pieces. An iron ship is united by riveting into a single firm mass; whilst a wooden vessel is composed of an innumerable number of pieces, all imperfectly joined together, but which are, nevertheless, dependent on each other for support,—so that if any one gives way, the stability of all the rest is endangered. In his paper on iron as a material for ship-building, Mr. Fair bairn gives the following results of some experiments on the com¬ parative strength of wood and iron, when subjected to pressure from a blunt instrument placed at right angles to the surface of the plate. It will be seen that, in these experiments, an endeavor was made to place the material in circumstances similar to those mentioned above, where the vessel is beating upon hard and unequal ground. In these experiments, the wrought-iron plates were fastened upon a frame of cast-iron, one foot square inside, and one foot six inches outside. The sides of the plate, when hot, were twisted round the frame, to which they were firmly bolted. The force to burst it was applied in the centre by a bolt of iron, terminating in a hemisphere three inches in diameter. Summary of Results. In Experiment I., a plate one-fourth of an inch thick was burst by. In Experiment II., a plate one-fourth of an inch thick was burst by. lbs. 13,789 19,769 Mean : lbs. 16,779 * Grantham “ On Iron as a Material for Ship-Building.” 12 178 THE PRACTICAL METAL-WORKER’S ASSISTANT. In Experiment III., a plate half an inch thick was burst bj. In Experiment IV., a plate half an inch thick was burst by . . . . .. Here the strengths are as the depths, a half-inch plate requiring . double the weight to produce fracture that had previously burst a quarter-inch plate. The experiments on wood were made upon good English oak, of the same width as the iron plates. The specimens were laid upon solid planks twelve inches asunder, and by the same apparatus the rounded end of the three-inch pin was forced through them. Summary of Results. Strength of planks 3 inches thick .... u (f Q (C (( O • • • • U 11 (( u - 1-9 • • • • U H 1 1 U u - 1-2 • * • • Here the strength to resist crushing follows the ratio of the square of the depth, as is found to be the case in the transverse fracture of rectangular bodies of constant breadth and span. The experiments show conclusively the superiority of iron in ordinary cases. Durability. —The durability of iron ships is now established beyond a doubt; and it is generally admitted that they remain fit for service longer than those of timber. At first it was thought that the action of salt-water would cause a rapid oxidation, and very soon disable them; indeed, oxidation has' been the rock-ahead of every iron ship for the last twenty years. The evil has been ex¬ aggerated ; and there are instances of iron ships built twenty years ago, which are still in existence with no sensible appearance of cor¬ rosion or decay, and, what is of equal importance, without having required repairs, if we except a few coats of oil-paint, or the appli¬ cation of some other anti-corrosive substance to neutralize the effects of the sea-water. Nature, however, comes to our assistance in this, as in almost every other attempt in the constructive arts, and seems to confirm the proverb, “A bright sword never rusts;” for it is with iron ships as with iron rails—when in constant use there is little, if any, appearance of oxidation. Economy.— Mr. Grantham, in the work already quoted, comes to the conclusion that iron vessels are on the whole less expensive in construction than similar vessels of wood. But assuming that, when built in the best manner, they cost about the same, still, the iron ship has great advantages. The strength of iron is so great that we are enabled to use a much thinner shell than with wood; and hence there is much more stowage room. The cost of main¬ taining an iron vessel, repairs, etc., are very small; whilst in a tint* lbs. 18,941 16,925 4,532 ) 4,280 f Mean : lbs. 17,933 4,406 lbs. Mean : lbs. 37,5i9 | 37>723 37,928 J METALS AND ALLOYS. 179 ber vessel they amount to a large sum. Iron vessels are not sub¬ ject to a dry rot; and we have already seen that they will remain under severe strain comparatively uninjured, when a timber vessel would go to pieces. It is necessary here to advert to the use of iron as applied to vessels of war. There cannot exist a doubt as to the advantages to be derived from iron as a material for ship-building, and it is as desirable in the navy as in the merchant service; but the great draw¬ back to its application is the effect of shot upon iron plates, and the consequent danger to the vessel if not regularly “ armored,” but merely constructed of iron like a merchantman. This danger does not arise so much from point-blank shot entering the ship at high velocities, as from shot ranging from a distance, and which strike the vessel with a reduced force. In the first case the shot penetrates and passes through the plates, making a perforation equal in diameter to the shot; but a half-spent shot when it arrives, not only pene¬ trates the side of the ship, but tears up the plates to a distance of some feet on every side. It is from this that the chief danger is to be apprehended. It is useless here to point out that which is now so very apparent to all well informed persons, that the successful application of iron in the building of powerful vessels of war, dur¬ ing the present contest in the United States—eventful in so very many respects—has opened a new era in ocean warfare. So great is this revolution, that the navies of the old world are now rendered comparatively harmless and consequently useless; and the United States, with her "New Ironsides,” “Dunderberg,” “Dictator,” “Puri¬ tan,” “ Roanoke,” and other iron-clads, is to-day not only the first military, but the first naval power in the world. CHAPTER XII. THE METALS AND ALLOYS MOST COMMONLY USED. We have now to consider the following metals: Antimony, Bis¬ muth, Copper, Gold, Lead, Mercury, Nickel, Palladium, Platinum, Rhodium, Silver, Tin, and Zinc. Unlike iron and steel, they do not admit of being hardened beyond that degree which may be produced by simple mechanical means, such as hammering, rolling, etc., neither (with the exception of platinum) do they submit to the process of welding. On the other hand, their fusibility offers an easy means of unit¬ ing and combining many of these metals with great readiness, either singly, or in mixtures of two or several kinds, which are called alloys. By the process of founding, any required form may 180 THE PRACTICAL METAL-WORKER’S ASSISTANT. be given to the fusible metals and alloys : their malleability and ductility are also turned to most useful and varied account; and by partial fusion neighboring metallic surfaces may be united, sometimes per se, but more generally by the interposition of a still more fusible metal or alloy called solder. The author intends therefore to commence with a brief notice of the physical characters and principal uses of the thirteen metals before named, and of their more important alloys. Tables of the cohesive force and of the general properties of metals will be next added to avoid the occasional necessity for reference to other works. These tables will be followed by some remarks on alloys, which as regards their utility in the arts, may be almost considered as so many distinct metals; this will naturally lead to the processes of melting, mixing and casting the metals ; a general notice and ex¬ planation of many works, taking their origin in the malleable and ductile properties, will then follow; and the consideration of the metals, and of materials from the three kingdoms, will be con¬ cluded by a descriptive account of the modes of soldering. DESCRIPTION OF THE PHYSICAL CHARACTER AND USES OF THE METALS AND ALLOYS COMMONLY EMPLOYED IN THE MECHANICAL AND USEFUL ARTS. ANTIMONY is of a silvery white color, brittle and crystalline in its ordinary texture. It fuses at about 800°, or at a dull red heat, and is volatile at a white heat. Its specific gravity is 6.712. Antimony expands on cooling; it is scarcely used alone, except in combination with similar bars of other metals for producing thermo-electricity: but antimony, which in the metallic state is frequently called “ regulus,” is generally combined with a large portion of lead, and sometimes with tin, and other metals. See Lead and Tin. “ Antimony and tin, mixed in equal proportions, form a moderately hard, brittle, and very brilliant alloy, capable of receiving an exquisite polish, and not easily tarnished by exposure to the air ; it has been occasionally manufactured into speculums for telescopes. Its s. g. is less than the mean of its constituent parts.” METALS AND ALLOYS. 181 BISMUTH is a brittle white metal with a slight tint of red: its specific gravity is 9.822. It fuses at 476° to 507°, and always crystallizes on cooling. According to Chaudet, pure bismuth is somewhat flexible. A cast bar of the metal, one-tenth of an inch diameter, supports, according to Mus- chenbroeck, a weight of forty-eight-pounds. Bismuth is volatile at a high heat, may be distilled in close vessels. It transmits heat more slowly than most other metals, perhaps in consequence of its texture. Bismuth is scarcely used alone, but it is employed for imparting fusibility to alloys, thus: 8 bismuth, 5 lead, 3 tin, constitute a fusible alloy, which melts at 212° F. 2 bismuth, 1 lead, 1 tin, a fusible alloy, which melts at 201° F. 5 bismuth, 3 lead, 2 tin, when combined melt at 199°. 8 bismuth, 5 lead, 4 tin, 1 type metal, constitute the fusi¬ ble alloy used on the Continent for producing the beautiful casts of the French medals, by the clichee process. The metals should be repeatedly melted and poured into drops until they are well mixed. 1 bismuth, and 2 tin, make an alloy found to be the most suitable for rose-engine and eccentric-turned patterns, to be printed from after the manner of letter-press. The thin plates are cast upon a cold surface of metal or stone, upon which a piece of smooth paper is placed, and then a metal ring; the alloy should neither burr nor crumble; if proper, it turns soft and silky; when too crystalline, more tin should be added. 2 bismuth, 4 lead, 3 tin, ) cons ^ u ^ e pewterers’ soft solders. 1 bismuth, 1 lead, 2 tin, j r All these alloys must be cooled quickly to avoid the sep¬ aration of the bismuth; they are rendered more fusible by a small addition of mercury. COPPER, with the exception of titanium, is the only metal which has a red color; it has much lustre, is very malleable and ductile, and exhales a peculiar smell when warmed or rub¬ bed. It melts at a bright-red or dull white heat at a tem¬ perature intermediate between the fusing points of silver and gold=1996° Fahr. Its specific gravity varies from 8.86 to 8.89 ; the former being the least density of cast copper, the latter the greatest of rolled or hammered copper. Copper is used alone for many important purposes, and very extensively for the following: namely, sheathing and bolts for ships, brewing, distilling, and culinary vessels. Some of the fire boxes for locomotive engines, boilers for marine engines, rollers for calico-printing and paper-mak¬ ing, plates for the use of engravers, etc. 182 THE PRACTICAL METAL-WORKER’S ASSISTANT. Copper is used in alloying gold and silver, for coin, plate, etc., and it enters with zinc and nickel into the composition of German silver. Copper alloyed with one-tenth of its weight of arsenic is so similar in appearance to silver, as to have been substituted for it. The alloys of copper, which are very numerous and im¬ portant, are principally included under the general name, Brass. In the more common acceptation, brass means the yellow alloy of copper, with about half its weight of zinc ; this is often called by engineers “ yellow brass.” Copper alloyed with about one-ninth its weight of tin, is the metal of brass ordnance, which is very generally called gun-metal; similar alloys used for the “ brasses” or bearings of machinery, are called by engineers, hard brass, and also gun-metal; and such alloys when employed for statues and medals are called bronze. The further addition of tin leads to bell metal, and speculum metal, which are named after their respective uses; and when the proportion of copper is exceedingly small the alloy constitutes one kind of pewter. Copper, when alloyed with nearly half its weight of lead, forms an inferior alloy, resembling gun-metal in color, but very much softer and cheaper, lead being only about one- fourth the value of tin, and used in much larger propor¬ tion. This inferior alloy is called pot-metal, and also cock- metal, because it is used for large vessels and measures, for the large taps or cocks for brewers, dyers and distillers, and those of smaller kinds for household use. Generally, the copper is only alloyed with one of the metals, zinc, tin, or lead; occasionally with two, and some¬ times with the three in various proportions. In many cases, the new metals are carefully weighed according to the quali¬ ties desired in the alloy, but random mixtures more fre¬ quently occur, from the ordinary practice of filling the crucible in great part with various pieces of old metal, of unknown proportions, and adding a certain quantity of new metal to bring it up to the color and hardness required. This is not done solely from motives of economy, but also from an impression which appears to be very generally entertained, that such mixtures are more homogeneous than those composed entirely of new metals, fused together for the first time. The remarks I have to offer on these copper alloys will be arranged in the tabular form, in four groups; and to make them as practical as possible, they will be stated in the terms commonly used in the brass-foundry. Thus, when the founder is asked the usual proportions of yellow brass, he will say, 6 to 8 oz. of zinc (to every pound of copper being implied). In speaking of gun-metal, he METALS AND ALLOTS. 183 wou d not say, it liad one-ninth, or 11 per cent, of tin, but simply that it was 1J, 2, or oz. (of tin), as the case might be ; so that the quantity and kind of the alloy, or the addi¬ tion to the pound of copper, is usually alone named: and to associate the various ways of stating these proportions, many are transcribed in the forms in which they are else¬ where designated. Alloys of Copper and Zinc only. The marginal numbers denote the ounces of zinc added to every pound of copper. I to | oz. Castings are seldom made of pure copper, as under ordinary circumstances it does not cast soundly; about half an ounce of zinc is usually added, frequently in the shape of 4 oz. of brass to every pound of copper; and by others 4 oz. of brass are added to every two or three pounds of copper. 1 to 1J oz. Gilding metal, for common jewelry: it is made by mixing 4 parts of copper with 1 of calamine brass; or sometimes 1 lb. of copper with 6 oz. of brass. The sheet gilding-metal will be found to match pretty well in color with the cast gun-metal, which latter does not admit of being rolled; they may be therefore used together when required. 3 oz. Bed sheet brass, made at Hegermuhl, or 5| parts copper, 1 zinc. 3 to 4 oz. Bath metal, pinchbeck, Mannheim gold, similor, and alloys bearing various names, and resembling inferior jewel¬ er’s gold greatly alloyed with copper, are of about this pro¬ portion : some of them contain a little tin; now, however, they are scarcely used. 6 oz. Brass, that bears soldering well. 6 oz. Bristol brass is said to be of this proportion. 8 oz. Ordinary brass, the general proportion; less fit for solder¬ ing than 6 oz., it being more fusible. 8 oz. Is generally the ingot brass, made by simple fusion of the two metals. 9 oz. This proportion is the one extreme of Muntz’s patent sheathing. See 10§. lOf oz. Muntz’s metal, or 40 zinc and 60 copper. “ Any propor¬ tions,” says the patentee, “ between the extremes, 50 zinc and 50 copper, and 37 zinc 63 copper, will roll and work at the red-heatbut the first-named proportion, or 40 zinc to 60 copper is preferred. The metal is cast into ingots, heated to a red-heat, and rolled and worked at that heat into ships’ bolts and other fastenings and sheathing. 12 oz. Spelter-solder for copper and iron is sometimes made in this proportion; for brass work, the metals are generally mixed in equal parts. See 16 oz. 184 THE PRACTICAL METAL-WORKER’S ASSISTANT. 12 oz. Pale yellow metal, fit for dipping in acids, is often made in this proportion. 16 oz. Soft spelter-solder, suitable for ordinary brass work, is made of equal parts of copper and zinc. About 14 lbs. of each are melted together and poured into an ingot mould with cross ribs, which indents it into little squares of about 2 lbs. weight; much of the zinc is lost. These lumps are afterwards heated nearly to redness upon a charcoal fire, and are broken up one at a time with great rapidity on an anvil or in an iron pestle and mortar. The heat is a critical point; if too great, the solder is beaten into a cake or coarse lumps and becomes tarnished; when the heat is proper, it i3 nicely granulated, and remains of a bright yellow color; it is afterwards passed through a sieve. Of course the ultimate proportion is less than 16 oz. of zinc. 16 oz. Equal parts is the one extreme of Muntz’s patent sheath¬ ing. See lOf. 161 oz. Mosaic gold, which is dark-colored when first cast, but on dipping assumes a beautiful golden tint. When cooled and broken, all yellowness must cease, and the tinge vary from reddish fawn or salmon color, to a light purple or lilac, and from that to whiteness. The proportions are stated as from 52 to 58 zinc to 50 of copper, or 16J to 17 oz. to the pound. 82 oz. or 2 zinc to 1 copper, a bluish-white, brittle alloy, very brilliant, and so crystalline that it may be pounded cold in a mortar. 128 oz. or two ounces of copper to every pound of zinc; a hard crystalline metal differing but little from zinc, but more tena¬ cious ; it has been used for laps or polishing disks. Remarks on the Alloys of Copper and Zinc. These metals seem to mix in all proportions. The addition of zinc continually increases the fusibility, but from the extremely volatile nature of zinc, these alloys cannot be arrived at with very strict regard to proportion. The red color of copper slides into that of yellow brass at about 4 or 5 oz. to the pound, and remains little altered unto about 8 or 10 oz.; after this it becomes whiter, and when 32 oz. of zinc are added to 16 of copper, the mixture has the brilliant silvery color of speculum metal, but with a bluish tint. These alloys, from about 8 to 16 oz. to the pound of copper, are extensively used for dipping, as in an enormous variety of furniture work; in all cases the metal is annealed before the application of the scouring or cleaning processes, and of the acids, bronzes and lackers subsequently used. The alloys with zinc retain their malleability and ductility well, unto about 8 or 10 ounces to the pound; after this, the crystalline character slowly begins to prevail. The alloy of METALS AND ALLOYS. 185 2 zinc and 1 copper, before named, may be crumbled in a mortar when cold. The ordinary range of good yellow brass, that files and turns well, is from about 4| to 9 oz. to the pound. With additional zinc, it is harder and more crystalline; with less, more tenacious, and it hangs to the file like copper; the range is wide, and small differences are not perceived. Alloys of Copper and Tin only. The marginal numbers denote the ounces of tin added to every pound of copper. Ancient Copper and Tin Alloys. Ancient bronze nails, flexible, or 20 copper, 1 tin. According to Pliny, as quoted Soft bronze, or . . 9 to 1 | oz. If oz. 2 oz. 2f oz. Medium bronze, or 8 to 1 Hard bronze, or . 7 to 1 6 to 8 oz. Ancient mirrors. by Wilkinson. Ancient weapons and tools, by various analyses, or 8 to 15 per cent, tin; metals from 8 to 12 per cent, tin, with two parts zinc added to each 100, for _ improving the bronze color. Modern Copper and Tin Alloys. 1 oz. Soft gun metal, that bears drifting, or stretching from a perforation. 1^- oz. A little harder alloy, fit for mathematical instruments ; or 12 copper and 1 very pure grain tin. 1| oz. Still harder, fit for wheels to be cut with teeth. 1| to 2 oz. Brass ordnance, or 8 to 12 per cent, tin; but the gen¬ eral proportion is one-ninth part of tin. 2 oz. Hard bearings for machinery. 2| oz. Very hard bearings for machinery. By Muschenbroek’s Tables it appears that the proportion 1 tin and 6 copper is the most tenacious alloy; it is too brittle for general use, and contains 2f oz. to the pound of copper. 3 oz. Soft musical bells. 3J oz. Chinese gongs and cymbals, or 20 per cent. tin. 4 oz. House bells. 4J oz. Large bells. 5 oz. Largest bells. 7f to 8f oz. Speculum metal. Sometimes one ounce of brass is added to every pound as the means of introducing a trifling quantity of zinc, at other times small proportions of silver are added; the employment of arsenic is by some recom¬ mended. The object agreed upon by all experimentalists appears to be the exact saturation of the copper with the tin, and the proportionate quantities differ very materially (in this 186 THE PRACTICAL METAL-WORKER’S ASSISTANT. and all other alloys ), according to the respective degrees of purity of the metals: for the most perfect alloys to this group, Swedish copper, and grain tin, should be used. When the copper is in excess, it imparts a red tint easily detected; when the tin is in excess, the fracture is granu¬ lated and also less white. The practice is to pour the melted tin into the fluid copper when it is at the lowest temperature that a mixture by stirring can be effected, then to pour the mixture into an ingot and to complete the com¬ bination by remelting in the most gradual manner, by put¬ ting the metal into the furnace as soon almost as the fire is lighted: trial is made of a little piece taken from the pot immediately prior to pouring. 82 oz. of tin to one pound of copper, makes the alloy called by the pewterers “ temper which is added in small quantities to tin, for some kinds of pewter, called “ tin and temper in which the copper is much less than 1 per cent. Remarks on the Alloys of Copper and Tin only. These metals seem to mix in all proportions. The addition of tin continually increases the fusibility, although when it is added cold it is apt to make the copper pasty, or even to set in a solid lump in the crucible. The red color of the copper is not greatly impaired in those proportions used by the engineer, namely, up to about 21 ounces to the pound; it becomes grayish white at 6, the limit suitable for bells, and quite white at about 8, the speculum metal; after this, the alloy becomes of a bluish cast. The tin alloy is scarcely malleable at 2 ounces, and soon becomes very hard, brittle, and sonorous; and when it has ceased to serve for producing sound, it is employed for reflecting light. The tough tenacious character of copper under the tools rapidly gives way ; alloys of 1| cut easily, 2 J assume about the maximum hardness without being crystalline ; after this they yield to the file by crumbling in fragments rather than by ordinary abrasion in shreds, until the tin very greatly predominates, as in the pewters, when the alloys become the more flexible, soft, malleable, £nd ductile, the less copper they contain. Alloys of Copper and Lead only. Tho marginal numbers denote the ounces of load added to every pound of copper. 2 oz A red-colored and ductile alloy. 4 oz. Less red and ductile ; neither of these is so much used as the following, as the object is to employ as much lead as possible METALS AND ALLOYS. 187 6 oz. Ordinary pot-metal, called dry pot-metal, as this quantity of lead will be taken np without separating on cooling; this is brittle when warmed. 7 oz. This alloy is rather short, or disposed to break. 8 oz. Inferior pot-metal, called wet pot-metal, as the lead partly oozes out in cooling, especially when the new metals are mixed; it is therefore always usual to fill the crucible in part with old metal, and to add new for the remainder. This alloy is very brittle when slightly warmed. More lead can scarcely be used, as it separates on cooling. Remarks on the Alloys of Copper and Lead only. These metals mix in all proportions until the lead amounts to nearly half, after this they separate in cooling. The addition of lead greatly increases the fusibility. The red color of copper is soon deadened by the lead; at about 4 ounces to the pound the work has a bluish leaden hue when first turned, but changes in an hour or so to that of a dull gun-metal character. When the lead does not exceed about 4 oz. the mixture is tolerably malleable, but with more lead it soon becomes very brittle and rotten: the alloy is greatly inferior to gun- metal, and is principally used on account of the cheapness of the mixture, and the facility with which it is turned and filed. Alloys of Copper, Zinc, Tin, and Lead, etc. This group refers principally to gun-metal alloys, to which more or less zinc is added by many engineers. The quantity of tin in every pound of the alloy, which is expressed by the marginal numbers, principally determines the hardness. M. Keller’s statues at Versailles are found, as the mean of four analyses, to consist of: Copper . . . . 91.40 or about 14f ounces. Zinc.5.53 “ 1 ounce. Tin.1.70 “ Of “ Lead.1.37 “ Of “ In 100 parts or the 16 ounces. If to 2f oz. tin to 1 lb. copper used for bronze medals, or 8 to 15 per cent, tin, with the addition of 2 parts in each 100 of zinc, to improve the color. The modern so-called bronze medals of our Mint are of pure copper, and are afterwards bronzed superficially. If oz. tin, f zinc to 16 oz. copper. Pumps and works requiring great tenacity. 188 THE PRACTICAL METAL-WORKER’S ASSISTANT. 1| oz. tin, 2 oz. brass, 16 oz. copper '( For wheels to be cut into if “ 2 " 16 “ j teeth. 2 “ 1| “ 16 “ For turning work. 21 “ 1| “ 16 “ For nuts of coarse threads and bearings. The engineer who uses these five alloys recommends melting the copper alone ; the small quantity of brass is then melted in another crucible, and the tin in a ladle,—the two latter are added to the copper when it has been removed from the furnace. The whole are stirred together and poured into the moulds without being run into ingots. The real quantity of tin to every pound of copper is about one- eighth oz. less than the number stated, owing to the addition of the brass, which increases the proportion of copper. If oz. tin, If oz. zinc, to 1 lb. copper. This alloy, which is a tough, yellow, brassy, gun-metal, is used for general purposes. It is made by mixing If lb. tin, If lb. zinc, and 10 lbs. of copper. The alloy is first run into ingots. 21 oz. tin, f oz. zinc, to 1 lb. copper. Used for bearings to sustain great weights. 21 oz. tin, 2f oz. zinc, to 1 lb. copper, were mixed by Chantrey, and a razor was made from the alloy. It proved nearly as hard as tempered steel, and exceedingly destructive to new files, and none others would touch it. 1 oz. tin, 2 oz. zinc, 16 oz. brass. Best hard white metal for buttons. f oz. tin, If oz. zinc, 16 oz. brass. Common white metal for buttons. 1.0 lbs. tin, 6 lbs. copper, 4 lbs. brass, constitute white solder. The copper and brass are first melted together, the tin is added, and the whole stirred and poured through birch twigs into water to granulate it; it is afterwards dried and pulverized cold in an iron pestle and mortar. This white solder was introduced as a substitute for silver solder in making gilt buttons. Another button solder consists of 10 parts cop¬ per, 8 of brass, and 12 of spelter or zinc. Remarks on Alloys of Copper, Zinc, Tin, and Lead, etc. Ordinary Yellow Brass (copper and zinc) is rendered very sensibly harder, so as not to require to be hammered, by a small addition of tin, say £ or f oz. to the lb. On the other hand by the addition of J to f oz. of lead, it becomes more malleable, and casts more sharply. Brass becomes a little whiter for the tin, and redder for the lead. The ad¬ dition of nickel to copper and zinc constitutes the so-called German silver. Gun Metal (copper and tin) very commonly receives a small addition of zinc; this makes the alloy mix better, and METALS AND ALLOYS. 189 to lean to the character of brass by increasing the mallea¬ bility without materially reducing the hardness. The zinc, which is sometimes added in the form of brass, also im¬ proves the color of the alloy both in the recent and bronzed states. Lead in small quantity improves the ductility of gun-metal, but at the expense of its hardness and color; it is seldom added. Nickel has been proposed as an addition to gun-metal by O’Donovan, of Dublin, and antimony by his countryman, Dr. Ure. Pot Metal (copper and lead) is improved by the addition of tin, and the three metals will mix in almost any pro¬ portions. When the tin predominates, the alloy so much the more nearly approaches the condition of gun-metal. Zinc may be added to pot metal in very small quantity, but when the zinc becomes a considerable amount, the copper takes up the zinc, forming a kind of brass, and leaves the lead at liberty, and which in great measure separates in cooling. Zinc and lead are also very indisposed to mix alone, although a little arsenic assists their union by “ kill¬ ing” the lead, as in shot metal. Antimony also facilitates the combination of pot metal; 7 lead, 1 antimony, and 16 copper, mixed perfectly well the first fusion, and the alloy was decidedly harder than 4 lead and 16 copper, and ap¬ parently a better metal. “ Lead and antimony, though in small quantity, have a remarkable effect in diminishing the elasticity and sonorousness of the copper alloys.” GOLD is of a deep and peculiar yellow color. It melts at a bright red heat, equivalent to 2016° of Fahrenheit’s scale, and when in fusion appears of a brilliant greenish color. Its specific gravity is 19.3. It is so malleable that it may be extended into leaves which do not exceed the one two hundred and eighty-two thousandth of an inch in thickness, or a single grain may be extended over 56 square inches of surface. This extensibility of the metal is well illustrated by gilt buttons, 144 of which are gilt by 5 grains of gold, and less than even half that quantity is adequate to giving them a very thin coating. It is also so ductile that a grain may be drawn out into 500 feet of wire. The pure acids have no action upon gold. Gold in the pure or fine state is not employed in bulk for many purposes in the arts, as it is then too soft to be durable. The gold foil used by dentists for stopping decayed teeth is perhaps as nearly pure as the metal can be obtained; it contains about 6 grains of alloy in the pound troy, or the one-thousandth part. Every superficial inch of this gold foil or leaf weighs f of a grain, and is 42 times as thick as the leaf used for gilding. The wire for gold lace prepared by the refiners for gold- lace manufacturers, requires equally fine gold, as when alloyed 190 THE PRACTICAL METAL-WORKER’S ASSISTANT. it does not so well retain its brilliancy. The gold in the proportion of about 100 grains to the pound troy of silver, or of 140 grains for double-gilt wire, is beaten into sheets as thin as paper; it is then burnished upon a stout red-hot silver bar, the surface of which has been scraped perfectly clean. When extended by drawing, the gold still bearing the same relation as to quantity, namely, the 57th part of the weight becomes of only one-third the thickness of or¬ dinary gold-leaf used for gilding. In water-gilding, fine gold is amalgamated with mercury, and washed over the gild- metal (copper and tin), the mercury attaches itself to the metal, and when evaporated by heat it leaves the gold behind in the dead or frosted state: it is brightened with the burn¬ isher. By the electrotype process a still thinner covering of pure gold may be deposited on silver, steel, and other metals. French watch-makers introduced this method of protecting the steel pendulum springs of marine chronometers and other time-pieces from rust. Fine gold is also used for soldering chemical vessels made of platinum. Gold Alloys. Gold-leaf for gilding contains from 8 to 12 grains of alloy to the oz., but generally 6 grains. The gold used by re¬ spectable dentists, for plates, is nearly pure, but necessarily contains about 6 grains copper in the oz. troy, or one 80th part; others use gold containing upwards of one-third of alloy; the copper is then very injurious. With copper, gold forms a ductile alloy of a deeper color, harder and more fusible than pure gold; this alloy, in the proportion of 11 of gold to 1 of copper, constitutes English standard gold; its density is 17.157, being a little below the mean, so that the metals slightly expand on combining. One troy pound of this alloy is coined into 46fg English sovereigns, or 20 troy pounds into 934 sovereigns and a half. (The pound was formerly coined into 44 guineas and a half). The standard gold of France consists of 9 parts of gold and 1 of copper. For Gold Plate the French have three different standards: 92 parts gold, 8 copper; also 84 gold, 16 copper; and 75 gold, 25 copper. In England, the purity of gold is expressed by the terms 22, 18, 16, 12, 8, carats, etc. The pound troy is supposed to be divided into 24 parts, and the gold, if it could be ob¬ tained perfectly pure, might be called 24 carats fine. The “ Old Standard Gold,” or that of the present British currency, is called fine, there being 22 parts of pure gold to 2 of copper. METALS AND ALLOYS. 191 The “New Standard,” for watch-cases, etc. is 18 carats of fine gold, and 6 of alloy. No gold of inferior quality to 18 carats, or the “New Standard,” can receive the Hall mark; and gold of lower quality is generally described by its com¬ mercial value. The alloy may be entirely silver, which will give a green color, or entirely copper for a red color, but the copper and silver are more usually mixed in the one alloy according to the taste and judgment of the jeweler. The following alloys of gold are transcribed from the memoranda of the proportions employed by a practical jeweler of considerable experience. When it is otherwise expressed, it will be understood all these alloys are made with fine gold, fine silver, and fine copper, obtained direct from the refiners. And to insure the standard gold passing the test of the Hall, 3 or 4 grains additional of gold are usually added to every ounce. First Group. Different kinds of gold that are finished by polish¬ ing, burnishing, etc., without necessarily requiring to be colored: The gold of 22 carats fine is so little used, on account of its expense and greater softness, that it has been purposely omitted. 18 carats, or New Standard gold, of yellow tint: 15 dwt. 0 grs. gold. 2 dwt. 18 grs. silver. 2 dwt. 6 grs. copper. 20 dwt. 0 grs. carats of red tint: 15 dwt. 0 grs. gold. 1 dwt. 18 grs. silver. 3 dwt. 6 grs. copper. 20 dwt. 0 grs. 16 carats or Spring gold: this, when drawn or rolled very hard, makes springs little inferior to those of steel. 1 oz. 16 dwt. gold. or 1.12 6 dwt. silver. •— .4 12 dwt. copper. — .12 2 oz. 14 dwt. 2. 8 $15 gold of yellow tint, or the fine gold of the jewelers; 16 carats nearly: 1 oz. 0 dwt. gold. 7 dwt. silver. 5 dwt. copper. 1 oz. 12 dwt. $15 gold of red tint, or 16 carats: 1 oz. 0 dwt. gold. 2 dwt. silver. 8 dwt. copper. 1 oz. 10 dwt. Second Group. Colored golds: these all require to be submitted to the process of wet-coloring, which will be explained; they are 192 THE PRACTICAL METAL-WORKER’S ASSISTANT. •used in much smaller quantities, and require to be very exactly proportioned. Full red gold: 5 dwt. gold. 5 dwt. copper. 10 dwt. Red gold: 10 dwt. gold. 1 dwt. silver, 4 dwt. copper. 15 dwt. Green gold: 5 dwt. 0 grs. gold. 21 grs. silver. 5 dwt. 21 grs. Gray gold: (Platinum is also called gray gold by jewel¬ ers.) 3 dwt. 15 grs. gold. 1 dwt. 9 grs. silver. 5 dwt. 0 grs. Blue gold: scarcely used: 5 dwt. gold. 5 dwt. steel filings. 10 dwt. Antique gold, of a fine green¬ ish-yellow color: 18 dwt. 9 grs. gold, or 18. 9 21 grs. silver, — 1. 3 18 grs. copper,— .12 20 dwt. 0 grs. 20. 0 Third Group. Gold solders: these are generally made from gold of the same quality and value as they are intended for, with a small addition of silver and copper, thus: Solder for 22 carat gold: 1 dwt. 0 grs. of 22 carat gold. 2 grs. silver. 1 gr. copper. 1 dwt. 3 grs. Solder for $15 gold : * 1 dwt. 0 grs. of $15 gold. 10 grs. silver. 8 grs. copper. 1 dwt. 18 grs. Solder for 18 carat gold: 1 dwt. 0 grs. of 18 carat gold. 2 grs. silver. 1 gr. copper. 1 dwt. 3 grs. Solder for $10 gold: but mid¬ dling silver solder is more generally used. 1 dwt. fine gold. 1 dwt. silver. 2 dwt. copper. 4 dwt. Dr. Hermstadt’s imitation of gold, which is stated not only to re¬ semble gold in color, but also in specific gravity and ductility, con- * By others, 4 grains of brass are added to the solder; it then fuses beauti¬ fully and is of good color. Zinc is sometimes added to other good solders to increase their fusibility, the zinc (or brass when used) should he added at the last moment, to lessen the volatilization of the zinc. METALS AND ALLOYS. 193 sists of 16 parts of platinum, 7 parts of copper, and 1 zinc, put in a crucible, covered with charcoal powder, and melted into a mass. Gold alloyed with platinum is also rather elastic, but the plati¬ num whitens the alloy more rapidly than silver. LEAD appears to have been known in the earliest ages of the world. Its color is bluish white; it has much brilliancy, is remarkably flexible and soft, and leaves a black streak on paper: when handled it exhales a peculiar odor. It melts at about 612°, and by the united action of heat and air, is readily converted into an oxide. Its specific gravity, when pure, is 11.445; but the lead of commerce seldom exceeds 11.35. Lead is used in a state of comparative purity for roofs, cisterns, pipes, vessels for sulphuric acid, etc. Ships were sheathed with lead and with wood, from before the Christian era to 1450, after which wood was more commonly employed, ‘ and in 1790 to 1800 copper sheathing became general; of late years, lead with a little antimony has likewise been used, also an alloy of copper and zinc and galvanized sheet iron. The most important alloys of lead are those employed for printers’ type, namely, about 3 lead, 1 antimony, for the smallest, hardest and most brittle types. 4 lead, 1 antimony, for small, hard, brittle types. 5 lead, 1 antimony, for types of medium size. 6 lead, 1 antimony, for large types. 7 lead, 1 antimony, for the largest and softest types. In addition to lead and antimony, type-metal also contains from 4 to 8 per cent, of tin, and sometimes 1 to 2 per cent, of copper; but as old metal is always used with the new, the proportions are not exactly known. Stereotype-plates are made of 20 parts of lead, 4 of antimony, and 1 of tin. Baron Wetterstedt’s patent sheathing for ships, consists of lead with from 2 to 8 per cent, of antimony ; about 3 per cent, is the usual quantity. The alloy is rolled into sheets. Similar alloys, and those of lead and tin in various prep¬ arations, are much used for emery wheels and grinding- tools of various forms by the lapidary, engineer, and others. The latter also employs these readily-fused alloys for tem¬ porary bearings, guides, screw nuts, etc. Organ pipes consist of lead alloyed with about half its quantity of tin to harden it. The mottled or crystalline ap¬ pearance so much admired shows an abundance of tin. Shot metal is said to consist of 40 lbs. of arsenic to one ton of lead. 194 THE PRACTICAL METAL-WORKER’S ASSISTANT. In casting sheet-lead, the metal was poured from a swing- trough upon a long and nearly horizontal table covered with a thin layer of coarse damp sand, previously levelled with a metal rule or strike. The thickness of the fluid metal was determined by running the strike along the table before the lead cooled, the excess being thus swept into a spill-trough at the lower end of the table; but the sheet- lead now more commonly used, is cast in a thick slab, and reduced between laminating rollers; it is known as “ milled - lead.” The metal for organ-pipes is prepared by allowing the metal to escape through the slit in a trough, as it is slid along a horizontal table, so as to leave a trail of metal be¬ hind it; the thickness of the metal is regulated by the width of the slit through which it runs, and the rapidity of the traverse ; a piece of cloth or ticken is stretched upon the casting table. The metal is planed to thickness, bent up and soldered into the pipes. Lead pipes are cast as hollow cylinders and drawn out upon triblets; they are also cast of indefinite length with¬ out drawing. A patent was taken out for casting a sheath of tin within the lead, but it has been abandoned. Lead shot are cast by letting the metal run through a narrow slit, into a species of colander at the top of a lofty tower ; the metal escapes in drops, which for the most part assume the spherical form before they reach the tank of water into which they fall at the foot of the tower, and this prevents their being bruised. The more lofty the tower, the larger the shot that can be produced; the good and the bad shot are separated by throwing small quantities at a time upon a smooth board nearly horizontal, which is slightly wriggled ; the true or round shot run to the bottom, the imperfect ones stop by the way, and are thrown aside to be re-melted; the shot are afterwards riddled or sifted for size, and churned in a barrel with black lead. MERCURY is a brilliant white metal, having much of the color of silver, whence the terms hydrargyrum, argentum vivum, and quicksilver. It has been known from very remote ages. It is liquid at all common temperatures; solid and malleable . at 40° F., and contracts considerably at the moment of con¬ gelation. It boils and becomes vapor at about 670°. Its specific gravity at 60° is 13.5: In the solid state its den¬ sity exceeds 14. The specific gravity of murcurial vapor is 6.976. Mercury is used in the fluid state for a variety of philo¬ sophical instruments, and for pressure gages for steam-en¬ gines, etc. It is sometimes, although rarely, employed for rendering alloys more fusible; it is used with tin-foil for METALS AND ALLOYS 195 silvering looking-glasses, and it has been employed as a substitute for water in hardening steel. Mercury forms amalgams with bismuth, copper, gold, lead, palladium, sil¬ ver, tin, and zinc. Mercury is commonly used for the extraction of gold and silver from their ores by amalgamation, and also in water- gilding. NICKEL is a white brilliant metal, which acts upon the magnetic needle, and is itself capable of becoming a magnet. Its magnetism is more feeble than that of iron, and vanishes at a heat somewhat below redness, 630°. It is ductile and malleable. Its specific gravity varies from 8.27 to 8.40 when fused, and after hammering, from 8.69 to 9.00. It is not oxidized by exposure to air at common temperatures, but when heated in the air it acquires various tints like steel; at a red-heat it becomes coated by a gray oxide. Nickel is scarcely used in the simple state, but princi¬ pally used together with copper and zinc, in alloys that are rendered the harder and whiter the more nickel they contain; they are known under the names of albata, British plate, electrum, German silver, pakfong, teutanag, etc.: the pro¬ portions differ much according to price; thus the Commonest are 3 to 4 parts nickel, 20 copper, and 16 zinc. Best . are 5 to 6 parts nickel, 20 copper, and 8 to 10 zinc. About two-thirds of this metal is used for articles resem¬ bling plated goods, and some of which are also plated ; the remainder is employed for harness, furniture, drawing and mathematical instruments, spectacles, the tongues for accor¬ dions, and numerous other small works. The white copper of the Chinese, which is the same as the German silver of the present day, is composed of 31.6 parts of nickel, 40.4 of copper, 25.4 of zinc, and 2.6 of iron, 17.48 - 53.39 - 13.0 -. The white copper manufactured at Sutil in the duchy of Saxe Hildburghausen, is said by Keferstein to consist of copper 88.000, nickel 8.753, sulphur with a little antimony 0.750, silex, clay, and iron 1.75. The iron is considered to be accidentally introduced into these several alloys along with the nickel, and a minute quantity is not prejudicial. Iron and steel have been alloyed with nickel; the former (the same as the meteoric iron which always contains nickel) is little disposed to rust: whereas the alloy of steel with nickel is worse in that respect than steel not alloyed. PALLADIUM is of a dull-white color, malleable and ductile, specific gravity is about 11.3, or 11.86 when laminated. 196 THE PRACTICAL METAL-WORKER’S ASSISTANT. fuses at a temperature above that required for the fusion of gold. Palladium is a soft metal, but its alloys are all Larder than the pure metal. With silver it forms a very tough malleable alloy, fit for the graduations of mathematical in¬ struments, and for dental surgery, for which it is much used by the French. With silver and copper, palladium makes a very springy alloy, used for the points of pencil-cases, inoculating lancets, tooth-picks, or any purpose where elas¬ ticity and the property of not tarnishing are required. Thus alloyed it takes a high polish. Pure palladium is not fusible at ordinary temperatures, but at a high tempera¬ ture it agglutinates so as to be afterwards malleable and ductile. This useful metal has recently been found in some abun¬ dance in the gold ores of the Minas Geraes district. Pal¬ ladium is calculated thoroughly to fulfil many of the purposes to which platinum and gold are applied in the useful arts, and from its low specific gravity it may be ob¬ tained at about half the price of an equal hulk of platinum, and at one-eighth that of gold; and it equally resists the action of mineral acids and sulphuretted hydrogen. Palladium was used in the construction of the balances for the United States Mint. PLATINUM is a white metal, extremely difficult of fusion, and unaltered by the joint action of heat and air. It varies in density from 21 to 21.5, according to the degree of mechan¬ ical compression which it has sustained. It is extremely ductile, but cannot be beaten into such thin leaves as gold and silver. The particles of the generality of the metals, when sep¬ arated from the foreign matters with which they are com¬ bined, are joined into solid masses by simple fusion; but platinum being nearly infusible when pure, requires a very different treatment. The platinum is first dissolved chemically, and it is then thrown down in the state of a precipitate; next it is partly agglutinated in the crucible into a spongy mass, and is then compressed whilst cold in a rectangular mould by means of a powerful fly-press or other means, which in operating upon 500 ounces, converts the platinum into a dense block about 5 inches by 4, and 2| inches thick. This block is heated in a smith’s forge, with two tuyeres meeting at an angle, at which spot the platinum is placed, amidst the charcoal fire. When it has reached the welding point, or almost a blue heat, it receives one blow under a heavy drop, or a vertical hammer somewhat like a pile-driving engine ; it then requires to be reheated, and it thus receives a fresh METALS AND ALLOYS. 197 blow about every twenty minutes, and in a week or ten days it is sufficiently welded or consolidated on all sides to admit of being forged into bars, and converted into sheets, rods, or wires by the ordinary means. The motive for operating upon so great a quantity is for making the large pans for concentrating sulphuric acid in only two or three pieces, which are soldered together with fine gold. In France 2000 ounces are sometimes welded into one mass, so that the vessels may be absolutely entire. For small quantities the treatment is the same, but in place of the drop, the ordinary flatter and sledge-hammer are used. Platinum is exceedingly tough and tenacious, and “ hangs to the file worse than copperon which account, when it is used for the graduated limbs of mathematical instruments, the divisions should be cut with a diamond- point, which is the best instrument for fine graduations of all kinds, and for ruling grounds, or the lined surfaces for etchings. Platinum is employed in Russia for coin. This valuable metal is also used for the touch-holes of fowling-pieces, and in various chemical and philosophical apparatus in which resistance to fusion or to the acids is essential. The alloys of platinum are scarcely used in the arts; that with a small quantity of copper is employed in Paris for dental surgery. "Dr. Yon Eckart’s alloy contains platinum 2.40, silver 3.53, and copper 11.71. It is highly elastic, of the same specific gravity as silver, and not subject to tarnish; it can be drawn to the finest wire from §• of an inch diameter without annealing, and does not lose its elasticity by an¬ nealing. It is highly sonorous, and bears hammering red- hot, rolling and polishing.” Dr. Ryan added to silver one-fourth of its weight of platinum, and he considers that it took up one-tenth its weight. The alloy became much harder than silver, capable of resisting the tarnishing influences of sulphur and hydro¬ gen, and was fit for graduations. An alloy of platinum with ten parts of arsenic is fusible at a heat a little above redness, and may therefore be cast in moulds. On exposing the alloy to a gradually-increasing temperature in open vessels, the arsenic is oxidized and ex¬ pelled, and the platinum recovers its purity and infusibilitv. Tin also so greatly increases the fusibility of platinum that it is hazardous to solder the latter metal with tin- solder, although gold is so used. Platinum, as well as gold, silver and copper, are deposited by the electrotype process; and silver plates thus platinized are employed in the galvanic battery. 198 THE PRACTICAL METAL-WORKER^ ASSISTANT. RHODIUM is a white metal very difficult of fusion. Its specific gravity is about 11; it is extremely hard; when pure the acids do not dissolve it. Rhodium has been long employed for the nibs of pens, which have been also made of ruby, mounted on shafts of spring gold. These kinds have had to endure for the last seven or eight years the rivalry of “ Hawkins’s Everlasting Pen,” of which latter, the author, from many months’ con¬ stant use, can speak most favorably. “The everlasting pen,” says the inventor, “is made of gold tipped with a natural alloy, which is as much harder than rhodium as steel is harder than lead ; will endure longer than the ruby; yields ink as freely as the quill; is easily wiped; and if left unwiped is not corroded.” Mr. Hawkins employs the natural alloy of iridium and osmium, two scarce metals discovered by Mr. Tennant, of Belfast, amongst the grains of platinum. The alloy is not malleable, and is so hard as to require to be worked with diamond powder. The metals rhodium, iridium, and os¬ mium, are not otherwise employed in the arts than for pens, although steel has been alloyed with rhodium. The inventor of the gold pen, Mr. Hawkins, is an American. SILVER is of a more pure white than any other metal. It has considerable brilliancy, and takes a high polish. Its specific gravity varies between 10.4, which is the density of cast silver, and 10.5 to 10.6, which is the density of rolled or stamped silver. It is so malleable and ductile, that it may be extended into leaves not exceeding the ten-thousandth of an inch in thickness, and drawn into wire much finer than a human hair. Silver melts at a bright-red heat, at 1873° of Fahrenheit’s scale, and when in fusion appears extremely brilliant. Silver is but little used in the pure unalloyed state, on account of its extreme softness, but it is generally alloyed with copper in about the same proportion as in our coin, and none of inferior value can receive the “ Hall mark.” Diamonds are set in fine silver, and in silver containing 3 to 12 grs. of copper in the ounce. The work is soldered with pure tin. The sheet metal for plated works is prepared by fitting together very truly a short stout bar of copper and a thin¬ ner plate of silver. When scraped perfectly clean they are tied strongly together with binding wire, and united by partial fusion without the aid of solder. The plated metal is then rolled out, and the silver always remains perfectly united and of the same proportional thickness as at first. Additional silver may be burnished on hot, when the sur- METALS AND ALLOYS. 199 faces are scraped clean, as explained under gold. This is done either to repair a defect, or to make any part thicker for engraving upon, and the uniformity of surface is re¬ stored with the hammer. In addition to its use for articles of luxury, the important service of copper plated with silver for the parabolic reflectors of light-houses must not be overlooked. These are worked to the curve with great perfection by the hammer alone. Plated spoons, forks, harness, and many other articles, are made of iron, copper, brass, and German silver, either cast or stamped into shape. The objects are then filed and scraped perfectly clean ; and fine silver, often little thicker than paper, is attached with the aid of tin solder and heat. The silver is rubbed close upon every part with a bur¬ nisher. The electrotype process is also used for plating several of the metals with silver, which it does in the most uniform and perfect manner. The silver added is charged by weight at about three times the price of the metal. The German silver, or albata, is generally used for the interior substance, as when the silver is partially worn through the white alloy is not so readily detected as iron or copper. Silver Alloys. The alloy with copper constitutes plate and coin. By the addition of a small proportion of copper to silver, the metal is rendered harder and more sonorous, while its color is scarcely impaired. Even with equal weights of the two metals, the compound is white. The maximum of hard¬ ness is obtained when the copper amounts to one-fifth of the silver. “ For silver plate, the French proportions are 9f parts silver, J copper; and for trinkets, 8 parts silver, 2 copper.” Silver solders are made in the following proportions: Hardest silver solder, 4 parts fine silver, and 1 part copper ; this is difficult to fuse, but is occasionally employed for figures. Hard silver solder, 3 parts silver, and 1 part brass wire, which is added when the silver is melted, to avoid wasting the zinc. Soft silver solder for general use, 2 parts fine silver, and 1 part brass wire. By some few, § part of arsenic is ad¬ ded, to render the solder more fusible and white, but it be¬ comes less malleable ; the arsenic must be introduced at the last moment, with care to avoid its fumes. Silver is also soldered with tin solder (2 tin, 1 lead), and with pure tin. Silver and mercury are used in the plastic metallic stop ping for teeth. 200 THE PRACTICAL METAL-WORKER'S ASSISTANT TIN has a silvery-white color with a slight tint of yellow; it is malleable, though sparingly ductile. Common tin-foil, which is obtained by beating out the metal, is not more than one-thousandth of an inch in thickness, and what is termed white Duck metal is in much thinner leaves. Its specific gravity fluctuates from 7.28 to 7.6, the lightest being the purest metal. When bent it occasions a peculiar crackling noise, arising from the destruction of cohesion amongst its particles. When a bar of tin is rapidly bent backwards and for¬ wards, several times successively, ic becomes so hot that it cannot be held in the hand. When rubbed, it exhales a peculiar odor. It melts at 442°, and, by exposure to heat and air, is gradually converted into a protoxide. Pure tin is commonly used for dyers’ kettles; it is also sometimes employed for the bearings of locomotive car¬ riages and other machinery. This metal is beaten into very large sheets, some of which measure 200 by 100 inches, and are of about the thickness of an ordinary card: the small sized foil is stated not to exceed one-thousandth of an . inch in thickness. The metal is first laminated between rollers, and then spread one sheet at a time upon a large iron surface or anvil, by the direct blows of hammers with very long handles; great skill is required to avoid beating the sheets into holes. The large sheets of tin-foil are only used for silvering looking-glasses by amalgamation with mercury. Tin-foil is also used for electrical purposes. The amalgam used for electrical machines, is 7 tin, 3 zinc, and 2 mercury. Tin is drawn into wire, which is soft and capable of be¬ ing bent and unbent many times without breaking; it is moderately tenacious and completely inelastic. Tin tube is extensively used for gas fitting and many other purposes by Le Roy & Co., of New York; it has been recently in¬ troduced in an ingenious manner for the formation of very cheap vessels, for containing artists’ and common colors, besides numerous other solid substances and fluids, required to be hermetically sealed, with the power of abstracting small quantities. Tin plate is an abbreviation of tinned iron plate; the plates of charcoal iron are scoured bright, pickled, and im¬ mersed in a bath of melted tin covered with oil, or with a mixture of oil and common resin; they come out thoroughly coated. Tinned iron wire is similarly prepared: there are several niceties in the manipulation of each of these pro¬ cesses, which cannot be noticed in this place. Tin is one of the most cleanly and sanatory of metals, and is largely consumed as a coating for culinary vessels* METALS AND ALLOYS. 20i although the quantity taken up in the tinning is exceed¬ ingly small, and which was noticed by Pliny. Tin imparts hardness, whiteness and fusibility to many alloys, and is the basis of different solders, and other im¬ portant alloys, all of which have a low power of conduct¬ ing heat. Pewter is principally tin; mostly lead is the only addi¬ tion, at other times copper, but antimony, zinc, etc., are used with the above, as will be separately adverted to. The ex¬ act proportions are unknown even to those engaged in the manufacture of pewter, as it is found to be the better mixed when it contains a considerable portion of old metal to which new metal is added by trial. Some pewters are made very common; when cast they are black, shining and soft; when turned, dull and bluish. Other pewters only contain one fifth or one-sixth of lead; these when cast are white, without gloss and hard ; such are pronounced very good metal, and are but little darker than tin. The French legislature sanctions the employment of 18 per cent, of lead with 82 of tin as quite harmless in vessels for wine and vinegar. The finest pewter, frequently called “tin and temper,” consists mostly of tin, with a very little copper, which makes it hard and somewhat sonorous, but the pewter be¬ comes brown-colored when the copper is in excess. The copper is melted, and twice its weight of tin is added to it, and from about J to 7 lbs. of this alloy or the “temper,” are added to every block of tin weighing from 360 to 390 pounds. Antimony is said to harden tin and to preserve a more silvery color, but is little used in pewter. Zinc is employed to cleanse the metal rather than as an ingredient; some stir the fluid pewter with a thin strip, half zinc and half tin; others allow a small lump of zinc to float on the surface of the fluid metal whilst they are casting, to lessen the oxidation. White metal is said to consist of 3| cwt. of block tin, 28 lbs. antimony, 8 lbs. copper, and 8 lbs. brass; it is cast into ingots and rolled into very thin sheets. Tin solders are very much used in the arts. 1 tin, 3 lead, the coarse plumber’s solder, melts at about 500 F. 2 tin, 1 lead, the ordinary or fine tin solder, melts at about 360 F. ZINC is a bluish-white metal, with considerable lustre, rather hard, of a specific gravity of about 6.8 in its usual state, but, when drawn into wire, or rolled into plates, its density is aug¬ mented to 7 or 7.2. In its ordinary state at common tern- 202 THE PRACTICAL METAL-WORKER’S ASSISTANT. peratures it is tough, and with difficulty broken by blows of the hammer. It becomes very brittle when its tempera¬ ture approaches that of fusion, which is about 773°; but at a temperature a little above 212°, and between that and 300°, it becomes ductile and malleable, and may be rolled into thin leaves, and drawn into moderately fine wire, which, however, possesses but little tenacity. When a mass of zinc, which has been fused, is slowly cooled, its fracture exhibits a lamellar and prismatic crystalline texture. Zinc, which is commercially known as “Spelter,” although it is always brittle when cast, has of late years taken its place amongst the malleable metals; the early stages of its manufacture into sheet, foil and wire are stated to be con¬ ducted at a temperature somewhat above that of boiling water; and it may be afterwards bent and hammered cold, but it returns to its original crystalline texture when re- melted. It has been applied to many of the purposes of iron, tinned-iron, and copper; it is less subject to oxidation from the effects of the atmosphere than the iron, and much cheaper, although less tenacious, ductile, or durable than the copper. The sheet metals when bent lengthways of the sheet (or like a roll of cloth), are less disposed to crack than if bent sideways; in this respect zinc and sheet iron are the worst: the risk is lessened when they are warmed. Zinc is applied as a coating to preserve iron from rust. Zinc mixed with one-twentieth its weight of speculum metal may be melted in an iron ladle, and made to serve for some of the purposes of brass, such as common chucks. The alloy is sufficient to modify the crystalline character, but reserves the toughness of the zinc; it will not, however, bear hammering either hot or cold. Four atoms of zinc and one of tin, or 133.2 and 57.9, make a hard, malleable, and less crystalline alloy. Biddery ware, manufactured at Biddery, a large city, 60 miles N.W. of Hyderabad in the East Indies, and also at Benares, is said to consist of copper 16 oz., lead 4 oz., and tin 2 oz., melted together; and to every 3 oz. of this alloy, 16 oz. of spelter or zinc are added. The metal is used as an inferior substitute for silver, and resembles some sorts of pewter. The foregoing alloys are mostly derived from actual practice, and although it has been abundantly shown that alloys are most perfect, when mixed according to atomic proportions, or by multiples of their chemical equivalents, yet this excellent method is little adopted, owing to various interferences. For example, it is in most cases necessary from an eco¬ nomic view, to mix some of the old alloys (the proportions of which are uncertain), along with the new metals. In most METALS AND ALLOYS. 203 cases also, unless the fusion and refusion of the alloys are conducted with considerably more care than ordinary prac¬ tice ever attains, or really demands, the loss by oxidation completely invalidates any nice attempts at proportion; and which proportions can be alone exactly arrived at when the combined metals are nearly or quite pure. The chemical equivalents of the metals upon the hydro¬ gen scale are appended; thus for mixtures of any metals, say tin and zinc, instead of taking arbitrary quantities, one atom of tin or 57.9 parts by weight, should be combined with 1, 2, 3, 4 or 5 atoms of zinc, or any multiple of 32.3 parts, and so with all other metals. In the following table the first column of figures denotes the comparative strength of the metals, glass being considered as unity; thus steel of razor temper is nearly 16 times as strong as glass of equal size; and by the second column, it is seen that a bar of steel one inch square is pulled asunder by a load of 150,000 lbs. Note. —The following Alloys having been omitted in their proper places are here inserted together. Babbitt’s Anti-Attrition Metal—Directions for Preparing and Fitting.— Melt 4 lbs. of copper, add. by degrees, 12 lbs. best quality Banca tin, 8 lbs. regulus of antimony, and 12 lbs. more of tin while the composition is in a melted state. After the copper is melted and 4 or 5 lbs. of tin have been added, the heat should be reduced to a dull red, to prevent oxidation ; then add the remainder of the metal as above. In melting the composition it is better to keep a small quantity of powdered charcoal on the surfaoe of the metal. The above composition is called “hardening.” For lining the boxes, take one lb. of this hardening and melt it with 2 lbs. of Banca tin, which produces the lining metal for use. Thus the proportions for lining metal are 4 lbs. of copper, 8 lbs. of regulus of antimony, and 96 lbs. of Banca tin. The article to be lined, having been cast with a recess for the lining, is to be nicely fitted to a former , which is made of the same shape as the bearing. Drill a hole in the article for the reception of the metal, say a half or three- quarters of an inch, according to the size of it. Coat over the part not to be tinned with a clay wash, wet the part to be tinned with alcohol, and sprinkle on it powdered sal ammoniac ; heat it till a fume arises from the sal ammo¬ niac, and then immerse it in melted Banca tin, taking care not to heat it so that it will oxidize. After the article is tinned, should it have a dark color, sprinkle a little sal ammoniac on it, which will make it of a bright silver color. Cool it gradually in water, then take the former to which the article has been fitted, and coat it over with a thin clay wash, and warm it so that it will be perfectly dry ; heat the article until the tin begins to melt, lay it on the former and pour in the metal, which should not be so hot as to oxidize, through the drilled hole, giving it a head, so that as it shrinks it will fill up. After it has sufficiently cooled remove the former. A shorter method may be adopted when the work is light enough to handle quickly, namely—When the article is prepared for tinning, it may be im¬ mersed in the lining metal instead of the tin, brushod lightly in order to remove the sal ammoniac from the surface, placed immediately on the former and lined at the same heating. Fenton’s Anti-Friction Metal.— 7^ parts of grain zinc, 7^ of purified zinc, and 1 of antimony. Alloy of the Standard Measure used by Government. —576 parts copper, 59 of tin, and 48 of brass (yellow, 2 copper to 1 of zinc). Tutenague.— 8 parts of copper, 5 of zinc, and 3 of nickel. Expansion Metal. —9 parts of lead, 2 of antimony, and 1 of bismuth. 204 TABLES OF THE COHESIVE FORCE OF SOLID BODIES. Table I.— Metals. (A) and (J) mark the highest and lowest result which Muschenbroek obtained from each kind of iron. METALS. 1 • O) w so*- ^ 00 O c « c3 ° 3 £2 ® % o h ‘o *> AUTHORITY. ^ 2 « 2 06 . =3 5 C- u. t- Spec sion, Coh a sq in 11 U1 to X Eh STEEL. Razor temper..., Soft. IRON. Wire. German bar,markBR(h) Swedish bar (A). German bar, mark L (A) Wire. Bar. Liege bar (A). Spanish bar. Bar. Bar.. Oosement bar (A).. Cable. German bar, mark L ( l) German bar, common... Swedish bar I Oosement bar j ' Bar of best quality.... Liege bar ( l) . German bar, mark BR(Z) Bar*.. Bar of good quality. Cable. Bar, fine-grained.. -medium fineness... —coarse-grained. CAST IRON. French.J German. French, soft. ..J English.J French. English, soft.. 15.927 12.739 12.004 9.880 9.445 9.119 9.108 8.964 8.794 8.685 8.581 8.492 8.142 7.752 7.382 7.339 7.296 7.006 6.621 6.514 6.480 5.839 5.787 5.306 3.618 2.172 7.470 7.250 6.754 5.520 5.412 4.540 4.334 150,000 120,000 113,077 9.3,069 88,972 85,000 85,797 84,443 82,839 81,901 80,833 80,000 76,697 73,024 69,5.38 69,133 68,728 66,000 62,369 61,361 61,041 55,000 54,513 49,982 34,081 20,460 70,367 68,295 63,622 52,000 50,981 42,666 40,824 t 7.78 to 7.84 « si a o 11 7.807 Mnschenbroek, Encyclo. Brit., art. Strength. Idem. Sickingen, Ann. de Chimie, xxv. 9. Muschenb. Int. ad Phil. Nat. i. 426. Idem. Idem. Buffon, (Euvres deGauthey, ii. 153. Emerson, Mechanics, 115. Muschenb. Int. ad Phil. Nat. i. 426. Idem. Soufflot Rondelet’s L’Art de Batir, iv. 500. Edin. Encyclo., art. Bridge, 544. Muschenb. Intr. ad Phil. Nat. i. 426. Annals of Phil. vii. 320. Muschenb. Intr. ad Phil. Nat. i. 426 Idem. Idem. Rumford, Phil. Mag. x. 51. Muschenb. Intr. ad Phil. Nat. i. 426. Idem. Perronet. CEuv. de Gauthey, ii. 154. Rumford, Phil. Mag. x. 51. Annals of Phil. x. 311. Rondelet, L’Art. de Bdtir, ir. 502 Idem. Idem. Navier, (Euv. de Gauthey, ii. 150. Muschenb. Intr. ad Phil. Nat. i. 417. Rondelet, L’Art. de Batir, iv, 514. Banks, Gregory's Meehan, i. 129. Ex. i. L’Ecole des Fonts, etc. Gaut. ii. 150. Gauthey, (Euvres, ii. 150. Banks, Greg. Mecb. i. 148. Ex. iii. * This is the mean result of thirty-three experiments, t Kirwan, Elem. Miner, ii. 155. t Calculated from experiments on the transverse strength, by arts. 14 and 15. | Yielding to the file without difficulty. 205 TABLES OF THE COHESIVE FORCE OF SOLID BODIES. Table I.— Continued. METALS. a M ^ 00 O (jj o ci £ 3 § c Q- O tfi *£ o o a *s o > J- O .a ® o o oa .3 |1 & t-. bfl AUTHORITY. CAST-IRON. French gray.* 4.000 37,680 Gray, of Cruzot, 2d fu- sion.* 3.257 30,680 Gray, of Cruzot, 1st fu- sion. * 3.202 30,162 COPPER. Wire... . 6.606 61,228 Cast, Barbary. 2.396 22,570 8.182 - Japan. 2.152 20,272 8.726 PLATINUM. Wire... 5.995 56,473 20.847 Wire. 5.625 52,987 SILVER. Wire. 4.090 38,257 Cast.. 4.342 40,902 11.091 GOLD. Wire. 3.279 30,888 Cast. 2.171 20,450 19.238 TIN. Wire. 0.7568 7,129 Cast, English black. 0.706 6,650 -idem. 0.565 5,322 7.295 -Banca. 0.3906 3,679 7.2165 1 -Malacca. 0.342 3,211 6.1256 J BISMUTH. Cast. 0.345 3,250 3,008 9.810 ) 0.3193 9.926} ZINC. Wire. 2.394 22,551 ] Patent sheet. 1.762 16.616 | Cast, Goslar, from. 0.3118 2,937 7.215 J to. 0.2855 2,689 LEAD. Milled. . 0.3533 3,328 11.4071 Wire. 0.334 3,146 2,581 11.348 Wire. 0.274 11.282 Wire. 0 2704 2,547 Cast, English. 0.094 885 11.479 j Antimony, cast. 0.1126 1,060 4.500 8? 7? 72 6t 5? Rondelet, L’Art. de B&tir, iv. 514. Ramus, Gauthey, ii. 150. Idem, f Sickingen, Ann. de Chimie, xxv. 9. Muschenb. Intr. ad Phil. Nat. i. 417. Idem. Morveau, Ann. de Chimie, xxv. 8. Sickingen, Ann. de Chimie, xxv. 9. Sickingen, Ann. de Chimie, xxv. 9. Muschenb. Intr. ad Phil. Nat. i. 417. Sickingen, Ann. de Chimie, xxv. 9. Muschenb. Intr. ad Phil. Nat. i. 417. Morveau, Ann. de Chim. lxxi. 194. Muschenb. Intr. ad Phil. Nat. i. 417. Idem. Idem. Idem. Muschenb. Intr. ad Phil. Nat. i. 417. Idem. i. 454. Morveau, Ann. de Chim. lxxi. 194. By my trial. Muschenb. Int. ad Phil. Nat. i. 417. By my trial. Muschenb. Intr. ad Phil. Nat. i. 452. Idem. Morveau, Ann. de Chim. lxxi. 194. Muschenb. Intr. ad Phil. Nat. i.452. Muschenb. Intr. ad Phil. Nat. i. 417. * Calculated from experiments on the transverse strength, by arts. 14 and 15. f In the operation of casting, the surface of the iron always becomes much harder, and is more tenacious than the internal parts; hence the strength of a small specimen is always greater than that of a large one. IV. B .—When the specific gravity is not referred to a separate authority, it is to be con¬ sidered that of the specimen of which the cohesive force is given. J Kirwan’s Miner, vol. ii. g Thomson’s Chemistry, vol. i. 206 TABLES OF THE COHESIVE FORCE OF SOLID BODIES. Table II. —Allots. 1 • AUTHORITY. w U • ® C3 g a 3 £ m to a, © O w P 1 U2 co Parts. Parts. Gold. 2 Silver. 1 2.972 28,000 Musch. Encyclop. Brit. art. Gold. 5 Copper. 1 5.307 50,000 Idem. [Strength. Silver. 5 Copper....... 1 5.148 48,500 Idem. Silver. 4 Tin. 1 4.352 41,000 Idem. Brass.. 4.870 45,882 Muschenb., Colson, i. 242. Copper. 10 Tin. 1 3.407 32,093 36,088 Musoh. Intr. ad Phil. Nat. Copper. 8 Tin. 1 3.831 Idem. [i. 428. Copper. 6 Tin. 1 4.687 44,071 Idem. Copper. 4 Tin. 1 3.794 35.739 Idem. Copper. 2 Tin. 1 0.108 1,017 Idem. Copper. 1 Tin. 1 0.077 725 Idem. Tin, English 10 Lead. 1 0.733 6,904 Musch. Intr. ad Phil. Nat. Tin, - 8 Lead. 1 0.841 7,922 Idem. [i. 438. Tin, - 6 Lead. 1 0.849 7,997 Idem. Tin, - 4 Lead. 1 1.126 10,607 Idem. Tin, -- 2 Lead. 1 0.793 7,470 7,074 Idem. Tin, - 1 Lead. 1 0.751 Idem. Tin, Banca 10 Antimony... 1 1.187 11,181 7.359 Musch. Intr. ad Phil. Nat. Tin, - 8 Antimony... 1 1.049 9,881 7.276 Idem. [i. 442. Tin, 6 Antimony... 1 1.341 12,632 7.228 Idem. Tin, - 4 Antimony... 1 1.431 13,480 7.192 Idem. Tin, - 2 Antimony... 1 1.277 12,029 7.105 Idem. Tin, -- 1 Antimony... 1 0.338 3,184 7.060 Idem. Tin, - 10 Bismuth. 1 1.347 12,688 7.576 Musch. Intr. ad Phil. Nat. Tin, - 4 Bismuth. 1 1.772 16,692 14,017 7.613 Idem. [i. 443. Tin,- 2 Bismuth. 1 1.488 8.076 Idem. Tin, - 1 Bismuth. 1 1.276 12,020 8.146 Idem. Tin, --- 1 Bismuth. 2 1.063 10,013 8.58 Idem. Tin, - 1 Bismuth. 4 0.836 7,875 9.009 Idem. Tin, - 1 Bismuth. 10 0.411 3,871 9.439 Idem. Tin, - 10 Zinc, Indian 1 1.371 12,914 7.288 Musch. Intr. ad Phil. Nat. Tin, 2 Zinc. 1 1.595 15,025 7.000 Idem. [i. 444. Tin, - 1 Zinc. 1 1.682 15.844 7.321 Idem. Tin, - 1 2 1.701 0.602 16,023 5,671 7.100 7.130 Idem. Idem. Tin’ - 1 Zinc. 10 Tin, English 1 Zinc, Goslar 1 0.958 9,024 Musch. Intr. ad Phil. Nat. Tin, - 2 Zinc. 1 1.164 10,964 Idem. [i. 446. Tin, - 4 Zinc. 1 1.089 10,258 10,607 Tin, 8 Zinc. 1 1.126 Idem. Tin, - 1 Antimony... 1 0.154 1,450 7.000 Musch. Intr. ad Phil. Nat. Tin, - 3 Antimony... 2 0.338 3,184 Idem. [i. 448. Tin, - 4 Antimony... 1 1.202 11,323 Idem. Lead, Scotch 1 Bismuth. 1 0.777 7,319 10.931 Musch. Intr. ad Phil. Nat. Lead, - 2 Bismuth. 1 0.620 5,840 11.090 Idem. [i. 454. Lead, - L_ 10 Bismuth. 1 0.300 2,826 10.827 Idem. 207 TABULAR VIEW OF SOME OF THE PROPERTIES OF METALS. Platinum. Specific gravity. Chemical equiva¬ lents. 98.8 Gold. 199.2 Iridium. 98.8 Tungsten. 99.7 Mercury. 202. Palladium. 53.3 Lead. . 11.35 103.6 Rhodium. 52.2 Silver. . 10.47 108. Bismuth. . 9.80 71. Uranium. . 9.00 217. Copper. 31.6 Cadmium. . 8.60 55.8 Cobalt. . 8.53 29.5 Nickel. 29.5 Iron. 28. Molybdenum. 47.7 Tin. 57.9 Zinc. 32.3 Manganese. . 6.85 27.7 Antimony. 64.6 Tellurium. 64.2 Arsenic. 37.7 Titanium. 24.3 Sodium. 23.3 Potassium. 39.15 Alloys possessed of greater specific gra¬ vity than the mean of their components. Gold and Zinc. — Tin. — Bismuth. — Antimony. — Cobalt. Silver and Zinc. — Lead. — Tin. — Bismuth. — Antimony. Copper and Zinc. — Tin. — Palladium. — Bismuth. — Antimony. Lead and Bismuth. — Antimony. Platinum and Molybdenum. Palladium and Bismuth. FUSIBILITY. Fahrenheit. i Mercury. 39 deg. Potassium. 136 “ Sodium. 190 “ Tin. 442 " Bismuth. 497 “ Lead. 612 “ Tellurium, rather less fusi¬ ble than lead. Arsenic, undetermined. Zinc. 773 “ Antimony, a little below a red heat. Cadmium, about. 442 “ Silver. 1873 deg. /Copper. 1996 “ / Gold. 2016 “ | Cobalt, rather less fusible I than iron. -g 1 Iron, cast. 2786 “ i \lron, malleable., f r 3 iri “g 6 ^ | Manganese.j smith’s forge. a iNickel, nearly the same as Cobalt. £ /Palladium.. -2 \ Molybdenum.... -o [Uranium. (Almost infusible and 3 Tungsten. / not to be procured •g JChrom.um. in buttons by the | /Titanium.V heat of a s ' ith > s m/C erium./ f but fusible Osmium.I bef ? re the oxyhy _ dro ge n biow P i Pe . \ Platinum. Columbium.... Alloys having a specific gravity inferior to the mean of their components. Gold and Silver. — Iron. — Lead. — Copper. — Iridium. — Nickel. Silver and Copper. Copperand Lead. Iron and Bismuth. — Antimony. — Lead. Tin and Lead. — Palladium. — Antimony. Nickel and Arsenic. Zinc and Antimony. 208 TABULAR VIEW OF METALS— Continued. HARDNESS. ™ anium . | Harder than Steel. Platinum.. Palladium ..... Copper.. Gold.. Silver.^ Scratched by Calcspar. Tellurium. Bismuth.. Cadmium.. Tin.. SSir::::::: 1 «*»• Nickel. Cobalt. Iron.Scratched by glass. Antimony. Zinc.. Lead. Scratched by the nail. Sodium 11 ™.| Soft as wax (at 60 deg.) Mercury. Liquid. BRITTLENESS. The following metals are brittle, and most of them may even be reduced to powder. Antimony. Arsenic. Bismuth. Cerium. Chromium. Cobalt. Columbium. Manganese. Molybdenum. Rhodium. Tellurium. Titanium. Tungsten. Uranium. MALLEABILITY, Or admit of being extended by the hammer. Gold. Zinc. Silver. Iron. Copper. Nickel. Tin. Palladium. Cadmium. Potassium. Platinum. Sodium. Lead. Frozen Mercury. DUCTILITY, Or admit of being drawn into wires. Gold. Tin. Silver. Lead. Platinum. Nickel. Iron. Palladium Copper. Cadmium. Zinc. TENACITY. Weights sustained by wires 0.787 of a line diameter. Iron. 549 lbs. 250 dec. pts. Copper. 302 “ 278 “ Platinum. 274 “ 320 “ Silver. 187 “ 137 “ Gold. 150 “ 753 “ Zinc. 109 “ 540 “ Tin. 34 “ 630 “ Lead. 27 “ 621 “ Elasticity and sonorousness belong to the hardest metals only, and are most evident in certain alloys. Odor and taste are most remarkable in copper, iron, and tin. LINEAR DILATATIONS BY HEAT. Dimensions which a bar takes at 212°, whose length at 32° is 1.000000; also its dilatation in vulgar fractions. Platinum. 1.00091085 or one 1097th part. Palladium. 1.00100000 it 1000th if Antimony. 1.00108300 it 923d if Cast iron. 1.00111025 a 901st if Steel. 1.00121286 it 824th if Wrought Iron. 1.00124S60 a 801st a Bismuth. 1.00139200 u 718th a Gold. 1.00149824 u 667th a Copper. 1.00179633 a 557th a Gun metal (C.8,T.l) 1.00181700 a 550th a Brass. 1.00190663 a 524th a Speculum metal. 1.00193300 a 517th a Silver. , 1.01)200183 a 499th a Tin. 1.00235840 a 424th a Lead. , 1.00285768 u 350th a Zinc. , 1.00297650 a 336th tt The above are the mean proportions of the various examples of each metal, given in Ure’s Dictionary of Chemistry and elsewhere. POWER OF CONDUCTING HEAT. From Despretz’s Experiments.* Conducting power. Gold. 100 Platinum. 98.1 Silver. 97.3 Copper. 89.82 Iron. 37 41 Zinc. 36.37 Tin. 30.38 Lead. 17.96 Marble... 2.34 Porcelain. L22 Brick earth. 1.13f * Ann. de Chim. et de Phys. xix. 97. f TrnitS Eldmcntairede Phy¬ sique, par M. Despretz, p. 20, as quoted by Dr. Thomson, or Heat and Electricity, p. 103. 209 WEIGHTS OF WROUGHT-IRON, STEEL, COPPER, AND BRASS WIRE AND PLATES. The specific gravities to determine the weights of the following- named metals, and the calculations of them, were taken and made by Charles H. Has well, of New York, for the well-known manu¬ facturers, Messrs. J. R. Brown & Sharpe, of Providence, R. I. Diameter and thickness determined by American gage:— No. of Gage. Size of each number. Wire—per Lineal foot. Plates—per Lineal Foot. Wrought Iron. Steel. Copper. Bran. Wrought Iron. Steel. Copper. Vasa. Inch. Lbs. Lbs. Lbs. Lbs. Lbs. Lbs. Lbs. Lbs. 0000 .46000 .660740 .666030 .640513 .606176 17.25 17.48 20.838 19.688 000 .40964 .444683 .448879 .607946 .479908 15.3615 15.5663 18.5567 17.6326 00 .36480 .352669 .355986 .402830 .380666 13.68 13.8624 16.5254 16.6134 0 .32486 .279665 .282303 .319451 .301816 12.1823 12.3447 14.7162 13.904 1 .28930 .221789 .223891 .253342 .239353 10.8488 10.9934 13.1053 12.382 2 .25763 .176888 .177648 .200911 .189818 9.6611 9.7899 11.6706 11.0266 3 .22942 .139480 .140796 .169323 .150522 8.6033 8.7180 10.3927 9.8192 4 .20431 .110616 .111660 .126363 .119376 7.6616 7.7638 9.2652 8.7445 6 .18194 .087720 .088548 .100200 .094666 6.8228 6.9137 8.2419 7.787 6 .16202 .069565 .070221 .079462 .075076 6.0768 6.1668 7.3395 6.9345 7 .14428 .055165 .055685 .063013 .059545 6.4106 6.4826 6.6359 6.1752 8 .12849 .043751 .044164 .049976 .047219 4.8184 4.8826 6.8206 6.4994 9 .11443 .034699 .035026 .039636 .037437 4.2911 4.3483 5.1837 4.8976 10 .10189 .027512 .027772 .031426 .029687 3.8209 3.8718 4.6156 4.3609 11 .090742 .021820 .022026 .024924 .023549 3.4028 3.4482 4.1106 3.8838 12 .080808 .017304 .017468 .019766 .018676 3.0303 3.0707 3.6606 3.4586 13 .071961 .013722 .013851 .015674 .014809 2.6985 2.7345 3.2698 3.0799 14 .064084 .010886 .010909 .012435 .011746 2.4032 2.4352 2.9030 2.7428 15 .057068 .008631 .008712 .009859 .009315 2.1401 2.1686 2.6852 2.4425 16 .050320 .006845 .006909 .007819 .007687 1.9068 1.9312 2.3021 2.1761 17 .045257 .005407 .005478 .006199 .005857 1.6971 1.7198 2.0501 1.937 18 .040303 .004304 .004304 .004916 .004645 1.6114 1.6316 1.8257 1.726 19 .035890 .003413 .003445 .003899 .003684 1,3459 1.3638 1.6258 1.6361 20 .031961 .002708 .002734 .003094 .002920 1.1985 1.2145 1.4478 1.3679 21 .028462 .002147 .002167 .002452 .002317 1.0673 1.0816 1.2893 1.2182 22 .025347 .001703 .001719 .001945 .001838 .95051 .96319 1.1482 1.0849 23 .022571 .001350 .001363 .001642 .001457 .84641 .8577 1.0225 .96604 24 .020100 .001071 .001081 .001223 .001165 .75375 .7638 .91053 .86028 25 .017900 .0008491 .0008571 .0009699 .0009163 .67125 .6802 .81087 .76612 26 .016940 .0006734 .0006797 .0007692 .0007267 .59775 .60572 .72208 .68223 27 .014195 .0005340 .0005391 .0006099 .0005763 .53231 .63941 .64303 .60766 28 .012641 .0004235 .0004275 .0004837 .0004570 .47404 .48036 .67264 .53103 29 .011257 .0003358 .0003389 .0003835 .0003624 .42214 .42777 .50994 .48180 30 .0100-25 .0002663 .0002688 .0003042 .0002874 .37694 .38095 .45413 .42907 31 .008928 .0002113 .0002132 .0002413 .0002280 .3348 .33926 .40444 .38212 32 .007950 .0001675 .0001691 .0001913 .0001808 .29813 .3021 .36014 .34026 33 .007080 .0001328 .0001341 .0001517 .0001434 .2665 .26904 .32072 .30302 34 .006504 .0001053 .0001065 .0001204 .0001137 .2364 .23955 .28557 .26981 35 .005614 .00008366 .00008445 .0000956 .00009015 .21053 .21333 .25431 .24028 36 .005000 .00006625 .00006687 .0000757 .0000715 .1875 .19 .2265 .2140 37 .004453 .00005255 .00005304 .00006003 .00005671 .16699 .16921 .20172 .19069 38 .003965 .00004166 .00005205 .00004758 .00004496 .14869 .15067 .17961 .1697 39 .003531 .00003305 .00003336 .00003775 .00003566 .13241 .13418 .15095 .16113 40 .003144 .00002620 .00002644 .00002992 .00002827 .1179 .11947 .14242 .13466 Specific Gravities .. 7.774 1 7.841 1 8.880 8.386 7.200 1 7.296 1 8.698 1 8.218 Weights of a cub. ft. 585.87 | 490.45 | 654.988 624.16 450. | 456. | 543.6 | 513.6 14 210 THE PRACTICAL METAL-WORKER’S ASSISTANT. CHAPTER XIII. REMARKS ON THE CHARACTERS OF THE METALS AND ALLOYS. Hardness, Fracture, and Color of Alloys. —The object of the present chapter is to explain in a general way some of the pe¬ culiarities and differences amongst alloys, prior to entering on the means of melting the metals, without which process alloys cannot be made: yet notwithstanding that the list contains the greater number of the alloys in ordinary use, and many others, it is merely a small fraction of those which might be made. It is also stated that metals appear to unite with one another in every proportion, precisely in the same manner as sulphuric acid and water. Thus there is no limit to the number of alloys of gold and copper. The same might be said of many other metals, and when the alloys compounded of three, four, or more metals, are taken into account, the conceivable number of alloys becomes almost unlimited. It is certain, however, that metals have a tendency to combine in definite proportion; for several atomic compounds of this kind occur native. It is indeed possible that the variety of proportions in alloys is rather apparent than real, arising from the mixture of a few definite compounds with each other, or with un¬ combined metal; an opinion not only suggested by the mode in which alloys are prepared, but in some measure supported by observation. It appears to be scarcely possible to give any sufficiently general rules, by which the properties of alloys may be safely inferred from those of their constituents; for although, in many cases, the work¬ ing qualities and appearance of an alloy, may be nearly a mean proportional between the nature and quantities of the metals com¬ posing it; yet in other and frequent instances the deviations are excessive, as will be seen by several of the examples referred to. Thus, when lead, a soft and malleable metal, is combined with antimony, which is hard, brittle, and crystalline, in the proportions of from twelve to fifty parts of lead to one of antimony; a flexible alloy is obtained, resembling lead, but somewhat harder, and which is rolled into sheets for sheathing ships. Six parts of lead and one of antimony are used for the large soft printers’ types, which will bend slightly, but are considerably harder than the foregoing; and three parts of lead and one of antimony are employed for the small¬ est types, that are very hard and brittle, and will not bend at all; antimony being the more expensive metal, is used in the smallest quantity that will suffice. In this alloy the antimony fulfills another service besides that of .inparting hardness: antimony somewhat expands on cooling, CHARACTERS OF METALS AND ALLOYS. 211 whereas lead contracts very much, and the antimony, therefore, within certain limits, compensates for this contraction, and causes the alloy to retain the full size of the moulds. Sometimes, from motives of economy, the neighboring parts of machinery are not wrought accurately to correspond one with the other, but lead is poured in to fill up the intermediate space, and to make contact; as around the brass nuts in the heads of some screw presses, in the guides or followers for the same, and some other parts of either temporary or permanent machinery. Anti¬ mony is quite essential in all these cases to prevent the contraction the lead alone would sustain, and which would defeat the intended object, as the metal would otherwise become smaller than the space to be filled. A little tin is commonly introduced into types, and likewise cop¬ per in minute quantity; iron and bismuth are also spoken of; the last is said to be employed on account of its well-known property of expanding in cooling, so as to cause the types to swell in the mould, and copy the face of the letter more perfectly, but although I find bismuth to have been thus used it appears to be neither common nor essential in printing-types. The difference in specific gravity between lead and antimony constantly interferes, and unless the type metal is frequently stirred, the lead, from being the heavier metal, sinks to the bottom, and the antimony is disproportionally used from the surface. In the above examples, the differences arising from the propor¬ tions appear intelligible enough, as when the soft lead prevails, the mixture is much like the lead; and as the hard, brittle antimony is increased, the alloy becomes hardened, and more brittle: with the proportion of four to one, the fracture is neither reluctant like that of lead, nor foliated like antimony, but assumes very nearly the grain and color of some kinds of steel and cast-iron. In like man¬ ner, when tin and lead are alloyed, the former metal imparts to the mixture some of its hardness, whiteness, and fusibility, in propor¬ tion to its quantity; as seen in the various qualities of pewter, in which however copper, and sometimes zinc or antimony are found. The same agreement is not always met with; as nine parts of copper, which is red, and one part of tin, which is white, each very malleable and ductile metals, make the tough, rigid metal used in brass ordnance, from which it obtains its modern name of gun- metal, but which neither admits of rolling nor drawing into wire; the same alloy is described by Pliny as the soft bronze of his day. The continual addition of the tin, the softer metal, produces a gradual increase of hardness in the mixture; with about one-sixth of tin the alloy assumes its maximum hardness consistent with its application to mechanical uses; with one-fourth to one-third tin it becomes highly elastic and sonorous, and its brittleness rather than its hardness is greatly increased. When the copper becomes two, and the tin one part, the alloy is so hard as not to admit of being cut with steel tools, but crumbles 212 THE PRACTICAL METAL-WORKER’S ASSISTANT. Tinder tlieir action; when struck with a hammer or even suddenly warmed it flies in pieces like glass, and clearly shows a structure highly crystalline, instead of malleable. The alloy has no trace of the red color of the copper, but it is quite white, susceptible of an exquisite polish, and being little disposed to tarnish, it is most per¬ fectly adapted to tbe reflecting speculums of telescopes and other instruments, for which purpose it is alone used. Copper, when combined in the same proportions with a different metal, also light-colored and fusible, namely, two parts of copper, with one of zinc, (which latter metal is of a bluish-white, and crys¬ talline, whereas tin is very ductile,) makes an alloy of entirely oppo¬ site character to the speculum metal; namely, the soft yellow brass, which becomes by hammering very elastic and ductile, and is very easily cut and filed. Again, the same proportions, namely, two parts of copper and one of lead, make a common inferior metal, called pot-metal, or cock-metal, from its employment in those respective articles. This alloy is much softer than brass, and hardly possesses malleability; when, for example, the beer-tap is driven into the cask, immediately after it has been scalded, the blow occasionally breaks it in pieces, from its reduced cohesion. Another proof of the inferior attachment of the copper and lead exists in the fact that, if the moulds are opened before the castings are almost cold enough to be handled, the lead will ooze out and appear on the surface in globules. This also occurs to a less extent in gun-metal, which should not on that account be too rapidly ex¬ posed to the air; or the tin strikes to the surface, as it is called, and makes it particularly hard at those parts, from the proportional in¬ crease of the tin. In casting large masses of gun-metal, it frequently happens that little hard lumps, consisting of nearly half tin, work up to the surface of the runners or pouring places, during the time the metal is cooling. In brass, this separation scarcely happens, and these moulds may be opened whilst the castings are red hot, without such occurrence; from which it appears that the copper and zinc are in more perfect chemical union than the alloys of copper with tin and with lead. Malleability and Ductility of Alloys.— The malleability and ductility of alloys are in a great measure referable to the de¬ grees in which the metals of which they are respectively composed, possess these characters. Lead and tin are malleable, flexible, ductile, and inelastic whilst cold, but when their temperatures much exceed about half way to¬ wards their melting heats they are exceedingly brittle and tender, owing to their reduced cohesion. The alloys of lead and tin partake of the general nature of these two metals; they are flexible when cold, even with certain addi¬ tions of the brittle metals, antimony and bismuth, or of the fluid metal mercury; but they crumble with a small elevation of tempera¬ ture, as these alloys melt at a lower degree than either of their CHARACTERS OF METALS AND ALLOYS. 213 components, to which circumstance we are indebted for the tin solders. Zinc, when cast in thin cakes, is somewhat brittle when cold, but its toughness is so far increased when it is raised to about 300° F. that its manufacture into sheets by means of rollers is then admissi¬ ble ; it becomes the malleable zinc, and retains the malleable and ductile character, in a moderate degree, even when cold, but in bending rather thick plates it is advisable to warm them to avoid fracture; when zinc is remelted, it resumes its original crystalline condition. It is considered that most of the sheet zinc contains a very little lead. Zinc and lead will not combine without the assistance of arsenic, unless the lead is in very small quantity. The arsenic makes this and other alloys very brittle, and it is besides dangerous to use. Zinc and tin make, as may be supposed, somewhat hard and brittle alloys, but none of the zinc alloys, except that with copper to con¬ stitute brass, are much used. Gold, silver, and copper, which are greatly superior in strength to the fusible metals above named, may be forged either when red- hot or cold, as soon as they have been purified from their earthy matters, and fused into ingots; and the alloys of gold, silver, and copper, are also malleable, either red-hot or cold. Fine, or pure gold and silver, are but little used alone. The alloy is in many cases introduced less with the view of depreciating their value than of adding to their hardness, tenacity, and duc¬ tility. The processes which the most severely test these qualities, namely, drawing the finest wires, and beating gold and silver leaf, are not performed with the pure metals, but gold is alloyed with copper for the red tint, with silver for the green, and with both for intermediate shades. Silver is alloyed with copper only, and when the quantity is small its color suffers but slightly from the addition, although its working qualities are greatly improved, pure silver being little used. The alloys of similar metals having been considered, it only re¬ mains to observe that when dissimilar metals are combined, as those of the two opposite groups; namely, the fusible lead, tin, or zinc, with the less fusible copper, gold, and silver, the malleability of the alloys when cold is less than that of the superior metal; and when heated barely to redness, they fly in pieces under the hammer ; and, therefore, brass, gun-metal, etc., when red-hot, must be treated with precaution and tenderness. It will be remembered the action of rollers is more regular than that of the hammer, and soon gives rise to the fibrous character, which, so far as it exists in metals, is the very element of strength when it is uniformly distributed throughout their substance. This will be seen by the inspection of the relative degrees of cohesion possessed by the same metal when in the conditions of the casting, sheet, or wire, shown by the table, and to which quality or the tenacity of the alloys we shall now devote a few lines. 214 THE PRACTICAL METAL-WORKER’S ASSISTANT. Strength or Cohesion of Alloys. —The strength or cohesion of the alloys is in general greatly superior to that of any of the metals of which they are composed. For example, on comparing some of the numbers of the table on pages 206 and 208, it will be seen that the relative weights, which tear asunder a bar one inch square of the several substances, stand as follows,—all the num¬ bers being selected from Muschenbroek’s valuable investigations, so that it may be presumed the same metals, and also the same means of trial, were used in every case. Alloys. Cast Metals. 10 Copper, 1 Tin, 32,093 lbs. 8 — 1 — 36,088 “ 6 — 1 — 44.071 “ 4 — 1 — 35,739 “ 2 — 1 — 1,017 “ 1 — 1 — 725 “ Barbary Copper, 22,570 lbs. Japan — 20,272 “ English Block Tin, 6,650 Do. — 5,322 Banca Tin, 3,679 Malacca Tin, 3,211 The inspection of these numbers is highly conclusive, and it shows that the engineer agrees with theory and experiment in selecting the proportion 6 to 1 as the strongest alloy ; and that the philosopher, in choosing the most reflective mixture, employs the weakest but one,—its strength being only one-third to one-sixth that of the tin, or one-twentieth that of the copper, which latter constitutes two-thirds its amount. It is much to be regretted that the valuable labors of Muschen- broek have not been followed up by other experiments upon the alloys in more general use. One curious circumstance will be ob¬ served, however, in those which are given, namely, that in the following alloys, which are the strongest of their respective groups, the tin is always four times the quantity of the other metal; and they all confirm the circumstance of the alloys having mostly a greater degree of cohesion than the stronger of their component metals. Alloys. Cast Metals. 4 English Tin, 1 4 Banca Tin, 1 4 — — 1 4 English Tin, 1 4 — — 1 Lead, 10,607 lbs. Antimony, 13,480 “ Bismuth, 16,692 “ Goslar Zinc, 10,258 “* Antimony, 11,323 “ • Lead, 885 lbs. ' Antimony, 1,060 “ • Zinc, 2,689 “ • Bismuth, 3,008 “ . Tin, 3,211 to 6,650 “ Fig. 118 represents a very ingenious instrument, denominated an alloy-balance. It is intended for weighing those metals the propor¬ tions of which are stated decimally: its principle, which is so simple as hardly to require explanation, depends upon the law that weights in equilibrium are inversely as their distances from the point of support. For weighing out any precise number of pounds or ounces, in the common way, the arms of the ordinary scale-beam are made as * This, in truth, is an exception ; it barely equals in strength the alloys with 8 and 2 parts of tin to 1 of zinc, but is superior to that of equal parts. It corroborates the great increase of strength in alloys generally. CHARACTERS OF METALS AND ALLOYS. 215 nearly equal as possible; so that the weights, and the articles to be weighed, may be made to change places, in proof of the equality of the Fig. 118. instrument. But to weigh out an alloy, say of 17 parts tin and 83 copper, unless the quantities were either 17 and 83 lbs. or ounces, would require a little calculation. This is obviated, if the point of suspension a, of the alloy-balance, which is hung from any fixed support b, is adjusted until the arms are respectively as 17 to 83 ; and for this purpose the half of the beam is divided into fifty equal parts numbered from the one end; and, prior to use, it only remains to adjust the weight, w, so as to place the empty balance in equilibrium. A quantity of copper, rudely estimated, having been suspended from the short arm of the balance, the proportionate quantity qf the tin will be denoted with critical accuracy, when, by its gradual addition, the beam is exactly restored to the horizontal line; should the alloy consist of three or more parts, the process of weighing is somewhat more complex. The annexed table was calculated by the author, for converting the proportions of alloys stated decimally, into avoirdupois weight. It applies with equal facility to alloys containing two or many compo¬ nents, so as to bring them readily within the power of ordinary scale? 216 THE PRACTICAL METAL-WORKER’S ASSISTANT. TABLE FOR CONVERTING DECIMAL PROPORTIONS Into Divisions of the Pound Avoirdupois. Decimal. OZ. dr. Decimal. oz. dr. Decimal. oz. dr. Decimal. oz. dr. .78 l 13.28 2 1 25.78 4 i 38.28 6 1 1.56 2 14.06 2 2 26.56 4 2 39.06 6 2 2.34 3 14.84 2 3 27.34 4 3 39.84 6 3 3.12 4 15.62 2 4 28.12 4 4 40.62 6 4 3.91 5 16.4 L 2 5 28.91 4 5 41.41 6 5 4.69 6 17.19 2 6 29.69 4 6 42.19 6 6 5.47 7 17.97 2 7 30.47 4 7 42.97 6 7 6.25 1 0 18.75 3 0 31.25 5 0 43.75 7 0 7.03 1 1 19.53 3 1 32.03 5 1 44.53 7 1 7.81 1 2 20.31 3 2 32.81 5 2 45.31 7 2 8.59 1 3 21.09 3 3 33.59 5 3 46.09 7 3 9.37 1 4 21.87 3 4 34.37 5 4 46.87 7 4 10.16 1 5 22.66 3 5 35.16 5 5 47.66 7 5 10.94 1 6 23.44 3 6 35.94 5 6 48.44 7 6 11.72 1 7 24.22 3 7 36.72 5 7 49.22 7 7 12.50 2 0 25.06 4 0 37.50 6 0 50.00 8 0 Application of the Table. The Chinese consist of— 40.4 parts of 25.4 — 31.6 — 2.6 — Packfong, similar to our German silver, is said to Copper 1 Zinc ! Nickel j Iron equivalent to 100.0 parts 16 oz. 0 — Avoird’s. All nice attempts at proportion are, however, entirely futile, un¬ less the metals are perfectly pure; for example, it is a matter of common observation that for speculums a variable quantity of from seven and a half to eight and a half ounces of tin is required for the exact saturation of every pound of copper, and upon which saturation the efficiency of the compound depends; bells of exactly similar quality sometimes thus require the dose of tin to vary from three and a half to five ounces to the pound of copper, according to the qualities of the metals. The variations in the purity of the metals obtained from different localities are abundantly demonstrated by the disagreement in the cohesive strengths of the two in question, more particularly the tin, as seen on page 214, and which can be only ascribed to their re¬ spective amounts of impurity. Any other supposition than the CHARACTERS OF METALS AND ALLOYS. 217 presence of foreign matter, would necessarily go to disprove the fact of the metals being simple bodies, and therefore strictly alike when absolutely pure, wheresoever they may have been obtained. Fusibility of Alloys.— In concluding this slight view of some of the general characters of alloys, it remains to consider the influ¬ ence of heat, both as an agent in their formation and as regards the degree in which it is required for their after-fusion; the lowest available temperature being the most desirable in every such case. Metals do not combine with each other in their solid state, owing to the influence of chemical affinity being counteracted by the force of cohesion. It is necessary to liquefy at least one of them, in which case they always unite, provided their mutual attraction is energetic. Thus, brass is formed when pieces of copper are put into melted zinc; and gold unites with mercury at common tem¬ peratures by mere contact. The agency of mercury in bringing about triple combinations of the metals, both with and without heat, is also very curious and extensive. Thus, in water-gilding , the silver, copper, or gilding metal, when chemically clean, is rubbed over with an amalgam of gold containing about eight parts of mercury; this immediately attaches itself, and it is only necessary to evaporate the mercury, which requires a very moderate heat, and the gold is left behind. Water-silvering is similarly accomplished. Cast-iron, wrought-iron, and steel, as well as copper and many other metals, may be tinned in a similar manner. An amalgam of tin and mercury is made so as to be soft and just friable; the metal to be tinned is thoroughly cleaned, either by filing or turning, or if only tarnished by exposure, it is cleaned with a piece of emery- paper or otherwise, without oil, and then rubbed with a thick cloth moistened with a few drops of muriatic acid. A little of the amal¬ gam then rubbed on with the same rag, thoroughly coats the cleaned parts of the metal by a process which is described as cold-tinning ; other pieces of metal may be attached to the tinned parts by the ordinary process of tin-soldering. In making the tinned iron plates, the scoured and cleaned iron plates are immersed in a bath of pure melted tin, covered wifrh pure tallow, the tin then unites with every part of the surfaces; and in the ordinary practice of tinning culinary vessels of copper, pure tin is also used. The two metals, however, must then be raised to the melting heat of tin; but the presence of a little mercury enables the process to be executed at the atmospheric temperature, as above explained. In M. Mallet’s recently patented processes for the protection of iron from oxidation and corrosion, and for the prevention of the fouling of ships, one proceeding consists in covering the iron with zinc. The ribs or plates for iron ships are immersed in a cleansing bath of equal parts of sulphuric or muriatic acid and water, used warm; the works are then hammered, and scrubbed with emery or sand. 218 THE PRACTICAL METAL-WORKER’S ASSISTANT. to detach the scales and to thoroughly clean them; they are then immersed in a preparing bath of equal parts of saturated solutions of muriate of zinc and sal-ammoniac, from which the works are transferred to a fluid metallic bath, consisting of 202 parts of mer¬ cury and 1292 parts of zinc, both by weight (being in the proportion of one atom of mercury to forty atoms of zinc); to every ton weight of which alloy, is added about one pound of either potassium or sodium (the metallic bases of potash and soda), the latter being preferred. As soon as the cleaned iron works have attained the melting heat of the triple alloy, they are removed, having become thoroughly coated with zinc. The affinity of this alloy for iron is, however, so intense, and the peculiar circumstances of surface as induced upon the iron presented to it by the preparing bath are such, that care is requisite least by too long an immersion the plates are not partially or wholly dissolved. Indeed where the articles to be covered are small, or their parts minute, such as wire, nails or small chain, it is necessary before immersing them to permit the triple alloy to dissolve or combine with some wrought-iron, in order that its affinity for iron may be partially satisfied and thus diminished. At the proper fusing temperature of this alloy, which is about 680° Fahr., it will dissolve a plate of wrought-iron of an eighth of an inch thick in a few seconds. The Palladiumizing Process .—The articles to be protected are to be first cleansed in the same way as in the case of zincing; namely, by means of the double salts of zinc and ammonia, or of manganese and ammonia; and then to be thinly coated over with palladium, applied in a state of amalgam with mercury. In the opinion of eminent chemists and metallurgists, all the met¬ als, even the most refractory which nearly, or quite refuse to melt in the crucible when alone, will gradually run down when sur¬ rounded by some of the more fusible metals in the fluid state; in a manner similar to the solution of the metals in mercury, as in the amalgams, or the solutions of solid salts in water. The surfaces of the superior metals are, as it were, dissolved, washed down, or re¬ duced to the state of alloys, layer by layer, until the entire mass is liquefied. Thus nickel, although it barely fuses alone, enters into the com¬ position of German silver by aid of the copper, and whilst it gives whiteness and hardness, it also renders the mixture less fusible. Platinum combines very readily with zinc, arsenic, and also with tin and other metals; so much so that it is dangerous to melt either of those metals in a platinum spoon; or to solder platinum with common tin solder, which fuses at a very low temperature : although platinum is constantly soldered with fine gold, the melting point of which is very high in the scale. Again, the circumstances that some of the fusible bismuth alloys melt below the temperature of boiling water, or at less than half the melting heat of tin, their most fusible ingredient, show that the points of fusion of alloys are CHARACTERS OF METALS AND ALLOYS. 219 equally as difficult of explanation or generalization as many other of the anomalous circumstances concerning them. This much, however, may be safely advanced, that alloys, without exception, are more easily fused than the superior metal of which they are composed; and extending the same view to the relative quantities of the components, it may be observed that the hard solders for the various metals and alloys, are in general made of the self-same material which they are intended to join, but with small additions of the more fusible metals. The solder should be, as nearly as practicable; equal to the metal on which it is employed, in hardness, color, and every property except fusibility ; in which it must excel just to an extent that, when ordinary care is used, will avoid the risk of melting at the same time, both the object to be soldered and likewise the softer alloy or solder by which it is intended to unite its parts It would appear as if every example of soldering in which a more fusible alloy is interposed, were also one of superficial alloying. Thus, when two pieces of iron are united by copper, used as a sol¬ der, it seems to be a natural conclusion that each surface of the iron becomes alloyed with the copper: and that the two alloyed surfaces are held together from their particles having been fused in contact, and run into one film. It is much the same when brass or spelter solder is used, except that triple alloys are then formed at the sur¬ faces of the iron, and so with most other instances of soldering. And in cases where metallic surfaces are coated by other metals,, the latter being at the time in a state of fusion, as in tinned-iron plates and silvered copper; may it not also be conceived, that be¬ tween the two exterior surfaces, which are doubtless the simple metals, a thin film of an alloy compounded of the two does in reality exist ? And in those cases in which the coating is laid on by the aid of mercury, and without heat, the circumstances are very sim¬ ilar, as the fluidity of mercury is identical with the ordinary state of fusion of other metals, although the latter require higher tem¬ peratures than that of our atmosphere. When portions of the same metal are united by partial fusion, and without solder, as in the process described as burning together, and more recently known as the “ autogenous ” mode of soldering, no alloy is formed, as the metals simply fuse together at their surfaces. Neither can it be supposed that any formation of alloy can occur, where the one metal is attached to the other by the act of burnishing on with heat, as in making gilt wire, but without a temperature sufficient to fuse either of the metals. The union in this case is probably mechanical, and caused by the respective par¬ ticles or crystals of the one metal being forced into the pores of the other, and becoming attached by a species of entanglement, similar to that which may be conceived to exist throughout solid bodies. This process, almost more than any other in common use, requires that the metals should be perfectly or chemically clean; 220 THE PRACTICAL METAL-WORKER’S ASSISTANT. for which purpose they are scraped quite bright before they are burnished together, so that the junction may be next approaching to that of solids generally. And, lastly, when metals are deposited upon other metals by chemical or electrical means, the addition frequently appears to be a detached sheath, and which is easily removed; indeed, unless the metal to be coated is chemically clean, and that various attendant circumstances are favorable, the sound and absolute union of the two does not always happen, even when carefully aimed at. It is time, however, that we proceed to the description of the methods of forming the ordinary alloys, the subject of the succeed¬ ing matter. CHAPTER XIY. MELTING AND MIXING THE METALS. The various Furnaces, etc., for Melting the Metals.— The subject upon which we have now to enter consists of two principal divisions, namely, the melting and combining of the met¬ als, and the formation of the moulds into which the fluid metals are to be poured. In the foundry the two processes are generally carried on together, so that by the time the mould is completed, the metal may be ready to be poured into it; but as in conveying these several particulars the one process must have precedence, I propose to commence with the means ordinarily employed in melt¬ ing and mixing the metals, in order to associate more closely all that concerns the alloys. In accordance with ordinary practice, the formation of the moulds will be described whilst the metals may be supposed to be in course of fusion; the concluding re¬ marks will be on pouring, or filling the moulds, the act strictly speaking of casting, and which completes the work. The fusible metals, or those not requiring the red-heat, are melted when in small quantities in the ordinary plumber’s ladle over the fire; otherwise larger cast-iron ladles or pans are used, beneath which a fire is lighted ; for very large quantities and various manu¬ facturing purposes, such as casting sheet-lead, and lead pipe, and also for type-founding, the metals are melted in iron pans set in brickwork, with a fire-place and ash-pit beneath, much the same as an ordinary laundry copper, and the metals are removed from the pans with ladles. The pewterers and some others call the melting pan a pit. although it is erected entirely above the floor ; and as their meltings are made up in great part of old metal, which is sometimes wet or damp, they have iron doors to enclose the mouth of the pan, in MELTING AND MIXING THE METALS. 221 case any of the metal sliould be splashed about from the moisture reaching the fluid metal. Antimony, copper, gold, silver, and their alloys, are for the most part melted in crucibles within furnaces similar to the kind used by the brass founders, which is represented at a, Fig. 119; the en¬ tire figure represents the imaginary section of a brass foundry with the moulding trough, b, for the sand on the side opposite the furnace, the pouring or spill trough, c, in the centre, and the core oven d, which is usually built in the wall close against one of the flues; but these matters will be described hereafter. The brass furnace is usually built within a cast-iron cylinder, about 20 to 24 inches diameter and 30 to 40 inches high, which is erected over an ash-pit arrived at through a loose grating on a level with the floor of the foundry. The mouth of the furnace Fig. 119. stands about 8 or 10 inches above the floor, and its central aper ture is closed with a plate now usually of iron, although still called a tile; the inside of the furnace is contracted to about 10 inches diameter by fire-bricks set in Stourbridge clay, except a small aperture at the back about 4 or 5 inches square, leading into the chimney. There are generally three or four such furnaces standing in a row, and separate flues proceed from all into the great chimney or stack, the height of which varies from about twenty to forty feet, and up¬ wards, the more lofty it is the greater the draught; every furnace has also a damper to regulate its individual fire. It is quite essential for constant work to have several furnaces, in order that one or two may be in use, whilst the others lie idle to allow of their being repaired, as they rapidly burn away, and when the space around the crucible exceeds about 2 or 3 inches, the fuel is consumed unnecessarily quick; the furnace is then contracted to its original size with a dressing of road drift and water applied 222 TPIE PRACTICAL METAL-WORKER’S ASSISTANT. ✓ like mortar, the fire is lighted immediately, and urged vigorously to glaze the lining. Road drift, or the scrapings of the ordinary turn-pike roads, principally silex and alumina, is often used for the entire lining of the furnaces. The refuse sand from the glass grinders, which contain flint glass, is also used for repairing them. It is also convenient to have several furnaces for another reason, as when a single casting requires more than the usual charge of one furnace, namely, about 40 to 60 lbs., two or more fires can be used. When the quantity of brass to be melted exceeds the charge of three or four ordinary air furnaces, the common blast furnace for iron is sometimes used as a temporary expedient; the practice, however, is bad, as it causes great oxidation and waste. The greatest quantities of metal, as for large bells, statues, and ordnance, amounting sometimes to several tons, are commonly melted in re¬ verberatory furnaces. The furnaces used by the gold and silver refiners are in many respects similar to the brass burnace a, Fig. 119, but they are built as a stunted wall along one or more sides of the refinery, and en¬ tirely above the floor of the same. The several apertures for the fuel and crucible are from 9 to 16 inches square, or else cylindri¬ cal, and 12 to 20 inches deep ; the front edge of the wall is horizon¬ tal, and stands about 30 inches from the ground, but from the mouth of the furnace backwards it is inclined at an angle of about 20 to 40 degrees, so that the tiles, or the iron covers of the furnace, lie at that angle. A narrow ledge cast in the solid with the iron plates covering the upper surface of the wall, retains the tiles in their position. The small kinds of air furnaces are of easy construction, but as a temporary expedient almost any close fire may be used, including some of the German stoves and hot-air stoves, that is for melting brass, which is more fusible than copper; although it is much the most convenient that the fire be open at the top, so that the con¬ tents of the crucible may be seen without the necessity for its re¬ moval from the fire. Such stoves, however, radiate heat in a some¬ what inconvenient manner, and to a much greater extent than the various portable furnaces, most of which are lined with fire-brick or clay; the lining concentrates the heat and economizes the fuel. Many of these portable furnaces answer not only for copper but also for iron, when they have a good draft; it may happen, however, that the chemical furnaces are equally as inaccessible to the ama¬ teur as those expressly constructed for the metals. Country blacksmiths, who are frequently called upon to practice many trades, sometimes melt from ten to fifteen pounds of brass in the ordinary forge fire, but there is considerable risk of cracking the earthen crucible at the point exposed to the blast; a wrought- iron pot is sometimes resorted to, but this is not very enduring, as the brass will soon cause it to burn into holes and leak. Observations on the Management of the Furnace, and on Mixing Alloys. — The fuel for the brass furnace is always hard MELTING AND MIXING THE METALS. 223 coke, which, is prepared in ovens and broken into lumps about the size of hens’ eggs: in lighting the fire, a bundle of shavings, chips, of cork, or any similar combustible, is first thrown in and ignited, and then some coke or charcoal is added. It is also -usual to put the pot in the fire at an early stage, and with its month down¬ wards: by this means the thin edge which admits the most easily of expansion gets hot first, and the heat plays within the crucible, so as to warm it gradually: it is not reversed until the whole is red hot: putting it in bottom downwards would be almost certain to cause it to crack. The pot is now bedded upon the fuel, and. the brass-founder, whilst making up the fire, puts an iron cover with a long central handle over the mouth of the pot, to prevent the small cokes which are now thrown on from entering the same. Next, the charge of metal is put in the crucible, and three or four large pieces of coke are placed across the mouth of the pot; the tile is put on the fur¬ nace, the damper is then adjusted to heat the crucible quickly, and the whole is left to itself until the metal is run down. The gold and silver refiners and jewelers manage their furnaces much in the same way, except that they support the crucible upon a hollow earthen stand placed on the fire-bars to catch any leakage, and also put an earthen cover over its mouth. They generally use coke, although charcoal is a purer fuel, and is laid upon the fluid metals to prevent oxidation. The above, and the so-called blue pots, or black-lead pots, are not burned until they are put into the fire for use ; but the Hessian pots, the English brown or clay pots, the Cornish and the Wedgwood crucibles, are all burned before use. It may be further observed, that the pots for brass are too porous for gold and silver, as they suck up too much of the same: the black-lead pots are closer and better for the precious metals, and they withstand change of temperature best of any kind; they are however the most expensive, but cannot be safely used with fluxes. The Hessian crucibles resist the fluxes, and serve with care for several consecutive meltings; the English clay pots, which resem¬ ble the Hessian, are safe for one or sometimes for more meltings, and their cost is trifling. The pots for gold and silver are occasion¬ ally coated or luted externally with clay as a protection. The generality of the metals are far more disposed to oxidation when in the melted condition than when solid; it is therefore usual, whilst they are in the crucible, to protect their surfaces from the air with some flux, to lessen their disposition to oxidize. In the iron furnace, the slag from the lime floats on the metal and fulfils this end; many brass-founders always throw broken glass, charcoal dust, sandiver, or sal-enixon, into the melting pot; by others these precautionary measures are altogether neglected. The black and white fluxes, borax, and saltpetre are also used for the precious metals, and oil or resin for the more fusible, as lead or tin; but excess of heat should be at all times avoided. 224 THE PRACTICAL METALWORKER'S ASSISTANT. The generality of the fusible metals may be mixed in all pro¬ portions. Those in which the melting points are tolerably similar may be easily combined, such as lead with tin, or gold with silver or copper ; these appear to call for no instructions beyond modera¬ tion in the heat employed, but the difficulty of making definite and uniform alloys increases when the melting point of the metals, or their qualities or quantities, are widely dissimilar. In mixing alloys with new metals, it is usual to melt the less fusible first, and subsequently to add the more fusible; the mix¬ ture is then stirred well together, and common opinion seems to be in favor of running the metal into an ingot mould, as the second fusion is considered more thoroughly to incorporate the mixture. Sometimes, with the same view, the alloy is granulated, by pouring it from the crucible into water, either from a considerable height through a colander, or over a bundle of birch twigs, which subdi¬ vide it into small pieces; others condemn such practices, and greatly prefer the first fusion, in order to avoid oxidation, and de¬ parture from the intended proportions. But in many, and perhaps in most cases, it is the practice to fill the melting pan, or the crucible, in part with old alloy, consisting of fragments of spoiled or worn-out work; and to which is added, partly by calculation but principally by trial, a certain quantity of new metals. This is not always done from motives of economy alone, but from the opinion that such mixtures cast and work better than those made entirely of new metals. When small quantities of metal of difficult fusion, are added to large proportions of others which are much more fusible, the whole quantities are not mixed at once. Thus in pewter, it would be scarcely possible to throw into the melted tin the half per cent, or the one per cent, of melted copper with any certainty of the two combining properly, and it is therefore usual to melt the copper in a crucible, and to add to it two or three times its weight of melted tin; this, as it were, dilutes the copper, and makes the alloys known as temper, which may be fused in a ladle, and added in small quantities to the fluid pewter or to the tin, as the case may be, until on trying the mixture by the assay its proportions are con¬ sidered suitable. The metal for printers’ type is often mixed nearly in the same manner; the copper is first melted alone in a crucible, the anti¬ mony is melted in another crucible, and is poured into the copper ; sometimes a little lead is also added. The hard alloy and the tin are then introduced to the mass of type-metal or lead, also in great measure by trial, as old metal mostly enters into the mixture. The composition of Britannia metal is as follows: 3J cwt. of best block tin ; 28 lbs. of martial regulus of antimony ; 8 lbs. of copper, and 8 lbs. of brass. The amalgamation of these metals is effected by melting the tin, and raising it just to a red heat in a stout cast-iron pot or trough, and then pouring into it, first the regulus, and afterwards the copper and brass, from the crucibles MELTING AND MIXING THE METALS. 225 in which they have "been respectively melted, the caster meanwhile stirring the mass about during this operation, in order that the mixture may be complete. It would appear, however, much more likely and consistent that a similar mode is adopted in making this alloy, as in pewter and type-metal; namely, that the copper and brass are melted together in one crucible, the antimony then added from another crucible, and perhaps also a little tin; this would dilute the hard metals, and make a fusible compound, to be added to the remainder of the tin when raised a very little beyond its fusing point, so as to maintain fluidity when the whole were mixed and stirred together, pre¬ viously to being poured into ingots. By this treatment the tin would be much less exposed to waste. When a very oxidizable or volatile metal, as zinc, is mixed with another metal the fusing point of which is greatly higher, as with copper for making the important alloy brass, whatever weight of each may be put into the crucible, it is scarcely possible to speak with any thing like certainty of the proportions of the alloy pro¬ duced, from the rapid and nearly uncontrollable manner in which the waste of the zinc occurs. Various means have been devised at different times for combin¬ ing these two metals. Although the most direct way of forming the different kinds of brass is by immediately combining the metals together, one of them, which is most properly called brass, was manufactured long before zinc, one of its component parts, was known in its metallic form. The ore of the latter metal was cemented with sheets of copper, charcoal being present. The zinc was formed and united with the copper, without becoming visible in a distinct form. The same method is still practised for making brass. The best way of uniting zinc with copper, in the first instance, will be to introduce the copper in thin slips into the melted zinc, till the alloy requires a tolerable heat to fuse it, and then to unite it with the melted copper. Some persons thrust the whale of the copper, in thin plates, into the melted zinc, which rapidly dissolves them; and the mass is kept in a pasty condition until within a few minutes of the time of pouring, when they augment the heat to the degree required for the casting process. But the plan which is the most expeditious, and now most usu¬ ally adopted, is to thrust the broken lumps of zinc beneath the surface of the melted copper with the tongs, which mode will be more particularly described ; but howsoever conducted, a consid¬ erable waste of the zinc will inevitably occur. It is also certain that every successive fusion wastes, in some degree, the more oxidizable metal, so that the original proportion is more and more departed from, especially with the least excess oi' heat; and when the metals are not well covered with flux. The loose oxide frequently mixes with the metal; this in brass gives 15 226 THE PRACTICAL METAL-WORKER’S ASSISTANT. rise to the white-colored stains, and the little cavities tilled with the white oxide of zinc; and in gun-metal the stains and streaks are blacker, and the oxide of tin (or putty powder) being much harder than the former, is sadly destructive to the tools. The vitreous fluxes collect these oxides, and are therefore serviceable ; but when in excess, they are liable to run into the mould w r hen the metal is poured. The chemist generally uses covers to the cruci¬ bles, to lessen the access of air, and therefore the oxidation; but the brass-founder frequently leaves the metal entirely uncovered. No considerable waste occurs until the metal is entirely fused and rather hotter than is required for pouring, which is indicated by the zinc beginning to burn at the surface with a blue flame. The loss which occurs in melting brass-filings is a proof that the granulation of the metals is not always desirable ; and unless the brass-filings are w r ell drown, by a group of magnets, to free them from particles of iron and steel, the latter often spoil the cast¬ ings, as they become so exceedingly hard as to resist the file or turning-tool, and can be only removed by the hammer and cold- chisel. In collecting the several alloys given at pages 180 to 203, espec¬ ially those of copper, I found great difficulty in reconciling many of the statements derived from books; and therefore, to place the matter upon a surer basis, and also with some other views, I de termined to mix a series of the copper alloys, in quantities of from one to two pounds each, pursuing, as nearly as possible, the com mon course of foundry work, to make the results practical and useful. My first intention was to weigh the metals into the crucible, and to find, by the weight of the product, the amount of loss in every case, as well as the quality of the alloy. Commencing with this view, with copper and zinc, the several attempts entirely failed, owing to the extremely volatile nature of the latter metal, espec¬ ially when exposed to the high temperature of melted copper. The difficulty was greatly increased owing to the very large extent of surface exposed to the air compared with that which occurs when greater quantities are dealt with, and the increased rapidity with which the whole was cooled. The zinc was added to the melted copper in various ways, namely,—in solid lumps, in thin sheets hammered into balls, poured in when melted in an iron ladle: and all these, both whilst the crueible was in the fire and after its removal from the same. The surface of the copper was in some cases covered with glass or charcoal, and in others uncovered, but all to no purpose, as from •one-eighth to one-half the zinc was consumed with most vexatious brilliancy, according to the modes of treatment: and these methods were therefore abandoned as hopeless. I was the more diverted from the above attempts by the well- known fact that the greatest loss always occurs in the first mixing of the two metals, and which the founder is in general anxious to MELTING AND MIXING THE METALS. 227 avoid. Thus, when a very small quantity of zinc is required, as for the so-called copper casting, about 4 oz. of brass are added to every 2 or 3 lbs. of copper. And in ordinary work, a pot of brass weighing 40 lbs. is made up of 10, 20, or 30 lbs. of old brass, and two-thirds of the remainder of copper. These are first melted. A short time before pouring, the one-third of the new metals, or the zinc, is plunged in when the temperature of the mass is such that it just avoids sticking to the iron rod with which it is stirred. In mixing the copper and zinc for my experiments on brass, an entirely different course was therefore determined upon, namely, to melt the metals on a large scale, and in the usual proportion— that is, 24 lbs. of copper to 12 lbs. of zinc—to learn the first loss of zinc when conducted with ordinary care. Then to remelt a quantity of the alloy over and over again, taking a trial-bar every time in order to ascertain the average loss of zinc in every fusion. From the residue of' the original mixture, to make the alloys con¬ taining less zinc, by a proportional addition of copper ; and those alloys containing more zinc, by a similar addition of zinc. And lastly, to have the whole of the bars assayed, to determine the ab¬ solute proportion of copper and zinc contained in all, and from these analyses to select my series of specimens, as nearly in agree¬ ment as I could with the proportions in common use. This method answered every expectation. Twenty-four pounds of copper, namely, clean ship’s bolts, were first melted alone to ascertain the loss sustained by passing through the fire, which was found to be barely ^ oz. on the whole. A simi¬ lar weight of the same copper was weighed out, and also 12 lbs. of the best Hamburg zinc, in cakes about f inch thick, which were broken into pieces. The copper was first melted, and when the whole was nearly run down the coke was removed to expose the top of the pot, which was watched until the boiling of the copper, arising probably from escape of bubbles of air locked up at the lower part of the semi-fluid mass, ceased, and the copper assumed a bright red but sluggish appearance. The zinc was then added. Precaution is necessary in introducing the first quantity of zinc not to set the copper, which is liable to occur if a large quantity of cold metal is thrown in, simply from the abstraction of heat; and it is also necessary to warm the zinc, that it may be perfectly dry, as the least moisture would drive the metal out of the pot with dangerous violence. A small lump of zinc, therefore, was taken in the tongs, held beside the pot for a few moments, and then put in with the tongs with an action between a stir and a plunge, regardless of the flare, and of the low crackling noise, just as if butter had been thrown in. The zinc was absorbed, and the sur¬ face of the pot was clear from its fumes almost immediately. The remainder of the zinc was then directly added, in about eight pieces, one at a time, much in the same manner, but the danger of setting the copper nearly ceases when a small quantity of the 228 THE PRACTICAL METAL-WORKERS ASSISTANT. spelter is introduced. After every addition the pot was free from flame in a few moments. A handful of broken glass was then thrown in, the tile replaced, and the whole allowed to stand for about fifteen minutes to raise the metal to the proper heat for pouring, which is denoted by the commencement of the blue fumes of the zinc. The pot was then taken from the fire, well stirred for one minute, and poured; the weight of the brass yielded was 34 lbs. 12| oz., showing a loss of 1 lb. 3| oz., or one-tenth of the zinc, or the one- thirtieth part of the whole quantity. This experiment was re¬ peated, and the loss was then 1 lb. 3 oz., the difl'erence being only 4 an oz. By analysis, the mean of the two brasses was 314 per cent, zinc ; or instead of being 8 oz. to the pound, it was only 71 oz. Twelve pounds of each of these experimental mixtures were re- melted six times, a bar weighing about one pound and a half'being taken every time; the two series of trials were conducted in differ¬ ent foundries, by different men, and quite in the ordinary course of work; but the loss per cent, of zinc was in the six experiments ex¬ actly alike in each series, that is, each bar, after the sixth melting, contained 22 \ per cent, or 4f oz. to the pound of copper. The second fusion in each case sustained the greatest loss, (say nearly two-fold;) and in the others, taking all the accidental circumstances into account, the loss might be pronounced nearly alike every fusion In making the alloys with more zinc; the calculated weight of the first alloy was melted, and the amount of zinc was warmed and plunged in with the tongs, whilst the pot was in the fire, the whole ■was stirred and quickly poured: the losses in weight were rather large, but this is common when the zinc is in great quantity. To make the alloys containing less zinc than the alloy, the calculated weight of copper was first made red-hot and the respective portion of the brass alloy was then put in the pot, by which means the two ran down nearly together: it being found that the copper, if en¬ tirely melted before the brass was added, incurred a risk of being set at the bottom of the pot; and remelting the mass, wasted the zinc. These alloys came out much nearer to their intended weights. In making the tin and copper alloys, very little difficulty was experienced. The copper was put into the pot together with a little charcoal, which was added to assist the fusion and also to cause the alloy to run clean out; as in pouring gun-metal a small quantity is usually left on the lip of the crucible, which would have been an interference in these experiments. When the copper had ceased boiling, and was at a bright red heat, it was taken from the fire, and the tin previously melted in a ladle, was thrown in; every mixture was well stirred and poured immediately. In the fourteen alloys thus formed, each weighing about a pound and a half, namely, 1, 1J, etc., up to 8 oz. of tin to the pound of copper, (missing the 6J and 7|,) no material loss was sustained in MELTING AND MIXING THE METALS. 229 nine instances, and in the other five it never exceeded | oz., and that quantity was probably lost rather in fragments than by oxidation. Alloys of 2, 4, 6 and 8 ounces of lead to the pound of copper, were made exactly under the same circumstances as the last. Messrs. Barron and Brother, of New York, manufacture a very effective and economical furnace, which supplies the necessary quantity of air; for in the combustion of fuel only a certain quantity of air is required, either an excess or deficiency is prejudicial to proper combustion. The metals are melted by this furnace in less time, and at a less expense of fuel than any that have fallen under my notice. In less than ten minutes, gold, silver, and copper can be melted by the furnace of Barron and Brother. The first size will melt from 4 to 12 ounces of gold with about a quart of coal; the second size will melt 50 to 120 ounces with about two quarts; and the third size will melt from 100 to 500 ounces with three or four quarts of coal. It is a difficulty of no ordinary description to ascertain the tem¬ perature of a furnace with sufficient accuracy. Every fire and every furnace is continually changing its temperature. When a furnace is charged with a fresh supply of fuel, its temperature is lowered by the absorption of heat which the cold fuel takes up when thrown upon the fire. The temperature is lowered by a rush of cold air through the open door. Experiments made by the pyrometer showing the mean temperature of the flues in a steam-engine boiler, and the effects produced by the admission of air through a permanent and regulated apparatus behind the bridge, indicate that in making the quantity of water evaporated by one pound of coal as the measure of economy, the mean of nearly the whole experiments is about 121 per cent, in favor of a regulated and continuous supply of air. In order to insure economy and effect in the combustion of fuel, a large supply of air must be admitted to the furnace, and that in the ratio of 10 volumes of air to 1 of coal gas. Perfect combustion is the prevention of smoke. And it is found that in order to render the residue of the products of combustion transparent or smokeless, a supply of air amounting to ten times the gases evolved must be admitted. 230 THE PRACTICAL METAL-WORKER’S ASSISTANT. CHAPTER XV. CASTING AND FOUNDING. Metallic Moulds.— We are indebted to the fusibility of the metals, for the power of giving them with great facility and per¬ fection, any required form, by pouring them whilst in the fluid state into moulds of various kinds, of which the castings become in general the exact counterparts. This property is of immeasurable value. Some few objects are cast in open moulds, so that the upper sur¬ face of the fluid metal assumes the horizontal position the same as other liquids, as in casting ingots, flat plates, and some few other objects; but in general the metals are cast in close moulds, so that it becomes necessary to provide one or more apertures or ingates for pouring in the metal, and for allowing the escape of the air which previously filled the moulds. When these moulds are made of metal, they must be sufficiently hot not to chill or solidify the fluid metal before it has time to adapt itself thoroughly to every part of the mould: and when the moulds are made of earthy matters, although moisture is essential to their formation, little or none should remain at the time they are filled. The earthen moulds must be also sufficiently pervious to air, that any vapor or gases which may be formed, either at the mo¬ ment of pouring in the metal or during its solidification, may have free vent to escape; otherwise, if these gases are rapidly formed, there is great danger of the metal being driven out of the mould with a violent explosion, or when more slowly formed and locked up without sufficient freedom for escape, the casting will be said to be blown, as some of the bubbles of air will displace the fluid metal and render it spongy or porous. It not unfrequently hap¬ pens that castings which appear externally good and sound, are full of hidden defects, because the surface being first cooled, the bubbles of air will attempt to break their way through the central and still soft parts of the casting. The explanatory diagram, Fig. 120, is intended to elucidate some of the circumstances concerning the construction of moulds, which in the greater number of cases are made only in two parts, but in other cases are divided into several. The figure to be moulded is supposed to be a rod of elliptical section, the mould for which might be divided into two parts through the line A, B, because no part of the figure projects beyond the lines a, b, drawn from the margin of the model at right angles to the line of division, and in which direction the half of the mould would be removed or lifted; the model could be afterwards drawn out from the second half of the mould in a similar manner. CASTING AND FOUNDING. 231 The mould could be also parted upon tlie line C, D, because in tbat direction likewise, no part of the model extends beyond tbe lines c, d, which show the direction in which the mould would be then lifted. Fig. 120. a C b The mould, however complex, could be also parted either upon A B or C D, provided no part of the model outstepped the rect¬ angle formed by the dotted lines b, c, or was undercut. But considering the figure 120 to be turned bottom upwards, and with the line E, F, horizontal, the removal of the entire half of the mould upon the lines e,f would be impossible, because in rais¬ ing the mould perpendicularly to E, F, that portion of the mould situated within the one perpendicular e, would catch against the overhanging part of the oval towards A. Were the mould of metal, and therefore rigid, it would be entirely locked fast, or it would not “ deliver were the mould of sand, and therefore yielding, it would break and leave behind that part between A and E which caused the obstruction. Consequently, in such a case, the mould would be made with a small loose part between A and E, so that when the principal portion, from A to F, had been lifted perpendic¬ ularly or in the direction of the line e, the small undercut piece, A to E, might be withdrawn sideways, on which account it would be designated by the iron founder a drawback, by the brass founder a false core. All the patterns in the mould, Fig. 121, could be extracted from each half the mould, because none of them encroach beyond the perpendicular line, or that in which the mould is lifted; a and b, could be laid in exactly upon the diagonal, or upon one flat side, or partly embedded; and in like manner f g, h, might be sunk more or less into the mould, their sides being perpendicular; but the patterns in Fig. 122 being undercut, the division of the mould into two parts only would be impracticable, and false cores or sub¬ divisions would be required in the manner represented, the con¬ struction of which will be hereafter detailed. Extending these same views to a more complex object, such as a bust, it will be conceived that the mould must be divided into 282 THE PRACTICAL METAL-WORKER’S ASSISTANT. so many pieces, that none of them will be required to embrace any overhanging part of the figure. For instance, were it attempted Fig. 121. to mould a human head, so that the parting might pass through the central line of the face and down the back, the two halves could not be separated if they were made each in a single piece; as the inner angles of the eyes, the spaces behind the ears, and the curls of the hair would obstruct it, and the head could be only thus moulded by making false cores or loose pieces at these par¬ ticular places, in the manner illustrated by the former figures. These would require to be accurately adapted to the surrounding parts, by pins and contrivances to ensure their re-taking their true positions. These remarks, however, are only advanced by way of general illustration, as figure casting is the most refined part of the art of moulding. Metal moulds are employed for many works in the easily-fused metals, which are required to be produced in large quantities, and with great similitude and economy: the examination of which moulds will serve to demonstrate many of the points of construc¬ tion and proceeding. Thus the common bullet mould is made like a pair of pliers, the jaws of which are conjointly pierced with a hole or passage leading into a spherical cavity; the aperture is equally divided between the two halves of the mould, so that in fact the division is truly upon the diametrical line both of the sphere and the runner, or the largest part of each, otherwise the pliers could not be opened to remove the bullet when cast. Iron shot for great guns are likewise cast in iron moulds, by which they also possess great accuracy of form and size. Figs. 123 124. CASTING AND FOUNDING. 233 Figs. 123 to 126 represent the moulds for casting pewter ink- stands: these moulds are a little more complex, and are each made in four parts; the black portions represent the sections of the ink- stands to be cast. The moulds each consist of a top piece or cap t, a bottom or core b, and two sides or cottles, s s ; in Fig. 126, the one Figs. 125 126. side is removed, in order to expose the casting, and the top piece t is supposed to be sawn through to make the whole more distinct. It will be seen, the top and bottom parts have each a rebate like the lid of a snuff-box, which embraces the external edges of the two side pieces s s, and the latter divide as in the bullet mould, exactly upon the diametrical line of the inkstand, which in a cir¬ cular object is of course the largest part; the positions of the parts are therefore strictly maintained. When the mould has been put together, laid upon its side, and filled through x, the ingate, or as it is technically called, the ledge, it is allowed to stand about a minute or two, and then the top t, is knocked off by one or two light blows of a pewter mallet; the mould is then held in the hand and the bottom part or core is knocked out of the casting by the edge; lastly, the two sides are pulled asunder by their handles, and the casting is removed from the one in which it happens to stick fast; but it requires cautious handling not to break it. The face of the mould is slightly coated with red ochre and white of egg, to prevent the casting adhering to the same, and to give the works a better face; the first few castings are generally spoiled, until in fact the mould becomes properly warmed. Most of the works made in the very useful material, pewter, are cast in gun-metal moulds, which require much skill in their construction; thus a pewter tankard, with a hinged cover and spout, consists of six pieces, every one of which requires a dif¬ ferent mould; thus, 1. The body has a mould in four parts, like that for the inkstand, but it is filled in the erect position through two ingates, which are made through the top piece t, of the mould: 2. The bottom requires a mould in two parts, and is poured at the edge: 3. The cover is cast in the same manner; and thus far the 23-4 THE PRACTICAL METAL-WORKER’S ASSISTANT. moulds are all made in the lathe, in which useful machine these castings are also finished be¬ fore being soldered together: 4. The spout requires a mould in two parts: 5. The piece, Fig. 128, by which the cover is hinged to the handle, requires a much more complex mould, which divides in four parts, as shown in Fig. 127, and much resem¬ bles, except in external form, the remaining mould: namely, 6. For the handle, which mould, like the last consists of four pieces fitted together with various ears and projections; they are represented in their relative positions in Fig. 130, with the excep¬ tion of the piece a, Fig. 131, which is detached and shown bottom upwards. Fig. 129 shows the pewter handle separately, with the three knuckles for joining on the cover: and on reference to Fig. 130, of the five parts through which the pin p, is thrust, the two ex¬ ternal pieces belong respectively to the sides c, and d, of the mould, the others are parts of the casting, and the two hollows are formed by the two solid knuckles fixed to the detached piece of the mould a, Fig. 131. At the time of pouring, the pin p, serves to connect the three parts a, c, d , together, and also to form the whole in the casting, for the pin of the joint. Figs. 129 130 131 Figs. 127 128. Fig. 132 shows the section of the mould upon the dotted line s: by this it will be seen the handle is cast hollow, as almost imme¬ diately the mould has been filled through t, all but the thin exter¬ nal shell is poured out again, and the weight is reduced to less than half. To extract the handle the pin p is first twisted out; CASTING AND FOUNDING. 235 then the joint piece a, is removed; next the back piece b ; and lastly the two sides c, d, are pulled asunder. Tin or pewter bearings for locomotive carriages, have been cast in appropriate metal moulds; and such materials are very useful to the mechanist for many temporary purposes, such as collars, bearings, screws and nuts, either for difficult positions, or where no screw tap is at hand and the resistance is moderate; in such cases the parts of the machine constitute one portion of the mould, the apertures being closed with moist loam: the processes are most successful when the parts can be made warm and the clay is nearly dry. The most important, exact, and interesting example of casting in metallic moulds is that of type-founding, the description of which, as well as drawings of the mould, have been repeatedly given; some of the peculiarities only of this art, will be therefore noticed. Each complete set of types consists of five alphabets, A, A, a, A, a, besides many other characters, in all about two hun¬ dred, and which are required to be most strictly alike in every respect, except in device and width ; the width is the greatest for the W and M, and the least for the i and !. Every required mea¬ sure of the types (represented on an enlarged scale in Eig. 133), is determined by the mould alone, and not by any after correction. If the moulds for the rectangular shafts of the types were made as in Figs. 134 or 135, the usual forms of square moulds, they would not admit of alteration in width, as shifting a, Fig. 134, would produce no change, and Fig. 135 would thereby produce the form b. The mould which is used is made in two L formed parts, as in Fig. 136, whence it follows that shifting the part a, to the right or left increases or decreases the width of the type with- 236 THE PRACTICAL METAL-WORKER’S ASSISTANT. out interfering with its thickness, or, as it is technically called, its body, (b, Fig. 133,) the width, w, is adjusted by a piece called the register, fixed at the bottom of the mould. The device is changed by placing across the bottom of the mould one of the two hundred little pieces of copper, Fig. 137, called matrices, into which the face of the latter is impressed by very beautifully formed punches The length of the letter is deter¬ mined by contraction at the upper part of the mould, as shown at c, Fig. 138, which represents the type as it leaves the mould; the metal is poured with a jerk, to make a sharp impression of the matrix: the mould, which is held in the left hand, and the ladle in the right, being jerked simultaneously upwards, at the moment of fill¬ ing the mould, and without which the face of the type would be rounded and quite imperfect. The breaks c, or the runners of the types, are first broken off, and after a slight correction of the sides, the hollows or channels in the feet are planed out of a whole col¬ umn of them, fixed between bars of wood, without touching the square shoulders which determine the lengths of the types, and are left as originally cast. In some types with a large face and much detail, such as the illustrations given on the last page, the motion of the hand is barely sufficient to give the momentum required to throw the me¬ tal into the matrix, and produce a clean sharp impression. A machine is then used, which may be compared to a small forcing- pump, by which the mould is filled with the fluid metal; but from the greater difficulty of allowing the air to escape, such types are in general considerably more unsound in the shaft or body ; so that an equal bulk of them only weigh about three-fourths as much as types cast in the ordinary way by hand, and which for general purposes is preferable and more economical. Some other variations are resorted to in type-founding; some¬ times the mould is filled at twice, at other times the faces of the types are dabbed, (the clichee process ;) many of the large types and ornaments are stereotyped, and either soldered to metal bodies, or fixed by nails to those of wood. The music type, and ornamental borders and dashes, display much very curious power of combina¬ tion. The clichee process is rather stamping than casting. The melted alloy is placed in a paper tray, and stirred with a card until it as¬ sumes the pasty condition. The metal die, or mould, is then “ dab¬ bed” upon the soft metal, as in sealing a letter, but with a little more of sluggish force. By the type-founding machine invented by Mr. Bruce, of N. Y., and employed in the extensive foundry of Collins and M’Leester, of Philadelphia, 3600 letters may be cast in an hour, much more sound and as perfect as those cast by hand. Plaster of Paris Moulds and Sand Moulds.— Other exam¬ ples of metallic moulds might be given, but there are far more frequent cases in which one single casting is alone required; or CASTING AND FOUNDING 237 else the number is so small, or the pieces themselves are so large or peculiar, that the construction of metal moulds would be found almost or quite impracticable, even without reference to an equally fatal barrier, the expense. In making these single copies in the metals of considerable fusi¬ bility, plaster of Paris is sometimes employed; thus, after the printer has arranged the loose types into a page, and the requisite corrections have been made, a stereotype, or solid type, is taken of the whole as a thin sheet of metal, which serves to be printed from almost as well as the original letters : and its small cost enables the printer to retain it for future use, after the types themselves have served perhaps for a hundred similar regenerations, and are ulti¬ mately worn out. The stereotype founder takes a copy of the entire mass of type in plaster of Paris ; this is dried in an oven, and placed face down¬ wards within a cast-iron mould, like a covered box, open at the four top-corners. The mould and plaster-cast are heated to the fusing temperature of the type-metal, and gradually lowered into a pan or bath of the same by means of a crane; the hot fluid metal runs in at the corners of the mould, and raises the inverted plas¬ ter, which latter would rise entirely to the surface but for the restraint of the cover of the mould. Type-metal is about eleven times as heavy as water; and if the mould be immersed four inches below the surface, it is subjected to a pressure equal to that of a column of water forty-four inches high, or above two pounds upon every square inch. The necessity of this arrangement is shown when a few ounces of type-metal are poured from a ladle on the face of the plaster ; the metal looks like a dump, almost without any mark of the let¬ ters, whereas the stereotype-cast is nearly as sharp as the original type. The immersion fulfils the same end as the jerk of the hand-caster, or of the pump occasionally employed: and the long continuance of the mould in the fluid metal allows ample time for the air to escape in bubbles to the surface; after which the mould is raised and cooled in a vessel of water, and the plaster is mostly destroyed in its removal. Plaster of Paris, although it may be, and frequently is used for the fusible metals, such as lead, tin, and pewter, cannot be em¬ ployed alone for iron, copper, brass, and many other metals, the intense melting heats of which would calcine the material, and cause it to crumble; even the soft metals should not be very hot, or they will make the plaster of Paris blister off in flakes or dust. We must therefore seek a substitute better capable of enduring the heat, and likewise susceptible of receiving definite forms; for which purpose damp sand, with a small natural or subsequent admixture of clay or loam, is found 10 be perfectly adapted. The moulding-sand cannot, however, be used without external support, and which is given by shallow iron frames without tops or bottoms, called flasks, represented in Figs. 139 and 140. The bot- 238 THE PRACTICAL METAL-WORKER’S ASSISTANT. tom part, 4, 5, is supposed to have been rammed full of sand, and to stand upon a flat board, 6. The model of the plain flat bar which is to be cast, is now laid on the surface of the sand, that of Fig. 139. Fig. 140. the round bar is imbedded half way in the same, and the mould is dusted with dry parting sand. The top part of the flask 2, 3, is shown still empty, and in the act of being attached to 4, 5 by its pins, which enter corresponding holes in the latter, easily but without shake: 2, 3 is also rammed full of sand, and covered with a top board, 1, not represented to avoid confusion. The mould is now opened, the models are removed, and channels are scooped out from the ends of the cavities left by the models, to the hollows or pouring-holes at the end of the flask: the parts are all replaced in the order 1 to 6, represented in Fig. 139, and the whole are fixed together by screw clamps, so as to assume the condition of Fig. 140. The flask is now placed almost perpendicularly beside the pour¬ ing-trough, and the metal is poured into it from the cruoible, as shown in Fig. 119, p. 221; but the flask, if small, is put on the sur¬ face of the pouring or spill-trough, and propped up with a short bar. This brief sketch of the entire process of moulding and casting in sand moulds, will be now followed by some remarks in greater detail: first on the patterns of the objects to be cast; secondly, on the conditions required in the sand; and thirdly, the process of mould¬ ing simple and solid bodies. The section then following will be devoted to moulding cored works, and figures, after which a few lines will be given upon the subject of filling the moulds. Patterns, Moulds, and Moulding Simple Objects.— The perfection of castings depends much on the skill of the pattern¬ maker, who should thoroughly understand the practice of the moulder, or he is liable to make the patterns in such a manner that they cannot be used, or at any rate be well used. CASTING AND FOUNDING. 239 Straight-grained deal, pine, and mahogany, are the best woods for making patterns, as they stand the best; screws should be used in preference to nails, as alterations are then more easily made in the models, and glue joints, such as dovetails, tenons, and dowels, are also good as regards the after use of the saw and plane for cor¬ rections and alterations. Foundry patterns should be always made a little taper in the parts which enter most deeply into the sand, in order to assist their removal from the same, when their purposes will not be materially interfered with by such tapering. The pattern-maker, therefore, works most of the thickness, and the sides or edges, both internal and external, a little out of parallel or square, perhaps as much as about one-six¬ teenth'to one-eighth of an inch in the foot, sometimes much more. When foundry patterns are exactly parallel, the friction of the sand against their sides is so great when they penetrate deeply, that it requires considerable force to extract them; and which vio¬ lence tears down the sand, unless the patterns are much knocked about in the mould, to enlarge the space around them. This rough usage frequently injures the patterns, and causes the castings to become irregularly larger than intended, and also defective in point of shape, from the mischief sustained by the moulds; all which evils are lessened when the patterns are made consistently taper and very smooth. It must be distinctly and constantly borne in mind, that although patterns require all the methods, care, and skill, of good joinery or cabinet-making, they must not, like such works, be made quite square and parallel, for the reasons stated. Sharp, internal angles should in general be also avoided, as they leave a sharp edge or arris in the sand, which is liable to be broken down in the removal of the pattern; or to be washed down on the entry of the metal into the mould. Either the angle of the model should be filled with wood, wax, or putty, or the sharp 'edges of the sand should be chamfered off with the knife or trowel. Sharp internal angles are very injudicious in respect also to the strength of castings, as they seem to denote where they will be likely to break; and more resemble carpentry than good metallic construction. Before the patterns reach the founder’s hands, all the glue that may have been used in their construction should be carefully scraped ofi, or it will adhere to and pull down the sand. The best way is to paint or varnish wooden patterns, so as to prevent them from absorbing moisture, as they will then hang to the sand much less, and will retain their forms much better. Whether painted or not, they deliver more freely from the mould when they are well brushed with black lead, like a stove. In patterns made in the lathe,'exactly the same conditions are required; the parts which enter deeply into the sand should be neither exactly cylindrical nor plane surfaces, but either a little coned, or rounding, as the case may be; and the internal angles should not be turned exactly to their ultimate form, but rather 240 THE PRACTICAL METAL-WORKER’S ASSISTANT. filled in, or rounded, to save tlie breaking down of the sharp edges of the mould. Foundry patterns are also made in metal; these are very excel¬ lent, as they are permanent; and when very small are less apt to be blown away by the bellows used for removing the loose sand and dust from the moulds. To preserve iron patterns from rust¬ ing, and to make them deliver more easily, they should be allowed to get slightly rusty, by lying one night on the damp sand; next, they should be warmed sufficiently to melt beeswax, which is then rubbed all over them, and in great part removed, and then polished with a hard brush when cold. Wax is also used by the founder for stopping up any little holes in the wooden patterns; whitening is likewise employed, as a quicker but less careful expe¬ dient ; and very rough patterns are seared with a hot iron. The good workman, however, leaves no necessity for these corrections, and the perfection of the pattern is well repaid by the superior character of the castings. Metal patterns frequently require to have holes tapped into them for receiving screwed wires, by way of handles for lifting them out of the sand; and in like manner, large wooden patterns should have screwed metal plates let into them, for the same purpose, or the founder is compelled to drive pointed wires into them, to serve as handles, which is an injurious practice. The flasks or casting-boxes for containing the sand, are made of various sizes. Each side is about 2 to 3 inches deep. They are poured at the edge when placed nearly vertical; but for large brass works the practice of the iron-founder is generally followed, who mostly pours his work horizontally, through a hole in the top, as will be explained. The pins of the flask should fit easily, but with¬ out shake, or the two halves will shift about and cause a disagree¬ ment or slip in the casting. The tools used in making the moulds are few and simple, namely, a sieve, shovel, rammer, strike, mallet, a knife, and two or three loosening wires and little trowels, which it is unnecessary to describe. The principal materials for making foundry moulds are very fine sand and loam. They are found mixed in various proportions, so that the respective quantities proper for different uses cannot be well defined; but it is always judicious to employ the least quantity of loam that will suffice. These materials are seldom used in their new or recent states for brass castings, although more so for iron, and the moulds made of fresh sand are always dried, as will be explained. The ordinary moulds are made of the old damp sand, and they are generally poured immediately, or whilst they are green; some- . times they are more or less dried upon the face. The old working fine sand is considerably less adhesive than the new, and of a dark- brown color. This arises from the brick-dust, flour, and charcoal- dust used in moulding becoming mixed with the general stock, which therefore requires occasional additions of new sand or loam,* CASTING AND FOUNDING. 241 so that when slightly moist and pressed firmly in the hand it may form a moderately hard compact lump. Red brick-dust is generally used to make the partings of the mould, or to prevent the damp sand in the separate parts of the flask from adhering together. The face of the mould which receives the metal is generally dusted with meal-dust, or waste flour; but in large works, pow¬ dered chalk, and also wood or tan ashes, are used, from being cheaper. The moulds for the finest brass castings are faced either with charcoal, loamstone, rottenstone, or a mixture of the same. The moulds are frequently inverted and dried over a dull fire of cork shavings, or when dried they are smoked over pitch or black resin lighted in an iron ladle. The gold and silver casters frequently use a lighted link for facing their sand-moulds, and some of the type-founders’ metallic moulds are smoked over a lamp. All these modes deposit a fine layer of soot upon the moulds. The cores, or loose internal parts of the moulds for forming holes and recesses, are made of various proportions of new sand, loam and horse-dung, as will be explained in the section on cored works. They all require to be thoroughly dried, and those containing horse-dung must be well burned at a red heat; this consumes the straw and makes them porous, and of a brick-red. In making the various moulds, it becomes necessary to pursue a medium course between the conditions best suited to the forma¬ tion of the mould and those best suited to filling them with the red-hot metal without risk of failure or accident. Thus, within certain limits, the more loam and moisture the sand contains, and the more closely it is rammed, the better will be the impression of the model; but at the same time the moist and impervious con¬ dition of the mould would then incur the greater risk of accident, both from the moisture and from the non-escape of the air. There¬ fore the policy, on the score of safety, is to use the sand as dry as practicable, so as to avoid the delay of after-drying, and also to keep the mould porous. The founder, therefore, compromises the matter by using a little facing sand containing rather more loam, for the face of the green moulds for general work; and in those cases where much loam is used, the moulds are thoroughly dried by heat, which is not gen¬ erally necessary with ordinary sand moulds. The power of conducting heat is considerably less in red-hot iron than in copper and brass, and therefore the moulds for the latter require to be in a drier condition than those which may be used for iron; but in either case the presence of superfluous moisture is always attended with some danger to the individual as well as to the work. The above is the reason generally assigned for the fact that the iron-founders may and do use their moulds with safety when sen¬ sibly more moist than is admissible for brass and copper castings. 16 242 THE PRACTICAL METAL-WORKER’S ASSISTANT. It is confirmatory of the fact that the more dense the mould, the drier it must be, as the sand used by iron-founders is also coarser and therefore more porous than that employed by brass- founders. Another point has also to be considered: as castings contract considerably in cooling, in moulding large and slight works the face of the mould must not be too strongly rammed, nor too much dried, or its strength may exceed that of the red-hot metal whilst in the act of shrinking. The result would be, that in contracting, the casting would be rent or torn asunder from the restraint of the mould; whereas it should have the preponderance of strength, so as to pull down the face of the sand instead of being itself de¬ stroyed. But the exact condition both of the mould and of the melted metal, must be determined by the nature of the object to be cast,—matters which can be only referred to with the development of the practice of the foundry, and upon which we shall now commence. The sand having been prepared, and the appropriate flask and boards selected, the moulder first examines every pattern sepa¬ rately to determine the most appropriate way of inserting it in the flask, as explained by Fig. 121, p. 232 ; also to see that patterns, such as / and h, therein shown, are smallest at the parts entering the most deeply into the sand, in order that they may deliver well. It should also be noticed whether they are perfectly smooth, and that there is no glue hanging about them, which would cause them to adhere and to pull down the moist sand. The bottom flask, 4, 5, p. 238, is placed on a board not less than an inch or two longer and wider than itself, with the face 4, down¬ wards, and it is filled from the side 5. A small portion of the strong facing-sand is rubbed through a fine sieve; the remainder is thrown in from the trough with the shovel, and the moulder drives the whole moderately hard into the flask, either with a mallet, the handle of the spade, or other rammer ; or else he jumps up by aid of the rope suspended from the ceiling, and treads the sand in with his feet. The surface is then struck off level with a straight metal bar or scraper, a little loose sand is sprinkled on the surface, upon which another board is placed, and rubbed down close. The two boards and the flask contained between them are then all three turned over together. This requires them to be brought to the front of the moulding-trough, so that the individual may rest his chest against them, and his fore-arms upon the edges of the top board ; he then grasps the three together at the back part with his outstretched hands, and, thus retained in contact, the whole are quickly turned over upon the front edge of the mould¬ ing-trough, and then slid back upon the transverse bearers or blocks to the usual position. The top board is afterwards taken off, the clean surface of moist sand, then exposed, is well dusted over with red brick-dust, crushed CASTING AND FOUNDING. 243 fine, and contained in a linen bag. The mouth of the bag is held in the right hand, and the bottom corner in the left, and both hands are shaken up and down together to scatter the dry powder uni¬ formly over the flask. A part of the loose powder is removed with the hand-bellows, and the bottom half of the mould is then ready for receiving the patterns. The models are next arranged upon the face of the sand at 4, so as to leave space enough to prevent the parts breaking one into the other, and also for the passages by which the metal is to be introduced, and the air allowed to escape. When there are only two or three pieces to be cast, a separate runner is often made to each of them from one of the holes in the end of the flask. When several small patterns are to be moulded, they are arranged on both sides a central runner, or ridge, from which small passages lead into every section of the mould. The whole mass when poured has been compared to a great fern leaf with its leaflets, and is usually called a spray. Those patterns which are cylindrical or thick, are partly sunk in the sand by scraping out hollow recesses with the bowl of an old copper spoon, and knocking the model into the sand with the mallet. Afterwards the general surface is repaired to agreement with the diametrical line of the model, or its largest section, as the case may be, by means of a knife or a little piece of sheet steel, something like the worn-out blade of a desert-knife bent up a little at the end, or else with very small trowels. After the sand is made good to the edges of the patterns, the brick-dust is again shaken over them, so that the patterns may receive a slight share as well as the general surface of the sand. The upper part of the flask 2, 3, is then fitted to the lower, or 4,5, by the pins, and this half likewise is made up. First a little strong sand is sifted in; it is then filled up from the trough, rammed down, and struck off as before, the dry powder serving to prevent the two halves from sticking together. In order to open the mould for the extraction of the models, a board is placed on the top of flask 2, 3, and struck smartly at dif¬ ferent parts with the mallet; the tool is then laid aside and the upper part of the flask and its board are lifted up very gently and quite level, after which it is inverted on its board—and now each of the inner faces of the mould is exposed. Should it happen that any considerable portion of the mould, say a part as large as a shilling, is broken down in one piece, the cavity is moistened with the end of the knife, the mould is again carefully closed, and lightly struck before the removal of the patterns. It is probable on the second lifting such piece will be picked up. The breaks are carefully repaired before the extraction of the patterns, to effect which they are driven slightly sideways with blows of the mallet, given on a short wire or punch, so as to loosen them by enlarging the space around them. The patterns are then lifted out very carefully with the finger-nails, or sometimes a 244 THE PRACTICAL METAL-WORKER’S ASSISTANT. pointed wire is driven a little way into the pattern to serve as a handle to lift it by. This process requires some delicacy not to tear away the sand, which accident must be carefully repaired, sometimes by replacing the loose pieces, at other times with a little new sand picked out of any unused part of the mould. A steel wire, pointed and hardened, is convenient as a picker out, and when fixed in the pattern and stuck sideways it serves as a loosening bar likewise. Should the flask only contain one or two objects, the ingate or runner is now scooped out of the sand, so as to lead from the object to the pouring hole, and when several objects are contained, a large central channel, and lesser passages sideways, are made as before mentioned. The entrance round about the pouring hole is smoothed and compressed with the thumb that it may not break down when the metal is poured, and all the loose sand is care¬ fully blown out of the mould, both parts of which may be placed edgeways for the more convenient application of the bellows if necessary. The succeeding processes are to dust the faces of both halves of the mould with meal dust or waste flour, as explained with regard to the brick-dust, and to replace the mould and boards. The whole of them are then carried to the spill-trough, upon the edge of which they are rested whilst the one board is placed exactly level with the end of the flask, but the board on the side from which the crucible will be poured, is placed about two inches below, as in Fig. 140, p. 238, and the hand-screws are fixed on as shown. The mould is now held mouth downwards, that any sand loosened in the screwing down may be allowed to fall out, and the flask, according to its size, is supported either on the ground or on the surface of the trough by aid of a little bar resting against the clamp. It is now quite ready to be filled—the particulars of which process will be described when the remarks on moulding are concluded. In works that require the first side or 3, 4 to be cut away for embedding the models, it is usual when the second part or 2, 3 has been made, to destroy the first or false side (which is only hastily made), and to repeat it in a more careful manner by inverting the lower flask upon 2, 3, proceeding in all other respects as before, by which means a much more accurate and sound mould is pro¬ duced. When many copies of the same patterns are required, an odd side is prepared, that is, a flask is chosen to which there are two bottom sides, 4, 5. One of these latter is very carefully arranged with all the patterns, but which are only embedded barely half way, so that when 2, 3, is filled and both are turned over, the whole of the pat¬ terns are left in the new side; a second side, 4, 5, is moulded to serve for receiving the metal, as the mould is destroyed every time the metal is poured in. By this plan the trouble of re-arranging the patterns for every separate mould is saved, as they are merely CASTING AND FOUNDING. 245 replaced in the odd side, and the routine of forming the two work¬ ing sides is repeated. Moulding Cored Works. —If the objects to be cast require to be so moulded that when they leave the sand they may contain one or several holes, they are said to be cored, and in such cases, a variety of methods are practised for introducing internal moulds or cores, which shall intercept the flow of the metal, and prevent it from forming one solid mass at those respective parts. For example, the pins inserted in the pewterers’ moulds, Figs. 127 and 130, page 234, for producing the holes in the joints, are essentially cores. Various other methods are pursued, the three most usual of which are represented in Figs. 141, 142, and 143 : the upper fig¬ ures show the exact sections of the three models or casting pat¬ terns ; the lower figure represents the two halves of the mould, which are respectively shaded with perpendicular and horizontal lines, the cores are shaded obliquely; and the white open spaces show the hollows to be occupied by the metal when it is poured in. First. Many works are said to deliver their own cores; of such kind is Fig. 141, in which the cavity extends through the model, and exactly represents that which is required in the casting; the hole is either made quite parallel, or a little larger one side than the other, and gradually taper between the two. In some cases, when the hole is sufficiently taper, it delivers its own core as a con¬ tinuation of the general mass of sand filling the one side of the flask ; but in many or most cases, the space in the model is rammed full of strong sand at first, and it is then moulded as if to produce a plain solid casting. Before the mould is finally closed for pouring, the sand core is pushed carefully out of the pattern, and inserted in the mould; to denote its precise position, one side of the core is scored with one or two deep marks in the first instance, which cause similar ridges or guides in the mould. Secondly. When the hole extends only part way through, the hole of the pattern, Fig. 142, is fitted with a solid plug, sawn and filed out of soft unburnt brick, principally sand (or the common Figs. 141 142 143. Flanders brick), the core is made long enough to project about as much as its own diameter, and the work is moulded as if to be cast with a solid pin, instead of a hole. The last step is to extract 246 THE PRACTICAL METAL-WORKER’S ASSISTANT. the filed core, and to insert it into the hollow formed by itself in the flask. Thirdly. The patterns for iron work and some others are mostly made with prints instead of holes, as in Fig. 143; that is, the pat¬ tern-maker places square or round pieces on one or both sides of the pattern, where thg square or round holes are respectively required; and the founder has moulds for forming cores of corres¬ ponding diataeters or sections, and in lengths of about two to twelve inches; short pieces of which are cut off as may be required. For example, some core-boxes are made like Fig. 144, for cylin¬ drical uores; these divide through the axis, and are kept in posi¬ tion by pins; at the time when they are rammed they are fixed together by wood or iron staples, embracing three sides of the mould, or else by screw clamps. For straight cores, say one inch wide, twelve inches long, and half-inch thick, the pieces of wood, Fig. 145, are also one inch thick, with an opening between them of twelve inches long and half-inch wide. This core-box is laid on a flat board, it is also held together with clamps, but without pins in the core-box, as the projection at the one end gives the position; it is rammed flush with both sides, and the two parts can be then separated obliquely. If it is preferred to make the cores to the precise lengths instead of cutting them off, this core-box admits of contraction in length, in the manner of the type mould, Fig. 136, p. 235, and by placing thin slips between the two halves it may be temporarily increased in width but not in thickness. Fig. 146 is a similar core-box for a casting with circular mortises; this requires pins or projections at each end, as it cannot be opened obliquely. Core-boxes are sometimes made of plaster of Paris, wood is much better, and metal is the best of all. Many works require core-boxes to be made expressly for them; thus the dotted line in Fig. 144 shows an enlargement in the centre for coring a hole of that particular section. Figs. 147 and 148 represent the two halves of a brass or lead core-box suitable to the Figs. 144 145 stop-cock, Fig. 149 ; and Fig. 150 shows the core itself after its removal from the part 148 in which it is also figured. In 149, the CASTING AND FOUNDING. 247 model from which the object is moulded, the shaded parts repre¬ sent the projections, or core-prints, which imprint within the mould the places where the extremities of the core, Fig. 150, are sup ported when placed therein. The various kinds of core-boxes are rammed full of new sand, sometimes with extra loam; the long cores are strengthened by wires; they are carefully removed from the boxes and thoroughly dried before use, in the oven prepared for the purpose. Others perfer sand, horse-dung, and a very little loam, for mak¬ ing cores; these are dried, and then well burned, for which purpose they are put into an empty crucible within the fire, the last thing at night, and allowed to remain until the morning. This consumes the small particles of straw, and renders them more porous, in consequence of which the works become sounder from the free escape of air, the necessity of which was adverted to in the earlier part of this subject, and cannot be too much insisted upon. Fig. 151 represents several examples of coring: in this view the works are represented of their ultimate forms, that is, with the holes in them; in Fig. 152, the models are arranged in the flask, Fig. 151 a with the runners all prepared, the prints of the cores being in every case shaded for distinction. Thus a is the stopcock, of which ex¬ planation has been already given; b, has a straight and a circular mortise; this pattern delivers its own core, in the manner referred to in Fig. 141, as the model is made with mortises like the finished work: c oidy requires a perpendicular square core; d, a round core parallel with the face of the flask, and in this manner all tubes and sockets are cast whether of uniform or irregular bore, see Fig. 144; e, has two rectangular cores crossing each other at right angles: 248 THE PRACTICAL METAL-WORKER’S ASSISTANT. and f is the cap of a double-acting pump, the core for which is shown in section by the white part of Fig. 152 J, the shaded portions being the metal: the great aperture leads to the piston, the two smaller are for valves opening inwards and outwards; this of course requires a metal core-box capable of division in two parts, and made exactly to the particular form. In addition to the cores used for making holes and mortises, much ingenious contrivance is displayed in the cores employed for other works of every-day occurrence, the undercut parts of which would retain them in the sand but for the employment of these and analogous contrivances. It will be now readily under¬ stood that if, in the Fig. 122, p. 232, the parts shaded obliquely were separate, there would be no difficulty in removing first the upper half of the flask, the false cores, after which the patterns would be quite free. The term false core is employed by the brass- founder to express the same thing as the drawback of the iron- founder. The former calls every loose piece of the mould not intended for holes, a false core. By such a method, however, the circular edge of a sheave would require at least three such pieces, but Fig. 153 shows a different way of accomplishing the same Fig. 153. thing, when the pattern is made in two parts in the manner repre¬ sented. The entire model is first knocked into the side A, the sand is cut away to the inner margin of the pattern which terminates upon the dotted line a, and the side A, of the mould is then well dusted; a layer of sand is now thrown on, and rammed tolerably firm to form an annular core, which is made exactly level with the inner margin b of the pattern, and the core is well dusted; lastly, the side B is put on and rammed as usual. To extract the model, the side B is first lifted, the half pattern b, b, (which is shaded,) is removed, and the ingate is cut in the side B, to the edge of the pully; the mould is well dusted with flour and replaced. The entire mould is now turned over, A is first removed, then the remaining half pattern a, a, which must be touched very ten¬ derly or it will break down the core; and the runner, (which divides in two branches around the core), is also scooped out in the side A, which is dusted with flour and replaced, ready for pouring. Common patterns not requiring cores are frequently divided into CASTING AND FOUNDING. 249 155 two parts in tlie above manner, so tbat when tbc mould is open the pattern may divide and remain half in each side; this lessens the risk of breaking down the mould and the attendant trouble ol afterwards repairing it. Reversing and Figure CASTiNG.-^Supposing that an orna¬ ment, represented in section in Fig. 154 has been modeled in relief, either in clay or wax upon a flat board, from which a thin casting in brass is wanted without the tablet, the process is called revers¬ ing, and is to be accomplished in any of three ways. First an empty flask is placed upon the board, 154, and rammed full of sand; it assumes the appearance of 155 ; the second part of the flask is attached to 155 and filled to make the part 156, which is called the back-mould ; some clay is then rolled out to the intended thickness of the casting, with a cylindrical roller running on two slips of wood or on two wires, and a narrow band of this clay is placed on 156, round the figure, that it may separate 155 and 156, exactly to the required distance, ready for receiving the metal. By the second mode, 155 is first made, then 156, and from the latter 157 is moulded, which is a counterpart of 155. A thin sheet of clay is then pressed all over 157, into every cavity, and cut oft' flush with the plane surface of the mould, by which it assumes the appearance denoted by the double line in 157. After this 156 is destroyed, and made over again in 157, but so much smaller than before as the thickness of the clay lining; when the new back-mould, 156, is placed in contact with 155, it leaves the re¬ quired space for the intended casting. This mode is only prefer¬ able to the first, when many parts of the work are nearly perpen¬ dicular; in which case, if the first mode be adopted, a portion of the back mould 155 must be pared away at the perpendicular parts, and if incautiously performed there will be a risk of irregu¬ larity of thickness, or even of holes in the casting. The third mode is to take a casting of 154 in plaster of Paris; when this is thoroughly dry it is oiled, and poured full of a cement of wax, grease, and red-ochre, which is poured out again when par tially set, leaving a thin crust behind (as in the pewter handle). A second, a third, or more layers of wax are thus added until the whole is sufficiently thick, when the wax shell is extracted, and then moulded from in the ordinary manner; the first brass casting is finished and chased to serve as the permanent pattern. The management of the wax requires practice. In constructing such moulds additional care is given to every part of the work; for example, the sand is sifted much finer, the 250 THE PRACTICAL METAL-WORKER’S ASSISTANT. parting is made with fine charcoal dust, and the facing with char¬ coal and rottenstone mixed together in about equal parts, the mix¬ ture being of a slaty color; sometimes the loamstone, which is found in the pits where clay for making tiles is dug, is used instead of rottenstone. The moulds are well dried in an oven, or ever the mouth of the furnace, and the faces are afterwards smoked over a dull fire of cork shavings ; this deposits a very fine layer of soot over the face of the mould, which greatly assists the running of the metal; when this additional care is taken the works are known as fine-castings. In casting figures, such as busts, animals, and ornaments consist¬ ing of branches and foliage, considerably more skill is required : the originals are generally solid, but the moulds necessarily divide into very many parts. Most persons will have had the opportunity of judging of the complexity of these moulds, from similar works in plaster of Paris, which are frequently purchased by artists and the virtuosi before the seams of the mould are removed. A glance at these plaster-casts, at the complex and undercut form of many of these ornamental works, and at the explanatory diagram on page 231, will convey some notion of the method to be pursued as well as of the trouble attending them. It is shown for example, by the diagram just referred to, that all figured works approaching to the circular or elliptical section, require that the mould should be divided into at least three parts, except under most favorable circumstances. In the human figure and quadru¬ peds, the four limbs and the trunk require at least three parts each, and often many more; it will be easily conceived therefore that such moulded works require considerable skill and patience. Piece after piece of the mould is successively produced, just as in making the core, Fig. 153, p. 248, every piece embracing only so much of the figure, as in no part to require any core to over¬ hang the line in which it is withdrawn. The side of the mould in which the figure is partly embedded is first dusted with charcoal, and then the first core is very carefully rammed into the nook, and pared down to the new line of division; the green or wet sand core is then dusted, and the second core is made, and after¬ wards dusted, when the moulder proceeds with the third core and so on ; every one being carefully adapted to its neighbor, and with¬ drawn to see that all is right, before the succeeding core is pro¬ ceeded with. The relative positions of the cores amongst them¬ selves are readily recognized and maintained by the irregularity of their forms, as in a child’s dissected map, or by making a notch or two here and there, which are faithfully copied in the succeed¬ ing piece. It is frequently necessary to thrust two or more broken needles through the green cores into the neighboring parts to con¬ nect them together, in imitation of the pins in the flasks. All the parts of the mould are dried in the oven, and the facings are smoked over a cork fire as before explained; the perfection of the casting is augmented by pouring whilst the mould is still CASTING AND FOUNDING. 251 slightly warm, as otherwise on cooling it has an increased affinity for damp; but the mould when hot is more or less filled with aqueous vapor, which is equally prejudicial. When a figure, such as a bust, is required to be cast hollow from a solid model, it is first moulded exactly as above. The core is now produced as follows: at the foot of the bust a large space, nearly equal in length and bulk to the bust, is cut away in the sand, to serve for fixing the core in the mould, or for the balance, as it is called, as the core cannot be propped up at both ends. The entire hollow, that is for the bust and the balance, is filled with a com¬ position of about one part of plaster of Paris and two of sand or fine brick-dust, mixed with a little water and poured in fluid, a few wires being placed amidst the same for additional support. The mould is now taken to pieces to extract the core, which is then dried, thoroughly burned, and allowed to cool slowly (which the founder calls annealing, from a similar method being employed in annealing or softening the metals and glass): the core is then re¬ turned to the mould, to see that it has not become distorted. If needful the fitting around the balance is made good to suit the re¬ duced magnitude of the core, which latter is then so far pared away as to leave room for the thickness' of metal; this is frequently regu¬ lated by boring holes at many parts of the core with a stop-drill, having a collar to prevent its penetrating beyond the determined depth; the surface of the core is now pared down to the bottoms of the holes, as uniformly as possible. When the mould has been faced, dried and smoked, the whole is put together for pouring, for which purpose the figure is inverted and filled from the pedestal. Equestrian and other figures are sometimes cast in two, three, or more pieces, and joined together by solder, screws, or wires; but in all such works, the aim of the founder is to leave little or nothing for the finisher or chaser to do. Some objects which are either exceedingly complex in their form, or soft and flexible in their substance, and which do not therefore admit of being moulded in sand, in the ordinary manner of figure casting, may be moulded for a single copy, provided the originals consist of substances which may be either readily melted or burned into ashes. A cavity is made in the sand of the moulding-trough, a little larger and longer than the object, or else a wooden box of appro¬ priate size is procured, in the midst of which the wax model may be placed; to the end of the model is added a piece to represent the runner, which will be required for introducing the metal. The composition of one-third plaster of Paris and two-thirds brick-dust, mixed with water, the same as for the core of the bust, is then poured in. entirely to surround the model. The mould is first slowly dried, it is then inverted and made warm to allow the wax to run out, after which it is annealed, or burned to redness, and lastly, when cooled, it is buried in sand and filled with metal. The 252 THE PRACTICAL METAL-WORKER’S ASSISTANT. method necessarily throws the chance of success upon a single trial, as the model is destroyed. Should the face of the casting be required to be particularly smooth, a small quantity of brick-dust is washed, (in the manner practised with emery, and to be explained,) and mixed with very line plaster: a coat of this is brushed over the model, which ex¬ cludes air-bubbles, the model is quickly placed in its cavity, and the coarser mixture is poured in as before. The above method exactly corroborates a mode long since des¬ cribed as being suitable to casting copies of small animals or in¬ sects, parts of vegetables and similar objects; these are to be fixed in the centre of a small box, by means of a few threads attached to any convenient parts, one or two wires being added to make air¬ holes, and ingates for the metal. A small quantity of river silt or mud, which had been carefully washed, was first thrown in and spread around the object by swinging the box about; and when partly dry, successive but coarser coats were thrown in, so as ulti¬ mately to fill up the box. When it had become thoroughly dry, the wires were first removed from the earthy mould; it was then burned to reduce the object to ashes, and when every particle of the model had been blown out, it was ready to be filled with metal. Filling the Moulds.— Having traced the formation of various kinds of moulds for brass work, we must now return to the fur¬ nace to see if the metal is in condition to be poured, which is in¬ dicated by the slight wasting of the zinc from its surface with a lambent flame. When this condition is observed, the large cokes are first removed from the mouth of the pot, and a long pair of crucible tongs are thrust down beside the same to embrace it securely, after which a coupler is dropped upon the handles of the tongs: the pot is now lifted out with both hands and carried to the skimming-place, where the loose dross is skimmed off with an iron rod, and the pot is rested upon the spill-trough, against or upon which the flasks are arranged. The temperature at which the metal is poured must be propor¬ tioned to the magnitude of the works: thus large, straggling, and thin castings require the metal to be very hot, otherwise it will be chilled from coming in contact with the extended surface of sand before having entirely filled the mould; thick massive castings if filled with such hot metal would be sand-burned, as the long con¬ tinuance of the heat would destroy the face of the mould before the metal would be solidified. The line of policy seems therefore to be, to pour the metals at that period when they shall be sufficiently fluid to fill the moulds perfectly and produce distinct and sharp impressions, but that the metal shall become externally concealed as soon as possible after¬ wards. For slight moulds the carbonaceous facings, whether meal-dust- charcoal, or soot, are good, as these substances are bad conductors, CASTING AND FOUNDING. 253 of heat, and rather aid than otherwise by their ignition ; it is also proper to air these moulds for thin works, or slightly warm them before a grate containing a coke fire. But in massive works these precautions are less required; and the facing of common brick- dust, which is incombustible and more binding, succeeds better. The founder therefore fills the moulds having the slightest works first, and gradually proceeds to the heaviest; if needful he will wait a little to cool the metal, or will effect the same purpose by stirring it with one of the ridges or waste runners, which thereby becomes partially melted. He judges of the temperature .of the melted brass, principally by the eye, as when out of the furnace and very hot, the surface emits a brilliant bluish white flame, and gives off clouds of the white oxide of zinc, a considerable portion of which floats in the air like snow, the light decreases with the temperature, and but little zinc is then fumed away. Gun-metal and pot-metal do not flare away in the manner of brass, the tin and lead being far less volatile than zinc; neither should they be poured so hot or fluid as yellow brass, or they will become sand-burned in a greater degree, or rather the tin and lead will strike to the surface, as noticed at page 212. Gun-metal and the much used alloys of copper, tin, and zinc, are sometimes mixed at the time of pouring; the alloy of lead and copper is never so treated, but always contains old metal, and copper is seldom cast alone, but a trifling portion of zinc is added to it, otherwise the work becomes nearly full of little air-bubbles throughout its surface. When the founder is in doubt as to the quality of the metal, from its containing old metal of unknown character, or that he desires to be very exact, he will either pour a sample from the pot into an ingot mould, or extract a little with a long rod terminating in a spoon heated to redness. The lump is cooled and tried with the file, saw, hammer, or drill, to learn its quality. The engraved cylinders for calico-printing are required to be of pure copper, and their unsoundness when cast in the usual way, was found to be so serious an evil that it gave rise to casting the metals under pressure. Some persons judge of the heat proper for pouring, by apply¬ ing the skimmer to the surface of the metal; which when very hot has a motion like that of boiling water; this dies away and be¬ comes more languid as the metal cools. Many works are spoiled from being poured too hot, and the management of the heat is much more difficult when the quantity of metal is small. The mixture and temperature of the metal being found to be proper, it is poured in the manner represented in Fig. 119, p. 221 . the tongs are gradually lowered from the shoulder down the left arm, and the right hand is employed in keeping back the dross from the lip of the melting-pot. A crucible containing the gen¬ eral quantity of 40 or 50 lbs. of metal, can be very conveniently managed by one individual, but for larger quantities, sometimes amounting to one hundred weight, an assistant aids in supporting 254 THE PRACTICAL METAL-WORKER’S ASSISTANT. the crucible, by catching hold of the shoulder of the tongs with a grunter, an iron rod bent like a hook. Whilst the mould is being filled, there is a rushing or hissing sound from the flow of the metal and the escape of the air; the effect is less violent where there are two or more passages, as in heavy pieces, and then the jet can be kept entirely full, which is desirable. Immediately after the mould is filled, there are gener¬ ally small but harmless explosions of the gases, which escape through the seams of the mould; they ignite from the runners, and burn quietly; but when the metal blows, from the after-escape of any confined air, it makes a gurgling bubbling noise, like the boiling of water, but much louder, and it will sometimes throw the fluid metal out of the runner in three or four separate spirts: this effect, which mostly spoils the castings, is much the most likely to occur with cored works, and with such as are rammed in¬ less judiciously hard, without being, like the moulds for fine cast¬ ings, subsequently well dried. The moulds are generally opened before the castings are cold, and the founder’s duty is ended when he has sawn off the ingates or ridges, and filed away the ragged edges where the metal has entered the seams of the mould; small works are additionally cleaned in a rumble, or revolving cask, where they soon scrub each other clean. Nearly all small brass works are poured vertically, and the run¬ ners must be proportioned to the size of the castings, that they may serve to fill the mould quickly, and supply at the top a mass of still fluid metal, to serve as a head or pressure for compressing that which is beneath, to increase the density and soundness of the casting. Most large works in brass, and the greater part of those in iron, are moulded and poured horizontally. Iron-Founders’ Flasks, and Sand Moulds. —The process of moulding works in sand is essentially the same both for brass and iron castings; but the very great magnitude of many of the latter gives rise to several differences in the methods: it will suffice, however, to advert to the more important points in which the two practices differ, or to those which have not been already noticed ; I shall therefore commence with a few remarks upon the flasks and the sand. In the greater number of cases the iron-founder moulds and casts his work horizontally, with the flasks lying upon the ground ; frequently the top part only is lifted ; and in the largest works the lower part of the flask is altogether omitted, such pieces being moulded in the sand constituting the floor of the foundry ; in these cases the position of the upper flask is denoted by driving a few iron stakes into the earth, in contact with the internal angles of the lugs, or projecting ears of the flasks. The sand would drop out of such large flasks, if only supported around the margin; they are consequently made with cross-bars or wooden stays a few inches asunder, which, unless the entire flask is CASTING AND FOUNDING. 255 made of wood, are fixed by little fillets cast in the solid with the sides of the iron flasks. A great number of hooks in the form of the letter S, but less crooked at the ends, are driven into the bars, and both the bars and hooks are wetted with thick clay water, so that the sand becomes entangled amidst them, and is sustained when the flask is lifted. Some flasks require the force of either two or several men, who raise them up by iron pins or handles projecting from the sides of the flask; they are then placed upon one edge, and allowed to rest against any convenient support whilst they are repaired, or they are sustained by a prop. The very heavy flasks are lifted with the crane, by means of a transverse beam and two long hangers, called clutches, which take hold of two gudgeons in the centres of the ends of the flask ; it can be then turned round in the slings, just the same as a dressing-glass, to enable it to be repaired. The modern iron-founder’s flasks are entirely of iron, and do not require the wooden stays, as they are made full of cross ribs nearly as deep as the flask itself, and which divide its entire surface into compartments four or five inches wide, and one to two feet long. On the sides of every compartment are little fillets, sloping opposite ways, so as to lock in the small bodies of sand very effectually. When these top flasks are placed upon middle flasks without ribs, as in moulding thick objects, the two parts are cottered or keyed together, by transverse wedges fixed in the steady pins of the flask ; lifters or gaggers are then placed amidst the sand; these are light T shaped pieces of iron, wetted and placed head downwards, the tails of which are largest at top, so as to hold themselves in the sand, the same as the key-stone of an arch is supported. The gag¬ gers are placed at various parts to combine the sand in the two flasks, and they fulfil the same end as the iron hooks and nails driven into the wooden stays of the old-fashioned flasks. The bottom flask or drag has sometimes plain flat cross-ribs two inches wide (like a flat bottom with square holes), that it may be turned over without a bottom board; and unless the flasks have swivels for the crane, they Lave two cast-iron pins at each end, and one or more large wrought-iron handles at each side, by which they may be lifted and turned over by a proportionate number of men. The sand of the iron-founder is coarser and less adhesive than that used by the brass-founder. The parting sand is the burned sand which is scraped off the castings; it loses its sharp, crystal¬ line character from being exposed to the red heat. The facing- sand is sometimes only about equal parts of coal-dust and charcoai- dust, ground very fine; at other times, either old or new sand is added, and for large thick works a little road-drift is introduced. All these substances get largely mixed with the sand of the floor, and lessen its binding quality, which is compensated for by occa¬ sional additions of new sand, and by using more moisture with the sand; as before extracting the patterns, the iron-founder wets the 256 THE PRACTICAL METAL-WORKER’S ASSISTANT. edges of the sand with a sponge, which has sometimes a nail tied to it to direct the water in a fine stream; for heavy works a water¬ ing pot is used. The green-sand moulds are made, as in the brass-foundry, of the ordinary stock of old moist sand; these are often filled as soon as they have been made. The dry-sand moulds are made in the same manner, but with new sand containing its full proportion of loam; these moulds are thoroughly dried in a large oven or stove, and then black-washed or painted with thin clay water containing finely ground charcoal; this facing is also thoroughly dried before the moulds are poured. The loam moulds, which are much used for iron castings and somewhat also for those of brass, are made of wet loam with a little sand, ground together in a mill to the consistence of mortar; the moulds are made partly after the manner of the bricklayer and plasterer, as will be explained ; the loam moulds also are thoroughly dried, black-washed, and again dried, as from their greater com¬ pactness they allow less efficient escape for the vapor or air, and therefore they must be put into the condition not to generate much vapor when they are filled. Iron moulds are also employed for a small proportional number of works which are then called chilled castings ; these were referred to at pages 163 and 164; and occasionally the methods of sand cast¬ ing and chilling are combined, as in some axletree-boxes, which are moulded from wooden patterns in sand, and are cast upon an iron core. To form the annular recess for oil, a ring of sand, made in an appropriate core-box, is slipped upon the iron mandrel, and is left behind when the latter is driven out of the casting. It would be a useless repetition to enter into the details of mould¬ ing ordinary iron works; but from the horizontal position of the flasks it is necessary that the part of the work which is required to be the soundest, and most free from defects, should be placed down¬ wards, as the metal is more condensed at the lower part, and free from the scoria or sullage which sometimes renders the upper sur¬ face very rough and full of minute holes. As the flasks almost always lie on the ground, it is also found the most convenient to retain them in contact by placing heavy weights upon them; the foundry should in consequence have an abundant supply of these. The flasks require to be poured through a hole in the upper half, as seen at r, Fig. 169, page 259, which hole is formed by placing a wooden runner stick in the top part A, whilst it is being rammed; and a small channel is afterwards cut sideways into the mould. Sometimes two, three, or even half-a-dozen or more run¬ ners are put to one single casting, either when it requires a great weight of metal, or when it is large but slight, as in trellis-work, in which case the metal might cool before filling the mould if only introduced at one single runner. When the runners are required to be lofty, either to supply pres¬ sure to the metal, or as a reserve to fill up the space left by its con- CASTING AND FOUNDING. 257 traction in cooling, iron rings of six or eight inches diameter are piled up to the required height, to support the tube of sand con¬ tained within them. Small objects that are poured from one hole, are frequently moulded with two runners, that the metal may flow through the mould, and that there may be a sufficient supply to meet the shrinkage, and also to supply head or pressure; another advantage also results, as it assists in carrying off the scoria or sullage. The iron-founder employs all the methods of coring explained at pages 245 to 248, and also others of an entirely different kind but little required in brass-works ; namely for lateral holes in the parts of the castings buried beneath the general surface of the mould, and which are explained by the Figs. 158 to 161. Thus 158 repre¬ sents the finished casting, 159 the model of the same, 160 the ap¬ pearance of the bottom flask or drag when the pattern is first re¬ moved, and 161 the flask and cores when closed ready for pouring ; the moulds are inverted, and the same letters of reference refer to similar parts of all these figures. Figs. 158 159 d 160 a 161. b a The core print a, would deliver from the sand and leave the cavity at a, Fig. 160, to be afterwards filled by the core shown black in Fig. 161, the same as formerly explained at Fig. 143, p. 245. But the core print, b, Fig. 159, (which has reference to the black stud b, Fig. 161,) would tear away the sand above it in with¬ drawing the pattern; therefore the print b should, like d, Fig. 159, extend to the face of the pattern, or the parting line represented by e, Fig. 161. This being the case, the pattern would leave the space denoted at d, Fig. 160; the core is put down sideways to the bot¬ tom of the recess, and extends entirely across the same; the small open space above, is made good with the general surface, as shown by the shade lines in Fig. 161, and this filling in at the same time fixes the core precisely where denoted by the print d, which latter has a mark to show to the moulder where the core is to end. The circular hole requires the core print shown at c, Fig. 159 ; the cores themselves are made in the core-boxes 144 and 145, before ex¬ plained at page 246. Fig. 163 represents the model and core-print, from which the finished casting shown at Fig. 162 might be made from a solid pat tern in a two-part flask; it would be inverted, and the parting would be made upon the line, x. The prints for the four holes a a, would be placed in the top flask, and those for the great apertures or panels d, would be made in a core-box of the express form, and 17 258 THE PRACTICAL METAL-WORKER’S ASSISTANT as thick as the pattern and core-print measured together. The core would be deposited edgeways into the core-print, and the upper corners of the mould would be made good, as explained in Fig. 161. Figs. 162 163 164 By the same method, a mortise wheel, or one with spaces around its edge, as at m m, Fig. 164, to be filled with wooden cogs, might be made with a series of core-prints, as at c, brought up flush with the parting of the mould ; if every print were filled with a core such as Fig. 165, made in an appropriate core-box, the matter would be accomplished with great facility and truth. The iron-founder makes frequent use of flasks, which divide in three or four parts; this is done in many cases simply to increase the depth of the contained space; in which case when wooden flasks were employed, they admitted of being temporarily fixed together by dogs, or large iron staples, driven a little way into the neighbor¬ ing flasks, but the modern iron flasks are fixed by cotters. The following examples will show the nature of some other uses to which the flasks with several partings are applied. Fig. 166. Fig. 167. A casting, such as Fig. 166, which represents the top of a sliding- rest for a lathe, might be rnoulded in a very deep two-part flask, if the parting were made upon the dotted line a, a ; but there would be very great risk of tearing down the mould in drawing out the pattern, and from the depth, there would be scarcely a possibility of repairing it, and the metal would probably be strained. It would CASTING AND FOUNDING. # 259 be also possible to mould it with, the joining upon the line b, pro¬ vided several cores were employed, but the mode adopted is more convenient than either of these—when the pattern is made in two parts, and the flask in three, as in Fig. 167. A and B are first united and partly filled with sand, the pattern is knocked in as represented, and the whole well rammed, especi¬ ally in the groove, the parting being made on the line, 1, 1, and dusted. C is now put on, filled, and struck off level, a board is put above it, and ABC are all turned over together, A becoming the top. A is now removed, and the sand is cut away to make the second parting on the line 2, 2, after which A is replaced, and the run¬ ner-stick is inserted to make the runner, r. On removing the pat¬ tern, the runner-stick r is first taken out, A, or the top part of the flask, is lifted off, and the white part of the pattern is drawn out; B, or the middle part, is then lifted, and the last or shaded piece of the pattern, is drawn out of the mould, which is now put to¬ gether again, and poured through r ; so that the top surface of the pattern, as seen in both views, becomes the face, from being cast downwards, or upon the lowest piece C, of the flask, called the drag. The part c, Fig. 166, might be cast with a chamfer in three dif¬ ferent ways; although, in small castings, it is more usual to cast it square and plane it out of the solid. First, the pattern might be moulded square, and the top A, after removal, might be worked to the angle by aid of the trowel and a chamfered slip of wood, used as a gage; or secondly, by the employment of a core, the print of which is represented by the dotted lines terminating at the angle d, Fig. 166 ; or thirdly, by having a loose slip on the pattern sliding on the line c, Fig. 166, so as to be drawn off when the top A, had been lifted. This last method is analogous to that represented in Fig. 168, also intended for a sliding-rest ■ and which might be cast Fig. 168. Fig. 169. in a two part flask, if the two camfers c c, were fitted loosely upon slides as shown; but a three-part flask is more convenient, as ex¬ plained by Fig. 169, in which the pattern is inverted. 260 THE PKACTICAL METAL-WOEKEK’S ASSISTANT. The lowest piece C, or the drag, is parted upon the line 1, 1, but its sand extends upwards between the two sides of the pattern, as shown by the shade-lines. The middle piece B, is parted through the line 2 2 ; and lastly A. the top, is filled up level, the runner- stick at r being inserted at the time, A is first lifted, and all the pattern is then removed, excepting the chamfered bars and their slides, which are represented black; this pattern delivers its own cores for the circular mortises m m, the sand forming them being a part of that in B, or the middle flask; lastly, B is lifted, and chamfer-slips are picked off from C. This pattern may conse¬ quently be moulded without turning over the flask, and every part of the mould is quite accessible for repair. The pedestal of the swage-block, Fig. 95, page 141, is another good example of moulding in a three-part flask. The model is made with the upper fillet loose, also with the sides solid, or with¬ out the holes, and the object is moulded as it stands. The top part of the flask opens at the upper moulding, and which latter is then removed from the pattern; the middle flask divides at the plinth or flange, so that when this has been lifted, the pattern also may be withdrawn, leaving a square pedestal of sand, as large as the interior of the model, standing upon the bottom part or drag, as in 169. The panels are made by means of a core-box of the kind Fig. 146, p. 246, the box is exactly as thick as the metal to be cast; and the circular cores are then fixed upon the pedestal of sand by means of a few wires or nails, after which the fla-sk is put together, ready for pouring. If the Fig. 95, here referred to, had four fluted columns at the four angles, either with a large cap to each, or with a square entab¬ lature connecting the whole of them, the object might be also cast in one piece, if moulded in a three-part flask. After removing the top flask, the entablature and capitals would be first withdrawn, the columns being divided through their smallest diameters; the mould would be then turned over, and upon lifting off the drag, or bot¬ tom-piece, the remainder of the pattern could be drawn, either in one single piece, or if the pillars were loose, the five parts could be more safely extracted; the three-part mould would be put together again and reversed for pouring. In this general manner, by mak¬ ing either the mould, or the pattern, or both, in different pieces, and by the judicious employment of cores and drawbacks, objects apparently the most untractable are cast with very great perfection. The iron-founders are likewise very dexterous in making cast¬ ings in some respects different from the patterns from which they are moulded ; thus, if the pattern be too long, or that it be tem¬ porarily desired to obliterate some few parts, the mould is made of the full size and stopped-off, additional sand being worked into the mould by aid of the trowel and some temporary piece of wood to represent the imagined termination of the pattern. On the other hand, any simple enlargement or addition is not always added to CASTING AND FOUNDING. 261 * the pattern, hut it is frequently cut out of the mould with the trowel, in a similar manner. Many common works, such as plates, gratings, parts of ordinary stoves, and simple objects, are made to written measures, and with¬ out patterns, as a few parallel slips of wood to represent the margin of the casting, are arranged for the purpose upon a flat body of sand, which is modelled up almost entirely by hand; but for all accurate purposes and for machinery, good and well-made patterns are indispensable, and to some particulars of which a little atten¬ tion will be now devoted. Remarks on Patterns for Iron Castings. —The construc¬ tion of patterns for iron castings requires not only the observance of all the particulars conveyed on pages 238 to 240, but, in ad¬ dition, the large size of the models, the peculiar methods employed in moulding them, and the nearly inflexible nature of the iron cast¬ ings when produced, call for some other and important considera¬ tions,—and which should not be entirely overlooked, even in works of comparatively small size, or it may lead to failure and disap¬ pointment. Thus, it becomes necessary to make patterns in some degree larger than the intended iron castings, to allow for their contraction in cooling, which equals from about the ninety-fifth to the ninety- eighth part of their length, or nearly one per cent. This allowance is very easily and correctly managed by the employment of a con¬ traction rule, which is made like a surveyor’s rod, but one-eighth of an inch longer in every foot than ordinary standard measure. By the employment of such contraction rules, every measurement of the pattern is made proportionally larger without any trouble of calculation. When a wood pattern is made, from which an iron pattern is to be cast, the latter being intended to serve as the permanent foundry pattern, as there are two shrinkages to allow for, a double contrac¬ tion rule is employed, or one the length of which is one-quarter of an inch in excess of every foot. These rules are particularly im¬ portant in setting out alterations in, or additions to, existing ma¬ chinery. The latter is measured with the common rule, and the new patterns are set out, to the same nominal measures, with a single or double contraction rule, as the case may be, the three being made in some respects dissimilar to avoid confusion in their use. The entire neglect of contraction rules incurs additional trouble and uncertainty. The contraction of brass is nearly three- sixteenths of an inch in every foot, but from the small size of brass castings the contraction rule is less required for them, as the differences may be easily allowed for without it. Iron castings weigh about fourteen times as much as the ordi¬ nary deal and fir patterns from which they are made, that being nearly the ratio of the specific gravities of those materials. Patterns for iron castings are much more frequently divided into several parts than those for brass. For instance, the division into 262 THE PRACTICAL METAL-WORKER’S ASSISTANT. two equal parts, after the manner of Fig. 153, p. 248 (but without reference to the under-cutting) is very common, as both the pattern and flask separate when the top part is lifted, and the halves of the pattern can then be drawn out from the halves of the flask with much less risk of tearing down the sand. Referring to p. 232, Fig. 122 if small, would be moulded as rep¬ resented, with false cores or drawbacks; but if it were a large fluted column, the iron-founder would employ a solid two-part flask ; the shaded parts would together represent the body of sand in the drag, and the pattern would be made in three parts some¬ thing like a boot-tree. When the top flask had been lifted, the central slice of the pattern, extending from the two upper to the two lower angles, would be withdrawn vertically, and the two outer pieces would be released sideways. The general rule is to divide the circumference of the pattern into six equal parts, and to let the central slice equal one of them in width. The Figs. 167 and 169, representing two parts of a slide-rest, and the pedestal, 95, are some amongst many of the common ex¬ amples of the division of the patterns; and with which may be associated, the numerous subdivisions of the mould instead of the pattern by the employment of cores, many applications of which have been also explained. All these matters display much in¬ teresting and ingenious contrivance, resorted to either to render pos¬ sible the operation of moulding, or to facilitate its performance. To lessen the distortion of castings from their unequal contrac¬ tion in cooling, it is important that the models should be nearly symmetrical. For example, bars or rods of all the sections in Fig. 121, p. 232, may be expected to remain straight; perhaps g is the most uncertain, but if the lower fins of e and h were removed, their flat surfaces, then exposed to the sand, would become round¬ ing or convex in length, from the contraction of the upper rib being unopposed by that of a similar piece on the under side. Bars and beams, the sections of which resemble the letter I, are of the most favorable kind for general permanence, and also for strength, and large panels may be cut out from their central plates to diminish their weight without materially reducing their stability. They are much used, not only in building, but also in the framing of machinery, which is in a great measure based upon the same general rules. It is also of great importance, especially in castings of large size, that the thickness of the metal should be nearly alike through¬ out, so that it may cool at all parts in about the same time. Should it happen that one part is set or rigid, whilst another is semi-fluid or in the act of crystallizing, there is great risk of the one part being altogether torn from the other and producing fracture. Or should the disturbing force be insufficient to break the casting, it may strain the metal nearly to its limit of tenacity or elasticity; so that a force far below that which the casting should properly bear may break it in pieces. CASTING AND FOUNDING. 268 An example of this is seen in wheels with very light arms and heavy rims or bosses. The arms sometimes cool so quickly as to tear themselves away from the still hot rim or nave ; or when the arms are solidified without fracture, the contraction of the rim may so compress the spokes endways as to dish the wheel (in the man¬ ner of an ordinary carriage wheel), and thereby strain the casting nearly or quite to the point of fracture. The arms are sometimes curved like the letter S, instead of being straight and radial; the contraction then increases their curvature with less risk of accident than to straight arms. It appears to be often desirable to super¬ sede the straight diagonal braces of iron castings by curved lines, which are both more ornamental and better disposed to yield to compression or extension by a slight alteration in their cur¬ vature. A more elegant way of avoiding the mischief is by placing the spokes as tangents to the central boss, in which case the contraction of the rim makes a small angular change of position in the boss; for the rim, in thrusting the spokes inwards, causes the boss to twist round a little way with far less risk of fracture. The destructive irregularity of thick and thin works is partly averted by uncovering the thick parts of the casting, or even cool¬ ing them still more hastily, by throwing on water from watering- pots. In wheels this has been done by a hose, the axis of which is concentric with the wheel, the arms being all the time sur¬ rounded by the sand to retard their cooling; but it is the most judicious in all patterns to make the substance for the metal as nearly uniform throughout as circumstances will admit, so as not to require these modes of partial treatment, which often compro¬ mise the ultimate strength of the casting. Another mode sometimes adopted for avoiding the fracture of wheels, from the great dissimilarity of their proportions, is by in¬ serting wrought-iron arms in the mould, but they do not always unite kindly with the iron of the rim and the nave. The same in¬ convenience occurs when iron pins are inserted in the ends of either iron or brass castings, to serve for their attachment to their respective places. In iron castings it frequently produces the effect of chill casting, so as to render the works difficult to be turned or filed at the junction, and there is risk of the casting becoming blown or unsound in either case. When the pins are heated before being placed in the mould, they become nearly cold before the metal can be poured, and they also endanger the presence of a little steam or vapor, which is detrimental; therefore they are more generally put in cold, notwithstanding the sudden check they then give to the fluid metal. The patterns for iron castings of large size are necessarily very expensive, especially those for hollow cylinders and pans, many of which are so large that it would be impossible to find solid pieces of wood from which the patterns could be made, either with sufficient strength for present use, or with the necessary perma- 264 THE PRACTICAL METAL-WORKER’S ASSISTANT. nence of form for a subsequent period, as they would be almost sure either to break or to become distorted from the effects of unequal shrinking. Such patterns, therefore, require to be made of a great many thin layers or rings of wood, each consisting of 6, 8, or 12 pieces, like the felloes of wheels, so that in all parts the grain may be nearly in the direction of a tangent. As they are glued up, every succeeding layer is connected with the former by glue and wooden pins or dowels, and the whole is afterwards turned to the tubular or hemispherical form, as the case may be. As the castings are generally required to be rather thin, such models are not only very expensive, but also very liable to accident; and besides, it frequently occurs that only one or two castings of a kind may be required, which makes the proportional cost of the patterns excessive. It fortunately happens, however, that this case, which is one of the most costly and uncertain, by the employment of ordinary wood or metal patterns, becomes exceedingly manageable by a peculiar and simple application of the art of turning (the one great centre of the constructive arts, to which these pages are intended immediately and collaterally to apply); and by which process, or one branch of loam moulding, to be explained hereafter, patterns are not generally required. Loam Moulding.— Figs. 170, 171, and 172, are intended to illustrate this process as regards a steam cylinder. Fig. 170 is the Figs. 170 171 172. entire section of the mould in its first stage. Figs. 171 and 172 are the half sections of the second and third stages, preparatory to burying the mould in the pit in which it is to be filled. The inner part of the loam mould is called the core when small, but the nowel when large; the outer is called the case or the cope. Each part is built upon an iron loam-plate, or a ring cast rough on the face, and with four ears by which it may be lifted. The mould is occasionally erected upon four shallow pedestals of bricks for the convenience of making a fire beneath it to dry the loam. At CASTING AND FOUNDING. 265 other times it is made upon a low truck, upon which it may be wheeled into the loam stove, which is heated to about the tempera¬ ture of 300 to 400 degrees Fahrenheit. A vertical axis a, is mounted in any convenient manner, fre¬ quently in two holes in the truck itself, or as shown in the figure, in a pedestal or socket erected upon the truck; at the other times the axis is mounted in a hole in the loam-plate, and in any bear¬ ing attached either to the building or its roof. The first step is to fix upon the spindle, the templet b b, at the distance of the radius of the cylinder, either by one or two clutches with various binding screws. An inner cylinder of brickwork is then built up, plastered by the hands with soft loam (which is re¬ presented black in all figures), and scraped into the cylindrical form by the radius board, which is moved round on its axis by a boy. When the surface is smooth and fair it is thoroughly dried, after which it is brushed over with blackwash, and again dried. The charcoal dust in the blackwash serves as a parting, to prevent the succeeding portions of the loam-mould from adhering to the first. The templet c c, Fig. 171, cut exactly to the external form of the cylinder, is now attached to the axis at the distance from the core required for the thickness of the metal: some additional loam is thrown on to form the thickness, which is smoothed in the same careful manner as the centre, after which the templet and spindle are dismounted, and the thickness, which is represented white in Figs. 171 and 172, is also dried and blackwashed. The ring for the outer case or cope is now laid down, and its position is denoted either by fixed studs or by marks; and the outer case represented in Fig. 172 is built up of bricks and loam, with an inner facing of loam worked very accurately to the turned thickness. The new work or the cope, is also thoroughly dried, and afterwards lifted off very carefully by means of the crane and a cross beam with four chains. This process likewise drags off' the thickness, which usually breaks in the removal; its remains are carefully picked out of the cope, both parts of the mould are repaired, and again blackwashed and dried. When the cylinder requires ports at the ends, or the short tubes with flanges for attaching the steam-passages, models of the tubes are worked into the cope, and are afterwards withdrawn ; the cores are made in core boxes, and are partly supported by the outer ex¬ tremity, and partly upon grains, or two little plates of sheet iron connected by a central wire, the whole being equal to the thick¬ ness of the metal at the part. When steam-passages are wanted, either along the side, or around the cylinder, they are worked up in clay upon the thickness, and duly covered in by the cope; their cores are supported, partly by their loose ends, and partly by grains, which become entirely surrounded by, and fixed in the metal, when it is poured. There is always some uncertainty of the sound union of the 266 THE PRACTICAL METAL-WORKER’S ASSISTANT. •«sg»i grains, or other pieces of iron, with the cast-metal. Some cast them in iron and file them quite bright, others also tin them, ap¬ parently to preserve them from rust, as the tin must be instantly dissipated by the hot metal. Grains should always present clean metallic surfaces, and when used for very thin castings to prevent them from dropping out, the wires are nicked with a file that they may be keyed in the metal. It is however better to avoid the use of grains, which may be generally done by giving the core sand bearings, and afterwards plugging up the holes in the casting. The mould is now put together in a pit sunk in the floor of the foundry, and the two iron plates are screwed together; the surround¬ ing space being rammed hard to prevent the mould from bursting open, but the inner part is left much more loose for the escape of the air. The top edges of the mould are covered over with a bam- cake (which has been previously made and dried), or a ring three or four inches thick, strengthened with iron bars amidst the clay, the joining being made air-tight by a little cows’ hair, and by the pressure of a quantity of iron weights; the loam-cake is generally perforated with many holes as shown at d, for the entry of the metal and the escape of the air. But provision must always be made in casting thin cylinders, boxes, and such like forms, for the breaking up of the core as soon as the metal is set, to prevent the metal scoring or rending from its contraction upon a rigid unyield¬ ing centre. To enable the mould to resist the great pressure of the lofty column of fluid metal (equal at the base to near 60 pounds on every square inch), the core is strengthened by diametrical iron bars entering slightly into the brickwork: the outer cylinder is surrounded at a small distance by iron rings piled one on the other, the interval being rammed with sand ; and stays are placed in all directions from the rings to the sides of the pit, which is either lined with brick-work, or when liable to be inundated with water, it is made of iron, like a water-tight caisson. Small cylinders are moulded in sand from wooden models, and only the cores are turned in loam; for cylinders of the smallest size the cores are made of sand in core boxes as already explained. Large pans, and various other circular works, are moulded pre¬ cisely in the same way as cylinders; except that curved templets are used, and that towards the conclusion, the apertures through which the spindle passed are filled in and worked by hand to the general surface. Water-pipes are made much in the same mode, but the cores for these are turned upon an iron tube pierced full of holes, which is laid horizontally across two iron trestles with notches, and is kept in rotation by a winch handle at the end: there is also a shaper- board or scraper fixed parallel with the axis; this primitive apparatus is called a founder’s lathe. The perforated tube (serving as the mandrel) is first wound round with hay-bands, then covered with loam, and the core is CASTING AND FOUNDING. 267 turned, dried and blackwashed; the thickness is now laid on and also blackwashed, after which the object is moulded in sand. The thickness is next removed from the core, which latter is inserted in the mould, and supported therein by the two prints at the extrem¬ ities, and by grains with long wires, the positions of which may be seen by the little bosses on the pipe, the metal being there made purposely thicker to avoid any accidental leakage at those parts. When pipes are cast in large quantities, they are moulded from wooden patterns in halves, so that it only becomes necessary to turn the core, and this, when made in the above manner, is sufficiently porous for the escape of the air. The moulds for crooked pipes and branches are frequently made in halves, upon a flat iron plate. An iron bar or templet of the curve required is fixed down, and a semicircular piece of wood, called a strickle, is used for working and smoothing the half core; next a larger strickle is used for laying on the thickness, the two halves are then fixed together by wires, and moulded from in the sand flask; the thickness is now stripped off the core, which is fixed in the mould by its extremities, and if needful, is supported also upon grains. By the employment of these means, although the loam work re¬ quires time for the drying, yet with ordinary care an equality of thickness may be maintained, notwithstanding the complexity of tine outline, and without the necessity for wooden patterns. Very many of the large works in brass are also moulded in loam, the management being in most respects exactly the same as for iron, except that in some ornamental works wax is more or less employed, and is melted out of the moulds before the entry of the metal; a very slight view of the methods will serve as a sequel to the subject of brass founding. Large bells are turned in almost the same manner as iron cylin¬ ders or pans, by means of wooden templets, edged with metal and shaped to the inner and outer contour of the core and thickness. The inscription and ornaments are either impressed within the cope, the clay of which is partially softened for the purpose, or the orna¬ ments are moulded in wax, and fixed on the clay thickness before making the cope. Less generally the whole exterior face of the bell, or indeed its entire substance, is modelled in wax, and melted out before pouring. In any case, the concluding steps in filling up the apertures where the spindle passed, are to attach a dissected wooden pattern of the central stem and of the six cannons or ears by which the bell is slung, which parts are moulded in soft loam; and then, the parts having been dried and replaced, and the iron ring for the clapper inserted, the whole is ready for the pouring pit. The heaviest bells are moulded within the pit the same as huge cylinders. Brass guns are also moulded in loam, and in a somewhat peculiar manner; a taper rod of wood much longer than the gun, is wound round with a peculiar kind of soft rope, upon which the loam is put 268 THE PRACTICAL METAL-WORKER’S ASSISTANT. for making the rough casting model of the gun, which is turned to a templet; the work is executed over a long fire to dry it as it proceeds, and the model is made about one-third longer than the gun itself. The model when dried and blackwashed all over, is covered with a shell of loam, not less than three inches thick, secured by iron bands, the shell is also carefully dried; after this the taper bar is cautiously driven out from its small end, the coil of rope is pulled out, and so likewise is every piece of the clay model of the gun. The parts for the cascable and trunnions, which should have been worked separately upon appropriate wooden models, are then attached to the shell. Should the gun have dolphins, or any other ornamental figures, now seldom the case, they are modeled in wax and fixed on the clay model before the shell is formed, and are then melted out to make the required space for the metal. When all is ready and dried, six, eight, or more of these loam cases, or shells, are sunk perpendicularly in a pit at the mouth of the reverberatory furnace, and the earth is carefully rammed around them; at the same time a vertical runner is made to every mould, to enter either at the bottom, or not higher than the trunnion: the upper ends of the runners terminate in the bottom of a long trough or gutter, at the far end of which is a square hole, to receive the excess of metal. In casting brass guns, tapping the furnace is rather a ceremony, and certainly an imposing sight: the middle and the end of the trough, are each stopped by a shovel or gate held across the same; and the runners are all stopped by long iron rods, held by as many men. When all is pronounced to be ready, the stopper of the fur¬ nace is driven inwards with a long heavy bar swung horizontally by two or three men, and the metal quickly fills the trough ; on the word of command, “ number one , draw,' 1 ' 1 the metal flows into the first mould, and fills it quickly but quietly from the bottom; the mould being open at the top, no air can be accidentally enclosed. Numbers two, three, and four are successively ordered to draw. The first shovel is then removed from the great channel, and now the guns, five to eight or ten, as the case may be, are similarly poured and filled to the level of the trough; after which the last shovel is withdrawn, and the residue of the metal is allowed to run into the square bed or pit prepared for it. The flow of metal from the furnace is regulated by the tapping bar, the end of which is taper, and is thrust more or less into the mouth of the furnace as required ; the trough and runners are thus kept exactly full, which is an important point in most cases of pouring, as it prevents a current of air being carried down along with the metal. Large bells are poured much in the same manner, except that the runners are at the top, and the metal runs from the great channel, through smaller gutters to every sunk mould, the stoppers for which are successively drawn. For quantities of brass inter¬ mediate between the charge of an ordinary crucible, and such as CASTING AND FOUNDING. 269 require the reverberatory furnace, the large ladles or shanks of the iron-founder are used; the contents of four or six crucibles being poured into the shank as quickly as possible, and thence in one stream into the mould. The author of the article Founding, in the Encyclopedia Metropo- litana, minutely describes three ways of casting large hollow statues, which are briefly as follows: First: a rough model of the figure is made in clay, but somewhat smaller than its intended size; it is covered over with wax, which is modeled to the required form, or the wax is worked up in sep¬ arate pieces and afterwards attached: various rods or cylinders of wax to make the apertures for the runners or air holes, are fixed about the figure and led upwards. The whole is now surrounded with a coating of loam and similar materials, the inner portion of which is ground very fine and laid on with a brush like paint; and the outer part is secured with iron bands. When all has been partially dried a fire is lighted beneath the grating on which the figure is built, to cause the wax to run out through one or more apertures at the base, which are afterwards stopped, and all is thoroughly dried and secured in the pit, after which the charge of the furnace is let into the cavity left by the wax. Secondly: the finished figure is modeled in clay, and stuck full of brass pins just flush with its surface, which surface is now scraped away as much as the thickness required in the metal; the reduced figure is now covered with wax mixed with pitch or rosin, which is worked to the original size with all the exactness possible. The other stages are the same as in the foregoing; the metal studs or pins prevent the mould and core from falling together, and they afterwards melt, becoming a part of the metal constituting the figure. Thirdly: the finished figure is modeled in plaster, and a piece- mould is made around it, the blocks of which consist internally of a layer of sand and loam 1J inch thick, and externally of plaster one foot thick. The mould when completed is taken to pieces, dried, and rebuilt in the casting pit; it is now poured full of a composition suitable for the core, the mould is again taken to pieces, the core is dried and scraped to leave room for the metal, and all is then put together for the last time, secured in the pit and the statue is cast. The first plan is the most wasteful of metal, the third, the least so, although it is the most costly when the time occupied is also taken into account; but it has the advantage of saving the original work of the artist. Melting and Pouring Iron.— Iron is usually melted in a blast furnace, or as it is more commonly called, a cupola; although the cupola or dome leading to the chimney, from which it would ap¬ pear to have derived its name, is frequently omitted, the two or three furnaces being often built side by side in the open foundry. At the basement there is a pedestal of brickwork about 20 to 30 270 THE PRACTICAL METAL-WORKER’S ASSISTANT. inches high, upon which stands a cast-iron cylinder from 30 to 40 inches diameter, and 5 to 8 feet high; this is lined with road-drift, which contracts its internal diameter to 18 or 24 inches. The fur¬ nace is open at the top for the escape of the flame and gases, and for the admission of the charge, consisting of pig-iron, waste of old metal, coke and lime, in due proportion. The lime acts as a flux, and much assists the fusion ; chalk is considered to answer the best, but oyster shells are very commonly used where they are abun¬ dant. At the back of the furnace, there are three or four holes one above the other for the blast, which is urged by bellows or by a re¬ volving fan. No crucible is used, and as the fluid metal collects at the bottom of the furnace, the blast pipe is successively removed to a higher hole, and the lower blast hole is stopped with sand, which partly fuses and secures the blast hole very effectually. The front aperture of the furnace through which the metal is allowed to flow into the ladles or trough, is usually made sufficiently large for the purpose of clearing or raking out rapidly the fuel and slag, as the process is most laborious owing to the excessive heat. This aperture is closed by a guard-plate, fixed on by staples attached to the iron-case of the furnace, in the centre of which plate the tapping hole is made: during the time the metal is fusing the tap hole is closed by sand well rammed in, and this if well done is never found to fail. Many iron furnaces are made octangular, and in separate parts bound together by hoops, so that in the event of the charge becom¬ ing accidentally solidified in the cupola, the latter may be taken to pieces for its removal, and thus avoid the necessity of destroying the. furnace. There is frequently a light framing or grating above the furnace, upon which the small cores are placed that require to be dried. In some foundries the cupolas are built just outside the moulding shop, beneath one or more chimneys or shafts, which carry off the fumes; in such cases the fronts of the furnaces are accessible through an aperture in the foundry wall, with which they are nearly flush; when the furnaces are lofty there is a feeding stage at the back, from which the charge is thrown in. For heavy iron castings, which sometimes amount to thirty tons and upwards in one piece, reverberatory or air furnaces are also commonly used; the ordinary charge for these is four to six tons of iron, and five or six furnaces «re commonly built close together, so that they may be simultaneously tapped in the production of such enormous works. For melting iron in the small way, good air furnaces may be used, and also some of the black-lead furnaces, 'which are blown with bellows, but this is one of the processes that is not successful upon a limited scale. Considerable judgment is required in proportioning the charge for the iron furnace, which always consists of at least two, and often CASTING AND FOUNDING. 271 of half-a-dozen kinds of new pig-iron mixed together, and to which new iron a small proportion of old cast-iron is usually added. The kinds and qualities used are greatly influenced by local and other circumstances, so that nothing can be said beyond a few general remarks. When the principal object is to obtain sound castings with a very smooth face, as for ornamental works not afterwards wrought, the soft kinds of iron containing most carbon, which are most fusible and flow easily, are principally used. But such metal would neither possess sufficient hardness, durability, nor strength, for many of the castings employed in the construction of edifices and machinery. If the cupola contained a little hard pig-iron, but were in great measure filled with the old cast-iron, which had been repeatedly melted and had become successively harder from the loss of carbon at every fusion; such castings would be brittle, and sometimes so hard as scarcely to admit of being cut; these would be equally unfit for the generality of machinery from the opposite causes. But the same mixture of iron will be found to differ very much according to the size of the objects in which it is cast. Iron which in a plate one-fourth of an inch thick may be quite brittle and hard, will mostly be of good soft and useful quality in a stout bar or plate of two or three inches thick. Thick castings are necessarily slow in cooling, and are seldom very hard unless in¬ tentionally made so. Between the extremes (say three parts of pig-iron to one of old, or three parts of old iron to one of pig-iron), various qualities may be selected. In castings for machinery the general aim is to obtain a strong, sound, and tough iron. Mixtures of this nature which are usedfor iron ordnance are called gun-metal amongst the gun-founders. The fireman, or the individual having the management of the furnace, therefore always employs the scales in mingling the dif ferent kinds of iron, according to the magnitude and character of the works to be cast; and until the sorts in use are familiarly known, it is partly a matter of trial, and requires the same atten¬ tion as the making of alloys, properly so considered. It is much to be regretted that no protection has yet been found to prevent the conversion of cast-iron into plumbago, or the car¬ buret of iron, from long immersion in sea-water, or the water of copper mines, sewers, and other places. This, which is a most serious inconvenience in dock works, sea walls and mines, arises, says Dr. Michael Faraday, from the circumstance that the protoxide of iron, formed beneath salt water, is soluble, .and becomes washed away, thus robbing the original mass of its iron; whereas the peroxide, or ordinary rust formed by exposure to the air, is in¬ soluble, and serves partly as a defence to the metal beneath. When first raised from the sea-water the plumbago becomes ex¬ ceedingly hot from the action of the atmosphere. It may be cut with a knife like an ordinary pencil. When enough iron is melted (the common charge being two and 272 THE PRACTICAL METAL-WORKER’S ASSISTANT. a half to four cwt., but sometimes above twelve tons), the cupola is tapped in front, at a hole close to the bottom, which allows the whole contents to run out, either into ladles or, in very large works, into channels leading directly to the moulds. The furnace is not unfrequently tapped whilst the charge of metal is being melted, and in such cases when the required quantity has been removed into the ladles, the fireman re-stops the tap-hole by a conical plug of clay on the end of a wooden bar. The process is called hotting, and requires a dexterous hand, or the whole contents of the fur¬ nace may escape. In pouring iron, the means of conveying the melted metal to the flasks differ with the quantity. One man will carry from fifty to seventy pounds in a hand-ladle ; three to five men will carry from two to four cwt. in a double hand-ladle, or a shank ; larger quan¬ tities, amounting to sometimes from three to six tons, are carried in the crane-ladle. These all possess one feature in common, namely, their handles or pivots are placed but slightly above the centre of gravity of the ladles,—they may therefore be tilted very readily, as their fluid contents in obeying the law of gravitation are almost neutral in the operation of tilting, which they scarcely assist or retard, unless by mismanagement the ladle is over-filled, and thus rendered top-heavy. All these ladles are coated with a thin layer of loam, and every time before use they are brushed over with black wash and care¬ fully dried. The hand-ladle has a handle three or four feet long, with a crutch or cross piece at the end, which is mostly held in the left hand. Frequently the contents of half-a-dozen or more hand-ladles are poured simultaneously into the same flask. The shank has a single handle on the one side, and one made in two branches at the other, and together they measure six to eight feet in length. The tilting is completely under the command, of the one or two men at the double handle. The crane-ladle is carried from the furnace to the mould by the swinging and traversing motions of the crane, which is similar to those used at the iron forges, etc. (see p. 87), and in very large foundries the plan of the building is divided into imaginary squares, with a crane in the centre of every square, so that the ladle is walked from one to the other, even to the far end of the shop, with great facility and expedition. The bail or handle of the crane-ladle is fixed in its perpendicular position by the guard, a simple bolt, which prevents the ladle from being overset by accident until it has reached its destination. Two long handles, terminating in forked branches, are now fitted by their square sockets upon the swivels or pivots of the crane-ladle, and secured by transverse keys,—after which the guard is with¬ drawn ; and then the two men at the ladle, two others at the crane, and one to skim the dross from the lip of the ladle, commonly suffice to manage two or three tons and upwards of fluid iron with great ease and dexterity. CASTING AND FOUNDING. 278 It has added to the pivot of the large crane-ladle a tangent-screw and worm-wheel, by which it may be gradually tilted by one man standing directly in front at any convenient distance; and another man skims the metal by a kind of throttle-valve coated with clay, which sweeps into the lip of the ladle and keeps back the sullage: the axis of the skimmer is continued as a long rod at right angles to the first, and also terminating in a cross. By these arrange¬ ments any precise quantity of metal can be delivered, and the risk of accident scarcely exists. The observations offered on p. 252 respecting the temperature of the metal suitable to different brass works, might be here in a great measure repeated—namely, that the smallest castings require very hot metal, and a gradually lower temperature is more suita¬ ble to works progressively heavier, to avoid their becoming sand- burned or rough on the face from the partial destruction of the mould. When cast-iron is very hot, the metal scintillates most beautifully, far more vividly than a mass of wrought-iron raised above the weld¬ ing heat; as the metal cools, the sparks become intermittent, and at last the metal remains entirely quiet, excepting a multitude of lines vibrating in all directions, as if the surface were covered with thousands of wire-worms in great activity ; this effect lessens until the metal solidifies. The softest iron shows most of this play of lines, or is said to break the best. Iron castings are generally much heavier than those of brass, and the melting heat of the metal being considerably higher, the quantity of gas generated is very much greater; additional care is consequently required to provide for its escape, or the explosions are much more violent. The sand is punctured at many places with a fine wire, before the removal of the patterns; sometimes also more coarsely as soon as the metal has become solidified. The gases issuing from the filled moulds are often lighted, either by the red-hot skimmer, or by a torch of straw with which the moulds are flogged: this lessens the accumulation of gas and the consequent risk of accident. The pouring of very large objects in open moulds, such as plates, beams and girders, is a very beautiful and grand sight. The metal is led from the furnace through a gutter lined with sand, into a large trough or sow, the end of which is closed with a shuttle; when the sow is full, the shuttle is raised; this allows the metal to flow very quickly into the mould, but enables it to be kept back should it be unnecessarily hot; the castings made in open moulds are generally covered up with sand as soon as the metal is set. The above, and the casting of smaller objects, such as flat plates in open moulds, may appear amongst the most certain modes of procuring sound castings; but unless the air be well drawn from the lower surfaces, they will become honeycombed or full of air- bubbles. This defect is avoided by making the sand-bed sufficiently 18 274 THE PRACTICAL METAL-WORKER’S ASSISTANT. porous, and pricking it with many holes just below the surface, to serve as horizontal mV-drains. A far greater number of works are cast in close moulds, and in the horizontal position; the proportionate quantity of metal is car¬ ried to them in ladles; skimmers are held to the lips of the moulds at the time of pouring, to keep back all the sullage or dross. The number, position, and height of the runners, are determined by cir¬ cumstances ; generally not less than two apertures are provided, the first for the entry of the metal, the second for the escape of the air, and to allow the metal to flow through the mould and carry off'the sullage. Sometimes in heavy castings, in addition to the runners one or more large heads or feeds are made at the upper part, to supply fluid iron as the metal shrinks in the act of solidifying; and in some such cases the feed is pumped, by moving an iron rod up and down in the feed to keep the metal in motion, so that for a time the metal may freely enter and the air escape, to increase the general sound¬ ness of the mass. The pumping should, however, be discontinued the moment the metal begins to stiffen and clog the iron rod, or in other words to crystallize, otherwise mischief instead of benefit will accrue. Works which are required to be particularly sound, as some cylinders, pipes, shafts and plungers, are cast vertically; the moulds are sunk in the earth, and well rammed to enable them to with¬ stand the great pressure of the fluid column, without becoming strained or bursting open. Such objects are moulded and poured with a head, or an additional portion about one-third the length of the finished casting, as mentioned in respect to brass guns. In pouring cylinders of tolerably large size, the metal is conducted from the sow through two sunk passages with side branches, en¬ tering the mould in the direction of tangents about one-third from the bottom; these keep the metal in circulation, and assist the rise of the sullage; cylinders are also poured through holes in the loam cake, other apertures being always provided in it for the escape of the air. Beneath the iron plate upon which the mould is built, is placed a central mass of hay-bands, in order that the air may have free passage to collect, and then to escape upwards to the surface of the earth, through one, two, three, or more internal or external tubes, as the case may be. The thick cylinders for hydrostatic presses are closed at one end, and those cast with the mouth down¬ wards, require an air tube bent at each end, to lead from the core beneath the casting to the surface of the earth; the gas drives out in a stream, and is immediately ignited like a great torch: others prefer casting them with the mouth upwards, in order that less risk may exist of locking up air within the casting. For the very heaviest works the three or four furnaces are usually tapped at the same moment, the stream from every one is conducted through a sand trough, and they all unite in one great trunk leading to the mould. CASTING AND FOUNDING. 275 In pouring some of the largest cylinders, the trough is led en¬ tirely round the top of the loam mould, and from the circular channel, sometimes as many as thirty runners, every one of which is stopped by a shovel held by a man or a boy, descend to the mould, and as many air holes are made between the ingates. When the foreman sees that all the furnaces are in full run, and that the channels are well supplied, he gives the word, “up shovels they rise at the instant, and allow the molten stream to deposit itself in its temporary resting-place. At the time the cylinder is poured, all the precautions explained, p. 266, are necessary to give the mould sufficient strength to resist the pressure of the fluid metal; but as soon as it becomes set, the conditions are altered, and this resistance must be removed from the inner surface, that the cylinder may shrink in cooling without restraint or fracture. Accordingly, after three or four hours’ time, all the diametrical iron stays are knocked away by a vertical weight or monkey, and men descend by iron ladders into the cylinder, to break down the brick core. The heat is so terrific, that they can only endure it for a minute or so at a time, but still the precaution is imperative.: and even in comparatively small castings of hollow objects, such as cylinders, pans, and boxes, it is desirable to break down the cores, to prevent the castings from scoring or breaking. Although some iron castings employed for bridges, girders, and even for machinery, require the enormous quantities of iron re¬ ferred to, on the other hand this useful metal is employed for exceedingly light and beautiful castings, abundant examples of which may be seen in the Berlin ornaments and chains. The links of most of the Berlin chains are connected with wrought- iron wire, but Figs. 173 and 174 represent a chain made entirely by the process of casting. Figs. 173 b 174. b Its length is 4 feet 10 inches. It consists of about 180 links, and weighs If oz. avoirdupois. It was thus made: The larger links a a were first cast separately; a solid model of the chain about 8 inches long, with core prints, as in Fig. 174, was then moulded. The links a, previously smoked to prevent the adhesion of the metal, were first laid in the mould, and afterwards the sand cores b b, and a separate runner was made to every one of the small links cc, so as to unite the whole when poured. The concluding duty of the iron-founder is to remove the cast 276 THE PRACTICAL METAL-WORKER’S ASSISTANT. ings from the mould and to break off the runners. After this all the loose sand (which is reserved for making the partings of future moulds) is scraped off with iron shovels and wire scratch brushes, and the seams are smoothed oft' with chisels and old files. The skin or crust of a casting made in a sand mould is in general harder than that of a loam casting. This appears to occur from the former being partially chilled by the moisture of the sand. In some cases, as in the teeth of wheels, it is desirable to retain this hard sand coat on account of its greater durability ; but when the crust is partially removed from thin or slight works, it con¬ stantly happens that they spring or become distorted whilst under the treatment of tools, from the general balance of strength being disturbed by the partial removal of the crust. This gives rise to continual interferences, which come however under the considera¬ tion of the mechanician rather than of the founder. The crust of the casting, which always retains some sand, is very destructive to the tools, unless they can be sent in deep enough to penetrate to the clean metal beneath. When but little is to be removed from the casting, or that they are wrought with expensive tools and circular cutters, it is desirable to pickle the works, or to undermine the sand by dissolving a little of the metal with some acid. Iron castings are pickled with sulphuric acid diluted with about twice as much water. The castings, if small, are immersed in a trough lined with lead; or else the acid is sprinkled over them. In two or three days a thin crust, like an efflorescence, may be washed off with the aid of water and slight friction. Brass and gun-metal, when pickled, require nitric acid diluted with four to six times as much water, otherwise the rough coat should be removed with an old file or a triangular scraper, but which is less effective than the dilute acid. This acid liquor should be also kept in leaden vessels, or in those of well-glazed earthen¬ ware or glass. The yellow brass is much improved by a good but equal condensation with the hammer, and in fact to whatever action the metals are subjected, whether natural in the mould, or artificial under the hammer and tools, it is of primary importance that all parts should be treated as nearly alike as possible. New Method of Manufacturing Drop Shot.— David Smith, of the house of Le Roy and Co., 263 Water Street, New York, has invented and put into practice a new mode of manufacturing drop shot. The chief feature of this invention consists in causing the fused metal to fall through an ascending current of air, which shall travel at such a velocity that the dropping metal shall come in contact with more particles of air, in a short tower, than it would in falling through the highest towers before in use. Fig. 175 is a vertical sectional elevation of a sheet metal cylinder, set up as a tower within a building, and may be about 20 inches internal diameter, and 50 feet high or less. This tower, although mentioned in Smith’s patent, is now dispensed with in the middle CASTING- AND FOUNDING. 277 of the height, so that only an open space remains. Fig. 176 is a Fig. 175. plan at the line a b ; Fig. 177 is a plan at the line q r ; Fig. 178 ia a section at op ; and Fig. 179 is a section at m n, Fig. 175 Fig. 178. Fig. 179 C is a water-cistern beneath the tower. B is a pipe from the blowing apparatus leading into the annular chamber /; the upper surface g is perforated as shown in Fig. 177, to dispense the ascend* 278 THE PRACTICAL METAL-WORKER’S ASSISTANT. ing air. The outer side of this annular ring f forms the base of a frustum of a cone, forming the tower D, passing the blast through the frame y y, Fig. 178 ; and in Fig. 175 is shown to support a cylindrical standard R, the upper central portion of which receives the pouring pan A. This pan is charged with each separate size of shot. Round the pouring pan A is a circular waste trough z. The object of this arrangement is that the fluid metal running through the pouring pan A into the ascending current of air, will be operated upon in the same manner as if it fell through stagnant air of great height The shot falls through the open centre of the ring / into the water cistern C, where a shoot t carries it into the tub S, which when full may be removed through x, an aperture in the cover of the cistern. CHAPTER XYI. WORKS IN SHEET METAL, MADE BY JOINING. On Malleability, etc. ; Division of the Subject.— The process of casting, which has been recently considered under so great a variety of forms, is one of the most valuable courses of preparation to which the metallic materials are submitted. In the foundry, the metals are made to assume an infinitude of the most arbitrary shapes, but which are in general more or less thick or massive. It is now proposed to consider a few of the methods and principles of a very extensive and serviceable employment of the malleable metals and alloys, which (excepting iron) are cast into thick slabs or plates, and then laminated into thin sheets between cylindrical rollers. Rollers have been used for a considerable period in the manu¬ facture of sheets of malleable iron, steel, and copper, when in the red-hot state, but most others of the metals and alloys are rolled whilst cold; and which economic application of'power often nearly supersedes the use of the hammer, as it performs its function in a more uniform and gradual manner, and at the same time increases to the utmost the hardness, tenacity, elasticity and ductility of such of the metals and alloys as are submitted to this and similar courses of preparation for the arts. These processes of condensa¬ tion cannot be carried to the extreme without frequent recurrence at proper intervals to the process of annealing; and in rolling the thinnest sheets of metal, several are frequently sent through the rollers at the same time; but, as in the instances of tin-foil, gold and silver leaf, and some others, the hammer is again resorted to after the metals have been rolled as thin as they will economically admit of, in this process of part-manufacture. WORKS IN SHEET METAL. 279 "None of these preparations of the metals can go on without a material internal change of their substance, to which the celebrated Dr. Dalton thus refers: "Notwithstanding the hardness of solid bodies, or the difficulty of moving the particles one amongst the other, there are several that admit of such motion without fracture, by the application of proper force, especially if assisted by heat. The ductility and malleability of the metals need only be men¬ tioned. It should seem the particles glide along each other’s sur¬ face, somewhat like a piece of polished iron at the end of a magnet, without being at all weakened in their cohesion.” This gliding amongst the particles of metals is exemplified by the action of thinning them by blows of the hammer ; likewise by the actions of laminating rollers and the draw-bench, in which cases the external layers of the metals are retarded or kept back as it were in a wave, whilst the central stream or substance con¬ tinues its course at a somewhat quicker rate. The necessity for annealing occurs when the compression and sliding have arrived at the limit of cohesion. Beyond this the parts would tear asun¬ der, and produce such of the internal cracks and seams, met with in sheet-metal and wire, as are not due to original flaws and air- bubbles, which have become proportionally elongated in the course of the manufacture of these materials. A sliding or gliding of a very similar nature occurs also in every case in which the metals are bent; and this differs only in degree, whether we consider it in reference to a massive beam, a permanently flexible spring, a piece of thin sheet-metal, or a film of gold leaf. For instance, the curvature of a cast-iron beam, originally straight, is produced by the stretching or extension of the lower edge, and the shortening or compression of the uppei edge, the central line remaining unaltered during the process, ex¬ cept it is bent. In like manner a spring derives its elasticity from the extension and compression of its opposite surfaces at every flexure; and the spring remains permanent, or endures its work without alteration of form, when the bending is not carried beyond its limit of elasticity ; but when it is bent beyond a certain point, the spring either retains a permanent set or distortion, or it will break. In the same manner the beam, when only bent to the limit of its elasticity, returns to its original form when the load is re¬ lieved, and the constant study of the engineer is so to proportion the beam that it may never be required to exceed nor even to arrive at the limit of its elastic force. For those parts of mechan¬ ism exposed to sudden shocks and strains, he will employ wrought-iron, the cohesive strength of which is considerably greater than that of cast-iron, although less than that of steel, which is the strongest and most permanently elastic of all metallic substances. The thin metals also possess some elasticity, but this dies away before they reach the tenuity of leaf gold, in which, however, the bending cannot be accomplished without a similar change in the 280 THE PRACTICAL METAL-WORKER’S ASSISTANT. arrangement of its opposite sides, although the difference is be¬ yond the reach of our physical senses. If we desire to wrap a piece of gold leaf around a cylinder of half an inch diameter, so small is the resistance that the least puff of breath suffices. A piece of thin tin-foil offers no more resist¬ ance than writing-paper. Thin latten-brass, or China tea-lead, is bent more easily than a card; brass and iron the thirtieth or forti¬ eth of an inch thick, could be readily bent with a wooden-mallet; but metal of one-eighth of an inch thick would call for smart blows of a hammer, and in iron and steel the further assistance of heat would be likewise required, because in the last case a very con¬ siderable amount of the sliding motion of the metal would be called into play. For example, the piece of metal | of an inch thick, was originally flat and of the same size on its opposite surfaces; whereas now, neglecting any alteration of thickness, the inner part would equal the circumference of a circle | an inch diameter, and the outer that of a circle of f inch diameter; or it would become 1J and inches long respectively on its opposite surfaces. To produce this change of dimensions would necessarily require far greater force than the bending of the gold leaf, the internal and external meas¬ ures of which, viewed as a cylinder, could be ascertained alone by calculation, and not by ordinary means. On the other hand, the sliding of the thick sheet of metal would be illustrated most dis¬ tinctly, if several pieces of writing-paper, equal to the original metal individually in surface and collectively in thickness, were wrapped around the same cylinder. The inner paper would ex¬ actly meet, the outer would present an open seam f inch wide. The metals possessed of the malleable property undergo a nearly equal change in their arrangement; but the uninalleable or brittle metals break. Several of the processes of working the sheet metals are closely analogous to those employed in forging ordinary works in iron and steel,—the difference being mainly such as arise from the thin and thick states of the respective materials, and their relative degrees of rigidity or resistance. The illustrations will be selected indis¬ criminately from various trades in which the sheet metals are em¬ ployed. It appears desirable, however, to separate the subject into two principal parts, namely, the formation of objects some lines of which are straight, and the formation of objects no lines of which are straight. The first division comprehends all objects with plane, cylindri¬ cal or conical surfaces, such as may be produced in pasteboard by cutting out the respective sides, either separately or in clusters, and combining them in part by bending, and in part by cement. Simi¬ lar works in metal are often produced by the precisely analogous means of cutting, bending, and uniting, and which call for increase of strength in the methods proportioned to the rigidity of the materials. WORKS IN' SHEET METAL. 281 The second division comprehends all objects with surfaces of double curvature, including spherical, elliptical, parabolical, and arbitrary surfaces, as in reflectors, vases, and a thousand other things, none of which forms can be produced in stiff' pasteboard, because this material is incapable of being extended or contracted in different parts in the manner of sheet metal. This is easily shown, by the following case, amongst others. Terrestrial globes are covered with thin 'paper, upon which the delineation of the surface of the earth has been printed: the paper may be cut into twelve gores, or fish-shaped pieces, all including thirty degrees from pole to pole. A globe is usually covered with 26 pieces of paper, namely, 2 pole papers, or circles including 80° around each pole; and 24 gores meeting at the equator. Sometimes the gores extend from the pole to the equator; every gore has then a narrow curved central notch extending 30° from the equator. But the same gores cut out of pasteboard could not be applied to the surface of a globe, as pasteboard does not admit of that degree of gradual extension and contraction, required for the production of spherical and similar raised forms, from pieces originally flat, but will become abruptly bent and torn in the attempt. On the contrary, a round disk of metal may be beaten into a hemisphere, or nearly into a sphere; but even thin paper is only possessed of this quality in a very limited degree, for the globe could not be smoothly covered with so few as two, three, or four pieces of the thinnest paper without its puckering up, showing that some parts of the material are in excess. The gliding property, or that of malleability and ductility, possessed by the metals, is indis¬ pensable to adapt the flat plate to the sphere, by stretching the central portion and gathering up the marginal part, an action that admits of some comparison to the extension or compression of the slides of a telescope, except that the metal becomes thicker or thinner instead of being duplicated on itself. Works in Sheet Metal, Made by Cutting, Bending, and Joining. —Every one in early life has made the first step towards the acquirement of the various arts of working in sheet metal, in the simple process of making a box or tray of card; namely, by doubling up the four margins in succession to an equal width, then cutting out the small squares from the angles,, and uniting the four sides of the box, either edge to edge, by paste, sealing-wax, or thread, or in similar manners by lapped or folded joints. A dif¬ ferent mode is to make the sides of the box as a long strip, folded at all the angles but one; or lastly, the bottom and sides may be cut out entirely detached, and united in various ways. In the above, and also in the most complicated vessels and solids, it is necessary to depict on the material the exact shape of every plane superficies of the work, as in the plans and elevations of the architect; and these may be arranged in any clusters which admit of being folded together, so as to constitute part of the joints by bending the material. Thus, a hexagonal box, Fig. 180, can be 282 THE PRACTICAL METAL-WORKER’S ASSISTANT. made by drawing first tbe hexagon required for the bottom, as in Fig. 181, and erecting upon every side of the same a parallelogram equal to one of the sides, which in this case are all exactly alike; otherwise the group of sides can be drawn in a line, as in Fig. 182, and bent upon the joints to the required angle, or 120 degrees. Either mode would be less troublesome than cutting out seven detached pieces and uniting them; the addition of one more hexa¬ gon, dotted in Fig. 182, would serve to complete the top of the hexagonal prism, by adding a cover or top surface. The same mode will apply to polygonal figures of all kinds, regular or irregular; thus Fig. 183 would be produced when the group of sides in 184 were bent around the irregular octagonal base; or that the sides of 185 were separately turned up Figs. 180 181 182 The cylinder is sometimes compared with a prism of so many sides, that they melt into each other and become a continuous curve; and if the hexagon in Fig. 182 were replaced by a circle, and the group of sides were cut out of equal length with the cir¬ cumference of that circle, and in width equal to the height of the vessel, any required cylinder could be produced. And in like manner any vessel of elliptical or similar forms, or those with par¬ allel sides and curved ends, and all such combinations, could be made in the manner of Fig. 184 (provided the sides were perpen¬ dicular} by cutting out a band equal in length to the collective margin of the figure, as measured by passing a string around it; or the sides might be made of two, or several pieces, if more con¬ venient, or if requisite from their magnitude. All prismatic vessels require parallelograms to be erected on their respective bases; but pyramids require triangles, and frustums of pyramids require trapezoids, as will be explained by Figs. 187 WORKS IN SHEET METAL. 283 and 188, which are the forms in which a single piece of metal must be cut, if required to produce Fig. 186. Every one of the group of sides, must be individually equal to one of the sides of the pyramid, whether it be regular or irregular, and 186 being an erect and equilateral figure, all the sides in 187 and 188 are required to be alike, and would be drawn from one templet: an irregular pyramid would require all its superficies to be drawn to their absolute forms and sizes. Figs. 186 187 188 The cone is sometimes compared with a pyramid with exceed¬ ingly numerous sides (as the cylinder is compared with the prism), and Fig. 189, intended to make a funnel or the frustum of a cone of the same proportions as 186, illustrates this case. The sides of the cone are extended until they meet in the centre o, Fig. 186, and then with the slant distances o a, and o b, the two arcs a a, and b b, are drawn with the compasses, from the centre o ; and so much of the arc a a, is required as equals the circumference a, of the cone: the margins a b, a b, are drawn as two radii. When the figure is curled up until the radial sides meet, it will exactly equal the cone, and the similitude between Figs. 188 and 189 is most explanatory, as 189 is just equal to the collective group of the sides required to form the pyramid. It will now be easily seen that mixed polygonal figures, such as Figs. 190, 192, and 194, may be produced in a similar manner, provided their sides are radiated from the square, the hexagonal or other bases, in the manner of Figs. 191, 193, 195, but the sides of the rays not being straight, it is no longer possible to group them by their edges, as in Figs. 182, 184, and 188. The object with plane surfaces, Fig. 190, is only the meeting of two pyramids, at the ends of a prism, and when unfolded, as in Fig. 191, the centre is equal to the base a, of the object; the sides b, radiate and ex- 284 THE PRACTICAL METAL-WORKER’S ASSISTANT. pand from the hexagon at the angle of the faces of the inverted or lower pyramid b, and their vertical height in the sheet is equal to the slant height in the vessel; the superficies c, are those of a prism, therefore they continue parallel, and have the vertical height of the part c, of the figure; lastly, the sides d, again contract as in the original, and at the same angle as the sides of the six upper faces; in a word, the faces b, c, d, are identical in the vase and in the radi¬ ated scheme. Figs. 190 192 194 Should the vessels, instead of planes, have surfaces of singk cur¬ vature, as in Figs. 192 and 194, the method is nearly as simple. The object is drawn on paper, and around its margin are marked several distances, either equal or unequal, and horizontal lines or ordinates are drawn from all to the central line. The radiating pieces for constructing the polygonal vases are represented in Figs. 193 and 195, in which the dotted lines are parallel with the sides of the hexagons or the bases, and at a distance equal to those of the steps 1, 2, 3, to 8, around the curve of the intended vases; the lengths of these lines, or ordinates, 1 1, 2 2, 3 3, are in regular hexagonal vessels exactly the same in the radiated plans as in the respective elevations, because the side of the hexagon and the radius of its circumscribing circle are alike. In all other regular polygonal vessels the new ordinates will be reduced for figures of 8, 10, and 12 sides, in the same proportions as the sides of these respective polygons bear to the radii of their circumscribing circles, and the prdinates for 3, 4, and 5 sided figures will be similarly increased. All the above cases could be accurately provided for without any calculation, by the employment of a very simple scale repre- WORKS IN SHEET METAL. 285 sented in Fig. 196, in which the angle 3 of shall contain 120 de¬ grees, or the third of a circle; 4 o /, 90 degrees, or the fourth; 5 of 72, or the fifth; 6 of 60, or the sixth; and 8, 10, and 12, re¬ spectively the 8th, 10th, and 12th parts of a circle. The circular arcs are struck from the centre o, and may be the 6th, 8th, 10th of an inch, or any small distance apart. To learn the altered value of any ordinate, as for constructing a vase like the several figures 190, 192, 194, but with 10 sides; we will suppose the original ordinate to reach from o to x on the radius o f the required measure would be the length of the arc x x , where intersected by the line 10, or that for a decagon; but it would be more convenient to make the angle half the size, as then the new ordinate would be at once bisected, ready for being set off on each side the central line of the radiated plan. When one side had been carefully formed, a curved templet or gage would be made to the shape, by which all the other sides could be drawn. For polygonal vessels with unequal sides, such as Fig. 197, the curvatures of the edges of the rays will be identical, notwithstand¬ ing the difference of the sides. For example, the octagon drawn in the one corner shows that the figure resembles the regular octa¬ gon as far as the angles are considered; and that the regular octagon may be considered to be cut into four quarters and to be removed to the four corners, by the insertion of the two pairs of intermediate pieces a a, and b b, which latter would necessarily be parallel. In the like manner a pyramidal vessel built upon the same base, would require equal angles for all its sides. It would have been easy to have extended these particulars to numerous other figures, such as the regular geometrical solids, oblique solids, and many others, but enough has been advanced to explain the cases of ordinary occurrence, and in the delineations of which, the tinman, coppersmith, and others are very expert. \J Much of that which has been stated, as it will eventually appear, has been partly advanced in elucidation, on the less apparent methods practised in making similar forms out of flat plates, by the process called raising ; this is done with the hammer alone, by stretching some parts of the metal and contracting others (the 286 THE PRACTICAL METAL-WORKERS ASSISTANT. drawing and upsetting of the blacksmith), a process not required iD any of the foregoing figures, the whole of which might be made in pasteboard, a material that, as before observed, does not admit of being raised or bulged into figures of double curvature. The various works having been drawn upon the sheet of metal, the first process is to cut them out; this is almost always done with the shears; sometimes, however, for thick metal, the cold- chisel and hammer are used, the work being laid upon the bare anvil or upon a cutting-plate, as in forging; occasionally the metal is fixed in the jaws of the tail-vice, and cut off with the cold-chisel applied in contact with the vice; the edge of the chisel is placed nearly parallel with the jaws, which serve as a guide. In some cases very long vices, with a screw at each end, are used in a simi¬ lar manner, for the thick iron plates employed for boilers ; but the shears are the most generally convenient. Although the tools used in working the sheet-metals are ex¬ tremely various as regards their sizes and specific forms, they may, with the exception of the shears and soldering-tools, be principally resolved into numerous varieties of hammers, anvils, swage-tools, and punches. Figs. 198 to 212 represent some few of the most common of these tools, which are used alike both in bent and raised works, and their close resemblance to those for ordinary forging in iron and steel will not escape observation. The most remarkable points of difference are in their greater height and length, which enable them to be applied to the interior of large WORKS IN SHEET METAL. 287 objects, and also in tbeir square shanks, by which they are fixed in holes in the wooden blocks and benches. The hammers are nearly alike at both ends; many of them have circular faces, either flat or convex ; others resemble the straight or cross-panes of ordinary hammers, and are also either flat or convex; and those used in finishing, are exceedingly bright, in order that they may impart their own degree of polish to the work, which process is called ’planishing . When thin metal is struck between tools both of which are of metal, it is invariably more or less thinned; and should the blows be given partially, such parts will become stretched or cockled, and will distort the general figure. It is therefore usual, whenever admissible, to employ wooden hammers of the forms described, and also wooden blocks or anvils when metal hammers are used ; reserving the employment of tools both of metal, either for the con¬ cluding steps, or for those cases, where from the substance of the metal and the nature of the work, the wooden hammers would be ineffective, or a greater definition of form is required than wooden tools could give. The anvil used by the coppersmith and similar workmen is usually square, say from six to eight inches on every side; and the smaller anvils, which are called stakes, and also teests, are of pro¬ gressively smaller sizes, down to half an inch square, and even less. Some of them have one edge rounded like 201 ; others have rounded faces as 202 and 203 ; a few assume the form of a rounded ridge, like Fig. 205 ; and many have bulbs or buttons, as if turned in the lathe, as in Fig. 206. The beak-irons are also very unlike those used by the smith; they are seldom attached to the anvil, and are often exceedingly long, as in Fig. 199: some few, for more accurate purposes, are turned in the lathe to the conical form, like 204; these are held in the vice, the jaws of which enter grooves in the shank; and man¬ drels four to six feet long, used for making long pipes, are attached to the bench by long rectangular shanks and staples. Fig. 198, the hatchet-stake, is from two to ten inches wide; it is very much used for bending the thin metals, in the same manner as the rectangular edge of the anvil is used for those which are thicker ; a cold-chisel fixed in the vice forms a small hatchet-stake; 207 is the creasing-tool for making small beads and tubes ; 208 is the seam-set for closing the seams prepared on the hatchet-stake ; 209 is a hollow and 210 a solid punch; the cutting edge of the former meets at about the angle of fifty degrees, the latter is solid at the end for small holes; both are struck upon a thin plate of lead or solder laid upon the stake; 211 is a riveting-set or punch for the heads of rivets ; and 212 is the swage-tool, a miniature of the tilt-hammer, to which a great variety of top and bottom tools, or creases, are added, which greatly economize the labor of making different mouldings and bosses; the stop is used to retain the par¬ allelism of the mouldings with the edge of the metal, and a similar stop is also at times applied to the hatchet-stake, 198. 288 THE PRACTICAL METAL-WORKER’S ASSISTANT. The sides of the vessels represented in Figs. 180 to 195, if the metal were thin, would be bent to the required angles by laying the metal horizontally upon the hatchet-stake, with the lines ex¬ actly over the edge of the same, and blows would be given with the mallet, (or with the hammer for more accurate angles), so as to indent the metal with the edge of the stake; it would be then bent down with the fingers, unless the edge were very narrow as for a seam, when the mallet would be alone used. Thicker metal is more commonly bent over the square edge of the anvil, as in Fig. 59, p. 104, a square set or hammer being held upon its upper sur¬ face; and sometimes the work is pinched fast in the vice, and it is bent over with the blows of a flat-ended punch or set, applied close in the angles, and then hammered down square with the hammer ; very strong metal is seldom bent in this manner, but the sides of objects are then made separately, and united in some of the ways which will be explained. In bending thin metals either to circular or other curves, they are held on the one edge in the hand, and curled on the opposite edge over beak-irons or triblets with the mallet; when the metal is too stubborn or too narrow to be thus held in the hand (as the copper-smith scarcely ever uses tongs, except at the fire), the metal is driven into a concave tool to curl up the edges. For instance, the crease, Fig. 207, is frequently employed for making small tubes or edging; the strip of metal is laid over the appropriate groove, and an iron wire is driven down upon it with the mallet; this bends it like a wagon-tilt; the edges are then folded down upon the wfire with the mallet, and it is finished by a top tool, or a punch, Fig. 208, having a groove of similar concavity or radius to that in the crease. For half-round strips, the crease together with the round wire suffice, or they would be more quickly made in the swage-tool, 212, and which might in this manner be made to produce any par¬ ticular section or moulding, and that at any distance from the edge by means of the stop or gage. Large tubes are always finished upon beak-irons, such as Fig. 199, the round ends of which serve for curvilinear, and the square ends for rectilinear works. Figs. 213 214. b b All the sheet metals up to the thickest boiler plate are treated much after the same general methods; large cast-iron moulds of WORKS IN SHEET METAL. 289 various sweeps are employed, the stout iron being heated to red¬ ness, and set into them with set hammers struck with the sledge. When a circular bend is wanted in the centre of a long piece, it is conveniently and accurately done by bending it over a ridge, such as a parallel plate with a rounded edge, or a triblet, the ends of the work serving for a purchase, or as levers. Thus Fig. 213 shows the common mode of bending thick plates to the form of the piece, a b, c', for the internal flues of marine boilers; the plate; is heated to redness in the middle, and pressed down until a c assume the positions a c'. In a similar manner, to bend long strips into easy curves, such as for cylindrical vessels, the tinmen use a former , Fig. 214, a cylin¬ drical piece of wood from two to four inches in diameter, and two feet long, turned with a pivot at the one end; the pivot is laid upon the edge of the bench, and the man rests his chest against the other extremity of Fig. 214, to support it in the horizontal position. The tin plate is first stretched in the hands by the two corners, a, c, and rubbed over the former diagonally, to bend it at every part; this is repeated across the other diagonal to flatten the plate; it is afterwards folded round the stick, and rubbed forcibly down with the hand, as at d, to give it an easy bend approaching to the required curvature. Should the vessel require a bed at the upper edge, it is usually made by the swage tool, Fig. 212, before the plate is curled up; the work is then much more rigid, and requires additional force to bend it. Figs. 215 216. 9 l Fig. 215 is intended to explain a very simple and useful machine, first employed by the tinmen for rolling up the cylinders for spring window-blinds, the sides of culinary vessels and similar works, and now also by the boiler-makers, and others for the strongest plates It has two cylindrical rollers, a, b, and d, which are connected by toothed wheels so as to travel in opposite directions, thus far ex¬ actly the same as a pair of laminating rollers for making the sheet metals; the third roller c, is just opposite the two, and is free to move on its pivots, as it is unconnected with a, b, and d ; and the third roller c, is capable of vertical adjustment. 19 290 THE PRACTICAL METAL-WORKERS ASSISTANT. When, therefore, the metal is moved along by the carrying rollers a b, and d, it strikes against the edge of the bending roller c, and is curled up to enable it to pass over the same; and as this bending occurs in an equal degree at every point of the sheet of metal, it assumes a circular sweep, the radius of which is depen¬ dent on the place of c. In the central position, the sheet would assume the circle e,f g\ and when c is more raised as to the upper position, the metal would follow the dotted circle, the radius of which is much less; and when the bending roller c, is placed out of level, the works are thrown into the conical form. Fig. 216 shows the application of the bending rollers to boiler plates; none of the rollers a, b, c, touch each other, and b is under adjustment for different curvatures. In the last four figures the same principle is employed, namely, the application of three forces as in a lever of the first order, or as in bending or breaking a stick across the knee. The school-boy’s problem of “drawing a circle through three given points” is thoroughly exemplified in Fig. 216 and in 215, the one force is the grip of the plate on the line of centres of a, b, d\ the roller c, curls the plate partly around the roller a, and the point at which the plate leaves a b, may be called the second force, or b ; the third is the point of contact on c. One of the most useful applications of the bending machines, is in straightening the metals, which may at first appear to be a mis¬ application of words, but in truth by the depression of c, to about the position of c', it only bends the plate for the moment, just to the limit of its elasticity. It results that when it has been passed through twice, or with each side alternately upwards, the elastic reaction just suffices to convert the figure temporarily given, or that of the arc of an enormous circle, into a plane or true surface; and as this is done without any blows, which produce partial con densation at such spots, the plate is less subject to after changes than if it had been hammered flat; as by the rollers, every part of the plate is bent exactly to the limit of its permanent elasticity. In the tinmen’s bending rollers, d, c, Fig. 215, are often turned with half round grooves, to receive the thickened edge which contains the wire employed to stiffen the tops of the vessels; sometimes also the rollers are used for preparing the seam to contain the wire. Grooved-rollers (similar to those shown on page 81) are very extensively employed, likewise, in other works in the arts be¬ sides the manufacture of iron, to which they are there more imme¬ diately referred. The use of the plain cylindrical roller at h, page 81, is so simple as to be immediately apparent; rollers with curvilinear edges, such as at i, have been long employed for bending the steel and brass plates for fenders; similar rollers on a smaller scale and of numer¬ ous patterns, many of them chased and ornamented, are used in making jewelry, as for producing mouldings, headings, and matted, checkered or other works WORKS IN SHEET METAL. 291 Improved Machine for Rolling up Sheet Metal Pipe.—• This Machine is the invention of Mr. William Ostrander, of New York, and is patented by Ostrander and Webster. It consists of three rollers, LMB (the same as ordinary stovepipe rollers); J is an independent pinion which mashes in the smaller ones fastened to the rollers, L and M, which gives them both the same line of motion; the roller, B, is raised or lowered by the treadle, G, in connection with F F, upon which rest the boxes of B. D D are set screws to adjust the height and pressure of B; I is a set screw, Fig. 217. which raises or lowers M, which regulates the space between L, M, and B. K is a mandril constructed of wood, upon which the pipe is formed; it is covered with the same material that is desired to be rolled or formed up by the machine, the seam or joint left un¬ soldered, in which the sheet C is placed, and there held while being formed between the three rollers. E is the pulley and belt; A is the bench; H is the weight which is used only when the machine is worked by a crank. The operation by steam is as follows: the 292 THE PRACTICAL METAL-WORKER’S ASSISTANT. rollers, L and M, are in constant motion, the mandril, K, is taken out from the three rollers, and the edge of the sheet, C, to be formed, is slipped between the mandril and its covering; it is then laid in the space it occupies as represented in the engraving; the foot is applied to G, which raises the roller, B, until the mandril, K, is brought in contact with L and M; the three rollers, together with the mandril, are revolved, and the sheet C, is drawn in and formed closely about the mandril; the foot is then removed from G, which allows the roller, B, to drop down, and permits the man¬ dril, K, to be taken out and the newly-formed pipe to be slipped off, whose edge, in nearly every instance, will be “laid” close enough for soldering: should the metal be so stiff and hard as to prevent its edge being laid in the first rolling, it will be perfectly so when rolled a second time on the bare wooden mandril. This roller is capable of forming from three to five thousand feet of pipe per 10 hours, in 20 inch joints, by a boy. It does not require the use of mallets to lay the edges. .It can be made as long as any sheet of metal requires, inasmuch as the rollers can be braced from the outside without being interfered with. It can be used in the old way for stovepipe, etc., by removing the pinion, J, up out of the way, and bringing the rollers, L M, close together. This machine is now in practical use by Woolcock and Ostran¬ der, No. 57 Ann Street, N. Y. ; who make large quantities of speak¬ ing and other pipes with it. Angle and Surface Joints. —The next steps to be considered, appear to be the methods of uniting the edges of the vessels after they have been cut and bent to meet in angles, curves, or plane surfaces. The principal modes of accomplishing this are repre¬ sented in Figs. 218 to 240, which are grouped together for the convenience of comparison. Figs. 218 and 219 are for the thinnest metals, such as tin, which require a film of soft-solder on one or other side. Sheet-lead is similarly joined, and both are usually soldered from within. Figs. 218 219 220 221 222 223 224 225 226 227 228 229. Figs. 220 and 221 are the mitre and Jw^-joints used for thicker metals with hard solders. Sometimes 221 is dovetailed together, the edges being filled to correspond coarsely ; they are also partly riveted before being soldered from within. These joints are very weak when united with soft solder. Fig. 222 is the lap- joint; the metal is creased over the hatchet WORKS IN SHEET METAL. 293 stake. Tin-plate requires an external layer of solder; spelter solder runs through the crevice, and need not project. Fig. 223 is folded by means of the hatchet-stake, the two are then hammered together, but require a film of solder to prevent them from sliding asunder. Fig. 224 is the folded angle-joint, used for fire-proof deed boxes, and other strong works in which solder would be inadmissible. It is common in tin and copper works, but less so in iron and zinc, which do not bend so readily. Fig. 225 is a riveted joint, which is very commonly used in strong iron plate and copper works, as in boilers, etc.; generally a rivet is inserted at each end, then the other holes are punched through the two thicknesses with the punch 210, on a block of lead. The head of the rivet is put within, the metal is flattened around it, by placing the small hole of the riveting set 211 over the pin of the rivet, and giving a blow; the rivet is then clinched, and it is finished to a circular form by the concave hollow in another riveting set. When the works cannot be laid upon an anvil or stake, a heavy hammer is held against the head of the rivet to receive the blow; in larger works the holes are all punched before riveting, and the heads are left from the hammer. Figs. 226 and 227 ; the plates a a, are punched with long mor¬ tises, then b b, are formed into tenons, which are inserted and riveted; but in 227 the tenons have transverse keys to enable the parts to be separated. Fig. 228, the one plate makes a butt-joint with the other, and is fixed by L formed rivets or screw-bolts s ; the short ends are generally riveted to the one plate, even when screwed nuts are used. This mode is very common for cast-iron plates, as in stove work. Fig. 229 is the mode universally adopted for very strong ves¬ sels, as for steam-boilers, in which the detached wrought-iron plates are connected by angle-iron, rolled expressly for the pur¬ pose, (see f Fig. 27, p. 81). The rivet holes are punched in all the four edges, by powerful punching engines furnished with travel¬ ing stages and racks, which insure the holes being in line, and equidistant, so that the several parts when brought together may exactly correspond. The rivet r, which may be compared to a short stout nail is made red-hot, and handed by a boy to the man within the boiler, who drives it in the hole; he then holds a heavy hammer against its head, whilst two men quickly clench or burr it up from without: between the hammering, and the contracting of the metal in cooling, the edges are brought together into most intimate and powerful contact. Bolts and nuts b, may be used to allow the removal of any part, as the man-hole of the boiler. For the curved parts of the boilers, the angle iron is bent into corresponding sweeps, and for the corners of square boilers, the angle iron is welded together to form the three tails for the re¬ spective angles or edges which constitute the solid corner: this when well done, is no mean specimen of welding. 294 THE PRACTICAL METAL-WORKER’S ASSISTANT. Tt frequently happens that several plates are required to be joined together to extend their dimensions, or that the edges of one plate are united as in forming a tube ; these joints are arranged in the figures 230 to 240, similarly to those for angles previously shown, from which they differ in several respects. Fig. 230 is the Zap-joint, employed with solder .for tin plates, sheet lead, etc., and for tubes bent up in these materials. Fig. 231, the ZmZZ-joint, is used for plates and small tubes of the various metals; united with the hard solders they are moderately strong, but with tin solder the junctions are very weak from the limited measures of the surfaces. Fig. 232 is the cramp-joint: the edges are thinned with the hammer, the one is left plain, the other is notched obliquely with shears, from one-eighth to three- eighths of an inch deep; each alternate cramp is bent up, the others down for the insertion of the plain edge; they are next hammered together and brazed, after which they may be made nearly flat by the hammer, and quite so by the file. The cramp-joint is used for thin works requiring strength , and amongst numerous others for the parts of musical instruments. Sometimes also 230 is fea¬ ther-edged; this improves it, but it is still inferior to the cramp-joint Figs. 230 231 232 233 234 235 TT \ / Ml 236 m 237 238 239 C 240 V7T-IW 1] strength. Fig. 233 is the lap-joint without sold- “ er, for tin, copper, iron, etc.; it is set ^ down flat with a seam-set, Fig. 209, and used for smoke-pipes, and numerous □ works not required to be steam or water¬ tight. _! Fig. 234 is used for zinc works and others; it saves the double bend of 233. Fig. 235 is the roll-joint employed for lead roofs, the metal is folded over a wooden rib, and requires no solder; the water will not pass through this joint until it exceeds the elevation of the wood. The roll- joint is less bent when used for zinc, as that material is rather brittle ; the laps merely extend up the straight sides of the wooden roll, and their edges are covered by a half-round strip of zinc nailed to the wood. Fig. 236 is a hollow crease used for vessels and chambers for making sulphuric acid ; the metal is scraped perfectly clean, filled with lead heated nearly to redness, and the whole are united by burning, with an iron heated also to redness. Solder which con¬ tains tin would be acted upon by the acid, whereas until the acid WORKS IN SHEET METAL. 295 is very concentrated, the lead is not injured; this method is how¬ ever now superseded by the mode of autogenous soldering. The concentration of sulphuric acid and some other chemical prepara¬ tions, is performed in vessels made of platinum. Figs. 237 and 238 are very commonly employed either with rivets or screw-bolts; the latter joint is common in boilers, both of copper and iron, and also in tubes; copper works are frequently tinned all over the rivets and joints, to stop any minute fissures. Fig. 237 is the flange-joint for pipes. Fig. 239, with rivets, is the common mode of uniting plates of marine boilers, and other works required to be flush externally. Fig. 240 is a similar mode, used of late years for constructing the largest iron steam-ships; the ribs of the vessels are made of T iron, varying from about four to eight inches wide, which is bent to the curve by the employment of very large surface-plates cast full of holes, upon which the wood model of the rib is laid down, and a chalk mark is made around its edge. Dogs or pins are wedged at short intervals in all those holes which intersect the curve; the rib, heated to redness in a reverberatory furnace, is wedged fast at one end, and bent round the pins by sets and sledge-hammers, and as it grows or yields to the curve, every part is secured by wedges until the whole is completed. The following method of constructing metallic boats, invented by Mr. Francis, of the Novelty Works, New York, is taken from Har¬ per’s New Monthly Magazine. In many cases of distress and disaster befalling ships on the coast, it is not necessary to use the car, the state of the sea being such that it is possible to go out in a boat, to furnish the necessary succor. The boats, however, which are destined to this service must be of a peculiar construction, for no ordinary boat can live a moment in the surf which rolls in, in storms, upon shelving or rocky shores. A great many different modes have been adopted for the construction of surf-boats, each liable to its own peculiar objections. The principle on which Mr. Francis relies in his life and surf-boats, is to give them an extreme lightness and buoyancy, so as to keep them always upon the top of the sea. Formerly it was expected that a boat in such a service, must necessarily take in great quantities of water, and the object of all the contrivances for securing its safety, was to expel the water after it was admitted. In the plan now adopted the design is to exclude the water alto¬ gether, by making the structure so light and forming it on such a model that it shall always rise above the wave, and thus glide safely over it. This result is obtained partly by means of the model of the boat, and partly by the lightness of the material of which it is composed. The reader may perhaps be surprised to hear, after this, that the material is iron. Iron—or copper, which in this respect possesses the same proper¬ ties as iron—though absolutely heavier than wood, is, in fact, much lighter as a material for the construction of receptacles of all kinds. 296 THE PRACTICAL METAL-WORKER’S ASSISTANT. on account of its great strength and tenacity, which allows of its being used in plates so thin that the quantity of the material em¬ ployed is diminished much more than- the specific gravity is in¬ creased by using the metal. There has been, however, hitherto a great practical difficulty in the way of using iron for such a pur¬ pose, namely, that of giving to these metal plates a sufficient stiff¬ ness. A sheet of tin, for example, though stronger than a board, that is, requiring a greater force to break or rupture it, is still very flexible, while the board is stiff. In other words, in the case of a thin plate of metal, the parts yield readily to any slight force, so far as to bend under the pressure, but it requires a very great force to separate them entirely; whereas in the case of wood, the slight force is at first resisted, but on a moderate increase of it, the structure breaks down altogether. The great thing to be desired therefore, in a material for the construction of boats, is to secure the stiffness of wood in conjunction with the thinness and tenacity of iron. This object is attained in the manufacture of Mr. Francis’s boats by plaiting or corrugating the sheets of metal of which the sides of the boat are to be made. A familiar illustration of the principle on which this stiffening is effected is furnished by the common table waiter, which is made usually, of a thin plate of tinned iron, stiffened by being turned up at the edges all around—the upturned part serving also at the same time the purpose of forming a margin. The platings or corrugations of the metal in these iron boats pass along the sheets, in lines, instead of being, as in the case of the waiter, confined to the margin. The idea of thus corrugating or Fig. 241. WORKS IN SHEET METAL. 297 plaiting the metal was a very simple one; the main difficulty in the invention came, after getting the idea, in devising the ways and means by which such a corrugation could be made. It is a curious circumstance in the history of modern inventions that it often requires much more ingenuity and effort to contrive a way to make the article when invented, than it did to invent the article itself. It was, for instance, much easier, doubtless, to invent pins, than to invent the machinery for making pins. The machine for making the corrugations in the sides of these metallic boats consists of a hydraulic press and a set of enormous dies. These dies are grooved to fit each other, and shut together; and the plate of iron which is to be corrugated being placed be¬ tween them, is pressed into the requisite form, with all the force of the hydraulic piston—the greatest force, altogether, that is ever employed in the service of man. The machinery referred to will be easily understood by the above engraving. On the left are the pumps, worked, as represented in the engraving, by two men, though four or more are often required. By alternately raising and depressing the break or handle, they work two small but very solid pistons which play within cylinders of corresponding bore, in the manner of any common forcing-pump. By means of these pistons the water is driven in small quantities, but with prodigious force, along through the horizontal tube seen passing across, in the middle of the picture, from the forcing-pump to the great cylinders on the right hand. Here the water presses upward upon the under surface of pistons working within the great cylinders, with a force proportional to the ratio of those pistons compared with that of one of the pistons in the pump. Now the piston in the force-pump is about one inch in diameter. Those in the great cylinders are about twelve inches in diameter, and as there are four of the great cylinders the ratio is as 1 to 576. Areas being as the squares of homologous lines, the ratio would be, mathe¬ matically expressed, l 2 : 4x 12 2 =1 : 4x 144=1 : 576. This is a great multiplication, and it is found that the force which the men can exert upon the piston within the small cylinder, by the aid of the long lever with which they work it, is so great, that when multi¬ plied by 576, as it is by being expanded over the surface of the large pistons, an upward pressure results of about eight hundred tons. This is a force ten times as great in intensity as that exerted by steam in the most powerful sea-going engines. It would be sufficient to lift a block of granite five or six feet square at the base, and as high as the Bunker Hill Monument. Superior, however, as this force is, in one point of view, to that of steam, it is very inferior to it in other respects. It is great, so to speak, in intensity, but it is very small in extent and amount. It is capable indeed of lifting a very great weight, but it can raise it only an exceedingly little way. Were the force of such an engine to be brought into action beneath such a block of granite as we have described, the enormous burden would rise, but it would rise 298 THE PRACTICAL METAL-WORKER’S ASSISTANT. by a motion almost inconceivably slow, and after going up perhaps as high as the thickness of a sheet of paper, the force would be spent, and no further effect would be produced without a new ex¬ ertion of the motive power. In other words, the whole amount of the force of a hydraulic engine, vastly concentrated as it is, and irresistible, within the narrow limits within which it works, is but the force of four or five men after all; while the power of the engines of a Collins’ steamer is equal to that of four or five thousand men. The steam-engine can do an abundance of great work ; while, on the other hand, what the hydraulic press can do is very little in amount, and only great in view of its extremely concentrated intensity. Hydraulic presses, before the introduction of D. Dick’s anti-fric¬ tion press, were often used, in such cases and for such purposes as require a great force within very narrow limits. The indentations made by the type in printing the pages of Harper’s Magazine, are taken out, and the sheet rendered smooth again, by hydraulic presses exerting a force of twelve hundred tons. This would make it necessary for us to carry up our imaginary block of granite a hundred feet higher than the Bunker Hill Monument to get a load for them. There are nine of these presses in the printing-rooms of Harper and Brothers, all constantly employed in smoothing sheets of paper after the printing. The sheets of paper to be pressed are placed between sheets of very smooth and thin, but hard pasteboard, until a pile is made several feet high, and containing sometimes two thousand sheets of paper, and then the hydraulic pressure is applied. These presses cost, each, from twelve to fifteen hundred dollars. In Mr. Francis’s presses, the dies between which the sheet of iron or copper are pressed, are directly above the four cylinders which we have described, as will be seen by referring once more to the drawing. The upper die is fixed—being firmly attached to the top of the frame, and held securely down by the rows of iron pillars on the two sides, and by the massive iron caps, called platens, which may be seen passing across at the top, from pillar to pillar. These caps are held by large iron nuts which are screwed down over the ends of the pillars above. The lower die is movable. It is attached by massive iron work to the ends of the piston-rods, and of course it rises when the pistons are driven upward by the pressure of the water. The plate of metal, when the dies approach each other, is bent and drawn into the intended shape by the force of the pressure, receiving not only the corrugations which are designed to stiffen it, but also the general shaping necessary, in respect to swell and curvature, to give it the proper form for the side, or the portion of a side, of a boat. It is obviously necessary that the dies should fit each other in a very accurate manner, so as to compress the iron equally in every part. To make them fit thus exactly, massive as they are in mag¬ nitude. and irregular in form, is a work of immense labor. They WORKS IN SHEET METAL. 299 are first cast as nearly as possible to tlie form intended, but as sncli castings always warp more or less in cooling, there is a great deal of fitting afterwards required, to make them come rightly together. This could easily be done by machinery if the surfaces were square or cylindrical, or of any other mathematical form to which the working of machinery could be adapted. But the curved and winding surfaces which form the hull of a boat or vessel, smooth and flowing as they are, and controlled, too, by established and well-known laws, bid defiance to all the attempts of mere mechanical motion to follow them. The superfluous iron, therefore, of these dies, must all be cut away by chisels driven by a hammer held in the hand; and so great is the labor required to fit and smooth and polish them, that a pair of them costs several thousand dollars before they are completed and ready to fulfil their function. The superiority of metallic boats whether of copper or iron, made in the manner above described, over those of any other con¬ struction, is growing every year more and more apparent. They are more light and more easily managed, they require far less repair from year to year, and are very much longer lived. When iron is used for this purpose, a preparation is employed that is called galvanized iron. This manufacture consists of plates of iron of the requisite thickness, coated on each side, first with tin, and then with zinc; the tin being used simply as a solder, to unite the other metals. The plate presents, therefore, to the water, only a surface of zinc, which resists all action, so that the boats thus made are subject to no species of decay. They can be injured or de¬ stroyed only by violence, and even violence acts at a very great disadvantage in attacking them. The stroke of a shot, or a con¬ cussion of any kind that would split or shiver a wooden boat so as to damage it past repair, would only indent, or at most perforate, an iron one. And a perforation even, when made, is very easily repaired, even by the navigators themselves, under circumstances however unfavorable. With a smooth and heavy stone placed upon the outside for an anvil, and another used on the inside as a hammer, the protrusion is easily beaten down, the opening is closed, the continuity of surface is restored, and the damaged boat becomes, excepting, perhaps, in the imagination of the navigator, as good once more as ever. Metallic boats of this character were employed by the party under Lieut. Lynch, of the U. S. Navy, now a traitor to his country, in making their voyage to the Dead Sea. The navigation of the stream was difficult and perilous in the highest degree. The boats were subject to the'severest possible tests and trials. They were impelled against rocks, they were dragged over shoals, they were swept down cataracts and cascades. There was one wooden boat in the little squadron; but this was soon so strained and battered that it could no longer be kept afloat, and it was abandoned. The metallic boats, however, lived through the whole, and finally floated in peace on the heavy waters of the Dead Sea, in nearly as good a condition as when they first came from Mr. Francis’s dies. 800 THE PRACTICAL METAL-WORKER’S ASSISTANT. The seams of a metallio boat will never open by exposure to the sun and rain, when lying long upon the deck of a ship, or hauled up upon a shore. Nor will such boats burn. If a ship take fire at sea, the boats if of iron, can never be injured by the conflagation. Nor can they be sunk. For they are provided with air chambers in various parts, each separate from the others, so that if the boat were bruised and jammed by violent concussions, up to her utmost capacity of receiving injury, the shapeless mass would still float upon the sea, and hold up with unconquerable buoyancy as many as could cling to her. The principle on which these life-boats are made is found equally advantageous in its application to boats intended for other pur¬ poses. For a gentleman’s pleasure-grounds, for example, how great the convenience of having a boat which is always stanch and tight—which no exposure to the sun can make leaky, which no wet can rot, and no neglect impair. And so in all other cases where boats are required for situations or used where they will be exposed to hard usage of any kind, whether from natural causes or the neglect or inattention of those in charge of them, this ma¬ terial seems far superior to any other. CHAPTER XVII. WORKS IN SHEET METAL, MADE BY RAISING; AND THE FLATTENING OF THIN PLATES OF METAL. Circular Works Spun in the Lathe. —The former examples have only called into action so small an amount of the malleable or gliding property of the metals, that all the forms referred to could be produced in pasteboard, a material nearly incapable of extension or compression. The raised works now to be consid¬ ered, call for much of this gliding or malleable action which may be compared with the plastic nature of clay as an opposite extreme. Thus a lump of clay is thrown on the potter’s horizontal lathe, a touch of the fingers shapes it into a solid round lump, the potter thrusts his clenched hand into the Centre, and it raises in form something like a basin; by applying the other hand outside to prevent the material from spreading, it will rise as an irregular hollow cylinder, and a gentle pressure from without, and a sustain¬ ing pressure from within, will gather up or contract the clay into the narrow mouth suited to a bottle, and which is made somewhat in this manner almost by the fingers alone. A similar and parallel application, due to the malleability of the metals, and one which also requires the turning-lathe, is very ex- WORKS IN SHEET METAL. SOI tensively practised: namely, tlie art of “spinning or burnishing to form ” thin circular works in several of the ductile metals and alloys, as for teapots, plated candlesticks, the covers of cups and vessels, the bell mouths of musical instruments, and numerous other objects required in great numbers, and of thin metals. Plated candlesticks are thus formed of several parts soldered together, or retained in position by the fittings of their edges, the whole being strengthened by a central wire, and by filling the entire cavity with a resinous cement. The Figs. 242 and 243 are intended to show the mode of spinning the body of a Britannia metal teapot from one unperforated disk of metal. The wooden mould or chuck a, Fig. 242, is turned to the form of the lower part of the teapot, and a disk of metal b, is pinched tight between the flat surfaces of a and c, by the fixed centre screw d of the lathe, so that a, b, and c, revolve with the mandrel: and now by means of a burnisher e, which is rested against a pin in the lathe rest, as a fulcrum, and applied near the centre of the metal; and a wooden stick /, held on the opposite side to support the edge, the metal is rapidly bent or swaged through the successive forms 1, 2, 3, to 4, so as to fit close against the curved face of the block and to extend up its cylindrical edge. The mould a is next replaced by g, Fig. 243, a plain cylindrical block of the diameter of the intended aperture. One of various Figs. 242 243. forms of burnishers {h, i, some bent, others T form, and so on, the surfaces of which are slightly greased) are used, together with the hooked stick or rubbery first to force the metal inwards, as shown at 5, 6, 7, and also to curl up the hollow bead which stiffens the mouth of the finished vessel, 9. Sometimes the moulds are made of the entire form of the inside of the work, but of several pieces, each smaller than the mouth ; so that when the central block is first removed the others may be successively taken- out of the finished vessel, like the parts of a hat-block or of a boot-tree. It is of importance during the whole process to keep the edge 302 THE PRACTICAL METAL-WORKER’S ASSISTANT. exactly concentric ancl free from the slightest notches, for which purpose it is occasionally touched with the turning tool during the process of spinning. The operation is very pretty and expeditious, and resembles the manipulation of the potter who forms a bottle or vase with a close mouth in a manner completely analogous, although the yielding nature of his material requires the fingers alone, and neither the mould, stick, nor burnisher. The lenses of optical instruments are often fixed in their cells by simi¬ lar means; a, Fig. 244, shows in excess the form of the metal when turned, and b the thin edge when curled over the glass by means of a burnisher applied whilst the ring re¬ volves in the lathe. Much of the cheap Birmingham jewelry is also spun in the lathe, but in a different manner. For instance, to make such an object as the ring represented black in Fig. 245, a steel mandrel is turned upon a lathe to the same form as the ring, but less in diameter. The metal is prepared as a thin tube, it is soldered and cut into short pieces, each to serve for one ring, and these are spun into shape almost in an instant, between the arbor and the milling tool or roller, as seen in the front view, Fig. 246. It is clear that unless the arbor were smaller than the work, the latter from being Fig. 245 246. undercut could not be released. Sometimes only one broad mill¬ ing tool is employed, at other times two or more narrow ones. This process is most distinctly a modification of two rollers, which travel by surface-contact instead of by toothed wheels, and differs but little from the embossing or matting rollers employed by jewel¬ ers and others for long strips instead of rings. Extending the same application to the milling-tool upon a solid body, such as milled nut, the interior metal supplies the resistance given by the arbor, in the last figure. Works Raised by the Hammer. — In raising the metals by the hammer, we have to produce similar effects to those in the spinning process; not however by the gradual and continued pres¬ sure of a burnisher, on one circle at a time, but by circle* of blows , WOKKS IN SHEET METAL. 303 applied mucli in the same order, and as far as possible with the same regularity of effect. The art consists, therefore, of two principal points. First, so to proportion the original size and thickness of the metal disks that it shall exactly suffice for the production of the required object— neither with excess of metal, which would have to be cut off with shears and thrown aside, wasting a part both of the metal and labor, nor with deficiency of metal, which would be nearly a total loss. Secondly, that the work shall be produced with the smallest possible number of blows, which sometimes tend to thin, and at other times to thicken the metal; whereas the finished works should present a uniform thickness throughout, and which is, in many cases, j ust that of the original metal when in the sheet. For instance, a hollow ball six inches diameter is made of two circular pieces of copper, each seven and a half inches diameter. Now, calling the original circumference of the disk twenty-two and a half inches, this line eventually becomes contracted to eighteen inches, or the circumference of the ball,—although, at the same time, the original diameter of the disk, namely, a line of seven and a half inches, has become stretched to that of nine inches or the girth of the hemisphere. This double change of dimensions, accomplished by the mallea¬ bility or gliding of the metal, occurs in a still more striking man¬ ner in the illustration of spinning the tea-pot, in which the disk, originally about one foot diameter, becomes contracted to two or three inches only at the mouth. The precise nature of the change is seen on inspecting Figs. 190 and 192 in connection with the radiated pieces 191 and 193 required for the formation of such polygonal vases, when bent up and soldered at their edges. The same vases wrought to the circular figure from round plates, either by spinning or by the hammer, would not require disks of metal so large as the boundary circles in Figs. 191 and 193; as the pieces between the rays would be entirely in excess, they would cause the vessels to rise beyond their intended sizes, and would require to be pared off. But the original disks for making the vases should be of about the diameters of tho inner circles, as then the pieces d, beyond the inner circles, would - be nearly equal to the spaces e, within these circles, which would leave the vessel of uniform thickness throughout, and without deficiency or excess of metal, supposing the conversion to be performed with mathe¬ matical truth. The first and most important notion to be conveyed in reference to raising works with the hammer, is the difference between those which may be called opposed, or solid blows, that have the effect of stretching or thinning the metal; and those which may be called unopposed, or hollow blows, that have less effect in thinning than in bending the metal; in fact, it often becomes thickened by hollow blows, as will be shown. For example, the hammer in Fig. 247 is directly opposed to the 304 THE PRACTICAL METAL-WORKER’S ASSISTANT. face of the anvil, or meets it face to face, and would be said to give a solid blow; one which would not jar the hand grasping the plate, were the latter ever so thick or rigid: and this blow would thin the metal by its sudden compression between two hard sur¬ faces, the face of the hammer being represented at /. The hammer m Fig. 248 is not directly opposed to the anvil, or rather to that point of it which sustains the work, consequently this would be called a hollow blow, one which would jar the hand were the plate thick and rigid ; and it would bend the plate partly to the form of the supporting edge, by a similar exhibition of the forces a, b, c, referred to in the diagrams, Figs. 213 to 216; not, how¬ ever, by the quiet pressure therein employed, but by impact, or by driving blows. The hand situated at a, Fig. 248, would be insuffi¬ cient to withstand the blows of the hammer at c, but for the great distance of a b, compared with b c, and the thin flexible nature of the material. From these reasons the coppersmith and others never require tongs for holding the metal, the same as the blacksmith, except at the fire, as in annealing and soldering; in hammering thin works, a constant change of position is required, and which can be in no way so readily accomplished as by the exquisite mechanism given us by nature, the unassisted hand. When, however, the works are too rigid or too small to be thus held, the anvil is made to supply the two points a, c, as in Fig. 249, and the blow of the hammer is directed between them. We will now trace the effects of solid and hollovj blows given partially on a disk of metal a a, Fig. 250, supposed to be twelve inches diameter; first within a central circle c c, of three inches diameter; and then around the margin a b, to the width of three inches, leaving the other portions untouched in each case; the thickness of the metal is greatly exaggerated to facilitate the explanation. The solid blows within the circle c c, would thin and stretch that part of the metal, and make it of greater superficial extent; but the broad band of metal a c, would prevent it from expanding be- WORKS IN SHEET METAL. 305 yond its original diameter, and therefore the blows would make a central concavity, as in a cymbal, or like Fig. 251. And the more blows that were given, either inside the bulge upon a flat anvil, or outside the bulge upon an anvil or head of a globular form, the more would the metal be raised, from its being thinned and ex¬ tended ; and thus it might be thrown into the shape of a lofty cone or sugar-loaf. The hollow blows given within the same limited circle would also stretch the metal and drive it into the hollow tools employed, such as Fig. 249 ; thus producing the same effect as in 251, but by stretching the metal as we should the parchment of a drum, by the pressure of the hand in the centre, or by a blow of the drum-stick. The solid blows around the three-inch margin, would thin the metal and cause it to increase externally in diameter; but the plate would only continue flat, as in Fig. 252, if every part of the ring were stretched proportionally to its increased distance from its first position. Were the inner edge towards h, thinned beyond its due amount, its expansion, if resisted by the strength of the outer ring a, would throw part of the work into a curve, and depress the metal, not as in the cymbal, but in the form of a gutter as in Fig. 253; it would however more probably happen, that the inner edge alone of the marginal ring would be expanded, leaving the outer edge undisturbed, and producing the coned figure, 254. The hollow blows given around the edge, as in Fig. 248, would have the effect of curling up or raising the edge, first as a saucer 255, and then into a cylindrical form 256; provided that by the skilful management of the hammering, the metal could be made to slide upon itself without puckering, so as to contract the original boundary circle of the disk or twelve inches, into six inches, or the measure of the edge of the cylinder resulting from the drawing in of the three-inch margin. In this process the metal would become proportionally thickened at the upper edge, because each little piece of the great circle, Fig. 257, when compressed into a circle of half the diameter, would only occupy half its original length, as it could not be altogether lost; and the metal would therefore increase in thickness in a pro¬ portional degree. The remainder of the circle serves for the time as effectually to compress the metal in the direction of the tangent, as if the radii were the sides of an unyielding angular groove dotted in Fig. 257: this contraction produces in fact the same effect as the jumping or upsetting by endlong blows in smith’s-work. 20 SOS THE PRACTICAL METAL-WORKER’S ASSISTANT. Theoretically, the thickness of the upper edge of the cylinder would be doubled, and the lower edge would retain its original thickness, as in 256; whereas in extending the margin of the disk by solid blows as in Fig. 252, the thinned edge would be found to taper away, also in a straight line, from the full thickness even to a feather edge if sufficiently continued, but neither of these cases would be admissible, as the general object is to retain a uniform substance. In equalizing the thickness of the cylindrical tube, Fig. 256, the solid blows would thin the metal, but at the same time throw it into a larger circle, it would then require to be again driven in¬ wards, which would again slightly thicken it. So that in reducing the metal to uniformity, two distinct and opposite actions are going on; and upon the due alteration, combination, or proportioning of which, will entirely depend the ultimate form: that is, whether the metal be allowed to continue as a cylinder; to expand or to contract, either as a cone or as a simple curve; or to serpentine in in any arbitrary manner, according as the one or other action is allowed to predominate with the gradual development. The treat¬ ment of such works with the hammer, is unlike spinning the teapot, at those parts of the work where the metal is folded down in close contact with the solid revolving mould therein employed; but in completing the upper part on the small block, Fig. 243, the burn¬ isher and the rubber maybe considered equivalent to the two anta¬ gonist forces, which lead the hammered vessel inwards, or outwards at the will of the operator. This subject is too wide to enable any thing more to be offered than a few general features, and I shall therefore proceed to trace briefly the practice in some examples. Figs. 258 259. Fig. 258 represents the first stage of making the half of a cop¬ per ball; the metal is first driven with a mallet into a concave bed, generally of wood, in which it is hastily gathered up to a sweep of about the third part of a sphere, as a, a, Fig. 259; but this puck¬ ers up the edge like a piece of fluted silk, or the serpentine margin of many shells, in the manner represented at///, Fig. 260, which is of twice the size of 259. The next step is to remove the flutes or puckers by means of blows of the raising hammer, applied externally as indicated by the black lines at h, Fig. 260; and in Fig. 261 are represented, on a still more enlarged scale, the relative positions of the hammer, WORKS IN SHEET METAL. 307 anvil, and work. Thus A represents the globular face of the anvil, B the rounded edge of the raising hammer, which like the pane of an ordinary hammer, stands at right angles to the handle, and a 1, shows the work, a being the edge, and 1 the point of the flute. The blows of the hammer are made to fall nearly on the centre o, of the anvil, and at a small angle with the perpendicular, the hand being on the side a. A few blows are given as tangents, or directly across the point of the flute, and when it exceeds the width of the hammer, oblique blows are given to restore the pointed character, to be followed by other blows parallel with the first, as shown at h, Fig. 260. These hollow blows cause the sides of the flutes to slide into one another, almost as when two packs of cards, placed like the ridge of a house, penetrate into each other and sink down flat: in a manner somewhat resembling that by which the original and extreme margin in Fig. 257, becomes, by the succes¬ sive blows, contracted to the inner circle; but in the present case the plait slides down to the general curve of the spherical dish. Figs. 260 261. h 8 If, however, the puckers of a large globe were entirely removed by hollow blows, the central lines of the flutes would become thickened, and therefore solid blows are mingled with them, or rather the one blow partakes of the two natures. Thus from the curvature and oblique position of the hammer, Fig. 261, its face is solid at 5 , to that part immediately below it, but towards h, it rather bends than thins; the flatter the curves of the two surfaces, the greater the extent of the solid or thinning blows. The plaits are not, however, entirely gathered up, as the dish a, a, Fig. 259, always opens a little, from the metal becoming stretched under the treatment for removing the flutes. Throwing the works into flutes as described is not imperative, for the hemisphere might be entirely raised, as in the succeeding step, by blows on the outer surface upon a convex tool or head, but the flutes quicken the process, and speedily give a concavity which is convenient, as it makes the work hang better on the rounded face of the anvil. The outer curve a a, Fig. 259, p. 306, which represents the cop¬ per dish when the puckers have been removed, will not be sent into the hemispherical form, or the inner line d d, at one process, but will progressively assume the curvatures b b, c c, and some- 808 THE PRACTICAL METAL-WORKER’S ASSISTANT. times many others; neither will the work be changed from the curve a a, to that of b b, at one sweep, or as with the burnisher in spinning even by one consecutive ring or wave. The hammer must necessarily operate by successive blows arranged in circles, the proximity of which circles will at length include within their range the entire sweep a a, or b b, each of which is called a course: and before proceeding from one course or sweep to the next, the metal requires to be annealed. Figs. 261 and 262 explain the transition or conversion from the first sweep a, to the second sweep b ; the black lines represent the metal after a circles of blows have been given. Fig. 262 shows the narrow edge of the raising-hammer, in the act of descending upon the centre of the head or stake, and as a tangent to the circle; it first throws in a little rim at 1, which connects the new and old sweeps by a curve or ogee: then another little circle 2, will be simi- Figs. 262 263. m a b n p larly gathered in, then 3, 4, 5, and so on, up to the edge. Now the artifice consists in making the intervals both of the great sweeps, a, b, c, Fig. 259, and of the little waves 1, 2, 3, of Fig. 262, as large as practicable, provided they do not cause the exterior metal to pucker or become in plaits, as this would endanger its ultimately cracking at those places, where the metal might have become plaited. In thus raising-in the metal, it necessarily becomes thickened from its contraction in diameter, but as in Fig. 261 the hammer at h, gives a hollow blow and bends, whilst the part s, gives a solid blow and thins, the two effects are thus combined; and when they are duly proportioned, by a hammer more or less round, and blows more or less oblique, the true thickness as well as the desired change of figure are both obtained. It is easier to get the hemisphere by a little excess of thinning, or by a superfluity of blows: so that the less skilful workman will use a piece of copper of seven inches diameter, with additional blows, for a six inch hemisphere; but the more skilful will take a piece of seven and a half inches diameter, and obtain the work with less labor. Occasionally, when the work is common and WORKS IN SHEET METAL. 309 thin, from three to six hemispheres or other pieces are hollowed together, the outer piece is cut as a hexagon or octagon, and its angles are bent over to embrace the inner pieces, before the pro¬ cess of hollowing is begun, and which scarcely consumes more time than for one only. This is a general practice in hollowing tin- works, such as the covers of sauce-pans, as the number of thick¬ nesses divide the strength of the blows; the several pieces are then twisted round at intervals, so as to arrange them in a different order, which mixes the little imperfections, and tends to their mutual correction: the raising process represented in Fig. 262 is also performed upon two or three pieces at a time, when they are sufficiently thin to permit it. One of the most conspicuous and remarkable examples of raised works is the ball and cross of St. Paul’s Cathedral, London. The old ball consisted of sixteen pieces riveted together; the present, also 6 feet in diameter and ^ inch thick, was raised in two pieces only, and may therefore be considered to mark the improvement in the coppersmith’s art in making large works, such as sugar- pans, stills, etc. The metal was first thinned and partly formed under the tilt- hammer at the copper-mills, or sunk in a concave bed; the raising was effected precisely as explained in Fig. 262, and with hammers but a little larger than usual; the two parts were riveted together in their place, and the joint is concealed by the ornamental band. All the work is modern, and is mostly hammered up, except the cast gun-metal consoles beneath the ball, which formed part of the original metallic edifice; a name to which it is justly entitled, the height being 29 feet, and the weight of copper 3£ tons. The new ball and cross are strengthened by a most judicious inner framing of copper and wrought-iron bars, stays, bolts, and nuts, extending through the arms and downwards into the building; thus adding about 2 tons of iron to the load of copper, and to the 38 ounces of gold used in its decoration. Having conveyed the full particulars for raising a hemispherical shape, the modifications of treatment required for various other forms will be sufficiently apparent. Thus, below the dotted lines a d f in Fig. 263 the sweeps are exactly the same as in Fig. 259, but the metal rises higher from having been originally larger; in the courses g h, it is first kept rather thicker on the edge, and to¬ wards the conclusion, it is thinned on the edge to the common substance, and curled over by hollow blows from within, although the whole figure might be produced by external blows, but which would be a more tedious method. On the other hand, by the continuance of the raising in, ex¬ plained by diagram 262, the metal would be gathered into a smaller diameter through the steps i,j, k, l, in the latter of which the metal would become thickened, unless the solid or thinning blows were allowed to predominate. If enough metal had been given in the first instance, when the mouth had been contracted as to the form 310 THE PRACTICAL METAL-WORKER’S ASSISTANT. of a teapot, it might be extended upwards as a cylindrical neck, in the manner explained in Fig. 256, and curled over at the top, as on the opposite side of Fig. 263, at h. To lessen the labor of raising works from a single flat plate, soldering is sometimes resorted to; thus the teapots, Figs. 190 and 192, page 284, might be made in two dished pieces, and soldered at the largest diameter; the lofty vase or coffeepot, Fig. 194, could be made from a cylinder of midway diameter soldered up the side, the bulge being set-out by thinning the metal, and the contraction above being drawn-in by hollow blows. Vases in the shape of an earthen oil jar, or of the line l d n, Fig. 263, could be made from a cone such as o p, with a bottom soldered in ; these preparations would save the work of the ham¬ mer, although such forms, and others far more difficult, could be raised entirely by the hammer from a flat piece of metal. Should any of the above vessels require a solid thickened edge or lip, beyond that which would result from the drawing-in of the metal, it would be necessary to select a piece of metal of smaller diameter but thicker, and to retain the margin of the full thick¬ ness by directing all the blows within the same; sometimes, on the other hand, works require to be thinned on the edge; these are then cut out proportionally smaller than their intended sizes, as illustrated by the following example, which is considered the most difficult of its kind. The bell of a French horn, together with the first coil of the tube, are made of a flat strip of metal about 4 feet long and 2 inches wide; for making the bell of the instrument, there is an enlargement at one end of the strip, in the form of the funnel piece 189, and of the width of 16 to 22 inches, the smaller piece being adopted when the bell is required to be very thin. The narrower piece of metal, when first bent up, much resembles the butt end of a musket, terminating in a small tube; the metal is united and soldered down the edge with a cramp or dovetail joint, Fig. 232 ; it is next thrown into a conical form of about five inches diameter, and expanded from within, first with blows of a wooden mallet upon a wooden block, and then with those of a hammer on iron, stakes. When nearly finished, or about one foot diameter, it is ham¬ mered very accurately upon a cast-iron mould turned exactly to the form of the bell, which is thus rendered much thinner than the general substance, and remarkably exact; the band containing the wire for stiffening the edge of the bell is attached by dexterous hammering, and without solder. To bend the tube to the curve without disturbing its circular section, it is filled with a cement, principally pitch, which allows the tube to be bent to the scroll of the instrument, without suffering the metal to be puckered or dis¬ turbed from its true circular section ; and in bending similar tubes to smaller curves, they are filled with lead. These materials serve as flexible and fusible supports, which are easily removed when no longer required. WORKS IN SHEET METAL. 311 Should any of the raised works have ornamental details, such as concave or convex flutes, or other mouldings, they would be mostly overlooked until the general forms had been given; and then every little part would be proceeded with upon the same principles of solid and hollow blows. Each of the series of flutes would be first slightly developed all around the object, then more fully, and so on until the completion; when, however, the details are so large, as to form what may be considered integral parts, it is necessary to prepare for them at an earlier stage. Thus, to take an excellent familiar example, let Fig. 264 repre¬ sent plans, 265 sections, and 266 elevations of jelly moulds, many of which require the greatest skill of the coppersmith. The gen¬ eral outline is that of a cylinder abed, upon a larger cylinder e f g h, as a base. The twelve large and deeply indented flutes or finials, rise perpendicularly to a great height from the plane sur¬ faces a c and e b, and yet the whole is hammered out of one flat plate. Figs. 264 265 266. The first step is to raise the summits of the flutes i or k, pre¬ paratory to the general formation of the upper cylinder abed, and then the two are worked up together, leaving for a time the expanded base e f g h, but ultimately the whole receive a general attention in common. If the flutes were polygonal, and terminated in ornaments like spires or finials, as at k, they would be first treated as if for the more simple or generic form i, and the details would be subsequently produced. The skill called for in such works is greatly enhanced by the attention which is required to preserve a nearly uniform thickness in the metal, notwithstanding the apparent torture to which it is submitted; and this is only endured in consequence of a frequent recurrence to the process of annealing, which reinstates the mallea¬ ble property. In cases of extensive repetition, or where large numbers of any specific shape are required, expensive dies of the exact forms are employed ; but these are only applicable to objects in small relief, and to those in which the parts are not quite perpendicular. Dies would be entirely inapplicable to objects such as the jelly moulds, Fig. 265, although a common notion exists that they are rapidly 312 THE PRACTICAL METAL-WORKER’S ASSISTANT. made by that method, but which is in general utterly impossible when such objects are made in one piece. In all such cases the metal has to undergo the same bendings and stretchings between the dies as if worked by the hammer, and which unless gradually brought about are sure to cut and rend the metal. The pro¬ duction of many such forms with dies is therefore altogether im¬ practicable. Figs. 267 268. For example, the pattern or moulding, z, Fig. 267, is only in small relief, and yet the flat piece of metal a would be cut in two or more parts if suddenly compressed between the dies A B, as the edges i j would first abruptly bend and then cut the metal, without giving it the requisite time to draw in, or to ply itself gradually to the die, beginning at the centre as in the process of hammering. In Fig. 268 the successive thicknesses obliterate the effect of the acute edges of the bottom die B ; the face and back of every thick¬ ness differ, as although parallel they are not alike, but they become gradually less defined, so that in Fig. 268 the top die A requires nothing more than a flowing line with slight undulations. There¬ fore, when two or three dozen plates are inserted between the dies A B, the transition from a to z is so gradual that the metal can safely proceed from a to b, from b to c, and so on, and it will be progressively drawn in and raised without injury. When one or two pieces alone are required, they are blocked-down to fit the mould by laying above them a thick piece of lead, which latter is struck with the mallet or hammer. By the yielding resistance the lead opposes, the thin metal is drawn into the die with much less risk of accident than if it were subjected to the blows without the in¬ tervention of the lead. In producing many pieces, however, one piece, a, is added at the top, between every blow, and one piece, z, is also removed from the bottom. Occasionally, two, three or more are thus added and re¬ moved at one time, and generally, as the concluding step, every piece is struck singly between the dies, such as Fig. 267, which exactly correspond. In general the process of annealing must be also resorted to once or more frequently during the transition from a to z. For the best works the bottom die is mostly of hardened steel, sometimes of cast-iron or hard brass. The top die is also of hardened steel in the best works, but in very numerous cases WORKS IN SHEET METAL. 813 lead is used, from the readiness with which it adapts itself to the shape required. Stamping is very common for many works in brass, but which would be inapplicable if the pieces had perpendicular and lofty sides, as in Fig. 265, page 311. Such lines, although rounded by the successive thicknesses of metal, would still present perpendicu¬ lar sides, and therefore render this mode of treatment with dies impracticable, without reference to cost. Thimbles are raised at five or six blows, between as many pairs of conical dies successively higher, but the metal requires to be annealed every time. Peculiarities in the Tools and Methods. —Before con¬ cluding the remarks on raised works, it may be desirable to revert to some of the principal and distinguishing features of the tools employed in these arts. As a general rule, it will be observed that all these manifold shapes are the more quickly obtained the more nearly the various tools assimilate to the works to be wrought. For instance, the several dies and swage tools quickly and accu¬ rately produce mouldings of the specific forms of the several pairs of dies; but it is utterly impossible to extend this method to all cases, and the progressive changes required, from the flat disk, the cylinder or cone, as the case may be, to the finished object; and therefore certain ordinary forms of tools can alone be employed, and they are continually changed as the work proceeds. For hollow works with contracted mouths, the inner tools are required gradually to decrease in bulk and to increase in length, in order to enter the cavities; but they can be rarely the exact counterparts of the transient forms of the works, nor is it always desirable they should be so. The tools are often required to be bent at the end, to extend within a shoulder or gorge. The small stake in the tool, Fig. 203, is an example of this; the dotted line represents the work, such as the perforated cover of a cylinder, or the top of a teakettle. The strong wrought-iron arm or horse, Fig. 203, carries the small steel tools, and which latter may be also fixed by their shanks either in the bench or vice, according to circumstances. There are many curious circumstances respecting the modifica¬ tion of the materials for, as well as the forms of, the hammers and anvils, if the use of these terms may be extended to the various contrivances, by the action and re-action of which thin metal works are produced; and the concluding examples are advanced to bring some of these peculiarities of method into notice. The plated metals have so thin a coating of silver, that they re¬ quire more expert hammering than similar works in solid silver, otherwise the removal of the bruises left by the hammer, by scrap¬ ing and polishing, might wear through the silver and show the copper beneath. The bruises are therefore driven to the copper side, by hammering upon the silver or the face, with a very smooth planishing hammer, and covering the anvil or bottom tool with doth. On account of the elasticity thus given, the blows become 314 THE PRACTICAL METAL-WORKER’S ASSISTANT. so far hollow that all the little bruises descend to the copper side, or that which is exposed to the cloth, and the face becomes per¬ fectly smooth. When the inside of a vessel is required to be smooth, it is the hammer that is covered with cloth, stretched over it by an iron ring, and the polished stake or head within the vessel is left uncov¬ ered ; and in those cases in which the work is required to be good on both sides, the faces both of the hammer and anvil are each muffled; this gives them some of the elasticity of wooden tools, but with superior definition of figure. Plated works are generally furnished with an additional thick¬ ness of silver at the part to be engraved with a crest or cipher, in order that the lines may not penetrate to the copper; should it, however, be requisite to remove the engraved lines for the substi¬ tution of others, the following mode is resorted to. The object is laid upon the anvil over a piece of sheet lead and it is struck with a bare hammer upon the engraved lines ; these latter are therefore hollow as regards the face of the hammer; in conse¬ quence of which, the re-action of the lead causes it to rise in ridges corresponding with the engraved lines, and to drive the thin plated metal before it. .The device is thus in great measure oblit¬ erated from the silver face and thrown to the copper side, so as to leave much less to be polished out; this ingenious method is ap¬ propriately called reversing. In making vases, such as Figs. 192 and 194, page 284, the metal is first driven into concave wooden blocks with a wooden mallet, as in Fig. 258, in order to gather up the metal into the fluted concave 260, but without making any sensible alteration in its thickness. In the next stage of the work, metal tools are alone employed, whether the object be made by raising-in with hollow blows, or by setting-out with solid blows, as adverted to; and the sizes and curvatures of the tools require to be accommodated to the changes of the work. Supposing the vases to have either concave or convex flutes, ornamental details are now sketched with the compasses upon the plain surface of the vase; and if from the shape of the works swage tools similar to Fig. 212, cannot be employed for raising the projecting parts, they are snarled-up, by the method represented in Fig. 269. Thus at v are the jaws of the tail vice, in which the snarling- iron s, is securely fixed : the extremity b, which is turned up, must be sufficiently long to reach any part of the interior of the vessel, but yet small enough to enter its mouth. The work is held firmly in the two hands, with the part to be raised or set out exactly over the end b ; and when the snarling-iron is struck with a hammer at h, the re-action gives a blow within the vessel, which throw the metal out in the form of the end of the tool, whether angular, cylindrical, or globular: except in small works, two individuals are required, one to hold and the other to strike. WORKS IN SHEET METAL. 315 Figure 270 stows the last stage of the work prior to polishing; thus in finishing the flutes and other ornaments after they are snarled-up, the object is filled with a melted composition of pitch and brick-dust—sometimes the pitch is used alone, or common resin is added—the ornaments are now corrected with punches or Figs. 269 270 271. chasing tools of the counterpart forms of the several parts ; some portions of the metal are thus driven inwards, whilst those around rise up from the displacement and reaction of the pitch. To avoid injuring the lower surface of the work it is supported upon a sand¬ bag b, like those used by engravers, and* the perpendicular lines p, denote the usual position of the chasing tool. Works in copper and brass are sometimes filled with lead at the time of their being chased, but the silversmiths and goldsmiths are studious to avoid the use of this metal, as, if it gets into the fire along with their works, it is very destructive to them. Pitch and mixtures of similar kind, are constantly used in the art of chasing in its more common acceptation ; from its adhesive and yielding nature it is a most appropriate support, as it leaves both hands at liberty, the left to hold the punch, the right for the small hammer used in striking it.. The pitch-block, Fig. 271, is employed to afford the utmost choice of position for works from the smallest size to those of six or eight inches long. The lower part is exactly hemispherical, and it is placed upon a stout metal ring or collar of corresponding shape, covered with leather. The mass of metal makes a firm solid bed to sustain the blows, and the ball and socket contact, allows the work to assume every obliquity, and to be twisted round to place any part towards the artist. Large flat works in high relief are frequently sketched out and commenced from the reverse face, the prominent parts of the sub¬ ject being sunk into the pitch, which after a short time must be melted away to allow the metal to be annealed; and this is fre¬ quently required when the works are much raised. In the con¬ cluding steps the artist works from the face side. Many of the chased works are cast in sand moulds from metal models, which have been previously chased nearly to the required forms; the castings are first pickled to remove the sand coat, and in such cases, chisels and gravers are somewhat used in removing the useless and undercut parts. 816 THE PRACTICAL METAL-WORKER’S ASSISTANT. Many ancient specimens of armor, gold and silver plate, vases and ornaments, are excellent examples of raised, chased, and in¬ laid and engraved works, both as regards design and execution. In our own times, the Hungarian silversmith, Szentepeteri, has produced a very remarkable alto-relievo in copper, taken from Le Brun’s picture of the battle of Arbela, in which some of the legs of the horses stand out and are entirely in relief from the back¬ ground. The art of chasing may be considered as the sequal to that of forging (that is, setting aside the employment of the red-heat), but the various hammers and swage tools now dwindle into the most diminutive sizes, and are required of as many shapes as may nearly correspond with every minute detail of the most complex works. Some of them are grooved and checkered at the ends, and others are polished as carefully as the planishing hammers, that they may impart their own degree of perfection and finish to the works; in a similar manner that the polish and excellence of coins and medals are entirely due to that of the dies from which they are struck, the chasing process being as it were a minute subdivision of the action of the die itself. The Principles and Practice of Flattening thin Plates of Metals with the Hammer.—I have purposely reserved this subject to be distinct, on account of its great general importance in the arts, and have placed it last, in order that the various applica¬ tions of the hammer might have been rendered comparatively familiar; for, although the plane surface may appear to be of more easy attainment than many of the complex forms which have been adverted to, such is by no means the case. . The methods employed are entirely different from that explained at page 153, in reference to flattening thick rigid plates, which are corrected by enlarging the concave side, with blows of the sharp rect¬ angular edge of the hack-hammer, applied within the concavity. A method which bears some analogy to that employed by the joiner in straightening a board which is curved in its width, namely, the contraction of its convex side by exposure to heat. In thin metal plates neither of these modes is available, as the near proximity of the two sides causes both to be influenced in an almost equal degree by any mode of treatment. Thin plates are flattened by means of solid and hollow blows, which have been recently explained, but they require to be given with considerable judgment; and a successful result is only to be obtained by a nice discrimination and considerable practice. All therefore that can be here attempted is an examination of the prin¬ ciple concerned, and of the general practice pursued; as the pro¬ cess being confessedly one of a most difficult nature, success is only to be expected or attained by a strict and persevering regard to principle. As respects thin works, no figure is so easily distorted as the true plane, and this arises from the very minute difference which WORKS IN SHEET METAL. 317 exists between tbe span or chord of a very flat arch, and its length measured around the curve. For example, imagining the span of an arch to be one inch, and the height of the same to be one-twen¬ tieth of an inch, the curve would be only about one 200th of an inch longer than the span: and therefore, if any spot of one inch diameter were stretched until, if unrestrained, it would become one inch and one 200th in diameter, such spot would raise up as a bulge one-twentieth of an inch high. This trivial change of mag¬ nitude would be accomplished with very few blows of the ham¬ mer, and much less than this would probably distort the whole plate. In general, however, there would be not one error only, but several, the relationship of which would be more or less altered with nearly every blow of the hammer; thence arises the difficulty, as the plane surface cannot exist so long as any part of the plate is extended beyond its just and proportional size, and which it is a very critical point to arrive at. There is another test of the unequal condition of flat works be¬ sides that of form, namely, their equal or unequal states of elasti¬ city, and which is an important point of observation to the work¬ man. For instance, if we suppose a plate of metal to be exactly uniform in its condition, it will bend with equal facility at every point, so that bending a long spring, or saw, will cause it to assume a true and easy curve; but supposing one part to be weaker than the remainder, the saw will bend more at the weak part, and the blade will become as it were two curves moving on a hinge. When such objects are held by the one extremity and vibrated, the per¬ fect will feel as a uniformly elastic cane; the imperfect, as a cane having a slight flaw, which renders it weak at one spot; and in this manner we partly judge of the truth of a hand-saw, as in shaking it violently by the handle, it will, if irregularly elastic, lean towards the character of the injured cane, a distinction easily appreciated. Fig. 272. A thin plate of metal can only be perfectly elastic, when it is either a true plane or a true curve, so that every point is under the same circumstances as to strength. Thus a hemisphere, as at a, 272, possesses very great strength and rigidity owing to its convexity, but as the figure becomes less convex it decreases gradually in strength, and when it slides down to the plane surface, as at f the metal assumes its weakest form. A nearly plane surface will necessarily consist of a multitude of convexities or bulges varying in size and strength, connected by 318 THE PRACTICAL METAL-WORKERS ASSISTANT. intermediate portions, which, may be supposed to be plane surfaces; the whole may be considered as greatly exaggerated in the figure. The bulged parts are stronger than the plane flat parts, it follows that the bending will occur in preference at the plane or weak parts of the plate, precisely as in the injured cane. When the bulges are large but shallow, they flap from side to side with a noise at every bending, as their very existence shows that they cannot rest upon the neutral or straight line; such parts are said to be buckled, their ready change of position renders them flaccid and yielding under the pressure of the fingers, and they are therefore called loose parts, but at the same time it is certain thatr they are too large. On the contrary, those parts which are intermediate between the bulges, feel tight and tense under the fingers, because they are stretched in their positions and rendered comparatively straight, by the strong edges of the bulged or convex parts: the flat portions are the hinges upon which the bulged parts move, and such flat parts are sensibly too small for their respective localities, the others being too large. Now, therefore, in prescribing the rule for the avoidance of these errors, it is simply to treat every part alike, so that none may be stretched beyond its proper size so as to become bulged, and thereby to distort the whole plate. When the mischief has occurred, the remedy is to extend all the too-small parts, or the hinges of the bulges to their true size, so as to put every part of the plate into equal tension, by allowing the bulged or too-large parts room to expand. Uniform blows should be therefore directed upon all the straight or too-small parts of the plate, the force and number of the blows being determined by the respective magnitudes of the errors, and the rigidity of the plate. In flattening plates, the greater part of the work is done with solid blows upon a true and nearly flat anvil; the face of the ham¬ mer is slightly round, and its weight and the force of the blows are determined by the strength of the plate, the slighter plate requiring more, delicate blows, and being more difficult to manage. In the commencement, the rectangular plate is hammered all over with great regularity in parallel lines beginning from one edge; it is generally turned over and similarly treated on the other side. Cir¬ cular plates are hammered in circular lines beginning from the centre, that is supposing the plates of metal to be soft, and in about the ordinary condition in which they are left by the laminating rollers; as the equable hammering gives a general rigidity, which serves as a foundation for the correctional treatment finally pur¬ sued. With a steel plate hardened in the fire, and which is already far more rigid than the soft plate, it is necessary to begin at once upon the reduction of the errors and distortions, which usually occur in the hardening and tempering. The hammer should be made to fall on one spot with the uni¬ formity of a tilt-hammer, the work being moved about beneath it. WORKS IN SHEET METAL. 819 As, "however, the regularity of a machine is not to be expected from the hand, it is scarcely to be looked for that the work shall be at once flat. Whilst the errors are tolerably conspicuous or consider¬ able, the man accustomed to the work will still keep the hammer in constant motion, and will so shift the work, as to bring the tight ■parts alone beneath its blows, hammering with little apparent con¬ cern just around the margins of the loose parts, or at the foot of every rise. As the plate becomes more nearly flat, it is necessary to proceed more cautiously, and to hold the plate occasionally be¬ tween the eye and the light to learn the exact parts to be enlarged ; the straight-edge is also then resorted to. In many works, especially in saws which require very great truth, the elasticity is also examined; this is frequently done by holding the opposite edges of the plate between the fingers and thumbs, and bending them at various parts. As previously ex¬ plained, all the portions which are technically called tight, or those lines upon which the loose enlarged parts appear to move as on hinges, are strictly the parts to be extended by gentle hammering. For instance, supposing that in the plate, Fig. 273, there were only Figs. 273 274. one central buckle a, the whole exterior portion would require to be stretched, beginning from the base of the bulge: but it must be remembered the extreme edges of the plate will yield with greater facility than the more central parts, and therefore require some¬ what fewer blows, as the blows are all given as nearly as possible of the same intensity, and the number of them is the source of variation. If, as it is more to be expected, there are two or more loose parts, such as a, and b c, the more quiescent part between them must be first hammered, as working upon any loose or bulged part only magnifies the evil. Where the intermediate space is narrow, as at d, less blows will be needed, and such tight parts will soon, and sometimes very suddenly, become loose from the two bulges melting into one. It should be rather the general aim to throw the several small errors into a large one, by getting the plate into one regular sweep; dealing the blows principally between the dotted lines, not carelessly so as to increase the general departure from the plane surface, but with an acute discrimination to lead all the defects in the same direction, by making the plate as it were a part of a very great cylinder, as at e or f Fig. 274, but with as little curvature as possible. 320 THE PRACTICAL METAL-WORKER’S ASSISTANT. When this is accomplished, and that the work is free from loose parts, it is hammered on the rounding side, in lines parallel with the axis of the imaginary cylinder ; so that in e the lines would be parallel with the edge from which the rise commences, and in/ or the plate which is bent diagonally, the lines of blows would be necessarily oblique, although as regards the curvature, the same as in e. The reason why any reduction of curvature should at all result from this treatment (action and reaction being alike) is due to the greater roundness of the hammer than the anvil; the rounder hammer effects the change more rapidly, but also the more indents the work. In a circular saw, the general aim is first to throw the minor errors into one regular concavity, which may be supposed to extend to b b in the imaginary section, Fig. 275, and then the margin a b would be hammered in a proportional degree, to enlarge it until it just allowed the interior sufficient room to expand to the plane surface. 9 It may happen in the course of the hammering that from b to b becomes loose, whilst the extreme edge a a is also loose, and that the intermediate part towards b requires to be stretched. These minor differences cannot be told alone by bending the plate with the fingers, as errors frequently exist which are too minute to yield to their pressure, and then the eye and straight-edge are conjointly employed in the examination. In a saw, the general aim is to leave the edge rather tight or small, as then the small amount of expansion it acquires when at work, from heat and friction, will enlarge the edge just sufficiently to bring the saw into a state of uniform tension. Otherwise, if before the saw is set to work the edge is fully large enough, when expanded by the heat it is almost sure to become loose on the edge, and to vibrate from side to side, without proper stability, so as to produce a wide irregular cut, and make a flanking whip-like noise, arising from the violent vibration of the buckled parts of the plate in passing through the saw kerf; the sides of the wood will then exhibit ridges like the ripple-marks on the sandy shore. In hammering all plates, preference should in the like manner be given to keeping the edge rather small or stiff, to serve as a margin or frame to the more loose parts within. It gives a degree of stability somewhat as if the object had a thickened rim, and when a rim really exists, the process of flattening is comparatively easy. If by undue stretching the edge is made too loose, the whole piece becomes flaccid and very mobile, and we seem to lose the WORKS IN' SHEET METAL. 321 governing power, or those retaining points by which the changes of the plate are both influenced and rendered apparent. The edge should be therefore always kept somewhat tight, from being pro¬ portionally less hammered, especially as the edge more easily admits of expansion than the inner part. As a general rule, it may be said, that every part of the plate which is straight and tense, whilst others are curved and flaccid, denotes that every straight part is under restraint; and that its straightness is due to its being, as it were, stretched, either length¬ ways or around its edges, by the other parts, which are too loose, and therefore arched and also strong. In such cases, the straight lines require to be extended in length, to allow sufficient room for the curves to expand to their proportional sizes. This refers not only to small local errors towards the inner part of the plate, as explained by diagram, Fig. 273, p. 319 ; but should the one edge of a plate be tolerably straight, whilst the opposite is loose and flaccid, the rule also applies with equal truth, and the straighter side must be hammered. In this case the curved side is as it were a great bulge cut in two parts. Should a circular saw have a sudden dent, such as at g, Fig. 275, on the last page, standing the reverse way, and which may result from its having rested upon a small lump of coke whilst in the fire, the first blows will be given on the hollow side, between the lines i i, to lessen the abruptness of the margin by stretching it to the dotted curve, and then it will be driven downwards by violent blows, to form a part of the general sweep or concavity. A little time is gained by these driving blows over the mode of stretching by the hammer. The foregoing descriptions have all referred to solid blows, upon the face of the hard anvil, but to expedite the process recurrence is often had to blocking, which is only one application amongst many others of a wooden anvil or block with a narrow flat-faced hammer, such as Fig. 248. In this case the blows are to a certain, extent hollow, as the wood immediately beneath the hammer-face yields to the blow, whereas the margin around the same does not. Such blows are therefore unquestionably hollow, and bend with very little stretching. The blocking is considerably employed in saw-making after the loose parts have been entirely removed, as the hollow blows cor¬ rect any slight errors of figure, by bending alone, and with little risk of stretching the plates, if the work be delicately performed. Towards the conclusion, however, all the different modes of work are required to be used in combination, as the true condition of the plate is only the exact balancing of all the forces, or of the tension of the several parts; and it constantly happens that atten¬ tion to one error causes a partial change and fluctuation throughout the whole. It therefore requires great tact to know when to leave the anvil for the block, and when to return to the anvil, and so on alternately; and also which side of the plate should be upwards 21 322 THE PRACTICAL METAL-WORKER'S ASSISTANT. for the time, which particular points should be struck, and the required force of the blows. Of course, within certain limits, a thick plate is easier to hammer than a thin one, as the latter is difficult from its excessive mobility; also a soft plate of iron is more difficult than a hard plate of steel, although the latter requires more blows to produce the same effect; but when the works are very thick they become laborious, and the difficulty always increases rapidly with the size of the plate. Those who may desire to practise this art should therefore com¬ mence with a plate some 4, 6, or 8 inches square, and moderately stout, and subsequently proceed to pieces larger and thinner. They will also find some advantage in raising the anvil to within about a foot of the eye, as the alterations can be then more easily seen whilst the work lies on the anvil, and the effect of any predeter¬ mined blows can be the better watched. One other observance is essential, namely, patience; as, although, the process is thoroughly reducible to system, and no blow should be struck in vain, the beginner will frequently find it necessary to pause, examine, and consider, especially as the errors decrease; whereas the accus¬ tomed eye will follow the fluctuations of the plate almost without intermission of the blows, and will also accomplish the task with the fewest possible number of blows, which is the great object. Indeed it may happen from hammering some parts of a plate excessively and improperly, that it is rendered so hard and rigid, as to make its correction very tedious, or indeed nearly impossible without previous annealing, as the plate might burst or crack from the extension being carried beyond the safe limit of malleability. As in raised works, the annealing is mostly done by a gentle red heat; but in hardened steel plates, a slight increase of temperature barely sufficient to discolor the plate, will make a perceptible dif¬ ference ; and this latter process is always the last step in making a saw, in order to restore, by a gentle heat, the proper elasticity which has been mysteriously lost in the grinding, polishing, and hammering required in its manufacture. CHPTER XVIII. PROCESSES DEPENDENT ON DUCTILITY. Drawing Wires, etc. —The ductility of many of the metals and alloys, or the quality which allows them to be drawn into wires, is applied to a variety of curious uses in the manufacturing arts, and the process may be viewed as the sequel to the use of grooved and figured rollers; but the ductile metals submit to this process with various degrees of perfection. / PROCESSES DEPENDENT ON DUCTILITY. 323 In drawing wire, the metal is first prepared to the cylindrical form, either directly by casting, or between rollers with semicir¬ cular grooves; and the process is completed by pulling the metal through a series of holes gradually less and less, made in a me¬ tallic plate, by which the wire becomes gradually reduced in size, and elongated; but, as in rolling, the process of annealing must be resorted to at proper intervals. In general, the draw-plates are made of hardened steel, and they are formed upon the same principle, whether for round, square, or complex sections, either solid as wires, or hollow as tubes; the substance of the metal is partly kept back, as in a wave, by a narrow ridge within the draw-plate, acting as a bur¬ nisher. The plates are generally made of hardened steel, or else of alloys of partly similar nature, which allow the holes to be contracted and repaired, by closing them with blows of a pointed hammer or punch around the hole. The holes for round wires are sometimes ground out from both sides upon the same brass cone or grinder, the sides of which vary in obliquity from 10 to 30 degrees, according to the metal to be drawn ; for the sake of strength the ridge is mostly nearer to the side on which the metal enters, and the sharp edge is also removed, either by wriggling the plate upon the grinder in order to round the inside, or in any other manner. The end of the wire is pointed, to enable it to be passed through the hole, and it is then caught by a pair of nippers, themselves at the extremity either of a chain, rope, toothed rack, or screw, by which the wire is drawn through by rectilinear motion. The nip¬ pers or dogs resemble very strong carpenters’ pincers or pliers, the handles of which diverge at an angle; they are sometimes closed by a sliding ring at the end of the strap or chain, which slides down the handles of the nippers ; there are some other modifica¬ tions, all acting upon the same principle, of compressing the nip¬ pers the more forcibly upon the wire the greater the draught. It requires a proportionally strong support to resist the strain; and to avoid the fracture of the hardened steel draw-plate, it is usually placed against a strong perforated plate of wrought-iron. In manufactories where large quantities of wire are made, the wire is more usually attached to the circumference of a reel, which is made to revolve by steam or other power. It is necessary often to anneal the wire, but no general rule can be stated in respect to its recurrence; and before resuming the drawing process, the wire is invariably immersed in some acid liquor or pickle, to remove the slight coating of oxide, which would otherwise rapidly destroy the plates (as many of these me¬ tallic oxides are used in polishing), in general some lubricating matter is applied to reduce the friction, as beer-grounds, starch- water or oil; and for gold and silver, wax is generally used. Most of the wire is drawn upon reels, and is therefore met with 324 THE PRACTICAL METAL-WORKER’S ASSISTANT. in circular coils, and it is necessary, in almost every case, to straighten it before use. The soft annealed wires, such as the cop¬ per wire used for bell-hanging, the soft iron binding-wire used in soldering, and others, are stretched and straightened by fixing the one end, and pulling the other with a pair of pliers; or short pieces of soft wire may be straightened by rolling them between two flat boards. So steel wire for making needles is straightened by rolling or rubbing: it is cut up in lengths of 4 or 5 inches, and arranged in cylindrical bundles, within iron hoops of 4 inches diameter; the rubber is a bar of cast-iron, about two feet long, narrow enough to lie between the rings. The hard-drawn and unannealed wires, used for making pins, bird-cages, blinds, and numerous other wire-works, are too elastic to yield to the above methods, and Fig. 276 represents the mode employed to take the spring out of them, or in other words, to straighten these hard wires. The coil of wire on the reel f which revolves on a pin, is drawn through the riddle g, by the pliers. The riddle is a piece of wood or metal with sloping pins, which lean alternately opposite ways, so as to keep the wire close down on the board, and yet to compel it to pursue a slightly zigzag, or rather serpentine course, which is considerably magnified in the figure. In practice, the riddle is made wider than represented, so as to contain about half a dozen rows of pins suitable to as many sizes of wire; between every set of pins, and fixed close down to the board, is a straight wire about three times the diameter of one to be straightened: very great importance is attached to this latter or central wire; being itself straight, it serves as a metallic bed for the small wire to run upon, and it thereby gets worn into furrows crossing it obliquely from pin to pin. The board is retained by two staples at the far end, which fit loosely on two studs or nails driven into the work-bench. Figs. 276 277. b The pins are equivalent to the three forces a, b, c, of the bend¬ ing-machine, page 289, several times referred to. Were the first tnree pins critically placed, they would suffice to bend the wire to the limit of its permanently elastic force, and would leave it perfectly PROCESSES DEPENDENT ON DUCTILITY. 325 straight; commonly, however, five pins are used, and sometimes seven or nine. The same riddle will not serve for wires differing in diameter; and were this simple tool more expensive, so as to render it desirable, a universal riddle might be made by placing the pins b and d, under a simple screw-adjustment; but in prac¬ tice, a tap of the hammer is found sufficient to correct their posi¬ tions. It is necessary to be very particular in pulling the wire througn, not to allow it to lean sensibly against either of the last two pins, or it will assume a curve; and in this manner, by drawing the wire designedly at different angles, it may be thrown into any required circular arc, instead of the right line. Cylindrical shafts may be viewed as large wires, and when they are turned with ordinary care, in a slide-lathe with a back-stay, it becomes pretty certain that the shafts are circular, and of true diam¬ eters ; but they are frequently more or less crooked or bent when they leave the lathe. In straightening the axes or shafts intended for the Calculating Machine, which were of steel, about 6 to 10 feet long and f to 1 inch diameter, three halfiround dies, Fig. 277, a, c, fixed to the bed of a fly-press, and b, to the screw of the same, which was so adjusted that b could only bend the portion of the shaft between a, c, to the limit of its elasticity; and therefore, by keeping the press con¬ stantly at work, drawing the rod through, and twisting it round so as to bend it at every point of its length, every shaft was made per¬ fectly straight. The straightening of black wrought-iron shafts previous to turn¬ ing, is now accomplished by three equidistant rollers, say a foot diameter and twelve feet long, similar to Fig. 216, p. 289. The shaft is heated to redness, and the centre roller is raised at the mo¬ ment of its introduction, and then a few turns are given to the whole; this straightens the shaft, and retains it so until partially cooled; the other end of the shaft, should it exceed the length of the rollers, is then heated, and treated in the same manner. All these modes are highly useful, as they operate upon the ma¬ terials without partially condensing any point, from which unequal treatment a loss of figure would be almost certain to occur, when any such condensed point is partially removed by the turning-tool or otherwise; as it appears to be quite impossible to prevent all sorts of perplexities, when, by any mode of operation, the one point of a material receives a different treatment from the remainder. The great bulk of wire is cylindrical, but draw-plates are also made of various other forms, as oval, half round, square, and trian¬ gular, for the wires Figs. 278; and also of more complex forms, as for the production of steel of the sections of Figs. 279, known as pinion wire, the whole of the illustration being printed from the wires themselves. The largest of 279, serves for the pinions of clocks, and the smallest for those of watches; in these cases the entire arbor (which carries one of the toothed wheels) is made of 326 THE PRACTICAL METAL-WORKER’S ASSISTANT. pinion wire, but tbe teeth are removed from every part, excepting that which works into the adjoining wheel of the train. The plates for pinion wire are exactly the same as the others in principle, and exhibit a remarkable degree of perfection in their construction, as for every size there must be a series of many holes gradually assuming the form of a circular foliated Gothic window, with six, seven, eight or more foils. Some of the printed calicoes and muslins are also curious ex¬ amples of the wire-drawing process; the pattern Fig. 280, consists of no less than 205 different pieces of copper wire of various forms, fixed into a wood block; the surface of the wires, when filed smooth, are printed from after the manner of printers’ types; the few de¬ tached pieces, Fig. 281, show some of the sections of such wires, and which may be combined in endless variety. In the same manner the specimen of music, Fig. 282, is printed from the sur¬ faces of detached wires and slips of copper fixed in a wooden block; this is only one amongst the many ingenious processes for printing music by letter-press or surface printing. Figs. 283 284 285 286. Fig. 283 represents the double-plates or swage-bits used for some of the pieces in Figs. 280 and 282; the dies are fitted into a small frame or cramp with a side screw (much the same as dies for cut¬ ting screws), so that the metal may be gradually reduced by one PROCESSES DEPENDENT ON DUCTILITY. 827 pair of swage-bits. This method is very much employed by the silversmith and goldsmith for mouldings, the tools being much cheaper than rollers: the piece 284 was thus prepared for the edg¬ ing of silver and gold boxes; it is bent round to the form of the box or cover, whether square, circular or oval, and the rebate on the straight side of the band serves for receiving the flat plate to constitute the cover. The most perfect example of this application of the drawing process is in the British Mint: two fixed rollers are employed after the manner of a draw-plate, and the long strip of gold or silver, when rolled very nearly to the thickness, is drawn through the stationary rollers, by dogs attached to one of the links of an endless chain, which is in continual motion from the steam-engine. It was found barely possible to make the surfaces of revolving rollers so truly concentric that the equality of thickness in the metal could be obtained with the rigorous exactness required, so as to dispense entirely with the necessity of scraping every piece individ¬ ually, a mode still practised in some of the Continental mints. The metal, when drawn, is tested by punching out one blank at each end; these are carefully weighed, and if found correct, the whole strip is punched into blanks; and such is the accuracy of the drawing and punching processes, that without the smallest after- adjustment, any fifty or one hundred blanks weigh alike to the fraction of a grain. The window lead, shown in section in Fig. 285, does not admit of being drawn in the ordinary manner, from the softness of the material, nor of being rolled, because of its undercut section; the two principles are, therefore, curiously combined in the glazier's vice. It may be conceived that the shade lines of 286, represent parts of two narrow rollers with roughened edges (equal in thick¬ ness to the glass), which indent the bottom of the groove, and thereby carry the lead between the figured side-pieces, one only shown. In some cases cutting is combined with drawing, cutters are then fixed to the draw plate; this method has been adapted to making rules and similar rods; and in perfecting the flattened wire for the reeds used in looms, the edges are rounded by reeling the wire beneath a forked cutter, a process intermediate between turning and planing. The process of wire-drawing is seldom practised by the general mechanician, and still less by the amateur; but when it is neces¬ sary to produce a wire either of some unusual section not prepared by the manufacturer, or that the equality of size requires more than usual exactness, the process may be accomplished in the small way, by fixing the draw-plate in the tail-vice and drawing the wire through with the pliers or a hand vice, or by a reel moved by a winch handle. Drawing Metal Tubes. —The perfection of tubes is mainly de¬ pendent on the drawing process, conducted in a manner similar to that employed for drawing wire. Many of the brass tubes foi 328 THE PRACTICAL METAL-WORKER’S ASSISTANT. common purposes, when they have been bent up and soldered edge to edge, as in Fig. 231, page 294, are only drawn through a hole which makes them tolerably round and smooth externally, but leaves the interior of the tubes in the condition in which they left the lire after they were soldered, and nearly as soft as at first. The sliding tubes for telescopes, and many similar works, are “ drawn inside and out ,” and rendered very hard and elastic, by the method represented in Fig. 287, the form of the plate b being ex¬ aggerated to explain the shape. For example, the tube when sol¬ dered is forced upon an accurate steel cylinder or triblet, in doing which it is rounded tolerably to the form with a wooden mallet, so Figs. 2S7 288. as to touch the mandrel in places; the end is set down with the hammer around the shoulder or reduction of the triblet, and on the drawing tube and triblet, by means of the loose key or transverse piece a, through the draw-plate b, the tube becomes elongated, and con¬ tracted close upon the triblet at every part, as the metal is squeezed between the mandrel and plate. The fluted tubes for pencil-cases, such as c, are drawn in this manner through ornamental plates, the triblets being in general cylindrical. Some of the drawn tube called joint-wire, is much smaller than d, and is used by silversmiths for hinges and joints. It is drawn upon a piece of steel wire, which being too small to admit the shoulder for holding on the tube, the latter is tapered oft' with a file, and the tube and wire are grasped together within the dogs, and drawn like a piece of solid wire. A semicircular channel is filed half-way in both the parts to be hinged, and short pieces of the joint-wire are sol¬ dered in each alternately. Triangular, square, and rectangular brass tubes are in common use in France for sliding rules and measures. These are made in draw-plates with movable dies, Fig. 288, whi,ch admit of adjust¬ ment for size. The dies are rounded on their inner edges, and are contained in a square frame with adjusting screws, and the whole lies against a solid perforated plate. In the general way, tubes of small diameters are completed at two draughts—sometimes three are used—and by this time the tube has received its maximum amount of hardness ; therefore the first thickness of the metal and the diameter of the plates require PROCESSES DEPENDENT ON DUCTILITY. 329 a nice adjustment. The tube, when finished, is drawn off the triblet by putting the key through the opposite extremity of the same, and drawing the triblet through a brass collar which ex¬ actly fits it; this thrusts off the tube, which will in general be almost perfectly cylindrical and straight, except a trifling waste at each end. It requires a very considerable assortment of truly cylindrical triblets to suit all works; and when the tubes are used in pairs, or to slide within one another, as in telescopes, it calls for a nice cor¬ respondence or strict equality of size between the aperture of the last draw-plate and the diameter of the triblet for the size next larger; and as these holes are continually wearing, it requires good management to keep the succession in due order, by making new plates for the last draught and adapting the old ones to the prior stages. Sometimes, for an occasional purpose, the triblet is en¬ larged by leaving a tube upon it and drawing the work thereupon ; but this is not so well as the turned and ground surface of the steel triblet. Tubes from inch internal diameter and 8 or 10 inches long, up to those of 2 or 3 inches diameter and 4 or 5 feet long, are drawn vertically by means of a strong chain wound on a barrel by wheels and pinions, as in a crane. In Donkin’s enormous tube¬ drawing machine, which is applicable to making tubes, or rather cylinders, for paper-making and other machinery, as large as 26| inches diameter and 6| feet long, a vertical screw is used, the nut of which is turned round by toothed wheels driven by six men at a windlass. All the tubes previously referred to are made of sheet-metals turned up and soldered edge to edge, but lead and thin pipes for water and other fluids have for a long period been cast as thick tubes, some 20 to 30 inches long, and extended to the length of 10, 12, or 15 feet on triblets, which require to be very exactly cylindrical or they cannot be withdrawn from the pipes. The brass tubes for the boilers of locomotive engines are now similarly made by casting and drawing without being soldered, and some of these are drawn taper in their thickness. The ductility of tin is very great. It is from the ordinary tin tube qf commerce (which is cast about 2 feet long, J inch thick, and drawn out to about 10 feet), out of which is made the col¬ lapsable vessels for artists’ oils and colors. Pieces 3 inches long were extended to 36 inches by drawing them through ten draw- plates, which are sometimes placed in immediate succession, the one to commence just as the other had finished. The tube seemed to grow under the operation, and it was thus reduced, without an¬ nealing, from half an inch thick, as cast, to the 170th of an inch thick, and it was stretched fully sixty times in length. This mode of making the tubes of collapsable vessels, has been superseded by another, presenting far greater ingenuity, and described here¬ after. 330 THE PRACTICAL METAL-WORKER’S ASSISTANT. Some of the smallest tin tube of commerce, when removed from the ten-foot triblet, is drawn through smaller plates without any triblet being used. This reduces the diameter, with little change of thickness, so that the half-inch tube becomes a nearly solid wire, measuring about ^ inch diameter externally, which is known as beading, and used to form the raised ledges around tables and counters covered with pewter. The accompanying sectional view gives the hydraulic press, and an arrangement for manufacturing lead pipe. The principle is claimed by Tetham, Cornell, Burr, and others. C is the hydraulic cylinder, and R the ram rising from it. A cross-head is attached to the hydraulic cylinder, and con¬ nected with the upper cross¬ head H by rods I) D. On the top of the ram a head- block B is placed. A foot- block F is attached to the bottom of the lead cylinder L, and the head-block, the foot-block, and the lead cyl¬ inder are secured firmly to¬ gether by bolts T T. By this arrangement the lead “ plug” or cylinder L is moved upwards by the ram R of the hydraulic press. To the upper cross-head H the hollow piston P is at¬ tached by bolts S S. The die Q, placed at the lower end of the piston, hollow throughout, communicates with the aperture A in the upper cross-head. The movable core I, when in use, is firmly fixed to the head- block of the ram and ex¬ tends upwards through the centre of the lead cylinder, and a little above it, so that it is inserted through the die Q at the end of the hollow piston P. The position of the core is regulated by means of the set-screws V V, which move the core and set it centrally to the die. When all the parts are thus arranged the lead cylinder is raised up to the lower end of the piston, the end of the core passing through the die. Fig. 289. C SOLDERING. 331 The ram is forced upwards, carrying the cylinder X that con¬ tains the plug of lead L ; this cylinder X passes over the hollow piston P. The pipe is formed at the point of pressure Q, it then passes through the hollow piston and out through the aperture A. CHAPTER XIX. SOLDERING. General Remarks and Tabular View. — Soldering is the process of uniting the edges or surfaces of similar or dissimilar metals and alloys by partial fusion. In general, alloys or solders of various and greater degrees of fusibility than the metals to be joined, are placed between them, and the solder when fused unites the three parts into a solid mass. Less frequently the surfaces or edges are simply melted together with an additional portion of the same metal. The chemical circumstances to be considered in respect to solder¬ ing are, for the most part, set forth in the section on the fusibility of alloys, pages 217 to 220, to which the reader is referred. It is there explained that the solders must be necessarily somewhat more fusible than the metals to be united; and that it is of primary im¬ portance that the metallic oxides and any foreign matters be carefully removed, for which purpose the edges of the metals are made chemically clean, or quite bright, before the application of the solders and heat; and as during this period their affinity for oxygen is violent, they are covered with some flux which defends them from the air, as with a varnish, and tends to reduce any por¬ tion of oxide accidentally existing. The solders are broadly distinguished as hard solders and soft solders ; the former only fuse at the red heat, and are consequently suitable alone to metals and alloys which will endure that tempera¬ ture ; the soft solders melt at very low degrees of heat, and may be used for nearly all the metals. The attachment is in every case the stronger the more nearly the metals and solders respectively agree in hardness and mallea¬ bility. Thus, if two pieces of brass or copper, or one of each, are brazed together, or united with spelter-solder, an alloy nearly as tough as the brass, the work may be hammered, bent and rolled almost as freely as the same metals when not soldered, because of the nearly equal cohesive strength of the three parts. Lead, tin, or pewter, united with soft solder, are also malleable from the near agreement of these substances ; whereas when cop¬ per, brass and iron are soft-soldered, a blow of the hammer, or any accidental violence, is almost certain to break the joint asun- 332 THE PRACTICAL METAL-WORKER’S ASSISTANT. der, so long as the joint is weaker than the metal generally; and therefore the joint is only safe when the surrounding metal, from its thinness, is no stronger than the solder, so that the two may yield in common to any disturbing cause. The forms of soldered joints in the thin metals have been figured and explained in pages 293 to 296 ; and soldered joints in thicker works resemble the several attachments employed in construction generally. When the spaces between the works to be joined are wide and coarse, the fluid solder will probably fall out, simply from the effect of gravity; but when the crevices are fine and close, the solder will be as it were sucked up by capillary attraction. All soldered works should be kept under motionless restraint for a period, as any movement of the parts during the transition of the solder from the fluid to the solid state disturbs its crystallization and the strict unity of the several parts. In hard-soldering, it is frequently necessary to bind the works together in their respective positions; this is done with soft iron binding-wire, which for delicate jewelry work is exceedingly fine, and for stronger works is the twentieth or thirtieth of an inch in diameter; it is passed around the work in loops, the ends of which are twisted together with the pliers. In soft soldering, the binding wire is scarcely ever used, as from the moderate and local application of the heat, the hands may in general be freely used in retaining most thin works in position during the process. Thick works are handled with pliers or tongs whilst being soft-soldered, and they are often treated much like glue joints, if we conceive the wood to be replaced by metal, and the glue by solder, as the two surfaces are frequently coated or tinned whilst separated, and then rubbed together to distribute and exclude the greater part of the solder. The succeeding “Tabular View of the Processes of Soldering” may be considered as the index, which refers to the ordinary methods of soldering most metals. TABULAR VIEW OF THE PROCESSES OF SOLDERING. Note .—To avoid continual repetition, references are made to the pages of this volume which illustrate the respective sub¬ jects, and also to the lists on the opposite page, in which some of the solders, fluxes, and modes of applying heat are enumerated. SOLDERING. 333 HARD-SOLDERING. 339. Applicable to nearly all metals less fusible than the solders ; the modes of treatment are nearly similar throughout. The hard solders most commonly used are the spelter solders, and silver solders. The general flux is borax, marked A, on page 334; and the m.odes of heating are the naked fire, the furnace or muffle, and the blow¬ pipe marked a. b. g. Note. —The examples commence with the solders (the least fusible first), followed by the metals for which they are commonly employed. Fine Gold, laminated and cut into shreds, is used as the solder for joining chemical vessels made of platinum. Silver is by many considered as much the best solder for German silver. Copper in shreds, is sometimes similarly used for iron. Gold solders laminated, are used for gold alloys. See 191-193 and 341. Spelter solders granulated whilst hot, are used for iron, copper, brass, gun-metal, German silver, etc., 184, 339-341. Silver solders laminated, are employed for all silver works and for common gold work, also for German silver, gilding metal, iron, steel, brass, gun-metal, etc., when greater neatness is required than is obtained with spelter-solder. 199 and 341. White or button solders granulated, are employed for the white alloys called button metals; they were introduced as cheap substi¬ tutes for silver-solder. 188. SOFT-SOLDERING. 341. Applicable to nearly all the metals; the modes of treatment very different. The soft-solder mostly used, is 2 parts tin and 1 part lead; some¬ times from motives of economy much more lead is employed, and 1| tin to 1 lead is the most fusible of the group unless bismuth is used. The fluxes B to G, and the modes of heating a to i, are all used with the soft-solders. Note. —The examples commence with the metals to be soldered. Thus in the list Zinc, 8, C, f implies, that zinc is soldered with No. 8 alloy, by the aid of the muriate or chloride of zinc, and the copper bit. Lead, 4 to 8, F, d, e, implies that lead is soldered with alloys varying from No. 4 to 8, and that it is fluxed with tallow, the heat being applied by pouring on melted solder, and the subsequent use of the heated iron not tinned; but in general one only of the modes of heatirig is selected, according to circumstances. 334 THE PRACTICAL METAL-WORKER’S ASSISTANT. Iron, cast-iron and steel, 8, B, D, if thick heated by a, b, or c, and also by g. 344. Tinned iron, 8, C, D,/. 342-3. Silver and Gold are soldered with pure tin or else with 8, E, a, g, or h. Copper and many of its alloys, namely, brass, gilding metal, gun- metal, etc., 8, B, C, D; when thick heated by a, b, c, e, or g, and when thin by f or g. 343-5. Speculum metal, 8, B, C, D, the heat should be most cautiously applied, the sand-bath is perhaps the best mode. Zinc, 8, C,/. 344. Lead and lead pipes, or ordinary plumbers’ work, 4 to 8, F, d, or e, 342. Lead and tin pipes, 8, D & G mixed, g, and also /. 345. Brittannia metal, 8, C, D, g. Pewters, the solders must vary in fusibility according to the fusi¬ bility of the metal; generally G and i are used, sometimes also G and g, or /. 345-6. Tinning the metals, and washing them with lead, zinc, etc. 346-7 SOLDERING PER SE, OR BURNING TOGETHER. 347. Applicable to some few of the metals only, and which in general reguire no flux. Iron and brass, etc., are sometimes burned, or united by partial fusion, by pouring very hot metal over or around them, d. 347-9 Lead is united without solder, by pouring on red-hot lead, and employing a red-hot iron, d, e, 347, and also by the autogenous process, page 350. Alloys and their Melting Heats.* 1. 1 Tin, 25 Lead 558 Fahr. 2. 1 — 10 — 541 — 3. 1 — 5 — 611 — 4. 1 — 3 — . 482 — 5. l — 2 — 441 — 6. 1 — 1 — 370 — 7. H — 1 — , 334 — 8. 2 — 1 — . 340 — 9. 3 — 1 — # 356 — 10. 4 — 1 — # 365 — 11. 5 — l — 378 — 12. 6 — 1 — • 881 — 13. 4 Lead, 4 Tin, 1 Bismuth 320 — 14. 3 — 3 — 1 — 310 — 15. 2 — 2 — 1 — 292 — 16. 1 — 1 — 1 — 254 — 17. 2 — 1 — 2 — # 236 — 18. 3 — 5 — 2 — 202 — Note .—By the addition of 3 parts of mer¬ cury to No. 18 it melts at 122° F., and may be used for anatomical injections, and for stopping teeth. Fluxes. A. Borax. 339. B. Sal-ammoniac, or mur. of ammo’a. 343-4. C. Muriate, or chloride of zinc. 344. D. Common resin. E. Venice turpentine. F. Tallow. 342. G. Gallipoli oil, a common sweet oil. 346. Modes op Applying Heat. a. Naked fire. 335-6. b. Hollow furnace or muffle. 335. c. Immersion in melted solder. 344. d. Melted solder or metal poured on. 341-7. e. Heated iron not tinned. 342. f. Heated copper tool, tinned. 342-9. g. Blowpipe flame 336 to 339, 341, 345, 350. h. Flame alone, generally alcohol. ». Stream of heated air. 346. * Tlie table by H. Gaulthier de Claubry, from which the present extract is SOLDERING. 335 The Modes of Applying Heat in Soldering. —The modes of heating works for soldering are extremely varied, and depend jointly upon the magnitude of the objects, the general or local manner in which they are to be soldered, and the fusibility of the solders. It appears to be now desirable to advert to such of the modes of applying heat enumerated in the tabular view, as are of more general application, leaving the modes specifically employed in heating works to their respective sections. In hard-soldered works, the fires bear a general resemblance to those employed in forging iron and steel, and already described; in fact, the blacksmith’s forge is frequently used for brazing, although the process is injurious to the fuel as regards its ordinary use. Coppersmiths, silversmiths, and others, use a similar hearth, but which stands further away from the upright wall, so as to allow of the central parts of large objects being soldered; the blows are always worked by the foot, either by a treadle, as in Fig. 42, p. 93, or more commonly by a chain from the rocking- staff terminating in a stirrup. Some parts of the remarks on forging iron and steel, p. 86 to 94, and also of those on hardening and tempering steel, 147 and 152, refer to similar applications of heat to those required in sol¬ dering. The brazier’s hearth for large and long works, is a flat plate of iron, about four feet by three, which stands in the middle of the shop upon four legs: the surface of the plate serves for the support of long tubes and works over the central aperture in the plate which contains the fuel, and measures about two feet by one, and five or six inches deep. The revolving fan is commonly used for the blast, and the tuyere irons, which have larger apertures than usual, are fitted loosely into grooves at the ends, to admit of eas^ renewal, as they are destroyed rather quickly. The fire is some¬ times used of the full length of the hearth, but is more generally contracted by a loose iron plate; occasionally two separate fires are made, or the two-blast pipes are used upon one. The hood is suspended from the ceiling, with counterpoise weights, so as to be raised or depressed according to the magnitude of the works; and it has large sliding tubes for conducting the smoke to the chimney. Furnaces are occasionally used in soldering, or the common fire is temporarily converted into the condition of a furnace from being built hollow, or by the insertion of iron tubes or muffles, amidst the ignited fuel, as already explained in reference to forging and hardening. For want of any of these means, the amate’ur may use the ordinary grate, or it is better to employ a brazier or chaf- derived, enumerates 102 different alloys intended to be used for the safety plugs of steam boilers, in order that the fusion of the plug, and the conse¬ quent escape of the water, may occur when the steam exceeds any predeter¬ mined pressure, dependent on thermometric temperature. See Le Diction- naire de V Industrie Manufacturere, Commerciale, et Agricole, par A. Baudrimont , Blanqui ain6 et autres. Paris, 1833. Vol. I., p. 323. 336 THE PRACTICAL METAL-WORKER’S ASSISTANT. ing dish containing charcoal, and urged with hand-bellows blown by an assistant, as then both hands are at liberty to manage the work and fuel. Fresh coals are highly improper for soldering, on account of the sulphur they always contain; the best fuel is charcoal, but in gen¬ eral coke or cinders are used. Lead is equally as prejudicial to the fire in soldering, as it is in welding iron and steel, or in forg¬ ing gold, silver, or copper; as the lead readily oxidizes and at¬ taches itself to the metals that are being soldered or welded, pre¬ venting the union of the parts, and in almost all cases rendering the metals brittle and unserviceable. There are many purposes in the arts which require the applica¬ tion of heat, having the intensity of the forge fire or of the furnace, but with the power of observation, guidance, and defini¬ tion of the artist’s pencil. These conditions are most efficiently obtained by the blowpipe, an instrument by which a stream of air is driven forcibly through a flame, so as to direct it either as a well-defined cone, or as a broad jet of flame, against the object to be heated, which is in many cases supported upon charcoal, by way of concentrating the heat. The blowpipe is largely used—namely, in soldering, in harden¬ ing and tempering small tools, in glass-blowing for philosophical instruments and toys, in glass-pinching with metal moulds made like pliers, in enameling, and by the chemist and mineralogist, as an important means of analysis ; the instrument has consequently received very great attention both from artisans and distinguished philosophers. Most of the blowpipes are supplied with common air, and gen erally by the respiratory organs of the operator; sometimes by bellows moved with the foot, by vessels in which the air is con¬ densed by a syringe, or by pneumatic apparatus with water pres¬ sure. In some few cases oxygen or hydrogen, or the same gases when mixed are employed; they are little used in the arts. The ordinary blowpipe is a light conical brass tube, about 10 or 12 inches long, from one-half to one-fourth of an inch diameter at the end for the mouth, and from one-sixteenth to one-fiftieth at the aperture or jet; the end is bent as a quadrant, that the flame may be immediately under observation. Fig. 290 represents the same instrument when fitted with a ball for collecting the condensed vapor from the lungs; it is seen by the enlarged section, Fig. 291, that the tube is discontinuous, and any moisture within it, proceeding in the direction of the arrow, is arrested in the ball. There are several other blowpipes for the mouth, with various contrivances, such as a series of apertures of different diameters, joints for portability, and for placing the jet at different angles, and projecting parts to support the instrument upon the table; but none of these are in common use. The lungs may be used for the blowpipe with much more effect than might be expected, and with a little practice a constant stream SOLDERING. 337 may be maintained for many minutes, if the cheeks are kept fully distended with wind, so that their elasticity alone shall serve to impel a part of the air, whilst the ordinary breathing is carried on through the nostrils for a fresh supply. The most intense heat of the common blowpipe is that of the pointed flame; with a thick wax candle, and a blowpipe with a small aperture placed slightly within the flame, the mineralogist succeeds in melting small fragments of all the metals, when they are supported upon charcoal and exposed to the extreme point of the inner or blue cone, which is the hottest part of the flame ; that is, fragments of all metals which do not require the oxhydrogen blowpipe invented by Dr. Hare of Philadelphia. Larger particles, requiring less heat, are brought somewhat nearer to the candle, so as to receive a greater portion of the flame ; and when a very mild degree of heat is needed, the object is re¬ moved further away, sometimes, as in melting the fluxes prepara¬ tory to soldering, even to the stream of hot air beyond the point of the external yellowish flame. The first, or the silent pointed flame, is used by the chemist and mineralogist for reducing the metallic oxides to the metallic state, and is called the deoxidizing flame; the second, or the noisy brush- like flame, is less intense, and is called the oxidizing flame. The artizan employs in soldering a much larger flame than the chemist, namely, that of a lamp the wick of which is from a quarter to one inch diameter; this must be plentifully supplied with oil; the blowpipe in such cases is selected with a large aperture; it is blown vigorously, and held a little distant from the flame, so as to spread it in a broad stream of light, extending over a large surface of the work, which is in most cases supported upon charcoal. When any minute portion alone is to be heated, the pointed flame is used with a milder blast of air and a decreased distance. Figs. 290 292 293 u Fig. 292 is an arrangement, the use of which is attended with no fatigue to the operator. A stream of air from a pair of bellows directs a gas flame through a trough or shoot, the third of a cylin¬ drical tube placed at a small angle below the flame. Instead of a 22 338 THE PRACTICAL METAL-WORKER’S ASSISTANT. charcoal support, they employ a wooden handle, upon which is fixed a flat disk of sheet-iron, about three or four inches diameter, covered with a matting of waste fragments of binding wire, entangled to¬ gether and beaten into a sheet, about three-eighths or half an inch thick; some few of the larger pieces of wire extend round the edge of the disk to attach the remainder. The work to be soldered is placed upon the wire, which becomes partially red-hot from the flame, and retains the heat somewhat as the charcoal, but without the inconvenience of burning away, so that the broad level surface is always maintained. Small cinders are frequently placed upon the tool, either instead of, or upon the wire. Sometimes, as in Fig. 293, the gas pipe is surmounted by a square hood, open at both ends, and two blast-pipes are directed through it; the latter arrangement is used by the makers of glass toys and seals; these are pinched in moulds something like bullet- moulds ; the devices on the seals are produced by inserting in the moulds dried casts, made in plaster of Paris. Makers of thermometers and other philosophical instruments generally use a table blowpipe, with a shallow oval, or rather a kidney-shaped lamp, Fig. 294, with a loop placed lengthways upon the short diameter for holding the cotton, which is sometimes an inch long and half an inch wide. The wick is plentifully supplied with tallow or hog’s lard, and a furrow is made through it with a wire to afford a free passage for the blast from the fixed nozzle, by the size of which, and its distance from the flame, the latter is made to assume the pointed or brush-like character. This lamp is more cleanly, and emits less smell than those supplied with oil; any overflow of the tallow is caught in the outer vessel or tray, and when cold, the fat solidifies. The forge, Fig. 42, page 93, has also a blowpipe and lamp to enable it to be applied to the arts in a similar manner, and a very cheap table blowpipe is described by Dr. Michael Faraday, in his “Chemical Manipulation,” page 120-169. Many blowpipes have been invented for the employment of oxygen and hydrogen; the mixed gases were first used by Dr. Hare, of Philadelphia, who has been followed in various wavs by many others. The construction and management of. nearly all the blowpipes are described in Dr. Faraday’s “Chemical Manipula¬ tion,” 1830, pages 107 to 123. Also in “A Practical Treatise on the Use of the Blowpipe,” by his talented countryman, Dr. Sheridan Muspratt, now of Liverpool, but formerly of Dublin. Two subse¬ quent modifications of gas blowpipes which have been invented for the workshop, will alone be here described, namely, the Workshop Blowpipe, intended for soldering, hardening, and other purposes; and the Count de Richemont’s Airo-hydrogen Blowpipe. The general form of the “workshop blowpipe” is that of a tube open at the one end, and supported on trunnions in a wooden pedestal, so that it may be pointed vertically, horizontally, or at any angle as desired. Common street gas is supplied through the one hollow trunnion, and it escapes through an annular open- SOLDERING. 339 mg; whilst oxygen gas, or more usually common air, is admitted through the other trunnion which is also hollow, and is discharged in the centre of the hydrogen through a central conical tube; the magnitude and intensity of the flame being determined by the rela¬ tive quantities' of gas and air, and by the greater or less protru¬ sion of the inner cone, by which the annular space for the hydro¬ gen is contracted in any required degree. From amongst numerous other small applications of heat, a port¬ able blowpipe furnace may be noticed; it consists of a lump of pumice-stone three or four inches diameter, scooped out like a pan or crucible, and filled with small fragments of charcoal; sometimes a conical perforated cover is added: the inside may be intensely ignited, whilst the slow conducting power of the pumice-stone guards the hand from inconvenient heat. Examples of Hard Soldering. —It was mentioned in the tabular view that the several works united with hard-solders receive nearly the same treatment; a few examples will therefore serve to convey a general idea of hard-soldering; a process commonly attended with some risk of partially melting the works, because the fusing points of the metals and their respective solders often approach very nearly together. Several of the hard solders contain zinc, which appears to be useful in different ways: first it increases their fusibility; in cases where the solder cannot be seen it serves as an index to denote the completion of the process, for when the solder is melted the zinc volatilizes, and burns with the well-known blue flame; and as at this moment some of the zinc is consumed, the alloy left behind becomes tougher, and more nearly approaches to the condition of the metal which it is desired to unite. The zinc may be therefore con¬ sidered to act as a flux, and so likewise does the arsenic occasionally introduced into the gold and silver solders, as the arsenic is for the most part lost, between the processes of making and using the solders; but this metal being of a noxious quality, it is but little resorted to, and besides, it renders the other metals very brittle. In every case of soldering, a general regard to cleanliness in the manipulation is important, and for the most part the edges of the metals are filed or scraped prior to their being soldered, as before observed; in those cases in which the red-heat is employed, filing or scraping are less imperative, as any greasy or combustible mat¬ ters are burned away, and the borax has the property of combin¬ ing with nearly all the metallic oxides and earthy bases, thereby cleansing the edges of the metals should that proceeding have been previously omitted. The works in copper, iron, brass, etc., having been prepared for brazing (or soldering with a fusible brass), and the joints secured in position by binding wire where needful, the granulated spelter and pounded borax are mixed in a cup with a very little water, and spread along the joint by a slip of sheet metal or a small spoon. 840 THE PRACTICAL METAL-WORKER’S ASSISTANT. The -work, if sufficiently large, is now placed above the clear fire, first at a small distance so as gradually to evaporate the mois¬ ture, and likewise to drive off the water of crystallization of the borax; during this process the latter boils up with the appearance of froth or snow, and if hastily heated it sometimes displaces the solder. The heat is now increased, and when the metal becomes faintly red, the borax fuses quietly like a glass; shortly after, that is at a bright red, the solder also fuses, the indication of which is a small blue flame from the ignition of the zinc. Just at this time some works are tapped slightly with the poker to put the whole in vibration, and cause the solder to run through the joint to the lower surface, but generally the solder flushes, or is absorbed in the joint, and nearly disappears without the necessity for tapping the work. It is of course necessary to apply the heat as uniformly as possi¬ ble, by moving the w r ork about so as to avoid melting the object as well as the solder; the work is withdrawn from the fire as soon as the solder has flushed, and when the latter is set, the work may be cooled in water without mischief. Tubes are generally secured by loops of binding wire twisted to¬ gether with the pliers; and those soldered upon the open fire are almost always soldered from within, as otherwise the heat would have to be transmitted across the tube with greater risk of melting the work, air being a bad conductor of heat; it is necessary to look through the tube to watch for the melting of the solder. Long tubes are rested upon the flat plate of the brazier’s hearth, and portions equal to the extent of the fire are soldered in succession. The com¬ mon tubes for gas-works, bedsteads, and numerous other purposes, are soldered from the outside; but this is done in short furnaces open at both ends and level with the floor, by which the heat is applied more uniformly around the tubes. Works in iron require much less precaution in point of the heat, as there is little or no risk of fusion; thus in soldering the spiral wires to form the internal screw within the boxes of ordinary tail vices, the work is coated with loam, and strips of sheet brass are used as solder; the fire is urged until the blue flame appears at the end of the tube, when the fusion is complete; the work is with¬ drawn from the fire and rolled backwards and forwards on the ground to distribute the solder equally at every part. Other com¬ mon works in iron, such as locks, are in like manner covered with loam to prevent the iron from scaling off. Sheet iron may be soldered by filings of soft cast-iron, applied in the usual way of soldering with borax, which has been gradually dried in a crucible and powdered, and a solution of sal-ammoniac. The finer works in iron and steel, those in the light-colored metals generally, and also the works in brass which are required to be very neatly done, are soldered with silver-solder. From the superior fusibility of silver-solder, and from its combining so well with the different metals without, “gnawing them or eating them SOLDERING. 341 away,' 1 ' 1 or wasting part of the edges of the joints, silver-solder is very desirable for a great many cases; and from the more careful and sparing manner in which it is used, many objects require but little or no finishing subsequently to the soldering, so that the more expensive solder is not only better, but likewise in reality more economical. The practice of silver-soldering is essentially the same as brazing. The joint is first moistened with borax and water; the solder (which is generally laminated and cut into little squares with the shears) is then placed on the joint with forceps. In heating the work additional care is given not to displace the solder; and for which reason some persons boil the borax, or drive off its water of crystallization at the red heat, then pulverize it and apply it in the dry state along with the solder; others fuse the borax upon the joint before putting on the solder. Numerous small works united with the hard-solders, such as mathematical and drawing instruments, buttons, and jewelry, are soldered with the blowpipe; in almost all cases the work is sup¬ ported upon charcoal, and sometimes for the greater concentration of the heat it is also covered with charcoal. The management of the blowpipe having been explained, it is only necessary to add that the magnitude and shape of the flame are proportioned to those of the works. In soldering gold and silver, the borax is rubbed with water upon a slate to the consistence of cream, and is laid upon the work with a camel’s-hair pencil, and the solders, although generally lam¬ inated, are also drawn into wire, or filed into dust; but it will be remembered the more minute the particles of the granulated metals, the greater is the degree of heat required in fusing them. In many of the jewelry works the solder is so delicately applied that it is not necessary to file or scrape off any portion, none being in excess, and the borax is removed by immersing the works in the various pickling and coloring preparations to be adverted to. Examples of Soft-soldering. —The plumbers’ sealed-solder, 2 parts lead and 1 of tin, melts at about 440° F.; the usual or fine tin-solder, 2 parts tin and 1 of lead, melts at 340°; and the bismuth- solders at from 250° to 270°: the modes of applying the heat con¬ sequently differ very much, as will be shown. The soft-solders are prepared in different forms suited to the na¬ ture of the various works; No. 5, p. 834, the plumbers’-solder, is cast in iron moulds into triangular ingots measuring from 140 6 superficial inches in the section. No. 8, the fine tin solder, is cast in cakes about 4 by 6 inches, and ^ to \ inch thick; and this and the more fusible kinds, are trailed from the ladle upon an iron plate or flat stone, to make slight bars, ribbons, and even threads, that the magnitude of the solder may be always proportioned to the magnitude and circumstances of the work. It is very essential that all soft-soldered joints should be particu¬ larly clean and free from metallic oxides; and, except where oil is 342 THE PRACTICAL METAL-WORKER’S ASSISTANT. exclusively used as the flux, greasy matters should be avoided, aa they prevent the ready attachment of the aqueous fluxes. It is therefore usual with all the metals, except clean tinned plate, and clean tin alloys, to scrape the edges immediately before the process, so far as the solder is desired to adhere. Lead works are first smeared or soiled around the intended joints, with a mixture of size and lamp-black, called soil, to prevent the adhesion of the melted solder; next the parts intended to receive the solder are scraped quite clean with the shave-hook (a triangular disk of steel riveted on a wire stem), and the clean metal is then rubbed over with tallow. Some joints are wiped, without the em¬ ployment of the soldering iron: that is, the solder is heated rather beyond its melting point, and poured somewhat plentifully upon the joint to heat it; the solder is then smoothed with the cloth, or several folds of thick bed-tick well greased, with which the superfluous solder is finally removed. Other lead joints are striped, or left in ridges, from the bulbous end of the plumber’s crooked soldering-iron, which is heated nearly to redness, and not tinned; the iron and cloth are jointly used at the commencement, for moulding the solder and heating the joint. In this case less solder is poured on, and a smaller quantity remains upon the work ; and although the striped-joints are less neat in ap¬ pearance, they are by many considered sounder from the solder having been left undisturbed in the act of cooling. The vertical joints, and those for pipes, whether finished with the cloth or iron, require the cloth to support the fluid solder when it is poured on the lead. Slight works in lead, such as lattices, requiring more neatness than ordinary plumbing, are soldered with the copper-hit or copper- holt represented in Figs. 297 and 298; they are pieces of copper Aveighing from three or four ounces to as many pounds, riveted into iron shanks and fitted with wooden handles. All the works in tinned iron, sheet zinc, and many of those in copper and other thin metals, are soldered with this tool, frequently misnamed a soldering-Aon, which in general suffices to convey all the heat required to melt the more fusible solders now employed. Figs. 295 297 If the copper-bit have not been previously tinned, it is heated in a small charcoal stove or otherwise to a dull red, and hastilv filed SOLDERING. 343 to a clean metallic surface ; it is then rubbed immediately, first upon a lump of sal-ammoniac, and next upon a copper or tin plate, upon which a few drops of solder have been placed; this will com¬ pletely coat the tool; it is then wiped clean with a piece of tow, and is ready for use. In soldering coarse works, when their edges are brought together, they are slightly strewed with powdered resin contained in the box, Fig. 296, or it is spread on the work with a small spoon; the cop¬ per-bit is held in the right hand, the cake of solder in the left, and a few drops of the latter are melted along the joint at short intervals. The iron is-then used to heat the edges of the metal, both to fuse and to distribute the solder along the joint, so as to entirely fill up the interval between the two parts; only, a short portion of the joint, rarely exceeding six or eight inches, is done at once. Some¬ times the parts are held in contact with a broad chisel-formed tool, or a hatchet-stake, whilst the solder is melted and cooled, or a few distant parts are first tacked together or united by a drop of solder but mostly the hands alone suffice, without the tacking. Two soldering tools are generally used, so that whilst the one is in the hand, the other may be reheating in the stove; the tempera¬ ture of the bit is very important; if it be not hot enough to raise the edges of the metal to the melting heat of the solder, it must be returned to the fire; but, unless by mismanagement it is made too hot and the coating is burned off, the process of tinning the bit need not be repeated, it is simply wiped on tow, on removal from the fire. If the tool be overheated, it will make the solder un¬ necessarily fluid, and entirely prevent the main purpose of the copper-hit, which is intended to act both as a heating tool, and as a brush, first to pick up a small quantity or drop from the cake of solder which is fixed upright in the tray, Fig. 295, and then to distribute it along the edge of the joint. The tool is sometimes passed only once slowly along the work, being guided in contact with the fold or ledge of the metal. This supposes the operator to possess that dexterity of hand, which is abundantly exhibited in many of the best tin wares; in these the line of solder is very fine and regular. The soldering-tool is then thin and keen on the edge, and the flux, instead of being resin, is mostly the muriate of zinc, with which the joint is moistened by means of a small wire or a stick prior to the application of the heated tool; sometimes the workman cools the part just finished, by blowing upon it as the bit proceeds in its course; and the iron, if overheated, is cooled upon a moistened rag placed in the empty space of the tray containing the solder. Copper works are more commonly fluxed with powdered sal ammoniac, and so is likewise sheet-iron, although some mix pow¬ dered resin and sal-ammoniac, others moisten the edges of the work with a saturated solution of sal-ammoniac, using a piece of cane the end of which is split into filaments to make a stubby brush, and they subsequently apply resin; each method has its advocates, but 344 THE PRACTICAL METAL-WORKER’S ASSISTANT. so long as the metals are well defended from oxidation any mode will suffice, and in general management the processes are the same. Zinc is more difficult to solder than the other metals, and the joints are not generally so neatly executed; the zinc seems to re¬ move the coating of tin from the copper soldering-tool; this prob¬ ably arises from the superior affinity of copper for zinc than for tin. The flux sometimes used for zinc is sal-ammoniac, but the muriate of zinc, made by dissolving fragments of zinc in muriatic acid diluted with about an equal quantity of water, is much supe¬ rior ; and the muriate of zinc serves admirably likewise for all the other metals, without such strict necessity for clean surfaces as when the other fluxes are used. The copper tool is only applicable to thin metals, because it re¬ quires such a degree of heat as will allow it to raise the temperature of the work to be joined, to the melting point of the solder; and the excess of heat thus required for stout metals, is apt, either to burn off the coating of solder, or to cause it to be absorbed as a process of superficial alloying. It requires some tact to keep the heat of the tool within proper limits by means of the charcoal or cinder fire, but with the airo-hydrogen blowpipe, explained at page 350-2, it is easy to maintain any required temperature for an indefinite period. Thicker pieces of metal, such as the parts of philosophical ap¬ paratus, gas-fittings, and others which cannot be conveniently managed with the copper-bit, are first prepared by filling or turn¬ ing, and each piece is then separately tinned in one of the follow¬ ing ways. Small pieces, immediately after being cleaned with the file or other tool, and without being touched with the fingers, are dipped into a ladle containing melted solder, which is covered with a little powdered sal-ammoniac. The flux meets the work before it is subjected to the heat, and the tinning is then readily done; sometimes the work is in the first instance sprinkled with resin, or rubbed over with sal-ammoniac water; the latter is rather a dangerous practice, as the moisture is apt to drive the melted metal in the face of the operator. Thin pieces of brass or of copper alloys, if submitted to this method, must be quickly dipped, or there is risk of their being attacked and partly dissolved by the solder. There is some little uncertainty as to iron, and especially as to steel, being well coated by dipping; sometimes a forcible jar or a hard rub will remove most of the tin, and it is therefore safer to rub these works with a piece of heated copper shaped like a file, immediately on their removal from the melted solder, which makes the adhesion more certain. Larger pieces of metal, or those it is inconvenient to dip into the ladle, are first moistened with sal-ammoniac water, or dusted with the dry powder or resin, and heated on a clear fire either of char¬ coal, coke, or cinders, until the strip of solder held against them is melted and adheres; as the lowest heat should be always used. SOLDERING. 345 Another cleanly way of applying the heat, and which is also em¬ ployed in tempering tools, varnishing, and cementing, is to make red-hot a few inches of the end of a flat iron bar about two feet long, to pinch it in the vice by the cold part, and to lay the work upon that spot which is at a suitable temperature ; the work can be thus very conveniently managed, especially as it may be like¬ wise placed in a good light. Until the two parts of the work are thoroughly tinned, they must be well defended from the air by the flux to prevent oxida¬ tion ; they are next made a trifle hotter than is required for tin¬ ning, and placed in contact whilst the solder is quite fluid, and a little additional solder is also used; when practicable, the two sur¬ faces are rubbed together to perfect the tinning and spread the alloy evenly through the joint; the work is then allowed to cool under pressure applied by the hammer handle, the blunt end of a tool, the tail-vice, or in any convenient manner. The stages of this practice are similar to those of the carpenter, who having brushed the glue over the two pieces of wood, rubs them together and fixes them with the hand screws until cold, as before ad¬ verted to. Small works are sometimes united by cleaning the respective surfaces, moistening them with sal-ammoniac water, or applying the dry powder or resin, then placing between the pieces a slip of tin-foil, previously cleaned with emory-paper, and pinching the whole between a pair of heated tongs to melt the foil; or, other similar modifications combining heat and pressure are used. Many workmen who are accustomed to the blowpipe, as jewel¬ ers, mathematical instrument makers, and others, apply the blow¬ pipe with great success in soft-soldering; but as the methods are in other respects similar to those given, they do not require partic¬ ular notice, except that in some cases there is no choice but to tie the works together with binding-wire as in hard-soldering; but the preference is always given to detached tinning and rubbing together. The modern gas-fitters are remarkably expert in joining tin and lead pipes with the blowpipe; they do not employ the method of the plumbers and pewterers, or the spigot and faucet joint sur¬ rounded by a bulb of solder, but they cut off the ends of the pipes with a saw, and file the surfaces to meet in butt joints, in mitres, or in T form joints as required. In confined situations they apply the heat from one side only with the blowpipe and rushes; they employ a rich tin solder, with oil and resin mixed in equal parts as the flux; the work looks like carpentry rather than soldering. The pewterers employ a very peculiar modification of the blow¬ pipe, which may be called the hot-air blast, and the names for which apparatus are no less peculiar; a, Fig. 299, being called the hod, and b, the gentleman. The first is a common cast-iron pot with a close cover, containing ignited charcoal; two nozzles leading respectively into and from it, to allow the passage of a stream of 346 THE PRACTICAL METAL-WORKERS ASSISTANT. air, through the pipe c, from bellows worked bj the foot. The pew ter wares, many of which are circular, are placed on the gentleman, or a revolving pedestal, which may be adjusted by the side screw to any height: the workmen dip the strip of solder in a little pot of oil, and apply it to the joint with the right hand, whilst they slowly revolve the work with the left. This, which is a very controllable application of heat, includes in its range a moderately large extent of the pewterer’s work, and answers the purpose extremely well: by some, the rushes and mouth blowpipe are used for circular as well as for other articles in pewter. The pewters bear nearly the proportion of the alloys Nos. 8 to 12, page 334: for the less fusible containing most tin, the solder No. 8, or 2 tin 1 lead, is used; for the more fusible containing most lead, the bismuth solders, 2 tin 1 lead 1 bismuth, and others of similar low degrees of fusibility, are employed. The first solder is called by the pewterers hard-pale, the last soft-pale, and to suit the pewters of intermediate degrees of fusibility, the two are mixed in variable proportions and called middling-pale; but the table on page 334, and especially the original from which the 18 terms there given are extracted, would enable the solders to be definitely proportioned to their respective metals. The flux always used by the pewterers is Gallipoli oil; it is a second rate olive oil, of peculiar quality, rather thick, green, and unfit for the table; but its selection requires judgment. Iron, copper, and alloys of the latter metal, are frequently coated with tin, and occasionally with lead and zinc, to present surfaces less subject to oxidation; gilding and silvering are partly adopted from similar motives. As regards iron, the method of making the tinned plate is strictly a manufacturing process, which has been slightly noticed at page 200, and that of covering iron with zinc, so that it principally remains to describe the ordinary method of tinning vessels and other objects of copper, brass, and iron, after they have been manufactured, and which is in general thus performed. Copper and brass vessels are first pickled with sulphuric acid, mostly diluted with about three times its bulk of water; they are Oien scrubbed with sand and water, washed clean and dried; they are next sprinkled with dry sal-ammoniac in powder, and heated slightly over the fire; then a small quantity of melted block-tin is thrown in, the vessel is swung and twisted about to apply the tin on all sides, and when it has well adhered the portion in excess is returned to the ladle, and the object is cooled in water. When cleverly performed very little tin is taken up, and the surface looks almost as bright as silver; some objects require to be dipped into a ladle lull of tin Fig. 299. SOLDERING. 347 Iron presents rather more difficulty, the affinity of the tin being less strong for iron than for copper; but the treatment is in gen¬ eral nearly the same. Old works require that the grease should be removed with concentrated muriatic acid, before the other pro¬ cesses are commenced; and in cast-iron vessels the grease often penetrates so deeply, owing to the porous nature of the metal, that the re-tinning is sometimes scarcely possible, and it is often more economical to obtain a new vessel. An alloy of nickel, iron, and tin, has been introduced as an improvement in tinning the metals. The nickel and tin compound is harder than tin, and endures a much longer time: it is less fusi¬ ble, and will not run or melt at a heat that would cause the ordi¬ nary tinning of pans to forsake the sides and lie in a mass at the bottom. Also that as an experiment to show the tenacity of the nickel, a piece of cast-iron tinned with the compound, had been subjected for a few minutes to the white heat under a blast, and although the tin was consumed, the nickel remained as a perma¬ nent coating upon the iron. The proportions of nickel and iron mixed with the tin in order to produce the best tinning, are ten ounces of the best nickel, and seven ounces of sheet-iron, to ten pounds of tin. These metals are Inixed in a crucible, and, to prevent the oxidation of the tin by the high temperature necessary for the fusion of the nickel, the metals are covered with one ounce of borax and three ounces of pounded glass. The fusion is completed in about half an hour, when the composition is run off through a hole made in the flux. In tinning metals with this composition the workman proceeds in the ordinary manner. The process was discovered by M. Budie, of the firm of Blaise and Co., Paris. There is also another method, that of cold-tinning, by aid of the amalgam of mercury, described at page 217; but this process when applied to utensils employed for preparing or receiving food, appears questionable both as regards effectiveness, and wholesome¬ ness, and the activity of the muriatic acid must not be forgotten; it should be therefore washed carefully off with water. The tin adheres, however, sufficiently well to allow other pieces of metal to be afterwards attached by the ordinary copper soldering-bit. Soldering per se, or Burning together. —This principally differs from ordinary soldering, in the circumstances that the unit¬ ing or intermediate metal is the same as those to be joined, and that in general no fluxes are employed. The method of burning together, although it only admits of limited application, is in many cases of great importance, as when successfully performed the works assume the condition of greatest strength, from all parts being alike. There is no dissimilarity be¬ tween the several parts as when ordinary solders are used, which are open to an objection, that the solders expand and contract by heat either more or less than the metals to which they are attached. There is another objection of far greater moment; the solders 848 THE PRACTICAL METAL-WORKER’S ASSISTANT. oxidize either more or less freely than the metals, and upon which circumstances hinge some galvanic or electrical phenomena; and thence the soldered joints constitute galvanic circuits, which in some cases cause the more oxidizable of the two metals to waste with the greater rapidity, especially when heat, moisture, or acids are present. In chemical works this is a most serious inconvenience, and therefore, leaden vessels and chambers for sulphuric acid must not be soldered with tin-solder, the tin being so much more freely dis¬ solved than the lead. Such works were formerly burned together by pouring red-hot lead on the joint, and fusing the parts into one mass, by means of a red-hot soldering-iron, as noticed at page 294 ; this is troublesome and tedious, and it is now replaced by the auto¬ genous soldering, to be explained. Pewter is sometimes burned together at the external angles of works, simply that no difference of color may exist; the one edge is allowed to stand a little above the other, as in Fig. 213, page 292, a strip of the same pewter is laid in the angle, and the whole are melted together, with a large copper-bit, Fig. 297, page 342, heated almost to redness; the superfluous metal is then filed off, leaving a well-defined angle without any visible joint. Brass is likewise burned together ; for instance the rims of large mural circles for observatories, that are five, six or seven feet diameter, are sometimes cast in six or more segments, and attached by burning. The ends of the segments are filed clean, two pieces are fixed vertically in a sand mould in their relative positions, a shallow space is left round the joint, and the entire charge of a crucible, say thirty or forty pounds of the melted brass a little hotter than usual, is then poured on the joint to heat it to the melting point. The metal overflows the shallow chamber or hole, and runs into a pit prepared for it in the sand; but the last quan¬ tity of metal that remains solidifies with the ends of the segments, and forms a joint almost or quite as perfect as the general sub¬ stance of the metal; the process is repeated for every joint of the circle. The compensation balance of the chronometer and superior watches is an interesting example of natural soldering. The balance is a small fly-wheel made of one piece of steel, covered with a hoop of brass. The rim, consisting of the two metals, is divided at the two extremities of the one diametrical arm of the balance, so that the increase of temperature which weakens the balance-spring contracts in a proportionate degree the diameter of the balance, leaving the spring less resistance to overcome. This occurs from the brass expanding much more by heat than steel, and it therefore curls the semicircular arcs inwards, an action that will be immediately understood if we conceive the compound bar of brass and steel to be straight, as the heat would render the brass side longer and convex, and in the balance it renders it more curved. SOLDERING. 349 In the' compensation balance the two metals are thus united : the disk of steel when turned and pierced with a central hole, is fixed by a little screw-bolt and nut at the bottom of a small cruci¬ ble with a central elevation, smaller than the disk ; the brass is now melted, and the whole allowed to cool. The crucible is broken, the excess of brass is turned off in the lathe, the arms are made with the file as usual, the rim is tapped to receive the compensa¬ tion screws or weights, and lastly the hoop is divided in two places, at opposite ends of its diametrical arm. A little black lead is generally introduced between the steel and the crucible; and other but less exact modes of combining the metals are also employed. Cast-iron is likewise united by burning, as will be explained by the following example: To add a flange to an iron pipe, a sand mould is made from a wood model of the required pipe, but the gusset or chamfered band between the flange and tube is made rather fuller than usual to afford a little extra base for the flange. The mould is furnished with an ingate, entering exactly on the horizontal parting of the mould at the end of the flange, and with a waste head or runner proceeding upwards from the top of the flange, and leading over the edge of the flask to a hollow or pit sunk in the sand of the floor. The end of the pipe is filed quite clean at the place of junction, and a shallow nick is filed at the inner edge to assist in keying on the flange ; lastly, the pipe is plugged with sand laid in the mould. After the mould is closed, about six or eight times as much hot metal as the flange requires is poured through the mould. This heats the pipe to the temperature of the fluid iron, so that on cool¬ ing the flange is attached sufficiently firm to bear the ordinary pressure of screw-bolts, steam, etc. Steam and, water-tight joints, in cast-iron works not requiring the power of after-separation, are often made by means of iron cement in the following proportions : 112 lbs. of cast-iron filings or borings, 1 lb. of sal-ammoniac, 1 lb. of sulphur, and 4 lbs. of whitening. Small quantities of the materials are mixed together with a little water shortly before use. For minute cracks the cement is laid on externally as a thin seam, or for larger spaces it is driven in with calking-irons. The edges of the metal and the cement shortly commence one com¬ mon process of rusting, and at the end of a week or ten days the joints will be found hard, dry, and permanent. The method of burning is occasionally employed in most of the metals and alloys in making small additions to old castings, and also in repairing trifling holes and defects in new ones; it is only successful, however, when the pieces are filed quite clean, and abundance of fluid metal is employed, in order to impart sufficient heat to make a natural soldering—a process which is also, although differently accomplished, in plating copper with silver (page 198), as the two metals are raised to a heat just short of the melting 350 THE PRACTICAL METAL-WORKERS ASSISTANT. point of the silver, and the metals then unite without solder by partial alloying. To conclude the description of soldering processes, we have to refer to Fig. 300, -which represents the airo-hydrogen blowpipe in- Fig. 300. vented in France by the Count de Richemont. It is in a great measure converting the oxy-hydrogen blowpipe, invented by Dr. Hare, to the service of the workshop, and it is done with great simplicity and safety. The elastic tube h supplies hydrogen from the generator, and the pipe a supplies atmospheric air from a small pair of double bellows b, worked by the foot of the operator, and compressed by a constant weight w • the two pipes meet at the arch, and proceed through the third pipe e to the small jet /, from whence proceeds the flame. All the connections are by elastic tubes, which allow perfect freedom of motion, so that the portable blowpipe is carried to the work. In soldering by the autogenous process, the works are first pre¬ pared and scraped clean as usual, the hydrogen is ignited, and the size of the flame is proportioned by the stop-cock /i; the air is then admitted through a, until the flame assumes a fine pointed character, with which the work is united after the general method of blowpipe soldering, except that a strip of lead is used instead of solder, and generally without any flux. This mode is described as being suitable to most of the metals, but its best application appears to be to plumbers’ work, and it has been adopted for such in our government dock-yards. The weight of lead consumed in making the joints is a mere fraction of the weight of ordinary solder, which is both more expensive and more oxidizable, from the tin it contains. The gas soldering, as it is called, removes likewise the risk of accidents from the plumbers’ fires, as the gas generator, which is in itself harmless, may be allowed to remain on the ground whilst the workman ascends to the roof, or elsewhere, with the pipe. SOLDERING. 351 Lead is interposed as solder in uniting zinc to zinc, and it is also used in soldering the brass nozzles and cocks to the vessels of lead, and those of copper coated with lead, used as generators. Another Fig. 301. very practical application of the gas flame, is for keeping the cop¬ per soldering tool, Fig. 301, at one temperature, which is done by leading the mixed gases through a tube in the handle, so that the flame plays on the back of the copper bit. This mode seems to be very well adapted to tin-plate and zinc works, especially as the common street gas may be used, thereby dispensing with the neces¬ sity for the gas generator, the construction and management of which alone remain to be explained. The gas generator, Fig. 300, when it is first charged, the stopper 1, is unscrewed, and the lower chamber is nearly filled with curly shreds of sheet zinc, and the stopper is replaced. The cover is now removed, and a plug with a long wire is inserted from the top into the hole near 3 ; the upper chamber is next filled with dilute sulphuric acid (1 acid and 6 water), until it is just seen through the central hole to rise above the plate immediately beneath it. This measures the quantity of liquid required to charge the vessel without the risk of overflow. The plug is now withdrawn from 3, and the cocks 4, and h, being opened, the air escapes from the lower vessel by the pressure of the column of water which enters beneath the perforated bottom 5, upon which the zinc rests. The cocks 4 and h are now closed, and by the decomposition of the water hydrogen is generated, which occupies the upper part of the lower chamber, and drives the dilute acid upwards, through the aperture 3, so as to place matters in the position of the engraving, which represents the generator about two-thirds filled with gas. The gas issues through the pipe h, when both cocks are opened, but it has to proceed through a safety box 6, in which the syphon tube dips two or three inches into a little plain water introduced at the lateral aperture 7; by this precaution the contents of the gasometer cannot be ignited, as, should the flame return through the pipe h, it would be intercepted by the water in the safety box. After three or four days’ constant work the liquid becomes con¬ verted into the sulphate of zinc, and is withdrawn through the plug 8 ; the vessel is then refilled with fresh dilute acid as already explained, but the zinc lasts a considerable time. The generators are made of lead, or where portability and light¬ ness are required, of copper washed with lead, and all the exposed parts of the brass work are washed and united with lead to defend 352 TITE PRACTICAL METAL-WORKER’S ASSISTANT. them from the acid. Occasionally the air is likewise supplied by aerometers, or vessels somewhat resembling the gas generator, but which are only filled with common air, and therefore do not require the zinc or acid. The following is the broad difference between the airo-hydrogen and the oxy-hydrogen blowpipes. In the oxy-hydrogen blowpipe, the pure gases are mixed in the exact proportions of two volumes of hydrogen to one of oxygen, which quantities when combined constitute water, and in this particular case there is the greatest condensation of volume, and the greatest evolution of latent as well as of sensible heat. The airo-hydrogen blowpipe is supplied with common air and with pure hydrogen; this instrument is also the most effective when the oxygen and hydrogen are mixed in the proportions of 1 to 2; but the nitrogen, which constitutes four-fifths of our atmos¬ phere, is now in the way and detracts from the intensity of the effect. CHAPTER XX SHEARS. Cutting Nippers for Wires. —Shears are instruments of a character quite different from any of those hitherto described, as the cutting edges of shearing tools are always used in pairs, and on opposite sides of the material to be sheared or severed. In many cases the shears are constructed after the manner of pincers and pliers, or as two double-ended levers united at the fulcrum by a pin, but other modes of uniting the two cutting parts of the in¬ struments are also employed, as will be shown. The sections of some varieties of this Fig. 302. instrument are represented by a b c of the annexed Fig. 302, from which it will be seen that the edges of shears and fir scissors meet in lateral contact, and pass . N _ . -f close against one another, severing the ;'j yH k material by two cuts or indentations, or b PH d thrusts, which take place in the same C plane as that in which the blades are situated and are moved. Some of the largest shearing tools of the kinds used by en¬ gineers, such as c, serve to divide bars of iron, 4, 5 or 6 inches wide, and 1 to 2 inches thick, then requiring the greatest possible solidity and freedom from elasticity. On the other hand, some of the finest scissors of the section a, such as are used by ladies in cutting lace, will cut with the greatest SHEARS. 353 cleanness and perfection the most flexible thread or tissue of threads, or the finest membranes met with in animal or vegetable structures. But this latter kind of shears, unlike the engineer’s shears, is altogether useless unless possessed of a considerable share of elas¬ ticity, to keep their edges in accurate contact at that point in which the blades at the moment cross each other, as will be explained, otherwise such thin materials are folded down between the blades instead of being fairly cut. The transition from the elastic to the inelastic kinds of shears is not, as may be supposed, by one defined step, but by gradual stages, making it as difficult in this, as in other classifications, to adopt any precise line of demar¬ cation. In addition to the above, or to shears properly so considered, there are a few tools known as cutting pliers, or nippers, in which the blades meet in direct opposition, but do not pass each other as in the legitimate kind of shears. This kind is represented by the section d, Fig. 302. Cutting pliers, if they admit of being classed with shears, are certainly the most simple of the group, and are used for cutting asunder small wires, nails, and a few other substances. Their edges are simply opposed wedges, exactly as shown in the above diagram at d\ and as respects the remainder of the instruments by which their wedges are composed, the most simple kind ex¬ actly resembles carpenters’ ordinary pincers for drawing out nails, except that the cutting pincers are made with thinner edges ; and Figs. 303 to 306 represent different kinds of cutting pliers and nippers. When cutting nippers are compressed upon a nail or a piece of wire, they first indent it on opposite sides, and when from their penetration the surfaces of the wedges exert a lateral pressure against the material, the latter eventually yields, and is torn asun¬ der at the moment the pressure exerted by the wedges exceeds the cohesive strength of the central metal yet uncut. Consequently the divided wire shows two beveled surfaces, terminating in a ridge slightly torn and ragged. The quantity of the material thus torn instead of being cut, will be the less, the softer the metal and the keener the pliers; but experience shows an angle of about 30 to 40 degrees to be the most economical for the edges of such tools. ' Little remains to be said on the varieties of cutting pliers; most of these used by general artisans and clockmakers are smaller than carpenters’ pincers, and the extremities of the jaws are beveled as in watch-nippers, Fig. 303, that they may cut pins lying upon a flat surface. Other cutting pliers, called side-nippers, are oblique, as in Fig. 304. Those used for the dressing-case, and known as nail- nippers, are concave on the edge, to pare the nails convex; and another kind, known as nipper-pliers, bell-hangers' or bottlers' pliers, have flat points at the end for grasping and twisting wires, and 23 354 THE PRACTICAL METAL-WORKER’S ASSISTANT. cutters on the sides for removing the waste ends, as shown in Pig. 305. The edges of cutting nippers are apt to be notched if used upon hard wires, or if wriggled whilst the cutting edges are buried in Figs. 303 304 the wire, and they scarcely admit of being reground or repaired. This inconvenience led to a modification of the instrument, Fig. 306, by the enlargement of the extremities, to admit of loose cut¬ ters fitted in shallow grooves being affixed by one screw in each as shown detached at c, so that the cutters may admit of removal and restoration by grinding, which end is effectually obtained, although somewhat to the prejudice of the instrument, by increas¬ ing its bulk. Scissors and Shears for Soft Flexible Materials. —The nippers have edges of about 30 to 40 degrees, meeting in direct opposition, but yet leave ragged edges on the work; whereas the shears have edges commonly of 90 degrees, seldom less than 60 degrees. These edges pass each other and leave the work re¬ markably keen and exact. Let the edges of scissors be ever so well sharpened, they act very imperfectly, if at all, unless the blades are in close contact at the time of passing; and this imperfection is the more sensible the thinner and more flexible the material to be cut, as it will then fold down between the blades if they do not come in contact. Whereas, when the blades exactly meet, the one serves to support the material whilst the other severs it; or rather this action is reciprocal, and each blade supports the material for the other, ren¬ dering the office of a counter-support, or of the bench, stool or cutting-board, used by the carpenter with the paring chisel. On a cursory inspection of a pair of ordinary scissors, it may be supposed that their blades are made quite flat on their faces, or with truly plane surfaces, like the diagram Fig. 307, representing the imaginary longitudinal section of the instrument, the two blades of which are united by a screw, consisting of three parts differing in diameter, namely, the head, the neck, and the thread; the bottom of the countersink that receives the head of the screw is called the shelf or the twitter-hit. If, however, the insides of •scissors were made flat, and as carefully as possible, they could tcarcely be made to cut slender fibrous materials, or if at all, then SHEARS. 855 for only a short period, and additional friction wonld accrue from the rubbing of their surfaces. The form which is really adopted, more resembles the exag¬ gerated diagram Fig. 308; the blades are each sloped some 2 or 3 degrees from the plane in which they move, so that their edges alone come into contact; instead of the blades being straight in their length they are a little curved so as to overlap; and close behind the screw-pin by which they are united, there is a little triangular elevation, insignificant in size but most important in effect, which may be considered as a miniature hillock or ridge, sloping away to the general surface near the hole for the screw. This enlargement or bulge is technically called the “riding part ,” and, as there is one on each blade, when the scissors are opened or that the blades are at right angles, the points or extremities only of the riding parts come into contact, and the joints may then have lateral shake without any prejudice. But as the blades are closed, first the bases or points of the riding parts, and lastly the summits or tops, rub against each other, and tilt the blades beyond the central line of the instrument; the effect of which is to keep the successive portions of the two edges in contact throughout the length of the cut, as by the time the scissors are closed, the points of the blades are each sprung back to the central line of the scis¬ sors, which is dotted in the diagram. Although scissors when in perfect condition for work may be loose, or shake on the joint when fully opened (and thereby placed beyond their range of action), they will be always found to be tight and free from shake, as soon as the blades can begin to cut the material near the joint, and so to continue tight until they meet at the points. That all scissors do exhibit this construction may be easily seen, as when they are closed and held edgeways between the eye and the light, they will be found only to touch at the points and at the riding parts, or those just behind the joint screw, the remainder being more or less open and gently curved ; and their elastic action will also be experienced by the touch, as whilst good scissors are being closed, there is a smoothness of contact which seems to give evidence of some measure of elas¬ ticity. Fig. 309 represents the section of the one blade of a pair of scissors, in which the elastic principle is differently introduced. These scissors are made without the riding part, but instead thereof, immediately behind the screw which unites the blade as usual, the 356 THE PRACTICAL METAL-WORKER’S ASSISTANT. one blade is perforated, for the purpose of admitting freely a small pin or stud fixed to the end of a short and powerful spring, so that the stud s, from acting on the opposite blade, throws the points of both towards each other, so as to give them a tendenoy to cross, but which being resisted by the edges of the blades touching one another, keeps them very agreeably in contact throughout their motion, and causes them to cut very well. If further evidence is wanted of the elastic principle in scissors, it is distinctly shown in sheep shears, which besides their ostensi¬ ble purpose of shearing off the fleece, are used by leather dressers and others. It is well known that sheep shears, Fig. 315, page 361, are made as one piece of steel, which is tapered at each end to constitute the cutting edges, is then for a distance fluted and straight to form the semi-cylindrical parts for the grasp, and that in the centre or opposite extremity, the steel is flattened and formed into a bow by which the blades are united and kept distended; sheep shears consequently require no joint pin, and the hands have only to compress them, as they spring open for themselves. If sheep shears are examined when fully opened, or when partially closed by tying round the blades a loop of string, it will be found that the blades have a tendency to spring into contact, as after having been pressed sideways and asunder, the cutting edges immediately return into exact contact the moment the distending pressure is removed. The construction of scissors with the riding-place, as adverted to in Fig. 308, is that which ordinarily obtains in most scissors, from the finest of those used by ladies, to the heavy ponderous shears for tailors, which sometimes weigh above six pounds, and are rested on the cutting-board by one of their bows, that are large enough to admit the whole of the fingers. The peculiar form of the insides of the blades is in all cases of paramount importance, and in the manufacture of fine scissors is attended by a person called a “putter-together,” whose province it is to examine the screw-joint, and see to the form of the riding- places, and lastly to set the edges of the scissors, which for gen¬ eral purposes are sharpened on an oilstone at an angle of about 40 degrees, but for the fine scissors more nearly upright or at 30 degrees from the perpendicular. So important, indeed, is the configuration of the inner face of scissors, that they should never be ground or meddled with at that part, but by a person fully experienced in their action, and scissors may with careful usage be kept in order for years without being ground, if the edges are occasionally set on the oilstone at the in¬ clination above referred to. It will frequently happen that well- made scissors which appear to grate a little when closed, merely do so from dirt or dust, which if removed by passing the finger along the edges, will restore the scissors to their smooth and pleasant action. It seems quite uncalled for to enter into the separate description SHEARS. 357 of various instruments known as button-hole scissors, cutting-out, drapers’, flower, garden, and grape scissors, horse trimming scis¬ sors; hair, lace, lamp, nail, paper, pocket, stationers’, and tailors’ scissors, and many others; nor of the large shears for the garden, such as pruning, trimming, and border shears, the distinctions be¬ tween which varieties are sufficiently known to those who use the several kinds, but the author will merely notice such of them as present any peculiarity of structure. Button-hole scissors are notched out towards the joint screw as in Fig. 311, so as to enable the instrument to make the incision a Figs. 310 311. little distant from the edge of the material; the joint must be made stiff, so as to prevent the points catching against each other. Flower and grape scissors assume the section of Fig. 310, so that they first cut the stem, and then hold it like a pair of pliers ; the one blade requires to be made in two parts riveted together; when entirely closed they present an elliptical section a ; and b shows how the stem of the flower is grasped; the blades are rounded at all parts that they may not injure the plants. Lamp scissors have the one blade very broad, and with a little rim, to prevent the snuff' of the lamp falling on the carpet. Nail scissors for the dressing-case are made very strong, and with short blades. In using scissors formed in the ordinary mode, the fingers and thumb of the right hand have naturally a tendency to press the blades together, in that position in which they are in¬ tended to cut; but the left hand, on the contrary, has a tendency to separate the blades and. defeat the principle on which scissors act. Therefore nail scissors are made in pairs, and formed in opposite ways, or as “ rights and lefts,” so that they may suit the respective hands. Pocket scissors have blades which admit of being locked to gether in the form represented in Fig. 312, as the point of one blade catches into a small spring near the bow of the other; and the in¬ strument cannot be opened until the spring or catch is released with the nail. When closed for the pocket, the bows stand on one line as at a b, when opened for use as at a c. Surgical scissors are of many forms, but have generally short blades, and long, straight, slender handles, that the hand may not 353 THE PRACTICAL METAL-WORKER’S ASSISTANT. impede the vision. In some of the surgical scissors the blades are curved as scimitars, and others are curved sideways; these kinds are difficult to make, as the elasticity of contact in the blade is re¬ quired nevertheless to be maintained. Many of the shears and scissors used in gardening, only differ from scissors and shears in general in their size, and the adaptation of their handles, some of which are of wood, and placed at an angle of 40 or 50 degrees, as in the letter Y inverted. Other garden shears used in trimming borders, have handles a yard long and inclined about 80 degrees to the blades, which may therefore lie on the ground whilst the individual stands nearly erect. Some of the border shears have rollers to facilitate their movement along the ground. In pruning shears and scissors, two peculiarities of form are judiciously introduced. In the more simple of the two kinds, which is shown in Fig. 313, the one part of the instrument termi¬ nates in a hook, with a broad and sometimes a roughened edge, to retain the branch from slipping away; the other part of the in¬ strument is formed as a thin cutting blade, the edge of which is convex. Theoretically it should be part of a logarithmic spiral, in which case the edge of the cutter would present a constant angle to the work throughout its action, and slide laterally through the incision made by itself, or make a sliding cut; whereas if the edge of the blade were radial, it would make a direct cut without any sliding, as in a paring chisel. The spiral blade cuts more easily, and will therefore remove a larger branch, with an action precisely analogous to that of the oblique cutters in some of the planes, although differently produced. Some of these instruments, when a little modified in form, are mounted on poles from 6 to 10 feet long, and are actuated by a catgut; this tool, which is known as the Averuncator, is very efficient for pruning at a considerable distance above the head. The other pruning, shears represented' in Fig. 314, are denom- Figs. 313 b a 314. mated sliding shears; the pin that unites the two parts fits in a round hole in the one blade and a long mortise in the other, and a link or bridle-rod c e, is attached by a screw to each lever; in con¬ sequence, when the instrument is fully opened the pin or fulcrum is at the end a, of the mortise, whereas, on the shears being grad¬ ually closed, the cutting blade slides downwards upon the pin until the fulcrum is near the opposite end b. In this modification of SHEARS. 359 shears the sliding action is produced to a much greater extent than with the spiral blade, but the construction is a little more ex¬ pensive ; and as the instrument is not provided with bows for the fingers, the spring d e, is added to throw it open. Before dismissing this subject, two modifications of shears will be briefly adverted to; those used by card makers, and the revolving shears employed in manufacturing woollen cloth. Card paper is prepared in large sheets; when dried and pressed it is cut into square pieces of the required sizes by means of long shears, the one blade of which is fixed at the end of a table, and has the joint at the farther extremity, whilst the cutting blade has a handle in front, and moves through a loop to keep the blade in its position, as in some chaff-cutting machines; there is also a stop fixed parallel with the blades, and as distant as the width of the slips into which the card is first divided, and these slips are then cut again the lengthway of the cards. The shears are moved so rapidly, that the action sounds like that of knocking at a door, and still the cards agree most rigidly in size. Revolving shears or “perpetual shears 1,1 are used for shearing off the loose fibres from the face of woollen cloths. For narrow cloths the cylinders are 30 inches long and 2 in diameter, eight thin knives are twisted around the cylinders, making 21 turns of a coarse screw, and are secured by screws and nuts which pass through flanges at the ends of the axis: formerly the cylinders were grooved and fitted with several thin narrow plates of steel 6 or 8 inches long. The edges of the eight blades are ground so as to constitute parts of a cylinder, by a grinder or strickle fed with emery, passed to and fro on a slide parallel with the axis of the cylinder, which is driven at about 1200 turns in the minute. In use, the cylinder revolves about as quickly, and in contact with the edge of a long thin plate of steel, called the ledger-blade, which has a very keen rectilinear edge, measuring 40 to 50 degrees; the blade is fixed as a tangent to the cylinder, and the two are mounted on a swing carriage with two handles, so as to be brought down by the hands to a fixed stop. The edge of the ledger-blade is sharpened, by grinding it against the cylinder itself with flour emery and oil, by which the two are sure to agree throughout their length. The cloth, before it goes through the process of cutting, is brushed so as to raise the fibres, it then passes from a roller over a round bar, and comes in contact with the spring bed, which is a long elastic plate of steel, fixed to the framing of the machine, and nearly as a tangent to the cylinder; this brings the fibres of the cloth within the range of the cutting edges, which reduce them very exactly to one level. The machine has several adjustments lor determining, with‘great nicety, the relative positions of the cylinder, ledger-blade and spring bar, but which could not be con¬ veyed without elaborate drawings. Formerly the cloth was passed over a fixed bed having a nearly sharp angular ridge, but which 360 THE PRACTICAL METAL-WORKER’S ASSISTANT. mode was far more liable to cut boles in tbe clotb than tbe spring bed. Broadcloths require cylinders 65 inches long, and machinery of proportionally greater strength. In the cross-cutting machine, the cloth is cut from list to list, or transversely, in which case the cloth is stretched by hooks at the two edges, and there are two spring beds; the cylinder in this machine is 40 inches long, and the cloth is shifted that quantity between every trip until the whole piece is sheared. The perpetual shears are also successfully applied to coarse fabrics, including carpets. A modification of the above revolving shears, made in a much less exact manner for mowing grass lawns, is fitted up somewhat as a wheelbarrow, or hand truck, so that the rotation of the wheels upon which the machine is rolled along, gives motion to the shears, which crop the grass to a level surface. Shears for Metal Worked by Manual Power. —When metals are very thin, such as the latten brass used for plating, and other purposes, they may be readily cut with stout scissors; and accordingly, we find the weakest of the shears for metal are merely some few removes in strength beyond the strong scissors for softer substances. It is however to be observed that, as common scissors are sharp¬ ened to an angle varying from about 50 to 60 degrees, they may fairly be considered to cut the materials submitted to their action; but shears for metal have in general rectangular edges, as they are seldom more acute than 80 degrees, and therefore instead of cutting into the material, they rather force the two parts asunder, by the pressure of the two blades being exerted on opposite sides of the line of division. It was recently stated to be of the utmost importance, that the blades of the weaker or elastic kind of shears should be absolutely in contact, or else thin flexible materials would be folded down between their blades without being cut. And it may now be urged as of equal importance, that the blades of the shears for metal should be also exactly in contact, not that rigid plates or bars of metal could be bent or folded down between their blades, even if these were a little distant; but the resistance to the operation of cutting would be then enormously increased, because the force exerted to compress the shears would not be then exerted in the line of their greatest resistance, which is strictly the case when the edges truly meet in one plane. If the blades were distant as in Fig. 320, from the want of direct support, the bar or plate would be tilted up and become jammed; this would tend further to separate the blades, and the shears would be strained or perhaps broken without dividing the bar, whereas all these evils are avoided if the shears close accurately in one and the same plane, as if the lower blade were shifted to the dotted line, and in which case they require the least expenditure of power and act with the best effect. SHEARS. 861 Hand shears, which are the smallest of these tools, are made of the form represented in Fig. 316, and vary from about four to nine 319 inches in total length. They are much used by tinmen, copper¬ smiths, silversmiths and others who work in sheet metals, and are often called snips, to distinguish them from bench shears. Some¬ times, however, they are fixed by the one limb in the table or tail vice, and then become essentially bench shears,—and this enables them to be used with soipewhat increased power. Bench shears of the ordinary form are represented in Fig. 317. The square tang t is inserted in a hole in the bench, or in a large block of wood, or else in the chaps of the bench vice itself. A less usual modification is seen in Fig. 318, with the joint at the far end, and the cutting part between the joint and the handle. Bench shears vary in total length from about one foot and a half to four feet, and the blades occupy about one-fifth of the length. Sometimes to increase the power of these shears the handle is forged thicker at the end to add weight, so that when the instru¬ ment is closed with a jerk, it may by its momentum cut thicker metal than could be acted upon by a simple thrust; but when con¬ siderable power is required it is better to resort to the shears next described. Purchase shears, which are represented in Fig. 321, are in every respect more powerful than those previously noticed ; the framing is much more massive, and the cutters are rectangular bars of steel inserted in grooves, to admit of their being readily sharp¬ ened or renewed. Instead of the hand being applied on the first lever or ah, a second lever c d e is added, and united to the first by the link h d, and but for the limit of the paper the hand lever c d e would have been represented of twice its present length. As the length of the part a h is three to four times the length of c d, the hand has to move through three to four times the space it would if applied directly to the shear lever, and consequently the purchase shears have three to four times the force of common shears, supposing the manual lever to be of equal length in each 362 THE PRACTICAL METAL-WORKER’S ASSISTANT. kind. There is usually at the back of the moving blade a very powerful spring or back stay, to keep the two edges in contact, and still further behind a stop to determine the lengths or widths of the pieces sheared off. Fig. 321. b Before using the shears, in those cases where the stop is not em¬ ployed to determine the width, it is usual to mark on the work the lines upon which it is intended to be sheared. The shears are then opened to the full, and the extremity of the line is placed in the angle formed by the jaws. If the work is short, it is also observed whether the opposite end of the line lies exactly on the edge of the lower blade; but if the work is long, the guidance is less easy. When the blades are closed the work will probably slip endlong, notwithstanding the resistance of the hand, until the angle at which the blades meet is so far reduced that they begin to grasp the work, when the extreme edge will be first cut through, and then the incision will be extended to the full length of the blades. As, however, each successive portion is severed, the two parts are bent -asunder to the angle formed by the blades, and both pieces become somewhat curved or curled up. Provided the cut is through the middle of the sheet, so that both are equally strong, the two parts become curved in the same degree; but when a nar¬ row and consequently weaker piece is removed from the edge of a wide sheet, the curling-up occurs almost exclusively in the nar¬ row strip, on account of its feebleness. In long pieces it is some¬ times necessary to increase the curvature, in order that as the work is sheared off the one part may pass above, and the other below the rivet or screw by which the halves of the shears are united. When from use or accident the joint becomes loose, so as not to retain the two parts in contact, in order to make the shears cut, the moving half must be pressed against that which is fixed to the pedestal or tail vice. Sometimes the sway of the blades of jointed SHEARS. 363 shears is prevented by allowing the moving arm to pass through a loop or guide which may retain it in position. Such a guide is mostly used in the light shears with which prin¬ ters cut their space line leads, or those thin strips of metal inserted between the lines of type, to separate them and make the printing more open. The leads are cast in strips about a foot long, and are cut into pieces of the exact width of a page, by laying them in a trough having at the end a pair of shears, and beyond these a stop to determine the precise length, so that any number of the leads may be cut exactly to the length required. Before adverting to the powerful shears used by engineers, two modifications of those already described will be noticed. Fig. 319, page 361, represents the section through the blades of a pair of shears, by which the tags or tin ferrules at the end of silk laces are cut and bent at one process, the general aspect of the tool being that of Fig. 317, page 361. The shearing blades are shaded obliquely in Fig. 319, and to the lower, which is fluted on the edge, is attached a stop that determines the width of the piece removed from the strip s, to make the tag. The upper shear blade, which is ground more acutely than usual, carries a ridge piece (shaded vertically), which compresses the strip as it is cut off, into the fluted edge of the lower blade, and thereby throws it into a chan¬ neled form; and by the employment of a pair of hollow pliers, or else a light hammer and a hollow crease, the bending is readily completed, and the tag attached to the cord. A nearly similar machine, but constructed more in accordance with the printers’ space line shears, is used for cutting slips of thin latten brass, into the channeled pens used in stationers’ machines for ruling the blue and red lines on paper for account books, etc. The one side of a slip of brass 1J inch wide, is thus cut and chan¬ neled at intervals suited to every line; the sides of every channel are closed to form a narrow groove, and the intervening pieces are removed with hand shears. The compound pen is fixed on a hinged board, and a strip of thick flannel laid at the top of the pen, is saturated with ink which flows steadily down all the channels, whilst the paper is moved horizontally under the pens, by two or three rollers and tapes, somewhat as in the feeding apparatus of printing machines, and thus the whole page is ruled one way and very quickly. Shears of the above kinds, with rectilinear blades, are not suited to cutting out curvilinear objects, such for example as the sides of callipers a, Fig. 349. The outline of such callipers is first of all marked on the sheet of steel from a templet, and with a brass wire which leaves a sufficient trace ; the outline is followed with a ham¬ mer and chisel upon an anvil, the chisel having a rounded or con¬ vex edge. Detached cuts running into one another are made round the curve, and the work is finally separated by pinching it in the tail-vice successively at all parts of the curve, and wrig¬ gling the other edge of the sheet with the hand until it breaks. 364 THE PRACTICAL METAL-WORKER’S ASSISTANT. The vice is often also used for cutting off straight pieces, which are then fixed with the line of division exactly flush with the chaps, and an ordinary straight chisel is so applied, that the cham¬ fer of the tool rests on the chaps of the vice, and the edge lies at a small angle to the work, and after each successive blow, the chisel is moved a little to the left without losing its general position. Engineers’ Shearing Tools ; Generally Worked by Steam Power.— The earliest machines of this class were scarcely more than a magnified copy of the bench shears shown on page 361, but made very much stronger; thus, Fig. 322 represents a shear¬ ing and squeezing tool used in some iron works and smithies. It has one massive piece that is fixed to the ground, and jointed to it is the lever, which carries at a, a pair of shearing cutters situated exactly on two radii struck from the centre of motion; this machine has also two squeezers b, for moulding pieces of iron when red-hot to the particular forms of the dies. The longer end of the lever is united by a connecting-rod to an eccentric stud in the disk d, which is made to revolve by the steam-engine. Shears are sometimes moved by means of an axis carrying two rollers, placed at the extremities of a diametrical arm, as in Fig. 323. The one roller acts on the radial part of the shear lever in the act of cutting, and the curved part then allows the lever to descend by its own weight rapidly, yet without a jerk, by the time the other roller comes into action for the succeeding stroke of the machine, which by this double eccentric makes two reciprocations for every revolution of the shaft. It is, however, more usual to employ cams, as in Fig. 324, and in this case the part of the cam which lifts the shear lever is usu¬ ally spiral, so as to raise it with equal velocity; the curve of the back is immaterial, provided it forms a continuous line so as to prevent the lever descending with a jerk. Fig. 325 represents the double shears; the one part, shown also detached, presents two horizontal but discontinuous edges with the axis in the centre, this piece is fixed to a firm support; the other or the moving part somewhat resembles the letter T or a pendulum, to the lower end of which, and beneath the floor, is SHEARS. 365 jointed a connecting-rod, that unites the pendulum with an eccen¬ tric or crank driven by the engine. The machine is double, or cuts on either side, and has two pairs of rectangular cutters of hardened steel, which may be shifted to bring the four edges of all of them successively into action. Boiler makers have great use for powerful shears for cutting plate iron from J to J, and sometimes f inch thick; and the next stage of their work is to punch the rivet holes by which the plates are attached. The two processes of shearing and punching are so far analogous in their requirements, that it is usual to unite the two processes in one machine; and as it sometimes happens the <■ F.g. 328. boiler maker’s yard is at a distance from the general factory, it then becomes necessary to work the shears by hand with a winch handle, and which is effected in the manner shown in Fig. 326, by the introduction of only one wheel and pinion. The wheel is fixed on the cam shaft, the pinion on the same axis that carries the heavy fly-wheel employed to give the required momentum; this mode of working the shearing and punching engine is perfectly successful, but of course less economical than steam or water power, the agency of which the machine is also adapted to receive. When shears that move on a joint and have radial cutters as in Fig. 322, are employed for thick bars, owing to the distance to which their jaws are opened, they meet at a considerable angle, and therefore from their obliquity they do not grasp the thick bar, but allow it to slide gradually from between them, to prevent which a rigid stop is added at the part c, Fig. 322, when, as the bar can no longer slide away it becomes severed. The shears with radial cutters, are also liable from their very oblique action to curve the plates; neither do they serve for making long cuts, as the joint then prevents the free passage of long work. All these inconveniences, however, are obviated in the shearing 366 THE PRACTICAL METAL-WORKER’S ASSISTANT. machines with slides, in which the edges approach in a right hue instead of radially, and are also nearly obviated in the very massive and powerful shearing and punching tool with jointed lever, first employed by French engineers and represented in Fig. 326, w r hich occupies an entire length of eleven feet, and serves for cutting plates not exceeding £ inch thick, cutting 12 inches in length at a time, and punching holes of 1£ inch diameter in £ inch iron. The shear¬ ing cutters are in this machine 15 inches long and raised above the centre of motion; as they lie on a chord instead of a radius, the longest pieces may therefore be cut without interference from the joint, and the cutters have the further advantage of meeting at a much smaller angle than if fitted radially. The portable punching and shearing* machine shown in front and side elevation in Figs. 327 and 328, will serve for a general exam¬ ple of such machines, as the differences in the several constructions are only those of form and arrangement, and not of principle. Figs. 327 328. This machine stands upon a base of a triangular form, and has in front a strong chamfer slide, which is reciprocated in a vertical line, by an eccentric that is concealed from view, it being immedi¬ ately behind the slide, and upon the same axis, as the eccentric is the toothed wheel. The pinion that takes into this wheel, is on the shaft that carries the fly wheel, and one of the arms of the latter receives the handle by which the machine is usually worked; or if it is driven by power, fast and loose pulleys are then fixed on the same axis as the fly wheel. The upper part of the slide carries a shearing cutter, which is SHEARS. 367 abo^t 7 inches wide, and meets a similar cutter that is fixed to the upper and overhanging part of the casting. The cutters, although ground with nearly rectangular edges, are beveled to the extent of about three-fourths of an inch in the direction of their length, that they may commence their work on the one edge, and therefore more gradually than if the entire width of the cutter penetrated at the same instant: this degree of obliquity does not cause the work to slide from the shears, neither does it materially curl up the work; and as the blades are quite clear of the framing, a cut may be extended throughout the longest works, provided the cut is not more than five inches from the edge of the plate, the distance of the cutters from the framing of the machine. The above machine, which measures in total height about five feet, makes 12 or 15 strokes per minute, shears J inch iron plates, and punches f holes in iron J inch thick. A larger machine makes 10 or 12 strokes per minute, shears f inch plate, and punches Id inch holes in iron f inch thick; and a still heavier machine, working at 8 or 10 strokes in the minute, shears 1 inch plates, and punches 2 inch holes in iron 1 inch thick. Some of these are pro¬ vided with railways by which the work is carried to the sheais or punches, as will be described; and the bar-cutting machine, having only shearing cutters at the bottom, and the eccentric at the top of the slide, is used for cutting bars not exceeding 6§ inches wide by If thick, or bars 2 or square, but we think these dimensions of the works performed might, if required, be greatly exceeded in heavier machines. There is a shearing machine for cutting wide plates of sheet iron, which is used in the manufacture of wrought iron; it has two wide cutters of steel fixed to the edges of thick plates of cast-iron; the lower cutter is at rest and quite horizontal, the upper cutter bar is fitted in grooves at the end of the frame, so as to be carried up and down vertically, by a shaft or spindle immediately above the cut- _ ter and parallel with it; this shaft has an eccentric at each end, and one in the centre, and three connecting links, which attach the cutter frame to the eccentrics, and give it a small reciprocating mo¬ tion. The upper cutter is a little oblique, so as to begin to act at the one end, and in removing the strips curls them but very little; A vice* for cutting wide pieces of boiler plate, is based on the mode of cutting thin slips of sheet metal over the chaps of the ordinary tail vice, as described on page 363-4. The jaws of the machine are about six feet long, faced with steel, and powerfully closed by two perpendicular screws and nuts, one at each end, which also secure the machine to the ground. The plate of iron is therefore fixed horizontally and with the line of division level with the jaws. A strong rod chisel struck with sledge-hammers, is applied successively along the angle formed between the work and the vice, and after the iron has been indented the whole length, the blows of the sledges directed on the overhanging piece of iron complete the separation. 368 THE PRACTICAL METAL-WORKER’S ASSISTANT. Fig. 329 represents the plan, and Fig. 330 the partial vertical section of a “ hydraulic machine for cutting off copper bolts.” The circle in Fig. 329 represents the cylinder of a hydrostatic press, which is flattened to the width of the rectangular bar that is fixed alongside of the cylinder, the two being enveloped in the ex¬ ternal casting which is shaded in the section Fig. 330, and resem¬ bles a stunted pillar three or four feet high. The whole of the parts are traversed by nine sets of holes suitable to bars from f to 2J inches diameter; the holes where they meet on the lines b b, are furnished with annular steel cutters, and are enlarged outwards each way to admit the work more easily. The rod r r, to be sheared, is introduced whilst the holes are directly opposite or continuous, and the men then pump in the in¬ jection water through the pipe w; it acts upon the annulus or shoulder intermediate between the two diameters of the cylindei. Figs. 329 330 331 332 333. causes the descent of the latter with a pressure of about 100 tons, and forces the bar asunder very quietly, and, from the annular form of the cutters, without bruising it. When the bar has been cut off, the injection water is allowed to flow out from beneath the cylinder, and the latter is raised by a loaded lever beneath the floor ready for the next stroke. The machine is far more econo¬ mical in its action than the old mode of cutting off the copper bolts with a frame saw used by hand, and the storekeeper in charge of the bolts can, if needful, perform the entire operation unassistedly, although usually four men work the pair of one inch injection pumps by a double-ended lever, as in a fire engine. In concluding this subject it is proposed to speak of the rotary shears for metal, which have continuous action like rollers, and are pretty generally used. In the best form of the instrument, two spindles, connected together by toothed wheels of equal size, have each two thin disks of different diameters, which are opposed to each other, that is, a large and a small in the same plane, as in the diagram. Fig. 331; the larger disks overlap each other and travel in lateral contact, and therefore act just like shears, and the two disks in each plane meet, or rather nearly meet, so as just to grasp between them, after the manner of flatting the rollers, the two SHEARS. 369 parts of the strip of metal which have been severed, and by carry¬ ing these forward they continually lead the yet undivided part of the metal to the edges of the larger disks, which in this manner . quickly separate the entire strip of metal into two parts. The machine requires that the spindle carrying the disks should have an adjustment for lateral distance, as in flatting rollers, to adapt their degree of separation to the thickness of the metal to be sheared. One of the spindles should also have an endlong adjustment to bring the disks into exact lateral contact, and the machine requires in addition a fence or guide fixed alongside the revolving shears to determine the width of the strips cut off. Sometimes the two smaller disks are omitted, and the larger alone used, as in Fig. 382 ; the circular shears are then somewhat less exact in their action, but perform nevertheless sufficiently well for most purposes. Circular or rotary shears are very useful for shearing plates not exceeding one-eighth of an inch thick, and one of the advantages which the rotary possesses over the common shears, is the facility with which curved lines may be followed, on account of the small portion of the disks that are in contact, whereas the length of rec¬ tilinear shear blades prevents their ready application to curves. Of course the speed at which the machines may be driven depends on the nature of the work, and if the cuts are straight and the plates light, the velocity of the shears may be considerable. The circular shears, or splitting rolls used in the works where wrought-iron is manufactured, are composed of steel disks of equal thickness, but of two diameters, arranged alternately upon two spindles, as in Fig. 333, so as at one action to split thin plates of iron of about 6 inches in width into very narrow pieces known as Fig. 334. nail rods, and into strips from half to one inch wide, designated as bundle or split iron. Of course different pairs of rolls are required for every different width of the strips thus manufactured. The anti-friction cam press, invented by David Dick, of Meadville, Pennsylvania, is destined to become of great use to the metal¬ worker. This press is much more easily con¬ structed, and can be supplied for much less cost than that of Timothy Brahmah; it also can be made to accomplish its work with much greater expedition. There are many arrangements for shears, punches, and presses for iron and steel, one of which may be described thus: A A, Fig. 334, are two eccentric wheels, and B is a rob r between. C C are two pair of sectors, constituting the bearings of the axes of the sectors. The axes of the sectors are of the 24 370 THE PRACTICAL METAL-WORKER’S ASSISTANT. knife-edge shape. D is the bearing, and R is the follower of the sectors. This combination, Fig. 334, is inclosed in a frame, Fig. 335. The centre roller B is made to revolve, which carries by its trac¬ tion the two eccentric wheels A A, which have their bearings on the faces of the sectors, which are transferred the length of their faces right and left, the sectors being knife-edge shaped at the cen¬ tres of motion 0 O, which revolve with very little friction. When A A have made their revolution the follower R will have moved the sum of the two eccentrics. Figs. 335 336. Fig. 336 is a side view with one side of the frame removed. A press constructed in this way, the follower moving down a spring S, may be used to return the moving parts when the press is relaxed. CHAPTER XXI. PUNCHES. Punches used without Guides. —This title may, at the first glance, only appear to possess a very scanty relation to the tools used in mechanical manipulation, as the ostensible purpose of a punch may be considered to be only that of making a round or square hole in any thin substance. But it frequently happens that the small piece or disk so removed by the punch, is the particular PUNCHES. 371 object sought, and some of the very numerous objects thus made with punches assume a very great importance in the manufacturing and commercial world, as will perhaps be admitted when a few of these are referred to. The general character of a punch is that of a steel instrument, the end of which is of precisely the form of the substance to be removed by the punch, and which instrument is forcibly driven through the material by the blow of a hammer. When the sub¬ ject is entertained in a moderately extended sense, it will be seen that much variety exists in the forms of the punches themselves, and also in the modes by which the power whereby they are actuated is applied. So far as relates to the actual edges of the punches by which the materials are severed, they may be classed under two principal di¬ visions, namely, duplex punches, and single punches. The duplex punches have rectangular edges and are used in pairs, often just the same as in shears for metal. The single punches have some¬ times rectangular but generally more acute edges, the one side being mostly perpendicular. The single punches require a firm support of wood, lead, tin, cop¬ per, or some yielding material, into which the edge of the punch may penetrate without injury, when it has passed through the material to be punched. The following classification has been attempted, as that best cal¬ culated to throw into something like order the miscellaneous instru¬ ments that will presently be more or less fully described. Punches used without guides. Punches used with simple guides. Punches used in fly presses, and miscellaneous examples of tlieir products. Punching machinery used by engineers. It would be hardly admitted that a carpenter’s chisel, driven by a mallet through a piece of card, could be considered as a punch, still the circular punch used with a mallet on a block of lead, for cutting out circular disks of cards for gun-wadding, is indisputably a punch, and yet scarcely more than a chisel bent round into a hoop. The gun-punch is formed as in Fig. 337, and is turned conical without and cylindrical within, or rather a little larger at the top, that the waddings may freely ascend, and make their way out at the top through the aperture; when, however, annular punches exceed about 2 inches in diameter, it is found a stronger and better method to make them as steel rings, attached to iron stems or centres spread out at the ends to fill the rings, as in Fig. 338, but holes are then required to push out the disks that stick to the punch, as shown by the section beneath the figure 338. The punch used in cutting out wafers for letters is nearly simi¬ lar, it being formed as a thin cylindrical tube of steel, fitted to the end of a perforated brass cone having at the top two branches for the cross handle, by which it is pressed through several of the 372 THE PRACTICAL METAL-WORKER’S ASSISTANT. farinaceous sheets, and as the wafers accumulate in the punch they escape at the top. Confectioners use similar cutters in making lozenges, and frequently the thin steel cutter is fixed to a straight perforated handle of wood. The lozenges are cut out singly and with a twist of the hand. When the disk is the object required, the punch is always cham- ferred exteriorly, as then the edge of the disk is left square and the external or wasted part is bruised or bent; but the punch is made cylindrical without, and conical within, when the annulus or exter¬ nal substance is required to have a keen edge. And when pieces such as washers, or those having central holes, are required in card or leather, the punches are sometimes constructed in two parts, as shown separated in Fig. 339, the inner being made to fit the outer punch, and their edges to fall on one plane; so that one blow effects the two incisions, and the punches may then be separated for the removal of the work, should it stick fast between the two parts of the instrument. Punches of irregular and arbitrary forms, used for cutting out paper, the leaves for artificial flowers, the figured pieces of cloth for uniforms and similar things, are made precisely after the manner of Fig. 337, and also of Fig. 338, except that they are forged in the solid, or without the loose ring. These irregular punches are, however, much more tedious to make than the circular, which admit of being fashioned in the lathe. Figured punches of much larger dimensions have been of late used for cutting out the variously formed papers used in making envelopes for letters. The punch or cutter is sometimes made in one piece as a ring an inch to an inch and a half deep, or else in several pieces screwed around a central plate of iron, and when the punch is sharp it is really forced through three to five hundred thicknesses of paper, by the slow descent of the screw press in which it is worked. Army clothiers use similar instruments for cutting out the leather for shoes and various other parts of military clothing, and several of these punching or cutting tools are often grouped together. Proceeding to the punches used for metal, those having the PUNCHES. 373 thinnest edges are known as "hollow punches; they are turned of various diameters, from about £ to 2 inches, and of the section Fig. 340; they are always used on a block of lead, and sometimes for two or three thicknesses at a time of tinned iron, copper, or zinc, Punches 341, smaller than £ inch, are generally solid, quite flat at the end, and are also used on a block of lead, which, although it gives a momentary support, yields and receives into its surface the little piece of metal punched out by the tool. Fig. 343 represents the punch used by smiths for red-hot iron; the tool is solid and quite flat at the end, and whether it is round, square, or oblong in its section, as for producing the holes repre¬ sented, it is parallel for a short distance, then gradually enlarged, and afterwards hollowed for the hazel rod by which it is surrounded to constitute the handle. The smith’s punch is frequently used along with a bottom or bed tool known in this case as a bolster, and which has a hole exactly of the same area as the section of the punch itself. Punches when used in combination with bolsters are clearly similar in their action to the shears with rectangular edges, as will be seen on comparing Figs. 342 and 343, the only difference being that the straight blade of the shears is to be considered as bent round into a solid circle for a circular punch, or converted into a square, rectangular, or other figure, as the case may be; but every part of the punch should meet its counterpart or the bolster in lateral contact, the same as formerly explained in reference to shears. This supposes the tools to be accurately made and correctly held by the smith, but which is somewhat difficult, because the bolster, the work, and the punch, are all three simply built up loosely upon the anvil, and the eye can render but little judgment of their rela¬ tive positions; the punch is consequently apt to be misdirected so as to catch against the bolster and damage both tools. The mode sometimes used to avoid this inconvenience is represented in Fig. 344, in which a guide is introduced to direct the punch ; but agreea¬ bly to the proposed arrangement, this figure will be more fully explained hereafter, when some other tools of a lighter description have been spoken of. , 374 THE PRACTICAL METAL-WORKER’S ASSISTANT. Fig. 315 shows a punch used by harp-makers and others in cut¬ ting long mortises in sheet metal. The punch is parallel in thick¬ ness, and has in the centre a square point from which proceed several steps ; this punch is used with a bolster having a narrow slit as long as the width of the punch. A small hole is first drilled in the centre of the intended mortise ; the first blow on the punch converts this into a square, the next cuts out two little pieces ex¬ tending the hole into a short mortise, and each successive blow cuts out a little piece from each end, thereby extending the mortise if needful to the full width of the punch. From the graduated action the method entails but little risk of breaking the punch or bulging the metal, even if it should have but little width. Sometimes, to make the punch act less energetically at the commencement of its work, the steps at the point are made smaller both in height and width; the serrated edge then becomes curved instead of angular, as shown. Punches used with simple Guides. —Beginning this part of the subject with the tools having the most acute edges, we have to refer to the punch pliers, Fig. 346, fitted with round hollow punches for making holes in leather straps and thin materials. Some pliers of this kind have a small oval punch, terminating in a chisel edge, for cutting those holes that have to be passed over buttons ; and pliers have been made with circular, square and triangular punches for the cruel practice of marking sheep in the ear. In all these tools the punch is made to close upon a small block of ivory or copper, so as to insure the material being cut through without injuring the punch. Another example of slender chisel-like punches is to be seen in the machine for cutting the teeth of horn and tortoise-shell combs. The punch or chisel is in two parts, slightly inclined and curved at the ends, to agree in form with the outline of one tooth of the comb. The cutter is attached to the end of a jointed arm, moved up and’down by a crank, so as to penetrate almost through the material, and the uncut portion is so very thin that it splits through at each stroke and leaves the two combs detached. Figs. 346 347. The little instrument called a pen-making machine, is another ingenious example of punches moving on a joint. It is repre¬ sented of half its true size, and ready to receive the pen, in Fig. 347, and in Fig. 348 the two cutters are shown of full size and PUNCHES. 375 laid back in a right line—although in reality it only opens to a right angle. The lower half has a small steel cutter b, pointed to the angle of the nibs of the pen, and fluted to the curve of the quill as at a ; the upper cutter d is made as an inverted angle with nearly vertical edges, as seen at e, which exactly correspond with the lower cutter, so as between them to cut the shoulders of the pen. The upper tool also carries a thin blade or chisel, which penetrates nearly through the quill and forms the slit. The quill having been pared down to its central line, is inserted through the hollow joint, on the line f and the cutters being very near the joint, the lever on being closed gives abundant power for the penetration of the punches. The pen requires to be after¬ wards nibbed, and for which purpose another cutter is attached to the instrument, which has likewise an ordinary pen-blade, so as to be entirely complete in itself. Passing from the punches with guides obtained by means of joints, and actuated by the pressure of the fingers, we will return to Fig. 344, on page 373, which with its simple guide becomes a very effective tool sometimes known as the hammer press, in con¬ tradistinction to the screw, or fly-press to be hereafter spoken of. The guide in the contrivance, Fig. 344, is a strong piece of iron attached to the bottom tool, and sufficiently above it to admit the work between the two. Each part is pierced with a hole of ex¬ actly the same size, and accurately formed as if they were inter¬ rupted portions of the same hole. The punch is made exactly to fit either hole, so that from the upper it receives a eorrect guid¬ ance, and it therefore cuts through the material, and penetrates the lower piece, with a degree of precision and truth scarcely attain¬ able when the tools are unattached, and are used simply upon the anvil, as before described. As however the punch mostly sticks tight in the work, it is needful to turn the instrument over, and drive out the punch with a drift a little smaller than the punch, and on which account punch¬ ing tools of this kind are often made of two parallel plates of steel firmly united by screws or steady pins, yet separated enough for the reception of the work, and frequently contrivances are added to guide the works to one fixed position, in order that any number of pieces may be punched exactly alike. Thus in punching circular mortises, as in the half of a pair of inside and outside callipers a, Fig. 349, the punch c, is first used to produce the central hole, and this punch is then left in the bed b, to retain the work during the action of the second punch m, by which the mortise is cut. The punch m, is very short, to avoid the chance of its being broken, and it is also narrow, so as to em¬ brace only a short portion of the mortise, which is then completed, with little risk to the tool, at three or four strokes, whilst the punch c serves as a central guide. Occasionally also punches of this simple kind, but on a larger scale, have been placed under drop hammers, falling from a con- 376 THE PRACTICAL METAL-WORKER’S ASSISTANT. siderable height through guide rods, somewhat as in a pile-driving machine. This mode of obtaining power is not suited to the action of punches used in cutting out metals, amongst other reasons, be¬ cause the punch sticks very hard in the perforation it has made, and requires some contrivance for pulling it out, which is not so easily obtained in this apparatus as in fly-presses, that are suited alike to large and small works. The drop hammer, or as it is more commonly called a force, is however very much used in the manufacture of stamped works, or such as are figured between dies, of which an example is de¬ scribed at length in page 312. Compared with a fly-press of equal power, the force is less expensive in its first construction, but it is also less accurate in its performance. Fig. 350 is a very simple yet effective tool, which may be viewed as a simplification of the fly-press 1 it consists of one very strong piece of wrought-iron, about one inch thick and four or five inches Figs. 349 350. wide, thickened at the ends and bent into the form represented ; the one extremity is tapped to receive a coarse screw, the end of which is formed as a cylindrical pin, or punch, that is sometimes made in the solid with a screw, but more usually as a hardened steel plug inserted in a hole in the screw. Immediately opposite to the punch is another hole in the press, the extremity of which is fitted with a hardened steel ring or bed punch. When the screw is turned round by a lever about three feet long, it will make holes as large as § inch diameter in plates f inch thick, and is therefore occasionally useful to boiler makers for repairs, and also for fitting works in confined situations about the holds of ships, and other purposes. When this screw is turned backwards the punch is drawn out and relieved from the work, but the sorewing motion is apt to wear out the end and side of the punch, and therefore to alter its dimensions. A very convenient instrument of exactly the same kind is used in punching the holes in leather straps, by which they are laced together with leather thongs, or united by screws and nuts, to con¬ stitute the endless bands or belts used in driving machinery. In this case the frame of the tool is made of gun-metal, and weighs only a few ounces, the end of the screw is formed as a cutting punch, and it is perforated throughout, that the little cylinders of PUNCHES. 377 leather may work out through the screw, which only requires a cross handle to adapt it to the thumb and fingers. In this case the screwing motion is desirable, as the punch in revolving acts partly as a knife, and therefore cuts with great facility, as the leather is supported by the gun-metal which consti¬ tutes the clamp or body of the tool. Punches used in Fly-Presses, and Miscellaneous Exam¬ ples of their Products.— The punches used in fly-presses, do not differ materially from those already described, but it appears needful to commence this section with some explanation of the principal modifications of the press itself. The fly-press is a most useful machine, which, independently of the punch or dies where¬ with it is used, may be considered as a means of giving a hard, unerring perpendicular blow, as if it were a powerful well-directed hammer. The precision of the blow is attained by the slide where¬ by the punch is guided, the force of the blow by the heavy revolv¬ ing fly attached to the screw of the press. When the machine is used, the fly is put in rapid motion, and then suddenly arrested by the dies or cutters coming in contact with the substance submitted to their action. The entire momentum of the fly, directed by the agency of the screw, is therefore instantaneously expended on the work to be punched or stamped, and the reaction is frequently such as to make the screw recoil to nearly its first position. The bare enumeration of the multitude of articles that are par¬ tially or wholly produced in fly-presses, would extend to consid¬ erable length, as this powerful and rapid auxiliary is not only employed in punching holes, and cutting out numerous articles from sheets of metal and other materials, but also in moulding, stamping, bending or raising thin metals into a variety of shapes, and likewise in impressing others with devices, as in medals and coins. Fig. 351 represents a fly- press of the ordinary construc¬ tion that is used for cutting out works, and is thence called a cutting press, in contra-dis¬ tinction to the stamping or coining presses. It will be seen that the body of the press, which is very strong, is fixed upon a bed or base that is at right angles to the screw ; the latter is very coarse in its pitch, and has a double or triple square thread, the rise of which is from about one to six inches in every revolution. The nut of the screw is mostly of gun-metal, and fixed in the Fig. 351. 378 THE PRACTICAL METAL-WORKER’S ASSISTANT. upper part or head of the press. The top of the screw is square or hexagonal, and carries a lever of wrought iron, terminating in two solid cast-iron balls, that constitute the fly, and from the lever the additional piece h, descends to the level of the dies to serve aa the handle, so that the left hand maybe used in applying the material to be punched, whilst the right hand of the operator is employed in working the press. The screw is generally attached to a square bar called the fol¬ lower, which fits accurately in a corresponding aperture and ia strictly in a line with the screw; and to the follower is attached the punch shown detached at a. The punch is sometimes fitted into a nearly cylindrical hole, and retained by a transverse pin or a side screw, but more generally the die is screwed into the fol¬ lower, like the chucks of some turning lathes; the bed or bottom die c, which is made strictly parallel, rests on the base of the press, and is retained in position by the four screws, that pass through the four blocks called dogs; these screws, which point a little downwards, allow the die to be accurately adjusted, so that the punch may descend into it without catching at any part, and thereby inflicting an injury to the tools. The piece b, which rests nearly in contact with the die, is called the puller off, it is perforated to allow free passage to the punch; when the latter rises, it carries up with it for a short distance the perforated sheet of metal that has been punched through, but which is held back by the puller ofi^ whilst the punch continuing its ascent rises above the puller off, and leaves behind the sheet of metal so released; the sheet is again placed in position whilst another piece is punched out, and so on continually. Before proceeding to speak of some of the works produced in stamping presses, it is proposed to describe some of the points of difference met with in fly-presses. The body of a cutting press is in general made with one arm, as represented in Fig. 351, because the sheet of metal can be more freely applied to the die ; but stamping and coining presses, which are used for pieces that have been previously cut out, require greater strength and have two arms, or are made somewhat as a strong lofty bridge with the screw in the centre. The fly of the press is frequently made as a heavy wheel, which may be more massive and is less dangerous to bystanders than the lever and balls, and in large presses there are two, three, or four handles fixed to the rim, as many men then run round with the fly, and let go when the blow is struck. Fly-presses are variously worked by steam-power; thus in the mint the twelve presses for cutting out the blanks or disks for coin, are arranged in a circle around a heavy fly-wheel, which re¬ volves horizontally by means of the steam-engine. The wheel has one projecting tooth or cam, which catches successively the twelve radial levers fixed in the screws of the presses, to cut the blanks, and twelve springs immediately return the several levers to their first positions, ready for the next passage of the cam on the wheel. PUNCHES. 379 The fly and screw are also worked by power, in some cases by an eccentric or crank movement fixed at a distance; a long con¬ necting-rod then unites the crank to an arm of the wheel, or to a straight lever, and gives it a reciprocating movement. At other times, in place of the crank motion are ingeniously substituted a piston and cylinder worked after the manner of an oscillating steam-engine, if we imagine the boiler to be superseded by a large chamber, exhausted by the steam-engine nearly to a vacuum, thus constituting an air engine, the one side of the piston being opened for a period to the exhausted chamber, whilst the other receives the full pressure of the atmosphere. In the manufacture of steel pens, it is important to have an exact control over the punches which cut the slits, and those which mark the inscriptions, as by descending too far they might dis¬ figure the steel, or even cut it through. Accordingly there is in¬ troduced between the head of the press and the lever an adjusta¬ ble ring, which acts as a stop, and only allows the punches to descend to one definite distance, until in fact the ring is pinched between the press and lever. The screw of the fly-press is sometimes superseded by a contriv¬ ance known both as the toggle joint, and as the knee joint. The two parts a, b, and b, c, Fig. 352 are joined to each other at b, the Figs. 352 353. extremity a, is joined to the upper part of the press, and c, to the top of the follower. When the parts a, b, and b, c, are inclined at a small angle, the extremities, a, and c, are brought closer together, and raise the follower, but when the two levers are straightened, a and c separate with a minute degree of motion, but almost irre¬ sistible power, especially towards the completion of the stroke. The bending and straightening of the toggle joint is effected by the revolution of a small crank, united to the point b, Fig. 352, by a connecting rod b,f Presses with the toggle joint are perfectly suited to cutting out works with punches and bolsters, provided the relative thickness 380 THE PRACTICAL METAL-WORKER’S ASSISTANT. of the work and tools are such as to bring to bear the strongest point of the mechanical action, at the moment the greatest resist¬ ance occurs in the work; but as the fly-press with a. screw is in all cases powerful alike, irrespective of such proportions, provided alone that there is sufficient movement to create the required momentum, the fly-press is more generally useful. The cut 353 refers to a lever press worked by an eccentric, and used in cutting brads and nails, which will be again alluded to when this manufacture is briefly noticed. It is now intended to describe a few examples of works executed in fly-presses, giving the preference to those appertaining to mechanism. The round disks of metal for coin are always cut out with the fly-press, and are then called blanks, the punch being a solid cylinder, the bed or bolster a hollow cylinder that exactly fits it. In the gold currency, more especially, great care is taken to make these punches as nearly as it is possible mathematically alike in diameter, and the sheets of gold also mathematically alike in thick¬ ness, by aid of the drawing rollers or rather drawing cylinders referred to in page 327; but notwithstanding every precaution, the pieces or blanks when thus prepared do not always weigh strictly alike. This minute difference is most ingeniously remedied by using the one error as a compensation for the other. Trial is made at each end of every strip of gold; and by cutting the thicker gold with the smaller punches, the adjustment is effected with the needful degree of accuracy, so that every piece is made critically true in weight, without the tedious necessity for weighing and scraping, otherwise needful. Buttons are made in enormous quantities by means of the fly- press. That metal buttons should be thus cut out with tools and stamped with dies, will be immediately obvious to all, but the fly- press has been also more or less employed in making buttons of horn, shell, wood, papier-mache, and some other materials. Amongst others, may be noticed the silk buttons, called Florentine buttons, each of which consists of several pieces that are cut out in presses, then enveloped by the silk covering, and clasped together at the back (in the press), by a perforated iron disk, the margin of which is formed into 6 or 8 points that clutch and hold the silk, whilst the cloth by which the button is sewed on, is at the same time pro¬ truded through the centre hole in the back plate of the silk button; details that may be easily inspected by pulling one of them to pieces. Indeed great ingenuity has been displayed, and many patents have been granted, for making this necessary article of dress, a button. Hound washers that are placed under bolts and nuts in machin¬ ery, are punched out just like the blanks for coin; although in punching the larger washers, that measure 5 and 6 inches in diam¬ eter and ^ inch thick, with the. ordinary fly-presses, the iron requires to be made red hot. PUNCHES. 381 The round or square holes in the washers are made at a second process with other tools, and to insure the centrality of the holes, some kind of stop is temporarily affixed to the lower tool. The more complete stop is a thin plate of iron hollowed out at an angle of from 90 to 120 degrees and screwed on the top of the bed, as this may be set forward to suit various diameters. But the more usual plan is to drill two holes in the bed, to drive in two wires, and to bend their ends flat down towards the central hole, as also shown in Fig. 354; the end of the wires are filed away until, after a few trials, it is found the blank, when held in contact with the stops by the left hand, is truly pierced; the whole quantity may be then proceeded with as rapidly as the hands can be used, with confi¬ dence in the centrality of all the holes thus produced. Chains with flat links that are used in machinery are made in the fly-press. The links are cut out of the form shown at a, Fig. 355, the holes are afterwards punched just as in washers and one at a time, every blank being so held that its circular extremity touches the stops on the bed or die, and thereby the two holes become equi¬ distant in all the links, which are afterwards strung together by inserting wire rivets through the holes. The pins or rivets for the links are cut off from the length of wire in the fly-press, by a pair of cutters like wide chisels with square edges, assisted by a stop to keep the pins of one length; or by one straight cutter and an angular cutter hollowed to about 60 degrees; or by two cutters each hollowed to 90 degrees. In the three cases, the wire is respectively cut from two, three, or four equidistant parts of its circumference: semicircular cutters are also used. The straight cutters first named, are moreover very usefully employed in the fly-press for many of the smaller works, that would otherwise be done with shears. Sometimes the succession of the links for the chain, is one and two links alternately, as at b, Fig. 355 ; at other times 3 and 2, or 4 and 3 links, as at c, and so forth up to about 9 and 8 links alter- Figs. 354 ah c nately, which are sometimes used, and the wires when inserted are slightly riveted at the ends. The pin is generally the weakest part of the chain and gives way first, but in the chains with 8 or 9 links, the pin must be cut through at 16 places simultaneously, before the chain will yield. 882 THE PRACTICAL METAL-WORKER’S ASSISTANT. Chains are sometimes intended to catch on pins or projections, around a wheel of the kind shown in Fig. 357, to fulfil the office of leather bands, without the possibility of the slipping, which is apt to occur with bands when subjected to unusual strains. Such chains are made after the manner shown in Fig. 356 : to constitute the square openings that fit over the pins of the wheel, the central links are made shorter, by which means the apertures are brought closer together than if the longer links were used throughout. Fig. 358 shows a different kind of chain, that has been used for catching in the teeth of an ordinary spur-wheel with epicycloidal teeth: this chain was invented by John Oldham, Engi¬ neer to the Bank of Ireland. Chains for watches, time-pieces, and small machinery, are too minute to be made as above described, therefore the slip of steel is first punched through with the rivet holes required for a num¬ ber of links, by means of a punch in which two steel wires are inserted; the distance between the intended links is obtained (somewhat as in file cutting) by resting the burrs of the two pre¬ vious holes against the sharp edge of the bed or bolster. The links are afterwards cut out by a punch and bolster of the kind already noticed, but very minute, and the punch has two pins in¬ serted at the distance of the rivet holes, the slip of steel being every time fitted by two of the holes to these pins; all the links are thereby cut centrally around the rivet holes. The tools are carried in a thick block having a perpendicular square hole, fitted with a stout square bar; the latter is driven with a hammer, which is supported on pivots, raised by a spring, and worked by a pedal; but when the links measure from £ to £ an inch in length, such tools are worked by a screw. The punches are fitted to the side of the square bar, in a pro¬ jecting loop or mortise, and secured by a wedge. They are drilled with holes for the pins, and across each punch there is a deep notch to expose the reverse ends of the pins, in order that when broken they may be driven out and replaced. The pins are taper pointed, that they may raise burrs, instead of cutting the metal clean out, and being taper, no puller-off is required, and the bed tools are fitted in chamfer grooves in the base of this old yet very efficient instrument. A large chain for a pocket chronometer now before the author, measures nearly 14 inches in length, and contains in every inch of its length 22 rivets and also 33 links, (in three rows); the total number of pieces in the chain is therefore 770, and its weight is 91 grains. A chain for a small pocket-watch measures 6 inches in length, and has 42 rivets and 63 links in every inch, in all 630 pieces, and yet the entire chain only weighs one grain and three- quarters. The square links of chains for jewelry are often cut out with punches, the exterior and interior being each rectangular; after which each alternate link is slit with a fine saw for the introduc- PUNCHES. 383 tion of the two contiguous links, and then soldered together so that the gaps become filled up. Other chains are drawn as square tubes, and cut off in short lengths with a saw; these, after having been strung together, are often drawn through a draw-plate with round holes, to constitute chains which present an almost continu¬ ous cylindrical surface like round wire ; a very neat manufacture, invented in France. The teeth of saws are for the most part cut in the fly-press. Teeth, whether large or small, require but one punch, the sides of which meet at 60 degrees. Two studs are used to direct the edge of the blade for the saw to the punch, at the required angle de¬ pending on the pitch or inclination of the teeth, and an adjustable stop determines the space or interval from tooth to tooth, by catch¬ ing against the side of the last tooth previously made. Gullet teeth, and the various other kinds shown, require punches of their several compounded figures, and of different dimensions for each size of tooth. The teeth of circular saws are similarly punched out by mount¬ ing the perforated circular disk on a pin or axis, but in cutting the last six or eight teeth, it is needful to be watchful, so as to divide the remaining space into moderately equal parts. In cutting the teeth of circular saws not exceeding 12 inches diameter, Holtzapffel and Co. have been in the habit of mounting the steel plates on a spindle in a lathe with a dividing plate, and using a punch and bed fitted to a square socket fixed horizontally in the ordinary rest or support for the turning tool, the punch being driven through the plate by one revolution of a snail or cam, by means of a winch handle, and thrown back by a spring. In this arrangement the dividing plate insures the exact dimensions and equality of the teeth, which are rapidly and accurately cut. The copper caps for percussion guns are punched out in the form of a cross with short equal arms, or sometimes in a similar shape with only three arms, and the blanks, after having been annealed, are thrown out into form by means of dies, which fold up the arms and unite them to constitute the tubular part, whilst the central part of the metal forms the top of the cap that receives the com position and sustains the blow of the hammer. . Steel pens are another most prolific example of the result of the fly-press; they pass through the hands many times, and require to be submitted to the action of numerous dies, to five of which alone we shall advert. The blanks are cut by dies of the usual kind, so as in general to produce a flat piece of the exterior form of Fig. 359, page 384; the square mortise at the bottom of the slit is then punched through. The next process is usually to strike on the blanks the maker’s name. The slit is now cut by a thin chisel-like cutter, which makes an angular gap nearly through the steel, from that side of the metal intended to form the inner or concave part of the pen, and the act of curling up the pen into the channeled form, brings the angular 384 THE PRACTICAL METAL-WORKER’S ASSISTANT. side of the groove into contact, rendering the slit almost invisible. The slit, which is as yet only part way through the pen, is in general completed in the process of hardening, as the sudden transition into the cooling liquid generally causes the little portion yet solid to crack through, or else the slit remains unfinished until the moment the pen is pressed on the nail to open and ex¬ amine its nibs. Lariviere’s perforated plates for strainers, lanterns, meat safes, colanders, and numerous other articles, exhibit great delicacy and accuracy in the mode in which they are punched out. The tools are illustrated by the enlarged sections, Fig. 360. The punch con¬ sists of a plate of steel called the punch plate, which is in some cases pierced with only one single line of equidistant holes, that are countersunk on their upper extremities. Every hole is filled with a small cylindrical punch made of steel wire, the end of which is bumped up, or upset to form a head, that fills the chamfer in the punch plate, so that the punch cannot be drawn out by the work in the ascent of the press. The bed punch or matrix has a number of equidistant holes corresponding most exactly with the punches. In this case the holes in the work are punched out one line at a time, and between each descent of the punches the sheet of metal is shifted laterally by a screw slide until it is in proper position to receive the adjoining line of holes. At other times, the tool, instead of having only one line of punches, is wide, and entirely covered with several lines, so as to punch some hundreds or even thousands of holes at one time. For circular plates the punches are sometimes arranged in one radial line, but more usually the whole of the punches required for the fourth, sixth or eighth part of the circular disks are placed in the form of a sector, and the central hole, having been first 'punched, is made to serve as the guide for the four, six or eight positions at which these beautiful tools are applied. Many of the thin plates thus punched require to be strained like the head of a drum to keep the metal flat, in which case the metal is grasped between little clamps or vices around its four edges, and then stretched by appropriate screws and slides with which the apparatus is furnished, and the same mechanism prevents the metal from rising, and therefore fulfils the office of the puller-off com¬ monly used with punches. PUNCHES. 385 The construction of the tools above described calls for the great¬ est degree of precision. The drill employed to pierce the punch and matrix is of exceedingly small size in the finest perforated works, as it is said as many as six or seven hundred holes have been inserted in the length of six inches, which, considering the intervening spaces to be half as wide as the diameter of the holes, would make the latter of the minute size of only six-thousandths of an inch diameter. Such finely perforated metal appears to offer nearly the transparency of muslin, and is a manifest proof of the great skill displayed in the construction of the instruments, and in conducting the entire process. M. Marc Lariviere’s patent was granted 28th Nov., 1825, and is described in the Repertory of Patent Inventions, vol. iii., 3d series, page 182. All the foregoing examples of punched works suppose the punch to have been fixed to the follower of the press, and the matrix to the base of the same, in which case the bed punch requires to be very exactly adjusted by the set screws or dogs of the press. But it remains, in concluding this section, to advert to a different arrangement, in which the cutting tools are quite detached, and are far less liable to accident or fracture, even when the punches are of very large area and complicated figure, than when constructed in the ordinary manner with a shank, by which they are united to the follower of the press. Punches, to be used in this manner, for works with various de¬ tached apertures requiring any especial arrangement, and for various straggling and complicated objects, are constructed as shown in Figs. 362 to 364. There are two steel plates somewhat larger than the work, and from T 3 5 to f thick, the plates are hinged together like the leaves of a book, but are placed sufficiently distant to admit between them the work to be stamped out, and which is pinched between them by a thumb screw a. The two plates whilst folded together are perforated with all the apertures required in the work, which perforation may be either detached, continuous or arranged in any ornamental design that may be required. To all the apertures are fitted punches, which in length or vertical height are about one-eighth of an inch longer than the thickness of the upper plate, so as to stand up one-eighth when resting on the ma¬ terial to be punched, as seen in the partial section 364, in which the work is shaded obliquely and the punch vertically. As it would be difficult to fit the punches in one single piece to the ornamental or straggling parts of some devices, and as moreover such large and complicated punches would be almost sure to become distorted in the hardening, or broken when in use, the difficulty is boldly met by making the punch of as many small pieces as cir¬ cumstances may render desirable, but which pieces must, collectively fill up all the interstices of the plate. In using these punching tools, it is only necessary first to fix between the plates the metal to be pierced, then to insert all the 25 386 THE PRACTICAL METAL-WORKER’S ASSISTANT. punches into their respective apertures, and lastly to give the whole one blow between the flat disks of a powerful fly-press; this drives all the punches through the work, and leaves them flush with the upper surface. The whole is then removed from the press, and placed over an aperture in the work bench, and with a small drift and hammer the punches are driven out of the plates into a drawer beneath, and on the plates being separated, the work will be found to be exactly perforated to the same design as that of the tool itself; or with any part of the design instead of the whole, if part only of the punches were inserted in their respective places. The punches are selected from amidst the corresponding pieces of brass, which latter are laid on one side and the routine is recommenced. It is by this ingenious application of punches that the beautiful buhl works of the late Robert B. Henesey, of Holborn, London, were stamped. If a honeysuckle should be the device, the piece of brass is first placed between the plate and punched out, and pro¬ vided the punches are of the same length, the honeysuckle is re¬ moved in one piece although the punch may be in several; the wood is afterwards inserted, and is punched to exactly the same form, so that the brass honeysuckle will be found to fit in the most perfect manner, as it is an exact counterpart of the removed wood. The process is very economical and exact, but is only suited to large designs, because of the injury it would otherwise inflict on the wood, and on account of the expense of the tools, the mode is oniy proper for those patterns of which very large numbers are wanted ; whereas the buhl saw is not liable to these limitations, but is of universal, although less rapid application. Figs. 362 363 365 366. Cut brads and nails , or those which, instead of being forged, are cut out of sheet iron by machinery, constitute the last example it is proposed to advance in this section. Brads of the most simple kind, as in Fig. 365, have no heads, but are simply wedge form, and are cut out of strips of sheet iron, equal in width to the length of the brads: these strips are slit with circular shears, transversely from the ends of the sheets of iron, so that the fibre of the iron may run lengthways through the nails. When such brads are cut in the fly-press, the bed has a rectangu- PUNCHES. 387 lar mortise shown by the strong black line in Fig. 365, the punch is made rather long and rectangular so as exactly to fill the bed, but the last portion of the punch, say for half an inch of its length, is nicked in, or filed back exactly to the size and angle of the brad, as shown in the inverted plan, in which the shaded portion shows the reduced part or tail of the punch. The punch is never raised entirely out of the bed, in order that the strip of metal may be put so far over the hole in the bed as the tail of the punch will allow it, and also in contact with a stop or pin fixed to the bed, and in the descent of the punch its outer or rectangular edge moves the brad. The strip of metal is turned over between every descent of the press, so as to cut the head of the one brad from the point of that previously made, and the double guides afforded by the tail and stop enable this to be very quickly and truly done. The upper surface of the bed is not quite horizontal but a little inclined, so that the cutting may commence at the point of the brad, and thereby curl it less than if the tools met in absolute parallelism. In cutting brads that have heads, the general arrangements are somewhat different, as explained in the diagram Fig. 366, in which as before, the rectangular aperture in the bottom tool is bounded by the strong black line, the tail of the punch is shaded, the stop s, is situated as far beyond the aperture in the bed as the vertical height of the head, and it is so made that the small part which ex¬ tends to the right, overhangs the slip of iron that is being cut, after the manner of a puller-off; but the overhanging part only comes into action when the slip is tilted up, either by accident, or from being so short as to give an insufficient purchase for the hand. It is also to be observed that the width of the point of the brad is just equal to the projection of its head. On the end of the strip of iron being first applied, a wedge-form piece is cut off, exactly equal to the difference between the tail of the punch and the bed, and a little projection is left near s, and which projection, after the iron is turned over, rests against the tail of the punch, as shown in the figure, so that the succeeding cut re¬ moves the one brad and forms the head of the following; the tail of the punch being inclined to the precise angle drawn from the point to the head of the brad, as denoted in the diagram. When, as it is more usual, brads are cut out by steam-power, the cutters are not worked in a fly-press, but the moving cutter is com ■ monly fixed at the end of a long arm which is moved rapidly up and down by a crank; the strip of metal is held in a spring clamp, terminating in a long iron rod which rests in a Y or fork, so that the boy who attends the machine, can turn the metal over very rapidly between every alternation of the machine ; these particulars are shown in Fig. 353. The machine, Fig. 353, may be used for brads either with or without heads; it is, however, always necessary to turn the iron over between every cut; but in the toggle press, Fig. 352, and 388 THE PRACTICAL METAL-WORKER’S ASSISTANT. which acts much more quickly, it is not requisite to reverse the metal, as the entire press is moved on its pivots e e, by the rod g, so as to incline the press alternately to the right and left, to the angle of such nails as are simply wedge-form, or have no heads, as in Fig. 365, page 386. In some machines resembling Fig. 353, the nail as soon as cut off is grasped in a pair of forceps or dies, whilst a hammer, also moved by the machine, strikes a blow that upsets the metal, and constitutes the flat head in the kinds known as cut nails, and tacks. Punching Machinery used by Engineers.— After the re¬ marks offered on pages 364 to 367, on shearing tools, little remains to be said in this place on the punching machinery used by engi¬ neers, as it was there stated that the cutters for shearing and the punches, were most usually combined in the same machine; the punch being placed either at the outer extremity of the jointed lever, or at the bottom of the slide in those machines having rec¬ tilinear action. The punch is fixed to the slide or moving piece, the die is secured to the framing by means of four holding and ad¬ justing screws just as in fly-presses, and the puller ofl' or stop is likewise added, all which details are represented in the woodcuts on pages 365 and 366. The principal application of the engineer’s punching engine, is for making the rivet-holes around the edges of the plates of which steam-boilers, tanks, and iron ships are composed. Another im¬ portant use, and in which the punches trench upon the office of the shears, is in cutting out curvilinear parts and apertures or panels in boiler work, to which straight bladed shears cannot be applied. In this case the round punch is used in making a series of holes running into one another, along the particular line to be sheared through, or in other words the punch is used as a gouge, by which the hole that has been first formed, is extended by cutting away crescent-form pieces, thus leading the incision in any required direction. This employment of the punch to shearing curved lines, is also much used in cutting out the side plates of the framings of loco¬ motive engines, which consist of two pieces of stout boiler plate (the technical name for iron in sheets from £ to f inch thick), riveted alongside a central piece of wood, that is sometimes also covered above and below with iron, all the parts being united by rivets. The punching engine serves admirably for cutting out all the curved lines in these side plates, also the spaces where the bearings for the wheels are situated, and various apertures* Fig. 367 is a slotting and paring machine manufactured at the Lowell Machine Shop, Mass. The base plate and upright frame are of cast-iron. The tool bar moves by an adjustable crank of ten-inch stroke. It will range over a wheel of four feet diameter. Work may be executed by a circular or straight line movement. The tool is made self-acting, and inclines, when necessary, from a PUNCHES. 389 horizontal position to cut key grooves in tapering holes. The table apparatus is adjustable up and down in front of the frame by means of a rack, pinion worm, and worm-wheel. Fig. 367. In England the name of the inventor is suppressed of a very great improvement in the punching engine, as applied to making boilers and tanks, in which the rivet-holes are usually required to be made in straight lines, and at exactly equal distances, so that holes in two pieces punched separately may exactly correspond. The plate was fixed down upon a long rectilinear slide or car¬ riage, and during every ascent of the punch, was advanced by the machine itself, the interval from hole to hole, the moment after the punch was disengaged from the work. Subsequently 2, 3, or 4 punches were fixed at equal distances in the vertical slide, but the punches were made of unequal lengths, so that they came succes¬ sively into action, thereby dividing the strain, and the horizontal slide was consequently shifted every time, a distance equal to 2, 3, or 4 intervals. This machine, which displayed much ingenuity of invention, served as the foundation of the more simple punch¬ ing engines that are now met with. We believe the invention to be by M. Cavd of Paris. The following experiments were performed with a cast-iron lever, 11 feet long, multiplying the strain ten times, with a screw 390 THE PRACTICAL METAL-WORKER’S ASSISTANT. adjustment at the head, and a counterpoise. The sheets of iron and copper which were experimented upon, were placed between two perforated steel plates, and the punch, the nipple of which was perfectly flat on the face, being inserted into a hole in the upper plate, was driven through by the pressure of the lever. The average results of the several experiments (which are given in a detailed tabular form), show that the power required to force a punch half an inch diameter through copper and iron plates, is as follows: Iron plate 0.08 thick, required a pressure of 6,025 pounds. “ 0.17 “ « 11,950 “ 0.24 “ “ 17,100 “ Copper plate 0.08 “ “ 3,983 “ “ 0.17 “ “ 7,883 “ Hence it is evident that the force necessary to punch holes of different diameters through metal of various thicknesses, is directly as the diameter of the holes and the thickness of the metal. A simple rule for determining the force required for punching may be thus deduced. Taking one inch diameter and one inch in thick¬ ness as the units of calculation, it is shown that 150'00 is the con¬ stant number for wrought-iron plates, and 96'000 for copper plates. Multiply the constant number by the diameter in inches, and by the thickness in inches; the product is the pressure in pounds, that will be required to punch a hole of a given diameter through a plate of a given thickness. It was observed that the duration of pressure lessened consider¬ ably the ultimate force necessary to punch through metal, and that the use of oil on the punch reduced the pressure about 8 per cent. A drawing of the experimental lever and apparatus accompanied the communication. The second experiments were by means of a hydrostatic press having four cylinders in combination, punching through various pieces of iron ; the thickest of them measured 3 J inches thick, and from which was punched out a disk of 8 inches diameter, with a pressure of 2000 tons. The removed piece was rather thinner than the remainder and a little taper, which arose from the circumstance of the bolster hav¬ ing been purposely made with a flat bottom, and a little larger in diameter than the punch, so that the disk when removed was a little spread or flattened out. It is curious that experiments so distant from one another in their scale of proportion, should yet agree so nearly: The computed force is . . 150,000 x 8x 3i = 4,200,000 lbs. The actual force was . . . 2000 x 20 x 112 =4,480,000 lbs. Figure 368 is an upright drill, manufactured at the Lowell ma¬ chine shop, Lowell, Mass., and invented by W. B. Bennet, who has invented many other useful metal-worker’s tools. PUNCHES. 391 The base and frame are of cast-iron; the table that holds the work is elevated or depressed by a screw; the drill feeds down by hand; the drilling-shaft has four changes of speed, and geared Fig. 368. with iron cone pulleys. This instrument will drill a hole ten inches from the nearest edge of the object operated upon, and six inches deep. Fig. 369 is the Universal Drilling Machine, manufactured at the Lowell Machine Shop, Lowell, Mass., of which establishment Wm. A. Burke is superintendent. This machine is designed for drilling pieces of castings, which, from their size, cannot be operated upon by drilling machines of the ordinary kinds. It consists of a very strong upright frame or column, which carries upon its front side a heavy beam or arm, that can be moved out from the column to the distance of 8 feet. This beam has also a movement up or down of 6 feet, upon the front of the column. It also carries upon its extreme outer end the drill headstock. The spindle in this headstock is driven by means of bevel gears and shafts from the first driving shaft. A 392 THE PRACTICAL METAL-WORKER’S ASSISTANT. hole can be drilled in a piece 8 feet distant from the nearest side or edge, and a piece can be brought under the drill 6 feet in height. Fig. 369. The headstock and spindle are made adjustable, so that the whole can be drilled at any angle required, and ten inches deep. The driving shaft with cast-iron pulleys is attached to the frame. The machine is back geared, giving 8 different speeds to the drill. CHAPTER XXII. DRILLS. Drills for Metal, used by Hand. —The frequent necessity, in metal works, for the operation of drilling holes, which are re¬ quired of all sizes and various degrees of accuracy, has led to so very great a variety of modes of performing the process, that it is difficult to arrange with‘much order the more important of these methods and apparatus. The ordinary piercing drills for metal do not present quite so much variety as the wood drills. The drills for metal are mostly pointed; they consequently make conical holes, which cause the point of the drill to pursue the original line, and eventually to produce the cylindrical hole. The comparative feebleness of the drill-bow limits the size of the drills employed with it to about one-quarter of an inch in diameter; but as some of the tools used with the bow agree in kind with those of much larger dimensions, it will be convenient to consider as one group the forms of the edges of those drills which cut when moved in either direction. DRILLS. 393 Figs. 370, 371, and 372, represent, of tlieir largest sizes, the usual forms of drills proper for the reciprocating motion of the drill bow, because, their cutting edges being situated on the line of the axis, and chamfered on each side, they* cut, or rather scrape, with equal facility in both directions of motion. Fig. 370 is the ordinary double-cutting drill, the two facets forming each edge meet at an angle of about 50 to 70 degrees, and the two edges forming the point meet at about 80 to 100; but the watch-makers, who constantly employ this kind of drill, sometimes make the end as obtuse as an angle of about 120 degrees; the point does not then protrude through their thin works long before the completion of the hole. Fig. 371, with two circular chamfers, bores cast-iron more rapidly than any other reciprocating drill, but it requires an entry to be first made with a pointed drill. By some this kind is also preferred for wrought-iron and steel. The flat-ended drill, Fig. 372, is used for flattening the bottoms of holes. Fig. 373 is a duplex expanding drill, used by the cutlers for in¬ laying the little plates of metal in knife handles; the ends are drawn full size. Fig. 374 is also a double-cutting drill; the cylindrical wire is filed to the diametrical line, and the end is formed with two facets. This tool has the advantage of retaining the same diameter when it is sharpened. It is sometimes called the Swiss drill, and was employed by M. Le Riviere, for making the numerous small holes in the delicate punching machinery for manufacturing perforated sheets of metal and pasteboard. These drills are sometimes made either semi-circular or flat at the extremity. The square countersink, Fig. 375, is also used with the drill- bow ; it is made cylindrical, and pierced for the reception of a small central pin—after which it is sharpened to a chisel-edge, as shown. This countersink is in some measure a diminutive of the pin drills, Figs. 382 to 385 ; and occasionally circular collars are fitted on the pin for its temporary enlargement, or around the larger part to serve as a stop and limit the depth to which the countersink is allowed to penetrate, for inlaying the heads of screws. The pin is removed when the instrument is sharpened. By way of comparison with the double-cutting drills, the ordi- 394 THE PRACTICAL METAL-WORKER’S ASSISTANT. nary forms of those which only cut in one direction are shown in Figs. 376, 377, and 378. Fig. 376 is the common single cutting drill for the drill-bow, brace, and lathe. The point, as usual, is nearly a rectangle, but is formed by only two facets, which meet the sides at about 80° to 85° ; and therefore lie very nearly in con¬ tact with the extremity of the hole operated upon, thus strictly agreeing with the form of the turning tools for brass. Fig. 377 is a similar drill, particularly suitable for horn, tortoise-shell, and substances liable to agglutinate and clog the drill. The chamfers are rather more acute, and are continued around the edge behind its largest diameter, so that, if needful, the drill may also cut its way out of the hole. Fig. 378, although never used with the drill-bow, nor of so small a size as in the wood-cut, is added to show how completely the drill proper for iron, follows the character of the turning tools for that metal; the flute or hollow filed behind the edge, gives the hook- formed acute edge required in this tool, which is in other respects like Fig. 376; the form proper for the cutting edge is shown more distinctly in the diagram a, Fig. 382. Care should always be .taken to have a proportional degree of strength in the shafts of the drills, otherwise they tremble and chatter when at work or they occasionally twist oft* in the neck; the point should be also ground exactly central, so that both edges may cut. As a guide for the proportional thickness of the point, it may measure at b, Fig. 379, the base of the cone, about one-fifth the diameter of the hole, and at p, the point, about one- eighth, for easier penetration; but the fluted drills are made nearly of the same thickness at the point and base. In all the drills previously described, except Fig. 374, the size of the point is lessened each time of sharpening; but to avoid this loss of size, a small part is often made parallel, as shown in Fig. 379. In Fig. 380 this mode is extended by making the drill with a cylindrical lump, so as to fill the hole ; this is called the re-centering drill. It is used for commencing a small hole in a flat-bottomed cylindrical cavity; or else, in rotation with the common piercing drill, and the half-round bit. in drilling small and very deep holes DRILLS. 895 in the lathe. Fig. 3S0 may be also considered to resemble the stop-drill, upon which a solid lump or shoulder is formed, or a collar is temporarily attached by a side screw, for limiting the depth to which the tool can penetrate the work. Fig. 381, the cone countersink, may be viewed as a multiplication of the common single cutting drill. Sometimes, however, the tool is filed with four equi-distant radial furrows, directly upon the axis, and with several intermediate parallel furrows sweeping at an angle around the cone. This makes a more even distribution of the teeth, than when all are radial as in the figure, and it is always used in the spherical cutters, or countersinks, known as cherries, which are used in making bullet-moulds. On comparison, it may be said the single chamfered drill, Fig. 376, cuts more quickly than the double chamfered, Fig. 370, but that the former is also more disposed of the two to swerve or run from its intended position. In using the double cutting drills, it is also necessary to drill the holes at once to their full sizes, as otherwise the thin edges of these tools stick abruptly into the metal, and are liable to produce jagged or groovy surfaces, which destroy the circularity of the holes; the necessity for drilling the entire hole at once, joined to the feebleness of the drill-bow, limits the size of these drills. In using the single chamfered drills, it is customary, and on sev¬ eral accounts desirable, to make large holes by a series of two or more drills; first the run of the drill is in a measure proportioned to its diameter, therefore the small tool departs less from its in¬ tended path, and a central hole once obtained, it is followed with little after-risk by the single cutting drill, which is less penetra tive. This mode likewise throws out of action the less fa\or/Mo part of the drill near the point, and which in large drills is neces¬ sarily thick and obtuse; the subdivision of the work enables a comparatively small power to be used for drilling large holes, and also presents the choice of velocity best suited to each progressive diameter operated upon. But where sufficient power can be ob- 396 THE PRACTICAL METAL-WORKER’S ASSISTANT. tained, it is generally more judicious to enlarge the holes previ¬ ously made with the pointed drills, by some of the group of pin drills, Figs. 382 to 385, in which the guide principle is very per¬ fectly employed: they present a close analogy to the plug centre- bit, and the expanding centre-bit, used in carpentry. The ordinary pin-drill, Fig. 382, is employed for making counter¬ sinks for the heads of screw-bolts inlaid flush with the surface, and also for enlarging holes commenced with pointed drills, by a cut parallel with the surface; the pin-drill is also particularly suited to thin materials, as the point of the ordinary drill would soon pierce through, and leave the guidance less certain. When this tool is used for iron it is fluted as usual, and a represents the form of the one edge separately. Fig. 383 is a pin drill principally used for cutting out large holes in cast-iron and other plates. In this case the narrow cutter removes a ring of metal, which is of course a less laborious pro¬ cess than cutting the whole into shavings. When this drill is applied from both sides, it may be used for plates half an inch and upwards in thickness; as should not the tool penetrate the whole of the way through, the piece may be broken out, and the rough edges cleaned with a file or a broach. Fig. 384 is a tool commonly used for drilling the tube-plates for receiving the tubes of locomotive boilers; the material is about f inch thick, and the holes If diameter. The loose cutter a, is fitted in a transverse mortise, and secured by a wedge ; it admits of being several times ground, before the notch which guides the blade for centrality is obliterated. Fig. 385 is somewhat similar to the last two, but is principally intended for sinking grooves ; and when the tool is figured as shown by the dotted line, it may be used for cutting bosses and mouldings on parts of work not otherwise accessible. Many ingenious contrivances have been made to insure the dimensions and angles of tools being exactly retained. In this class may be placed O’Tool’s pin drill, Figs. 386 and 387 ; in action it resembles the fluted pin drill, Fig. 382, but the iron stock is Figs. 386 387. much heavier, and is attached to the drilling machine by the square tang; the stock has two grooves at an angle of about 10 degrees with the axis, and rather deeper behind than in front. Two steel cutters, or nearly parallel blades represented black, are laid in the grooves; they are fixed by the ring and two set screws, and DRILLS. 397 are advanced as they become worn away, by two adjusting screws, a a, (one only seen), placed at the angle of 10° through the second ring; which, for the convenience of construction, is screwed upon the drill shaft just beyond the square tang whereby it is attached to the drilling machine. The cutters are ground at the extreme ends, but they also require an occasional touch on the oilstone, to restore the keenness of the outer angles, which become somewhat rounded by the friction. The diminution from the trifling ex¬ terior sharpening, is allowed for by the slightly taper form of the blades. The process of drilling generally gives rise to more friction than that of turning, and the same methods of lubrication are used, but rather more commonly and plentifully ; thus oil is used for the generality of metals, or from economy, soap and water; milk is the most proper for copper, gold, and silver ; and cast-iron and brass are usually drilled without lubrication. For all the above-named metals and for alloys of similar degrees of hardness the common pointed steel drills are generally used; but for lead and very soft alloys, the carpenters’ spoon bits, and nose bits, are usually employed, with water. Having considered the most general forms of the cutting parts of drills, we will proceed to explain the modes in which they are put in action by hand-power, beginning with those for the smallest diameters, and proceeding gradually to the largest. Methods of working Drills by Hand-Power. —The smallest holes are those required in watch-work, and the general form of the drill is shown on a large scale in Fig. 888; it is made of a piece of steel wire, which is tapered off at the one end, flattened with the hammer, and then filled up in the form shown at large in Fig. 370 ; lastly, it is hardened in the candle. The reverse end of the instrument is made into a conical point, and is also hardened; near this end is attached a little brass sheave for the line of the drill- bow, which in watchmaking is sometimes a fine horse-hair, stretched by a piece of whalebone of about the size of a goose’s quill stripped of its feather Fig. 388. M The watchmaker holds most of his works in the fingers, both for fear of crushing them with the table vice, and also that he may the more sensibly feel his operations; drilling is likewise performed by him in the same manner. Having passed the bow-string around the pulley in a single loop (or with a round turn), the centre of the drill is inserted in one of the small centre holes in the sides of the table vice, the point of the drill is placed in the mark or cavity made in the work by the centre punch; the object is then pressed 398 THE PRACTICAL METAL-WORKER’S ASSISTANT. forward with the right hand, whilst the bow is moved with the left; the Swiss workmen apply the hands in the reverse order, as they do in using the turn-bench. Clockmakers, and artisans in works of similar scale, fix the ob¬ ject in the tail-vice, and use drills, such as Fig. 388, but often larger and longer; they are pressed forward by the chest, which is defended from injury by the breast-plate, namely, a piece of wood or metal about the size of the hand, in the middle of which is a plate of steel, with centre holes for the drill. The breast-plate is sometimes strapped round the waist, but is more usually supported with the left hand, the fingers of which are ready to catch the drill should it accidentally slip out of the centre. As the drill gets larger, the bow is proportionally increased in stiffness, and eventually becomes the half of a solid cone, about 1 inch in diameter at the larger end, and 30 inches long; the catgut string is sometimes nearly an eighth of an inch in diameter, or is replaced by a leather thong. The string is attached to the smaller end of the bow by a loop and notch, much the same as in the archery bow, and is passed through a hole at the larger end, and made fast with a knot; the surplus length is wound round the cane, and the cord finally passes through a notch at the end, which prevents it from uncoiling. Steel bows are also occasionally used; these are made something like a fencing foil, but with a hook at the end for the knot or loop of the cord, and with a ferrule or a ratchet, around which the spare cord is wound. Some variations also are made in the sheaves of the large drills; sometimes they are cylindrical, with a fillet at each end; this is desirable, as the cord necessarily lies on the sheave at an angle, in fact in the path of a screw; it pursues that path, and with the reciprocation of the drill-bow, the cord trav¬ erses, or screws backwards and forwards upon the sheave, but is prevented from sliding off by the fillet. Occasionally, indeed, the cylindrical sheave is cut with a screw coarse enough to receive the cord, which may then make three or four coils for increased purchase, and have its natural screw-like run without any fretting whatever; but this is only desirable when the holes are large, and the drill is almost constantly used,' as it is tedious to wind on the cord for each individual hole. The structure of the bows, breast¬ plates, and pulleys, although often varied, is sufficiently familiar to be understood without figures. When the shaft of the drill is moderately long, the workman can readily observe if the drill is square with the work as regards the horizontal plane; and to remove the necessity for the observa¬ tion of an assistant as to the vertical plane, a trifling weight is sometimes suspended from the drill shaft by a metal ring or hook; the joggling motion shifts the weight to the lower extremity; the tool is only horizontal when the weight remains central. In many cases, the necessity for repeating the shaft and pulley of the drill is avoided by the employment of holders of various DRILLS. 399 kinds, or drill-stocks, which serve to carry any required number of drill points. The most simple of the drill-stocks is shown in Fig. 389; it has the centre and pulley of the ordinary drill, but the op- Figs. 389 a ap¬ posite end is pierced with a nearly cylindrical hole, just at the inner extremity of which a diametrical notch is filed. The drill is shown separately at a ; its shank is made cylindrical, or exactly to fit the hole, and a short portion is nicked down also to the diamet¬ rical line so as to slide into the gap in the drill-stock, by which the drill is prevented from revolving: the end serves also as an abutment, whereby it may be thrust out with a lever. Sometimes a diametrical transverse mortise, narrower than the hole, is made through the d rill-stock, and the drill is nicked in on both sides; and the designer, Mr. B. Balfe, of Kilkenny, proposes that the cylindrical hole of 389 should be continued to the bottom of the notch, that the end of the drill should be filed off obliquely, and that it should be prevented from rotating by a pin inserted through the cylindrical hole parallel with the notch; the taper end of the drill would then wedge fast beneath the pin. Drills are also frequently used in the drilling-lathe; this is a miniature lathe-head, the frame of which is fixed in the table vice; the mandrel is pierced for the drills, and has a pulley for the bow, therein resembling Fig. 390, except that it is used as a fixture. The figure 390, just referred to, represents one variety of another common form of the drill-stock, in which the revolving spindle is fitted in a handle, so that it may be held in any position without the necessity for the breast-plate; the handle is hollowed out to serve for containing the drills, and is fluted to assist the grasp. 400 THE PRACTICAL METAL-WORKER’S ASSISTANT. Fig. 391 represents the socket of an “universal drill-stock ,” in¬ vented by James O’Kyan: it is pierced with a hole as large as the largest of the wires of which the drills are formed, and the hole terminates in an acute hollow cone. The end of the drill-stock is tapped with two holes, placed on a diameter; the one screw, a, is of a very fine thread, and has at the, end two shallow diametrical notches; the other, b, is of a coarser thread, and quite flat at the extremity. The wire-drill is placed against the bottom of the hole, and allowed to lean against the adjusting-screw a, and if the drill be not central, this screw is moved one or several quarter-turns, until it is adjusted for centrality ; after which the tool is strongly fixed by the plain set-screw b. Fig. 392 is a drill-stock contrived by Mr. Murphy. It consists of a tube, the one end of which has a fixed centre and pulley, much the same as usual. The opposite end of the tube has a piece of steel fixed into it which is first drilled with a central hole, and then turned as a conical screw, to which is fitted a corresponding screw nut, n ; the socket is then sawn down with two diametrical notches, to make four internal angles ; and lastly, the socket is hardened. When the four sections are compressed by the nut, their edges stick into the drill and retain it fast, and, provided the instrument is itself concentric, and the four parts are of equal strength, the centrality of the drill is at once insured. The out¬ side of the nut, and the square hole in the key k, are each taper, for more ready application; and the drills are of the most simple kind, namely, lengths of wire pointed at each end, as in Fig. 393. The sketch, Fig. 392, is also intended to explain another useful application of this drill-stock as an upright or pump-drill, well known among the ancient Irish as the breast-drill. Occasionally the pump-drill and the common drill-stock are mounted in frames, by which their paths are more exactly defined; but these con¬ trivances are far from being generally required, and enough will be said in reference to the use of revolving braces, to lead to such applications, if considered requisite, for reciprocating drills. Holes that are too large to be drilled solely by the breast-drill and drill-bow, are frequently commenced with those useful instru¬ ments, and are then enlarged by means of the hand-brace, which is very similar to that used in carpentry, except that it is more commonly made of iron instead of wood, is somewhat larger, and generally made without the spring-catch. Holes may be extended to about half an inch diameter with the hand-brace; but it is much more expeditious to employ still larger and stronger braces, and to press them into the work in various ways by weights, levers, and screws, instead of by the muscular effort alone. Fig. 394 represents the old smith’s press-drill, which although cumbrous and much less used than formerly, is nevertheless simple and effective. It consists of two pairs of wooden standards, be DRILLS. 401 tween which, works the beam a b, the pin near a is placed at any height, but the weight w is not usually changed, as the greater or Figs. 394 395. less pressure for large and small drills is obtained by placing the brace more or less near to the fulcrum a ; and this part of the beam is shod with an iron plate full of small centre holes for the brace. The weight is raised by the second lever c d, the two being united by a chain, and a light chain or rope is also suspended from d, to be within reach of the one or two men engaged in moving the brace. It is necessary to relieve the weight when the drill is nearly through the hole, otherwise it might suddenly break through, and the drill becoming fixed, might be twisted off in the neck. The inconveniences in this machine are, that the upper point of the brace moves in an arc instead of a right line; the limited path when strong pressures are used, which makes it necessary to shift the fulcrum a ; and also the necessity for re-adjusting the work under the drill for each different hole, which in awkwardly-shaped pieces is often troublesome. A portable contrivance, of similar date, is an iron bow frame or clamp, shown in Fig. 395. The pressure is applied by a screw, but in almost all cases, whilst the one individual drills the hole, the assistance of another is required to hold the frame ; 395 only applies to comparatively thin parallel works, and does not present the necessary choice of position. Another tool of this kind, used for boring the side holes in cast-iron pipes for water and gas, is doubtless familiarly known; the cramp or frame divides into two branches about two feet apart, and these terminate like hooks, which loosely embrace the pipe, so that the tool retains its position without constraint, and it may be used with great facility by one individual. Fig. 396 will serve to show the general character of various con¬ structions of more modern apparatus, to be used for supplying the pressure in drilling holes with hand braces. It consists of a cylin¬ drical bar a, upon which the horizontal rectangular rod b is fitted with a socket, so that it may be fixed at any height, or in any angular position, by the set-screw c. Upon b slides a socket, which 26 402 THE PRACTICAL METAL-WORKER’S ASSISTANT. is fixed at all distances from a by its set-screw d ; and lastly, this socket has a long vertical screw e, by which the brace is thrust into the work. The object to be drilled having been placed level, either upon the ground, on trestles, on the work bench, or in the vice, according to circumstances, the screws c and d are loosened, and the brace is put in position for work. The perpendicularity of the brace is then examined with a plumb-line, ap¬ plied in two positions (the eye being first directed as it were along the north and south line, and then along the east and west), after which the whole is made fast by the screws c and d. The one hole having been drilled, the socket and screws present great facility in re-adjusting the in¬ strument for subsequent holes without the necessity for shifting the work, which would generally be attended with more trouble than altering the drill-frame by its screws. Sometimes the rod a is rectangular, and extends from the floor to the ceiling; it then traverses in fixed sockets, the lower of which has a set screw for retaining any required position. In the tool represented, the rod a terminates in a cast-iron base, by which it may be grasped in the tail-vice, or when required it may be fixed upon the bench; in this case the nut a is unscrewed, the cast-iron plate, when reversed and placed on the bench, serves as a pedestal, the stem is passed through a hole in the bench, and the nut and washer, when screwed on the stem beneath, secure all very strongly together. Even in establishments where the most complete drill¬ ing machines driven by power are at hand, modifications of the press drill are among the indispensable tools: many are contrived with screws and clamps, by which they are attached directly to such works as are sufficiently large and massive to serve as a foundation. Various useful drilling tools for engineering works are fitted with left hand screws, the unwinding of which elongate the tools; so that for these instruments which supply thtiir own pressure, it is only necessary to find a solid support for the centre They apply very readily in drilling holes within boxes and panels, and the abutment is often similarly provided by projecting parts of the castings; or otherwise the fixed support is derived from the wall or ceiling, by aid of props arranged in the most convenient manner that presents itself. Eig. 397 is the common brace, which only differs from that in Fig. 396. DRILLS. 403 Fig. 396 in the left hand screw; a right hand screw would be un¬ wound in the act of drilling a hole when the brace is moved round in the usual direction, which agrees with the path of a left hand screw. The cutting motion produces no change in the length of the instrument, and the screw being held at rest for a moment during the revolution, sets in the cut; but towards the last, the feed is discontinued, as the elasticity of the brace and work suffice for the reduced pressure required when the drill is nearly through, and sometimes the screw is unwound still more to reduce it. The lever-drill, Fig. 398, differs from the latter figure in many respects ; it is much stronger, and applicable to larger holes; the drill socket is sufficiently long to be cut Into the left hand screw, and the piece serving as the screwed nut, is a loop terminating in the centre point. The increased length of the lever gives much greater purchase than in the crank-formed bra-ce, and in addition the lever-brace may be applied close against a surface where the crank-brace cannot be turned round; in this case the lever is only moved a half circle at a time, and is then slid through for a new purchase, or sometimes a spanner or wrench is applied directly upon the square drill socket. Figs. 397 400 The same end is more conveniently fulfilled by the ratchet-drill, Fig. 399, apparently derived from the last: it is made by cutting ratchet teeth in the drill shaft, or putting on the rachet as a sepa¬ rate piece, and fixing a pall or detent to the handle; the latter may then be moved backward to gather up the teeth, and forward to thrust round the tool, with less delay than the lever in Fig. 398, and with the same power, the two being of equal length. This tool is also peculiarly applicable to reaching into angles and places in which neither the crank-form brace, nor the lever-drill will apply. Fig. 400, the ratchet-lever, in part resembles the ratchet- drill, but the pressure-screw of the latter instrument must oe 404 THE PRACTICAL METAL-WORKER’S ASSISTANT. sought in some of the other contrivances referred to, as the rat¬ chet-lever has simply a square aperture to fit on the tang of the drill d, which latter must be pressed forward by some independent means. Fig. 401, which is a simple but necessary addition to the braces and drill tools, is a socket having at one end a square hole to re¬ ceive the drills, and at the opposite, a square tang to fit the brace; by this contrivance the length of the drill can be temporarily ex¬ tended for reaching deeply seated holes. The sockets are made of various lengths, and sometimes two or three are used together, to extend the length of the brace to suit the position of the prop ; but it must be remembered that, with the additional length, the torsion becomes much increased, and the resistance to end-long pressure much diminished, therefore the sockets should have a bulk proportionate to their length. The French brace is also constructed in iron, with a pair of equal bevel pinions, and a left hand centre screw, like the tools Figs. 397, 398, and 399 ; it is then called the corner-drill. Some¬ times also, as in Figs. 402 and 403, the bevel wheels are made with a hollovf square or axis, as in the ratchet-lever, Fig. 400; the driver then hangs loosely on the square shank of the drill tool, or cutter bar, and when the pinion on the handle is only one-third or fourth of the size of the bevel wheel with the square hole, it is an effective driver for various uses; the long tail or lever serves to prevent the rotation of the driver, by resting against some part of the work or of the work-bench. Fig. 402 Fig. 403. All the before-mentioned tools are commonly found in a variety of shapes in the hands of the engineer, but it will be observed they are all driven by hand power, and are carried to the work. I shall conclude this section with the description of a more recent drill tool of the same kind, invented by Mr. O’Kelly of Dublin. DRILLS. 405 This instrument is represented of one-eighth size, in the side view, Fig. 404, in the front view, 405, and in the section, 406; it is about twice as powerful as Fig. 403, and has the advantage of feed¬ ing the cut by a differential motion. The tangent screw moves at the same time the two worm wheels a and b ; the former has 15 teeth, and serves to revolve the drill; the latter has 16 teeth, and by the difference between the two, or the odd tooth, advances the drill slowly and continually, which may be thus explained. The lower wheel a, of 15 teeth, is fixed on the drill shaft, and this is tapped to receive the centre screw c, of four threads per inch. The upper wheel of 16 teeth is at the end of a socket d. (which is represented black in the section Fig. 406), and is con¬ nected with the centre screw c, by a collar and internal key, which last fits a longitudinal groove cut up the side of the screw c; now, therefore, the internal and external screws travel constantly round, and nearly at the same rate, the difference of one tooth in the wheels serving continually and slowly to project the screw c, for feeding the cut. To shorten or lengthen the instrument rapidly, the side screw e is loosened; this sets the collar and key free from the 16 wheel, and the centre screw may for the time be moved in¬ dependently by a spanner. Fig* 404 405 406. The differential screw-drill, having a double thread in the large worm, shown detached at /, requires 7| turns of the handle to move the drill once round, and the feed is one 64th of an inch for each turn of the drill; that being the sum of 16 by 4. Drilling and Boring Machines.— The motion of the lathe mandrel is particularly proper for giving action to the various single-cutting drills referred to; they are then fixed in square or round hole drill-chucks which screw upon the lathe mandrel. The motion of the lathe is more uniform than that of the hand tools, and the popit-head, with its flat boring flange and pressure screw, forms a most convenient arrangement, as the works are then carried to the drill exactly at right angles to the face. But in drilling very small holes in the lathe, there is some risk of uncon¬ sciously employing a greater pressure 'with the screw than the 406 TOE PRACTICAL METAL-WORKERS ASSISTANT. slender drills will bear. Sometimes the cylinder is pressed for ward by a horizontal lever fixed on a fulcrum; at other times the cylin¬ der is pressed forward by a spring, by a rack and pinion motion, or by a simple lever, and the best arrangement of this latter kind is that next to be described. In the manufacture of harps there is a vast quantity of small drilling, and the pressure of the cylinder popit-head is given by means of a long, straight, double ended lever, wdiich moves hori¬ zontally (at about one-third from the back extremity), upon a fixed post or fulcrum erected upon the back-board of the lathe. The front of the lever is connected with the sliding cylinder by a link or connecting rod, and the back of the lever is pulled towards the right extremity of the lathe, by a cord which passes over a pulley at the edge of the back-board, and then supports a weight of about twenty pounds. Both the weight and connecting rod may be attached at various distances from the fixed fulcrum between them. When they are fixed at equal distances from the axis of the lever, the weight, if twenty pounds, presses forward the drill with twenty pounds, less a little friction; if the wmight be two inches from the fulcrum and the connecting rod eight inches, the effect of the weight is reduced to five pounds; if, on the other hand, the weight be at eight and the connecting rod at two inches, the pressure is fourfold, or eighty pounds. The connecting rod is full of holes, so that the lever may be ad¬ justed exactly to reach the body of the workman, who standing w ith his face to the mandrel, moves the lever with his back, and has therefore both hands at liberty for managing the w r ork. Some¬ times a stop is fixed on the cylinder, for drilling holes to one fixed depth; gages are attached to the flange, for drilling numbers of similar pieces at any fixed distance from the edge: in fact, this very useful apparatus admits of many little additions to facilitate the use of drills and revolving cutters. Great numbers of circular objects, such as wheels and pulleys, are chucked to revolve truly upon the lathe mandrel, whilst a sta¬ tionary drill is thrust forward against them, by which means the concentricity between the hole and the edge is insured. The drills employed for boring works chucked on the lathe, have mostly long shafts, some parts of which are rectangular or parallel, so that they may be prevented from revolving by a hook wrench, a spanner or a hand-vice, applied as a radius, or by other means. The ends of the drill shafts are pierced with small centre holes, in order that they may be thrust forward by the screw of the popit- head, either by hand or by self-acting motion: namely, a connection between either the mandrel or the prime mover of the lathe, and the screw of the popit-head, by cords and pulleys, by wheels and pinions, or other contrivances. The drills, Figs. 376 and 378, p. 394, are used for boring ordinary holes: but for those requiring greater accuracy, or a more exact DRILLS. 407 repetition of the same diameter, the lathe drills, Figs. 407 to 409 are commonly selected. Fig. 407, which is drawn in three views and to the same scale as the former examples, is called the half- round hit, or the cylinder hit. The extremity is ground a little in¬ clined to the right angle, both horizontally and vertically, to about the extent of three to five degrees. It is necessary to turn out a shallow recess exactly to the diameter of the end of the bit as a commencement; the circular part of the bit fills the hole, and is thereby retained central, whilst the left angle removes the shaving. This tool should never be sharpened on its diametrical face, or it would soon cease to deserve its appellation of half-round bit: some indeed give it about one-thirtieth more *of the circumference. It is generally made very slightly smaller behind, to lessen the friction; and the angle, not intended to cut, is a little blunted half-way round the curve, that it may not scratch the hole from the pressure of the cutting edge. It is lubricated with oil for the metals generally, but is used dry for hard woods and ivory, and sometimes for brass. The rose-bit, Fig. 408, is also very much used for light finishing cuts, in brass, iron, and steel; the extremity is cylindrical, or in the smallest degree less behind, and the end is cut into teeth like a countersink; the rose-bit, when it has plenty of oil, and but very little to remove, will be found to act beautifully, but this tool is less fit for cast-iron than the bit next to be described. The rose-bit may be used without oil for the hard woods and ivory, in which it makes a very clean hole; but as the end of the tool is chamfered, it does not leave a flat-bottomed recess the same as the half-round bit, and is therefore only used for thoroughfare holes. Figs. 407 408 409 410 411. The drill, Fig. 409, is much employed, but especially for cast- iron work; the end of the blade is made very nearly parallel, the two front corners are ground slightly rounding, and are chamfered, the chamfer is continued at a reduced angle along the two sides, to the extent of about two diameters in length: this portion is not 108 THE PRACTICAL METAL-WORKER’S ASSISTANT. strictly parallel, but is very slightly largest in the middle or barrel- shaped : this drill is used dry for cast-iron. Fig. 409, in common with all drills that cht on the side, may, by improper direction, cut sideways, making the hole above the in¬ tended diameter; but when the hole has been roughly bored with a common fluted drill, the end of the latter is used as a turning tool, to make an accurate chamfer, the bit 409 is then placed through the stay, as shown in Fig. 410, and is lightly supported between the chamfer upon the work and the centre of the popit-head; the moment any pressure comes on the drill, its opposite edges stick into the inner sides of the loop (as more clearly explained in Fig. 411), which thus restrains its position; much the same as the point and edges of the turning tools for iron dig into the rest, and secure the position of those tools. It is requisite the drill and loop should be exactly central; Fig. 410 shows the common form of the stay when fitted to the lathe rest, but it is sometimes made as a swing gate, to turn aside, whilst the piece which has been drilled is removed, and the next piece to be operated upon is fixed in the lathe. Sometimes also the drill 409 has blocks of hardwood attached above and below it, to com¬ plete the circle; this is usual for wrought-iron and steel, and oil is then employed. These three varieties are exclusively lathe-drills, and are in¬ tended for the exact repetition of a number of holes of the par¬ ticular sizes of the bits, and which, on that account, should remove only a thin shaving to save the tools from wear. The cylinder bits, however, may be used for enlarging holes below half an inch, to the extent of about one-third their diameter at one cut; and for holes from half an inch to one inch, about one-fourth their diameter or less, and as the bits increase in size, the proportion of the cut to the diameter should decrease. The cylinder bit is not intended to be used for drilling holes in the solid material, and as the piercing drills are apt to swerve in drilling small and very deep holes, the following rotation in the tools is sometimes resorted to. A drill, Fig. 376, p. 394, say three- sixteenths diameter, is first sent into the depth of an inch or up¬ wards, and the hole is enlarged by a cylinder' bit of one-quarter inch diameter. The centre at the end of the hole is then restored to exact truth, by Fig. 380, a re-centering drill, the plug of which exactly fits the hole made by the cylinder bit; the extremity of the re-centering drill then acts as a fixed turning tool, and should the first drill have run out of its position, Fig. 380 corrects the centre at the end of the hole. Another short portion is then drilled with Fig. 376, enlarged with the half-round bit, and the conical extremity is again corrected with the re-centering drill; the three tools are thus used in rotation until the hole is completed, and which may be then cleaned out with one continued cut, made with a half-round bit a little larger than that previously used. Some of the large half-round bits are so made that the one stock DRILLS. 409 will serve for several cutters of different diameters. In the bits used for boring out ordnance, the parallel shaft of the boring bar slides accurately in a groove, exactly parallel witli the bore of the gun; the cutting blade is a small piece of steel affixed to the end of the half-round block, which is either entirely of iron, or partly of wood; and the cut is advanced by a rack and pinion move¬ ment, actuated either by the descent of a constant weight, or by a self-acting motion derived from the prime mover. For making the spherical, parabolical or other termination to the bore, cutters of corresponding forms are fixed to the bar. The outside of the gun is usually turned, whilst the boring is going on, by hand tools. A plug of copper is screwed into the brass guns to be perforated for the touch-hole, copper being less injured by repeated discharges, than the alloy of nine parts copper and one part tin, used for the general substance of the gun; the curved bit smooths off the end of the plug. There are very many works which from their weight or size, cannot be drilled in the lathe in its ordinary position, as it is scarcely possible to support them steadily against the drill; but these works are readily pierced in the drilling machine, which may be viewed as a lathe with a vertical mandrel, and with the flange of the popit-head, enlarged into a table for the work, which then lies in the horizontal position simply by gravity, or is occasionally fixed on the table by screws and clamps. The structure of these important machines admits of almost endless diversity, and in nearly every manufactory some peculiarity of construction may be observed. Figs. 412 and 413, exhibit a “Portable Hand-drill,” which is introduced as a simple and efficient example, that may serve to Figs. 412 413. convey the general characters of the drilling machines. The spindle is driven by a pair of bevel pinions, the one is attached to the axis of the vertical fly-wheel, the other to the drill shaft, which is depressed by a screw moved by a small hand-wheel. Sometimes, as in the lathe, the drilling spindle revolves without 410 THE PRACTICAL METAL-WORKER’S ASSISTANT. endlong motion, and the table is raised by a treadle or by a hand lever ; but more generally the drill-shaft is cylindrical and revolves in, and also slides through fixed cylindrical bearings. The drill spindle is then depressed in a variety of ways; sometimes by a simple lever, at other times by a treadle, which either lowers the shaft only one single sweep, or by a ratchet that brings it down by several small successive steps, through a greater distance; and mostly a counterpoise weight restores the parts to their first posi¬ tion when the hand or foot is removed. Friction clutches, trains of differential wheels, and other modes are also used in depressing the drill spindle, or in elevating the table by self-acting motion. Frequently also the platform admits of an adjustment independent of that of the spindle, for the sake of admitting larger pieces; the horizontal position of the platform is then retained by a slide, to which a rack and pinion movement, or an elevating screw is added. Drilling machines of these kinds are generally used with the ordinary piercing drills, and occasionally with pin drills; the latter instrument appears to be the type of another class of boring tools, namely, cutter bars, which are used for works requiring holes of greater dimensions, or of superior accuracy, than can be attained by the ordinary pointed drills. The small application of this principle, or of cutter bars, is shown on the same scale as the former drills, in Fig. 414; the cutter is placed in a diametrical mortise in a cylindrical boring bar, and is fixed by a wedge; the cutter extends equally on both sides, as the two projections or ears embrace the sides of the bar, which is slightly flattened near the mortises. Cutter bars of the same kind are occasionally employed with cutters of a variety of forms, for making grooves, recesses, mould¬ ings, and even screws, upon parts of heavy works, and those which cannot be conveniently fixed in the ordinary lathe. Fig. 415 repre¬ sents one of these, but its application to screws will be found in the chapter on the tools for screw cutting. Figs. 414 416 415 The larger application of this principle is shown in Fig. 415, in which a cast-iron cutter-block is keyed fast upon a cylindrical bar; the block has four, six, or more grooves in its periphery. Some- DRILLS. 411 times, tlie work is done with only one cutter, and should the bar vibrate, the remainder of the grooves are filled with pieces of hard wood, so as to complete the bearing at so many points of the circle; occasionally cutters are placed in all the grooves, and carefully adjusted to act in succession, that is, the first stands a little nearer to the axis than the second, and so on throughout, in order that each may do its share of work; but the last of the series takes only a light finishing cut, that its keen edge may be the longer pre¬ served. In all these cutters, the one face is radial, the other dif¬ fers only four or five degrees from the right angle, and the cor¬ ners of the tools are slightly rounded. These cutter bars, like the rest of the drilling and boring machin¬ ery, are employed in a great variety of ways, but which resolve themselves into three principal modes: First, the cutter bar revolves without endlong motion, in fixed centres or bearings, in fact, as a spindle in the lathe; the work is traversed, or made to pass the revolving cutter in a right line, for which end the work is often fixed to a traversing slide rest. This mode requires the bar to measure between the supports, twice the length of the work to be bored, and the cutter to be in the middle of the bar; it is therefore unfit for long objects. Secondly, the cutter bar revolves, and also slides with endlong motion, the work being at rest; the bearings of the bar are then frequently attached in some temporary manner to the work to be bored, and are often of wood. Cylinders of forty inches diameter for steam-engines, have been thus bored, by attaching a cast-iron cross to each end of the cylinder; the crosses are bored exactly to fit the boring bar, one of them carries the driving gear, and the bar is thrust endlong by means of a screw, moved by a ratchet or star wheel. In another common arrangement, the boring bar is mounted in headstocks, much the same as a traversing mandrel, the work is fixed to the bearers carrying the headstocks, and the cutter bar is advanced by a screw. The screw is then moved either by the hand of the workman; by a star-wheel, or a ratchet wheel, one tooth only in each revolution; or else by a system of differential wheels, in which the external screw has a wheel say of 50 teeth, the internal screw a wheel of 51 teeth, and a pair of equal wheels or pinions drives these two screws continually, so that the ad¬ vance of the one-fiftieth of the turn of the screw, or their differ¬ ence, is equally divided over each revolution of the cutter bar, much the same as in the differential motion of the screw drill, Fig. 404. This second method only requires the interval between the fixed bearings of the cutter bar to be as much longer than the work as the length of the cutter-block; but the bar itself must have more than twice the length of the work, and requires to slide through the supports. Cutter bars of this kind are likewise used in the lathe; in the 412 THE PRACTICAL METAL-WORKER’S ASSISTANT. act of boring, the end of tlie bar then slides like a piston into the mandrel. Such bars are commonly applied to the vertical boring machines of the larger kinds, which are usually fitted with a dif¬ ferential apparatus, for determining the progress of the cut; the bar then slides through a collar fixed in the bed of the machine. In some of the large boring machines either one or two hori- zontal slides are added, and by their aid series of holes may be bored in any required arrangement. For instance, the several holes in the beams, or side levers, and cranks of steam-engines, are bored exactly perpendicular, in a line, and at any precise distances, by shifting the work beneath the revolving spindle upon the guide or railway; in pieces of other kinds, the work is moved laterally during the revolution of the cutters, for the formation of elongated countersinks and grooves. Thirdly. In the largest applications of this principle, the boring bar revolves upon fixed bearings without traversing; and it is only needful that the boring bar should exceed the length of the work, by the thickness of the cutter block, of which it has com¬ monly several of different diameters. *The cutter block, now some¬ times ten feet diameter, traverses as a slide down a huge boring bar, whose diameter is about thirty inches. There is a groove and key to couple them together, and the traverse‘of the cut¬ ter block down the bar is caused by a side screw, upon the end of which is a large wheel, that engages in a small pinion, fixed to the stationary centre or pedestal of the machine. With every revolution of the cutter bar, the great wheel is carried around the fixed pinion, and supposing these be as ten to one, the great wheel is moved one-tenth of a turn, and therefore moves the screw one-tenth of a turn also, and slowly trav¬ erses the cutter block. The contrivance may be viewed as a huge, self-acting, and re¬ volving sliding-rest, and the diagram 417 shows that the cutter bars are equally applicable to portions. of circles, such as the D valves of steam-engines, as well as to the enormous interior of the cylinder itself. All the preceding boring tools cut almost exclusively upon the end alone. They are passed entirely through the objects, and leave each part of their own particular diameter, and therefore cylindrical ; but I now proceed to describe other boring tools, that cut only on their sides, go but partly through the work, and leave its section a counterpart of the instrument. These tools are gen¬ erally conical, and serve for the enlargement of holes to sizes intermediate between the gradations of the drills, and also for the formation of conical holes, as for valves, stopcocks, and other Fig. 417. DRILLS. 413 work 3 . The common pointed drill, or its multiplication in the rose countersink, is the type of the series; but in general the broaches have sides which are much more nearly parallel. Broaches for making Taper Holes. —The tools for making taper holes are much less varied than the drills and boring tools for cylindrical holes. Figs. 418 419 420 421 422 423 425. The broaches for metal are made solid, and of various section s; as half-round, like Fig. 418; the edges are then rectangular, but more commonly the broaches are polygonal, as in Fig. 419, except that they have 3, 4, 5, 6, and 8 sides, and their edges measure respectively 60, 90, 108, 120, and 135 degrees. The four, five, and six-sided broaches are the most general, and the watchmakers em¬ ploy a round broach in which no angle exists, and the tool is therefore only a burnisher, which compresses the metal and rounds the hole. Ordinary broaches are very acute, and Fig. 425 may be consid¬ ered to represent the general angle at which their sides meet, namely, less than one or two degrees; the end is usually chamfered off with as many facets as there are sides, to make a penetrating point, and the opposite extremity ends in a square tang, or shank, by which the instrument is worked. Square broaches, after having been filed up, are sometimes twisted whilst red-hot; Fig. 424 shows one of these ; the rectan¬ gular section is but little disturbed, although the faces become slightly concave. The advantage of the tool appears to exist in its screw form: when it is turned in the direction of the spiral, it cuts with avidity and requires but little pressure, as it is almost disposed to dig too forcibly into the metal: when turned the re¬ verse way, as in unscrewing, it requires as much or more pressure than similar broaches not twisted. This instrument, if bent in the direction of its length, either in the act of twisting or hardening, does not admit of correction by grinding, like those broaches hav¬ ing plane faces. It is not much used, and is almost restricted to wrought-iron and steel. Large countersinks that do not terminate in a point, are some¬ times made as solid cones; a groove is then formed up one side, and deepest towards the "base of the cone, for the insertion of a cutter; see Fig. 420. As the blade is narrowed by sharpening, it 414 THE PRACTICAL METAL-WORKER’S ASSISTANT. is set a little forward in the direction of its length, to cause its edge to continue slightly in advance of the general surface, like the iron of a plane for cutting metal. Figure 426 represents the broach, invented by James Kinse- laugh, of Wicklow, Ireland, in which four detached blades are intro¬ duced, for the sake of retaining the cone or angle of the broach Fig. 426. with greater facility. The bar or stack has four shallow longitud¬ inal grooves, which are nearly radial on the cutting face, and slightly undercut on the other. The grooves are also rather deeper behind, and the blades are a little wedge-form both in sec¬ tion and in length, to constitute the cone, and the cutting edges. In restoring the edges of the blades, they are removed from the stock, and their angles are then more easily tested : when replaced, they are set nearer to the point, to compensate for their loss of thickness. Broaches are also used for perfecting cylindrical holes, as well as for making those which are taper. The broaches are then made almost parallel, or a very little the highest in the middle ; they are hied, with two or three planes at angles of 90 degrees, as in Figs. 421 or 422. The circular part not being able to cut, serves as a more certain base or foundation, than when the tool is a complete polygon ; and the stems are commonly made small enough to pass entirely through the holes, which then agree very exactly as to size. Such tools are therefore rather entitled to the name of finish¬ ing drills, than broaches. The size of the parallel broaches is often slightly increased by placing a piece or two of paper at the convex part. Leather and thin metal are also used for the same purpose. Gun-barrels are broached with square broaches, the cutting parts of which are about eight to ten inches long ; they are packed on the four sides with slips or spills of wood to complete the circle, as in Fig. 423, in which the tool is supposed to be at work. The size of the bit is progressively enlarged by introducing slips of thin paper, piece by piece, between two of the spills of wood and the broach; the paper throws the one angle more towards the centre of the hole, and causes a corresponding advance in the opposite or the cutting angle. Sometimes, however, only one spill of wood is employed. A broach used by the philosophical instrument-makers in finish¬ ing the barrels of air-pumps, consisted of a thin plate of steel in¬ serted diametrically between two blocks of wood, the whole con¬ stituting a cylinder with a scraping edge slightly in advance of the wood. Slips of paper were also added. According to the size of the broaches, they are fixed in handles DRILLS. 415 like brad-awls; they are used in tlie brace, or tlie tap wrench, namely, a double-ended lever with square central holes. Some¬ times also broaches are used in the lathe just like drills, and for large works broaching machines are employed. These are little more than driving gear terminating in a simple kind of universal joint to lead the power of the steam-engine to the tool, which is generally left under the guidance of its own edges, according to the common principle of the instrument. In drills and broaches the penetrating angles are commonly more obtuse than in turning tools; thus in drills of limited dimensions the hook-form of the turning tool for iron is inapplicable, and in the larger examples the permanence of the tool is of more conse¬ quence than the increased friction. But on account of the ad¬ ditional friction excited by the nearly rectangular edges, it is commonly necessary to employ a smaller velocity in boring than in turning corresponding diameters, in order to avoid softening the tool by the heat generated; and in the ductile fibrous metals, as wrought-iron, steel, copper and others, lubrication with oil, water, etc., becomes more necessary than in turning. The drills and broaches form together a complete series. First, the cylinder bit, the pin drills, and others with blunt sides, produce cylindrical holes by means of cutters at right angles to the axis ; then the cutter becomes inclined at about 45 degrees, as in the common piercing drill and cone countersink; the angle becomes much less in the common taper broaches; and finally disappears in the parallel broaches, by which we again produce the cylin¬ drical hole, but with cutters parallel with the axis of the hole. Still considering the drills and broaches as one group, the drills have comparatively thin edges, always less than 90 degrees, yet they require to be urged forward by a screw or otherwise, the re¬ sistance being sustained in the line of their axes. The broaches have much more obtuse edges, never less than 90, and sometimes extending to 135 degrees; and yet the greater force required to cause the penetration of their obtuse edges into the material is supplied without any screw, because the pressure in all these varied tools is at right angles to the cutting edge. Thus supposing the sides of the broach extended until they meet in a point, as in Fig. 425, we shall find the length will very many times exceed the diameter, and by that number will the force em¬ ployed to thrust forward the tool be multiplied, the same as in the wedge, whether employed in splitting timber or otherwise; and the broach being confined in a hole, it cannot make its escape, but acts with lateral pressure, directed radially from each cutting edge; and the broach under proper management leaves the holes very smooth and of true figure. 416 THE PRACTICAL METAL-WORKER’S ASSISTANT. CEtAPTER XXIII. SCREW-CUTTING TOOLS. An elementary idea of the form of the screw, or helix, is ob¬ tained by considering it as a continuous circular wedge; and it is readily modeled by wrapping a wedge-formed piece of paper around a cylinder. The edge of the paper then represents the line of the screw, and which preserves one constant angle to the axis of the contained cylinder, namely, that of the wedge. The ordinary wedge, or the diagonal, may be produced by the composition of two uniform rectilinear motions, which, if equal, produce the angle of 45°, or if unequal, various angles more or less acute ; and in an analogous manner, the circular wedge or the screw may be produced of every angle or coarseness by the com¬ position of an uniform circular motion, with an uniform rectilinear motion. And as either the rectilinear or the circular motion may be given to the work or to the tool indifferently, there are four distinct modes of producing screws, and which are all variously modified in practice. The screw admits of great diversity. It may possess any diame¬ ter ; it may also have any angle—that is, the interval between the threads may be either coarse or tine, according to the angle of the wedge or the ratio of the two motions; and the wedge may be wound upon the cylinder to the right hand or to the left, so as to produce either right or left hand screws. The idea of double, triple, or quadruple screws, will be conveyed by considering two, three, or four black lines drawn on the uncovered edge of the wedge-formed paper, or likewise by two, three, or four strings or wires placed in contact, and coiled as a flat band around the cylinder, the angle remains unaltered, it is only a multiplication of the furrows or threads; and lastly, the screw may have any section, that is, the section of the worm or thread may be angular, square, round, or of any arbitrary form. Thus far as to the variety in screws. The importance of this mechanical element, the screw, in all works in the constructive arts, is almost immeasurable. For in¬ stance, great numbers of screws are employed merely for connect¬ ing together the different parts of which various objects are com¬ posed ; no other attachment is so compact, powerful, or generally available; these binding or attachment screws require, by compari¬ son, the least degree of excellence. Other screws are used as regu¬ lating screws, for the guidance of the slides and the moving parts of machinery, for the screws of presses and the like; these kinds should possess a much greater degree of excellence than the last. But the most exact screws that can be produced, are quite essen¬ tial to the good performance of the engines employed in the grad- SCREW-CUTTING TOOLS. 417 nation of right lines and circles, and of astronomical and mathe¬ matical instruments; in these delicate micrometrical screws, our wants ever appear to outstrip the most refined methods of ex¬ ecution. The attempt to collect and describe all the ingenious contriv¬ ances which have been devised for the construction of screws, would be in itself a'work of no ordinary labor or extent: I must, therefore, principally restrict myself to those varied processes now commonly used in the workshops, for producing with comparative facility, screws abundantly exact for the great majority of pur¬ poses. It has been found rather difficult to arrange these ex¬ tremely different processes in tolerable order, but that which seems to be the natural order has been adopted, thus:— There' appears to be no doubt, but that in the earliest produc¬ tion of the apparatus for cutting screws, the external screw was the first piece made; this plain circular metal screw was serrated and thus converted into the tap, or cutting tool, by which internal screws of corresponding size and form were next produced; and one of these hollow screws or dies became in its turn the means of regenerating, with increased truth and much greater facility, any number of copies of the original external screw. In these several stages there is a progressive advance towards perfection, as will be hereafter adverted to. These hand processes are mostly used for screws, which are at least as long, if not longer than their diameters. The rotatory and rectilinear guides, and the one or several series of cutting points, are then usually combined within the tool. This first group will be considered in the succeeding order:— On originating screws. On cutting internal screws, with screw taps. On cutting external screws, with screw dies. Subsequent improvements have led to the employment of the lathe in producing from the above, and in a variety of ways, still more accurate screws. These methods are sometimes used for screws which possess only a portion of a turn, at other times for screws twenty or thirty feet long and upwards. The rotatory guide is always given by the mandrel, the rectilinear guide is vari¬ ously obtained, and the detached screw tool or cutter, may have one single point, or one series of points which touch the circle at only one place at a time. This second group will be arranged thus:— On cutting screws, in the common lathe by hand. On cuttinor screws, in lathes with traversing mandrels. On cutting screws, in lathes with traversing tools. It may be further observed that the modes described under these heads are in general applied to very different purposes, and are only to a limited extent capable of substitution one for the other; it is to be also remarked that it has been considered convenient, in a great measure to abandon, or rather to modify, the usual dis- 27 418 THE PRACTICAL METAL-WORKER’S ASSISTANT. tinction between the tools respectively used for wood and for metal. The eighth and concluding section of this subject describes some refinements in the production of screws which are not com¬ monly practiced, and it is in some measure a sequel to the second section. On Originating Screws. —It appears more than probable, that in the earliest attempts at making a screw, a sloping piece of paper was cemented around the iron cylinder; this oblique line was cut through with a stout knife or a thin edged file, and was then gradually enlarged by hand until it gave a rude form of screw. Doubtless as soon as the application of the lathe was generally known, the work was mounted between centres, so that the prog¬ ress of filing up the groove could be more easily accomplished, or a pointed turning tool could be employed to assist. Such, in fact, is one of the modes recommended by Plumier, for cutting the screw upon a lathe mandrel for receiving the chucks, even in pref¬ erence to the use of the die-stocks, which, he urged, were liable to bend the mandrel in the act of cutting the screw. Nearly similar modes have been repeatedly used for the pro¬ duction of original screws; one account differing in several re¬ spects from the above, is described as having been very success¬ fully resorted to above fifty years back, at the Soho w'orks, Birm¬ ingham, by a workman of the name of Joe Baggs, before the in¬ troduction of the screw-cutting lathe. This is an English account of an English supposed invention. The screw was seven feet long, six inches diameter, and of a square triple thread; after the screw was accurately turned as a cylinder, the paper was cut parallel exactly to meet around the same, and w r as removed and marked in ink with parallel oblique lines, representing the margins of the threads; and having been replaced on the cylinder, the lines were pricked through with a centre punch. The paper was again removed, the dots were con¬ nected by fine lines cut in with a file, the spaces were then cut out with a chisel and hammer and smoothed with a file, to a sufficient extent to serve as a lead or guide. The partly formed screw was next temporarily suspended in the centre of a cast-iron tube or box strongly fixed against a horizontal beam, and melted lead mixed with tin, was poured into the box to convert it into a guide nut; it then only remained to complete the thread by means of cutters fixed against.the box or nut, but with the power of adjustment, in fact in a kind of slide-rest, the screw being handed round by levers. Another very simple way of originating screws, and which is sufficiently accurate for some purposes, is to coil a small wire around a larger straight wire as a nucleus ; this last is frequently the same wire the one end of which is to be cut into the screw. The covering wire, whose diameter is equal to the space required between the threads of the screw, is wound on dose and tight, and made fast at each end. The coiled screw, being enclosed between SCREW-CUTTING TOOLS. 419 two pieces of hard wood, indents a hollow or counterpart thread, sufficient to guide the helical traverse, and a fixed cutter completes this simple apparatus. Common screws, for some household purposes, have been made of tinned iron wire; two covering wires are rolled on together, the one being removed leaves a space such as the ordinary hollow of the thread, and when these screws are dipped in a little melted tin, the two wires become soldered together. Other modes have been resorted to for making original screws, by indenting a smooth cylinder with a sharp-edged cutter placed across the same at the required angle, and trusting to the surface or rolling contact to produce the rotation and traverse of the cylinder, with the development of the screw. In the most simple application of this method a deep groove is made along a piece of board in which a straight wire is buried a little beneath the sur¬ face. A second groove is made nearly at right angles across the first, exactly to fit the cutter, which is just like a table knife, and is placed at the angle required in the screw. The cutter when slid over the wire indents it, carries it round, and traverses it end¬ ways in the path of a screw. A helical line is thus obtained, which, by cautious management, may be perfected into a screw sufficiently good for many purposes. Mr. Walsh, of Dublin, employed a cutter upon cylinders of wood, tin, brass, iron, and other materials, mounted to revolve between centres in a triangular bar lathe ; the knife was hollowed to fit the cylinder, and fixed at the required angle on a block adapted to slide upon the bar; the oblique incision carried the knife along the revolving cylinder. Some hundreds of screws were thus made, and their agreement with one another was in many instances quite remarkable. On the whole he gave the preference to this mode of originating screws. The apparatus for originating screws for astronomical and other purposes is represented in plan in Fig. 427, in side elevation in Fig. 428, and 429 is the front elevation of the cutter frame alone. This method is also due to Mr. Walsh. The piece intended for the screw, namely, a a, Fig. 427, is turned cylindrical, and with two equal and cylindrical necks; it is supported in a metal frame with two semi-circular bearings, b b, which are fixed on a slide moved by an adjusting screw c. The instrument generates original screws perfectly true, of any number of threads, and right or left handed. In this case, the stock and cutter are made as in Figs. 427, 428, and 429 ; the back of the stock is made into the segment of a circle, s ; and the top of the cutter is continued into an index, t. The cutter is a single thread, and moves on its edge, v, as a centre. This must fit true, and the stock fit close to the cutter, to keep it perfectly steady: u, u, two screws, to adjust and fasten the cutter to any required angle. The cutter should be rather elliptical, for it is best to fit well to the cylinder at the greatest angle it will be ever used. 420 THE PRACTICAL METAL-WORKERS ASSISTANT. When one turn has been given to the cylinder, Fig. 427, a tooth, w is put into the cut, and screwed fast. This tooth secures the 427 lead, and causes every following thread to be a repetition of the first; and though it might do without, yet this is a satisfactory security. In cutting ordinary screws, the dies shown separately in Figs. 430 to 433, the consideration of which is for the present deferred, takes the place of the oblique cutter in the former figures. The screw is also originated by traversing the tool in a right line alongside a plain revolving cylinder. Sometimes the tool has many points, and is guided by the hand alone; at other times the tool has but one single point, and is guided mechanically so as to proceed, say one inch or one foot in a right line, whilst the cylin¬ der makes a definite number of revolutions. The tool is then traversed either by a wedge placed transversely to the axis, by a chain or metallic band placed longitudinally, or by another screw connected in various ways with the screw to be produced, by wheel-work and other contrivances. On Cutting Internal Screws, with Screw Taps. —The screw is converted into the tap by the removal of parts of its circumfer¬ ence, in order to give to the exposed edges a cutting action; whilst the circular parts which remain, serve for the guidance of the in¬ strument within the helical groove, or hollow thread, it is required to form. SCREW-CUTTING TOOLS. 421 In the most simple and primitive method, four planes were filed upon the screw, as in Fig. 434, but this exposes very obtuse edges which can hardly be said to cut, as they form the thread partly by indenting, and partly by raising or burring up the metal; and as such they scarcely produce any effect in cast-iron or other crystal¬ line materials. Conceiving, as in Fig. 434, only a very small por¬ tion of the circle to remain, the working edges of squared taps, form angles of (90 + 45 or) 135 degrees with the circumference, and the angle is the greater, the more of the circle that remains. It is better to file only three planes, as in Fig. 435, but the angle is then as great as 120 degrees even under the most favorable cir¬ cumstances. < In taps of the smallest size it is imperative to submit to these conditions, and to employ the above sections. Sometimes small intermediate facets or planes are tipped off" a little obliquely with the file, to relieve the surface friction; this gives the instrument partly the character of a six or eight sided broach, and improves the cutting action. Figs. 434 435 436 437 438 439. There appears to be no doubt that, for general purposes, the most favorable angle for the edges of the screw taps and dies is the radial line, or an angle of 90 degrees. This condition mani¬ festly exists in the half-round tap, Fig. 436. I propose that this should be made half-round, as it will be found that a tap formed in this way will cut a full clear thread (even if it may be of a sharp pitch), without making up any part of it by the burr, as is almost universally the case when blunt-edged or grooved taps are used. It has sometimes been objected to me by persons who had not seen half-round taps in use, that from their containing less substance than the common forms do, they must be very liable to be broken by the strain required to turn them in the work. It is proved, however, by experience, that the strain in their case is so much smaller than usual, that there is even less chance of breaking them than the stouter ones. Workmen are aware that a. half-round opening bit makes a better hole and cuts faster than a five sided one, and yet that it requires less force to use it. Fig. 437, in which two-thirds of the circle are allowed to remain, has been also employed for taps; this, although somewhat less penetrative than the last, is also less liable to displacement with the tap wrench. It is much more usual to employ three radial cutting edges instead of one only; and as in the best forms of taps, they are only required to cut in the one direction, or when they 422 THE PRACTICAL METAL-WORKER’S ASSISTANT. are screwed into the nut, the other edges are then chamfered to make room for the shavings; thereby giving the tap a section somewhat like that of a ratchet wheel, with either three, four, or five teeth, as in Figs. 438 and 446. It is more common, however, either to file up the side of the tap, or to cut by machinery, three concave or elliptical flutes, as in 439 ; this form sufficiently approximates to the desideratum of the radial cutting edges, it allows plenty of room for the shavings, and is easily wiped out. What is of equal or greater importance, it presents a symmetrical figure, little liable to accident in the hardening, either of distortion from unequal section, as in Figs. 436 and 437, or of cracking from internal angles as in 437 and 438. Still, considering alone the transverse section of the tap, it will be conceived that before any of the substance can be removed from the hole that is being tapped, the circular part of the instrument must become embedded into the metal a quantity equal to the thickness of the shaving; and in this respect Figs. 434 and 435, in which the circular parts are each only the tenth or twelfth of the circumference, appear to have the advantage over the modern taps 438 and 439, in which each arc is twice as long. Such, however, is not the case, as the first two act more in the manner of the broach, if we conceive that instrument to have serrated edges; but Figs. 438 and 439 act nearly as turning tools, as in general the outer or the circular surface is slightly relieved with a file, so as to leave the cutting edges a, somewhat in advance of the general periphery; which is equivalent to chamfering the lower plane of the turning tool some three degrees to produce that relief which has been appropriately named the angle of separation. But in the tap Fig. 440, invented by F. O’Neal, this is still more Figs. 440 441 442 443. effectually accomplished. The instrument, instead of being turned of the ordinary circular section in the lathe (or as the outer dotted line), is turned with three slight undulations, by means of an alter¬ nating radial motion given to the tool. From this it results that, when the summits of these hills are converted into the cutting edges, that not only are the extreme edges or points of the teeth SCREW-CUTTING TOOLS. 423 nade prominent, but the entire serrated surface becomes inclined at about the three degrees to the external circle, or the line of work, so as exactly to assimilate to the turning tool; and therefore there is little doubt but that, under equal circumstances, O’Neal’s tap would work with less friction than any other. The principle of chamfering, or relieving the taps, must not, however, be carried to excess, or it will lead to mischief. For ex¬ ample, the tap, if sloped behind the teeth as is Fig. 441, would be much exposed to fracture; and the instrument being entirely under its own guidance, the three series of keen points would be apt to stick irregularly into the metal, and would not produce the smooth, circular, or helical hole, obtained when the tool, Fig. 442, is used. The relief should be slight, and the surfaces of the teeth then assimilate to the condition of the graver for copper plates, and thereby direct the tap in a very superior manner. The teeth sloped in front, as in Fig. 443, would certainly cut more keenly than those of 442, but they would be much more ex¬ posed to accident, as the least backward motion or violence would be liable to snip off the keen points of the teeth ; and therefore, on the score of general economy and usefulness, the radial and slightly relieved teeth of Fig. 442, or rather of 439, are proper for work¬ ing taps. It appears further to be quite impolitic, entirely to expunge the surface-bearing, or squeeze, from the taps and dies, when these are applied to the ductile metals; as not only does it, when slight, greatly assist in the more perfect guidance of the instrument, but it also serves somewhat to condense or compress the metal. Unless the taps cut very freely, it is the general aim to avoid the necessity for tapping cast-iron, which is a granular and crystal¬ line substance, apt to crumble away in the tapping, or in the after use. The general remedy is the employment of bolts and nuts made of wrought-iron, or fixing screwed wrought-iron pins in the work, by means of transverse keys and other contrivances, and sometimes by the insertion of plugs of gun-metal, to be afterwards tapped with the screw-threads. In general also, the small screws for cast-iron are coarse and shallow in the thread compared with those for wrought-iron, steel, and brass. The transverse sections hitherto referred to, are always used for those taps employed in screwing the inner surfaces of the nuts, and holes required in general mechanism. The longitudinal section of the working tap is taper and somewhat like a broach, the one end being small enough in external diameter to enter the blank hole to be screwed, and the other end being as large as the screw for which the nut is intended. In many cases a series of two, three, or four taps must be used instead of only one single conical tap, and the modifications in their construction are explained by the following diagrams; namely, Fig. 444, the tap formerly used for nuts and thoroughfare holes, and Fig. 445, the modern tap for the same purposes: the dotted lines in each represent the bottoms of the threads. 424 THE PRACTICAL METAL-WORKER’S ASSISTANT. In the former kind, the thread was frequently finished of a taper figure, with the screw tool in the lathe; after which either the four or three plane surfaces were filed upon it, as shown by the section at s ; the neck from / to g was as small as the bottom of the thread, and the tang from g to h was either square or rectangular for the tap wrench. The tang, if square, was also taper, the tap wrench then wedged fast upon the tap; the sides of the tang, if parallel, were rectangular, and measured as about one to two, and there were shoulders on two sides to sustain the wrench. Fig. 444. In the modern thoroughfare taps for nuts, drawn to the same scale in Fig. 445, the thread is left cylindrical, from the screw tool or the dies; then from a to b, or about one diameter in length, is turned down cylindrical until the thread is nearly obliterated ; from dtof also nearly one diameter in length at the other end, is left of the full size of the bolt, and the intermediate part, b to d, equal to three or four diameters, is turned to a cone, after which the tap is fluted as seen at s. The neck f g, as before, is as small as the bottom of the thread, and the square g h, measures diagon¬ ally the same as the turned neck. In using the modern instrument, Fig. 445, the hole to be tapped is bored out exactly to fit the cylindrical plug a b, which therefore guides the tap very perfectly in the commencement; the tool is simply passed once through the nut without any retrograde motion whatever, and the cylindrical part d f takes up the guidance when the larger end of the cone enters the hole; at the completion, the tap drops through, the head being smaller than the bottom of the thread. The old four square taps could not be thus used, for as they rather squeezed than cut, they had much more friction; it was necessary to move them backwards and forwards, and to make the square for the wrench larger, to avoid the risk of twisting oft’ the head of the tap. In taps of modern construction of less than half an inch diameter, it is also needful to make the squares larger than the proportion employed in Fig. 445. In tapping shallow holes, as only a small portion of the end of SCREW-CUTTING TOOLS. 425 the tap can be used, the screwed part seldom exceeds two diame¬ ters in length, and as they will not take hold when made too coni¬ cal, a succession of three or four taps is generally required. The screwed part of the first may be considered to extend from a to b of Fig. 444, of the second, from c to d, of the third from e to /; so that the prior tap may, in each case, prepare for the reception of the following one. The taps are generally made in sets of three; the first, which is also called the entering or taper tap, is in most cases regularly taper throughout its length ; the second, or the middle tap, is sometimes taper, but more generally cylindrical, with just two or three threads at the end tapered off; the third tap, which is also called the plug or finishing tap, is always cylin¬ drical, except at the two or three first threads, which are slightly reduced. Taps are used in various ways, according to the degree of strength required to move them. The smallest taps should have considerable length, and should be fixed exactly in the axis of straight handles; the length serves as an index by which the true position of the instrument can be verified in the course of work; with the same view as to observation, and as an expeditious mode, taps of a somewhat larger size are driven round by a hand brace, whilst the work is fixed in the vice. Still larger taps require tap wrenches, or levers with central holes to fit the square ends of the taps; for screw taps from one to two inches diameter, the wrenches have assumed the lengths of from four to eight feet, although the recent improvements in the taps have reduced the lengths of the wrenches to one-half. Notwithstanding that the hole to be tapped may have been drilled straight, the tap may by improper direction proceed ob¬ liquely ; the progress of the operation should be therefore watched, and unless the eye serve readily for detecting any falseness of position, a square should be laid upon the work, and its edge com¬ pared with the axis of the tap in two positions. In tapping deeply seated holes, the taps are temporarily length¬ ened by sockets, frequently the same as those used in drilling, which are represented in Fig. 401, page 403 ; the tap wrench can then surmount those parts of the work which would otherwise prevent its application. Sometimes for tapping two distant holes exactly in one line, the ordinary taper tap, Fig. 445, is made with the small cylindrical part a b exceedingly long, so as to reach from the one hole to the other and serve as a guide or director. This is only an extension of the short plug a b, Fig. 445, which it is desirable to leave on most taps used for thoroughfare holes. Some works are tapped whilst they are chucked on the lathe mandrel; in this case the shank of the tap, if in false position, will swing round in a circle whilst the mandrel revolves, instead of continuing quietly in the axis of the lathe. Sometimes the centre point of the popit-head is placed in the centre hole in the head of 426 THE PRACTICAL METAL-WORKER’S ASSISTANT. the tap; in those which are fixed in handles it is better the handle of the tap should be drilled up to receive the cylinder of the popit- head, as in the lathe taps for making chucks; this retains the guid¬ ance more easily. Taps of large size, as well as the generality of cutting instru¬ ments, have been constructed with detached cutters. For those exceeding about 1J inch diameter, two steel plugs a a, may be in¬ serted within taper holes in the body of the tap, as represented in Fig. 446, and in the two sections b and c ; the whole is then screwed and hardened. Fig. 446. The advance of the cutters slightly beyond the general line of the thread, is caused by placing a piece of paper within the mor¬ tises a b, and to relieve the surface friction, each alternate tooth in the middle part of the length of the tap is filed away. Sometimes the cutters are parallel and inserted only partway through, and are then projected by set screws placed also on the diameter, as in the section c. The cutter bar, Fig. 415, p. 410, may also be viewed as a tap with detached cutters. The cylindrical bar is supported in tem¬ porary fixed bearings, one of which embraces the thread (some¬ times by having melted load poured around the same), the bar moves therefore in the path of a screw. In cutting the external thread, the cutter represented is shifted inwards with the progress of the work ; or a straight cutter shifted outwards, serves for mak¬ ing an internal screw; pointed instead of serrated cutters may be also used; they are frequently adjusted by a set screw instead of the hammer, and are worked by a wrench. This screw cutter bar, independently of its use for large awk¬ ward works, is also employed for cutting, in their respective situa¬ tions, screws required to be exactly in a line with holes or fixed bearings, as the nuts of slides, presses, and similar works. Some taps or cutters are made cylindrical, and are used for cut¬ ting narrow pieces and edges, such as screw-cutting dies, screw tools, and worm wheels; therefore it is necessary to leave much more of the circle standing, and to make the notches narrower than the width of the smallest pieces to be cut. But the grooves should still possess radial sides, and when these are connected by a curved line, as in Fig. 447, there is less risk of accident in the hardening. The number of the notches increases with the diame¬ ter, but the annexed figure would be better proportioned if it had SCREW-CUTTING TOOLS. 427 one or two less notches, as inadvertently the teeth have been drawn too weak. When the tool, Figs. 447 and 448, is used for cutting the dies of die stocks it is called an original lap, of which further particulars Figs. 447 448. will be given in the succeeding section ; the tool is then fixed in the vice, and the die-stock is handed round, as in cutting an ordinary screw. When Fig. 448 is used for cutting up screw tools, or the chasing-tools for the use of the turning lathe, the cutter is then called a hob, or a screw-tool cutter, and its diameter is usually greater; it is now mounted to revolve in the lathe, and the screw tool to be cut is laid on the rest as in the process of turning, and is pressed forcibly against the cutter. Another method is proposed: the inside screw tool is laid in a lateral groove in a cylindrical piece of iron, and the tool and cylinder are cut up with the die-stocks as a common screw; by which mode the inside screw tool obviously becomes the exact counterpart of the hollow thread of that particular diameter. Fig. 448 is also used as a worm-wheel cutter, that is, for cutting or for finishing the hollow screw-form teeth, of those wheels which are moved by a tangent screw; as in the dividing-engine for cir¬ cular lines, and many other cases in ordinary mechanism. The worm-wheel cutter is frequently set to revolve in the lathe, and the wheel is mounted on a temporary axis so as to admit of its being carried round horizontally by the cutter; sometimes the wheel and cutter are connected by gear. The contact of the ordinary tangent screw with the worm-wheel, resembles that of the tangent to the circle, whence the name ; but Hindley, of York, made the screw of his dividing engine to touch 15 threads of the wheel perfectly, by giving the screw a curved section derived from the edge of the wheel, and smallest in the middle. In cutting the metal screw, or the bolt, the tools are required to be the converse of the tap, as they must have internal instead of external threads, but the radial notches are essential alike in each. For small works, the internal threads are made of fixed sizes and in thin plates of steel; such are called screw plates; for larger works, the internal threads are cut upon the edges of two or three detached pieces of steel, called dies; these are fitted into grooves within die¬ stocks, and various other contrivances which admit of the approach 428 THE PRACTICAL METAL-WORKERS ASSISTANT. of the screwed dies, so that they may be applied to the decreasing diameter of the screw, from its commencement to the completion. The thickness of the screw plate is in general from about two- thirds to the full diameter of the screw, and mostly several holes are made in the same plate; from two to six holes are intended for one thread, and are accordingly distinguished into separate groups by little marks, as in Fig. 449. The serrating of the edges is some¬ times done by making two or three small holes and connecting them by the lateral cuts of a thin saw, as in Fig. 450. The notches alone are sometimes made, and when the holes are arranged as in Fig. 451, should the screw be broken short off by accident, it may be cut in two with a thin saw, and thus removed from the plate. In making small screws, the wire is fixed in the hand-vice, tap¬ ered off with a file, and generally filed to an obtuse point; then, after being moistened with oil, it is screwed into the one or several holes in the screw plate, which is held in the left hand. At other times, the work fixed in the lathe is turned or filed into form, and the plate is held in the right hand; but the force then applied is less easily appreciated. The harp-makers and some others, attach a screw plate with a single hole to the sliding cylinder of the popit- head. Figs. 449 450 451. The screw plate is sometimes used for common screws as large as from half to three-quarters of an inch diameter; such screws are fixed in the tail vice, and the screw plate is made from about 15 to 30 inches long, and with two handles; the holes are then made of different diameters, by means of a taper tap, so as to form the thread by two, three, or more successive cuts, and the screw should be entered from the large side of the taper hole. It is, however, very advisable to use the diestocks, in preference to the screw plates, for all screws exceeding about one-sixteenth of an inch diameter, although the unvarying diameter of the screw plate has the advan¬ tage of regulating the equal size of a number of screws, and as such, is occasionally used to follow the diestocks, by way of a gage for size. The diestock, in common with other general tools, has received a great many modifications that it would be useless to trace in greater detail, than so far as respects the varieties in common use, or those which introduce any peculiarity of action in the cutting edges. A notion of the early contrivances for cutting metal screws SCREW-CUTTING TOOLS. 429 will be gathered from the figures 452 to 455, which are copied half-size from “Leupold’s Theatrum Machinarum Generate, 1724.” For instance, Fig. 452 is the screw plate in two, and jointed to¬ gether like a common rule; the inner edges are cut with threads, the larger of which is judiciously placed near the joint, that it may be more forcibly compressed; there is a guide a, a, to prevent the lateral displacement of the edges, which would be fatal to the action. Similar instruments are still used, but more generally for screws made in the turning lathe. Figs. 452 453 454 455. In one of these tools, the frame or stock is made exactly like a pair of flat pliers, but with loose dies cut for either one or two sizes of threads. Plier diestocks are also made in the form of common nut-crackers, or in fact, much like Fig. 452, if we consider it to- have handles proceeding from a a, to extend the tool to about two or three times its length; the 'guide a a is retained, and removable dies are added, instead of the threads being cut in the sides of the instrument. In general, however, the two dies are closed together in a straight line, instead of the arc of a circle: one primitive method, Fig. 455, extracted from the work referred to, has been thus remodeled; the dies are inserted in rectangular tapei holes, in the ends of two long levers, which latter are connected by two cylindrical pins, care¬ fully fitted into holes made through the levers, and the ends of the pins are screwed aud provided with nuts, which serve more effect¬ ually to compress the dies than the square rings represented in Fig. 455. The diestock in its most general form has a central rectangular aperture, within which the dies are fitted, so as to admit of compres¬ sion by one central screw; the kinds most in use being distin¬ guished as the double chamfered diestocks, Figs. 456 and 457 ; and the single chamfered diestock, Figs. 459 and 460, the handles of which are partly shown by dotted lines. In the former, the aperture is about as long as three of the dies; about one-third of the length of the chamfer is filed away at the end, for the removal of the dies 430 THE PRACTICAL METAL-WORKER’S ASSISTANT. laterally, and one at a time. In the single chamfered diestock 460, which is preferable for large threads, the aperture but little exceeds the length of two dies, and these are removed by first taking off the side plate b a, which is either attached by its chamfered edges as a slide, or else by four screws; these, when loosened, allow the plate to be slid endways, and it will be then disengaged, as the screws will leave the grooves at a, and the screw heads will pass through the holes at b. Figs. 456 457 458 461 462 Sometimes dies of the section of Fig. 458 are applied after the manner of 457, and occasionally the rectangular aperture of Fig. 460 is made parallel on its inner edges, and without the side plate b a; the dies are then retained by steel plates either riveted or screwed to the diestock, as represented in Fig. 461, or else by two steel pins buried half-way in the sides of the stock, and the re¬ maining half in the die, as shown in Fig. 462. These variations are of little moment, as are also those concerning the general form of the stock : for instance, whether or not the handles proceed in the directions shown (the one handle being occasionally a con¬ tinuation of the pressure screw), or whether the handles are placed as in the dotted position t. In small diestocks, a short stud or handle is occasionally attached at right angles to the extremity, that the diestock may be moved like a winch handle; and some¬ times graduations are made upon the pressure screw, to denote the extent to which the dies are closed. These and other differences are matters comparatively unimportant, as the accurate fitting of the dies, and their exact forms, should receive the principal atten¬ tion. In general only two dies are used, the inner surface of each of SCREW-CUTTING TOOLS. 431 which includes from the third to nearly the half of- a circle, and a notch is made at the central part of each die, so that the pair of dies present four arcs, and eight series of cutting points or edges; four of which operate when the dies are moved in the one direc¬ tion, and the other four when the motion is reversed; that is when the curves of the die and screw are alike. The formation of these parts has given rise to much investigation and experiment, as the two principal points aimed at require di¬ rectly opposite circumstances. For instance, the narrower the edges of the dies, or the less of the circle they contain, the more easily they penetrate, the more quickly they cut, and the less they com¬ press the screw by surface friction or squeezing, which last tends to elongate the screw beyond its assigned length. But, on the other hand, the broader the edges of the dies, or the more of the circle they contain, the more exactly do they retain the true helical form and the general truth of the screw. The action of screw-cutting dies is rendered still more difficult, because in general one pair of dies, the curvatures and angles of which admit of no change , are employed in the production of a screw, the dimensions of which during its gradual transit from the smooth cylinder to the finished screw continually change. For instance, the thread of a screw necessarily passes two mag¬ nitudes, namely, the top and bottom of the groove, and also two angles at these respective diameters, as represented by the dotted lines in the diagrams, Figs. 463, 465, and 467 (which are drawn with straight instead of curved lines). The angles are nearly in the inverse proportion of the diameters; or if the bottom were half the diameter of the top of the thread, the angle at the bottom would be nearly twice that at the top. The figures show the original taps, master taps, or cutters, from which the dies, Figs. 464, 466, and 468, are respectively made; and in each of the three diagrams the dies a are supposed to be in the act of commencing, and the dies b in finishing, a screw of the same diameter throughout as that in Fig. 463. Of course the circumstances become the more perplexing the greater the depth of the thread, whereas in shallow threads the interference may be safely overlooked. As the dies cannot have both diameters of the screw, it becomes needful to adopt that cur¬ vature which is least open to objection. If, as in Fig. 464, the curved edges of the dies a and b have the same radii as the finished screw, in the commencement, or at a, the die will only touch at the corners, and the curved edges being almost or quite out of contact, there will be scarcely any guidance from which to get the lead oi first direction of the helix, and the dies will be likely to cut false screws, or else parallel grooves or rings. In addition to this, the curved edges present, at the commencement, a greater angle than that proper for the top of the screw ; but at the completion of the screw, or at b, the die and screw will be exact counterparts, and will be therefore perfectly suitable to each other. 432 THE PRACTICAL METAL-WORKER’S ASSISTANT. If, as in Fig. 468, the inner curvature of the dies a and b be the same as in the blank cylinder, a will exactly agree both in diame- Figs. 463 465 467 Small Master Tap. Medium Master Tap. Same diameter as Screw. One depth larger than Screw. Large Master Tap. Two depths larger than Screw. ter and angle at the commencement of the screw, but at the con¬ clusion, or as at b, each will be too great, and the die and screw will be far from counterparts, and therefore ill adapted to each other. The most proper way of solving the difficulty in dies made in two parts, is by having two pairs of dies, such as 468 and 464 and which is occasionally done in very deep threads, see Figs. 432 and 433. But it is more usual to pursue a medium course, and to make the original tap or cutter, Fig. 465, used in cutting the dies, not of the same diameter as the bolt, as in Figs. 463 and 464, not to exceed the diameter of the bolt by twice the depth of the thread, as in Figs. 467 and 468, but with only one depth beyond the exact size, or half-way between the extremes as in Figs. 465 and 466, in which latter it is seen the contact, although not quite perfect either at a or h, is sufficiently near at each for general practice. The obvious effect of different diameters between the die and screw must be a falsity of contact between the surfaces and angles of the dies ; thus in 464 the whole of the cutting falls upon e, the external angles, until the completion of the screw in b, when the action is rather compressed than cutting. In Fig. 468 the first act is that of compressing, and all the work is soon thrown on i, the internal angles of the die, which become gradually more pene¬ trative, but eventually too much so, being in all respects the reverse of the former. In the medium and most common example, Fig. 466, the cut falls at first upon the external angles e, it gradually dies away, and it is during the brief transition of the cut from the external to the internal angles i, that is, when the screw is exactly half-formed, that the compression principally occurs. The compression or squeezing is apt to enlarge the diameter of the screw (literally by swaging up the metal), and also to elongate SCREW-CUTTING TOOLS. 433 it beyond its assigned length, and that unequally at different parts. Sometimes the compression of the dies makes the screw so much coarser than its intended pitch that the screw refuses to pass through a deep hole cut with the appropriate tap. Not only may the total increase in length be occasionally detected by a common rule, but the differences between twenty or thirty threads, measured at va¬ rious parts with fine-pointed compasses, are often plainly visible. Other and vastly superior modes for the formation of long screws, or those requiring any very exact number of threads in each inch or foot of their length, will be shortly explained. Yet notwith¬ standing the interferences which deprive the diestocks of the refined perfection of these other methods, they are a most invalu¬ able and proper instrument for their intended use; and the dis¬ agreement of curvature and angle is more or less remedied in prac¬ tice, by reducing the circular part of the dies in various ways; and also in some instances, by the partial separation of the guiding from the cutting action. The most usual form of dies is shown in Fig. 469, but if every measure be taken at the mean, as in Fig. 470, the tool possesses a fair, average, serviceable quality; that is, the dies should be cut over an original tap of medium dimensions, namely one depth larger than the screw, such as Fig. 465; the curved surface should be halved, making the spaces and curves as nearly equal as may be; and the edges should be radial. Fig. 471, nearly transcribed from Leupold’s figure, 453, has been also used, but it appears as if too much of the curve were then removed. Sometimes the one die is only used for guiding, and the other only for cutting: thus a, Fig. 472, is cut over two different diameters of master taps, which gives it an elliptical form. A large master tap, Fig. 467, is first used for cutting the pair of dies; this leaves the large parts of the curve in a ; the dies are subsequently cut over a small master tap, 463. Figs. 469 470 471 472 473. In beginning the screw, the die a, serves as a bed with guiding edges; these indent without cutting, and also agree at the first start, with the full diameter of the bolt; with the gradual reduc¬ tion of the bolt, it sinks down to the bottom of a, which continually presents an angular ridge, nearly agreeing in diameter, and there¬ fore in angle with the nascent screw. The inconveniences of the dies, Fig. 472, are, that they require a large and a small, master tap 28 434 THE PRACTICAL METAL-WORKER’S ASSISTANT. for the formation of every different sized pair of dies, and which latter are rather troublesome to repair. The dies also present more friction than most others, apparently from the screw becoming wedged within the angular sides of the die a. In Fig. 473, the dies are first cut over a small master tap, Fig. 464, the threads are then partially filed or turned out of b, to fit the blank cylinder; which therefore rests at the commencement upon blunt triangular, curved surfaces, instead of upon keen edges; and as the screw is cut up, its thread gradually descends into the por¬ tions of the thread in b, which are not obliterated. About one- third of the thread is turned out from each side of the cutting die a, leaving only two or three threads in the centre, as shown in the last view; and the surface of this die is loft flat, that it may be ground up afresh when blunted, and which is also done with other dies having plane surfaces. Mr. William Ryan and Mr. Patrick Mullen have each proposed to assist the action of dies for large screws, by means of cutters; their plans will be sufficiently explained by the diagrams, Figs. 474 and 475. This mode to large screws of square threads was applied for gun carriages; the dies were cut very shallow, say one- third of the full depth, and they were serrated on their inner faces to act like saws or files. The dies were used to cut up the com¬ mencement of the thread, but when it filled the shallow dies, their future office was not to cut, but only to guide the ascent and descent of the stocks, by the smooth surfaces of the dies rubbing upon the top of the square thread. The remaining portion of the screw was afterwards ploughed out by a cutter like a turning tool, the cutter being inserted in a hole in the one die, and advanced by a set screw, somewhat after the manner represented in the figures 474 and 475. Figs. 474 476 478 Mullen employed a similar method for angular thread screws, and the cutter was placed within a small frame fixed to the one die. The screw bolt was commenced with the pair of dies which were closed by the set screw a, 474, the cutter being then out SCREW-CUTTING TOOLS. 435 of action. When the cutter was set to work by its adjusting screw b, it was advanced a little beyond the face of the die, and not afterwards moved; but the advance of a closed the dies upon the decreasing diameter of the screw, the cutter always continuing prominent and doing the principal share of the work. Figure 476 is the plan, and 477 the side elevation, of an old although imperfect expedient,, for producing a left-handed screw from a right-handed tap. It will be remembered the right and left-hand screws only differ in the direction of the angle, the thread of the one coils to the right, of the other to the left hand; and on comparing a corresponding tap and die, the inclinations of the ex¬ ternal curve of the one, and the internal curve of the other neces¬ sarily differ in like manner as to direction. The mode employed, therefore, is to carry a right-hand tap around the screw to be cut; the temporary screw-cutter possesses the same interval or thread as before, but the cutting angles of the tap, having the reverse direc¬ tion of those of the die, the screw becomes left-handed. The one die in 476 and 477 is merely a blank piece of brass or iron without any grooves, the other is a brass die in which the tap is fixe^; as may be expected, the thread produced is not very per¬ fect, but in the absence of better means, this mode is available as the germ for the production of a set of left-hand taps and dies. Figs. 478 and 479 represent a different mode of originating a left- handed screw, proposed by Mr. Walsh; the tool is to be a small piece of a right-handed screw, which is hardened and mounted in a frame like an ordinary milling or nurling tool, and intended to act by pressure alone; the diameter of the tool and cylinder should be alike. The screw stock represented in Fig. 480: three narrow dies Figs. 480 481 482. were fitted in three equidistant radial grooves in the stock, the ends of the dies came in contact with an exterior ring, having on its inner edge three spiral curves (equivalent to three inclined planes), and on its outer surface a series of teeth into which worked 436 THE PRACTICAL METAL-WORKER’S ASSISTANT. a tangent screw, so that on turning the ring by the screw, the three dies were simultaneously and equally advanced towards the centre. These screw stocks were found to cut very rapidly, as every cir¬ cumstance was favorable to that action. For instance, on the principle of the triangular bearing, all the three dies were con¬ stantly at work ; the original tap being slightly taper, every thread in the length of the die was performing its part of the work, the same as in a taper tap, every thread of which removes its shaving or share of the material; and the dies were narrow, with radial edges, which admitted of being easily sharpened. The diestock has been abandoned in favor of the screw stock, which is represented in Fig. 481. The one die embraces about one-third of the circle, the two others much less; the latter are fitted into grooves which are not radial, but lead into a point sit¬ uated near the circumference of the screw-bolt; the edges of the dies are slightly hooked or ground respectively within the radius, and they are simultaneously advanced by the double wedge and nut; the dies are cut over a large original, such as Fig. 467, that is, two depths larger than the screw. The large die serves to line out or commence the screw, and the two others act alternately; the one whilst the stock descends down the bolt, the other during its ascent. We will notice but one more screw stock. It is seen that the one die embraces about one-third the screw, the other is very nar¬ row ; the peculiarity of this construction is that a circular recess is first turned out of the screw stock, and a parallel groove is made into the same, the one handle of the stock (which is shaded), nearly fills this recess, and receives the small die. If the handle fitted mathematically true, it is clear it would be immovable, but the straight part of the handle is narrower than the width of the groove; when the stock is turned round, say in the direction from 2 to 1, the first process is to rotate the handle in the circle, and to bring it in hard contact with the side 1, this slightly rotates the die also, and the one corner becomes somewhat more prominent than the other. When the motion of the stock is reversed, the handle leaves the side 1, of the groove, and strikes against the other side 2, and then the opposite angle of the die becomes the more prominent; and that without any thought or adjustment on the part of the workman, as the play of the handle in the groove 1, 2, is exactly proportioned to cause the required angular change in the die. The cutting edges of the die act exactly like turning tools, and therefore they may very safely be beveled or hooked as such; as when they are not cutting, they are removed a little way out of contact, and therefore out of danger of being snipped off, or of being blunted by hard friction. The opposite die affords daring the time an efficient guidance for the screw, and the broad die is ad¬ vanced in the usual manner, by the pressure screw made in con- SCREW-CUTTING TOOLS. 487 tinuation of the second handle of the diestock; the dies are kept in their places by a side plate, which is fitted in a chamfered groove in the ordinary manner. There is less variety of method in cutting external screws witl the diestocks, than internal screws with taps, but it is desirable ir both cases, to remove the rough surface the work acquires in th foundry or forge, in order to economize the tools; and the bes works are either bored or turned cylindrically to the true diame ters corresponding with the screwing tools. The bolt to be screwed is mostly fixed in the tail vice vertically, but sometimes horizontally, the dies are made to apply fairly, and a little oil is applied prior to starting. As a more expeditious method suitable to small screws, the work is caused to revolve in the lathe, whilst the diestock is held in the hand ; and larger screws are sometimes marked or lined out whilst fixed in the vice, the principal part of the material is then removed with a chasing tool or hand-screw tool, and the screw is concluded in the die¬ stocks. In cutting up large screw bolts, two individuals are re¬ quired to work the screw stocks, and they walk round the standing vice or screwing clamp, which is fixed to a pedestal in the middle of the workshop. For screwing large numbers of bolts, the engineer employs the bolt-acrewing machine, which is a combination of the ordinary taps and dies, with a mandrel, driven by steam-power. In the machine the mandrel revolves, traverses, and carries the bolt, whilst the dies are fixed opposite to the mandrel; or else the mandrel carries the tap, and the nut to be screwed is grasped opposite to it. In another machine, the mandrel does not traverse, it carries the bolt, and the dies are mounted on a slide; or else the mandrel carries the nut, and the tap is fixed on the slide. The tap or die gives the traverse in every case, and the engine and strap supply the muscle; of course the means for changing the direction of motion and closing the dies, as in the hand process, are also essential. The screwing table is a useful modification of the bolt machine, intended to be used for small bolts, and to be worked by hand. The mandrel is replaced by a long spindle running loosely in two Figs. 483 484. 438 f THE PRACTICAL METAL-WORKER’S ASSISTANT. bearings; the one end of the spindle terminates in a small wheel with a winch-handle, the other in a pair of jars closed by a screw. The jaws embrace the head of the bolt, which is presented opposite to dies tnat are fixed in a vertical frame or stock, and closed by a loaded lever to one fixed distance. In tapping the nut, it is fixed in the place before occupied by the dies, and the spindle then used is bored up to receive the shank of the tap, which is fixed by a side screw. This machine insures the rectangular position of the several parts, and the power is applied by the direct rotation of a hand wheels. It will be gathered from the foregoing remarks, that the die- SCREW-CUTTING TOOLS. 439 stock is an instrument of most extensive use, and it would indeed almost appear as if every available construction bad been tried, with a general tendency to foster the cutter, and to expunge the surface friction or rubbing action; by the excess of which latter the labor of work is greatly increased, and risk is incurred of stretching the thread. Figures 483 and 484 show a shaping machine, built at the Lowell Machine Shop, Lowell, Mass. Many of the machines built at the Lowell Machine Shop, were much improved by W. B. Bennet. This shaping and planing instrument will plane either flat or curved surfaces. The tool bar is moved by a variable crank adjustable to any length of motion not exceeding eight inches. It has a self-acting horizontal and circular feed motion, with a hand-feed motion for internal curves. Figs. 485, 486 show a gear-cutting machine manufactured at the Lowell Machine Shop, Lowell, Massachusetts. The dividing plate is forty-eight inches in diameter. This machine will cut every number of teeth up to 133, and every even number to 268, also 272, 276, and 360 teeth. The cutter stock is so arranged as to move either horizontally or vertically, or at any angle, so as to cut bevel, spur, and spiral wheels and gearing. Screws Cut by Hand in the Common Lathe. —Great num¬ bers of screws are required in works of wood, ivory and metal, that cannot be cut with the taps and dies, or the other apparatus hitherto considered. This arises from the nature of the materials, the weakness of the forms of the objects, and the accidental pro¬ portions of the screws, many of which are comparatively of very large diameter and inconsiderable length. These, and other cir¬ cumstances, conspire to prevent the use of the diestocks for objects such as the screws of telescopes and other slender tubes, those on the edges of disks, rings, boxes, and very many similar works. Screws of this latter class are frequently cut in the lathe with the ordinary screw tool, and by dexterity of hand alone; there is little to be said in explanation of the apparatus and tools, which then consist solely of the lathe with an ordinary mandrel incapable of traversing endways, and the screw tools or the chasing tools, with the addition of the arm rest. The screw tool held at rest would make a series of rings, because at the end of the first revolution- of the object, the points ABC of the tool would fall exactly into the scratches ABC commenced respectively by them. But if, in its first revolution, the tool is shifted exactly the space between two of its teeth, at the end of the revolution, the point B of the tool drops into the groove made by the point A, and so with all the others, and a true screw is formed, or a continuous helical line, which appears in steady lateral motion during the revolution of the screw in the lathe. It is likely the tool will fail exactly to drop into the groove, but 440 THE PRACTICAL METAL-WORKER’S ASSISTANT. if the difference be inconsiderable, a tolerably good screw is never¬ theless formed; as the tool being moved forward as equally as the hand will allow, corrects most of the error. But if the difference be great, the tool finds its way into the groove with an abrupt break in the curve; and during the revolution of the screw, as it progresses it also appears to roll about sideways, instead of being quiescent, and is said by workmen to be “ drunkthis error is frequently beyond correction. It sometimes happens that the tool is moved too rapidly, and that the point C drops into the groove commenced by A; in this case the coarseness of the groove is the same as that of the tool, but the inclination is double that intended, and the screw has a double thread, or two distinct helices instead of one; the tool may pass over three or four intervals and make a treble or quadruple thread, but these are the results of design and skill, rather than of accident. On the other hand, from being moved too slowly, the point B of the tool may fail to proceed so far as the groove made by A, but fall midway between A and B; in this case the screw has half the rise or inclination intended, and the grooves are as fine again as the tool; other accidental results may also occur which it is unnecessary to notice. On Cutting Screws in Lathes with Traversing Mandrels. •—One of the oldest, most simple, and general apparatus for cutting short screws in the lathe, by means of a mechanical guidance, is the screw -mandrel or Gravers my-mandrel, which appears to have been known almost as soon as the iron mandrel itself was introduced. Fig. 487. Figure 487 is copied from an old French mandrel mounted m a wooden frame, and with tin collars cast in two parts; the upper halves of the collars are removed to show the cylindrical necks of the mandrel, upon the shaft of which are cut several short screws. In ordinary turning, the retaining key k, which is shown detached in the view k ', prevents the mandrel from traversing, as its angular SCREW-CUTTING TOOLS. 441 and circular ridge enters the groove in the mandrel; but although not represented, each thread on the mandrel is provided with a similar key, except that their circular arcs are screw-form instead of angular. In screw cutting, k is depressed to leave the mandrel at liberty; the mandrel is advanced slightly forward, and one of the screw-keys is elevated by its wedge until it becomes engaged with its corresponding guide-screw, and now as the mandrel revolves, it also advances or retires in the exact path of the screw selected. The modern screw-mandrel lathe has a cast-iron frame, and hardened steel collars which are not divided; the guide screws are fitted as rings to the extreme end of the hardened steel mandrel, and they work in a plate of brass, which has six scollops, or semi¬ circular screws upon its edge. When this mandrel is used for plain turning, its traverse is prevented by a cap which extends over the portion of the mandrel protruding through the collars. In cutting screws with either the old or modern screw-mandrel, the work is chucked, and the tool is applied, exactly in the man¬ ner of turning a plain object; but the mandrel requires an alter¬ nating motion backwards and forwards, somewhat short of the length of the guide screw; this is effected by giving a swinging motion or partial revolution to the foot wheel. The tool should retain its place with great steadiness, and it is therefore often fixed in the sliding rest, by which also it is then advanced to the axis of the work with the progress of the external screw; or by which it is also removed from the centre in cutting an internal screw. To cut a screw exceeding the length of traverse of the mandrel, the screw tool is first applied at the end of the work, and when as much has been cut as the traverse will admit, the tool is shifted the space of a few threads to the left, and a further portion is cut; and this change of the tool is repeated until the screw attains the full length required. When the tool is applied by hand, it readily assumes its true position in the threads; when it is fixed in the slide rest, its adjustment requires much care. In screwing an object which is too long to be attached to the mandrel by the chuck alone, its opposite extremity is sometimes supported by the front centre or popit-head; but the centre point must then be pressed up by a spring, that it may yield to the advance of the mandrel: this method will only serve for very slight works, as the pressure of the screw-tool is apt to thrust the work out of the centre. It is a much stronger and more usual plan to make the extremity or some more convenient part of the work cylindrical, and to support that part within a stationary cylindrical bearing, or collar plate, which retains the position of the work not¬ withstanding its helical motion, and supplies the needful resistance against the tool. The amateur who experiences difficulty in cutting screws flying, or with the common mandrel and hand-tool unassistedly, will find the screw-mandrel an apparatus by far the most generally convenient for those works, in wood, ivory, and metal turning, to which the 442 THE PRACTICAL METAL-WORKER’S ASSISTANT. screw box and the taps and dies are inapplicable; for the screw- mandrel requires but a very small change of apparatus, and what¬ ever may be the diameter of the work, it insures perfect copies of the guide screws, the half dozen varieties of which will be found to present abundant choice as to coarseness, in respect to the ordi¬ nary purposes of turning. On Cutting Screws in Lathes with Traversing Tools.—A great number of the engines for cutting screws, and also of the other shaping and cutting engines now commonly used, are clearly to be traced to a remote date, so far as their principles are con¬ cerned. For instance, the germs of many of these cutting machines, in which the principles are well developed, will be found in the primitive rose engine machinery with coarse wooden frames, and arms, shaper plate, cords, pulleys, and weights, described in the earliest works on the lathe, whilst many are as distinctly but more carefully modeled in metal, in the tools used in clock and watch making, many of which have also been published. The principles of these machines being generally few and simple, admit of but little change; but the structures, which are most diversified, nay, almost endless, have followed the degrees of excel- Fig. 488. lence of the constructive arts at the periods at which they have been severally made, combined with the inventive talent of their projectors. In most of the screw-cutting machines a previously-formed screw is employed to give the traverse; such are copying machines, and will form the subject of the present section; and a few other SCREW-CUTTING TOOLS. 443 engines serve to originate screws, by tbe direct employment of an inclined plane, or the composition of a rectilinear and a circular motion. The earliest screw-lathe known to the author bears the date of 1569, and this curious machine, which is represented in Fig. 488, is thus described by its inventor, Besson: “ Esplce de Tour en nulle part encore veue et qui n'est sans subtilite, pour engraver petit ci petit la Vis cl Ventour de tout Figure ronde et solide, voire mesmes ovale.” The tool is traversed alongside the work by means of a guide- screw, which is moved simultaneously with the work to be operated upon, by an arrangement of pulleys and cords too obvious to require explanation. It is however worthy of remark, that bad and im¬ perfect as the constructive arrangement is, this early machine is capable of cutting screws of any pitch, by the use of pulleys of different diameters; and right and left-hand screws at pleasure, by crossing or uncrossing the cord; and also that in this first machine the inventor was aware that a screw-cutting-lathe might be used upon elliptical, conical, and other solids. The next illustration, Fig. 489, represents a machine described as Fig. 489. “A Lathe in which without the common art all sorts of screws and other curved lines can be madethis was invented by M. Grand- jean prior to 1729. The constructive details of this machine, which are also sufficiently apparent, are in some respects superior to those in Besson’s; but the two are alike open to the imperfec¬ tion due to the transmissions of motion by cords; and Grandjean’s is additionally imperfect, as the scheme represented will fail to produce an equable traverse of the mandrel compared with its revolution, owing to the continual change in the angular relations between the arms of the bent lever, and the mandrel and cord respectively. Sometimes the spiral board or templet s, is attached 444 THE PRACTICAL METAL-WORKER’S ASSISTANT. to the bent lever to act upon the end of the mandrel; this also is insufficient to produce a true screw in the manner proposed. Several of the engines for cutting screws appear to be derived from those used for cutting fusees, or the short screws of hyperbo¬ lical section, upon which the chains of clocks and watches are wound, in order to counteract the unequal strength of the different coils of the spiral springs. The fusee engines, which are very numerous, have in general a guide-scrhw from which the traverse of the tool is derived, and the illustration, Fig. 490, selected from an old work published in 1741, is not only one of the earliest, but also of the most exact of this kind; and it exhibits likewise the primitive application of change wheels, for producing screws of varied coarseness from one original. This instrument is nearly thus described by Thiout: “A lathe which carries at its extremity two toothed wheels; the upper is attached to the arbor, the clamp at the end of which holds the axis of the fusee to be cut, the opposite extremity is retained by the centre; the fusee and arbor constitute one piece, and are turned by the winch handle. The lower wheel is put in movement by the upper, and turns the screw which is fixed in its centre; the nut can traverse the entire length of the screw, and to the nut is strongly hinged the lever that holds the graver or cutter, and which is pressed up by the hand of the workman. Several pairs of wheels are required, and the smaller the size of that upon the mandrel the less is the interval between the threads of the fusee.” Fig. 490. In the general construction of the fusee engine, the guide-screw and the fusee are connected together on one axis, and are moved by the same winch handle; the degree of fineness of the thread on the fusee is then determined by the intervention of a lever gener¬ ally of the first order; a great variety of constructions have been made on this principle. Three are described in Thiout’s Treatise: namely, in plates 25, 26, and 27, the first by Regnaud de Chaalon. The mode of action will be moie clearly seen in the next figure, SCREW-CUTTING TOOLS. 445 wherein precisely the same movements are applied to the lathe for the purpose of cutting ordinary screws. The apparatus now referred to is that invented by Mr. Healey of Dublin, an amateur; it is universal, or capable within certain limits of cutting all kinds of screws, either right or left-handed, and is represented in plan in Fig. 491, in which C is the chuck which carries the work to be screwed, and t is the tool which lies upon r r' the lathe-rest, that is placed at right angles to the bearer, and is always free to move in its socket s, as on a centre, because the binding screw is either loosened or removed. On the outside of the chuck C is cut a coarse guide screw, which we will suppose to be right-handed. The nut n n, wdiich fits the screw of the chuck, is extended into a long arm, and the latter communicates with the lathe-rest by the connecting rod c c. As the lathe revolves backwards and forwards the arm n (which is retained horizontally by a guide pin g) traverses to and fro as regards the chuck and work, and causes the lathe-rest r r', to oscillate in its socket s. The distance s t being half s r', a right-handed screw of half the coarseness of the guide will be cut; or the tool being nearer to, and on the other side of, the centre s, as in the dotted position t', a finer and left-hand screw will be cut. The rod c c may be attached indiffer¬ ently to any part of n n, but the smallest change of the relation of s t to s r' would mar the correspondence of screws cut at different periods, and there¬ fore t and r should be united by a swivel-joint capable of being fixed at any part of the lathe-rest r r'. The apparatus represented in plan in Figs. 492 and 493, although it does not present the universality of the last, is quite correct in Figs. 492 493. Fig. 491. its action; it is evidently a combination of the fixed mandrel, and tl e old screw mandrel, Fig. 487. Four different threads are cut on tl.e tube which surrounds the mandrel, and the connection between 446 THE PRACTICAL METAL-WORKER’S ASSISTANT. the guide screw and the work is by the long bar b b, which carries at the one end a piece g filed to correspond with the thread, and at the other a socket in which is fixed a screw tool t, corresponding with the guide at the time employed. The lathe revolves with continuous motion; and the long bar or rod being held by the two hands in the position shown, the guide g and the tool t are traversed simultaneously to the left by the screw guide; and when the tool meets the shoulder of the work both hands are suddenly withdrawn and the bar is shifted to the right for a repetition of the cut, and so on until the completion of the screw. The guide g is supported upon the horizontal plate p, which is parallel with the mandrel, and the tool t lies upon the lathe rest r. Beneath the tool is a screw which rubs against the lathe rest r, and serves as a stop ; this makes the screw cylindrical or conical, according as the rest is placed parallel or oblique. For the inter¬ nal screw the tool is placed parallel with the bar, as in Fig. 493 ; and the check screw is applied on the side towards the centre against a short bar parallel with the axis of the lathe. None of the machines which have been hitherto described are proper for cutting the accurate screws, of considerable length or of great diameter, required in the ordinary works of the engineer; but these are admirably produced by the screw-cutting lathes, in which the traverse of the tool is effected by a long guide-screw, connected with the mandrel that carries the work by a system of change wheels after the manner employed a century back, as in Fig. 490. The accuracy of the result now depends almost entirely upon the perfection of the guide-screw, and which we will suppose to possess very exactly 2, 4, 5, 6, or some whole number of threads in every inch, although we shall for the present pass by the methods employed in producing the original guide-screw, which thus serves for the reproduction of those made through its agency. The smaller and most simple application of the system of change wheels for producing screws is shown in Fig. 494. The work is attached to the mandrel of the lathe by means of a chuck, to which is also affixed a toothed-wheel marked M, therefore the mandrel, the wheel and the work partake of one motion in common. The tool is carried by the slide-rest, the principal slide of which is placed parallel with the axis of the lathe as in turning a cylinder, and upon the end of the screw near the mandrel is attached a tooth wheel S, which is made to engage in M, the wheel carried by the mandrel. As the wheels are supposed to contain the same number of teeth, they will revolve in equal times, or make continually turn for turn; and therefore in each revolution of the mandrel and work, the tool will be shifted in a right line, a quantity equal to one thread of the guide-screw, and so with every coil throughout its extent of motion. Consequently the motion of the two axes being always equal and continuous, the screw upon the work will SCREW-CUTTING TOOLS. 447 become an exact copy of the guide-screw contained in the slide- rest, that is, as regards the interval between its several threads, its total length, and its general perfection. Fig. 494. But the arrows in M and S denote that adjoining wheels always travel in opposite directions; when, therefore, the mandrel and slide-rest are connected by only one pair of wheels, as in Fig. 494, the direction of the copy screw is the reverse of that of the guide. The right-hand screw being far more generally required in me¬ chanism, when the combination is limited to its most simple form, of two wheels only, it is requisite to make the slide-rest screw left- handed, in order that the one pair of wheels may produce right- hand threads. But a right-hand slide-rest screw may be employed to produce at pleasure both right and left-hand copies, by the introduction of either one or two wheels, between the exterior wheels M and S, Fig. 494. Thus, one intermediate axis, to be called I, would pro¬ duce a right-hand thread ; two intermediate axes, I I, would pro¬ duce a left-hand thread, and so on alternately; and this mode, in addition, allows the wheels M and S to be placed at any distance asunder that circumstances may require. In making double thread screws the one thread is first cut, the wheels are then removed out of contact, and the mandrel is moved exactly half a turn before their replacement, the second thread is then made. In treble threads the mandrel is twice disengaged, and moved one-third of a turn each time, and so on. When the intermediate wheels are employed, it becomes neces¬ sary to build up from the bearers some description of pedestal, or from the lathe-head some kind of bracket, which may serve to carry the axes or sockets upon which the intermediate wheels re¬ volve. These parts have received a great variety of modifica¬ tions, three of which are introduced in the diagrams Figs. 495 to 497 ; the wheels supposed to be upon the mandrel are situated on the dotted line M M, and those upon the slide-rest on the line S S. 448 TIIE PRACTICAL METAL-WORKER’S ASSISTANT. The rectangular bracket in Fig. 495 has two straight mortises; by the one it is bolted to the bearers of the lathe, and by the other it carries a pair of wheels, whose pivots are in a short piece, which may be fixed at any height or angle in the mortise, so that one or both wheels, I I, may be used according to circumstances. In Fig. 496, the intermediate wheel, or wheels, are carried by a radial Figs. 495 496 497. arm, which circulates around the mandrel, and is fixed to the lathe head by a bolt passed through the circular mortise. In Fig. 496, a similar radial arm is adjustable around the axis of the slide-rest screw, in the fixed bracket. Sometimes the wheel supposed to be attached to the slide-rest, is carried by the pedestal or arm, fixed to the bed or headstock of the lathe; in order that a shaft or spindle may proceed from the wheel S, and be coupled to the end of the slide rest screw, by a hollow square or other form of socket, so as to enable the rest to be placed at any part of the length of the bearer, and permit a screw to be cut upon the end of a long rod. The shaft sometimes terminates at each end in universal joints, in order to accommodate any trifling want of parallelism in the parts ; if, however, the shaft be placed only a few degrees oblique, the motion transmitted ceases to be uniform, or it is accelerated and retarded in every revolution, which is fatal in screw cutting. This change in the position of the slide-rest is also needful in cutting a screw which exceeds the length the rest can traverse, as such long screws may then be made at two or more distinct opera¬ tions; before commencing the second trip the tool is adjusted to drop very accurately into the termination of that portion of the screw cut in the first trip, which requires very great care, in order that no falsity of measurement may be discernible at the parts where the separate courses of the tool have met. This method of proceeding has, however, from necessity been followed in produc¬ ing some of the earliest of the long regulating screws, which have served for the production of others by a method much less liable to accident, namely, when the cut is made uninterruptedly through¬ out the extent of the work. SCREW-CUTTING TOOLS. 449 In the larger application of the system of change-wheels, the entire bed of the lathe is converted into a long slide-rest, the tool carriage with its subsidiary slides for adjusting the position of the tool, then traverses directly upon the bed; this mode has given rise to the name “ traversing or slide-lathe,” a machine which has received, and continues to receive, a variety of forms in the hands of different engineers. It would be tedious and unnecessary to attempt the notice of their different constructions, which neces¬ sarily much resemble each other; more especially as the principles and motives, which induce the several constructions and practices, rather than the precise details of apparatus, are here under con¬ sideration. The arrangement for the change-wheels of a screw-cutting lathe given in Fig. 498, resembles the mode frequently adopted. The guide-screw extends through the middle of the bed, and projects at the end; there is a clasp nut, so that when required, the slide-rest may be detached from the screw and moved independently of the same. The train of wheels is placed at the left extremity of the lathe; there is a radial arm which circulates around the end of the main screw, the arm has one or two straight mortises, in which are fixed the axes of the intermediate wheels, and there are two circular mortises, by which the arm may be secured to the lathe bed, in any required position, by its two binding screws. On comparing the relative facilities for cut¬ ting screws, either with the slide-rest furnish¬ ed with a train of wheels, or with the travers¬ ing or screw-cutting lathe, the advantage will be found greatly in favor of the latter; for in¬ stance :— With the slide-rest arrangement, Fig. 494, the work must be always fixed in a chuck to which the first ot the change-wheels can be also attached; the wheels frequently prevent the most favorable position of the slides from being adopted; and in cutting hollow screws the change-wheels entirely prevent the tool carriage of the slide-rest from being placed oppo¬ site to the centre, and therefore awkward tools, bent to the rectan¬ gular form, must be then used. The slide-rest also requires fre¬ quent attention to its parallelism with the axis of the lathe, or the screws cut will be conical instead of cylindrical. With the traversing lathe, from the wheels being at the back of the mandrel, no interference can possibly arise from them, and consequently the work may be chucked indiscriminately on any of the chucks of the lathe ; every position may be given to the slide carrying the tool, and therefore the most favorable, or that nearest to the work, may be always selected, and the tools need not be crooked. As the tool carriage traverses at once on the 29 450 THE PRACTICAL METAL-WORKER’S ASSISTANT. bearers of the lathe, the adjustment for parallelism is always true, and the length of traverse is greatly extended. The system of screw-cutting just explained is very general and practical: for instance, one long and perfect guide-screw (which we will call the guide), containing 2, 4, 6, 8, 10, or any precise number of threads per inch having been obtained, it becomes very easy to make from it subsequent screws, (or copies ) which shall be respectively coarser and finer in any determined degree. The principle is, that whilst the copy makes one revolution, the guide must make so much of one revolution, or so many, as shall traverse the tool the space required between each thread of the copy; and this is accomplished by selecting change-wheels in the proportions of these quantities of motion, or in other words, in the proportion required to exist between the guide-screw and the copy. In explanation, we will suppose the guide to have 6 threads per inch, and that copies of 18, 14, 12J, 8, 3, 2, 1, threads per inch are required ; the two wheels must be respectively in the proportions of the fractions T %, T fi ? , |, §, |, f, f, the guide being constantly the numerator. The numerator also represents the wheel on the mandrel, and the denominator that on the guide-screw ; any multi¬ ples of these fractions may be selected for the change-wheels to be employed. For example, any multiples of T fi g , as Kf, §*, etc., will pro¬ duce a screw of 18 threads per inch, the first and finest of the group; and any multiples of as, fj?, s 2 0 °, etc., will produce a screw of 1 thread per inch, which is the last and coarsest of those given. Screws 2, 4, or 6 times as fine will result from the interposing a second pair of wheels, respectively multiples of 4, l, and placed upon one axis. For instance, the pair of wheels § |, used for producing a screw of 18 threads per inch, would, by the combination A, produce a copy three times as fine, or a screw of 54 threads per inch. Fig. 496 represents the wheels referred to in combination A, and Fig. 497 those in combination B. M 24 Combination A. Interm. S -60 20-72 Combination B. Combination C. M Interm. S M Interm. S. 120 24 27 —53 72 20 39 107 And the wheels Vo° used f° r the screw of one thread per inch, would by the combination B, produce a copy three times as coarse, or of three inches rise. Whatsoever the value of the intermediate wheels, whether multiplies of f, |, f, etc., they produce screws.re¬ spectively of f, |, the pitches of those screws, which would be otherwise obtained by the two exterior wheels alone; and in this manner a great variety of screws, extending over a wide range of pitch, may be obtained from a limited number of wheels. For instance, the apparatus Holtzapffel and Co. have recently SCREW-CUTTING TOOLS. 451 added to the slide rest, after the manner of Figs. 494 and 496, has a series of about fifteen wheels, of from 15 to 144 teeth, employed with a screw of 10 threads per inch: several hundred varieties of screws may be produced by this apparatus, the finest of which has 320 threads per inch, the coarsest measures 7 5 inches in each coil or rise: and the screws may be made right or left-handed, double, triple, quadruple, or of any number of threads. The finest com¬ binations are only useful for self-acting turning; those of medium coarseness serve for all the ordinary purposes of screws; whilst the very coarse pitches are much employed in ornamental works, and in cutting these coarse screws the motion is given to the slide- rest screw, and by it communicated to the mandrel. The value of any combination of wheels may be calculated as vulgar fractions, by multiplying together all the driving wheels as numerators, and all the driven wheels as denominators, adding also the fractional value, or pitch, of the guide-screw; thus in the first example A:— 24 x 20 x 1 = 480 1 — — - -or reduced to its lowest terms —. 60 x 72 x 6 = 25920 54 The fraction denotes that A th of an inch is the pitch of the screw, or the interval from thread to thread; also that it has 54 threads in each inch, and which is called the rate of the screw. And in C, the numbers in which example were selected at ran¬ dom, the screw would be found to possess rather more than 35 threads per inch. The fractions should be reduced to their lowest terms before cal¬ culation, to avoid the necessity for multiplying such high numbers. Thus the first example would become reduced to J x | x ^ = 5 V, and would be multiplied by inspection alone, as the numerators and denominators may be taken crossways if more convenient; thus f I is equal to J, and §g is also equal to J, fractions which are smaller than ? and T s g , the lowest terms respectively of §$ and the second case could not be thus treated, and the whole numbers must there be multiplied, as they will not admit of reduction. Other details will be advanced, and tables of the combinations of the change-wheels will be also given, in treating of the practice of cutting screws. 27 x 39 x 1 1114 1 — — - -or reduced to its lowest terms-. 53 x 107 x 6 39026 35 T Hu In imitation of the method of change-wheels, the slide-rest screw is sometimes moved by an arrangement of catgut bands, resem¬ bling that represented in Besson’s screw-lathe, page 442. One band proceeds from the pulley on the mandrel to a spindle overhead having two pulleys, and a second cord descends from this spindle to a pulley on the slide-rest. This apparatus has been 452 THE PRACTICAL METAL-WORKER’S ASSISTANT. applied to catting the expanding horn snakes. See Manuel de Tour¬ neur, first edit., 1796, vol. ii., plate 21; and second edit., 1816, vol. ii., plate 16. i The method offers facility in cutting screws of various pitches, by changing the pulleys, and also either right or left-hand screws, by crossing or uncrossing one of the bands. The plan is unexceptionable, when applied for traversing the tool slowly for the purpose of turning smooth cylinders, or sur¬ faces (which is virtually cutting a screw or spiral of about 100 coils in the inch); and in the absence of better means, pulleys and bands are sometimes used in matching screws of unknown or irreg¬ ular pitches, by the tedious method of repeated trials; as on slightly redncing, with the turning tool, the diameter of either of the driving pulleys, the screw or the work becomes gradually finer; and reducing either of the driven pulleys makes it coarser; but the mode is scarcely trustworthy, and is decidedly far inferior to its descendant, or the method of change-wheels. The screw tools, or chasing tools, employed in the traversing lathes for cutting external and internal screws, resemble the fixed tools generally, except as regards their cutting edges; the follow¬ ing figures, 499 to 501, refer to angular threads, and 502 and 503 to square threads. Angular screws are sometimes cut with the single point, Fig. 499, a form which is easily and correctly made; the general angle of the point is about 55° to 60°, and when it is only allowed to cut on one of its sides or bevels, it may be used fearlessly, as the shavings easily curl out of the way and escape. But when both sides of the single point tool are allowed to cut, it requires very much more cautious management; as in the latter case, the duplex shav¬ ings being disposed to curl over opposite ways, they pucker up as an angular film, and in fine threads they are liable to break the point of the tool, or to cause it to dig into, and tear the work. Sometimes, also, a fragment of the shaving is wedged so forcibly into the screw by the end of the tool, that it can only be extricated by a sharp chisel and hammer. In cutting angular screws, it is very much more usual and ex¬ peditious to employ screw tools with many points, which are made in the lathe by means of a revolving cutter or hob, Figs. 447 and 448, page 427. Screw tools with many points, are always required for those angular threads which are rounded, at the top and bottom, and which are thence called rounded or round threads. To the screw tool for rounded threads is given the profile of Fig. 500, which construction allows the tool to be inverted, so that the edges may be alternately used for the purpose of equalizing the section of the thread. In making the tool 500, the hob (which is dolled) is put between centres in the traversing lathe, and those wheels are applied which would serve to cut a screw of the same pitch as the hob; the bar of steel is then fixed in the slide-rest, so that the dotted line or the axis of the tool intersects the centre of SCREW-CUTTING TOOLS. 453 the hob. The tool is afterwards hollowed on both sides with the file, to facilitate the sharpening, and it is then hardened. In using the tool, it is depressed until either edge comes down to the radius, proceeding from the ( "black ) circle, which is supposed to represent the screw to be cut; the depression gives the required penetration to the upper angle, and removes the lower out of contact. In the chasing tool represented in Fig. 501, the cutter, c, is made as a ring of steel which is screwed internally to the diameter of the bolt, and turned externally with an undercut groove, for the small screw and nut by which it is held in an iron stock, s, formed of a corresponding sweep; for distinctness the cutter and screw are also shown detached. The centre of the curvature of the tool is placed a little below the centre of the lathe, to give the angle of Screw Tools for Angular Threads . Figs. 499 Screw Tools for Square Threads. 902 H -^ _ =u- separation or penetration; and after the tool has been ground away in the act of being sharpened, it is raised up, until its points touch a straight-edge applied on the line a a of the stock; this denotes the proper height of centre, and also the angle to which the tool is intended to be hooked, namely, 10 degrees: each ring makes four or five cutters, and one stock may be used for several diameters of thread. Angular thread screws are fitted to their corresponding nuts simply by reduction in diameter; but square thread screws require attention both as to diameter and width of groove, and are conse¬ quently more troublesome. Square thread screws are in general of twice the pitch, or double the obliquity, of angular screws of 454 THE PRACTICAL METAL-WORKER’S ASSISTANT. the same diameters; and, consequently, the interference of angle before explained as concerning the die-stocks, refers with a two¬ fold effect to square threads, which are in all respects much better produced in the screw-cutting lathe. The ordinary tool for square thread-screws is represented in two views in Fig. 502 ; the shaft is shouldered down so as to ter¬ minate in a rectangular part which is exactly equal to the width of the groove. In general the end alone of the tool is required to cut, and the sides are beveled according to the angle of the screw, to avoid rubbing against the sides of the thread. Tools which cut upon the side alone are also occasionally used for' ad¬ justing the width of the groove. In either case it requires con¬ siderable care to maintain the exact width and height of the tool—• the inclination of which should also differ for every change of diameter. To obviate these several inconveniences, the author several years back contrived a tool-holder, Fig. 503, for carrying small blades made exactly rectangular. In height, as at h, the blades are alike, in width, w, they are exactly half the pitch of the threads, and they are ground upon the ends alone. The parallel blades are clamped in the rectangular aperture of the tool socket by the four screws c c; and when the screws s s, which pass through the cir¬ cular mortises in the sockets, are loosened, the swivel-joint and graduations allow the blades to be placed at the particular angle of the thread, which is readily obtained by calculation, and is estimated for the medium depth of the thread, or midway between the extreme angles at the top and bottom. One blade, therefore, serves perfectly for all screws of the same pitch, both right and left-handed, and of all diameters. As the tool exactly fills the groove, it works steadily, and the width of the groove and the height of the centre of the tool are also strictly maintained with the least possible trouble. The depth of the groove, which is generally one-sixth more than its width, is read off with great facility by means of the adjusting-screw of the slide- rest ; especially if, as usual, the screw and its micrometer agree with the decimal division of the inch. The holder, Fig. 503, has been much and satisfactorily used for screws from about 20 to 2 threads per inch; but when the screw is coarse and oblique, compared with its diameter, the blade is ground away to the dotted line in h, and is sometimes beveled on the sides almost to the upper edge, to suit the obliquity of the thread, but without altering the extreme width of the tool. The tools for external screws of very coarse pitch, are necessa¬ rily formed in the lathe by aid of the corresponding wheels and a revolving cutter bar resembling Fig. 415, p. 410. The soft tool is fixed in the slide-rest, and is thereby carried against the revolving cutter bar, 415, which has a straight tool, either pointed or square as the case may be. The end of the screw tool is thus shaped as part of an external screw, the counterpart of that to be cut. The SCREW-CUTTING TOOLS. 455 face of the screw tool is filed at right angles to the obliquity of the thread, and the end and sides are slightly beveled for penetration previously to its being hardened. Internal square threads of small size are usually cut with taps which resemble Fig. 445, p. 424, except in the form of the teeth. When internal square threads are cut in the lathe, the tool assumes the ordinary form of a straight bar of steel with a rectangular point standing off at right angles, in most respects like the com¬ mon pointed tool for inside work. For very deep holes, and for threads of very considerable ob¬ liquity, cutter bars, such as Fig. 415, p. 410, are used. The work and the temporary bearings of the bar are all immovably fixed for the time, and the bar advances through the bearings in virtue of its screw-thread; or otherwise a plain bar, having a cutter only, and not being screwed, may be mounted between centres in the screw lathe, and the work, fixed to the slide-rest, may traverse parallel with the bar by aid of the change-wheels. The cutter bar in some cases requires a ring to fill out the space between itself and the hole, to prevent vibration ; and it is necessary to increase the radial distance of the cutter between each trip, by a set screw, or by slight blows of a hammer. Very oblique inside cutters are turned to their respective forms with a fixed tool, in a manner the converse of that explained above; and some peculiarities of management are required in using them, in order to obtain the under-cut form of the internal thread. In cutting screws in the turning lathe, the tool only cuts as it traverses in the one direction; therefore whilst the cutter is moved backwards, or in the reverse direction, for the succeeding cut, it must be withdrawn from the work. Sometimes the tool is traversed backwards by reversing the motion of the lathe ; and in lathes driven by power, the back motion is frequently more rapid than the cutting motion, to expedite the process; at other times the lathe is brought to rest, the nut is opened as a hinge, so as to become disengaged from the screw, and the slide-rest is traversed backwards by hand, or by a pinion movement, and the nut is again closed on the screw, prior to the succeeding cut. This mode an¬ swers perfectly for screws of the same thread as the guide, and for those of 2, 4, 6, 8 times as coarse or as fine; but for those of 2£, 4J, or any fractional times the value of the guide screw, the clasp nut cannot in general be employed advantageously. The progressive advance of the tool between each cut, is com¬ monly regulated by a circle of divisions or a micrometer on the slide rest screw, which should always correspond with the decimal division of the inch. The substance of the shaving may be pretty considerable after the first entry is made, but it should dwindle av«ay to a very small quantity, towards the conclusion of the screw. To avoid the necessity for taxing the memory with the graduation at which the tool stood when it was withdrawn for the 456 THE PRACTICAL METAL-WORKER’S ASSISTANT. back stroke, the author has been in the habit of employing a micrometer exactly like that on the screw, which is set to the same graduation, and serves as a remembrancer; another method is to employ an arm or stop, which fits on the axis of the screw or handle with stiff friction, but nevertheless allows the tool to be shifted the two or three divisions required for each cut. In the screw lathe used by Mr. Roberts, the nut of the slide- screw instead of being a fixture, is made with two tails as a fork, which embraces an eccentric spindle; by the half rotation of which spindle, the nut together with the adjusting screw, the slide, and the tool, are shifted, as one mass, a fixed distance to and from the centre, between each cut; so as first to withdraw and then to replace the tool. Whilst the tool is running back, the screw is moved by its adjusting screw and divisions, the minute quantity to set in the tool for the succeeding cut, and the continual wear upon the adjust¬ ing screw, as well as the uncertainty of its being correctly moved to and fro by the individual, are each avoided. Sometimes, with the view of saving the time lost in running back, two tools are used, so that the one may cut as the tool slide traverses towards the mandrel, the other in the contrary direction. An arrangement for this purpose, as applied to the screwing of bolts in the lathe, is shown in Fig. 504; f represents the front, and b the back tool, which are mounted on the one slide s s, and all three are moved as one piece by the handle h, which does not require any micrometer. Fig. 504. In the first adjustment, the wedge w, is thrust to the bottom of the corresponding angular notch in the slide s, and the two tools are placed in contact with the cylinder to be screwed. For the first cut, the wedge is slightly withdrawn to allow the tool f to be advanced towards the work; and for the return stroke, the wedge SCREW-CUTTING TOOLS. 457 is again shifted under the observation of its divisions, and the slide s s, is brought forwards, towards the workman, up to the wedge; this relieves the tool f and projects b, which is then in adjustment for the second cut; and so on alternately. The command of the two tools is accurately given by the wedge, which is moved a small quantity by its screw and micrometer, between every alter¬ nation of the pair of tools, by the screw h. In cutting very long screws, the same as in turning long cylin¬ drical shafts, the object becomes so slender, that the contrivance called a backstay is always required for supporting the work in the immediate neighborhood of the tool. The backstay is fixed to the slide plate, or the saddle of the lathe which carries the tool, and is brought as near to the tool as possible; sometimes the dies or bearings are circular, and fit around the screw ; at other times they touch the same at two, three or four parts of the circle only. Some of the numerous forms of this indispensable guide or back¬ stay will hereafter be shown. In using the screw-lathe with a backstay for long screws, it is a valuable and important method, just at the conclusion, to employ a pair of dies in the place usually occupied by the tool; as they are a satisfactory test for exact diameter, and they remove trifling errors attributable to veins and irregularities of the material, which the fixed tool sometimes fails entirely to reduce to the gen¬ eral surface. The tool and backstay may be each considered to be built on the tops of pedestals more or less lofty, and therefore, more susceptible of separation by elasticity, than the pair of dies fixed in a small square frame. It has been judiciously proposed, in effect, to link the backstay and turning tool together, by the employment of a small frame carrying a semicircular die of lignum- vitse, and a fixed turning tool, adjusted by a pressure screw; the frame to be applied either in the hand alone or in the slide rest, and to be inverted so that the shavings may fall away without clogging the cutter. Various Modes of Originating and Improving Screws.— The improvement of the screw has given rise to many valuable schemes and modes of practice, which have not been noticed in the foregoing sections, notwithstanding their collective length. These practices indeed could not consistently have been placed in the former pages of this subject because some of them must be viewed as refinements upon the general methods, the earlier notice of which would have been premature; and others exhibit various combinations of methods pursued by different eminent individuals with one common object, and are therefore too important to be passed in silence, notwithstanding their miscellaneous nature. To render this section sufficiently complete, it appears needful to take a slight retrospective glance of the early and the modern modes of originating screws and screw apparatus; some account of the former may be found in the writings of Pappus, who lived in the fourth century. 45 S THE PRACTICAL METAL-WORKER’S ASSISTANT. In the works of Pappus Alexandrinus, a Greek mathematician of the fourth century, are to be found practical directions for making screws. The process is simply to make a templet of thin brass of the form of a right-angled triangle, the angles of which are made in accord¬ ance with the inclination of the proposed screw. This triangle is then to be wrapped round the cylinder which is to be the desired screw, and a spiral line traced along its edge. The screw is sub¬ sequently to be excavated along this line. Minute practical direc¬ tions are given not only for every step of this process, but also for the division, setting out, and shaping the teeth of a worm-wheel of any required number of teeth to suit the screw. (Vide Pappi Math. Col., lib. viii. prob. xviii.) The progressive stages which may be supposed to have been formerly in pretty general use for originating screws, may be thus enumerated: 1. The first screw-tap may be supposed to have been made by the inclined templet, the file, and screw tool. It was imperfect in all respects, and not truly helical, but full of small irregularities. 2. The dies formed by the above were considerably nearer to perfection, as the multitude of pointed edges of 1 being passed through every groove of the die, the threads of the latter became more nearly equal in their rake or angle, and also in their distances and form. 3. The screw cut with such dies would much more resemble a true helix than 1; but from the irregularities in the first tap, the grooves in the die 2 would necessarily be wide, and their sides, instead of meeting as a simple angle, would be more or less filled with ridges, and 3 would become the exact counterpart of 2. 4. A pointed tool applied in the lathe would correct the form of the thread or groove in 3 without detracting from its improved cylindrical and helical character, especially if the turning tool were gradually altered from the slightly rounded to the acute form in accordance with the progressive change of the screw. The latter is occasionally changed end for end, either in the die-stocks or in the lathe, to reverse the direction in which the tools meet the work, and which reversal tends to equalize the general form of the thread. 5. The corrected screw 4, when converted into a masfer-tap, would make dies greatly superior to 2; it would also serve for cutting up screw tools ; and lastly, 6 . The dies 5 would be employed for making the ordinary screws and working taps; and this completes the one series of screwing apparatus. One original tap having been obtained, it is often made sub¬ servient to the production of others; for example, a screw tool with several points cut over the corrected original 4 would serve for striking in the lathe other master-taps of the same thread but different diameters. The process is so much facilitated by the per¬ fection of the screw tool that a clever workman would thus, with- SCREW-CUTTING TOOLS. 459 out additional correction, strike master-taps sufficiently accurate for cutting up otter dies larger or smaller than 4. Sometimes also the dies 5 are used for marking out original taps a little larger or smaller than 4. As a temporary expedient the screw tool may be somewhat spread at the forge fire to make a tool a little coarser, or it may be upset for one a little finer, and afterwards corrected with a file; or screw tools may be made entirely with the file, and then employed for producing, in the lathe, master-taps of corresponding degrees of coarseness and of all diameters. These are in truth some of the progressive modes by which, under very careful management, great numbers of good useful screwing apparatus have been produced, and which answer perfectly well for all the ordinary requirements of “ binding ” or “attachment' 1 ' 1 screws; or as the cement by which the parts of mechanism and structures generally are firmly united together, but with the power of separa¬ tion and reunion at pleasure. In this comparatively inferior class of screws considerable latitude of proportion may be allowed, and whether or not their pitches or rates have any exact relationship to the inch, is a matter of indiffer¬ ence as regards their individual usefulness; but in superior screws, or those which may be denominated “regulating^ and “micrometri¬ cal' 1 '' screws, it does not alone suffice that the screw shall be good in general character, and as nearly as possible a true helix; but it must also bear some defined proportion to the standard foot or inch, or other measure. The attainment of this condition has been attempted in various ways, to some of which a brief allu¬ sion was made, and a few descriptive particulars will now be offered. The apparatus for cutting original screws by means of a wedge or inclined plane, appears to be derived from the old fusee engine, a drawing of which is given in Fig. 505. In principle it is per¬ fect, and it is also universal within the narrow limitation of its structure. The drawing is the half size of Fig. 1, Plate xvii., of Ferdinand Berthoud’s Essai sur EHorlogerie, Paris, 1763. M. Berthoud says, “ The instrument is the most perfect with which I am acquainted; it is the invention of M. Le Lievre, and it has been reconstructed and improved by M. Gideon Duval.” The templet or shaper plate determines the hyperbolical section of the fusee. The modifica¬ tion, with an inclined plane, is due to Hindley, of York. The handle h gives rotation to the work; and at the same time, by means of the rack r r, and the pinion fixed on its axis, the handle traverses a slide which carries on its upper surface a bar i ; the latter moves on a centre, and may be set at any inclination by the adjusting screw and divisions ; it is then fixed by its clamp ing screws. The slide s carries the tool, and the end of this slide rests against the inclined plane i through the intervention of a saddle or swing piece. The slide and tool are drawn to the left 460 THE PRACTICAL METAL-WORKER’S ASSISTANT. hand by the chain which is coiled round the barrel b, by means of a spiral spring contained within it. Fig. 505. Supposing the bar i i to stand square or at zero, no motion would be impressed on the tool during its traverse, which we will suppose to require 10 revolutions of the pinion. But if the bar were inclined to its utmost extent, so that we may suppose the one end to project exactly one inch beyond the other, in reference to the zero line or the path of the slide, then during the 10 revolu¬ tions of the screw the tool would traverse one inch, or the differ¬ ence between the ends of the inclined bar i ; and it would thereby cut a screw of the length of one inch, or the total inclination of the bar, and containing ten coils or threads. But the inclination of the bar is arbitrary, and may be any quantity less than one inch, and may lean either to the right or left; consequently the instrument may be employed in cutting all right or left-hand screws, not exceeding 10 turns in length, nor measur¬ ing in their total extent above one inch, or the maximum inclination of the bar. The principle of this machine may be considered faultless; but in action it will depend upon several niceties of construction, par¬ ticularly the straightness of the slide and inclined bar, the equality of the rack and pinion, and the exact contact between the tool slide and the inclined plane. These difficulties augment very rapidly with the increase of dimensions; and probably the machine made by Mr. Adam Reid exclusively for cutting screws, is as large as SCREW-CUTTING TOOLS. 461 can be safely adopted. Tlie inclined plane is 44 inches long, but the work cannot exceed l, 6 0 ths inch diameter, 2J inches long, or ten threads in total length. The application of the inclined plane to cutting screws is therefore too contracted for the ordinary wants of the engineer, which are now admirably supplied by the screw¬ cutting lathes with guide screws and change wheels. The accuracy of screws has always been closely associated with the successful performance of engines for graduating circles and right lines, and the next examples will be extracted from the pub¬ lished accounts of the dividing engines made by Mr. Ramsden. This eminent individual received a reward from the Board of Longitude, upon the condition that he would furnish for the benefit of the public a full account of the methods of constructing and using his dividing machines, and which duly appeared in the following tracts: “ Description of an Engine for Dividing Mathe¬ matical Instruments, by Ramsden, 4to., 1777.” Also, “ Descrip¬ tion of an Engine for Dividing Straight Lines, by Ramsden, 4to., 1779, from which the following particulars are extracted : The circular dividing engine consisted of a large wheel moved by a tangent screw; the wheel was 45 inches diameter, and had 2160 teeth, so that six turns of the tangent screw moved the circle one degree; the screw had a micrometer, and also a ratchet-wheel of 60 teeth—therefore one tooth equalled one-tenth of a minute of a degree. The screw could be moved a quantity equal to one single tooth, or several turns and parts, by means of a cord and treadle, so that the circular works attached to the dividing wheel could be readily graduated into the required numbers by setting the tangent screw to move the appropriate quantities. The divid¬ ing knife or diamond point always moved on one fixed radial line by means of a swing-frame. “In ratching or cutting the wheel,” says Mr. Ramsden, “the circle was divided with the greatest exactness I was capable of, first into 5 parts, and each of these into 3; these parts were then bisected 4 times; this divided the wheel into 240 divisions, each intended to contain 9 teeth. The ratching was commenced at each of the 240 divisions by setting the screw each time to zero by its micrometer, and the cutter frame to one of the great divisions by the index; the cutter was then pressed into the wheel by a screw, and the cutting process was interrupted at the'ninth revolution of the screw. It was resumed at the next 240th division (or nine degrees off), as at first, and so on. This process was repeated three times round the circle, after which the ratching was continued uninterruptedly around the wheel about 300 times; this completed the teeth with satisfactory accu¬ racy. The tangent screw was subsequently made, as explained in the text. The first application of the tangent screw and ratchet to the pur¬ poses of graduation, appears to have been in the machine for cui- ting clock and watch wheels, by Pierre Fardoil; see plate 23 of 462 THE PRACTICAL METAL-WORKER'S ASSISTANT. Thiout’s Trade d' Horlogerie, etc. Paris, 1741. At page 55 is given a table of ratchets and settings for wheels with from 102 to 800 teeth. In Mr.Ramsden’s description of his dividing engines for circles, he says: '‘Having measured the circumference of the dividing wheel, I found it would require a screw about one thread in a hundred coarser than the guide-screw.” He goes on to explain that the guide-screw moved a tool fixed in a slide carefully fitted on a triangular bar, an arrangement equivalent to a slide-rest and fixed tool: the screw to be cut was placed parallel with the slide, and the guide-screw and copy were connected by two change wheels of 198 and 200 teeth (numbers in the proportion required between the guide and copy), with an in¬ termediate wheel to make the threads on the two screws in the same direction. As no account is given of the mode in which the guide- screw was itself formed, it is to be presumed it was the most correct screw that could be obtained, and was produced by some of the means described in the beginning of the present sections. Mr. Ramsden employed a more complex apparatus in originat¬ ing the screw of his dividing engine for straight lines, which it was essential should contain exactly 20 threads in the inch; a con¬ dition uncalled for in the circular engine, in which the equality of the teeth of the wheel required the principal degree of attention. This second screw-cutting apparatus, which may be viewed as an offspring of the circular dividing engine, is represented in plan, in Fig. 509, and may be thus briefly explained. Fig. 509. The guide-screw G is turned round by the winch, and in each revolution moves the larger tangent wheel one tooth: the tangent wheel has a small central box or pulley p, to which is attached the one end of an elastic slip of steel, like a watch-spring; the other end of the slip is connected with the slide s, that carries the tool t, in a right line besides the screw C, which latter is the piece to be cut; and C is connected with the guide-screw G, by a bevel pinion and wheel g, and c, as 1 to 6. SCREW-CUTTING TOOLS. 463 To proportion the traverse of the tool to the interval or pitch of the screw, two dots were made on the slide s, exactly five inches asunder; and in that space the screw should contain 100 coils, to be brought about by 600 turns of the handle. The guide-screw was moved that number of revolutions, and the diameter of p was reduced by trial, until the 600 turns traversed the slide exactly from dot to dot; these points were observed at the time through a lens placed in a fixed tube, and having a fine silver wire stretched diametrically across the same as an index. See “ Description of an Engine for Dividing Straight Lines.” In the construction of his dividing engine for straight lines, Ramsden very closely followed his prior machine for circular lines, if we conceive the wheel spread out as a rectangular slide. On the one edge of the main slide which carried the work, was cut a screw-form rack, with twenty teeth per inch, which was moved by a short fixed screw of the same pitch, by means of ratchets of 50, 48, or 32 teeth respectively; the screw could be moved a quantity equal to one single tooth, or to several turns and parts, by means of a treadle. To obtain divisions which were incompa¬ tible with the sub-division of the inch into 1000, 960 or 640 parts, the respective values of one tooth, the scale was laid on the slide at an angle to the direction of motion; when the swing frame was placed to traverse the knife at right angles to the path of the slide, the graduations were lengthened; when the knife was traversed at right angles to the oblique position of the scale being divided, they were shortened. This was to a small degree equivalent to having a screw of variable length. In cutting the screw-form teeth of the rectilinear dividing engine, the entire length, namely, 25.6 inches, was first divided very carefully by continual bisection into spaces of eight-tenths of an inch, by hand as usual, and the screw-cutter was placed at zero at each of these divisions, pressed into the edge of the slide, and revolved sixteen times; after three repetitions at each of the principal spaces, the entire length was ratched continu¬ ously until the teeth were completed. With the view of producing screws of exact values, engineers have employed numerous modifications of the chain or band of steel, the inclined knife, the inclined plane, and indeed each of the known methods, which, however, were remodelled as additions to the ordinary turning-lathe with a triangular bar. Some give a preference to the inclined knife, applied against a cylinder revolving in the lathe, by means of a slide running upor. the bar of the lathe ; which, besides being very rapid, reduced the mechanism to its utmost simplicity. This made the process to de¬ pend almost alone on the homogeneity of the materials, and on the relation between the diameter of the cylinder and the inclination of the knife; whereas in a complex machine, every part concerned in the transmission of motion, such as each axis, wheel and slide, entails its risk of individual error, and may depreciate the accuracy of the result; and to these sources of disturbance, must be added 464 THE PRACTICAL METAL-WORKER’S ASSISTANT. those due to change of temperature, whether arising from the at¬ mosphere or from friction, especially when different metals are concerned. A rod of wood, generally of alder and about two feet long, was put between the centres, and reduced to a cylinder by a rounder or witchet, attached to a slide running on the bar; the slide with the inclined knife was then applied, and the angle of the knife was gradually varied by adjusting screws, until several screws made in succession, were found to agree with some fixed measure. The experiment was then repeated with the same angle, upon cylinders of the same diameter, of tin, brass, and other comparatively soft metals, and hundreds, or it might almost be said, thousands of screws were thus made. From amongst these screws were selected those which, on trial in the lathe, were found to be most nearly true in their angle, or to have a quiescent gliding motion; and which would also best endure a strict examination as to their pitch or intervals, both with the rule and compasses, and also when two were placed side by side, and their respective threads were compared, as the divisions on two equal scales. The most favorable screw having been selected, it was employed as a guide-screw, in a simple apparatus which consisted of two triangular bars fixed level, parallel, and about one foot asunder, in appropriate standards with two apertures; the one bar carried the mandrel and popit-heads as in the ordinary bar lathe. The slide rest embraced both bars, and was traversed thereupon by the guide-screw placed about midway between the bars; the guide screw and mandrel were generally connected by three wheels, or else by two or four, when the guide and copy were required to have the reverse direction. The mandrel was not usually driven by a pulley and cord; but on the extremity of the mandrel was fixed a light wheel, with one arm serving as a winch handle for rapid motion in running back ; and six or eight radial arms (after the manner of the steering wheels of large vessels), by which the mandrel and the screw were slowly handed round during the cut. In a subsequent and stronger machine the bar carrying the man¬ drel stood lower than the other, to admit of larger change wheels upon it, and the same driving gear was retained. And in another structure of the screw-cutting lathe, the triangular bar was placed for the lathe heads in the centre, whilst a large and wide slide- plate, moving between chamfer bars attached to the framing, car¬ ried the sliding rest for the tool; in this last machine, the mandrel was driven by steam-power, and the retrograde motion had about double the velocity of that used in cutting the screw. The relations between the guide-screw and the copy were varied in all possible ways: the guide was changed end for end, or dif¬ ferent parts of it were successively used; sometimes, also, two guide-screws were yoked together with three equal wheels, their Duts being connected by a bar jointed to each, and the centre of SCREW-CUTTING TOOLS. 465 this link (whose motion thus became the mean of that of the guides) was made to traverse the tool. Steel screws were also cut, and converted into original taps, from which dies were made, to be themselves used in correcting the minor errors, and render the screws in all respects as equable as possible. In fact, every scheme that he could devise, which appeared likely to benefit the result, was carefully tried, in order to perfect to the utmost, the helical character and equality of subdivision of the screw. The change of the thousandth part of the total length, was therefore given to the tool as a supplementary motion, which might be added to, or subtracted from, the total traverse of the tool, in the mode explained by the diagram, Fig. 507, in which all details of construction are purposely omitted. The copy C, and the guide- screw G, are supposed to be connected by equal wheels in the usual manner; the guide-screw carries the axis of the bent lever, whose arms are as 10 to 1, and which moves in a horizontal plane; the short arm carries the tool, the long arm is jointed to a saddle which slides upon a triangular bar i i. In point of fact, the tool was mounted upon the upper of two longitudinal and parallel slides, which were collectively traversed by the guide-screw Gr. In the lower slide was fixed the axis or fulcrum of the bent lever, the short arm of which was connected by a link with the upper slide, so that the compensating motion was given to the upper slide relatively to the lower : Fig. 507. The triangular bar i i, when placed exactly parallel with the path of the tool, would produce no movement on the same, and C, and G, would be exactly alike; but if i i were placed out of the paral¬ lelism one inch in the whole length, the tool, during its traverse to the left by the guide-screw G, would be moved to the right by the shifting of the bent lever, one-tenth of the displacement of the bar, or one-tenth of an inch. Therefore, whilst the guide-screw G, from being coarser than required, moved the principal slide the one-thousandth part of the total length in excess; the bent lever and inclined straight bar i i, pulled back the upper or compensating slide, the one-thousandth part, or the quantity in excess; making the absolute traverse of the tool exactly seven feet, or the length required for the new screw C, instead of seven feet and one-sixteenth of an inch, the length of G. To have lengthened the traverse of the tool, the bar i i must have been inclined the reverse way; in other words, the path of the tool 30 466 THE PRACTICAL METAL-WORKER’S ASSISTANT. is in the diagram the difference of the two motions; in the reverse inclination, its path would be the sum of the two motions, and i i being a straight line, the correction.would be evenly distributed at every part of the length. Other experimentalists preferred, however, the method of the chain, or flexible band, for traversing the tool the exact quantity; because the reduction of a diameter of the pulley or drum, afforded a very ready means of adjustment for total length; and all the wheels of the mechanism being individually as perfect as they could be made, a near approach to general perfection was naturally antic¬ ipated on the first trial. This mode, however, is subject to the error introduced by the elasticity or elongation of the chain or band, and which is at the maximum when the greatest length of chain is uncoiled from the barrel. About the year 1820, Mr. Clement put in practice a peculiar mode for originating the guide-screw of his screw-lathe, the steps of which plan will be now described. 1. He procured from Scotland some hand-screw tools cut over a hob with concentric grooves; and to prevent the ridges or points of the screw tools from being cut square across the end, the rest was inclined to compensate for the want of angle in the hob or cutter. 2. A brass screw was struck by hand, or chased with the tool 1. 3. The screw 2, was fixed at the back of a traversing mandrel, and clipped between two pieces of wood or dies to serve as a guide, whilst, 4. A more perfect guide-screw was cut with a fixed tool, and substituted on the mandrel for 3; as Mr. Clement considered the movement derived from the opposite sides of the one screw, became the mean of the two sides, and corrected any irregularities of angle, or of drunkenness. 5. A large and a small master-tap m, Fig. 508, were cut on the traversing mandrel with a fixed tool, the threads were about an inch long and situated in the middle of a shaft eight or ten inches long; the small master-tap was of the same diameter as the finished screw, the large master-tap measured at the bottom of the thread the same as the blank cylinder to be screwed. The master-taps m, were used in cutting up the rectangular dies required in the apparatus shown in Fig. 508, and now to be described. 6 . On the parallel bed of a lathe were fitted two standards or collar-heads h h', intended to receive the pivots of the screw to be cut, on the extremity of which was placed a winch handle, or some¬ times an intermediate socket was interposed between the screw and the winch, to carry the latter to the end of the bed. The bed had also an accurate slide plate s s', running freely upon it, the slide plate had two tails which passed beside the head li', and at the other end. a projection through which was made a transverse rec¬ tangular mortise for the dies, the one end of the mortise is shown by the removal of the front die d, and the back die d' is seen in its SCREW-CUTTING TOOLS. 467 proper situation; one extremity of each, die was cut from the large master tap m, and the other from the small. The clamp or shackle c c', was used to close the two dies upon the screw simultaneously; it is shown out of its true position in order that the dies and mortise may be seen, but when in use the shackle would be shifted to the right, so as to embrace the dies d d'. The plain extremity c' rested against the back die, whilst the screw c bore against the front die, through the intervention of the washer loosely attached to the clamp to save the teeth from injury; the pressure screw c had a graduated head and an index, to denote how much the dies were closed. Fig. 508. 7. A cylinder about two feet long, prepared for the screw, was placed between the heads h h', and the large dies, whose inner edges were of the same diameter as the cylinder, were closed upon it moderately tight, and the screw was turned round with the winch, to trace a thread from end to end; this w as repeated a few times, the dies being slightly closed between each trip. 8 . A screw-tool was next fixed on the slide s s', in a chamfer slide 11', with appropriate adjusting screws, so as to follow the dies and remove a shaving, much the same as in turning. The dies having arrived at one end of the screw, the same screw tool or a second tool was placed on the opposite side of the side-plate so as to cut during the return movement. With the progress of the screw the screw-tool was applied at a variety of distances from the pair of dies, as well as on opposite sides of the screw, so that the metal was cut out by the tool, and the dies were used almost alone to guide the traverse. Of course the dies were closed between each trip, and when the screw was about half cut up the small dies were substituted for the large ones used at the commencement of the process. 9. The screw thus made, which was intended for a slide-rest, was found to be very uniform in its thread, and it was used for some time for the ordinary purposes of turning. When, however, it was required to be used for cutting other screws, it was found objectionable that its rate was nearly nine, whereas it was required to have eight threads per inch. It was then used in cutting a new guide-screw by means of a pair of change wheels of 50 and 56 468 THE PRACTICAL METAL-WORKER’S ASSISTANT. teeth, which upon calculation were found to effect the conversion with sufficient precision. 10. From 9, the screw of 24 inches in length, one of 8 feet in length was obtained. The thread was cut one-third of its depth, with the wheels, successive portions being operated upon and the tool being carefully adjusted to the termination of the part pre¬ viously cut. The general truth of the entire length was given by Fig. 509. a repetition of the tedious mode of correction represented in the figure, with the dies and tool applied upon a bearer rather exceed¬ ing the full length of the screw. Fig. 510. Although the processes 7 and 8 will produce a most uniform screw, Mr. Clement attaches little importance to the use of the dies SCREW-CUTTING TOOLS. 469 and guide-frame alone when several screws are wanted strictly of the same length. Of some few thus made as nearly as possible under equal circumstances two screws were found very nearly to agree, and a third was above a tenth of an inch longer in ten inches. • This difference he thinks to have arisen in marking out the threads, from a little variation in the fric¬ tion of the slide, or a difference in the first penetration of the dies. The friction of the slide, when sufficient to cause any retardation, he considers to produce a constant and accumulative ef¬ fect; first, as it were, reducing the screw of 15 threads per inch, say to the fineness of 15|-, then acting upon that of 15£, re¬ ducing it to 151, and so on; and that to such an extent, as occasionally to place the screw entirely beyond the correctional process. This cannot be the case when the thread is first marked out with the change-wheels instead of the dies. One very important application of the screw is to the graduation of mathe¬ matical scales. The screw is then em¬ ployed to move a platform, which slides very freely and carries the scale to be graduated; and the swing frame, for the knife or diamond point, is attached to some fixed part of the framing of the machine. Supposing the screw to be absolutely perfect, and to have fifty threads per inch, successive movements of fifty revolutions would move the platform and grad¬ uate the scale exactly into true inches ; but on close examination some of the graduations will be found to exceed, and others to fall short of, the true inch. The scales assume, of course, the relative degree of accuracy of the screw employed. No test is more severe; and when these scales are examined by means of two microscopes under a magnifying power of ten or twenty times, the most minute errors become abundantly obvious from the divisions of the scales failing to in¬ tersect the cross wires of the instrument; the result clearly indi¬ cates corresponding irregularities in the coarseness of the screw at the respective parts of its length. An accustomed eye can thus detect, with the microscope, differences not exceeding the one thirty- thousandth part of an inch, the twenty-five-thousandth part being comparatively of easy observation. Figs. 509 and 512 show a large chucking and reaming lathe built at Lowell, Massachusetts. Figs. 510 and 511 show a chucking and reaming lathe manu¬ factured at Lowell. This instrument is geared with a rest for holding drills and reamers moved by a toothed rack, backhead Fig. 511. 470 THE PRACTICAL METAL-WORKER’s ASSISTANT. stock, adjustable sideways, cast-iron cone-pulleys, gun metal bear¬ ings, and cast-steel spindle. Fig. 512. Fig. 513 is an engine lathe manufactured at the Lowell Machine Shop, Lowell, Massachusetts. Its swing is 50 inches over the sills, and 32 over the rest. Fig. 513. The bed of this lathe is cast in one piece, the feed motion is carried by a screw, the tool rest held down by gibs under the slides, and moved on a toothed rack and pinion by hand. Screw Threads Considered in Bespect to their Propor¬ tions, Forms, and General Characters. —The proportions given to screws employed for attaching together the different parts of works are in nearly every case arbitrary, or, in other words, they are determined almost by experience alone rather than by rule, and with little or no aid from calculation, as will be shown. In addition to the ordinary binding screws, which, although arbi¬ trary, assume proportions not far distant from a general average, many screws, either much coarser or finer than usual, are continu- SCREW-CUTTING TOOLS. 471 ally required for specific purposes; as are likewise other screws of some definite number of turns per inch—as 2, 10, 12, 20, etc.—in order to effect some adjustment or movement having an immediate reference to ordinary lineal measure. But all these must be con¬ sidered as- still more distant than common binding screws from any fixed proportions, and not to be amenable to any rules beyond those of general expediency. Neither the pitch, diameter, nor depth of thread, can be adopted as the basis from which to calculate the two other measures, on account of the different modes in which the three influence the effectiveness of the screw; nor can the proportions suitable to the ordinary f- inch binding screw be doubled for the If inch screw, or halved for that of f inch, as every diameter requires its individual scale to be determined in great measure by experiment in order to produce something like a mean proportion between the dissimilar conditions, which will be separately explained in various points of view. The reasons for the uncertainty of measure in the various fixing screws required in the constructive arts are sufficiently manifest; as first, the force or strain to which a screw is exposed, either in the act of fixing or in the office it has afterward to perform, can rarely be told by calculation ; and secondly, a knowledge of the strain the screw itself will safely endure without breaking in two, or without drawing out of the nut, is equally difficult of attainment; nor thirdly, can the deduction for friction be truly made from that force the screw should otherwise possess from its angle or pitch when viewed as a mechanical power, or as a continuous circular wedge. The force required in the fixing of screws takes a very wide range, and is faintly indicative of the strain exerted on each. The watchmaker, in fixing his binding screws, employs with great delicacy a screw-driver the handle of which is smaller than an ordinary drawing pencil; while for screws, say of five inches dia¬ meter, a lever of six or seven feet long must be employed by the engineer, with the united exertions of as many men. But in neither case do we arrive at any available conclusion, as to the pre¬ cise force exerted upon, or by each screw; nor of the greatest strain that each will safely endure. The absolute measures of the strength of any individual screw being therefore nearly or quite unattainable, all that can be done to assist the judgment, is to explain the relative or comparative mea¬ sures of strength in different screws, as determined by the three conditions which occur in every screw; whether it be right or left- handed, of single or of multiplex thread, or of any section what¬ ever ; and which three conditions follow different laws, and con¬ jointly, yet oppositely determine the fitness of the screw for its par¬ ticular purpose, and therefore tend to perplex the choice. The three relative or comparative measures of strength in different screws are: first, the mechanical power of the thread, which is de- 472 THE PRACTICAL METAL-WORKERS ASSISTANT. rived from its pitch; secondly, the cohesive strength of the bolt, which is derived from its transverse section; thirdly, the cohesive strength of the hold, which is derived from the interplacement of the threads of the screw and nut. These conditions will he first considered, principally as regards ordinary binding screws, and screw bolts and nuts, of angular threads, and which indeed constitute by far the largest number of all the screws employed; screws of angular and square threads will be then compared. The comparative sections, Figs. 514 to 517, represent screws of the same diameters, and in all of which the depth of the thread is equal to the width of the groove; Figs. 515 and 517 show the ordi- dinary proportions of f inch angular and square thread screws; 514 and 516 are respectively as fine and as coarse again as 515. Figs. 514 515 516 517. Various measures of the screws which require little further ex¬ planation are subjoined in a tabular form; and the relative degrees of strength possessed by each screw under three different points of view, are added. MEASURES AND RELATIVE STRENGTHS OP THE SCREWS. Fig. 514. Fig. 515. Fig. 516. Fig. 517. External diameters in hundredths of an inch . . . • .75 .75 .75 .75 Internal diameters in hundredths of an inch . . . • .65 .55 .35 .55 Number of threads per inch, or rates of the screws . .20 10. 5. 5. Depths and widths of the threads in hundredths . . .05 .10 .20 .10 Angles of the threads on the external diameters* . . 2°33' 5° 5' 5° 5' Angles of the threads on the internal diameters* . . 1°28' 3°28' 10°47' 6°55' Relative mechanical powers of the threads . . . . 20 10 5 5 Relative cohesive strengths of the holts. 4 3 1 3 Relative cohesive strengths of hold of the screws . . 65 55 35 27£ Relative cohesive strengths of hold of the nuts . . . 75 75 75 37 i Square thread screws, have about twice the pitch of angular threads of similar diameters, and Fig. 517 estimated in the same manner as the angular, will stand by comparison as follows. The * The angles of the threads of screws are calculated trigonometrically, the circumference of the bolt being considered as the base of aright-angled triangle, and the pitch as the height of the same. The author has adopted the following mode, which will be found to require the fewest figures ; namely, to divide the pitch by the circumference, and to seek the product in the table of tangents ; decimal numbers are to be used, and it is sufficiently near to consider the circumference as exactly three times the diameter. SCREW-CUTTING TOOLS. 473 square thread, Fig. 517, will be found to be equal in power to Fig. 516, the pitch being alike in each. In strength of bolt to be equal to Fig. 515, their transverse areas being alike. And in strength of hold, to possess the half of that of Fig. 515, because the square thread will from necessity break through the bottom of the threads, or an interrupted line exactly like the dotted line in Fig. 516, that denotes just half the area or extent of base, of the thread of Fig. 515; which latter covers the entire surface of the contained cylinder, and not the half only. The mechanical power of the thread is derived from its pitch. The power, or the force of compression, is directly as the number of threads per inch, or as the rate; so that neglecting the friction in both cases, Fig. 514 grasps with four times the power of Fig. 516, because its wedge or angle is four times as acute. When, however, the angle is very great, as in the screws of fly- presses, which sometimes exceed the obliquity of 45 degrees, the screw will not retain its grasp at all; neither will a wedge of 45 degrees stick fast in a cleft. Such coarse screws act by impact; they give a violent blow on the die from the momentum of the fly (namely, the loaded lever, or the wheel fixed on the press-screw) being suddenly arrested; they do not wedge fast, but on the con¬ trary, the reaction upwards unwinds and raises the screw for the succeeding stroke of the fly-press. Binding screws which are disproportionately coarse, from lean¬ ing towards this condition, and also from presenting less surface- friction, are liable to become loosened if exposed to a jarring ac¬ tion. But when, on the contrary, the pitch is very fine, or the wedge is very acute, the surface friction against the thread of the screw is such, as occasionally to prevent their separation when the screw-bolt has remained long in the hole or nut, from the adhesion caused by the thickening of the oil, or by a slight formation of rust. The cohesive strength of the bolt is derived from its transverse section. The screw may be thus compared with a cylindrical rod of the some diameter as the bottom of the thread, and employed in sus¬ taining a load; that is, neglecting torsion, which if in excess may twist the screw in two. The relative strengths are represented by the squares of the smaller diameters: in the screws of 20, 10, and 5 angular threads, the smaller diameters are 65, 55, and 35; tha squares of these numbers are 4225, 3025, and 1225, which may be expressed in round numbers as 4, 3, 1 ; and, therefore, the coarsest screw, Fig. 516, has transversely only one-fourth the area, and conse- For the external angle of Fig. 516 say .20+2.25=.0888, and this quotient by Hutton’s Tables gives 5 deg. 5 min. For the internal angle of Fig. 514 say .05+1.95=0.2564, and by Hutton’s Tables, 1 deg. 28 min. In this method the pitch is considered as the tangent to the angle, and the division effects the change of the two sides of the given right-angled triangle, for two others, the larger of which is 1 or unity, for the convenience of using the tables. 474 THE PRACTICAL METAL-WORKER’S ASSISTANT. quently one-fourth the strength of the finest, represented in the three diagrams. The cohesive strength of the hold is derived from the helical ridge of the external screw, being situated within the helical groove of the inter¬ nal screw. The two helices become locked together with a degree of firmness, approaching to that by means of which the dilferent particles of solid bodies are united in a mass; as one or both of the ridges must be in a great measure torn off in the removal of the screw, unless it be unwound or twisted out. A slisrht difference in the diameter or the section of a screw and O nut, is less objectionable than any variation in the coarseness or pitch; as the latter difference, even when very minute, will pre¬ vent the screw from entering the hole, unless the screw is made considerably smaller than it ought to be, and even then it will bear very imperfectly, or only on a few places of the nut. To attempt to alter a screwed hole by the use of a tap of a dif¬ ferent pitch, is equally fatal, as will be seen by the annexed dia¬ gram, Fig. 518. For instance, the upper line a, contains exactly 4 threads per inch, and the middle line or b, has 4^- threads; they only agree at distant intervals. The lowest line c, shows that which would result from forcing a tap of 4 threads such as a into a hole which had been previously tapped with the 4£ thread screw b, the threads would be said to cross, and would nearly destroy each other; the same result would of course occur from employing 4 or 5 thread dies on a screw of 4J threads per inch. Therefore, unless the screw tackle exactly agree in pitch with the previous thread, it is needful to remove every vestige of the former thread from the screw or hole; otherwise the result drawn at c, must ensue in a degree proportionate to the difference of the threads, and a large portion of the bearing surface, and conse¬ quently, of the strength and durability of the contact, would each be lost. Some idea may thence be formed of the real and irreme¬ diable drawback frequently experienced from the dissimilarity of screwing apparatus; nearly to agree will not suffice, as the pitch should be identical. The nut of a f-inch screw bolt is usually £ inch thick, as it is SCREW-CUTTING- TOOLS. 475 considered that when the threads are in good contact, and collec¬ tively equal to the diameter of the bolt, that the mutual hold of the threads exceeds the strength either of the bolt or nut; and therefore that the bolt is more likely to break in two, or the nut to burst open, rather than allow the bolt to draw out of the hole, from the thread stripping off. When screws fit into holes tapped directly into the castings or other parts of mechanism, it is usual to allow still more threads to be in contact, even to the extent of two or more times the diame¬ ter of the screw, so as to leave the preponderance of strength greatly in favor of the hold; that the screw, which is the part more easily renewed, may be nearly certain to break in two, rather than damage the castings by tearing out the thread from the tapped hole. Should the internal and external screws be made in the same material, that is both of wood, brass or iron, the nut or internal screw is somewhat the stronger of the two. For example, in the screw Fig. 515, the base of the thread is a continuous angular ridge, which occupies the whole of the cylindrical surface repre¬ sented by the dotted line. Therefore the force required to strip off the thread from the bolt, is nearly that required to punch a cylindrical hole of the same diameter and length as the bottom of the thread; for in either case the whole of the cylindrical surface has to be stripped or thrust off laterally, in a manner resembling the slow, quiet action of the punching or shearing engine. But the base of the thread in the nut, is equal to the cylindrical surface measured at the top of the bolt, and consequently, the mate • rials being the same, and the length the same, considering the strength of the nut for Fig. 515 to be 75, the strength of the bolt would be only 55, or they would be respectively as the diame¬ ters of the top and bottom of the thread; although when the bolt protrudes through the nut, the thread of the bolt derives a slight additional strength, from the threads situated beyond the nut, and which serve as an abutment. It is however probable that the angular thread will not strip off at the base of the threads, either in the screw or nut, but will break through a line somewhere between the top and bottom: but these results will occur alike in all, and will not therefore materially alter the relation of strength above assumed. Comparing Figs. 514, 515, and 516, upon the supposition that the bolts and nuts exactly fit or correspond, the strengths of the three nuts are alike, or as 75, and those of the bolts are as 65, 55, and 35, and therefore the advantage of hold lies with the bolt of finest thread; as the finer the thread, the more nearly do the bolt and nut approach to equality of diameter and strength. Supposing, however, for the purpose of explanation, that instead of the screws and nuts being carefully fitted, the screws are each one-tenth of an inch smaller than the diameters of the respective taps employed in cutting the three nuts; Fig. 514 would draw 476 THE PRACTICAL METAL-WORKERS ASSISTANT. entirely out without holding at all; the penetration and hold of Fig. 515 would be reduced to half its proper quantity; and that of Fig. 516 to three-fourths; and the last two screws would strip at a line more or less elevated above the base of the thread, and therefore the more easily than if the diameters exactly agreed. The supposed error, although monstrous and excessive, shows that the finer the thread, the greater also should be the accuracy of contact of such screws; and it also shows the impolicy of employ¬ ing fine threads in those situations where they will be subjected to frequent screwing and unscrewing, and also to much strain. As although when they fit equally well, fine threads are somewhat more powerful than coarse, in hold as well as in mechanical power; the fine are also more subject to wear, and they receive from such wear, a greater and more rapid depreciation of strength, than threads of the ordinary degrees of coarseness. In a screw of the same diameter and pitch, the ultimate strength is diminished in a twofold manner by the increase of the depth of the thread; first it diminishes the traverse area of the bolt, which is therefore more disposed to break in two; and secondly, it diminishes the individual strength of each thread, which becomes a more lofty triangle erected on the same base, and is therefore more exposed to fracture or to be stripped off. But the durability of machinery is in nearly every case increased by the enlargement of the hearing surfaces, and therefore as the thread of increased depth presents more surface-bearing, the deep screw has constantly greater durability against the friction or wear, arising from the act of screwing and unscrewing. The durability of the screw becomes in truth a fourth condition, to be borne in mind collectively with those before named. It frequently happens that the diameters of screwed works are so considerable, that they can neither break nor burst after the manner of bolts and nuts; and if such large works yield to the pressures applied, the threads must be the part sacrificed. If the materials are crystalline, the thread crumbles away, but in those which are malleable and ductile, the thread, instead of stripping off as a wire, sometimes bends until the resisting side presents a perpendicular face, then overhangs, and ultimately curls over: this disposition is also shown in the abrasive wear of the screw before it yields. Comparing the square with the angular thread in regard to fric¬ tion, the square has less friction, because the angular edges of the screw and nut, mutually thrust themselves into the opposite angular grooves in the manner of the wedge. The square thread has also the advantage of presenting a more direct thrust than the angular, because in each case the resistance is at right angles to the side of the thread, and therefore in the square thread the resistance is very nearly in the line of its axis, whereas in the angular it is much more oblique. From these reasons, the square thread is commonly selected for SCREW-CUTTING TOOLS. 477 presses, and for regulating screws, especially those in which rapidity of pitch, combined with strength, is essential; but as regards the ordinary attachments in machinery, the grasp of the angular thread is more powerful, from its pitch being generally about as fine again, and, as before explained, angular screws and nuts are somewhat more easily fitted together. The force exerted in bursting open a nut, depends on the angle formed by the sides of the thread, when the latter is considered as part of a cone, or as a wedge employed in splitting timber. For instance, in the square thread screw, the thread forms a line at right angles to the axis, and which is dotted in the figure 519 ; it is not therefore a cone, but simply compresses the nut, or attempts to force the metal before it. In the deep thread, Fig. 520, the wedge is obtuse, and exerts much less bursting effort than the acute cone represented in the shallow thread screw, Fig. 521; therefore, the shallower the angular thread, the more acute the cone, and the greater the strain it throws upon the nut. The transverse measure of nuts, whether they are square or hexagonal, is usually about twice the diameter of the bolt, as represented in the figures, and this in general suffices to withstand the bursting effort of the bolt. In the table of dimensions of nuts, in “ Byrne’s Engineer’s Pocket Companion,” the traverse measures decrease in the larger nuts; the breadth of a nut for a J inch bolt is stated as 1 inch, that for a 2| inch bolt as four inches. Those nuts, however, which are not used for grasping, but for the regulating screws of slides and general machinery, are made much thicker, so as to occupy as much of the length of the screw as two, three, or more times its diameter. This greatly increases their surface-contact and durability. Should it be required to be able to compensate the nut, or to re¬ adapt it to the lessened size of the screw when both have been worn, the nut is made in two parts and compressed by screws, or it is made elastic so as to press upon the screw. The nuts for angular threads are divided diametrically and reunited by two or more screws, as in Fig. 522—in fact, like the semi-circular bearings of ordinary shafts; as then by filing a little of the metal away from 478 THE PRACTICAL METAL-WORKER’S ASSISTANT. between the two halves of the nut, they may be closed upon the. angular ridges of the thread. The nuts of square threads by a similar treatment would, on being closed, fit accurately upon the outer or cylindrical surface of the square thread screw; but the lateral contact would not be re¬ stored ; these nuts are, therefore, divided transversely, as shown in Fig. 523, or they are made as two detached nuts placed in contact. When, therefore, a small quantity is removed from between them with the file, or that they are separated by one or more thicknesses of paper, the one-half of the nut bears on the right hand side of the square worm, the other on the left. Figs. 522 523 524 525 Either of these methods removes the “ end play,” or the “ loss of f the carbonic acid disengaged, which parts with an atom of oxy¬ gen (CO 2 -f C = 2 CO) combining with the carbon of the cast- iron, and which becomes carbonic oxide. In the third case, we may surmise that the carbon was burned out by the air o,f the fire-place, penetrating through the interstices of the cast- iron plates forming the boxes in which the metal and the mix¬ ture were packed. The air was prevented from acting vio¬ lently by the mass of bone-dust and powdered charcoal with 654 TIIE PRACTICAL METAL WORKER’S ASSISTANT. which the articles were surrounded. "We do not believe that the temperature was sufficiently high to decompose the bone- dust, even in presence of the charcoal. The furnace employed was of brick, and square, and divided by vertical partitions of cast-iron plates, between two of which were packed the castings and the mixture, and around which were flues for the circula¬ tion of the gases of the fire-place. However imperfect these dispositions may be. when com¬ pared with the present ones, Reaumur ascertained that oxides of iron and cast-iron, heated together in closed vessels, pro¬ duced malleable iron; that for malleable castings, white is pre¬ ferable to gray metal; that the castings, previous to annealing, should be deprived of the adhering sand, which becoming fluxed, prevented the reaction; that too protracted and too intense a heat may harden the castings again; and that pro¬ perly annealed articles may be bent, forged, welded, case-hard¬ ened, and present all the properties and even appearance of wrought iron. After having explained the principles upon which the in¬ dustry of malleable iron casting is founded, and given a histori¬ cal notice of the first trials made, we cannot do better than to describe the actual processes, such as are applied at the Hard¬ ware and Malleable Iron Works of Messrs. Chas. W. Carr, Jos. S. Crawley, and Thos. Devlin, successors to E. Hall Ogden, and whose store is at 307 Arch Street, Philadelphia. In this large establishment, where everything is conducted with the best order and understanding, anything in the line of ordinary and malleable castings for building and cabinet, car¬ riage and saddlery hardware, &c., is made complete, from the pattern to the casting, annealing, coppering, adjusting and japanning of the articles. Indeed, the mechanical appliances for finishing and adjusting different parts, comprise one of .the most interesting departments of the works, with their plan¬ ing machines, lathes, punches, screw-cutting tools, grinding and polishing stones, and drills which allow of the drilling of several holes in the same piece at the same time, and at various angles. The pig iron used preferably for malleable castings is a white charcoal pig, and is melted in cupolas, or in a rever¬ beratory furnace (Fig. 606). This latter furnace, of which A is the fire-place, B the hearth, G the tap-hole, D the flue to¬ wards the stack, and E the door through which the impurities are removed from the top of the molten metal, consumes more fuel, and produces more wa^e than the cupola. On the other hand, the metal is purer, because it is not melted in direct con¬ tact with the fuel, and does not absorb its impurities, sulphur especially. There is also the advantage that, should the metal contain too much carbon, part of it may be removed by the oxidizing action of the flame. MALLEABLE IRON CASTINGS. 655 Most of the castings are made in green sand, from metallic patterns, which insure a constancy of shape and of smooth surfaces. Fig. 606. The castings, which are as brittle as glass, are then put into 08 to 1S66 ; exhibiting the Origin and Growth of the Prin¬ cipal Mechanic Arts and Manufactures, from the Earliest Colonial Period to the Present Time ; By J. Leander Bishop, M. D., Ed¬ ward Young, and Edwin T. Freedley. Three vols. 8vo., B $10 00 OX—A PRACTICAL TREATISE ON HEAT AS APPLIED TO THE USEFUL ARTS: For the use of Engineers, Architects, etc. By Thomas Box, au¬ thor of “Practical Hydraulics.” Illustrated by 14 plates, con¬ taining 114 figures. 12mo. . . . . . . $4 25 ABINET MAKER’S ALBUM OF FURNITURE : Comprising a Collection of Designs for the Newest and Most Elegant Styles of Furniture. 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By Forsttu. 4to., cloth.$5 00 *** This volume, for the beauty and variety of its designs, has never been surpassed by any publication of the kind, and should be in the hands of every marble-worker who does fine monumental work. miRBAIRN.—THE PRINCIPLES OF MECHANISM AND MA- £ CHINERY OF TRANSMISSION : Comprising the Principles of Mechanism, Wheels, and Pulleys, Strength and Proportions of Shafts, Couplings of Shafts, and Engaging and Disengaging Gear. By William Fairbairn, Esq., C. E., LL. D., F. R. S., F. G. S., Corresponding Member of the National Institute of France, and of the Royal Academy of Turin; Chevalier of the Legion of Honor, etc. etc. Beau¬ tifully illustrated by over 150 wood-cuts. In one volume 12mo. $2 50 'AIRBAIRN.—PRIME-MOVERS: Comprising the Accumulation of Water-power; the Construc¬ tion of Water-wheels and Turbines; the Properties of Steam; the Varieties of Steam-engines and Boilers and Wind-mills. By William Fairbairn, C. E , LL. D., F. R. S., F. G. S. Au¬ thor of “Principles of Mechanism and the Machinery of,Trans¬ mission.” With Numerous Illustrations. In one volume. (In press.) ILBART.—A PRACTICAL TREATISE ON BANKING: By James William Gilbart. To which is added: Tiie Na¬ tional Bank Act as now in force. 8vo. . . $4 50 IESNER.—A PRACTICAL TREATISE ON COAL, PETROLEUM, f AND OTHER DISTILLED OILS. By Abraham Gesner, M. D., F. G. S. Second edition, revised and enlarged. By George Weltden Gesner, Consulting Chemist and Engineer. Illustrated. 8vo. . . $3 50 HENRY CAREY BAIRD’S CATALOGUE. 13 QOTHIC ALBUM FOR CABINET MAKERS: Comprising a Collection of Designs for Gothic Furniture. Il¬ lustrated by twenty-three large and beautifully engraved plates. Oblong . ..$3 00 /TRANT.—BEET-ROOT SUGAR AND CULTIVATION OF THE BEET: By E. B. Grant. 12mo. . ... . . $1 25 GREGORY—MATHEMATICS FOR PRACTICAL MEN : Adapted to the Pursuits of Surveyors, Architects, Mechanics, and Civil Engineers, cloth By Olinthus Gregory. 8vo., plates, . $3 00 HRISWOLD.—RAILROAD ENGINEER’S POCKET COMPANION. Comprising Rules for Calculating Deflection Distances and Angles, Tangential Distances and Angles, and all Necessary Tables for Engineers; also the art of Levelling from Prelimi¬ nary Survey to the Construction of Railroads, intended Ex¬ pressly for the Young Engineer, together with Numerous Valu¬ able Rules and Examples. By W. Griswold. 12mo., tucks. $1 75 HUETTIER.—METALLIC ALLOYS: ^ Being a Practical Guide to their Chemical and Physical Pro¬ perties, their Preparation, Composition, and Uses. Translated from the French of A. Guettier, Engineer and Director of Founderies, author of “La Fouderie en France,” etc. etc. By A. A. Fesquet, Chemist and Engineer. In one volume, 12mo. $3 00 H ATS AND FELTING: A Practical Treatise on their Manufacture. By a Practical Hatter. Illustrated by Drawings of Machinery, &c., 8vo. $1 25 AY.—THE INTERIOR DECORATOR : ’ The Laws of Harmonious Coloring adapted to Interior Decora¬ tions : with a Practical Treatise on House-Painting. By D. R. Hay, House-Painter and Decorator. Illustrated by a Dia¬ gram of the Primary, Secondary, and Tertiary Colors. 12mo. $2 25 rrUGHES.—AMERICAN MILLER AND MILLWRIGHT’S AS- S 1ST ANT: By Wm. Carter Hughes. A new edition. In one volume, 12mo. ... - .... ^1 50 14 HENRY CAREY BAIRD’S CATALOGUE. w NT.—THE PRACTICE OF PHOTOGRAPHY. By Robert Hunt, Vice-President of the Photographic Society, London. With numerous illustrations. 12mo., cloth . 75 JJURST.—A HAND-BOOK FOR ARCHITECTURAL SURVEYORS: Comprising Formulae useful in Designing Builders’ work, Table of Weights, of the materials used in Building, Memoranda connected with Builders’ work, Mensuration, the Practice of Builders’ Measurement, Contracts of Labor, Valuation of Pro¬ perty, Summary of the Practice in Dilapidation, etc. etc. By J. F. IIcrst, C. E. 2d edition, pocket-book form, full bound $2 50 JERVIS. —RAILWAY PROPERTY: A Treatise on the Construction and Management of Railways; designed to afford useful knowledge, in the popular style, to the holders of this class of property; as well as Railway Mana-. gers, Officers, and Agents. By John B. Jervis, late Chief Engineer of the Hudson River Railroad, Croton Aqueduct, &c. One vol. 12mo., cloth .... . $2 00 JOHNSON.—A REPORT TO THE NAVY DEPARTMENT OF THE U UNITED STATES ON AMERICAN COALS: Applicable to Steam Navigation and to other purposes. By Walter R. Johnson. With numerous illustrations. COT pp. 8vo., . . . . . $10 00 OHNSTON—INSTRUCTIONS FOR THE ANALYSIS OF SOILS, LIMESTONES, AND MANURES By J. W. F. Johnston. 12mo. .... 35 K 1 ENE.—A HAND-BOOK OF PRACTICAL GAUGING, For the Use of Beginners, to which is added a Chapter on Dis¬ tillation, describing the process in operation at the Custom nouse for ascertaining the strength of wines. By James B. Keene, of H. M. Customs. 8vo. . . . $1 25 HENRY CAREY BATRD’S CATALOGUE. 15 J^ENTISH.—A TREATISE ON A BOX OF INSTRUMENTS, And the Slide Rule ; with the Theory of Trigonometry and Lo¬ garithms, including Practical Geometry, Surveying, Measur¬ ing of Timber, Cask and Malt Gauging, Heights, and Distances. By Thomas Kentish. In one volume. 12mo. . . $1 25 OBELL.—ERNI.—MINERALOGY SIMPLIFIED: A short method of Determining and Classifying Minerals, by means of simple Chemical Experiments in the Wet Way. Translated from the last German Edition of F. Yon Kobell, with an Introduction to Blowpipe Analysis and other addi¬ tions. By Henri Erni, M. D., Chief Chemist, Department of Agriculture, author of “Coal Oil and Petroleum.” In one volume. 12mo. ... . $2 60 ANDRIN.—A TREATISE ON STEEL: Comprising its Theory, Metallurgy, Properties, Practical Work¬ ing, and Use. By M. II. C. Landrin, Jr., Civil Engineer. Translated from the French, with Notes, by A. A. Fesqtjet, Chemist and Engineer. With an Appendix on the Bessemer and the Martin Processes for Manufacturing Steel, from the Report of Abram S. Hewitt, United States Commissioner to the Universal Exposition, Paris, 1867. 12mo. . . $3 00 TARKIN.—THE PRACTICAL BRASS AND IRON FOUNDER’S GUIDE. A Concise Treatise.on Brass Founding, Moulding, the Metals and their Alloys, etc.; to which are added Recent Improve¬ ments in the Manufacture of Iron, Steel by the Bessemer Pro¬ cess, etc. etc. By James Larkin, late Conductor of the Brass Foundry Department in Reany, Neafie & Co.’s Penn Works, Philadelphia. Fifth edition, revised, with extensive Addi¬ tions. In one volume. 12mo. . . . . . $2 25 lb IIENRY CAREY BAIRD'S CATALOGUE. T EAVITT.—PACTS ABOUT PEAT AS AN ARTICLE OF FUEL: ■*"* With Remarks upon its Origin and Composition, the Localities in which it is found, the Methods of Preparation and Manu facture, and the various Uses to which it is applicable; toge¬ ther with many other matters of Practical and Scientific Inte* rest. To which is added a chapter on the Utilization of Coal Dust with Peat for the Production of an Excellent Fuel at Moderate Cost, especially adapted for Steam Service. By II. T. Lkavitt. Third edition. 12mo. . . . $1 75 TEROUX—A PRACTICAL TREATISE ON THE MANUFAC- - Lj TURE OF WORSTEDS AND CARDED YARNS: Translated from the French of Charles Leroux, Mechanical Engineer, and Superintendent of a Spinning Mill. By Dr II. Paine, and A. A.Fesquet. Illustrated by 12 large plates. In one volume 8vo. . . . . . . . . $5 00 T ESLIE (MISS).—COMPLETE COOKERY: Directions for Cookery in its Various Branches. By Miss Leslie. 60th edition. Thoroughly revised, with the addi¬ tion of New Receipts. In 1 vol. 12mo., cloth . . $1 60 T ESLIE (MISS). LADIES’ HOUSE BOOK : a Manual of Domestic Economy. 20th revised edition. 12mo., cloth . . . . . . . . . $1 25 T ESLIE (MISS).—TWO HUNDRED RECEIPTS IN FRENCH ^ COOKERY. 12mo. 50 j^IEBER.—ASS AYER’S GUIDE: Or, Practical Directions to Assayers, Miners, and Smelters, for the Tests and Assays, by Heat and by Wet Processes, for the Ores of all the principal Metals, of Gold and Silver Coins and Alloys, and of Coal, etc. By Oscar M. Lieber. 12mo., cloth $1 25 T 0VE.—THE ART OF DYEING, CLEANING, SCOURING, AND FINISHING: On the most approved English and French methods; being Practical Instructions in Dyeing Silks, Woollens, and Cottons, Feathers, Chips, Straw, etc.; Scouring and Cleaning Bed and Window Curtains, Carpets, Rugs, etc.; French and English Cleaning, etc. By Thomas Love. Second American Edition, to which are added General Instructions for the Use of Aniline Colors. 8vo.5 00 HENRY CAREY BAIRD’S CATALOGUE. 17 TyrAIN AND BROWN—QUESTIONS ON SUBJECTS CONNECTED 1V1 WITH THE MARINE STEAM-ENGINE: M And Examination Papers; with Hints for their Solution. By Thomas J. Main, Professor of Mathematics, Royal Naval College, and Thomas Brown, Chief Engineer, R. N. 12mo., cloth $1 50 AIN AND BROWN.—THE INDICATOR AND DYNAMOMETER: With their Practical Applications to the Steam-Engine. By Thomas J. Main, M. A. F. R., Ass’t Prof. Royal Naval College, Portsmouth, and Thomas Brown, Assoc. Inst. C. E., Chief En¬ gineer, R. N., attached to the R. N. College. Illustrated. From the Fourth London Edition. 8vo. ... . $1 50 M AIN AND BROWN —THE MARINE STEAM-ENGINE. By Thomas J. Main, F. R. Ass’t S'. Mathematical Professor at Royal Naval College, and Thomas Brown, Assoc. Inst. C. E. Chief Engineer, R. N. Attached to the R,oyal Naval College. Authors of “Questions Connected with the Marine Steam-En- With numerous . $5 00 gine,” and the “ Indicator and Dynamometer.’ Illustrations. In one volume 8vo. . TUTARTIN.—SCREW-CUTTING TABLES, FOR THE USE OF ME- CHANICAL ENGINEERS: Showing the Proper Arrangement of Wheels for Cutting the Threads of Screws of any required Pitch; with a Table for Making the Universal Gas-Pipe Thread and Taps. By W. A. Martin, Engineer. 8vo. ....... 50 M ILES—A PLAIN TREATISE ON HORSE-SHOEING. With Illustrations, By William Miles, author of “ The Horse’s Foot” lyrOLESWORTH.—POCKET-BOOK OF USEFUL FORMULA! AND 1Y1 MEMORANDA FOR CIVIL AND MECHANICAL EN3INEERS. By Guilford L. Molesworth, Member of the Institution of Civil Engineers, Chief Resident Engineer of the Ceylon Railway. Second American from the Tenth London Edition. In one volume, full bound in pocket-book form .• . . $2 00 M OORE.—THE INVENTOR’S GUIDE: Patent Office and Patent Laws: or, a Guide to Inventors, and a Book of Reference for Judges, Lawyers, Magistrates, and others. By J G. Moore. 12mo., cloth.$1 25 APIER.—A MANUAL OF ELECTRO-METALLURGY: Including the Application of the Art to Manufacturing Processes. By .Tames Napier. Fourth American, from the Fourth London edition, revised and enlarged. Illustrated by engravings. In one volume, 8vo. ........ $2 00 18 HENRY CAREY BAIRD'S CATALOGUE. NTAPIER.—A SYSTEM OF CHEMISTRY APPLIED TO DYEING: Br James Napier, E. C. S. A New and Thoroughly Revised Edition, completely brought up to the present state of the Science, including the Chemistry of Coal Tar Colors. By A. A. Fesquet, -Chemist and Engineer. With an Appendix on Dyeing and Calico Printing, as shown at the Paris Universal Exposition of 1867, from the Reports of the International Jury, etc. Illus¬ trated. In one volume Svo., 400 pages . . . . $5 00 fyTEWBERY.— GLEANINGS FROM ORNAMENTAL ART OF EVERY STYLE; Drawn from Examples in the British, South Kensington, Indian, Crystal Palace, and other Museums, the Exhibitions of 1851 and 1862, and the best English and Foreign works. In a series of one hundred exquisitely drawn Plates, containing many hundred ex¬ amples. By Robert Newbeby. 4to.$15 00 |pCH0LS0N.—A MANUAL OF THE ART OF BOOK-BINDING: Containing full instructions in the different Branches of Forward¬ ing, Gilding, and Finishing. Also, the Art of Marbling Book- edges and Paper. By James B. Nicholson. Illustrated. 12mo. cloth .... .$2 25 "VTORRIS.—A HAND-BOOK FOR LOCOMOTIVE ENGINEERS AND 1)1 MACHINISTS: Comprising the Proportions and Calculations for Constructing Locomotives; Manner of Setting Valves; Tables of Squares, Cubes, Areas, etc. etc. By Septimus NorRis, Civil and Me¬ chanical Engineer. New edition. Illustrated, 12mo., cloth $2 00 YSTROM. — ON TECHNOLOGICAL EDUCATION AND THE CONSTRUCTION OF SHIPS AND SCREW PROPELLERS: For Naval and Marine Engineers. By John W. Nystrom, late Acting Chief Engineer U. S. N. Second edition, revised with additional matter. Illustrated by seven engravings. 12mo. O' $2 50 NEILL.—A DICTIONARY OF DYEING AND CALICO PRINT¬ ING: Containing a brief account of all the Substances and Processes in use in the Art of Dyeing and Printing Textile Fabrics : with Prac¬ tical Receipts and Scientific Information. By Charles O’Neill, Analytical Chemist; Fellow of the Chemical Society of London ; Member of the Literary and Philosophical Society of Manchester ; Author of “ Chemistry of Calico Printing and Dyeing.” To which is added An Essay on Coal Tar Colors and their Application to IIENRY CAREY BAIRD’S CATALOGUE. 19 Dyeing and Calico Printing. By A. A. Fesquet, Chemist and Engineer. With an Appendix on Dyeing and Calico Printing, as shown at the Exposition of 1867, from the Reports of the Interna, tional Jury, etc. In one volume 8vo., 491 pages . . $6 00 QSBORN.—THE METALLURGY OF IRON AND STEEL: Theoretical and Practical : In all its Branches ; With Special Re¬ ference to American Materials and Processes. By H. S. Osborn, LL. D., Professor of Mining and Metallurgy in Lafayette College, Easton, Pa. Illustrated by 230 Engravings on Wood, and 6 Folding Plates. 8vo., 972 pages.$10 00 QSBORN.—AMERICAN MINES AND MINING : Theoretically and Practically Considered. By Prof. II. S. Os¬ born, Illustrated by numerous engravings. 8vo. (In preparation.) pAINTER, GILDER, AND VARNISHER’S COMPANION: Containing Rules and Regulations in everything relating to the Arts of Painting, Gilding, Varnishing, and Glass Staining, with numerous useful and valuable Receipts; Tests for the Detection of Adulterations in Oils and Colors, and a statement of the Dis¬ eases and Accidents to which Painters, Gilders, and Varnishers are particularly liable, with the simplest methods of Prevention and Remedy. With Directions for Graining, Marbling, Sign Writ¬ ing, and Gilding on Glass. To which are added Complete Instruc¬ tions eor Coach Painting and Varnishing. 12mo., cloth, $1 50 P P : iALLETT.—THE MILLER’S, MILLWRIGHT’S, AND ENGI¬ NEER’S GUIDE. By Henry Pallett. Illustrated. In one vol. 12mo. . $3 00 ERKINS.—GAS AND VENTILATION. Practical Treatise on Gas and Ventilation. With Special Relation to Illuminating, Heating, and Cooking by Gas. Including Scien¬ tific Helps to Engineer-students and others. With illustrated Diagrams. By E. E. Perkins. 12mo., cloth . . . $1 25 ERKINS AND STOWE.—A NEW GUIDE TO THE SHEET-IRON AND BOILER PLATE ROLLER: Containing a Series of Tables showing the Weight of Slabs and Piles to Produce Boiler Plates, and of the Weight of Piles and the Sizes of Bars to Produce Sheet-iron ; the Thickness of the Bar Gauge in Decimals; the Weight per foot, and the Thickness on the Bar or Wire Gauge of the fractional parts of an inch; the Weight per sheet, and the Thickness on the Wire Gauge of Sheet- iron of various dimensions to weigh 112 lbs. per bundle; and the conversion of Short Weight into Long Weight, and Long Weight into Short. Estimated and collected by G, n. Perkins and J . G- Stowe.. $2 59 20 HENRY CAREY BAIRD’S CATALOGUE. (HILLIPS AND DARLINGTON.—RECORDS OF MINING AND METALLURGY: Or, Facts and Memoranda for the use of the Mine Agent and Smelter. By J. Arthur Phillips, Mining Engineer, Graduate of the Imperial School of Mines, France, etc., and John Darlington. Illustrated by numerous engravings. In one vol. 12mo. . $2 00 iRADAL, MALEPEYRE, AND DUSSAUCE. — A COMPLETE TREATISE ON PERFUMERY: Containing notices of the Raw Material used in the Ait, and the Best Formulae. According to the most approved Methods followed in France, England, and the United States. By M. P. Piiadal, Perfumer-Chemist, and M. F. Malepeyre. Translated from the French, with extensive additions, by Prof. II. Dussauce. 8yo. $10 iROTEAUX.—PRACTICAL GUIDE FOR THE MANUFACTURE OF PAPER AND BOARDS. By A. Proteaux, Civil Engineer, and Graduate of the School of Arts and Manufactures, Director of Thiers’s Paper Mill, ’Puy-de- Dume. With additions, by L. S. Le Norhand. Translated from the French, with Notes, by Horatio Paine, A. B., M. D. To which is added a Chapter on the Manufacture of Paper from Wood in the United States, by Henry T. Brown, of the “American Artisan.” Illustrated by six plates, containing Drawings of Raw Materials, Machinery, Plans of Paper-Mills, etc. etc. 8vo. $5 00 •DEGNAULT.—ELEMENTS OF CHEMISTRY. By M. Y. Regnault. Translated from the French by T. For¬ rest Benton, M. B., and edited, with notes, by James C. Booth, Melter and Refiner U. S. Mint, and Wu. L. Faber, Metallurgist and Mining Engineer. Illustrated by nearly 700 wood engravings. Comprising nearly 1500 pages. In two vols. 8vo., cloth $10 00 "DEID.—A PRACTICAL TREATISE ON THE MANUFACTURE OF PORTLAND CEMENT: By Henry Reid, C. E. To which is added a Translation of M. A. Lipowitz’s Work, describing anew method adopted in Germany of Manufacturing that Cement. By W. F. Reid. Illustrated by plates and wood engravings. 8vo. . . . . . $7 00 T1 IFF AULT, VERGNAUD, AND TOUSSAINT.—A PRACTICAL 11 TREATISE ON THE MANUFACTURE OF COLORS FOR PAINTING: Containing the best Formulas and the Processes the Newest and in most General Use. By MM. Riffault, Yergnaud, andTous- saint. Revised and Edited by M. F. Malepeyre and Dr. Emil Winckler. Illustrated by Engravings. In one vol. Svo. {In preparation .) HENRY CAREY BAIRD’S CATALOGUE. 21 T> IFF AULT, VERGNAUD, AND TOUSSAINT.—A PRACTICAL LXl TREATISE ON THE MANUFACTURE OF VARNISHES: By MM. Riffault, Vergnaud, and Toussaint. Revised and Edited by M. F. Malepetee and Dr. Emil Winckler. Illus¬ trated. In one vol. 8vo. (In preparation.) IHUNK.—A PRACTICAL TREATISE ON RAILWAY CURVES * AND LOCATION, FOR YOUNG ENGINEERS. By Wm. F. Shunk, Civil Engineer. 12mo., tucks . . $2 00 MEATON.—BUILDER’S POCKET COMPANION: Containing tbe Elements of Building, Surveying, and Arcliitec. ture ; with Practical Rules and Instructions connected with the sub¬ ject. By A. C. Smeaton, Civil Engineer, etc. In one volume, 12mo. . . . . . • - . . . $1 50 IMITH.—THE DYER’S INSTRUCTOR: 1 Comprising Practical Instructions in the Art of Dyeing Silk, Cot¬ ton, Wool, and Worsted, and Woollen Goods: containing nearly 800 Receipts. To which is added a Treatise on the Art of Pad¬ ding ; and the Printing of Silk Warps, Skeins, and Handkerchiefs, and the various Mordants and Colors for the different styles of such work. By David Smith, Pattern Dyer, 12mo., cloth $3 00 MITH—THE PRACTICAL DYER’S GUIDE: ' Comprising Practical Instructions in the Dyeing of Shot Cobourgs, Silk Striped Orleans, Colored Orleans from Black Warps, ditto from White Warps, Colored Cobourgs from White Warps, Merinos, Yarns, Woollen Cloths, etc. Containing nearly 300 Receipts, to most of which a Dyed Pattern is annexed. Also, a Treatise on the Art of Padding. By David Smith. In one vol. 8vo. $25 00 S HAW.—CIVIL ARCHITECTURE: Being a Complete Theoretical and Practical System of Building, containing the Fundamental Principles of the Art. By Edward Siiaw, Architect. To which is added a Treatise on Gothic Archi¬ tecture, Ac. By Thomas W. Sillowat and George M. Hard¬ ing , Architects. The whole illustrated by 102 quarto plates finely engraved on copper. Eleventh Edition. 4to. Cloth. $10 00 QLOAN.—AMERICAN HOUSES: A var iety of Original Designs for Rural Buildings. Illustrated by 20 colored Engravings, with Descriptive References. By Samuel Sloan Architect, authorof the “ Model Architect,” etc. etc. 8vo. $2 50 OCHINZ.—RESEARCHES ON THE ACTION OF THE BLAST. ® FURNACE. By Chas. Schinz. Seven plates. 12mo. . * . $4 25 22 HENRY CAREY BAIRD’S CATALOGUE. OMITH.—PARKS AND PLEASURE GROUNDS: Or, Practical Notes on Country Residences, Villas, Public Parks, and Gardens. By Charles II. J. Smith, Landscape Gardener and Garden Architect, etc. etc. 12mo. . . . . $2 25 ^TOXES.—CABINET-MAKER’S AND UPHOLSTERER’S COMPA- Comprising the Rudiments and Principles of Cabinet-making and Upholstery, with Familiar Instructions, Illustrated by Examples for attaining a Proficiency in the Art of Drawing, as applicable to Cabinet-work; The Processes of Veneering, Inlaying, and Buhl-work ; the Art of Dyeing and Staining Wood, Bone, Tortoise Shell, etc. Directions for Lackering, Japanning, and Varnishing; to make French Polish ; to prepare the Best Glues, Cements, and Compositions, and a number of Receipts, particularly for workmen generally. By J. Stokes. In one vol. 12mo. With illustrations $1 25 STRENGTH AND OTHER PROPERTIES OF METALS. Reports of Experiments on the Strength and other Properties of Metals for Cannon. With a Description of the Machines for Test¬ ing Metals, and of the Classification of Cannon in service. By Officers of the Ordnance Department U. S. Army. By authority of the Secretary of War. Illustrated by 25 large steel plates. In 1 vol. quarto ....... . $10 00 QULLIVAN.—PROTECTION TO NATIVE INDUSTRY. By Sir Edward Sullivan, Baronet. (1870.) 8vo. $1 50 rrnBLES SHOWING THE WEIGHT OF ROUND, SQUARE, AND 1 FLAT BAR IRON, STEEL, ETC. By Measurement. Cloth ...... 63 rpAYLOR.—STATISTICS OF COAL: "*■ Including Mineral Bituminous Substances employed in Arts and Manufactures; with their Geographical, Geological, and Commer¬ cial Distribution and amount of Production and Consumption on the American Continent. With Incidental Statistics of the Iron Manufacture. By R. C. Taylor. Second edition, revised by S. S. IIaldeman. Illustrated by five Maps and many wood engrav¬ ings. 8vo., cloth . . . . . . . . $6 00 rpEMPLETON.—THE PRACTICAL EXAMINATOR ON STEAM AND THE STEAM-ENGINE : With Instructive References relative thereto, for the Use of Engi¬ neers, Students, and others. By Wm. Templeton, Engineer 12mo. $1 25 HENRY CAREY BAIRD’S CATALOGUE. 23 rjiHOMAS.—THE MODERN PRACTICE OF PHOTOGRAPHY. By R. W. Thomas, F. C. S. 8vo., cloth ..... 75 JiHOMSON.—FREIGHT CHARGES CALCULATOR, By Andrew Thomson, Freight Agent . . . . $1 25 ■TURNING: SPECIMENS OF FANCY TURNING EXECUTED ON ± THE HAND OR FOOT LATHE: With Geometric, Oval, and Eccentric Chucks, and Elliptical Cut¬ ting Frame. By an Amateur. Illustrated by 30 exquisite Pho¬ tographs. 4to. ........ $3 00 ipURNER’S (THE) COMPANION: Containing Instructions in Concentric, Elliptic, and Eccentric Turning; also various Plates of Chucks, Tools, and Instru¬ ments ; and Directions for using the Eccentric Cutter, Drill, Vertical Cutter, and Circular Rest; with Patterns and Instruc¬ tions for working them. A new edition in 1 vol. 12mo. $1 50 J. U RBIN —BRULL. —A PRACTICAL GUIDE FOR PUDDLING IRON AND STEEL. By Ed. Urbin, Engineer of Arts and Manufactures. A Prize Essay read before the Association of Engineers, Graduate of the School of Mines, of Liege, Belgium, at the Meeting of lS(15-6. To which is added a Comparison op the Resisting Properties of Iron and Steel. By A. Brull. Translated from the French by A. A. Fesquet, Chemist and Engineer. In one volume, 8vo. $1 00 •yOGDES.—THE ARCHITECT’S AND BUILDER’S POCKET COM- V PANION AND PRICE BOOK. By F. W. Vogdes, Architect. Illustrated. Full bound in pocket- book form. . . . . . . . . . $2 00 In book form, ISmo., muslin . . . . . . 1 50 ARN—THE SHEET METAL WORKER’S INSTRUCTOR, FOR ZINC, SHEET-IRON, COPPER AND TIN PLATE WORK¬ ERS, &c. By Reuben Henry Warn, Practical Tin Plate Worker. I ius- trated by 32 plates and 37 wood engravings. 8vo. . . $3 CO ATSON.—A MANUAL OF THE HAND-LATHE. By Egbert P. Watson, Late of the “ Scientific American,*’ Au¬ thor of “ Modern Practice of American Machinists and Engi- W W neers,” In one volume, 12mo. $1 50 24 HENRY CAREY BAIRD'S CATALOGUE. WATSON.—THE MODERN PRACTICE OF AMERICAN MA- VY CHINISTS AND ENGINEERS: Including the Construction, Application, and Use of Drills, Lathe Tools, Cutters for Boring Cylinders, and Hollow Work Generally, with the most Economical Speed of the same, the Results verified by Actual Practice at the Lathe, the Vice, and on the Floor. Together with Workshop management, Economy of Manufacture, the Steam-Engine, Boilers, Gears, Belting, etc. etc. By Egbert P. Watson, late of the “Scientific American.’' Illustrated by eighty-six engravings. 12mo. . . . . . $2 50 WATSON.—THE THEORY AND PRACTICE OF TEE ART OF *' WEAVING BY HAND AND POWER: With Calculations and Tables for the use of those connected with the Trade. By John Watson, Manufacturer and Practical Machine Maker. Illustrated by large drawings of the best Power-Looms. 8vo. ......... . $10 00 WEATHERLY.—TREATISE ON .THE ART OF BOILING SU- VY GAR, CRYSTALLIZING, LOZENGE-MAKING, COMFITS, GUM GOODS, And other processes for Confectionery, Ac. In which are ex¬ plained, in an easy and familiar manner, the various Methods of Manufacturing every description of Ravv and Refined Sugar Goods, as sold by Confectioners and others . . . $2 00 W ILL.—TABLES FOR QUALITATIVE CHEMICAL ANALYSIS. By Prof. Heinrich Will, of Giessen, Germany. Seventh edi¬ tion. Translated by Charles F. Himes, Ph. D., Professor of Natural Science, Dickinson College, Carlisle, Pa. . . $1 25 W ILLIAMS.—ON HEAT AND STEAM : EmbracingNew Views of Vaporization, Condensation, and Expan¬ sion. By Charles Wye Williams, A. I. C. E. Illustrated. 8vo. $3 50 WORSSAM.—ON MECHANICAL SAWS: From the Transactions of the Society of Engineers, 1867. By S. W. Worssam, Jr. Illustrated by 18 large folding plates. 8vo. $5 00 OHLER.—A HAND-BOOK OF MINERAL ANALYSIS. By F. Wohler. Edited by II. B. Nason, Professor of Chemistry, Rensselaer Institute, Troy, N. Y. With numerous Illustrations. 12mo. .......... $3 00