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The Columbia University Libraries reserve the right to refuse to accept a copying order if, in its judgement, fulfillment of the order would involve violation of the copyright law. Author: Dowd, Albert Atkins Title: Tools and patterns Place: Date: [ 1 922] COLUMBIA UNIVERSITY LIBRARIES PRESERVATION DIVISION BIBLIOGRAPHIC MICROFORM TARGET ilASTEIl NEQATIVE • ONQINAL MATERIAL AS FILMED * EXISTING BIBUOQRAPHIC RECORD Dowd, Albert AtUns, 1872- Tools and patterns, by Albert A. Dowd "New Tpr^ Industrial extension institute f401 8 j t°^^^^3 i f^^?? and I xvii, service, ii, 446 p. illus. IQh*^.- (Haif-Hik: Factory tnanagement course aia ». Prr4i)v.l0) -^^^^ Series title in part also on t-p. \ Tools.. 2. Machine-tools. 3. Pattern-making. i. Title. Library of Congress Copyright A 503195 TJ1180.D7 18-16995 iiftlillli^ 4i|-|M*''^t-|'^ RESTRICTIONS ON USE: TECHNICAL MICROFORM DATA RLM SIZE: REDUCTION RATIO: IMAGE PLACEMENT: lA /II A IB IIB DATE FILMED TRACKING # : I N I T"I^V Iw^^ FILMED BY PRESERVATION RESOURCES. BETHLEHEM, PA. in Si 8 ■nil' 3 > 03 o m OQ -^3 ^ o>5 ^jKiiiiii^^ ^^^^^^^^^^^^^^^^ < -< N < X o o i i Cn O bo 1.0 rnm 1.5 mrn 2.0 mm ABCO0QN1JKLMNOI>QRSTUVWXVZ tl23«S67890 ABCDEFGHIJKLMNOPQRSTUVWXYZ •bod«lihiikknnofMKStuvwmyzl2345678^ ABCDEFGHIJKLMNOPQRSTUVWXYZ abcdefghijklmnopqrstuvwxp 1234567890 ABCDEFGH I J KLMNOPQRSTUVWXYZ abcdef gh ij k I m n qpqrst uvwxyz 2.5 mm 1234567890 4^ X? 'if 3 O o •ti m u z z s 0 L, -D 30 ^ ^ ^ C. Cd 1 TI ^ s O o» O (I) ; m >! 31 O q 4l I" is fi |i P I cr Is M C/5 oorsi o J LIBRARY School of Business FACTORY MANAGEMENT COURSE AND SERVICE A Stxiea of Interlocking Text Books Written for the liidiistrkl Exiensioii Insittate by Factory Man- agers and CkintnlUng Enj^neers as Part of llie Factory Management Course and Service INDUSTRIAL EXTENSION INSTITUTE INCORPORATED NEW YORK ADVISOBY OOUNCIIi mmoLMB Thul Wwrn, Pwk., Chablbs P. Steinmetz, nwrnuuMB , cmsulting Engineer, CbaSLBB E. Punk, Secy,, General Electric 00. GmsL A. Btockawat, Tmbas., Jmivis R. Harbeck, YUte-PreM. American Cm Co, *™ " Vice-Pret. Strathmore Paper Charles C. Goodrich, Co., Lieut. Oo/. Ord- QitoSrich-Lockhart Co. nance Dept WMliAW W. mm, Charles B. Going, AuMuiaal Engi- Formerly Editor, The Engir PaWte sen** Oornm, •lllHiW ftl*WlrW BTAFF. a R Khoeppel, OMIMUtiHli AlfiMi'** IfKTEB BliWMFIELD, Oon»uUant on PeraonnO. H. A TwOTOiD, mmoLMM Tbobl Wicm ConmOHmg MutirM MmflmMf' DWIQHT T. Fabwham, Con««I«iiHr En§lmM^' WiLLABD L. €AS1, Mt. Wtllard L. Cers back slightly to give clearance when cutting a key way or something of this kind. This clearance also prevents upsetting the metal and raising a bnrr along the edges of the groove. So also the gonge, C, has a slight amount of back clear- ance to facilitate the cutting action. This type of HAND AND FORGED TOOLS 15 ' Shearing Anqfe Giiidtng £cfge A-'' FIG. 4. EFFECT FROM INCORRECT AND CORRECT ANGLES ON GOU) CHISELS chisel is used largely for cutting oil grooves in bear- ings, pulleys, and similar work. It will be seen that this type of chisel is ground at a different angle than the cape and flat chisels. This is done so as to per- mit the operator to change the depth of the cut by raising the end of the chisel a trifle while in use. The cow-mouth chisel is used for chipping circular work; while the diamond point, shown at E, is used for correcting errors when drilling holes, for chip- ping in the corners of dies, and such work. The straight-side chisel, shown at F, is commonly used by die makers for squaring up the sides of punches and dies and for squaring out holes, cutting shoulders, and the like. Scrapers. — ^After a piece of work has been ma- chined, the eye is deceived into thinking that the resulting plane surface is smooth and free from humps and hollows. As a matter of fact, however, 16 TOOLS AND PATTERNS the apparently smooth surface is much like the waves of the ocean on a small seale; hence, if it is neces- sary to have a perfectly fitting piece of work, the **high spots'' must be removed and the whole sur- face worked down more nearly level. These high spots can only be levelled by hand with scraping tools. It may seem strange to the layman that a piece of work, if properly clamped, cannot be finished to a true surface on a high class machine tqol, and if the machine tool itself is in first class working condition, but even under the most favorable con- ditions there is bound to be a certain amount of spring" both in the work being machined and in the tool which is cutting it Hence, work which has been machined shows an infinite number of high and low spots more or less evenly distributed over the surface. If two moving parts were to be fitted to- gether with these high and low spots still upon them, it would only be a short time before the wearing down of the spots would destroy the alignment of the pieces, seriously impairing their accuracy. As an example, consider the ''ways'' of a planer or of a turret lathe: In the planer, if the ways were not scraped to a perfect bearing one side would be very apt to wear more than the other, so that the work produced would not be aoenrate-^it might be taper- ing, convex, concave, or even a combination of all inaccuracies mentioned. In the case of the turret lathe, the center of the turret would not line with the spindle after a short while, and the holes bored and surfaces turned would be tapering or otherwise dis- torted. HAND AND FORGED TOOLS 17 It will be seen from the foregoing that on flat work it is necessary to scrape all surfaces which are to be in moving contact with other flat surfaces. When their contact is with cylindrical bearings, they may be scraped, lapped, or ground according to the par- ticular requirements. The art of scraping requires practice, a nice sense of touch, and a considerable amount of judgment. Many people not conversant with the necessity of scraping bearing surfaces, imagine that the mottled effect produced is for orna- mental purposes, yet it is highly essential on any well-made machine and serves no other purpose than that menticaed. Many varieties of scrapers have been designed simply to fulfill a need for a tool to get at some par- ticular piece of work of unusual form on which a bearing was desired. In Figure 5 is shown a double- end scraper. A, commonly used on plane surfaces and broad work. It wiU be seem that this type has a broad flat surface and is perfectly square across the end. Such scrapers are often made single-ended from an old file, having a wooden handle on one end; but for heavy work the double-end tool shown is to be pre- ferred, for it is not Ukely to spring itillllts weight gives an added advantage. It is important that any scraper of this type should be ground perfectly square across the end so that it will not tend to gouge work when in use. Scrapers are hardened to as high a degree as fire and water and the metal itself will permit. The scraper, B, in Figure 5 is hook shaped, which permits it to be pulled toward the workman instead of pushed away 18 TOOLS AND PATTERNS no. 5. YABIODB TYFE8 (NT BGEAFBH3 from him, as in the case of the double-end scraper. The triangular form, C, is sometimes made from a three, cornered file from whieh the teeth have been ground away. All scrapers are made of high-grade steel, as the service to which they are put is so severe that no economy would be found in using low-grade steel for the parpose. Scrapers of the three-cornered variety are largely used for scraping bearings of cylindrical form, such as the crank-shaft hearings in an auto- mobile, or spindle bearings in machine tools. When flat surfaces are to be scraped, a "master'' or standard surface plate is used and the parts to be fitted are rubbed on it to determine the high spots. In using this master plate a very light coating of Prussian blue, red lead, or lamp black is spread upon the machined work which is then rubbed upon the master plate; the high spots on the machined piece show bright and are removed with the scraper. This performance is repeated until the work shows an even bearing all over. When completed a series of high-point bearing spots very close together is ob- HAND AND FOB0ED TOOLS 19 tained all over the work, so that it has the mottled appearance previously mentioned. Forged Tools. — ^All varieties of work on nearly every class of machine tool require the use of forged tools. Many shapes and forms are adopted, depend- ing on the work for which they are intended. Gen- erally speaking, their construction is such that they can be ground several times before reforging is neces- sary. On lathes and planers they are used to a greater extent than on any other classes of machines, and many tools of the same general type can be used on these two machines. A group of lathe and planer tools, which may be considered as representative types is shown in Figure 6, although many modifications are required to suit particular cases. It is unnecessary to take up of the tools illustrated and describe its functions, for the reason that tools of this kind are so well known that they require little description and can be found na. 6. A GBoup o? fobged tools W TOOLS AND PATTEBNS in every modern f aetory as weU as in those of older davs. The matter of upkeep of cutting tools, however, is a subject which should receive most careful attention; and as the upkeep and productive capacity of any tool is dependent upon its shape we will consider the points which are important in regard to cutting angles and i^apes of the several varieties of tools. It is evident that any kind of cutting tool, to pro- duce its maximum amount of work, should be so shaped and ground that it will remove the metal with the least possible amount of friction. When such a condition is reached the machine tool is at its best, and the work is produced with a minimum amount of labor. Further than this, the life of the tool is pndonged because the periods of regrinding are lessened. The simplest types of tools are used on planer work, for the reason that the cutting action of the planer is along a straight line. On the other hand, a lathe tool is also used on the outside of cylindrical work, in boring a hole, or in turning a taper, so that in each case the tool must be differently shaped in order to clear itself and ^Hum the cMp" to the best advantage. A number of factors must be considered in the de- sign of cutting tools, such as the position of the tool in relation to the work, the spring of the tool under the cutting action, the shape of the work, and the material to be cut. For example, soft and fibrous materials require an entirely different cutting angle than do materials having a short-grained structure. HAND AND FOBGED TOOLS 21 The tool. A, shown in Figure 7, is seen to be im* properly designed for planer work, because an excess of power is required to pull the tool and, further- more, it really does not cut at all but crowds or pushes the metal off. If such a tool were used for a long while under the condition shown it would in wo. 7. THE CUTTING ACTION OF PLANER T00U3 (A) Incorrect Form of Cutting Tool. (D) Abrasive Action of Chips on Face of Tool. time develop a form similar to that shown at D in the illustration, because of the abrasive action of the chips against the tool. It would be perfectly logical to assume, then, that if the tool were ground to this shape in the first place its form would be more nearly correct. The manner in which any cutting tool is supported determines to a certain extent its shape, because the spring of the tool holder may tend to carry it into 22 TOOLS AND PATTERNS the work and produce chatter/' An example of this kind is illustrated in the planer tool. A, Figure & As the work moves in the direction indicated by the arrow, the tool and tool block together will spring (if sufficient pressure is applied), radially from the corner B with a tendency to dig into the work. 1 m.8. FliAKEBtOOIB CA) The Digging Tendency of Tools ProdiictiTe of Chatter. (C) Tool Siirings Away ftom Work and X>oes Not Dig in. For this reason the tool may be made as shown at C, with the cutting point far enough back so that any spring action will carry the tool away from the work, thus obviating chatter." The heel angle of a cut- ting tool should be of such shape as to resist the cutting strain to the best advantage. It is obvious, therefore, that heavy cutting tools, such as those used on a planer, should have a greater body of metal and less clearance behind the cutting edge than those used for a lighter class of work. The diamond-point tool, shown in Figure 9, is a common type of lathe tool, but such a tool is limited HAND AND FOBGfiD TOOLS 23 in its productive capacity by the width of the cut- ting face and the strength of the neck. It is not suited to high-speed work nor to fine finishing, ex- cept on wiry material such as tool steel or alloy steels. In work of this nature it may be used for finishing, providing that a very fine feed is given MG. 9. DIAMOND-POINT FIG. 10. SIDE TOOL FOR LATHE TOOL ROUOmNG DOWN WORK the machine tool and a sUght "drag" is stoned just behind the cutting point so as to produce a burnish- mg effect on the work. Many mechanics use a side tool such as that shown in Figure 10 for roughing, down bar stock, for the cutting face of the tool is wide and it can be made to take a very wide chip if set as indicated in the illustration. In addition to the points above mentioned, when a cutting tool is to be used on cylindrical surfaces, as m the case of a lathe job, the position of the tool relative to the center of the work is of importance, iheoretically a tool should be **on center,'' whether It is boring a hole or turning an outside cylindrical surface. Ijt must be remembered, however, that the inajority of tools are more or less elastic and will show a certain amount of spring which must be taken 24 TOOLS AND PATTERNS into consideration in setting the tool. Hence, if an outside diameter is to be tnmedy for example, the tool should be set slightly below center so that it will not dig in under the pressure of the cut but will rather tend to spring away from the work. Similarly, in boring a hole the tool should be slightly abov^ center so that its spring under the cutting action will also carry it away from the work. But as previ- ously mentioned these points will depend entirely upon the manner in which the tools are supported and upon the direction which their deflection will take under the cutting strain. Grinding Tools.— In past years it has been the custom for mechanics to grind their own tools to any particular kind of a shape that they fancied gave the best results. The natural consequence of a procedure like this was that one man's work would be much superior to another's because of a greater knowledge of tool shaping. At present, however, it is possible to purchase a tool grinder for forged tools so that all tools of any particular variety can be ground to a predetermined angle, even by an inexperienced man. The work produced with tools uniformly ground is much superior to that done by a "hit or miss'' method, and the life of the tool is correspondingly prolonged. In addition, the amount of time lost in regrinding tools is greatly reduced and the labor of a skilled mechanic is not required. In determining proper angles for cutting tools the aim should he toward the ideal form which will turn the chip to the best advantage with the least amount of power and at the same time to give the longest life to the tool. HAND AND FOBGED TOOLS 25 Especial caution should be exercised not to obtain an angle so sharp that the cutting edge will approach the wood tool in shape, for a tool with such an edge would have a very short life and would require fre- quent regrinding. Tools for Holders.— In order to economize in the amount of high-speed steel used in forged tools a number of holders have been devised which require only small sections of such steel. These holders are so arranged that they will take stock of standard sizes and clamp them securely; in this manner they will answer many purposes of forged tools made from high-speed steel, or certain clesses of work they are extremely valuable; but for very heavy cutting forged tools are still preferred in many factories because the heavy forged tools have a greater section and carry away the heat more rapidly than the smaller sections used in holders, and are therefore capable of higher speeds and greater production. This fact, however, does not detract in any way from the utility and economy of the holders mentioned. These holders will be described in more specific detail in the dis- cussion of tool holders* BBOP FORGING AND BLANKING DIES Principlet nf Drop Fixrgiif.— rMtho^ drop f org- ing di«, may be HM^nt when they become greatly worn, they should still be considered as perishable tools; a great deal depends upon the treatment of the die, botli in the process of hardening and also in its use. The eonstmction and form of the die itself makes a great difference in its life, and it is difficult to estimate the number of pieces upon which any die can be used on account of the variations in the form of pieces to be drop forged. When a comparatively small number of pieces are to be made, it is possible to make up cast iron dies, but of course these are not serviceable for any length of time. When only six or eight similar pieces are to he made cast iron dies are most economical. But in work requiring a large production the dies are made of steel containing from 0.45 to 0.60 per cent carbon, and the blocks from which they are cut range between 5 and 8 inches in thickness. Usually the dies are dovetailed, as shown in Figure 11, to fit the drop hanmier in which they are to be used. Since the advent of the automobile, drop forging processes have been greatly perfected, and many forgings are now made which would have been con- DBOP FOifcaiNa AND DIBS tT 2 I FIG. 11. DOVE-TAILED DROP FORGE DIES sidered impracticable a few years ago. The necessity ^ for extraordinary strength in certain parts has led to the adoption of alloy steels for these pieces and drop forgings are made to suit the conditions. Comparatively few pieces of work have a form such that they can be produced in a single pair of dies. When the diameters do not vary greatly in the different sections, circular forms can be made in a single set of dies; but forms of widely varjdng sec- tion require a preliminary "breaking down*' opera- tion, and when a heavy boss is a part of the forging three or four operations may be necessary before the piece is completed. When the forgings are small. TOOLS AND PATTERNS several recesses can be made in one set of dies for breaking down, formation, cutting off, and nicking for breaking off. Generally speaking, it is best to complete a lorging At a single heat if possible, but in some instances sieveral heats may be necessary. When work is of large size and two or more sets of dies are nsed, the hammers can be placed near each other, so that the workman can step immediately from one to lie other without "losing the heat/' In work done on the anvil by hand the smith acts as an artist and models his work to the form re- quired, drawing it out here or there as the design may call for. But when forgings are made in dies, the amount of metal from which a piece is stamped must be large enough so that it will overrun the die a trifle, thus assuring a full die and a forging of proper shape. The "fin" which is squeezed out between the dies at the time of forging must be removed by means of trimming dies. Provision is made in the dies themselves to take care of this fin, as shown in Kgure 12. A wide and rather shallow groove which is cut all around to receive the fin is shown at A, and the manner in which the faces of the dies are some- times sloped away for the same purpose is shown at B. Figure 13 shows a forging of a lever which has the fin, X, still on it, and the trimming die, shown in the lower part of illustration, shears off the fin and leaves the forging clean and ready for use. Cylindrical work can be manipulated by the oper- ator so that no fin will be left by simply rotating the work under the hammer during the process of forg- ing. Drop-forged levers are frequently made with a DROP FOmaiNd AND DIBS ^ S 2 vm. 12. imm vobge die with space wm becetving mns countersunk portion in the center of the bosses in order to facilitate machining, as shown in **A'' of Figure 14. Other cases when the hole itself can be punched directly through the work are indicated in the dies shown at **B'' in the same illustration. Oc- casionally the hole in the boss is taken care of by the method shown at "C*; this leaves a thin web at the center of the hole, which is afterwards punched out without difficulty. So many forms of dies and forgings for all classes of work occur that it is obviously out of the question to do more than out- line the simple form so as to give an approximation of the method of treatment. Blanking Dies.— When work is produced from cold metal the processes used for shaping the forms are TOOLS AND PATTSMMB na. 13. A ROUGH raunNO and vm wmmiko dis very different from those previously described under the head of drop forgings. Cutting *dies should properly include all types which punch or cut out various shapes from the metal as it is fed through the press when the section of the metal itself is not changed to any extent Shaping dies on the contrary include any which change the form of the metal from its original flat condition to one of a different con- tour in which the various surfaces are in different planes. Some dies of the latter class really constitute a combination of cutting and shaping dies — ^the work is first punched out to shape and is afterwards formed. Follow dies are dies which have two or more cut- ting portions acting progressively on the work as it DBOP WOmmQ AND DIBS 31 TO. 14. METHODS OP ^ROVTOING FOR HOLES IN DROP FORGINGS is fed through the press, each stroke producing a finished piece. Dies of this kind are sometimes called tandem dies. An example of this die is shown in Figure 15. It will be seen that the work **A'' has three separate operations all performed upon it in the same die, and yet at each stroke of the press a completed piece is turned out. Gang dies, are often used for small parts in order to save waste metal and, at the same time, to produce work more rapidly. An example is. shown in Figure 16. This illustration shows that several pieces may he made at one stroke of the press with a compara- tively small amount of wasted metal. A compound die is one that is arranged in such a way that the punch and die portions are not separ- ated but are combined in such manner that the upper fOOIiS AND PATTEBNE O nil ISHCO WORK STOCK AFTER BLANKW6 1 PUNCH II 1 u 1 i 0I£ 0 o Q.. o, ■>, 0 PLAN VIEW OF DIE FHi. 15. mvuiMnMmkmsiAJmmvmmsmmwx. and lower half e^ch contam a puncli and die. Such a die has its stripper springs adjusted so that they are strong enough to overcome the cutting resistance of the stock, after which they are compressed untU the end of the stroke is reached. In a compound die all the operations are carried out synchronously while the stock is firmly held; therefore, the work pro- duced hy this type of die is more accurate than those previously described. It is not as simple a die, how- ever, and it requires much more care in setting up. Forming dies are used for work of hollow form, a cavity being made in the die into which the work is DBOF FOB€HNa AND DIBS 33 FIRST OPERATION SECOND OPERATION PUNCH i Ms WG. 16. AN EXAMPIiE OP A GANG ME forced by the press. Drawing dies are used for much the same class of work as forming dies; but in the process of drawing, the flat blank which is being formed is held rigidly between the surfaces of the die so that wrinkles will not form during the draw- ing operation. Curling dies and bending dies are used respectively for turning over the edges of sheet X TOOLS AND PATTERNS metal pieces and tm besding the snrfaee of H piece of work into a partial curve, not, however, a com- plete circle. Sub-press dies, strictly speaking, are not a special class of die except in the sense that the pnnch and die are combined in a single unit by means of guides so that there is no necessity for lining up the lower and upper dies when setting up. A high degree of accuracy is assured when this class of die is used, although the expense of the die itself may be some- what greater. CHAPTER III BULLING, BORING, AND BEAMING DriU8.~^Drills may be considered as one of the most important factors in producing work in any manufacturing plant. A drill must not be considered as a finishing tool, however, although it is possible, if the drill is carefully ground and the work pain- stakingly performed, to produce a clean hole quite close to the size of the tool. For many classes of work a drilled hole answers every purpose, and if followed by a reamer a smooth hole of any required diameter may be readily produced. For bolts or other fastenings of similar character a drilled hole is usually considered commercially good. As in other types of tools, drill shapes and forms are dependent to a certain extent on the class of material upon which they are to be used. Almost any kind of a pointed tool will drill a hole if revolved under pressure, but in order to produce the work properly the drill shape must be suited to the material to be cut. As a preliminary operation in drilling a long hole, it is often advisable to spot the material with a short drill. The stiffness of the short tool is an advantage to start the hole in the right place and not run any chance of the deflection which might take place if a long drill were to be used first. Further- S5 36 TOOLS AND PATTERNS more, a considerable 'saving in drill grinding will result, as the short drill gets through the scale on the work and leaves the long drill to take a clean cut under the snrface of the scale. This treatment is of marked advantage in drilling forgings on the turret lathe. * Drills in common nse are shown in Figure 17. The spotting drill, A, is groond to an angle of 40 degrees in order that the following drill may commence its cut on the lips and not on the point; it will then cut more freely and get a better start in the work. The maimer in which the cutting action takes place with the following drill is clearly shown in the diagram at B. The drill, C, is Uttle used in general manufacturing, ma. 17. VARIOUS types of maiA DRILLING, BORING, FORGING 37 but it is an important item in the equipment of the blacksmith or metal worker. A drill of this type is not suited to deep holes, although is particularly adapted to thin work. It has no twist, and there- fore does not have a tendency to tear and break the metal as it passes through the work. The wood drill, D, is often used by cabinet makers and other wood workers. This drill also has no twist, but is partly cylindrical with a groove for chips on each side. The ordinary type of twist drill, E, is used in general manufacturing work. The angle at which it is usually ground, indicated in the illustration, is about 31 degrees, but the angle of the twist cut varies in different makes; sometimes it is uniformly twisted throughought its length and again it may be made with, what is termed, an increase twist to give greater strength in a tong drill. Twist drills were originally made by twisting up a piece of flat stock, but the present method of manufacture is to mill the helical grooves from a round bar of steel. A shank is pro- vided in order properly to hold the drill and drive it through the work, this portion being either straight or tapering. If straight it may be h^ld in a drill chuck or in a plain bushing with set screws, but if the shank tapers, it is provided with a flatened end, or *Hang,'' which acts as a driver in the drill socket. A modern twist drill has a slight *'back taper" run- ning longitudinally from point to shank so that it will work with more freedom. Body clearance is also provided as indicated in the end view of the tool shown in the illustration. The purpose of the two clearances is to avoid the heating of the drill by 38 fOOLS AND PATTERNS friction in the hole and also to make the entting action easier. The cutting angles of the lip of the drill vary from 59 to 76 degrees depending on the material which is to be drilled; ordinarily a drill fof »teel and iron is ground to 59 or GO degrees, while for brass the angle may be around 75 degrees. It is of the greatest im- portance that drill angles should be equal, for unless this is the ease the hole will be cut too large, as indicated at P, since the tool is working aronnd a false center which is not the actual center of the drill stock itself. In such a case the longest lip governs the size of the hole, as may be readily seen. Another type of twist drill, G, is known as a flat twist drill. As made by some manufacturers it has a flat shank requiring a special form of socket for holding. The Pratt & Whitney Co. make the form illustrated in which an increase of twist is given to the shank portion to provide additional surface which is ground to fit the taper in a standard socket, thus doing away with the necessity for special sock- ets. The advantages ckdmed for this type of drill are that it has greater chip clearance and higher pro- ductive capacity. Ckm DriBs.— When holes are to be drilled in cast iron or other cast metals in which the holes have been cored, another type of drill, often termed a "core drill," is used. Drills of this kind, H, Figure 17, are listed by manufacturers as "three-groove chucking reamers." It may be noted that the end of the drill does not come to a point, as in the case of the regular twist drill, but is blunted because it has no work to BEIIiliING, BOBING, FOBaiNO do at the center. The three flutes tend to keep the tool in a central position while drilling. Four flutes instead of three are sometimes used. In the larger sizes shell drills, K, are founc! to be capable of very severe service. They are held on an arbor like a shell reamer and are generally four fluted. An important point in connection with the use of core drills is that any variation or eccentricity of the cored portion of the work is likely to affect the tool to a considerable extent so that the resulting hole is not true with the remainder of the work. This trouble can be easily avoided by truing up the hole for a short distance with a single-point tool before inserting the core drill, as indicated in Figure 18. Counterbores.— When a shouldered hole is to be made, such as that shown ii^ Figure 19, the counter- bore is generally employed. In order to have the two holes concentric, two methods are possible: In one the we. 18, STABTIHO A HOLE WTTH A STARTINO TOOL PMOB TO rm VS9 OF A conE pmM4 1 m AND PATTBEMS BBIIiLma, BOBINCJ, FORCING 41 MG. 19. VARIOUS TYPES OF COXJNTERBORES work is revolved and the cutting tools are held rigidly without revolving; the holes can then be pro- duced by two or more cuts of the tools after they are set out to the required diameters. In the second method the work is stationary and the tools revolve; the smaller hole is usually made first and a tool called a couiiterliorey A, like that shown in Figure 19, hav- ing a pilot, B, which enters the smaller hole, does the remainder of the cutting on the larger diameter. It will be noted that the action of the pilot in the pre- viously drilled small hole tends to steady the action of the counterbore and produce a concentric hole. Several varieties of connterbores are in use, the principles of which are the same as that shown at A. One type, D, has interchangeable blades or cut- ting lips and removable bushings, C, which allow w( rk to be done in holes of various diameters. An- ot ler tjrpe, E, also has a removable pilot, which can be provided with cutting heads of different diameters, but the pilot does not revolve. If work requiring a high degree of accuracy is intended, the type with a revolving pilot is advisable. Some cases occur when it may be possible to extend a pilot somewhat smaller than the hole, so that it can be guided in a bushing beyond the work itself. In either of these cases there is little danger of injury to the finished surface of the smaller hole. wm. 20. (a) hahd REiiifm (b) plain vltwed chucking (c) mm CHUCKIN0 reamer Beamers. — ^When a hole is to be accurately finished to a given diameter it may either be bored to this size by successive cuts of the boring tool or it may be reamed. A reamer, therefore, may be considered strictly as a tool for sizing a hole. Several types of reamers are in common use and the selection of the type for any particular work depends upon the ma- 42 fOOLS AND PATTEBNS terial to be eiit, tie diameter of the work, and tbe preTions operations which have been done upon it. As reamers are used entirely as finishing tools, the amount of metal which they remove ig small and is dependent upon the diameter of the hole and the nature of the metal. A group of reamers of various types is shown in Figure 20; while the types here represented do not inelmde every variety, they may be considered as rep- resentative. The simplest type in common use is the plain fluted hand reamer, shown at A, which has a squared end to which a wrench or holder can be ap- plied for the purpose of forcing the reamer through the hole. Beamers of this kind are sometimes made with spiral flutes. The plain chucking reamer, B, in the same illus- tration, is largely used in drill press or turret lathe work and is made with either a taper or straight shank. When used in turret-lathe work it is held in a floating holder, different types of which are de- scribed nnder their proper heading. The type of fluted chucking reamer shown at B may have the flutes equally spaced around the periphery of the reamer or they may be staggered so that no two tooth spaeings are exactly alike. The obje ct §f this ar- rangement is to prevent chatter." lii^^ Another type, called a rose chucking reamer, C, is intended for work of a fragile nature or for thin work which might be distorted in reaming with an ordinary coarse-fluted reamer. The rose reamer has wider lands" (space between indentations) and is not lipped Eke the chneking reamer previously men- DMLMNG, BOBINO, FOWIINO win. 21. TTPES OF INSEBTED-BIiADE REAMERS tioned. It should cut only on the end, and the ob- ject of the wide lands on the flutes is to preserve a bearing surface and thus tend to produce greater ac* curacy in the work. Inserted-Blade ReamCTS.— The simplest type of in- serted-blade reamer is the tool shown at A in Figure 21. This reamer is never used with a floating holder, the design being such that the blade, b, floats in the holder, a. Fdr certain classes of work, especially vertical work, as on a vertical boring mill, reamers of this type may be made to do excelliiiliprork. Upkeep IS provided for by means of a tapered screw and a slot in the blade whereby the blade may expanded and reground. On account of the cost of high-speed steel later developments in the de- sign of reamers favor the inserted*blade type so made TOOLS AND PATTERNS that tlie blades can be removed and replaced at a nominal expense. By this means tbe upkeep of the tool is quite low: a number of styles can be purchased ill the Ameriean market. A good example is tbat shown at B in Figure 21, made by the Pratt & Whitney Co. In this type of reamer the body, d, is provided with tapered slots in which the blades, e, fit. The clamps, f, in the sec- tional view, lock the blades by means of the screws shown. Various diameters within the capacity of the reamer can be readily made by manipulating the lock- ing nnt shown at g. It is a very difficult matter to change a reamer adjustment of this kind in such a way that all the blades will cut equally, but it is a simple matter to regrind to the desired size after set- ting the blades slightly oversize to allow for the grinding. Another excellent type of inserted-blade reamer is shown in the same illustration at C. In this type the body of the tool is cut out, as indicated, to re ceive the blades, h. It will be seen that these blades are so made that each forms two teeth, and are held in place by the screws shown. When a reamer of this kind becomes worn so that it does not size the work properly, the blades may be removed and strips of paper inserted under them, after which they can h reground to the desired size. Twpat Beamfin.— Before reaming a tapering hole, the first essential i» «iat the bored hole be true and straight. When the taper is very "shallow"— le., fhe angle of the taper very slight— a single reamer mtk be jmdf as, for inatancei in making a taper pi^ 46 ©^FLUTED 8= FLUTED ROUGHER FINISHER NICKED D BREAK CHIP PLAIN OR NICKED TAPER SCRAPING TOOL FOR LARGE WORK no. 22. TYPES OF TAPER REAMERS / hole; but when a more obtuse angle is required sev- eral tools may be necessary to produce the final taper. For this latter work the first two reamers may be made as indicated, in Figure 22, at A and B. In the tool, A, the flutes are cut straight but are threaded or nicked to "break the chip" and make the cutting ac- tion easier. In order to overcome the tendency to- ward drawing in,*' a slight left-hand spiral may be given to the flutes, the angle of the spiral being de- pendent somewhat on the angularity of the tapered hole. It is also advisable m some cases to space the teeth unequally to avoid chatter which is more likely to occur in taper than in straight reaming. Taper reamers should be made longer than the holes in which they are to be used in order to provide for up- keep. Eoughing reamers should have fewer flutes than the finishing tool for greater chip clearance. TOOLS AND PATTEBNS Taper reamers are occasionally made for large work with a single inserted blade, such as that diowm at C in the Ulustration: A tool of this kind is not, strictly speaking, a reamer, bnt is more nearly a scraping tool. This type of tool is vain, able for some classes of work, however, as it can he adjusted to size very readily and can be reground a nnmb^ of times. iror/r .„ .A 9 mmm - IIO. 23. SnfPLB TTOBS Of BCWINQ TOCKil Boring Tools.— The engine lathe is generally nsed when a hole is to be bored in but one piece of work wMch can be revolved. The type of boring tool used for small holes nnder these conditions is shown ib Figure 23 at A. Due to its construction, a tool of this kind is only suited to very light work, and a number of cuts must be taken to bring the work to the required siae. As such tools are seldom used to any great extent in manufacturing work, it ^ mSlMm, BORING, FORGING 47 unnecessary to mention their shortcomings. They serve the purpose for which they are intended — boring holes in jigs and the like, and therefore need no further comment. Tools of a similar char- acter but somewhat heavier are occasionally used in turret lathe work for boring short holes, al- though a boring bar is generally used when the size of the hole will permit. When a boring tool of this type must be used for manufacturing work, it is better to make it in the form shown at B in the illustration. It will be seen that this tool has a more substantial nose and that it is ground to a different shape than the toolmaker's tool shown at A in the illustration. It will give very good results on short work. When a turret lathe must be used to bore a hole and the size of the hole will permit, it is better to use a bar such as that shown at A in Figure 24. Single-point tools, or tools having but one cutting edge, will produce more accurate work than multiple- cutting tools, although they will not turn out the work as rapidly. The bar, B, made in a variety of ways to suit different conditions, is used in many classes of work. The tool, placed straight across the bar, is held with a set screw or a taper pin, and may or may not have the added refinement of a backing- up screw to make adjustment easier. The bar may »e piloted in a bushing of some kind, or it may be as shown in the figure. If several diameters are to be machined at the same time a multiple bar, C, can be ^ised to good advantage, the general points in con- isiruction being much the same. fOOI^ AND FAvrnmB Flil-Oiitlir Boring Bin« — ^For rapid produeiion flat cutters are frequently used in bars such as shown at D, Figuie 24. The advantage obtained by the use of two euttiiBg edges is that the amount of work performed by each cutter is less than with a single- point tool, and therefore the feed can be somewhat increased. The disadvantage lies in the fact that diameter mm are soon lost on account of re-grind- ing, while the single point tool can be re-set to a given diameter a number of times through a simple adjustment. For very heavy cutting a cutter head is made up similar to that shown at E in the illustration. In boring automobile cylinders, or other work of similar character, tools of this kind can be used to advan- tage, but it is highly important to have all the cutting points ground to the same diameter and angle so that they will do an equal amount of work. Bars of other varieties besides those shown are used in general mannfaetnring, but the working principles are much the same as the ones described. AdjnstaUa Boring Tool for Tool-Room Work.— The requirements of the toolmaker are somewhat differ- ent from the requirements in the manufacturing de partments. Therefore the type of boring tool which he is likely to favor will differ from those previously described and may take the form of that shown in Mgnre 25. This tool will probably be provided with a taper shank, A, which will fit the tailstock of the lathe. The cutting tool itself is small and is held by two screws, as shown, in the swinging block pivoted at B in the body of the toolhold^. The two screws, DmiililKa, dOMH€K FOUeiMG 49 wm. 24. vABious types of bobinq babs TOOLS AND PATTERNS €/mck ? m. 25. TOoi*iiAKiaw^ apjo8tabub bomnq tool C, C, are used for adjustment/ one being loosened and the opposite one tightened until the desired diameter is obtained. Other varieties of this tool may be found in any manufacturers tool room. A tooLaker wiU often have one of his own make which is of course superior to all others." For boring bushing holes in jigs, tools of this sort are almost indispensaUe. Recessing Tools.— In turret lathe work it is often necessary to produce a recess or groove in the in- side of the work. When the work is of medium size, so that a good-«ized tool can be used, no par- ticular difficulty is experienced, for the work can be done by a number of different methods. If the work is done on an engine lathe, a tool may be conven- iently held on the cross slide of the lathe, as* indi- cated at A, Figure 26, and the carriage can be with- drawn until the tool has reached the proper depth, after which it can be fed along the distance re- DEILLING, BORING, FORGING 51 MO. 26. A SIMPLE REGESSINO TOOL ON AN ENGINE LATHE quired to produce the work, as shown at B. It must be remembered, however, that many varieties of tur- ret lathes do not have a cross-sliding movement to the turret, nor does the cross slide in some other varieties have a longitudinal power feed. Hence, it is necessary to design a recessing tool in such a way that it will be self-contained and have its own moving parts, irrespective of the turret movement. Much depends upon the naturo of the groove to be cut If it is narrow, such as that shown in Fig- ure 27, it is easily possible to build a tool of a very simple character to be operated by the wojkman. In this ease the tool consists simply of a body, A, in which the holder, B, is set eccentrically to the center line of the spindle and at a sufficient distance to give the depth of cut desired. The handle, C, hirnishes the necessary feed. When a recess is cut deeply into the work, and m TOOLS AND PATT£BNS wm. 2B. mammm tool wm Tumm mths DBIIililNG, BOBINO, FOBaiNG 53 when the tool extends a considerable distance from the turret face, a scheme snch as that indicated in Figure 28 can be utilized to good advantage. In this case the body of the tool, A, is mounted on the turret and contains a sliding member, B, in which is mounted the recessing bar, C, having a tool at Assuming that there are tools on the front of the cross side, which are used in connection with the work, and that the rear of the slide is supplied with a support, E, by means of which the recessing bar is supported and fed into the work by with- drawal of the cross slide; it will be seen, then, that a movement of the slide will carry the tool into the work as deeply as permitted by the stop screw, F. The slide carrying the recessing bar is controlled by a spring, so that when the feeding pressure is re- leased the spring wiU return the sMe to its normal position. Extraordinary cases occur occasionally in ma- chine shop practice when a number of parts must be made which call for more elaborate tooling than is ordinarily required. An example of this sort is shown in Figure 29. In this case, the work, A, is a steel casing with two recesses equidistant from the center line as shown at B. The work is of large size and requires a 20-inch swing turret lathe to handle it. It will be seen that the two recesses are in such positions that they can not readily be machined. As a support for any tool making this cut is necessary, a bushing has been inserted in the fixture to hold the piece so that a pilot can be used on the bar for re- cessing. This bar has been drilled to receive a rod, TOOLS AND PATTERNS Wm, 29. IM XLAB0R4TB KBCE8BEK0 VOC«< FOR A LABOB STEEL CASINQ C, on which two angular splines have been cut. The splines engage with the two small tool blocks, D, which hold the recessing tools. The mechanism is operated by means of a pinion, E, which engages with a rack cut on the operating bar, as clearly indi- cated in the Ulnstration. It is obvious that any tool of this kind would not be built unless very many pieces were to be ma- chined, as it would not prove economical otherwise because of the high first cost. For the work shown, however, some thousands of pieces were to be made, and the elaborate equipment paid for itself many times over in the saving of time and in the accuracy of pro- duction. As the depth of the recess on this piece was rather important, it was essential that the spacing of the grooves should be symmetrical about the center line, which also made the tool so much more essential CHAPTER IV TURNING, FORMING, AND THREADING Hollow Mills.— In roughing-down bar stock similar to the piece shown at A in Figure .30, a hollow mill is frequently used, but this type of tool is not to be recommended for accuracy. But as it has several cutting lips it will remove stock rapidly and can be used for roughing operations to good advantage. The ring:, B, is used to prevent the lips of the tool from springing and also to make small adjustments by drawinig in the lips to a slightly smaller diameter when necessary, but the adjustment obtainable on this type of hollow mill amounts to only a few thou- sandths of an inch. An adjustable type such as shown at C, is much more expensive but possesses some ad- vantages. The cutting tools, D, D, are of the in- serted type and are controlled as to their diameter by a ring with cams cut upon it which engage with the cutting tools and force them in or out as desired. Although a tool of this type can be more accurately adjusted to a given diameter than the one previously described, it will not remove stock in as great a quantity nor has it the desirable features of chip clearance that the former tool possesses. Another type of hollow mill designed for excep- tionally heavy cutting and large stock reduction is 55 It IHIOIiS AND PATTfiRNB m. 90. wKmtuosTiFmmmoiAmruaiM sliown at E. This tool is of special character and is designed for a single purpose. It will be noticed, however, thallMII^ tools, are adjustable and that they are heavy in section so as to carry away heat rapidly. Tools of this sort are designed only for fhe mmt severe service and are not economiea) TURNING, FORMING, THREADING 57 unless stock reductions are large and a great number of pieces of the same character are to be machined. An important point in connection with all hollow mills is the back clearance which, on the type shown at A should be at least an eighth of an inch to the foot. The cutting edges of hollow mills should be a trifle ahead of the center for steel work but on center for brass. Turning Tools. — On turret lathe work tools used for turning are made up in a different way from those employed on the engine lathe. On the engine lathe the tools are held on the cross slide of the ma- chine in suitably designed tool holders, while in tur- ret lathe work the holders are mounted on the turret and the tools are held either horizontally or ver- tically. One of the simplest types of turning tool is shown in Figure 31, the holders in this case being 31. A smPLB wmatme tool wm TumciBT lathe wokk 58 fOOIiS AND PATTERNS made of easi iron and bolted to the turret face. The tool is set at an angle and is held in place by two set screws. Adjustments for diameters can be readily made within the capacity of the tool. For short lengths and snlall diameters, a tool of this kind will give excellent results; but when the work is long, as in the turning of bar work on a screw machine, it is necessary to provide support for the work opposite to the eutting point of the tool. A simple type of tool for this latter purpose, usu- ally termed '*box tool'', is shown in Figure 32. The 110. 32. A SIMPLE BOX TOOL FOR TURRET LATHE WORK tool is mounted in a block opposite to which a V- shaped supporting block is so placed that it can be adjusted to the diameter of the work being cut. M ttkers of turret lathes have developed a great va- riety of tools along these lines to suit the particular machine which they manufacture. For small screw- maehine work, box tools with two or more adjustable blocks are frequently made which are extremely use- ful for automatic and light hand-screw machine work. Adjustable Turning Tools. — ^For bar work it is very desirable to have tools which can be adjusted rapidly TUBNING, FORMING, THREADING m wo. 33. ADJUSTABLE TURNING TOOL WITH ROLLER BACK RBSTB Pratt & Whitney Co. to various diameters within their capacity, and on turret lathe work several fools of the styles shown in Figure 33 may be mounted on the turret and con- trol several diameters on the bar. Such tools are made with both roller-back and V-back rests, the back rests being adjustably mounted so that they can be used either for following or leading. When used as following back rests, they are set to the diameter at which the tool is at work and sUghtly behind a pomt opposite the cutting tool. When used as lead- ing back rests, the material must either be bright mm steel or it must have been finished to a given ^immeter m a previous operation. Leading back rests can never.be ised on rough stock; but following back rests, as they work directly behind a surface which jas just been finished, are always used in rough »?ock turning. The dilference between the use of the 60 TOOLS AND PATTERNS V-back rest and tlie roller-back rest is that the rollers are less likelv to mar the work, while V-back rests mav cause sUght abrasions, especially if work i» done at high speed. However, on automatic work of small diameter the V-rests are commonly used with per- fectly satisfactory result. - Open-side Turning Tools.— The tool shown m Fig- ure 34 is used for turning short lengths when the no. 34. OPEN SIDE TURNING TOIM^ Pratt ft Whitney CJo. work is held rigidly; therefore it does not require back rest support, A tool of this nature is adjustable to different diameters within its capadty, and some- times possesses an added refinement in an adjustable stop or an index on the screw so that it can be set for different diameters for both roughing and finish ing cuts. Overhead Turning Tools.— It is important that any type of turning tool should be held rigidly to avoid TUBNING, FOBMINa, THREADING 61 FIG. 35. SPECIAL PILOTED TURNINO TOOL imRAPn) PRODUCTION the chatter resulting from excessive vibration. For this reason turret lathe tools for heavy classes of work--such as castings, forgings, and the like— should be so constructed that they will have ample section to withstand cutting strains without spring- ing away from the work. For manufacturing work in large quantities, special tools are frequently built sttch as that shown in Figure 35 at A. It will be seen that this tool is mounted on the turret of the turret 62 TOOLS AND PATTERNS lathe and has additional support from the pilot bar, B, which enters a bushing in a bracket on the head stoek of the machine. The several tools are remov- able and adjustable, so that they can be repW and regronnd when necessary. Such tools are not in- tended for universal use but are specially designed to meet the requirements of a particular case. It is al- ways advisable, in making up a tool of this kind, however, to provide as much latitude as possible, so that in the event of a change in design the tool can still be used with slight modifications. Tuniiii; Tools for Vorfeieal Boring Mills.— Many people do not consider that the vertical boring mill is sufficiently adaptable to handle special classes of manufacturing work to good advantage, but its power and stability are such that, if properly tooled, it will prove a valuable manufacturing machinel The majority of boring mills in use throughout the coun- try are not run anywhere near to their maximum effi- ciency. Only a short time ago, while investigating conditions in an old factory, I discovered three bor- ing mills at work continuously, yet only turning out about one-fifth of the product which they shpuld liave accomplished. When the Superintendent was asked why these machines seemed to be such small producers, he informed me that they turned the work out ''as fast as the assembling room could use it," so lie had no fault to find. The multiple turning tool head shown in Figure 36 gives an idea of the adaptability of multiple tools to a vertical boring mill when the product is suffi ciently large to warrant a little expenditure for tools. TUBNING, FOBMING, THBBADINQ 63 KG.36. SFWJIAL TORNmo TOCM OH A VERTICAL WmiNG MILL In this ease the heavy tool holder, A, contains three tools, B, C, and D, which all work simultaneously on the casting. At the same time the two tools, E, and * , m the left-hand head are at work facing the sur- taees indicated. It is unnecessary to go into the mat- ter of turning tools on the vertical boring mill to any great extent as the more modem machines used in mamifaeturing are provided with a side head in ad- ^on to a turret, each containing a number of tools. When a machine of this type is used, the side head provides a means of setting up four or more tool's to hp °P*''"ate^ in sequence, and adjustment of the side leaa permits diameter settings to be easily made. M TOOLS AND PATTEBNS tMtiMg-M TodhL—The ordiBary type of tool used for cutting off work which has been previously turned or formed is shown in Figure 37 at A. Such tools, however, are uneconomical, for after grinding a few times, they must be annealed and ref orged, or drawn out to their former length. The inserted-blade type wm. 37. TYPES or cwraNQ-ow togim of cutting-off tool, shown at B in the same illustra- tion, is much more economical, for it is so designed that the blade, C, can be clamped securely in the holder and adjusted to any desired position without difficulty. The holder is so made that it will fit sev- eral different sizes of tool posts, thereby making its adaptability to different classes of work and different machines so mueh the greater. In the holder showB, the Tblades can be bought ready-made to slip into the holders, and only require an occasional grinding to keep them in condition. TURNINa FOBMING, THREADING 65 Threading Tools.— The simplest form of threading tools is the forged tool shown at A in Figure 38, Such a tool is used for plain threading on the engine lathe and needs no particular comment as the nature of the operation is so well known. In any threading Work A A"' wm, 38. THE SIMPLEST WORM. OF THREADING TOOL tool there are two essential points; first the correct shape of the tool itself, and second, its setting in re- lation to the work. K a threading tool is ground to the correct angle on its sides and is set on the center of the work, it should produce a threaded form of the correct angle. If, however, it does not come into contact with the work at the proper point, and if the cutting face is tipped one way or the other to bring the point on center, the resulting angle of thread will not be correct. Because of these facts, it is evident that the great- est care must be exercised both in grinding and in setting any sort of threading tool. In turret lathe ^vork, threading tools of the single-point variety can ^ot be used unless the machine is provided with a 66 TOOLS AND PATTEBNS thread-chasing attachment whereby the lead of the screw can be properly controlled. There are many eases, however, when such an attachment is a great advantage, and it is in cases of this kind that a spe cial design of entting tool is desirable. When the thread-chasing attachment is applied to the cross slide of the machine, an ordinary type of tool may be used for the work if desired; but when the thread- ing attachment afleets the turret slide, another type of tool may be found necessary. If the work calls for an interior thread, a bar, such as that shown at A in Figure 39, can be used with a tool of the single-point type, as B, or of the chaser 110. 39. TYPES or THREAD OHASIMO TOOUI TURNING, FORMING, THREADING 67 type, as C. This bar must be held in a special holder on the turret, which provides for quick with- drawal and a micrometer stop for depth. A tool slide of this sort can be easily applied to the turret of the machine and presents no great difficulty in the mat- ter of design. When the turret itself has cross-slid- ing features and a micrometer dial adjustment, there is no necessity for an extra tool holder of the type mentioned. Goose Nedc Threading Tool— Due to the peculiar construction of a threading tool it is very likely to chatter under the cut. As chatter is caused by a rapidly repeated springing away of the tool from the work and by an equally repeated digging in again, both tool and work should be held so rigidly that such vibration will not be possible. Such a condition is difficult to obtain, however, and therefore the tool may be so constructed that it will never have a tendency to dig in. A special tool of this nature, made especially for threading work on the turret Wdrk Turrwf ^ ^Q. 40, A GOOSE-NECK THREADING TOOL FOR TURRET I4ATHE 68 TOOLS AND PATTERNS lathe, is shown in Figure 40. The tool-holder body 18 mounted on the bar. A, which is held in the tur- ret of the machine. The body is drilled at B and slotted at C to allow for springing action. The threading tool, D, is locked in position and is ground to the correct angle for threading. In use, the posi- tion of the spring hinge allows the tool to spring away from the work without digging in. Forming Tools.— When it becomes necessary to machine a form a number of more or less irregular shapes on an engine lathe, turret lathe, or other ma- chine of similar character, a forming tool of some sort is indispensible. When only a single piece is to be made, the operator can work out the shape a little at a time on an engine lathe to fit a templet of sheet steel which has been carefully laid out to the re- quired dimensions. There are many kinds of forming tools whose utility depends to a great extent on the class of work for which thev are intended, as well as the number of pieces which are to be machined and the accuracy required in the finished product. The type of tool selected for any given piece of work, therefore, should be determined by these factors. For example, in the work shown at the upper part of Figure 41, a simple angular groove is to be cut on a lot of 500 pieces. It would be inadvisable, therefore, to go to any great expense in the matter of a forming tool. A rect- angular tool. A, of some standard section should be formed to the shape shown at B with very little ex- pense or trouble, and the work may be produced without difficulty. If such a tool as this, however, TUKNING, FOBMINO, THRSADINe TO. 41. THBES TYPES OF SIMPLS FOElflNa T0(»£ 70 TOOL» AND PATTERNS were to be used day after day and week after week, it would not give good results. Freqnent regrinding would change the shape and size so that it would soon need to be .replaced by another. This is due to the fact that the clearance as indicated by the dotted line is increasingly smaller than the part of the tool doing the cutting, so that as the face is ground away the tool becomes narrower and does not cut a groove of the desired width. To avoid changes in form caused by regrinding, an angularly set forming tool, such as that shown at C in the center of Figure 41 can be used to advantage. In this case a holder F, of special form is provided on the cross slide of the machine, bolted down in some approved manner according to the form of slide on which it is used. The holder is dovetailed at E to receive the forming tool on which the correct form, C, has been fashioned. The design of the tool is such that when it is ground flat across the front it will produce the required form. Clearance is taken care of by the angle at which the tool is set in the holder. Suitable clamping screws are provided in the holder so that as re-grinding is done adjustment can be made to keep the cutting edge always at the center Ine. In a tool of this character, which is required for very wide forms and heavy cutting, a set screw is sometimes placed in the holder directly under the tool to provide a firm support and take the thrust of the cut. When such provision is not made it may be found necessary to "shim*' up the tool to prevent it from pushing down under the pressure of the cut. Tools of this kind are largely used on TURNING, FORMING, THREADING 71 turret lathe and screw machine work for producing various form and shapes up to four or five inches in length. Smaller work, such as that on automatic and small hand-screw machines can be handled to ad- vantage with the circular type of forming tool, H, shown in the lower part of Figure 41. This type is tapped out to receive a screw which passes through a special tool holder on the cross slide of the machine. If the holder is made for the rear of the cross slide, the center line of the screw, K, is from i/g- to 14-inch below the center of the work. Wlien the holder is designed to be used on the front of the cross slide, the center is about an equal amount above the work center, as indicated in the illustration. This arrangement is for the purpose of giving a greater clearance to the tool. It will be seen that a tool of this sort can be ground a great number of times and still preserve its form. Further- more, it is a type not difficult to make, as it can be turned on an engine lathe to the desired form and then cut out, as at M, to give the cutting lip. Since the cutting edge of the tool is not on the center on which the turning of the tool is accomplished, a suitable allowance for this difference must be made when shaping it. Formulas for this type of tool can be found in Machinery's Handbook." MILLING AND PLANING Milliinf PiwefMl. — The process of milling a sur- face or form consists, essentiaUy, in holding the work to be milled firmly and pushing it against a revolving cutter which removes the stock at a very rapid rate. The cutter is held in some ap- proved manner in the spindle of a milling machine, or on an arbor, either in a vertical or horizontal position depending upon the nature of the work and the type of machine to which it is applied. Milling machines are of several fundamental types, each possessing features more or less distinctive according to the manufacturer and the particular class of work for which the machine is intended. Thus we have hand milling machines, plain miHing machines, the Lincoln type of milling machines, uni- versal milling machines, and so on, all of which are built with a horizontal spindle. Then there are vertical, rotary table, multiple spindle, duplex, and continuous milling machines, some of which have vertical spindles while others have horizontal spin- dles or even a combination of horizontal and verti cal spindles on the same machine. In fact, the ramifications in these machines are somewhat diffi- cult to keep in touch with from day to day on ac- 73 count of the many developments in rapid produc- tion processes. Factors Influencing Machine Selection.— When any piece of work is to be machined by milling processes the proper machine to produce it most eco- nomically must first be determined. Next, having de- termined the machine to use, the method of holding the work must be considered and a fixture designed for it; finally the type of cutter to be used must be decided upon. Several factors have an influence on these points and are of great importance. They in- clude: 1. Nature and composition of the material to be cut. 2. Size of the work. 3. Amount of metal to be removed. 4. Accuracy required. 5. Width and shape of cut. 6. Number of pieces to be machined. It is obvious in considering the nature and com- position of the material to be cut that for instance, a heavy piece of alloy steel would require a powerful machine in order to remove the stock to the best advantage, while a light piece of aluminum or brass could be handled more economically on a hand-feed or plain machine. The size of the work also has an effect on the ma- chme to be used, for it not infrequently happens ™t a light piece of work of large size must be ?nachined on a heavy machine solely on account of the range required. In machining heavy forgings 74 TOOLS AND PATTERNS ©f alloy steel, miUiiig machines of great power must be used, and the fixtnres in which the work is held must be of the most massive design in order to hold the work securely and prevent vibration or chatter. The amonnt of metal to be removed affects the selection of the machine tool on account of the power needed to pull the cut. At the same time it influences the design and form of the milling cutter adapted to the work. Speaking generally, surfacing cnts on castings are best handled by a face mill or end-milling cutter ar- ranged to cut either horizontally along the side of the work, if used on a horizontal milling machine, or vertically on top of the work if used on a vertical- spindle machine. Steel work, on the contrary, can more profitably be handled with a spiral milling cutti»r, the cut being taken in a direction parallel with the center line of tkiil^ of rotation. The accuracy with which a piece of work must be finished determines whether a single roughing cut will be suffi- cient or whether both roughing and finishing cuts must be taken. For the general run of work which does not require a high degree of accuracy, a single cut may Im taken with success, but when interchangeable work within close limits of accuracy is to be manufactured it is usually advisable to take two cuts. The width and shape of the cut determine both the class of machine to be used, the kind of cutters neces- sary, and the fixti^re required. In modern practice, a milling machine having both vertical and horizontal spindles is often selected for a piece of work of larg« size and the fixtures are designed so that several pieces MILLING AND PLANING 75 may be machined simultaneously. There are machines on the American market today having as many as seven spindles, all of which may be working simul- taneously on a certain piece of work. Furthermore, the work may be roughed and finished iij the same machine, one **bank'' of cutters serving for the rough- ing cuts and the others for the finishing operations. Obviously, machines of this character are very expen- sive, but for high production work they are great money savers. Here it will be seen that the number of pieces to be machined is an important factor in regard to the type of machine used. Another point in this connection which should not be overlooked is the type of fixture which is used, but— this matter will be dealt with in greater detail under a later head- ing. Milling Cutters.— The milling cutter. A, Figure 42, IS an end mill of the ordinary variety with straight flutes. This type of cutter can be used for milling the edges of a surface on either a vertical or hori- zontal machine, and is provided with a taper shank to fit the milling machine spindle. The form, B, is of the center-cut type. It can be fed directly into the work if necessary, the teeth being so cut on the end as to permit this. With the type A, the form of tooth on the end does not permit such a cut to be taken. The cutter, C, is an end mill of the same general type as that shown at A, except that the flutes are cm spirally. The cutting action on the side of this J^ill is better than that on the straight fluted mill, A, because the entire width of the flute is not all in 76 TOOLS AND PATTBKNS FIG. 42. GROUP OP STRAIOHT-FLUTl, SPIRAIi| AND BHEUb END mUM I contact with the work at one time. The action, there fore, is a shearing cut instead of a pushing cut. Tlii' mill, also, requires less power to drive it and is les likely to produce chatter. MILLING AND PLANING 77 The special form of cutter shown at D is made on the same principle as that shown at C, except that it is intended to cut only on the side. The spiral in this case is much more abrupt, so that the shearing action is very pronounced. A cutter of this kind gives excellent results on steel and produces a su- perior fnish by virtue of its shearing cut. The flutes may be nicked to break the chip; this makes the cut- ting action easier and. is an advantage on very tough and wiry material. When an end mill of a greater size is required, it is evident that it would not be economical to make both tool and shank of high speed steel; hence the shell end mill, E, has been devised. It can be seen that such a mill is easily attached to a stem or taper- ing arbor which fits the conical hole in the mill. The end of the arbor is threaded so that the mill can be forced back onto the taper by 4i|i|.of a nut applied to its face. Shell end mills are made in a variety of ways to suit different conditions"; in the larger sizes, for in- stance, the body of the tool may be made of cast iron or steel with the cutter blades inserted. When in- serted blades are used it is evident that the cost of upkeep is much less than when the mill is cut from the soMd metal, for a broken tooth can be readily replaced with a new one; furthermore, an entirely new set of blades can be substituted for a worn out set at comparatively small expense. Ordinarily, mills ^? five iiglpi in diameter are made from a single' piece of higfi-speed or carbon steel, while those above *is size are made with inserted blades. PATTBJUfS Slotting OntlerB.— If a straight slot, open at the ends, is to be cut in a casting or other piece of work, a plain end mill such as that shown in Figure 42 at A or B can be used. But if the slot is I-shaped, another type of cutter, A, Figure 43, must he used. FIG. 43. (a) tee-slot CITTTER, (b) FISHTAIL CUTTER (C) TWO-UP SLOTTING CUTTER Tkm cutter is commonly spoken of as a tee-slot cut- ter. It will be noted that the neck of the tool is smaller than the cutter, so as to permit under cut- ting the work, or getting the tool down into a slot, etc. This same t3rpe of cutter is also used for cutting the circular slot in a shaft when a Woodruff key is to be inserted. In many kinds of manufacturing work it is neces- sary to cut a narrow slot with rounded ends, as for example a slot, or spline" as it is more frequently called, in a shaft in which a key of rectangular sec- tion is to be fastened to act as a driver for a pulley or a gear. There are several ways to cut such a MIiIiINQ AND PLANING 79 spline, but such cutters as shown at B or C, Figure 43, are most useful. The cutter, B, is termed a fish- tail cutter from its resemblance to a fish's tail. The cutter, C, is a two-lip slotting cutter or routing cut- ter. Both' types are used for the same work, but the latter is used more frequently on cast iron to cut directly mto a piece of work to the depth desired; then the work is fed along to the requiired distance, liie hshtail type is more useful for steel work since It has better chip clearance. These tools are com- monly used on the spUne-miUing machine or on a milling machine with a spline-miUiug attachment for cuttmg slots and splines in general manufacturing WUx Ik. Angular and Specud Cutters—Various types of cutters have been developed for diflferent kinds of work, the shapes being dependent upon the form to be cut and the manufacturing conditions governine the production. In making up reamers, drills, and special tools of different kinds, special cutters are a necessity in developing the required forms. Refer- views shown at A and a mdicate respectively the shape of the cutting edges ot the milling cutters used for cutting flutes in reamers and taps. C and D are used for fluting twist anils and other work of similar character. F and G ^^^'^ly single and double angle cutters used 'drgely tor cutting spiral mills or other work when Z^l\ ^"^^""^^ *° °'i"«'i lies at an «^le to the axis of the work. E, H, and K are cor- '«nng, concave, and convex cutteHh^^etively iHey are used for a variety of purpbtH^j^iJ m TOOLS AND mKtKmB ANGULAR COTTERS WITH THREADED HQIIS Wm. 44. ANGI7LAB AND SPECIAL TYPES OF MILLING CUTTEES work, the radii of the cutters being made up to suit any particular piece 'of work for which they are to be used . When a piece of work is to be machined which does not permit a cntter to be ield on an arbor ex- tending on both sides of the cutter, it may be neces- sary to make up the types shown at L and M. It is obvious that as snch a cutter must be screwed on to an arbor, as indicated, it must have either a right- hand or left-hand thread according to the direction of rotation of the spindle. These cutters can be made up in any form to suit the class of work on which they are to be used. MILLING AND PLANING GOULD AND EBERHAROT PATENT Caiter Work E TO. 45. GEUt-TOOTR ODTTERS AND FORMED CUTTERS 6ear-Tootii and Formed Cotters.— In cutting the teeth in spur gears the cutter, A, Figure 45, is fre- quently employed. This cutter, patented by Gould & i-berhardt, Newark, N. J., is so made that each tooth ;s of shghtly different form than the one preceding It and progressively removes metal left by the pre- ceding tooth. The value of this method of cutting "es in the fact that the stock as it is removed is oroken np into a great number of small chips instead M a comparatively small number of wide chips TOOLS AND PATTERNS The obvious advantage is that the cutting action is much easier and it requires less power than other forms of cutters. With this type, used for roughing only the gear tooth is cut to its correct shape, leav- ing only a small amount to be removed by the finish- ing cutter, as shown at B in the illustration. The manner by which the chip is broken up by the cutter is indicated at C. The ordinary type of ronghmg-out or stocking cutter for gear teeth is of somewhat similar shape, but it makes a cut like that shown at D Figure 45, which, it will be seen does not leave an equal amount of stock all around for the fimshing cutter to remove, for this reason it is not as rffeetive in its work as the other type. In some manufacturing work unusual shapes may be required cut from a flat surface or stnp of metal, and when the quantity demanded is sufficient to war- rant it the form can be milled to advantage by a cutter formed to the correct shape, as indicated at Fi-ure 45. Let us suppose that a number of blocks are to be made from blocks 2 inches long to have a form-Hke that indicated. In order to produce a nuin- ber of pieces of this kind it is only necessary to make up a cutter of the required form and to mill a num her of long strips on the milling machine. The strips can afterward be sawed up into short pieces each ot which is 2 inches long. , i All milling cutters are **relieved'' at the bacK oi the tooth, in order to provide chip clearance for chil^ removed from the work by the cutting action ana also to prevent the back of the tooth from rubbiii on the work during the operation. Formed cutters MILMNG AND PLANING 83 like the one shown at D, however, are given a differ- ent kind of relief, called an eccentric relief, which permits the cutter to be re-ground a number of times after it becomes dull without changing the shape of the piece milled. HisceUaiieous Cutters. — It is obviously impossible to describe and illustrate every type of cutter without entering into a lengthy discussion of the subject of milling. Such a discussion is unnecessary here. The descriptions show that varieties to meet every con- dition can be made. Figure 46 shows a group of common cutters used for various purposes in the average factory. The cutter, A, is generally termed a **hob." It is used for milling the teeth in a worm gear, the work being held on an arbor either on a milling machine or a gear bobber. In making such a cutter the shape first produced is very similar to a worm gear and the teeth are formed by cutting longi- tudinal grooves. Each of the teeth is then relieved, and the cutter, is, hardened and ground ready for work. A hob cutter, when used for a worm gear, must always be made up specially for any piece of work. Gear teeth of the spur variety, however, are cut with so-called generating hobs on regular gear- hobbing machines, which can be bought in stock sizes according, to the pitch of the teeth an^i the kind of machine on which they are to be used. Each hob, however, is made for a specified pitch of tooth and can be used only for this pitch. In this connection an amusing incident occurred some years ago in a New England factory where there were a number of apprentices. One of the ap- m TOOLS AND PATTERNS TO. 46. (a) WORM HOB CUTTER, (b) SIDE OB STRADDM: Mllir mo COTTEB. (C) PLAIN MHjUHO CUTTE R, (d) IN- SEBfBD-BLADE CUTTEB. (e) mTEBIMKING mUA CUTfBB MIMiING AND.PIiANING 85 prentices was sent to the tool room by the tool maker for whom the boy was working, who told him to get **the hob used for the big gear on Machine No. 1272.'' On the way to the tool room the boy forgot the num- ber 0* the machine, but nevertheless he asked the tool crib man to "give me a hob for a big gear." *'What machine is it for?'' the man asked him. **0h, I don't remember the number of the machine, but you better give me the biggest one you've got 'cause it's a big gear.'' Needless to add, he was told to **beat it, and get the machine number." The cutter, B, Figure 46, is a side-milling cutter used as a single cutter for side milling or for facing a piece of work. It is also frequently used in gangs of two or more spaced the required distance apart for straddle milling." For example, if a boss on the end cff a lever needs to be faced on each side, two side-milling cutters would be properly spaced on an arbor in the milling machine so that the distance between the cutters would be the same as the width of the finished boss on the lever. Given the proper kind of fixture for holding the work, then, a great number of pieces could be machined one after the other with perfect uniformity until the cutters were so worn as to require readjustment. For heavy work of large diameter inserted-tooth facing-mills, D, Figure 46, are used both singly and in groups for the same purpose as the side cutter, B. Cutters of this kind are largely used for making heavy facing cuts on both cast iron and steel. They will also produce good results on aluminum or brass. On vertical milling machines and multiple spindle 86 TOOLS AND PATTERNS nuidiiiies this type of eatter is extensively used for general manufacturing. The plain milling cutter, C, is intended only for surfacing or milling broad flat surfaces. It is most frequently used for milling steel. Frequently this cutter is set up with two or more side-milling cutters to mill a flat surface and at the same time to straddle mill both sides. It will be noted that the teeth on the cutter are milled spirally in such a way that as the cutter revolves each tooth engages the work progress- ively with a shearing cut, thereby producing a very fine finish with little likelihood of chatter. It is well to state lit this point that no matter what style d cutter may be used on any piece of work some chat- ter may result. Loose gibbing (loose attaching) on the table of the machine is a frequent cause, the remedy for which is apparent. Another cause is a poorly designed fixture for holding the work or an inefficient method of clamping the work in the fixture. Still another is the use of an incorreet speed or im- proper feed, or a combination of both, which will be discussed in a later chapter. Interlocking Cutters. — ^In many processes of manu- facturing occasions arise when it is necessary to mill a slot in the work to a specified size within close Umits of accuracy. The ordinary type of side- milling cutter, B, Figure 46, if used for this work soon becomes so worn on the sides that, after grind- ing a lew times, it is a trifle under size and does not cut the slot to the required dimensions. When such a condition as this arises, therefore, an interlocking cutteri E, Figure 46, should be used. This illustra- MIIililNe ANB PLANING 87 tion shows that the cutter is really a double cutter, made up of two parts which fit into each other in such a manner that every other tooth laps over an imaginary center line drawn around the circumfer- ence of the cutter. By this arrangement the teeth of the cutter may be adjusted by placing a disc of thin paper between them when they become slightly worn, the paper disc being made thick enough to compensate for the wear caused by hard usage and frequent regrinding. Such a cutter can be kept up to accurate size, and will always produce a piece of work within the required limits. Planing Tools.— Surfaces requiring the greatest ac- curacy are often planed instead of being milled. This is particularly the case with heavy castings such as machine beds and heavy fixtures, or' parts of ma- chines which are a sliding fit on each other— such as the cross slide on a turret lathe, the carriage on an engine lathe, the table of a milling machine and other work of similar character. In large manufacturing work— the building of locomotives, steam engines, compressors, or printing presses— the planer is a valu- able adjunct; but for smaller manufacturing the mill- ing machine is much more largely used, not only on account of its superiority in the matter of rapid pro- ductipn but also because it does not require so experi- enced an operator as the planer. The tools used in planing are generally single lorged tools of a nature similar to those used on the engine lathe. There is a little difference in the shapes of the tools, however, since in the one case the work IS revolving, while in the other the work is moving 88 TOOLS AND PATTBINS along in a horizontal direction. Except for the fact that planer tools are somewhat heavier than lathe tools, there is so little difference in them that it is rather unnecessary to go into an extended description of them. It should also be remembered that the planer is not used to any great extent in interchange- able raiannf actnrey so that the tools are not so highly specialized but, more frequently, are gronnd in a slightly different way to suit the particular case. CHAPTER VI BEOACHING The Purposes of Broaching.— The process of broach- ing holes, either round or rectangular, is by no means new, but modem methods differ from those in use a few years ago. In present-day practice the broach is pulled through the hole as a rule, while the former method favored a pushing action in forcing the tool through. Strictly speaking the broaching of a hole is a shaving operation produced by a number of cut- ting edges on a tool of suitable form. The teeth on the broaching tool are so arranged that progressively they come in contact with the work as the tool is forced through. Each tooth is set out beyond the preceding one a few thousandths of an inch, the amount being dependent upon the length of the broach, the kind of material which is being cut, and the amount of stock which is to be removed. The design of broaches therefore must take into consideration the points mentioned and also the mat- ter of upkeep— re-grinding and replacement when worn. For example, it would not be economical to design and make up a broach which was to be used only for a couple of hundred pieces in as painstaking a manner as though the work consisted of several thousand pieces. It would be the part of wisdom to 80 m TOOLS AND PATTERNS nmke up the tool as cheapl|r m possible consistent with good workmanship; but if several thousand pieces were to be broaehed refinements in design could be made so that replacements could be made as easy as possible. PrtUmiiiaiy Treatmrat— The preliminary require- ments in broaching a hole are that the work shall have been previously drilled or bored, or that an opening of some sort in flie piece is large enough to permit the entry of the small end of the broaching tool. It is also necessary to ensure that the work can be prop- erly held and so located that the broaching operation will be done in the correct location on or in the work. Sometimes a previously drilled or reamed hole can be used for locating the work precisely by slipping it onto a stud on the face plate of the machine. In some eases the broach itself acts as the locating medium. In order that the process of broaching may be more readily understood by the reader, let us assume that a gear blank has been drilled, bored and reamed, and that it is desired to cut a keyway through it, as in X, Figure 47. In this case the face plate of the broaching machine is provided with a ** pull-bush- ing,** as it is called, in which a slot is cut to allow the broach, A, to pass through it. This pull-bushing then acts as a guide for the broach and at the same times locates the work properly for the operation. This broach, A, is called a "keyway" broach and may be purchased cheaply in standard sizes from the makers of broaching machines, or it may be made up in the tool room of any factory at comparatively BBOACHING 91 A - KEV-WAY BROACH O - SQUARE HOLE BROACH Work C- ROUND HOLE BROACH Work 0- RHJR*WY KEY-WAY BROACH ITO. 47. SEVERAL VABIETIES OF BBOAOmNO TOOEB small expense. One end of the tool is slotted, so that a pin can be nsed to couple it to the feed-screw mech- anism of the machine. The teeth on the broach, start- ing at the end where the slot is, are graded in such manner that the first tooth cuts a very shallow groove in the work, the next tooth increases the depth slightly, and the remainder of the teeth act in like manner progressively. The last iMilil five teeth m the broach cut the full depth of the slot, for the purpose of assuring the accuracy of the work in the event that some of the teeth become worn. Broaching a Square Hole.— As a broaching cut of any kind requires a powerful machine, it is evident that the wear on the broach is very severe. There- TOOLS AND PATTERNS for to relieve the machine as far as possible and also to provide for long life in the broach itself, it is customary in broaching a square hole to drill the work out previously to a diameter slightly larger than the distance across the flat surfaces of the square, as shown at Y, Figure 47. The broach, B,. is the type used for a square hole. The slotted end is cylindrical and a trifle smaller in diameter than the previously reamed hole so as to act as a pilot in guiding the square portion of the broach into the hole. Broaches of this variety are made of a single piece of carbon steel, machined to the shape indi- cated, and carefully hardened and ground before being used. The teeth also cut progressively as in the instance previously mentioned, the amount cut by each tooth being slightly in excess of that taken by the tooth just ahead of it. In broaching steel, the teeth of the broach are usually well lubricated at the moment before they enter the hole, thus reducing the friction of the cut and carrying away the heat generated. The proper lubricant is determined by the material which is to be cut. The various important matters connected with the subject of lubrication, however, will be found in Chapter XIX. Broaching a Round Hole.— Formerly, the proper method of obtaining a cylindrical hole to a given dimension was by the reaming process. The ordmary procedure was to bore the hole 'with roughing and finishing boring tools, leaving a few thousandths of an inch of metal to be removed by the reainer Becent developmOTts, however, have shown that a BBOACHING round broach can be used to better advantage. The finish in the hole produced by a broach is superior to that made by a reamer, and the required size can be easily obtained. In the matter of upkeep, also, the broach is superior to the reamer, although its first cost may be somewhat higher. As to accuracy, the modem broaching machine can be fitted with fixtures for holding the work and locating it so exactly that center distances can be precisely maintained.^ As a matter of fact the broaching process may be con- sidered as a precision operation. When it is desired to broach one hole in a piece in a definite relation to another, it is only neces- sary to locate a stud on the face plate of the machine at the proper distance from the center hole and pro- vide a broach of suitable form. It will be under- stood that when the hole is a single one and not located accurately with relation to some other one in the work the broaching machine centers the broach in the work by the previously reamed or bored hole. In such a case no special fixture is needed. In the case illustrated in Figure 48, a very accurate location is necessary between the two centers, A and B, in the work, C, an automobile connecting rod. Prior to the operation shown, the hole, A, has been ed and carries the chuck jaws radiaUy inward or 130 TOOLS AND PATTERNS outward, aeeording as the pinion is operated to the right or left. Air-Operated Chucks. — The advantages of com- pressed air and the many uses to which it can be ap- plied in the factory are becoming more and more appreciated by the progressive manufacturer. Some years ago considerable interest was shown when a machine-tool builder of international reputation de signed and built a very large fixture for use in his own plant, which had a series of clamps by means of which the work was held, the clamps being oper- ated by compressed air. An additional refinement was supplied by the designer in the introduction of a pressure valve so arranged that the amount of pres- sure applied to the clamp could be adjusted to provide the same amount of pressure under any condition. As the work was of large size and peculiar shape, there was danger of distortion if Tom, Dick or Harry were permitted to exercise his judgment in regard to damping the nwk, but the application of compresse I air and the pressure valve made the matter of hold- ing an absolutely safe proposition. In the past few years methods of chucking or hold- ing work on the turret lathe or screw machine have received a great amount of attention, and the prin- ciple of holding by means of compressed air has been made use of by several manufacturers. A very successfnl type of air chuck, made in a number of varieties by the Hannifton Mfg. Co., is shown at 6, Figure 58. In the type shown the jaws are three in number, as shown at H, and on these jaws an adjust- able jaw, K, Is mounted. By means of the screw, h MACHINE IQUIPMBNT 131 MO. 58. TMBEE Ykmsmm OF CHUCKS these adjustable jaws, K, can be set in or out in1| radial direction toward the center of the chuck to provide for holding pieces of different diameter, or they can be set eccentrically at different distances from the center to suit any particular case. On the TOOLS AND PATTERNS adjustable jaws tbe work-holding jaw. My is looated by means of the tongue shown. The operation of the mechanism is as follows: The chuck is slotted in three places to. receive the oper- ating levers, each of these levers being provided with an arm whieh enters a slot iiiM side of the jaws, H. A plunger, 0, runs back through the spindle and connects with the air cylinder at the rear of the spindle. The front end of the plunger is so grooved that it engages with the three lever arms as indicated at P. When it is desired to operate the chuck jaws, a conveniently located two-way valve is opened, allowing the air to enter the cylinder at the rear of the spndle and pull back upon the plunger, 0, which in its turn, operates the lever arm, N, that moves the jaws inward in a radial direction to grip the work firmly. The amount of pressure used can be regulated by means of a pressure valve if desired, depending upon the work which is to be held, so that a delicate pressure or a powerful clamping action can be readUy obtained. Air chueks of this kind are extremely useful for chucking work of various kinds on turret lathes and screw machines, and they can be obtained in a num- ber of sizes and shapes to suit the most fastidious customer. It is evident that special jaws can be adapted without difficulty to chucks of this kind, so that they can be made to handle a variety of work. Fonr-lttiped Iiid«p«admi OhiielL— In the course of general manufacturing, or for work in the tool-room, it happens occasionally that a piece of irregular shape needs to be held. In a case of this kind the MACHINE EQUIPMENT 133 three-jaw chuck cannot be used to advantage since it is adapted only for work which can be centered. For tool-room work an independent chuck is frequently used for holding irregular shapes, the workman set- ting up the piece in the jaws approximately to the center which is to be bored or drilled and then using an indicator on the work to indicate the exact center. Such a chuck is shown at Q in Figure 58. It will be seen that this chuck is indispensable both in the tool-room and for general manufacturing for holding irregularly-shaped pieces on the turret lathe or on the boring mill. When a number of pieces of the same kind are to be chucked one after the other, and when these pieces cannot be held by the ordinary three- jawed, geared, scroll chuck, it is customary to set two of the jaws, or more if possible, to the proper center to act as a vee in locating the teeth. The work is then placed in the chuck with the proper sur- faces against the two fixed jaws, and the other jaws are brought up independently. The construction of this chuck is clearly indicated in Figure 58. The jaws are moved radially by the screws, S, which in their turn are controlled by a socket wrench (not shown in the illustration). The body of the chuck IS generally fastened to a faceplate, as shown at T, which is screwed to the nose of the spindle. The lace of the jaw is provided with a series of notches, so that a special jaw of any particular kind can be easily attached to it. As ordinarily furnished, the Chuck IS supplied with one or more sets of jaws stepped out at different diameters, so that a variety 01 work can be held without recourse to special jaws. lU TOOm AND PATfllMS lH}. 59. MAinirACTUBEMO JkND IIACHIHE VinS Machine and Manufacturing Vises.— The impor- tance of the proper way of holding a piece of work to be inachined cannot be overestimated. Hence, vises are nsed on many classes of machines for hold- ing work during the process of machining. They are particularly useful on the milling machine and the drill press; and recent developments along these lines have developed a particular type of vise called a manufacturer's vise. This vise is more or less adaptable, and suitable stops can be applied and locating pins put in for the purpose of locating a MACHIHE EQUIPMENT 135 small number of pieces and holding them securely. Attachments provide for drill bushings of different sizes, and drill plates to hold the bushings can be applied with little trouble. The Graham Manufac- turmg Co. makes a useful tool of this kind, as shown at A, B, and C, Figure 59. The upper figure, A, shows the vise supplied with special jaws, D, and a drill plate of an adjustable type, E, which can be moved to any desired location over a piece of work held in the vise jaws. The figure, B, shows another plate applied to the same type of vise; the work, F, is held between the vise jaws and obtains its endwise bcation against the stop, G, which is likewise adjust- able. A third application of this vise is shown at C, where a set of special jaws of V-type are used to center a piece of round work, and the drill plate is set centrally so that the vise can be used as a cen- tering jig. An excellent type of machine vise employing a cam as the locking principle is shown at H, Figure 59. This vise, made by the F. C. Sanford Manufacturing Co., IS an excellent example. It can be used as an ordinary vise and adapted to special conditions with standard jaws, as shown at K, or these jaws can be made up in special form to suit particular cases. Approximate location of the jaws is obtained by means of the screw, L; after the location has been obtained the entire locking movement is made by the ever, M, which is eccentrically placed with relation to the link, N, by means of which the jaw is locked, ^wiufacturing vises of this type are coming more more into use and several varieties are on the 136 TOOLS AND PATTERNS American market. They are made in a number of styles and sizes to suit different conditions. The ordinary madune vise commonly found on the milling machine, also nsefnl in drill press work, is shown at 0, Figure 59. This type of vise is operated by a sliding jaw, controlled by a screw which, in turn, is manipulated .by the handle, P. This Yim is made by |||||g||g|||| ^ gharpe Mfg. Co., and can be provided with false jaws to hold special forms of worky as indicated at Q. A vise of this sort is found IB eTery tool crib, usually in several sizes. nip% Dies, and Holdem.— The ordinary method of cutting a thread on the outside of a single piece of cylindrical work is to chase" it on an engine lathe with a single-point tool, gearing up the lathe to the proper pitch, or number of threads per inch, and taking several cuts successively upon it until the desired depth has been reached. When a hole of odd size is to be threaded in a piece of worki the same method may he employed, but the type of tool used is one adapted to internal cutting. Both procedures may be used with success, but they are uneconomical unless the work is of particular accuracy and difficult to get at with some other types of threading tools. A properly equipped tool crib should be provided with complete sets of taps, dies, chasers, and suitable holders for them, so that any type of standard thread can be cut without difficulty. If the thread to be cut is difficult of access, the lathe method may be the only one possible. Mgure 60 shows, at A, a standard type of hand tap which is commonly used in connection with a MAOHINIS EQUIPMENT If? jia. 60. TAPS, mm, and houhhs wrench, B, for tapping out a hole by *'man power." The tap itself is squared on one end so that it can be readily held in the adjustable jaw, F, by a turn of the threaded handle, G. The same taps are also used in a releasing tap holder when used on a turret lathe or a hand screw machine. The ordinary type of spring threading die^ shown at C, in the same illustration, is commonly used in a die holder such as that indicated at D. Such a die is used for thread- ing screws, studs, or other eylindrical work, either by hand or by a screw machine; the holder, D, being used when the work is done by hand. A special type of holder is used on the screw machine, which is of the releasing variety such as that used for holding a tap on the same machine. If the taps and dies mentioned are used on a screw niachine or turret lathe, it is necessary to reverse the machine in order to back off the tap from the TOOLS AND PATTERNS work after the thread has been cat. So also, the spindle on the engine lathe must be reversed in cut- ting a thread and the tool run back out of the way. (The more modem varieties of engine lathes are provided with a form of indicator which makes a reversal of the spindle unnecessary.) Naturilljr a considerable loss of time is entailed by this oper- ation, and in order to overcome it another type of die heady called an opening die, can be used, whereby it is unnecessary to reverse the spindle. An opening die of this sort, E, Figure 60, is made by the Geo- metric Tool Co. It can be supplied with chasers, E, which may be made for any form or pitch of thread within the capacity of the die head. The chasers accurately fit slots cut to receive them in the face of the die head, as indicated in the illustration. In operation, when used on a turret lathe or hand screw machine, the shank, L, is held in the turret and the open end, containing the chasers, is fed onto the work until a predetermilied stop has been reached, at which time the chasers fly open and permit the die head to be drawn back out of the way. These die heads are extremely useful in manufacturing work. Although their first cost is high, the fact that a single size of holder can be used for many sizes and varieties of threads by the simple substitution of a different set of chasers, makes it an economical proposition xa ftie machine equipment. FIXTURES FOR PLAIN AND STRADDLE iflMilNQ Nature and Variety of Fixtures.— The process of milling has taken the place of planing to a great extent in the general processes of interchangeable work, except in cases where the size of the piece is too large to be handled to advantage on a milling machine, or when the accuracy required, or the shape of the piece is such as to make it impossible to mill the surface. There are a number of different types of machines which are adapted to the milling process and it naturally follows that the type of milling fixtures which are used on the various machines must be so de- signed that they will apply to the particular type on which the work is to be done. Thus, if a piece of work is to be handled on a milling machine having a horizontal spindle, the fixture will be so designed as to present the work to the cutter revolving in the same way that a carriage wheel turns. Or again, if a fixture is to be used on a milling machine having a vertical spindle, the fixture must be so designed as to present the work to the cutter revolving in a hori- zontal plane, like a top. The two most important types of nulling machines i^sed in manufacturing are those having a horizontal 138 TOOLS AND PATTBBNS spindle and those with a vertical spindle. Variations of these types are found in those that have more than one spindle, such as duplex machines and multiple- spindle machines. In the duplex type, the spindles are opposed and can he adjusted towards each other until the ends of the cutters strike. The multiple- spindle machines have from four to seven spindles, some of whidi are arranged horizontally and others vertically. It is evident that in the design of any milling fix- ture, the first point to be taken into consideration is the nature of the work and the material to be cut. The next point is the type of machine which is best adapted to the work; and the third point is the method of holding the piece when it is being machined. Heoesaity for Proper Holding. — The most important point in connection with the design of milling fix- tures is the proper holding of the work; for it must not be distorted by the pressure of the clamp used in holding it in jdaee and, at the same time, the method of clamping must be so rigid that there will be no possibility of chatter" which would result if the work were allowed to swing out of position under pressure of the cot. In this matter of holding, the ingenuity of the tool designer is the important fac- tor, also, the lift or dragging action of the cutter while it is engaged with the work must be considered. A piece that has previously been partially ma- chined, with either holes, slots, or other finished sur- faces, will naturally require different holding methods than those used for rough castings or forgings. For in performing a second or third operation on a piec« FIXTURES FOR PLAIN AND STRADDLE MILLING 141 of work, it is essential that the location should be positively determined by one of the finished surfaces. Which surface is to be used as a locating point must be determined by the nature of the work and the sequence of the various operations upon it. Let us assume, for instance, that a lever having a boss at each end has been drilled and reamed at one end through the boss, and that the other end is to be straddle-milled." It is obvious, then, that in order to locate the piece properly so that the second milled surface on the boss will be at right angles to the hole, the work must be located by a stud in the hole, and must be set up on the fixture in such a way that the damps will not spring it out of alignment. In work that has not been previously machined and is still in the rough state, the locating points must be so placed as to center the work in relation to the cut which is to be taken for the greatest degree of profit. Milling Fixture for a Connecting Rod. — ^An excel- lent example of a milling fixture designed to handle a drop forging of an automobile connecting-rod is shown in Figure 61, the work Being shown at A, and the sur- face which is to be milled being the small end-boss, B. In this milling operation, which is called straddle billing, two cutters of the side-milling type, C, are set up on an arbor, D, and are properly spaced with a collar between them so as to make the distance between the cutting edges of the two cutters the same width as the thickness of the boss to be milled. In the example shown, the boss, B, is located in a ^^-block, E, the angular surfaces of which tend to 142 TOOLS AND PATTERNS HO. 61. simpijE straddle-milung fixture fob a CONNECTING BOD center the boss correctly. The large end, F, is dropped down upon a locating pin, 3, in the base of the fixture, and two side stops in the form of pins, H, are set into the lug, K, which is a part of the fixture base. The upper portion of this lug is pro- vided with a set-screw, L, which acts upon the small boss, B, to hold it firmly down in the V-Mock. A cam lever, M, works against the side of the connect- ing rod and throws the piece over against the two pins, H, which give the work its location, A fixture of this kind may be manipulated very rapidly; the design is extremely simple and can be made cheaply. In addition to this, the method of holding the work and supporting it under the cut is so rigid that there is no likelihood of chatter. Such a fixture can be made up to hold a couple of pieces if desired, in which case two gangs of milling cutters FIXTUBBS FOR PLAIN AND STIABBMS MMMMQ MS m. 62. DOIJBLE-STRADDLS: MUiLING TDmjRE FOB AN AUTOMOBI^ CONNECTING ROD would be required. All milling fixtures are provided with keys such as those shown at N, and are also slotted, as at 0, so that they can be held down on the table of the milling machine by means of T-bolts. Straddle Hilling Fixture Working from a Finished Surface. — The connecting-rod shown in Figure* 61 is an excellent example of another type of fixture. Let assume that after the first operation has been done, a hole is drilled and broached to size in the l>oss, B. After this operation it becomes necessary to mill the other end of the connecting-rod, using the 144 TOOiiB AMD PATf SBNS hole in the smaller boes as a loeating point. In this manner the large boss, F, can be milled accurately at right angles to the hole. Keferring to Figure 62, the method of setting up for this operation will be clearly undmtood. The plan view above shows two connect- ing rods, the small bosses of which have been milled with holes drilled and broached in the manner just described* In the first place, the bosses, B, in the small end have plugs, Q, inserted in them which snugly fit the holes. These plugs rest in two pairs of V-blocks, E, for purposes of alignment, and the V-blocks are fin- ished on the surfaces, P, so that the sidewise location is assured. The other end of the work which is to be machined drops down upon the finished pad, B, on the base of the fixture. When the connecting-rods are to be clamped in place on the fixture, the strap, S; is placed across the two rods and the nut, T, is tightened, thus securing the work firmly. A coil spring, U, is placed under the clamp in order to assist in raising it when the work is being removed from the fixture. It will be seen that this method of locating from a finished hole, and also the method of clamping with a strap across both pieces, makes it possible to set up the work without any fear of distorting it or throw- ing it out of alignment. Fixtures of this kind are in common use on many varieties of work and can be applied to other instances in which the same prin- ciple is involved. Both of the fixtures shown in Figures 61 and 62 are adapted for use on a horizon- tal type of milling maehine. FIXTUBBS FOR PLAIN AND ST im m Gang MilHng.— In milling several surfaces of vary- ing depths on any piece of work, if the production is sufficient to warrant the work being done in a single operation with a gang of special cutters, a fixture should be designated so that the cutters may be mounted on an arbor to obtain the proper spacings and depths. A good example is shown at A, Figure 63. In this case the work has several shoulders and several plane surfaces of different heights, as shown in the illustration. The milling fixture is of ex- tremely simple type, and is nothing more nor less than a cast-iron block, B, grooved and finished at C and D to give the proper location to the work in relation to the table. A set-screw, E, or several set- screws, according to the length of the work, is used to clamp it against the surface, D. An important feature in the design of any sort of milling fixture in which the work is located against finished sur- faces, is the groove, F, the purpose of which is to allow any dirt or chips which might accumulate in the fixture to be swept out of the way and passed down into the groove so that they will not interfere with the location of the work. The cutter gang, shown at G, H, I, J, and K, is so arranged that it will give the proper spacing and depth. Many varie- ties of work can be handled with a set of cutters of similar character to these, and the work can be pro- duced at a rapid rate and within good commercial limits of accuracy. End Milling a Slotted Bracket.— It is frequently necessary in the process of manufacturing to cut a 146 TOOLS AND PATTERNS FIG. 63. MXTURES FOR VARIOUS KINDS OF MILLING OPERATIONS slot in a casting or forging which will bear a certain relation to some other finished surface. An example is shown in Mgnre 63 at L. In this example the bracket, M, has been previously machined at the side and base, and it is now necessary to cut the slot, N, in a certain relation to these two surfaces. The method of setting np the work in this ease is Terj FIXTURES FOR PLAIN AND STRADDLE MILLING 147 simple, as the fixture itself consists of an angular plate, 0, which is fastened down to the milling ma- chine table in the usual manner. The work is located on the finished pad at the base and against the side surface, being clamped in position by means of the two bolts shown. The cutter which is used for this work is a spiral end mill, P, which is clearly shown in the fixture. In operation, the table feed of the milling machine is started and the work is run di- rectly by the cutter at the position indicated. Fixture for Angular Hilling.— Taking as an ex- ample the same bracket shown at L, let us assume that an angular surface, Q, is to be miUed upon it in another operation, bearing a certain relation to the previously finished surfax,^. A piece of work of this kind may be handled in three different ways, but in order to make the application of the milling machine more clearly apparent, let us assume that in this a horizontal type 6t machine is used which hasVHB vertical milling attachment that can be swung to any desired angle. The procedure then would be to set over the vertical attachment to the desired angle of the finished surface, Q, and to locate the work hori- zontally as in the preceding instance, using a type of fixture shown at R, with suitable locaters and clamps. A milling cutter of the spiral end-mill type is inserted in the milling attachment as indicated at S, and the machine table is fed under the work while in the position indicated. Another method of handling the same piece of work would be to build the fixture itself on an angle with the table, so that the surface, Q, which is being milledi 148 TOOLS AND PATTERNS would lie parallel to the table itself. In snail a case, an ordinary type of plain milling cutter would be used, the cutter having straight cutting edges parallel to the surface of the table. The work could also be performed in the same fixture as that shown by swinging the vertical milling attachment to another angle and using the end of the mill for making the cut, instead of the side of the mill as indicated in the drawini^. Fizlmre fer Form IDIHns:.— Let it be assumed that a piece of work, T, is to be formed to the contour shown. The work has been previously machined along tiie base, but has not been surfaced on the edges. It is necessary to reduce the form that is parallel to the lower surface and approximately in line with the edges of the work. 1m this ease the fixtnra, Wf is of U-section, bolted to the table in the usual manner, and located by means of tongues in the table T-slots. Two adjust- able studsy W| are furnished along the side, and against these stn^ fhe rough side of the work is located, being clamped firmly against it by means of the thumb-screws, X. It is customary, in work of this kind, either to build a fixture which will take a number of pieces ot the same kind, or else to make the work in a single strip and cut it up into pieces of the desired length after it has been machined. Naturally, the process which is to be used determines the method of holding and clamping. The formed milling cutters, Y, and side milling cutters, Z, are made up to suit the contour of the work to be manu- faetmred. FIXTURES FOR PLAIN AND STRADDLE MILLING 149 HQ. 64. DOUBLE INDEXING FIXTURE FOR STRADDLE MILUNO LEVERS Index MilMng a Pair of Levers. — ^When rapid pro- duction is desired on a piece of work it may be pos- sible and profitable to arrange a fixture similar to that shown in Figure 64. Here we have two levers of identical size, but the bosses on the ends are of two different widths. They can be machined in a single setting by a suitable arrangement of the fix- ture and cutter. In the case shown the levers have a boss at one end, as at A, and at the other end, as at B. The fixture is built so that it will hold the two levers in such a way that a large and a small end are successively presented to the cutters at A and B, and these cutters are spaced so as to mill different widths according to the thickness of the bosses. The fixture locates the work in each case against the small set-screws, C, to give sidewise location against the sides of the lever, and suitable V-blocks, D, hold the bosses centrally. The V-blocks are at one TOOLS AND PATT£fiNS end only, the other enda rest against the angular sur- face, £. ^Ehnmb-serewsy P, are provided on each side of the fixture to hold the work against the set-screw, C. A rocking clamp, G, on each of these set-screws equalizes any variation in the forging and makes the damping action positive. An ordinary strap clamp, H, holds the work down on the fixture. The method of using the fixture is to mount it suit- ably on a base, such as that shown at K, centering it by means of a central -jpiugf L. The base is fastened down to the table of the milling machine, but the upper portion, M, can be swung around through an arc of 180 degrees so as to present the opposite ends of the levers to the cuttero in sequence. Indexing is usually performed manually by the operator with some type of locating pin which gives the correct location when indexing from one position to another. A scheme for accurately indexing a piece of this kind will be described under the next heading. The fore- guing fixture mills two ends of two bosses at the same time and is then indexed to mill the two oppo- site ends, so that four ends of the two levers have been machined at a single setting. But it must be recalled that a fixture of this kind is not economical unless a number of pieces are to be machined. Indttx WSOing nxtane for Quantity Production.->In work that is being put through a shop on the inter- changeable system, as in automobile production or other manufacturing where a number of pieces of the same sort are to be successively machined to a given size, a number of pieces are usually found which re- quire some sort of an indexing fixture for milling mXTWMB FOB FliAIN AND STBADB]j£ MlMilNa 151 j/^imf ■ VIO. 65. SUIHJS INDBX-lfUlINO WiXTU«E slots, clutch teeth, and the like. The progressive de* signer of tools, therefore, usually designs some sort of universal milling fixture which has sufficient flexi- bility that it can be adapted to such a variety of work. For example, while supervising the work on a large automobile plant equipment for a Eussian corpora- tion, I used recently the type of fixture shown in Figure 65 over twenty times on as many differ^t cases. The indexing mechanism and the base of the fixture were practically the same in every case; the only differences were in the number of points of in- dexing and in the adapters which were used to hold the different shapes to be milled. A particular ad- vantage in this type of fixture is its adaptability to ^Ufferent conditions, and also to the fact that it is practically impossible to destroy the correct indexing 152 . TOOLS AND PATTERNS of the fixture, as the mechanism is so well protected from chips and dirt that no trouble can be caused thereby. As this fixture is so notably flexible, it is worth while to describe it in greater detail than might otherwise be deemel necessary. The base of the fixture, A, is fastened to the milling machine table by the bolts shown, being located in the usual manner by keys in the table T-slot. A revolving table, B, is suitably mounted on a stud, C, IE the center of the base. On the under side of the table a hardened tool-steel indexing ring, E, is se- curely fastened by means of screws, and is provided with angular slots, F, around its periphery, as many in number as the indexing points which are to be made. A sliding block, G, is located radially in rela- tion to the index plate and- is tapered on the end which fits the angular slot in the index plate, thus determining the radial indexing points on the fixture. The movement of this sliding block is controlled by a handle, H, and it is drawn back into position by the spring, K, when the proper indexing point has been reached. It will be seen that the location of the slots in the index plate is such that it is practically impossible for any chips or dirt to interfere with the proper location of the table. The upper part of the fixture can be fitted with adapters of liferent kinds to hold various shapes or forms which are to be milled. The work shown in the illustration is a cylindrical piece, L, which is squared up at the upper end by the two milling cutters, M. This piece of work is located on a spring stud, N, expanded by means of the bolt, HXTUBBS FOB PLAIN AND STRADDLE MILLING 153 0, SO that all chance of vibration is taken up and there is no possibility of chatter during the progress of the work. A hand lever, P, is provided on the table to index it from one position to the other; but this feature is unnecessary in many cases as the workman can use the work as a lever for indexing the table. However, a series of holes around the per- iphery of the table allow the pin to be inserted at different points to provide for a circular indexing movement when needed. This type of fixture is prob- ably one of the most useful that can be made to handle a great variety of work, and although its first cost is fairly high it should not by any means be con- sidered an expensive fixture. C/JHAPTBR XI MXTOKES FOB CONTINUOUS MILLING The Value of Simplicity.— It is an eeoBomical propositiciiiy when a great nmnber of pieces of the same kind are to be machined by the process of mill- ing, to make the fixtures wherever possible in such a way that there will be as little lost time as possible eansed by taking ont and pntting in the woA. It is most advantageous to arrange a milling fixture in such a way that the cutters will be working as nearly continuously as possible. Several methods ean be employed, depending upon the class of work to be done and the machine which is used for the work. On the regular type of horizontal milling machine some classes of work can be handled in an almost continnons manner; although the cutting action will not be absolutely continuous, there is very little lost time between cuts and it is unnecessary to stop the machine at any time. A special type of milling machine, called a con- tinuous miller, is made by the Becker Milling Ma- chine Company. This machine uses a revolving table and a series of fixtnres arranged radially on the table. The Potter and Johnston Company also make a con- tinuous milling machine having an indexing table on which the work can be set up on one side of the table 1S4 FIXTURES FOE CONTINUOUS MIMiINO 155 TO. 66. SIMPLE TYPE OP CONTINUOUS MILLING FIXTURE while another piece is being machined on the- oppo- site side. The Beaman and Smith Company make a large machine with seven spindles which can be used for continuous milling on large work. These various machines require somewhat different types of fixtures because of their different arrangement of spindles. In selecting the simplest of continuous milling fix- tures, let us look at the one shown in Figure 66, which is made for a horizontal milling machine. The work in this case is a bracket, A, shown in the upper part of the illustration. ' The bracket is to be straddle milled by a gang of cutters, as shown at B, which are used to face the sides of the bosses as indicated in the upper part of the illustration. The fixture base, G, is located on the table of the milling machine in the usual manner and has at each end a simple type of locating and clamping device in which the work 156 TOOLS AND PATTERNS is located and held. A sectional view of the arrange- ment is shown at the left-hand pfortion of the figure. The other end is identical with it. The work is placed in the position shown, resting against the stop pins, D, and is clamped in place by means of the screw, E, at the top of the fixture and by the clamp, F, at the bottom. The latter clamp is operated by means of the thumb nut, G, and is released by the coil spring, H. In operation, the work is placed in position and clamped on one side of the fixture; the table is then moved inward close to the revolving cutter, and the feed is set in operation. While the table is moving forward and the peee in position is being milled, the operator places another piece of work in position and clamps it at the other end of the fixture. Then, after the work at one end has been completed, the table is moved over to machine the other piece; the first piece Is removed from the fixture and another one is in- serted in its place. By this description it will be seen that the process of milling is nearly continuous, and for certain classes of work this fixture can be used to good advantage. Continuous Milling Fixture for Cfylinders.— The Beaman & Snuth coBtinuous milling machine makes possible the machining of surfaces of large size in such a way that the action of the cutters with prop- erly designed fixtures, is practically continuous from the time the machine starts in the morning until the factory closes at night. The construction of the machine is such that there are a number of tables similar to, but somewhat shorter than, a planer FIXTURES FOB OONTINIJOUiilMWG ISf MO. 67. CONTINUOUS MJIUNQ FIXTURE FOR AUTOMOBILE CYLINDERS table, and each of these tables can be equipped with a similar set of fixtures. These fixtures can be loaded one after the other and placed in engage- ment with the feed mechanism of the table, one fix- tare following the other closely with very little space between. The fixtures pass through the machine from one end to the other, the finished work is then taken off and is replaced by other pieces, after which the entire table with the fixtures mounted on it is carried around to the original starting point and started again on its journey through the machine. For some classes of work four or five of these tables w»ay be required, each with the same type of fixture ^Pon it. In milling the cylinders, transmission cases, and crank cases of automobiles, as well as in other TOOLS AND PATTERNS wofk of similiiir characteri the production wMeh can be obtained from a macMne of this kind is extremely high. Under favorable circumstances from 300 to 400 automobile cylinders of 4^-inch bore can be produced in a ten-hour day. A good example of a continuous milling fixture for automobile cylinders is shown in Figure 67. The cylinders, A, are to be milled on the surfaces, B and C. They ha¥e been previously machined on the end and in the bore. The cylinders are located on plugs, E, shown dotted in the bore of the cylinder. Each fixture is capable of holding six cylinders at one time. The fixtures are held down on the table by means of clamps and T-bolts in the T-slots, and the work is held down on the fixture by means of the clamps shown at F and G. In the case shown two milling cutters operate on the u]^r part of the cylinders and two more opposed to each other are used to machine the surfaces on the sides. Fixtaro for ''Becker" Continuous Milling Machine. —The Becker type of continuous milling machine uses a revolving table which is in continuous operation after the first pieces have been set in place on the fixture. The fixture, shown in Figure 68, is built to accommodate twelve wall bearings, as seen at A. These bearings are located in position by the fixed studs, B, which act as a vee, into which the pieces are forced by means of the sliding V-block, C, oper- ated by the thumb-screw, D. After the first pieces have been placed in the fix- ture, the operator simply removes the finished work and continues to place new pieces in the position PIXf CUES FOB OONTINUOUS MIMiINQ im m. 68. ooimNuoiis icnuKo iixTtjRB for bsckee muuhq occupied by those just finished. It will be seen that as the cutter, F, is in continuous movement, it has a contact with several pieces at the same time. In the case illu»trated the work is of such nature that there • IS very little "dead time," or time when the cutter ^ not in contact with the work. This example, there- fore, is an excellent one to show the value of con- tinuous milling and how it can be applied to manu- 160 TOOLS AND PATTEBNS faetnring work. However, when the shape of a piece of work is such that it cannot be set up on a cir- cular fixture without leaving wide spaces between the pieces, it is not advisable to attempt to mill it by the eontinnons milling process; but with work that can be set close together, it is usually highly profitable. Spline-Milling .Fixtures. — Some years ago the cus- tomary method of ^tting a slot in a shaft for a key- wav was to drill a hole at each end of the slot and then mill from one hole to the other. This process, nec- essarily, was somewhat slow, and it has been largely replaced by seme form of spline-milling machine or a spline-milling attachment applied to a plain milling machine. The machine that is manufactured by the Pratt ft Whitney Co. for this purpose consists of two opposing spindles arranged in such a way that they feed automatically towards each other during the process of the work. The table is reciprocated, with the work in position on it, to a specified length of stroke determined by the length of the key-slot. The fixtures used for this machine may be those which hold a single piece for cutting two slots opposite to each other, or it may be arranged to hold several pieces in which one or more slots are to be cut. Spline-milling machines are well adapted for all kinds of rectangular key slotting, unless the work to be done is of such a size as to be prohibitory. For all kinds of shafting, arbors, and similar work, it can be arranged without the necessity for any elab- orate fixture. In some cases, however, in order to FIXTUEfiS mm CONTINUOUS MIIiIiINO lil mo. 69. DOUBLE SPUNE-KILLINO MXTXIBE increase production, fixtures may be made to suit particular cases. A spline-milling attachment for a hand-milling machine, made by the Standard Engineering Co. to ^PPly to one of their hand milling machines, is also very useful for milling key-slots, although but one cutter is used at a time. The attachment is pro- vided with automatic features which make it val- uable for many kinds of manufacturing. In the at- tachment mentioned, the spindle is vertical in rela- tion to the table of the machine. On the spline- DTiilling machine, however, the two spindles lie in a liorizontal plane. Let it be supposed that a piece of work, such as that shown at A, Figure 09, is to be splined or cut tooijS and patterns 011 tlie mA with four keyways, as indieated at B in the end view. This piece having the four slots at 90 degrees apart on the periphery, requires some sort of indexing fixture in order that the various slots may be ent in their proper relations to each other. The illustration shows the method of holding used for this fixture when applied to a Pratt & Whitney spline-milling machine. The fixture base is fastened to the milling machine table by means of bolts through the slot, C, at each end of the fixture, and is aligned by means of keys entering the table T-slot. The method of locating the work on this fixture is out of the ordinary, and is therefore worthy of a detailed description. The two shafts, shown at D and E, are laid on the finished surface of the fixture. They are held by the elamp, F, the angular portion of which grips and pulls in on the cylindrical part of each shaft. As the clamp screw is set up, the two shafts approach each other until they strike against the finished surfaces or dioulders on two inserted pieces, 0 and H, which locate and align the work. The first cut on the key- ways is made with the pieces set in the position shown, after which the clamp is released sufficiently to permit the two shafts to be turned with the slot downward. A positive method of locating from the first slot which has been cut is provided in the bed of the fixture; and as the shaft is revolved after the first cut and stands with the slot downward on the fixture, this locater engages with the slot and gives positive location. The locaters are controlled by the set^serews, L. MXTUBSS FOB CONTINUOUS miJBBB 163 It will be seen that a repetition of the indexing process will produce the four slots at 90 degrees from each other without the need of expensive fix- tures ordinarily used for this work. Other examples of spline-milling fixtures will be given, but as they are usually of a simple form which can be made up at minimum expense, it is unnecessary to go into the matter more completely here. CHAPTER XII FACE-PLATE FIXTURES J ljttii i Mi for Singfe Ptoim— tlie general process of manufacturing, and also in tool-making, many pieces of work to be machined on an engine or tur- ret lathe cannot be satisfactorily held in any of the Yarions forms of chneks previously described. For such cases either a face-plate of standafd form is nsed, as that shown in Figure 70, or, if a number of pieces are to be maehinedi a special face-plate with suitable lugs and clamps may be made up. When required for toolmaking, or for a single piece of work, the standard style of face-plate in Figure 70 is commonly employed. This type is made of cast iron and is screwed to the end of the spindle of the machine. If the toolmaker has a certain piece of work to bore, and the work is of such size that it can be clamped upon the face-plate, he would set up the work against the face of the plate, A, and apply suitable clamps through several of the slotted holes, B, so that the work could be held in the desired posi- tion for machining the hole. In setting up a piece of work of this kind he would use an indicator on the work to determine when it was in the correct position for machining. The T-dlotSi C, em be used m FACE-PLATi; FIXTUBMS 165 Y c m. 70. mmBAXD wace plate wm ah mmm lathe both to hold the work and to fix steel blocks in cer- tain locations on the face of the plate when several pieces of the same kind are to be machined. Such a face-plate is seldom used in general manufacturing except for the work just described. Fixtures for Quantity Production.— We now come to the class of manufacturing known as quantity pro- duction, where many pieces of the same kind are produced. If a number of pieces are to be machined, it is obvious that the face-plate fixtures to be used can be made up with quick clamping attachments which require a minimum amount of time and labor to set up. They can also be made with simple clamp- ing arrangements which answer every purpose for holding the work but which take a little longer in setting up. The latter fixtures are, of course, some- what cheaper than the more elaborate, and if the output is to be comparatively low, they will answer every purpose. TOOLS AND PATT£ENH no. 71. TWO muptM fage-flatb fixtubis The fixture. A, Figure 71, is sbown holding the work, B, a flanged collar which has pre¥ionsly been machined on its inside surface, C. As it is neces- sary to cut out the recessed portion, D, of the collar in a subsequent operation, the work is located on the stud, E, and is clamped in place on the locating stud against the face of the fixture by means of the clamps, F, three in number arranged equidistantly on the face of the plate. In a fixture of this kind the revolution of the work around the axis of the spindle, G, is perfectly true, so that when the recess, D, is cut it will be concentric with the previously machined surface, C. Fixtures for Cutting Packing Bings.— The other example of a face-plate fixture, H, Figure 71, is de- signed to handle a nng pot, K, from which packing rings are to be cut The ring pot has previously been faced on the end shown against the face-plate and three holes have been drilled in the flange for locating and driving purposes. The work is set up FACE-PLATE FIXTURES 167 on the face-plate fixture, locating on the pins, L, one of which is shown in the illustration. The work is clamped back against the face of the fixture by means of three hook bolts, M, having an angular end which engages with the angular flange at N, thus holding the work back firmly against the face of the plate. This face-plate is provided with a bushing, O, in which the pilot, P, of the boring bar is guided. The boring bar is used to bore out the inside of the pot, as indicated. When a number of packing rings are to be made up a fixture of this kind can be used to advantage or the flange of the pot can be made so that it can be gripped in chuck jaws of special form. The latter method is more common at present and is superior to that shown, due to the fact that no pre- liminary operation is necesary on the work before this machining operation. Face-Plate Fixture for a Hub Plange.— The face- plate fixture shown in Figure 72 is somewhat similar to that noted at A, in Figure 71; but in this case the work is located by an outside surface which also has been previously machined, shown at A in this illustration. The face-plate, B, is screwed to the end of the spindle as indicated, and is recessed to allow the shoulder. A, to fit into it, thus giving the correct location. The flange, C, has been drilled in several places, as indicated at D, and these drilled holes are used for driving against the pressure of the cut, by means of the pins indicated. The clamps, E, three in number, hold the work back against the face of the plate, and are slotted to allow them to be drawn off the flange when setting or removing the work 168 TOOLS AND PATTERNS m. 72. FAGE-PIATE FIXTURE FOR A HUB FLANGE from the fixture. The coiled springs, F, are pro- vided in order that the clamps will always stand away from the work when it is being placed in position. Fixtures of this kind, largely used in the general process of manufacture, can be adapted to many kinds of turret lathe work. Self-Oentering Fixture for a Rough Casting.— It is sometimes desirable to machine a piece of work, a ring pot, for instance, whose, shape is such that it is not readily held in chuck jaws. A fixture for this purpose is shown at A, Figure 73. The casting, B, is somewhat thin in section, and is to be bored and turned by means of the tools, C and D. As no previous machining has been done on the casting, it is necessary to center it from the rough surface in some way and to clamp it firmly on the fixture. For the purpose of centering the work, a spring tapered plug, E, is located in the fixture in such a FAGE-PLATE FIXTURES 169 wo. 73. SECTION THROUGH A SELF-CENTERING FIXTURE FOR A RING POT way that it automatically centers the work from the inside. The spring at the base of the plug permits the clamps, F, to be tightened down upon the face of the flange, so as to grip the work securely. While the spring plunger centers the work, it does not in any way prevent the tightening of the clamps, and also it is bored out and ground to the size of the pilot, G, of the boring bar in which the cutter, D, is located. The principle used in this fixture can be applied to a variety of work on turret lathes and boring mills. Fixture for Thin Aluminum Castings.— The in- stances which have been previously noted have all been pieces of cylindrical section, but it frequently 170 TOOLS AND PATTERNS no. 74. FACE-PLATE FIXTURE FOR A THIN ALUMINUM CASTING happens that the work which is to be machined is of irregular form requiring special arrangements for locating and holding it One point in the design of faee-plate fixtures for such work, is that the piece shall be held in such a way that it will be firmly secured and will not be distorted in any way by im- perfect clamping. An example is shown in Figure 74, where the work is an aluminum casting, A, of more or less rectangular shape. The V-prineiple, so-called, in locating work on fix- tures of Tarions kinds, is based on the fact that a piece of work can be put into a V-shaped block or its equivalent in such a way as to act as a locater whether the piece is a rough casting or one that has previously been machined. It might almost be said that the basic principle of jig and fixture design is that Qf locating by means of a form that resembles tlie FAOl-PIiATl FIXTUBIS capital letter V — ^generally written, vee. This vee form is often obtained by means of a series of pins arranged in proper formation to receive the work. In the instance noted in Figure 74, the work. A, is placed on the fixture^ B, in such a way that it locates against the fixed steel pins, C, on one side of the fixture and the pin, D, on the other which form a sort of vee. The work is forced over against the pin, D, in one direction by means of the screw, E; while the location in the other direction is performed by means of the swinging clamp, F, operated by the hollow set-screws, G. It will be seen that the swing- ing clamps, F, have a knife edge and that the locat- ing pins at C and D are similarly arranged. The purpose of this arrangement is to sink these clamps and pins into the surface of the casting slightly, so as to keep it from being pulled out while the piece is being machined. As the bottom of the casting is also rough, it must also be supported, so that the work will not be pushed inward toward the face of the fixture by the pressure of the cut. This is taken care of by means of the spring pins, H, which adapt themselves to the rough surface of the casting and are firmly locked in position by the set-screws, K, in the outer rim of the face-plate. In addition to the spring pins, H, the work is given a positive location on the fixed pins, N, at three comers of the piece. The work which was done upon this casting after it was located and clamped, was the facing of the surface, L, the turning and sizing of the interrupted circular tongue, M, and the boring and reaming of the center hole with the reamer, 0. The machine on 172 TOOLS AND PATTBMNS Wa. 75. PL.AN AND SECTION OF A FIXTURE WITH SAFEGUARDING DEVICES which •this work was done was a horizontal turret lathe, and the equipment for producing the work was of a special nature. The principles shown in this fixture may he applied to other examples of turret lathe work. Fixture for an Irregular Bracket. — The protection of workmen engaged in manufacturing is often neglected in the design of fixtures for turret lathe work and other work that requires similar handling. It should be the purpose of every designer to make any fixture upon which he is engaged so that it will be impossible for a workman to become injured by it. It happens occasionally that a piece of work w'th projecting arms or lugs is to be held on a face-pi ate fixture, and when such cases of this kind arise the designer should exercise the greatest care to make the fixture in such a way that the workman will be protected from these projections as they revolve. An example of this kind is shown in the piece of FACE-PI4ATE FIXTURES 173 work, A, in Figure 75. This piece has been previously machined by milling the surface, B, and cutting the tongue, C. It will be seen that the bracket has three projecting arms, D, which, if unprotected, might strike a workman when machining the piece. The fix- ture, therefore, is made up with a protecting rim, B, of such height that the arms do not extend beyond it. The extra cost of making a fixture like this is very slight, and in addition to the safety feature, the rim, E, also acts as a counterpoise and makes the fixture run more smoothly. The work is located on the fixture against the fin- ished pads, D, and the tongue, C, lies in a groove provided for it. The work is clamped by means of the four straps, F, which are slotted so that they can be moved back to allow the work to be set up and removed. As in the preceding instance, the body of the fixture, G, is screwed to the nose of the spindle, as indicated. The work to be done in this case is the boring of the hole, H. This work is performed by means of the tool, K, mounted on a bar whose forward end is piloted by a bushing, L, in the face- plate fixture. This method of piloting a boring tool or other cutting tool assists greatly in producing ac- curate work, as the bushing acts as a guide for the bar and keeps it always in a certain relation to the work. Counterbalaaoed Fixture for a Conneetiiig Bod.— For a piece of work that is very much off center and is to be bored or otherwise machined at high speed, it is often necessary to provide a counter- balance on the fixture in order to prevent excessive 174 TOOLS AND PATTSBNS WKL 7i. CXnTHfEBBALAKCED FAGE-FL4TB fIXTUBE VOS A CONKEGTINQ BOD vibration from the unevenly balanced rotation of the work and fixture. An example is shown in Figure 76. The fixture here is designed for boring and ream- ing the hole, A, in the connecting rod, B. The con- necting rod has been previously drilled and reamed at the small end, C, and it is necessary to locate it for the remaining operation in such a way that the hole, A, will be in a fixed relation to the previously reamed hole, C. The face-plate fixture, therefore, is ' made np with a stnd on which the portion, C, locates. This portion of the work is drawn back against the face of the fixture by means of a nut. The large end is then correctly located by means of a V-block, D, which eratm the boss at C. This V-block is under ent, as indicated in the sectional view, so that it tends to draw the work back against the face of the plate, when it is then set up by means of the screw, K This screw is monnted in a swinging latch and PACB-PLATB FIXTURES 175 can be thrown back to allow the workman to hook his finger into the recess, F, and pull the block away from the work. As the fixture is considerably heavier on one side than on the other, provision is made for counter- balancing it by means of the Ings, G. These Ings are a part of the cast-iron face-plate and are made heavy enough and thick enough to more than balance the mechanism on the opposite side of the fixture. • In balancing a fixture of this kind, the work is placed in position and all clamps are set up as if the machining was about to be done. The fixture is then placed on an arbor and allowed to swing as it will. Naturally, the heaviest portion will hang down- ward. The workman then drills out a portion of the stock from the lug, as indicated by the holes, K, and tests the fixture again, continuing the operation until a proper balance is obtained. Sometimes so much stock has been added as a counterbalance that it becomes necessary to mill off a portion of the eounterpoise in order to bring the fixture into balance. Fixture with Adjustable Counterbalance. — A fix- ture for turret lathe work or for the engine lathe may be needed which will enable several pieces of similar character to be machined upon it by making slight modifications. An irregularly-shaped piece of work which has a counterbalanced portion, will per- mit the counterbalance to be shifted radially on the plate so that it will balance whatever piece is being held upon it. An example of this fixture is shown in Figure 77. If § TOOLS AND PATTERNS mi. Ti. SEcnoK and plan of a fixture with adjustable COUNTERBALANCE The work in this case is a worm-gear sector, A, which has been previously bored and reamed at B, and now is to be machined as indicated at C. The work 18 located m a fixed stud at the center of the fixtnre, and is clamped back against the finished pad by means of the nut, E. A **C-washer," F, is used with the nut so as to permit the work to be ranoYed rapidly. By using such a device it will be seen that the nut can be slightly loosened, the C- washer slipped out through the slot, and the work immediately released without removing the nut, E. In order to provide the portion of the work, C, with a rigid support, it is swung around against the stop pin, H, and is clamped by the screw, K. As this ride of the fixture, then, is so much heavier than the other, it is necessary to provide a counter balance at L. This counterbalance is in the form of a segmental block with two bolts through it, as indi- cated at M, which pass through the two slots, and FACE-PLATE FIXTURES 177 ullow the counterbalance to be radially adjusted to compensate for pieces of different size. An applica- tion of this principle of a movable counterbalance can be made to many types of lathes, turret lathes, and other machines of similar character. In cases where the work to be machined is of comparatively large diameter, so that the work runs at slow speed, it is not usually necessary to counterbalance it. Eccentric Fixture for a Ring Pot.— In making up packing rings for automobile motors, compressors, and the like, an eccentric ring is frequently desir- able. The ordinary process of machining one of these is by means of an eccentric turning device which will be described in Chapter XIV. As an eccentric device of the character mentioned is some- what expensive, however, the small manufacturer frequently dispenses with such a device and handles the work in a slightly different manner. But when the device is employed, the work is turned eccen- trically by means of the device and is also bored concentrically at the same time, thus saving a con- siderable amount of time in the process. When an attachment of the kind mentioned is not Bsed, it is customary to bore the work in one opera- tion. The outside eccentric is then turned in an- other operation, either by means of an eccentric arbor or by placing the pot from which the rings are to be made on a fixture which can be set eccentrically after the hole has been bored. In Figure 78, the ring pot. A, is located on the face of the fixture by means of the lugs and clamps shown at B. The face-plate consists of two parts, one of 178 TOOLS AND PATTERNS 110.78. TOCENTiaC FmiTRB ItIR A RINO POT which, C, is screwed to the end of the spindle, and the other, D, is fastened to it by means of the bolts, B, which enter slotted holes in the plate, D, to allow for a slight movement of the upper plate on the lower. The plate, C, is grooved at F, directly across its face; and the plate, D, is provided with a tongue to slide in this groove. In operation, the hole, G, is first bored by a boring bar piloted in the bushing, H, in the movable plate. After this operation has been done, the nnts at £ are loosened and the plate is set over the amount indi- cated by the line at K. The correct distance is de- termined by pins and bushings at L and M. This type of eccentric fixture is very simple and answers all purposes for work of this character. It is unnecessary to counterbalance the fixture unless the eccentricity is so great that the fixture runs out of balance when it is set over. Swinging Eocmtric Fizlnre.— A fixture may be required that will permit a slight amount of adjust- ment so that it can be set to give two or three eccen- FACE-PLATE FIXTUEEg 179 FOR A PACKINO MNQ POT tricities. In order to provide for a contingency such as this it is necessary to make the fixture so that the stops which limit the throw of the eccentric are adjustable. An example of such a fixture is shown at A, Figure 79. The fixture is designed for a hori- zontal turret lathe for boring and turning eccen- trically the worki B. The ring pot, B, which is to be turned and bored, is held on the plate, C, in practically the same way as the pot shown in the previous illustration. The mounting of the plate on the body of the fixture, however, is arranged in a different way. In this case, the plate is pivoted so as to swing from the stud, D. The lower portion of the body plate. A, is provided with a stop ex- tending out through a slot in the plate, as indicated at E. Adjusting screws, F, on the surface of the fixture at E, provide for lateral movement of the plate, and suitable clamping bolts, G, on each side of the fixture hold it in place. When it is desired to set over the work to produce the eccentric, the bolts, G, are loosened and the plate 180 TOOLS AND PATTERNS swung over until the stud, E, strikes against the set- screws, F, The amount which these set-screws per- mit the plate to move, govern the amount of eccen- tricity. The spacing of the stop, E, is twice the distance from the pivot point, D, to the center of the work, so that the apmuBt of movement at F is exactly twice the eccentricity produced. Fixtures of this kind can be used with success on a great variety of work, and as they are cheaply made and very serviceable they may be considered as excellent types of eccentric turning and boring equipment CHAPTER XIII ABBOBS AND MANDRELS Definition of Terms. — The term arbor is applied to the cylindrical piece used for mounting cutters upon a milling machine. It is also applied to the device used to center a piece of work by a previously bored or reamed hole so as to bear a distinct relation to the hole. The term mandrel is almost sjmonynious with the term arbor as applied to holding work. For example, the expressions, **an arbor for a %-inch hole," or **a mandrel for a %-inch hole," are used interchangeably. The term mandrel, however, is not used synonymously with the term arbor when applied to the device for holding cutters in a milling ma- chine. These would always be referred to as cut- ter arbors.'* AYbors are of several kinds — ^plain arbors, threaded arbors, expanding arbors, and cutter arbors. The last mentioned is generally used in the milling ma- chine for holding om or more cutters in position. This type of arbor is quite simple and is variously made as a part of the standard equipment for a mill- ing machine. Such an arbor is shown in Figure 80 at A. The tang end, B, is tapered to fit the milling machine spindle, and may be used in an adapter when the spindle taper and that of the arbor do not ISl m TOOLS AND PATTERNS 1— e-M MG. 80. ABBOB FOE MILUNG MACHINE, ABOVE, AND VOR PliAIN LATHE, BELOW m-1 ■ na. SL EXPANDING SHOB T¥FB €P AIDOfI W. H. Nldwlflon ft Oa ARBORS AND MANDRELS 183 correspond. The cutters, C, are placed on the arbor with one or more spacing collars, D, between them to space the distance, B, correctly for the work re- quired. There is little to be said about milling ma- chine arbors as their design is so extremely simple. A plain arbor or mandrel, indicated at F, Figure 80, is usually found in the tool crib in all standard sizes. It is made up for standard sizes of holes, usually with a taper of about 0.006 inch per inch of length. When a piece of work, such as that shown at G, is to be turned on its surface by the tool, H, after it has been reamed in a previous operation, it is placed under an arbor press and the arbor, F, is forced into it under pressure. As the arbor is tapered, it will wedge firmly into the work so that there will be no slipping when the pressure of the cut is applied. Arbors of this kind are usually de- signed to be dogged to the face-plate, as indicated in the drawing. Arbor with Expanding Shoes.— It is often neces- sary to hold a piece of work that is slightly over or under a standard size on an arbor, to perform some operation upon the piece which will be absolutely concentric with a previously finished hole. Two methods of holding are possible. The toolmaker or machinist can make up, in comparatively short time, such an arbor as that shown in i'igure 80, of such a size as to suit the hole in the work. Or, if the tool crib is well equipped with expanding arbors, it may not be necessary to piake up a special one for the job. Expanding arbors are of several types, but perhaps m TOOLS AND PATTEBNS the most useful type is that shown in Figure 81. Such an arbor can be purchased in Yarious sizes to suit any given eonditions. The body of the arbor is hardened and ground to cylindrical form. It is furnished with four slots, A, into which are fitted the shoes, 3. It will be noticed that the slots are cut on a slight longitudinal taper, so that when a piece of work is placed on the shoes, they may be adjusted along the tapered slots to the required diameter. The retaining ring, C, at each end of the shoes are slotted to receive the shoes and hold them on the arbor when not in use. This type of expand- ing arbor should form a part of the tool crib equips ment and should be bought in a sufficient range of sizes to cover the requirements of the class of work which is being done. This same type is also largely used in general manufacturing, and its adaptability suits it for an. infinite number of pieces. Sidit ting Ezpandiiig Arbor.— It is sometimes nec- essary to refinish the outside of a piece of work and make sure that it is absolutely concentric with the center of the hole that has been previously machined. A common type of arbor for this purpose is shown in Figure 82 at A. Let it be supposed that the work, B, is to be held by the hole previously finished in it, and that the work is to done on an engine lathe. A steel arbor, C, is then made up with a slight taper along its length. A sleeve, D, is split along its length at E, and is tapered on the inside so as to fit the taper on the arbor, C. When the work, B, is placed in position and forced onto the arbor over the split ring, the ring expands slightly as it is forced up on AKBOBS AND MANDRELS 185 ■ no. 82. SPUT-RING EXPANDING ABBORS the taper until it grips the work securely, thus hold- ing it so that it can be machined readily. ' This type of arbor is not exceptionally good, as it is simply split longitudinally. When it opens up, the ring, D, therefore, is slightly elliptical and does not expand evenly all over. As a cheap arbor that can be used for a few pieces, such a device will answer the pur- pose in many instances, but it should not be used for work requiring great accuracy. A much better type of arbor, shown at F, can be used for work requiring great accuracy. Roughly, the principle of the two arbors is the same, except that in the instance previously mentioned the ring split in one direction only, while in the example, ^, the ring, G, is split longitudinally into three slots, running from one almost to the other and spaced 120 degrees apart, as indicated at H. There are also 186 TOOLS AND PATTERNS three other slots starting from the other end of the ring, spaced equidistantly between the slots men- tioned, and also running nearly to the end of the ring. It will be seen that this arrangement allows the ring to be expanded equally all over, making a mueh better eonstmetion than that previously described. An additional requirement on this arbor is seen in the nut, K, and washer, L, by means of which the ring is forced back on the taper, M, so that it expands and holds the work. In the example shown at A, it is necessary to use an arbor press to force the work on, or else to drive it on with a piece of babbitt or wood. For finishing the outside of collars, small blanks, and other work of similar character, the type of arbor shown at F is very useful, and is fre- quently found among the tools used for general manufacturing. Expanding Arbor for an Automobile Flange.— Special arbors may be made up to suit a particular case when a number of pieces are to be manufac- tured. One such is shawn in Kgure 83. In this case the work, A, is an automobile flange which has been previously bored and reamed at B and C. As it is necessary to finish the end, D, and the flange, E, the method of holding by the inside surface was devised. The machine to which this arbor was applied is a horizontal turret lathe. The method of holding was by means of the collet mechanism with which the turret lathe is furnished, the stem of the arbor, F, being held as indicated in exactly the same ABBOBS AND MAllHI^' 187 ilO. 83. SECTION TmiOUGH EXPANDINa AJSBOB FOB MM AUTOMOBUfE FLANGE manner as that used to hold a piece of bar stock. The work then was placed on the portion, G, which made a nice fit at this point. After the work was so placed, the tupered screw, H, was set up, thus expanding or opening up the arbor to grip the points, C. A shoulder was also provided on the arbor to give longitudinal location at K. When making use of the collet mechanism to hold an arbor for manufacturing purposes, it is necessary to make sure that the collet is perfectly true; other- wise the arbor might run out of truth and work naight be produced which would not be concentric. An arbor of this kind must be made of tool steel, tempered slightly in order that it may expand prop- erly and come back to place again when the tapered screw is released. It will be understood that the i 188 TOOLS AND PATTKRNS portion of the arbor whieh is controlled by the ex- pansion of the tapered screw, is slotted into three sections, so that it can be opened up slightly by the action of the screw mentioned. KYpandlng Axboir for an Adjuiting Nut— Occa- sionally several pieces of similar character but slightly different in size may be machined by the same or similar equipment on a turret lathe. An example is shown in the pieces A and Figure 84. These pieces are bronze adjusting nuts in two sizes, slightly different both in outside diameter and in the location of the spanner holes shown at C. Several thousands of these parts were to be made, and as it was desirable to make up the equipment as cheaply as possible, the arbor was so designed that it could be used for both pieces by the aid of an adapter. *A special nose piece, was screwed to the end of the spindle, as indicated, shouldered at E to receive the ring, F, which was used for the piece, A, and also could be fitted with the ring, 6, for use with the piece, B. In each case the rings were provided with pins, H and K. These pins entered the spanner holes, as indicated, and assisted in driving the work-an essential point in connection with an arbor on whieh any heavy work is to be done. The outside of the nut in each case was to be threaded with an opening die, so that the pulling action of the cut was rather severe. A split ring, similar to the one shown at G, Figure 82, was used to center the work. This ring, of course, was very much smaller than the one previously nien- tionedy but the method of splitting was the same. ABBORS AND MANDRELS 189 p WO. 84. IZPAKniNO ARBOB FOB AN ADJtJSTINQ NUT In this arbor, it will be observed, expansion was procured by means of the tapered plug, L, which had a generous bearing, M, in the nose piece. The threaded portion, N, was somewhat loose in order that the centering action might not be governed by the threaded portion, but might be absolutely de- termined by the cylindrical part, M. The thread was sunply used as a means of drawing in on the plug and thus expanding the ring at L. Applications of this principle may be made to many kinds of narrow work when it is necessary to do heavy cutting on the outside. It occasionally happens that one or more holes are drilled in a piece of work in order to provide a means of driving. In the particular case mentioned, the spanner holes, fortunately, made this unnecessary. Expaadingr Arbor for a Bevel Pinion.— It is par- ticularly necessary to machine a bevel pinion in such 190 TOOLS AND PATTERNS IW. 85. 8SCni»f THROUGH BXPANDINO SHOE ARBOR FOR A BBVEKf FUnON a way that the outside of the gear is in perfect con- centricity with the hole. In order, therefore, to pro- vide a means by which snch an effect may be secured, it is necessary at times to design an arbor of small dimensions with adjustable features to provide for self-centering. Occasionally, also, the kind of tooling which is to be used on a piece of this kind has a certain effect on the design of the arbor. Such an instance is shown in Figure 85. This is an unnsual type of arbor for it is somewhat delicate in construction. Its mechanical features, however, are of considerable value, and the principle shown may be applied to other work of similar character. This arbor was made np for use on a horizontal turret lathe in connection with a special taper at- tachment for generating the angular surface of the pinion, A, which had previously been bored and reamed on another machine. At the same setting of the work, the face, B, was to be machined. Pre- ARBORS AND MANDRELS 191 vious to the operation shown and after the hole had been reamed, a keyway, C, was cut in the pinion in order to provide an efficient means of driving while the heavy cutting was taking place at A. The spindle of the machine was provided with an adapter, D, which had a tapered hole, E, where the stem, F, of the arbor was located. A key driver, G, was also added to make the driving positively certain. As will be seen from the illustration the work located on the cylindrical surface, H, which was made 0.002 of an inch under the size of the hole in the pinion. There are three slots cut in the arbor to receive the shoes, K, which were beveled slightly on their internal faces so as to fit the taper on the oper- ating rod, L. This operating rod was pushed back mto the arbor by means of the screw, M. The por- tion, N, is ground to fit a shell mill held in the tur- ret and used for facing the angular surface, B. As the operating rod was pushed inward by means of the screw, M, the three shoes, K, were forced out- ward against the inside of the hole in the pinion, thus providing an efficient centering action. A sec- tional view, taken directly across the arbor and is shown at 0, and a correspond- ing section of the operating rod is indicated at P. Although an arbor of this kind is fairly exgMlMve and rather delicate in its construction, it may be used in a number of cases where the greatest accu- i*acy is necessary. The equipment mentioned is really the '^ast word" in the design of an accurate expanding arbor. An additional refinement is found ^ the knurled nut, Q, which is used to start the TOOLS AND pj^ffEf^ work after it has been inachined in the event that it might stick slightly. Expanding Pin Chuck for a Kston.— Automobile pistons, A, Figure 86, and certain other classes of work, are made in such form that the inside portion is "cored.'* A core, if of large size, but not extend- ing completely through the work, always shows a tendency to sag more or less while the casting is made, so that the resulting work is not absolutely concentric. This is particularly true of automobile pistons. Therefore, such work must be held in such a way that wh^ it is machined on the outside, the surface will be very nearly concentric with the in- side rough-cored surface, no matter whether the cast- mg is true when in the rough state or not. It is logical to hold such work for the machining processes from the inside core, so as to be sure of the concentricity. This method of holding makes neces- sary a rather elaborate arbor. Arbors made for this purpose are of various forms, each having some par- ticular claim for its existence. The example shown in Figure 86 is one of the best for this class of work, and has been built to suit numerous cases with the most satisfactory results. It is by no means a cheap arbor, and it requires the greatest care in design and the most careful workmanship in machining. Yet its action is so satisfactory that in the event of a large number of pieces to be machined, the first cost of the arbor may almost be neglected. The arbor, shown at B, is screwed to the end of the spindle, as indicated. It is made of machine Steel, carbonized, hardened, and ground in its essen- ARBOBS AMD MANPBKLS Ida m, 86. PLAN AND SECTION OP EXPANDING PIN CHUCK FOR A PISTON tial parts. Six pins are so spaced as to be equi- distant around the periphery, at C, while at D they are arranged in such a way as not to interfere with the wrist pin bosses shown in the upper sectional view at E. The lower ends of the pins are beveled to ride on the two cams, F and G. These cams are threaded right and left hand to fit the screw, H, which is provided with a slot, K, for operating pur* poses — ^a pair of bevel pinions, at L and M, being used as the operating means. It will be seen that when the pinion, L, is revolved by means of a special socket wrench, the motion is transferred to the IM TOOLS AND PATTERNS pimon, M, which turns the threaded shaft, H, and causes the cams, F and G, to approach or recede from each other according to tie direction of rota- tion. A valuable point in connection with this piece of mechanism is the fact that the pressure exerted on the pins C and D is eqnaHzed, so that the amount of force exerted on all six pins is the same. This equalizing action is caused by the * Afloat" in the two cams. As the shaft, H, is free to move slightly longitudinally, the pressure is distributed on the two cams in an equal ratio. The cams are prevented from turning by means of the set-screws, 0. Threaded and Knock-off Arbors.— Tapping out a piece of work in such a way that the threaded por- tion will be in perfect concentricity with the out- side and with the ends of the work, is a difficult oper- ation. It is, therefore, necessary to provide some means of re-finishing the outside of the work or the ends, using the threaded portion as a locating point. The simplest type of arbor which can be devised for holding a piece of threaded work is that shown at A, Figure 87. In this arbor a portion, B, is threaded to receive the work, which is screwed upon it and makes up against the shoulder, D. This arbor is held on centers in an engine lathe and is driven by means of a dog in the usual man ner. While it will give satisfactory results, it is by no means a convenient type to use, for the reason that the pressure of the cut in finishing the outside of the work is such that it causes the piece to **freeze'' up against the shoulder, D, so that it is AlBORS Am MANDRELS 195 KEG. 87. THRSADED AND KHOGK-OFF ARBORS difficult to remove it without the use of a pipe wrench or special clamps. A much better type of arbor and one which over- comes this trouble, is shown at E in the lower illus- tration. This arbor is threaded in the same manner as the upper one in Figure 87, except that the work, F, does not make up against the shoulder, G, but rather against the flange, H. This flange, however, fits against a shoulder, K, on the arbor, so that the longitudinal location of the work always comes the same. Provision for removing the work without difficulty is as follows: The arbor is threaded, at L, with a 196 TOOLS AND PATTERNS coarse left-hand thread on which the flange, H, is screwed until it strikes against the shoulder, K. The flange is provided with two lugs, M, on opposite sides m order to make the matter of releasing easy. When the work has been finished, it is only necessary to strike either of these lugs a sharp blow with a bab- bitt hammer or piece of wood and the work is at once released, because the end of the work is backed away from the flange, H. It is an easy matter, then, to release the jriece from the arbor without the aid of any tools except the workman's hands. Knock-oflf Arbor for Threaded Collars.— An excel- lent example of a knock-off arbor designed for handling a number of pieces of threaded work of different sized threads and pitches is shown in Figure 88. There were a number of collars such as those shown at A, B, and C; the manufacturing require- ments of which made it necessary to have the ends square with the thread. An equipment was designed, therefore, so that by means of adapters, such as those shown at D, E, and F, and with threaded 'arbors as that shown tft G, a number of different sizes could be handled with little trouble. A master bushing, H, was inserted in the spindle of a turret lathe, as indicated. In it the adapters, G, were located by means of the taper at K, and were drawn by a bolt, L, provided with a spherical washer, M, in order to equalize any strain caused by the action of the bolts m drawing the work back into the taper, K. The master bushing was provided with a threaded por- tion, N, and a shoulder, 0, against which a plate, P, gave the correct location to the work. The threaded ARBOES AND MANDRELS 197 m. 88. KHOCK-OTF ARBCm im *mEEAllED OOU4ABS portion was made left hand, as in the preceding instance. A knock-off flange, Q, was made with a finished pad, E, so that a spacing collar, F, could be used in connection with the work. In operation, the threaded flange is screwed .up 'Jntil it makes against the shoulder at 0; the spacer, P. is inserted, and the work, C, is screwed onto the arbor. Then, after the machining has been *e lugs, S, are given a sharp blow with the hammer or a block of wood, and the work is immediately TOOIiS AND PATTEBMS released so that it can be removed from the arbor. I nlllll up an equipment of this kind to handle twelve pieces of different diameters and different threads, and its operation was very satisfactory. Moreover, the same principle may be applied in many other cases where threaded work is to be machined. Special Arbor for an Eccentric Packing Sing.— The packing ring, shown at A, Mgnre 89, is a type commonly nsed for compressors and automobile motors. The operations on a ring of this kind are as follows: A pot casting is first made np and held in snch a way that it can be tnmed eccentrically and bored at the same time. In the same operation the rings are cut off from i/4-inch to %-inch wide. After they have been cut off they are ground to the correct thickness, and are then cut with a diagonal cut, as indicated at B, and from 5/32 to 3/16 of an inch of metal is taken off of each. When one of these rings is closed up so that the edges at B are in contact, it will be found that the ring is slightly elliptical. To counteract this ellipse and to make the ring true once more, it must be turned or ground on the outside. A special arbor of an unusual type is used for this purpose, the con- struction being practically the same whether it is used for turning or grinding. The arbor, C, is ar- ranged so that it can be dogged at one end and held on centers in an engine lathe or on a cylindrical grinder. A locating flange, D, and a sliding sleeve, E. fit snugly on the portion, C. The particular type of arbor shown in this illus- tration is intended to take two packing rings, F. AEBOBS AND MANDBELS 199 Wm, 89. SPECIAL ABBOR FOR AN ECCENTRIC PACKING KINO These are held firmly against the shoulder by means of the threaded piece, G, which is hexagonal so that a wrench can be used upon it. In using this arbor, the hexagonal nut, H, is removed and the rings, F, are set into the sleeve; the threaded nut is then screwed up upon them until they are firmly held against the shoulders at D. The sliding sleeve is now pulled back out of the way, until the detent pin, K, snaps into the groove, L, which keeps it out of the way of the tool while the work is being done. An air hole is provided at M, in order to relieve the suction and allow the sleeve to be pushed* back away from the work without difficulty. Were it not for this provision it would be practically impossible to pull back the sleeve. Arbors of this kind are in very common use in automobile factories throughout the country. Prac- tically all are made on the same general style, al- though refinements are sometimes found tending toward more rapid manipulation and quicker hand- ling. However, the type shown is an excellent ex- ample of an arbor for work of this character. 4 CHAPTBB XIV GENERATING AND FOEMING ATTACHMENT Generating Curved Surfaoes.— A cylindrical piece of work may be formed to a prescribed shape by means of a tool itself shaped to the correct contour, or the shape may be generated by a single tool nsed with a special attachment on an engine lathe, a turret tathe, or a vertical boring mill. If the work to be formed is not cylindrical, a suitable forming attach- ment can be applied either to a planer, a shaper, or a millmg machine in sueh a way as to produce the desired shape, either with a cutter of special form or with a forming plate that controls the move- ment of the cutting tool. Attachmente for the planer, shaper, and milling machme are rarely nsed, except on special work, and as they are highly specialized and the design is gen- erally developed to suit the particular pieces to be machmed, it is not necessary to describe them here. For some very large work, a radial attachment can be applied to a planer and used to generate a curved surface. It is also possible to apply a taper attachment to a planer, but this is not usual as the work can frequently be set at such an angle that tlie tapered surface to be machined will be in the same plane as the top of the table. Spedal forms can be aoo GBNBBATING AND FOEMINa ATTACHMENTS 201 • machined on a planer by means of a forming attach- ment which controls the movement of the tool on the rail. In milling machine work it is seldom that an attachment to produce contours is required. The form of the piece to be milled can be easily generated on a profiler by suitable forming plates. It is en- tirely possible, however, to generate simple forms on a milling machine by the application of a proper fixture and a suitable forming plate. These several machined are so seldom used for forming that we have only the proposition of forming as applied to the engine lathe, turret lathe, and vertical boring mill to consider. Therefore, as these three machines are most commonly used for work of a cylindrical nature, the attachments described are particularly applicable to this class. Simple Radius Generating Attachment.— The en- gine lathe is frequently used either by the applica- tion of a forming attachment at the back of the lathe or by some special arrangement applied in a suitable manner. The construction of any such attachment depends somewhat upon the work to be machined. Standard forming attachments applied to the rear of the machine can be obtained from manufacturers of certain engine lathes; but as these attachments are generally designed to operate longitudinally along the work, other arrangements are necessary when it is desired to generate a form on the end of a cylindrical piece. An example of the latter is shown in Figure 90, where an arrangement for generating a radius on the end of the piston is seen at A. It will be noticed 202 TOOLS AND PATTEfiNS - D o that tbe end of the work is formed to a perfect radius, and also that the surface is so large that it could not properly be formed with a single tool. The application of the attachment to the lathe made it possible to generate the radius shown in a short time; furthermore the attachment itself was compar- GENERATING AND FOEMING ATTACHMENTS 203 atively inexpensive. The design was such that con- siderable flexibility was possible, both in the length of the radius and in its position with relation to the center of the spindle. The construction of the attachment is simple; a special block, B, is supplied with a swivel top, C, the upper part of which was dovetailed at D. The tool-block, L, was furnished with a tool, E, for cut- tmg the correct form. A special form of bracket, F, is fastened to the carriage as indicated, and a T-slot, G, is cut in it to provide for transverse adjustment of the pivot, H. The arm, K, swings on this pivot, and is attached to the tool-block, L. Thus it will be seen that as the cross feed of the carriage is operated, the tool, E, will be constrained to follow the path indicated by the dotted line, M; except that it can be moved radially as permitted in the tool- block so as to obtain radii of different lengths, if desired, and also to compensate for re-grinding the tool when it becomes worn. The attachment shown was designed by me a num- ber of years ago for an automobile plant in Massa- chusetts, and since that time I have used the same idea in several other cases to good advantage. The principal value of this attachment is that it can be made up so cheaply. In addition, it does the work required of it with practically no attention on the part of the operator, and the results produced give excellent satisfaction. Kadins Forming Attachment for Gmwaisig Ptd- leys. — The ordinary cast-iron pulley, so largely used ^ machine work, has a crown" or radius on the 204 TOOLS AND PATTJBKNS face to which the belt is appUed, the purpose of which is to keep the belt from running off. The metal in the pulley at the point which is crowned IS usuaUy thin, and consequently cannot be formed with a wide tool of the proper shape to good advan- tage. In machining these surfaces it is therefore necessary to generate the form by means of a form- ing attachment. In the instance shown in Figure 91, the attachment was so made that two pulleys could be crowned at the same time with the two tools indicated at A in the upper part of the iUnstration. The work, B shown in the lower part of the figure, is held on an arbor, C, and driven by means of the driver, D, ex- tending through the face-plate and between the spokes of the pnUeys, as indicated. This attachment was apphed to an old-style lathe, and the necessary movement was imparted to the tool-block, E, by naeans of the rod, F, passing completely through to the back of the lathe as shown. A roller, Q, made contact with the forming plate, H, and was held in place by means of the spring, K. The bracket, L, was fastened to the back of the kthe carriage and was simply used to form a thrust surface for the spring. It wai be seen that as the carriage is trav ersed longitudinally, the two tools will follow the form indicated at H, thus generating the desired surface. If an engme lafhe is furnished with a forming attachment, work of the character shown in Figure 91 can be more easily handled by the application of a snitable forming plate to the forming slide at PIG. 91. PLiAN AND ELEVATION OF A RADIUS-FORMING ATTACH- MENT FOR CROWNING PULLEYS the rear of the machine. But the general construc- tion of attachments of this kind is similar to the one shown. Many varieties of forms can be generated % means of forming attachments on the engine 206 TOOLS AND PATTERNS lathe; it is only necessary to provide a plate to suit any given case. Piston Forming and Grooving Attachment.— As aitmniiMle pistons are produced in large lots, every effort is made to design the various tools used in the manufacture, so as to provide maximum produc- tion. And as the piston of an antomobile is a vital part of the motor, the greatest care is nsed in the mannfactore to insure uniformity and accuracy. Turret lathes are largely used for work of this character, and attachments are frequently applied for combining several operations in one. An excellent example of a forming attachment which is combined with two equipments for grooving the piston, is shown in Figure 92. A plan view looking down upon the machine is shown in order to make the manner of operation more apparent. The turret of the machine is used simultaneously with the tool shown in the plan view, but as the turret tools have nothing to do with the forming attachment, it would be confusing to show them here. The piston in this case is held on a special chuck, A, this chuck being somewhat similar to that de- scribed in Chapter Xm, Mgure 86. The work to be done is the forming of the ends of the piston, B, to the required radius, and simultaneously to make the annular grooves, C and D. In the first place, the cross-slide is furnished with a si>ecial block, dovetailed to receive the sliding member which is carried under the block that holds the grooving tool for tl^ surfaces C and D. The dovetailed slide, E, has a roller at F, which is guided GENEEATINa AND FORMING ATTACHMENTS 207 no. 92. FfSfOH lORMINO AND OlIOOVINO ATFACHMENT by the forming plate at G and H, so that the proper form is described on the end of the piston, B. It will be seen that as the cross-slide feed is engaged, the tool for turning the ends of the piston at B travels across the lathe carriage in the path directed by the forming plates. At the same time, the grooving tools are slowly moving forward, illitil they reach tho outside of the piston and begin to cut. At this time the operator changes the feed to a very slow one, so that the grooving tools cut only a little at a time and do not have any tendency to chatter. The feed for a cut of this kind on any kind of a job must be slow, to produce good results, as the cutting action of a grooving tool is not very good. 208 TOOLS AND PATTERNS It is obvious that any such equipment as the one described herewith would only be warranted when high production is desired. Attachments of this kind, however, are applicable to many varieties of work, and combinations of tools can be made to cover many different cases. The number of pieces to he machined must always be considered when designing any sort of special equipment, in order that the ex- pense may be proportional to the production. Angiilar Qfflwmting CroM-Slide.— For inishing the faces on large ring gears, the angular cut across the face of the gear usually requires a special forming attachment or special equipment of some character. It is entirely possible to machine work of this kind by means of a forming attachment similar to the one indicated in Figure 92, but, of course, it would be necessary to make the forming plates to the correct angle of the bevel on the face of the gear. A more convenient attachment for either an engine lathe or a turret lathe can be made up, as shown in figure d3. This is a special swivel cross-slide, and is designed to take the place of the regular cross- slide on the machine, which must be removed to allow the swivel slide to be put in position. The particular advantage of a cross^lide of this char- cater is that it can be swung radially about the cen- ter, A, to any angle within its capacity. The ring gear, shown at B in this instance, is to be machined along the face, C. The tool-block, D, on the swivel cross-slide is furnished with two tools, as indicated, for roughing and finishing this angular plate, which are set far enough apart so that the roughing tool GENERATING AND FORMING ATTACHMENTS 209 r K •B res rr-P u aQQaDQQQDaQQU 1 VIO^ d3. SPECIAL SWIVEL CBOSS-SLUIE Wm A TUREET LATHE completes its work before the finishing tool starts on the face of the gear. A swivel cross-slide is not by any means a cheap attachment, but its usefulness and flexibility is such that it can be used advantageously on many kinds of work requiring an angular generating device. Even though the attachment is rather expensive, the construction is simple and it is not likely to get out of order. The feed screw which operates the slide is controlled by a ]f>air of bevel pinions at the center which are always in mesh no matter what the angle of the slide may be. A suitable knock-off can be easily provided to stop the cutting action at any desired point. Eccentric Turning Device for Packing Bings.— ^^cking rings for automobile motors are frequently 210 TOOLS AND PATTERNS Wm. 04. ECCENTEIC TUBMINQ DEVICE WOB, PACKING RINGS made eccentric, and it is a decided advantage to be able to bore the inside of the ring and turn it eccen- tric at the same time. For this purpose, several manufaetiirers of turret lathes have developed equip- ment to apply to their own product. One such is shown in Figure 94— -the eccentric turning and bor- ing attachment for a turret' lathe, manufactured and patented by Pratt ft Whitney Co. The work, A, in the drawing, is held by chuck jaws, B, in a three-jawed gear scroll chuck, the face- plate of which forms a ring gear at C, and drives another gear of equal size, D. The latter gear is mounted on a shaft, splined at E, and carried by a GENERATING AND FORMING ATTACHMENTS 211 bracket, F, on the spindle cap of the machine. A supplementary bracket, G, is mounted on the turret and carries a slide, H, in which the tool, K, is mounted. This tool is used for turning the outside of the casting, A, eccentric to the inside. The slide, H, is held by the pressure of a stifif spring against a cam, shown at L. As the work revolves, the shaft on which the cam, L, is mounted revolves at exactly the same speed. And as the cam revolves, it bears against a small roller, M, mounted in the slide, so that it moves the tool, K, continually in and out to form an eccentric on the outside of the work. Simul- taneously with the turning of the outside of the pot, a boring bar, N, having a tool, 0, is used to bore the inside of the ring. Coincident with the action of the boring and turning tool, the tool-block, P, moves transversely, so that the gang of tools mounted on it cut off the packing rings one by one. This is J excellent example of the application of special attachments to a ttirret lathe, and indicates the possibilities of this class of machine in manu- facturing processes. Bevel Oenmtting Attachment for a Turret Lathe. — The possibilities of the horizontal turret lathe are little appreciated by the average manufacturer, and it is remarkable how poor a showing some of these Mgh-capacity machines are making in many factories simply because tool designers are not as bold in de- signs as they might be. For bevel pinions, and other angular work of similar character in which the angle IS less than 40 degrees on one side of the center line of the work, a generating attachment for a hori- 212 TOOLS AND PATTERNS mmial turret lathe may be made that will handle a wide variety of work. Such an attachment is shown in Figure 95. The work, A, is held on a special form of arbor where the pilot, B, enters a bushing, C, in Ije face of the attachment and makes the probabil- ity of chatter very remote. The turret of the ma- chine IS furnished with a bracket fastened against one of the turret faces, as shown at D. This extends OBt and overhangs the turret and has a steel pilot, ^, at Its forward end, which is guided in a bushing, F, supported by the bracket, a This bracket in turn IS fastened to tie spindle cap, or to some part of the head construction which is sufficiently massive to permit its being used as a support. This portion of the design depends largely upon the type of turret lathe to which it is to be applied. The bracket, B, that is fastened to the turret face, GENERATING AND FORMING ATTACHMENTS 213 is furnished with a special slide, H, to which tool- blocks, snch as that shown at K, can be readily ap- plied. These tool-blocks may have one or more tools in them according to the work for which they are intended. The slide itself is free to move up and down as held by the straps, L. The back of the slide is furnished with a block, M, that is free to swivel. A powerful spring, adjusted by means of the screw shown at M, holds the entire slide up until the swivel block strikes the bevel indicated at O. This bevel is cut on a long rectangular bar of steel, P, properly fitted to a slot in the fixture. The angle of the bevel is made according to the work to be done, but any number of bars may be made np for different bevels, and they can be replaced and snbstituted one for the other in a moment's time. The action of this device is extremely satisfactory, and its adaptability iis such that it can be applied to a wide variety of work. In operation, the end of the tapered bar (which is guided in the bracket on the headstock) comes against a stop (not shown) before the cntting action of the tool, Q, commences. As the tapered bar does not move after it has been brought to the stop, it is obvious that the entire taper-turning device moves forward along the taper bar, and that the swivel block, M, follows the angle, 0, on the tapered bar as it is constrained to do by the swing at the back of the slide. The tool, there- fore, follows the same angle, and generates the cor- rect taper on the work. After the work has been finished, the entire mech- anism is withdrawn by a backward movement of the 214 TOOLS AND PATTERNS tnrret, and any other tools which are on the turret in other positions can be brought into action. After tne worlc has been done on one piece, another one is pot in position on the arbor, and the tnrret is in- dexed to Its original position. After this has been done, the lever, R, is pulled forward to throw the tapered bar ahead into its original position ready for uie new job of work. An equipment of this kind may be made up with two attachments, one of which can be used for rough- ing and the other for finishing. These two attach- ments can be on opposite sides of the turret and may be tied together by means of a suitable tie-bracket, such as that shown at S. I have designed several equipments of this kind for bevel gear work and other ai^nlar work, and have found them very satis- factory m action. Radius Generating Attachment for a Vertical Turret Lathe.— The Bullard vertical turret lathe is adaptable in many ways: By the aid of forming attachments almost any kind of shape may be generated, and the machine is of such rigidity that the heaviest cut can be taken with impunity. Incidentally, in regard to tte powOT of the machine„the story is told that upon being asked by a prospective customer, "How manv machines can be handled by one man," Mr. Bullard repUed, "It takes two men to operate one machine, one to handle the machine and the other to carry away the chips." The simple attachment for this type of machine, shown ,n Figure 96, is for forming or generating a radius on the surface of the large pulley, A. The GBNEaATING AND FORMING ATTACHMENTS 215 FIG. 96. BADIUS GENERATING ATTACHMENT FOR FACINO A Pni.L£Y ON THE BULLARD VERTICAL TURRET LATHE forming or generating is accomplished by means of the side head with the tool shown at B, and attach- ments, consisting of a couple of brackets, C and D, are attached to the column of the machine. These brackets support a slotted plate, E, by means of the bars, F and G, which are adjustable vertically. The side head is provided with a T-slot, H, in which a link is pivoted, as shown at E. The radius of the link determines the radius to be generated by the tool at B, and as the link is of the very simplest constraction it will be seen that different radii can 216 TOOLS AND PATTERNS be readily established by simply providing an extra link ot the desired length. The plate, E being slotted at L, aUows the link to be fastened 'at any deared point in the slot, so as to determine the exact center from which the radius is to be described. There IS httle eost connected with the mannfacture of an attachment of this kind, and its usefulness and adaptability is qnite evident. Ansmlar Generating Attachment for Vertical Tor- ret Lathe.— To machine an angular surface, such as that shown at A, Figure 97, on work of large size, a Bullard vertical turret lathe may be supplied with an Migular generating attachment. Let it be sup- posed that the bevel ring gear shown is to be ma- chined along the surface, A, with an attachment mch as that indicated in the illustration. The tool, B, m this case is held in the turret of the side head, and angular motion is obtained by means of the roller, D, which bears against the angular plate, C. The angular plate is fastened to the side-head ram and IS adjustable along the T-slot, X. The roller, D, IS also adjustable up or down in the slot shown in the vertical plate, B. Provision for quick removal of the roller is made in the large holes at each end of the slot. The slotted plate is supported in much the same manner as that shown in Figure 96 By means of a forming plate in place of the angular plate, this attachment may be used for forming differ- ent shapes if desired, and the entire attachment is sufficiently flexible to handle work with quite wide variations. When the vertical turret lathe is used for heavy manufiicturing in quantities, an attachment GENERATING AND FORMING ATTACHMENTS 217 no. 97. ANOULAK QENEIUTINO ATTACHMENT of this kind may be applied with excellent results. lutemal Sadius Boring Attachment.— It is occa- sionally necessary to mach|BM||, inside radius on a piece of work, and although conditions reqniring such an operation are rather rare, **it is the unex- pected that always happens/' 218 TOOLS AND PATTERNS 1 5-— J O O o *m«a nWaWAL-RAMTO BORING ATTACmm^ SdTL t^.^^^'hined to the shape indicated St Th ^^^^ ^ ^^^«<^ turret lathe The attachment shown, made up for the work or the nature indicated several years ago with ex- 1?^^ ^ self-contained in the bar, B. Thi. bar IS located in the turret of the machine and IS of massive proportions so that it may be rigid «^^tted to receive a swiveled toolholder, carrying at each the tools, GBNBRATINa AND FORMING ATTACHMENTS 219 C and B, set to cut the same radius from the center of the bar. A link motion allows the lug at the end, E, to travel radially when it is pushed downward by the sliding block, F, operated by a special rec- tangular piece, G, in the side-head turret of the ma- chine. It will be seen that when the side-head down- feed is started, the action of the sliding block causes the cutting tools, C and D, to describe an. arc, thus generating the inside radius. Bigidity of the bar is assured by the pilot, H, which enters a bushing in the center of the table as indicated. This attachment is decidedly special, and was con- structed for a particular piece of work requiring con- siderable accuracy. It is not to be supposed that such an equipment will be frequently called for, but conditions may arise in any factory which may neces- sitate some arrangement for internal radius boring, in which event an equipment of this kind would be of the greatest use. CHAPTER XV . VEETICAL BOBINQ MILL PIXTUBES Fnadamatil Oonstmetion Features—Fixtures dp «gned for vertical boring n,i„s are natu^dlv heavier m construction than those used" „ a perfectly logica because the work done on a ver- bonng rmll requires heavier speeds and fel than the class of work done on tlTe smfllil. ^ Ughter ujachines.. While a vertical bor^^^^^^^ nsed for machining many of the same stvles of sr^^r^'r-'r^' z * '•--tauurrtt,: the difference in the work, however, is one of size- STollr^"*'"'" " "^"^"^^ ^ tion"wiiw: V "^^T mentioned in connec- iat Thf wI'J • T*'''' ''"""^ "'i"- That is it t Inf " « horizontal plane, and fix urrl"r'.''^'^' counterbalance any if the "".odf shaped piece, as it would he m?it ha, th« . "° » ^«rtical boring ti^ lit '•'^ of rotation in a ve" tical plane, and the work revolves horizontally; 220 ' 221 while on the horizontal turret lathe the center line or axis of rotation is in a Iiorizontal plane, and the work revolves vertically. In vertical boring mill practice, therefore, the work may be laid down on the table of the machine and can readily be clamped down to it. The weight of the piece really assists in holding it; and the only thing necessary in the clamping device is that pres- sure enough be applied to keep the work from slipr ping under the pressure of the cut. It must also be remembered that the cuts taken on these heavy boring milte, are greatly in excess of those used on horizontal machines. For many kinds of heavy manufacturing work the vertical boring mill or vertical turret lathe can be used to freat advantage, and the massive construc- tion of these machines permits work to be done within close limits of accuracy. Furthermore, ma- chines of this type can be easily set up with a com- paratively small outlay for tool equipment, so that although tlie first cost of the machines is rather largOi the productive efficiency is extremely high. Vertical Boring Mill Fiztare for Thin Work.— The problem of holding and machining a piece of thin work is always more or less difficult, because it is not easy to hold the work without distorting it, and in addition, the work is likely to be sprung out ef shape by the pressure of tie cut in machining. It is necessary, therefore, in designing a method for holding a piece of thin work, to strive to prevent both distortion from tlie holding device and distor- tion from the pressure of the cutting tool. ™. 99. METHOD OF HOU)INO ram WOIIK W A VIBTKUL VERTICAL BORING MILL FIXTURES 223 An excellent example of a piece of work of thin section to be machined on the vertical boring mill is shown in Figure 99. The method nsed for hold- ing this piece and supporting it while machining, can be applied to a number of cases of similar char- acter with slight variations. The work is large in diMneter, and it is necessary to machine it on the surfaces A, B, C, and D. Since the web, B, is very thin, it is necessary to support this portion of the work to keep it from swinging downward while the cutting tool is in action. The direction of the cut is indicated by the arrows; and the tool which is used on the portions B and C, is shown at E in the side-head of the machine. The work is laid down upon a special cast-iron locating ring, F, which ie held down by lugs, indicated at 6, in the table key- slots. The work is centered by means of the special hook-bolt jaws, H, which are soft and bored out to fit the outside of the work. (Incidentally, the work has been finished on the surface, K, in a previous setting.) The three jaws indicated are attached to the master jaws on the table chuck, as shown in the upper view, and, as the table chuck is of the three- jawed geared scroll variety, the work is readily cen- tered on the table. The jaws are brought up very lightly on the outside of the work, so as not to cause any distortion; and after they are brought in con- tact with the work, the hook bolts, L, are tightened by means of the nut, M, so that the work is gripped at three points around the circumference in much the same manner as though it were held in three separate vises. It can be easily seen that this method 224 TOOIiS AND PATTERNS of holding is exceptionally rigid and does not cause distortion in the work. The pot, F, acts as a locat ing device to give the correct height to the work, and at the same time it supports it against the pressure of the cut. Speeial Tixtme with Tapered Plug Locater.— It is frequently necessary to locate a piece of work on a tapered hole that has previously been machined, and at the same time to hold the pece by means of clamps on some other portion. As it is a difficult matter to machine a tapered surface and a plane sur- face so that they will always bear an exact relation to each other, some method of holding must be used which will compensate for the variations between the two surfaces. Let us take as an example of this kind of work the piece shown at A, Figure 100. This work is a iywheel for an automobile engine, and it has been machined in a previous setting in the tapered hole, B, and also on surfaces C, D, and E. Now in order to machine the side of the work, F, and the hub, G, 80 that they will be in the correct relation to the previously machined tapered hole, it is necessary to locate the work on a plug in this tapered hole. But while this location would be all right, it would not be possible to clamp the work easily without spring- ing it out of shape if it were to be located only on the tapered plug. The surface, D, then, must be used for attadiing an additional clamp, but as this surface may vary slightly in its relation to the tapered hole, any method of clamping must be so designed that compensation may be made for sur- VEBTICAIi BO1IN0 MILL FIXTURES 225 no. 100. BmMNQ A PIEGS OF WOBK BY rrS TAPEEED HOU face variations. This is accomplished by making a tapered plug or shell, as shown at H, and locating this shell on a threaded stud, K, set in the center hole in the table. The upper end of the tapered shell is squared out to receive the special socket wrench, L, by means of which it is operated. 226 TOOLS AND PATTERNS The method of using this fixture is as follows: The plug is lowered by means of the screw, so that the work can slip onto it loosely. The clamps, M, which are three in number, are then set up lightly on the rim, C. After this, the socket wrench, L, is used to screw the tapered bnshing up in the hole, thns locating the work on the tapered portion. After this has been done the clamps are tightened securely, and the work is ready for machining. Applications of this principle can often be used to hold work of this character, with various methods of compensating. The tapered shell bushing is some- times arranged on a spring, so that it is self-locat- ing. A method of this kind is quite satisfactory and generally gives good results. Ezpandiii; Arbor and Faceplate for Vertical Bor- mg Mill— For a piece of work that has been pre- viously machined and is to be located in the second netting by the previously machined surface, it is necessary to make up a locating fixture. A good example of such a fixture is shown in Figure 101. In this case the work, which is a double bevel gear, hm been previously machined at A and B, and on the bevel-gear faces, C and D. It is necessary to locate it for this operation by means of the hole, B, md, as the work must be very accurately done, an expanding arbor must be used in the hole. In con- junction with the expanding arbor, it is necessary to prevent the work from springing at the surfaces of the outer bevel-gear ring, D. A cast-iron fixture body, E, is located in the center of the table by means of the plug, F, which enters VBBTICAI4 BOMNa MILL FIXTURES 227 FIG. 101. PLAN AND SECTION OP EXPANDING ARBOR AND FACE ¥UkTE FOR VBBTIGAL BORINO MILL 228 TOOLS AND PATTERNS the center hole. The work is placed in position over the central ping and drops down against the surface, A, of the fixture. A split ring, G, similar to the type described under the heading Split Ring Expanding Arbor," Chapter XHI, is then expanded by means of the bolt, H, thus giving the desired centering action. The spring jacks, K, are now re- leased and allowed to spring up against the surface, D, after which they are locked by means of the set- screws, L. The final clamping of the work is ac- complished by means of the hook-bolts, M, which are operated by the bolts, N. The principle shown in this fixture can be applied to a great variety of work, and it can be adapted to suit different conditions, both as to the means of clamping and as to the points on which the work is located. Any method of clamping applied to a fix- ture which has been previously machined must take into consideration the fact that no distortion can be permitted. The use of springs and spring jacks for this purpose is common. Care must be exercised that when the set-screws are tightened they will not force the jacks out of position. Vertical Boring-Mill Fixture for a Fragile Alumi- num Casting.— One of the most difficult examples of a fixture for holding a piece of thin work of irregular shape, and machining it when held without causing distortion in the work, is shown in Figure 102, at A. In the plan above, it will be seen that the cast- ing has a thin flange of approximately elliptical shape and the face of this flange is to be machined m the setting indicated. In addition to this the face, VERTICAL BORING MILL FIXTURES 229 72ZZZZZ TO. 102. PLAN AND SECTION OF A VEETICAIi BORING Mllli FIimJilE POR A WRkQUM ALUMINUM CASTING B, located below the snrface of the other flange, must also be f acei**ii the same operation. The part of the flange indicated at A is joined to the right- hand portion of the casting, as indicated in the sec- tional view below. The other side of the flange, how- ever, at C, is open and nnsupported, making it very difficult to hold the piece without forcing the parts out of alignment 230 TOOLS AND PATTEBNS This piece of work is one of the most difficult that I have ever encountered, and I give it here simply to show the possibilities of arranging clamping de vices so that they will not distort the work. The piece IS set up with the boss, on the under side of ^ locating in a V-block on the fixture base, and the edge of the adjacent flange is supported by the spnng pins indicated at D. These spring pins are locked by means of the special screw, B. The flange A, rests against a knife^dge locater, F, and is lightly Jami^ by means of swinging knife-edge dogs at e and H, while resting on the pads shown at K The other side of the flange, C, is simply a rim which must be held and firmly located without sprmging it out of position in the slightest degree For this purpose, the floating hook-bolt, shown at L is made in triplicate. These bolts are used in the three bosses, M, N, and 0, although only one of them IS shown in the illustration. The action of the hook- bolts IS such that the work is clamped between the jaws shown while the entire mechanism "floats", so that It does not strain the work. After the hook- bolt IS tightened, it is locked in place by means of the set-screw, P. By this method of clamping, any piece of delicate sectaon may be clamped without causing distortion. Although the example shown is a rare case, the prin- ciples involved in this design can be applied with equal success to other work of similar nature. It is sufficient to say in regard to the fixture mentioned that its work was in every way satisfactory and the work was maduned without error. VEBTICAIj BOBINe MILL FIXTUEES 231 Simple Tiitnre for Machining an Eeeentrie.— An example of a fixture for turning an eccentric piece was shown in the group of fixtures in Chapter XII, but in that case the work was held on a swinging fixture applied to a horizontal turret lathe. Another example of an eccentric turning fixture of the in- dexing type, but arranged for a vertical boring mill, is shown in Figure 103. In this case, the work is set up on an indexing plate, A, by means of the three pins, B, in the flange. This indexing plate is located eccentrically on a base, C, which is fastened to the boring mill table, being located on a plug, D, in the center hole. After the work is set up on the pins, it is clamped in place by means of the three hook-bolts shown at E, these bolts being brought down on the flange as indicated in the upper view. When clamped in the position shown, the hole, F, is bored, and then the upper part of the fixture, A, is swung around until the center, G, takes the place of the hole previously machined. A locating pin is provided at H to give the correct location. In indexing the fixture, the button clamps around the rim, as shown at K, and is loosened to permit the revolution of the portion, A; but when the table has been indexed to the proper position these clamps are again tightened before the machining takes place. The next operation on the work is the ma- chining of the eccentric, L, when it has been indexed into the position mentioned. After this the work can he removed from the fixture and another substituted for it. Work of this character m frequently machined in TOOLS AND PATTERNS MG. 103. PLAN AND SECTION OF A FIXTURE wm AN BOqiNTOIC PIECE OP WORK two settings, and no attempt is made to make an indexing fixture sneh as that shown. In such an event the ordinaiy method of procedure is to bore the hole first and then locate the work on another fixture on a atnd set eccentrically to the center for VEETICAL BORING MILL FIXTURES 233 the turning of the eccentric surface, L. The matter ||»iesigning a fixture for a piece of work of this kind is dependent entirely upon the number of pieces to be machined and the accuracy required in the finished product. Application of this principle may be made to many varieties of work where two sur- faces are machined eccentric to each other. Sliding Fixture for Boring a Pair of Cylinders.— When a pair of cylinders, such as those shown in Figure 104, at A and B, are to be bored and faced on a vertical boring mill, the work must be handled either by means of two settings, or by an eccentric or sliding fixture. If two settings are to be used, the ordinary method of handling is to machine one of the cylinders first and then set it up on a stud eccentric to the center of the table at the correct distance to bring the center of the second cylinder into position for boring. For rapid production, how- ever, a sliding fixture or one having an eccentric movement can be designed, so that the work can all be handled at one setting, thus saving consider- able time in the machining and in the handling of the work. The device shown in Figure 104 consists of a base plate, C, which is fastened to the table and is centrally located by means of the plug, D. The base plate is held by means of the bolt, E, in the table T-slot as indicated. Mounted on the base plate, C, is a dovetailed slide, F, on which suitable clamps, G, are provided to hold the work. A sectional view taken through the base is shown at H. Along eacn side of the sliding members are two handles, K, for TOOLS AND PATTERNS 104. BmmQ wnmjm worn mmmQ a pais ov ctmndebs VBBTICAL BOMNO i!mlPIXTUBES 235 the purpose of locking the sliding fixtures in any desired position. After one of the holes has been bored, the handles are unscrewed and the fixture is push^ over until the second cylinder is under the center of the spindle, the correct location being as- sured by means of a taper pin, L. When the de- sired position has been reached, the levers, K, are again tightened, and the second cylinder may be bored in exactly the same manner as the first. Threaded Knock-off Arbor for Vertical Boring Mill.— The work shown at A, Figure 105, is a large head used for a rock drill. The piece is made of chrome-nickel steel which is extremely hard to cut. The work has been previously machined on the in- side surfaces, B, and has been threaded at C as indicated. It is necessary to machine the outside tapered surfaces, A and B, in another setting, and these surfaces must be in correct relationship to that previously threaded inside of the work. A knock-off arbor was therefore suggested, such as that indicated in the illustration. This work was to be done on a vertical boring mill, and accuracy was an essential point. The base of the fixture, D, is located on the table of the machine and is held in place by means of the bolts, E, which pass through the T-slot in the table and are clamped by means of the shoes shown at P. The location of the plate is obtained by means of the threaded stud which is ground to a fit at G in the central hole of the table. The right-hand threaded arbor, H, is made at the upper part,Vso that the thread corre- sponds to the inside thread in the work at C. Below 23i TOOLS AND PATTERNS F-1 TO. 105. THEEADB© KNOCK-OFF ABBOB WOR A VEBflGAL BORINO MILL this a left-hand thread is cut at K. The lower part of the arbor is provided with two pins, L, in order to give good driving properties. The knock-off por- tion of the arbor is shown at M, with a left-hand thread to fit the part K. Let it be supposed that the fixture is abont to be loaded by attaching the piece A. At this time tlie knock-off portion, M, is screwed up until it shoulders against the portions N. The work, A, is then screwed OB imtil it makes up against the surface 0. The VERTICAL BORING MILL FIXTUEBS 237 work is now ready for machining, and during the action, because of the pressure of the cut, the sur- face, 0, becomes very tightly in contact with the knock-off pad. After the work has been done, a sharp blow on one of the projecting lugs of the knock-off, M, causes the pressure at the point 0 to be relieved, so that the work can be easily unscrewed from the arbor. The principles involved in this arbor are practically the same as those described in Chap- tei XIII, under the heading Expanding Arbor for an Adjusting Nut" CHAPTBB XVI CHONDING FIXTURES Adaptabili^ of Cutting Hxtum.— The f unctioiis of grinding as praetieed by manufacturers in general have been taken up in Chapter VII, but the matter of holding fixtures for the grinding operations has not been dealt with to any extent. As a matter of fac^ fixtures used for grinding purposes are very similar to those used in various machining opera- tions, although the necessity for holding the piece rigidly is not present, since the amount of pressure exerted on the work by the grinding operations is nothing like as severe as by the cutting operations. Many of the fixtures devised for machining opera- tions can be used for grinding, but as a rule grinding fixtures are considerably lighter in construction than those used for turning and facing. The principles which apply to holding devices of various kinds for turning can be applied to grind- ing practice, with proper modifications to suit the conditions. For example, there are many cases where a spring clamp can be used for a grinding fixture with excellent results, and yet such clamps would not be suitable in any way for machining operations on account of their lack of holding power. The pull- ing action of a grinding wheel taking a very light 288 eilNDING FIXTURES 2S9 fIG. 106. METHOD OF SETTING UP A GRINDING MACHINE FOB EXTERNAL GTMNDRIGAL GRINDING cut is nowhere near as severe as when a cutting tool is used on the work. When cylindrical work is to be ground, there is seldom a need for any sort of grinding fixtures— unless some portion of the work is irregular, in which case a special method must be used for holding. The ordinary method of locating and holding a piece of cylindrical work for external grinding is illustrated in Figure 106. The work, A, in this case has several shoulders, B, C, and D, which are to be ground in the setting indicated. The work is located on the centers shown at E and F, and is driven by a dog, 6. which enters the driven faceplate, H. While the work is in the position indicated, the wheel, K, is traversed in the direction indicated by the arrows until the various diameters have been ground to the correct size. It will be seen that no special eqnip- ment of any kind is necessary in performing work of this character. 210 TOOLS AND PATTEBNS no. 107. BOTABT AND RECTANGULAR MAGNETIC CHUCKS Magnetic CQmcks. — ^Frequently, however, cylin- drical work requires special fixtures, for although the portion which is to be ground may be cylindrical, it may happen that the method of holding must be special in order to accommodate a peculiarly shaped piece. CSiueks, either magnetic or the step-chuck type, are largely used for holding work which is to be ground. When the work permits the holding by magnetic chucks, this method is largely used and gives very satisfactory results. Otherwise, a step- chuck can be arranged to handle the work. A group of magnetic chucks, made by the Heald Machine Co., is shown in Figure 107. Those shown at A and B are of the rotary t3rpe, while those shown at C, D, and E, are of the rectangular type, not used on rotary machines, but applied principaUy to sur- face grinding. One of the great advantages de- rived from the use of magnetic chucks is the rapidity with which the work is applied to and removed from the chuck. Another advantage lies in the fact that there is little danger of distortion caused by an im- GRINDING FIXTURES 241 proper method of clamping. This feature is par- ticularly noticeable when thin work is to be ground. Still another advantage is that a great number of pieces can be held at the same time. It is only nec- essary to throw a switch in order to apply the elec- tric current, magnetize the soft iron core of the chuck, and hold rigidly any work on its surface. The rotary chuck, shown at A and B, can be Applied to a horizontal machine for cylindrical grinding, or to a rotary surface-grinding ma- chine. Piston rings or packing rings, for example, are usually ground on their edges on this type of chuck. The rectangular type of chuck, shown at C, D, and E, is particularly suited to surface grind- ing and to milling or planing operations. In applica- tion they hold a number of small pieces or a single piece of long work. Many uses will be found for these chucks in a manufacturing establishment, and the type of chuck most suited to any man's work can best be deter- mined by consultation with the various manufac- turers. Suitable demagnetizers are applied to all chucks of the magnetic type, so that after the work has been removed, no future trouble is experienced from magnetism remaining in the work. Grindin|l"%izture for Universal-Joinl Part— A number of pieces in an automobile are made of alloy steel that requires special methods of hardening. One of these pieces is the rocker arm of the universal joint, shown in Figure 108 at A. This piece must be ground on the two cylindrical portions B and C, and it requires a special fixture as indicated at D. This 242 TOOLS AND PATTERNS FIG. 108. FIXTURE FOB GRINDING UNIVERSAL JOINTS fixture is not designed for the purpose of holding the work, but merely to provide a means for driving the long end, A, and preventing vibration of the work during the process of grinding. Snch a fixture as this can be mounted on an adapter plate, as at E, attached to the spindle of the machine and rotated. The work in Figure 108 is held on the faceplate, and is located on two centers, as indicated. A suit- able thumb screw is provided at F on the fixture, so that when the work is placed in position the thumb screw can be tightened to throw the work over until it strikes a stud, 6. Since this fixture with the work in position is heavier on one side than on the other, a cast-iron lug, H, is applied to the oppo- site side, as shown, so that the entire fixture can be properly balanced before the work is done. If a grinding fixture of this sort were to be made up and not properly balanced, the action on the entire ma- chine would be injurious and the work produced would not be true. It is not only advisable but nec- essary to see that any fixture used for grinding is properly balanced to obtain the best possible results. ©BINDING FIXTURES 243 WIQ. 109. FIXTURE FOR GRINDING PISTONS Piston Grinding Fixtures.— Manufacturing prac- tice differs in regard to the finishing of automobile engine pistons, but most makers finish the external surface of the piston by grinding. When this is done, accuracy can be more readily kept within the re- quired limits, and the superior finish gained by the grinding is an added advantage. A fixture for holding an automobile piston while grinding is shown in Figure 109. In this case, the work. A, is located on an arbor, B, which is drawn back into a tapered hole, C, in a special nose piece, D, which is screwed to the end of the last spindle, E. A key to hold the work on the spindle is pro- vided at F, somewhat unnecessarily in the instance shown. I say unnecessarily, because the amount of friction generated by the grinding wheel against the outside of the piston, A, could never be sufficient to permit the arbor, B, to turn in the tapered hole, TOOLS AND PATTEBNS especially when drawn back by means of the nnt and washer shown at G. The end of the piston is given additional snpport by meeris of the center shown at H, this center being in the tailstock of the grinding machine. The method of holding the pis- ton on the arbor is somewhat ont of the ordinary and IS therefore worthy of description. The open end of the piston locates on the arbor at K, and is drawn back firmly against the shoulder, L, by means of the rod, M, and the taper wedge, N When the work is placed in position, the ball-ended ping, 0, is dropped through the wrist-pin hole, P passing through the draw-back rod as indicated' After this has been done the wedge, N, is pushed lightly into place until the operating rod, M, drawi;i.«.vj 4.1. X wetn, for there is ^^Li J^^r^ "T" ^^^«ge their tln^?i^ the eeBter of the gear because of distor- tCf^^i^" ""'^^^ ^ ^^^^ the bottom of the tooth ufiuaUy selected as the locating pXT GRINDING FIXTURES 249 HG. 112. SECTION AND PLAN OF AN ABAPTABU: FIXT0BE FOB OBINDINO SPUR GEARS The fixture shown in the illustration consists of a nose piece, C, mounted on the spindle, D, and pro- vided with a tapered portion, E, as indicated. The gear is held and located by a series of blocks, F, each of which has a point, G, so designed that it will strike the bottom of six teeth, as indicated. These six blocks are radially located in a split mem- ber, H, by means of the clamps shown at K. This split member, H, is slotted in six places in order to allow it to contract as it is pulled back into the tapered portion, E, by means of an internal mech- anism running through the spindle as indicated at L A spider-shaped piece, M, is set into the base piece, C, between the slots, N, which provide for ex- pansion and contraction of the piece, H. This spider is provided in order to give an endwise location to the work. It will be seen that as the work is placed in the chuck, the points, 6, are drawn in radially until they center the work from the bottom of the six teeth as indicated. This mechanism may be applied to a 250 TOOLS AND PATTERNS FIG. 113. ADJUSTABLE FIXTTJBE FOB QBINDINO A BEVEL PINION gear having an odd number of teeth by making up the blocks to suit the conditions. Adjustable Fixture for Grinding a Bevel Pinion.- A bevel gear that has been hardened is subject to the same changes as those that may be produced in a spur gear. It must, therefore, be set up for the grinding operations in such a way as to compensate for any errors caused by the hardening process. In this case, the pitch line of the gear is generally used as a locating point. Taking the example shown in Figure 113: the work, A, is to be ground in the tapered hole, B, which must be concentric with the teeth cut on the outside of the gear. A different type of fixture is provided for this class of work. A special nose piece, C, is screwed to the end of the spindle in the usual manner, and is provided with four holes, D, in which are inserted the round wires, E, which pass through rollers, F, QEINDING FIXTURES 251 and rest against a hardened ring, G, located in the nose piece and having a suitable taper so that the center line of the roller will adapt itself to the pitch line of the gear. An enlarged view of one of these rollers is shown m section at the lower part of the illustration. It will be seen that the center hole through the rollers is tapered for clearance only, so that a floating action is permitted, allowing them to adapt themselves to the gear. Provision is made for supporting the wire at the inner end of the chuck by means of the ring, H, and suitable holes are drilled to receive the ends of the wire. When setting up the work. A, it is placed in the chuck, and the various rolls find their location on the fixed line of the gear. The spring clamps, K, are then swung around into position to hold the gear in this location. The work is then ready for grinding. This type of fixture also can be adapted to bevel pinions of odd or even teeth by slight changes in the roll location and by suitable rings of the correct angle, as shown at G. Orinding Fixture for a Large Bevel Spring Gear. The bevel ring gear used in the rear axle of an auto- mobile is likely to change somewhat during the hard- ening process; and it is essential, therefore, to grind it after hardening in such a way that the teeth and the center hole will be in correct relation to each other. For this purpose a fixture can be made up for grinding similar to that shown in Figure 114. In this case, the work is located by means of a master gear, shown at A in the figure. This master 252 TOOLS AND PATTERNS FIG. 114. GRINDING FIXTURE FOR THE LARGE BEVEL RING GEAR IN THE REAR AXLE OF AN AUTOMOBILE gear is an exact duplicate of the gear which is to be ground, and is fastened to the faceplate shown at B, so that the pitch line of the master gear is ooncentrie with the center of the spindle. In opera- tion, the work, C, is placed in position against the face of the master gear and with the teeth between those of the master gear. As each of the gears is beireled, the bevels act in such a way as to center the gear in the correct position. After the location has been assured, the spring clamps, D, are adjusted to hold the work properly. As little pressnre is re- quired to hold a piece of work of this kind, these clamps answer the purpose very well and can be quickly adjusted to position. The principle shown here can be adapted to any work of this character and the work obtained by its use gives excelleat results. CHAPTER XVII OPEN DRILL JIGS Functions and Operation. — Strictly speaking, a drill jig is a device by means of which a piece of work may be properly located and clamped in order that a series of holes may be drilled in the work at certain fixed locations. It will be seen, then, that any number of pieces of similar shape and form can be placed one after the other in a drill jig and all the pieces will be made in snch a way as to be inter- changeable. Not only is a drill jig provided with the proper methods of clamping and holding the work, but there are also a number of bushings, cor- responding to the number of holes in the piece, located in the jig in such a way that the drills used in the manufacture will pass through these bush- ings and be guided thereby. The bushings are made of hardened tool steel, and are located very care- fully by a toolmaker in their oorreet positions to produce the holes desired. Natumlly, the shape of the work to be held exer- eises a powerful influence on the form of jig to be designed for the work. It is evident that a jig for a simple piece of work which can be held easily by a couple of simple clamps, m much easier to design iuaii one which is of such shape as to require very 258 254 TOOLS AND PATTERNS special methods of locating and clamping. In order to illustrate the functions of a drill jig, let us suppos that a hole is to be drilled in each end of a simple lever, and that the work is to be done in a drill jig. Let us further suppose that the workman has a drill jig before him on the table of a drill press, and that he is ready to do the work. He takes the work in one hand, then, and places it in position in the drill jig, clamping the work securely by means of the elamps provided in the jig. After this he pulls the drill jig under the drilling-machine spindle, or spindles, and proceeds to feed the drill down through the bushings provided for it in the jig. After the drill has been pressed through the work to the proper distance, the workman raises the spindle, removes the jig to a convenient position on the table, and releases the clamps which hold the work in place. This allows the piece to be taken out of the jig and replaced by another one, and the process is repeated. When drill jigs are to be made for large work, or when a number of holes are to be drilled at different angles or from different sides, it is necessary to make up a drill jig of more elaborate form. If the work is very large and heavy, trunnion jigs are frequently employed. Jigs of this character are so made that the work is placed in jKMsition, clamped, and the entire jig is revolved on a bearing at each end, this bearing being the term from which the word trunnion is derived. A trunnion jig is mounted . on a pedestal, or base of some kind, in such a way that it can be -swung into the correct position for drilling. It is also provided with suitable indexing OPEN DRILL JIGS , 255 mechanisms, in order to locate the jig properly at the various angles in which it is to be drilled. Some- times trunnion jigs are mounted on a sort of carriage which can be rolled from one drill-press table to another, in order to take advantage of special group- ing of the spindle. In regard to the grouping of spindles, it must be remembered that many drill jigs are used on mul- tiple-spindle drilling machines. A number of drilling machines of this character can be arranged one after the other and connected by means of a track or miniature railroad on which a trunnion jig, suitably mounted on a carriage with wheels which fit the rails of the railroad, can be rolled from one machine to the other and indexed, as previously mentioned. An arrangement of this sort can be used for such work as an automobile cylinder or crank-case, or a machine-tool gear box, or some other piece of work that requires a number of holes to be drilled in it from different sides. The advantage of such a jig is that the work is once clamped in position and is not released until all of the holes have been drilled. In this way, the jig makes it possible to obtain a number of pieces of work, all of which are drilled in exactly the same relation to each other. Drill jigs can be designed so that their work can be done on any type of drill press, from a slngle^pindle ma- chine to one of the multiple type. A number of points must be considered in the de- sign of a drill jig: the method of locating the work in position; the method of clamping it so that it will l>e firmly held against the pressure of the drill and 256 TOOLS AND PATTERNS at the same time will not be distorted by the pressure of the clamp; clearance around the work; provision for chips; easy aoeessibility for cleaning so that no variation in the work can be cansed by chips or their accumulation on the locating point; and finally a method of clamping which will be both rapid and positive in aetion. When a series of jigs is to be made, these points must all be taken into consideration if the jigging process is to give correct results. Any incorrect method of locating, or any method of clamping which tends to distort the work, may cause a great deal of trouble and expense; for even with work requiring great accuracy it i» entirely possible to drill a series of holes in sneh a way that they will not coincide with other holes to which the work is to be fitted. Again, if the work is strained by the method of clamping, the hole will not line np properly with the other work and a great deal of unnecessary fit- ting nmst be done when the parts are assembled. In taking up the more common types of drill jigs, let us consider that the two most general types are the open and the closed jigs. An open jig is one in which the work is held in such a way that it is not enclosed. A closed jig is one of the box type, where the work is placed in a sort of box or frame and is usually drilled from several sides in the same setting. A Simple Plate Jig.— The work shown at A, Figure 115, is a cast-iron flange which is to be drilled with six holes, B, located in a circle around one face of the flange. This is an extremely simple piece for 257 Vm. 115. SIMPIiE VhkTR JIG which to make a jig and, therefore, it is used as an example to show what simple forms may be used for jigging purposes. In this case, the work has been previously bored and reamed, so that the jig plate, C, can be located directly on the upper flange by means of a plug, D, which enters the roll. The jig plate is provided with a series of bushings, E, so located in the plate as to give the resired location to the hole. For a piece of work of this kind no clamping device is necessary, as the work is usually done on a multiple-spindle drill press, each spindle of which contains a drill of the proper size for the work. These drill spindles TOOLS AND PATTERNS are adjustable, so that they can readily be made to correspond to the holes in the jig. In operation, a jig of this kind is simply dropped on the work which is located on the drill press table, and immediately thereafter the spindles of the drill press are brought down until they enter the bushings; after this the feed is started and the work is completed without any clamping device being necessary. The pressure of the drill is sufficient to hold the work in position, and after the holes have once been started there is no necessity for any method of clamping to keep the jig properly located. Jigs of this kind are suited to many kinds of work that have been previously machined, as indicated, and also to work that has a finished face on which to rest it while the drilling is taking place. Plate Jig with Supplementary Supporting Sing.— Another type of plate jig, more suited to work that would be unstable without support while being drilled, is shown in Figure 116. This piece of work has been previously finished on both sides of the fiange, B, and ako on the outside of the hub, C. It will be- seen, however, that the piece could not be drilled very well without some sort of support, be- cause the radius of the hole, E, is out beyond the base of the hub, A, and if the work were to be drilled without any. support, it would be likely to tip one way or the other unless all the drills were exactly of the same length. In order to oi||||||||e any tendency of this sort, a cast-iron ring, I*, i« made to act as a support for the work. This ring is made of sufiScient diameter and stability to allow the work to OPEN DRILL JIGS FIG. 116. PLATE JIG WITH SUPPLEMENTARY PLATE rest on the flange at B and be supported thereby. The drill-jig plate, D, in this case, is made so that it will slip over the hub, C, and is provided with a series of bushings, B, arranged in circular form to give the correct spacing of the holes. In some cases, the holes to be drilled may be of several diameters, and drills of corresponding diam- eter are used. However, when an occasion of this kind arises, some method of location must be provided, both for the work and for the drill-jig plate in order that the correct bushings may be located properly under the corresponding drill. This kind of jig is usually used on a multiple- spindle drill press, with the spindles grouped to the correct radial setting. Adaptations of the two forms 0^ jigs just mentioned. Figures 115 and 116, may be made to cover a variety of cases. Such jigs are 260 TOOLS ANB PATTIENS f i 1 H ; ■ ' -/j jT* I I i !g! '"^^tt^J^r^r ~ ill rr !• !l Kt 'r !« •I c... TO. 117. mm, JIG FOB AN OIL-PUMP COVER cheap in their eomtruction and answer the purposes forwhich they are intended very well indeed. DnH Jig for sm Oil-Pump Cover.— The work shown at A, Figure 117, is an aluininnm oil-pnmp cover which has been previonsly faced on the surface, B, but has not been turned. Due to the fact that only one surface on this piece has been machined, it is necessary to locate from this snrface for the opera- OPEN DRILL JIGS 261 tion of drilling the six holes shown at C. In order properly to accomplish a correct location for this Avork, the vee principle is tised. In the example shown in Figure 117, the two pins at D are used as locaters of this kind. The work is forced against or between these pins by means of the thumb screw shown at E, and is further located by means of the stop-screw, F, against which the boss is clamped by means of another screw, G. The clamps, H, are then tightened, thus holding the work firmly against the face of the fixture and down on the surface, B. With the work in this position, the entire jig is turned over onto the legs, K, on which it rests while the drilling operation takes place. These legs are a part of the base casting of ike jig, and are surfaced in such a way as to provide an ample means of support which is, at the same time, parallel with the surface, B. Bushings are provided for the holes at C, as in the former instances described. It will be seen that after the jig has been turned over, the pressure of the drills comes entirely against the clamps. H. These clamps, therefore, must be suffi- ciently strong and heavy to withstand the pressure. Jigs of this kind are very useful for many kinds of semi-cylindrical work where there is a single fin- ished surface and a series of holes arranged more or less centrally about the center of the piece. Applica- tions of the principles shown in this jig can be made to a great variety of work. Open Jif for a Lever.— Jigs designed for drilling holes in levers are of two kinds: those which locate from the work in its unfinished state or which locate 262 TOOIiS Am PATTIBNS on bosses at either end of the lever; and those which locate for a single drilling operation of one end-hole from a previously bored or reamed hole in the other end. Both of these jigs are in common use and will, therefore, be described separately. The type men- tioned first is shown in Fignre 118. In this case the lever, A, has been finished by straddle milling the side of the bosses at each end. The jig shown is for the purpose of drilling the two holes, B, at each end of the lever. The method of locating used for this piece is a vee block, C, in which the boss at one end of the OPEN DEUili JIGS 263 lever rests. The other end of the lever is located and clamped simultaneously by means of the sliding yee-block, D. This vee-block is chased up into posi- tion by means of the thumb screw, E, located in a swinging latch, F, between the bosses, G, through >vhich a pin is passed. An additional support is given the latch at the other end on the lug, H. After the work has been located as mentioned, it is clamped firmly by means of the wide clamp, L, which is slotted so that it can be pushed back out of the way to allow the piece to be placed in position. When the work has been clamped as indicated, the entire jig is turned over, so that it rests upon the two feet, K, after which the holes are drilled through the bush- ings indicated. This type of jig is in common use, with certain modifications in regard to clamping and locating in accordance with the nature of the piece to be drilled. It is comparatively inexpensive and gives excellent results. Ofm Jig for a Lever with Stud Locater.— The lever, A, Figure 119, is of similar shape to that shown in Figure 118, but it is of larger size, and the end, B, has been bored and reamed in a previous operation. It is, therefore, necessary to locate from this hole to drill the small end, C. A stud, D, is placed in the jig body, and the work is placed over it as indicated. The small end, C, is located by means of a sliding vee-block, E, which is forced up against the boss by means of a thumb screw, F. The work is keld in position and supported against the pressure of the cut by means of the clamp shown at G. As in the TOOLS AND PATTERNS FIG. 119. (MPEN JIG WITH STUD liOCATEB former case, after the work has been located in the jig it is turned over, so that it rests upon the feet, K, in wMeli position it is drilled. Jigs of this kind are nearly as common as that shown in Figure 118, and their application to many shapes of levers will be apparent. Open Jig for a Small Bnuskit— The work shown at A, Mgnre 120, is a small bracket which is to be drilled at B, C, and D. The holes, B and C, are in one plane, and the hole, D, is in another. Therefore, the jig mnst be so made that it can be tnmed on one side for the latter hole and on another side for the holes at B and C. The use of a vee-block is seen in this fixture at E, and the rounded angular end of the OPEN DRILL JIGS 265 work rests in this block as it is forced there by means of the set-screw shown at P. It will be seen that this set-screw is placed at an angle and also that the vee- block, E, has an angular face. The purpose of this is to make sure that the work will be held down firmly and located correctly. The work rests on the flat milled surface, G, and suitable bushings are pro- vided for the various holes. An additional clamp is provided at H in order to make the clamping action more positive. Legs are provided on the side of the jig at K and also at L, so that the work can be 26G TOOLS AND FATTEBNS WG. 121. SET-ON JIO Vm A TRANSMISSI0N-GA8E COVER drilled in the correct positions. Additional legs are also made at M for purposes of setting up the work. Set-on Jig for a Transmission-case Cover.— When a large piece of work is to be handled and a small portion of it only is to be drilled, a set-on Jig is ad- vantageous. In the design of a jig of this kind it is always necessary to consider the bearing which the work itself will have on the table of the drill press, in order that the pressure of the drills as they enter the work may not be in snch a position as to cause the work to topple over or tip on one side. An example of this kind is shown in Figure 121. In this case, the work, A, has been previously fin- ished by milling along the surface, B, and also on the face, C. At C, four holes are to be drilled as OPBN msMMi Mm 267 shown at E in the upper view. The surface, B, is sufficiently solid to rest on the drill-press table with- out difficulty. The drill jig is made of cast iron and consists of a pipe, D, with lugs at each end through which the set-screws, F, are passed to act as an end-stop for the jig when it is placed in position on the work. Another stop-pin is placed on the other side of the jig plate, as shown at H in the upper view, and in placing the jig plate on the work this pin is brought up against the side of the work before the set-screw, shown at G, is tightened. As this set-screw is tight- ened it will be seen that the entire jig is clamped in place on the top of the work. The jig plate is pro- vided with a series of bushings, E, through which the drills arc passed as the four holes are drilled. This is a very simple type of jig, but application of the principle shown can be used on many other cases for work of similar kind. SeUm Jig tmt a Gas-Control Plale^— Set-on jigs are sometimes used for small as well as for large pieces when the size of the work is such that it can be used to advantage. In designing a jig of this kind care must be exercised to see that there is sufficient stabil- ity to the work itself to permit placing and support- ing the jig upon it. Figure 122 is a very good ex- ample of a piece of work which can be drilled with this type of mi^n jig. The gas-control plate, A, in this case, has been finished in a previous opera- tion, so that the surface, B, is perfectly plane and can therefore be used for setting up the work. The jig is placed on the top of the piece as indicated in TOOLS AND FATTliBNS f fiCL 122. SKMXK m wm mMJu vmm or work the illustration, and the two pins, shown at C, in reality form a sort of Y against which the work is forced by means of the set-screw at the other end of the jig. This set-screw, D, forces up the work and locates it at the same time by means of the vee- blocki E. A series of bushings are arranged to drill the holeSy F and Q, in the top view. It will be seen that when this jig is to be used, it is only necessary to place it in position on top of the work while the work is resting on the drill press table and then to tighten the thnmb-screw, D. After this has been done the jig can be readily moved under the spindles of the drill press, in which posi- tion the work can be drilled without difficulty. The number of other jigs which could be classed under the heading of open jigs, is so great that it is out of the question to enumerate the different types OPEN DRILL JIGS 269 in a book of this kind. My effort, therefore, has been to show new forms of open jig, in order that the discriminating reader may be able to form an idea of the various types and their application to work of ordinary nature. Speaking broadly, an open jig can be made for almost any piece of work when holes are to be drilled from not more than three directions. As the usual thing, however, open jigs are designed for pieces that are to be drilled in one or two directions only CHAPTER XVni ViAjiSMiD Jllio Bushing for an Oil-Pump Shaft— In the previous efaapter a few varieties of open jigs were described, but by no means all types were mentioned. In this chapter, also, it will be impossible to enumerate every type of closed jigs, and yet an attempt will be made to cover the subject in a broad way, so that the reader will be able to get a good idea of the variety of jigs. Beferring to Figure 123, let us assume that the ' bushing shown at A, has been previously bored and reamed in the hole, C, and that the end, B, has been faced. Let us also assume that the outside of the work has been completely finished to the form shown, and that the upper end has also been faced. The work in this case is located on the previously finished hole at C on a small stud, and it rests against the sur- face, By on the locating stud. While in this position, it is clamped by means of the sei^screw shown at H. A button on the end of the set-screw bears against the end of the piece. This type of jig is arranged in such a way that holes can be drilled in the work at two different angles. The jig is turned over on the legs, F, while the hole located by the bushing, D, is drilled. After CLOSED JIGS 271 HG. 123. BUSHING FOR AN OILrPUMP SHAFT this is done, the jig is turned over until it rests upon the legs, K. In this position, the drill is guided by the long bushing shown at G. As this bushing is so very long, it will be noticed that it is relieved to a size a little larger than the drill for a good pro- portion of its length. As the piece of work shown in this illustration is cylindrical in its general form, it does not make any difference how it is located radially, so that it is only necessary to slip it on to the stud and tighten the clamp screw, H, before starting the work. A drill jig of this kind can be used for many kinds of bushing work when oil holes or other holes of sim- ilar kind are to be drilled. It forms an excellent example of a simple type of closed jig. Naturally, such a jig is used on a drill press, either with a couple of spindles in which the different size drills m TOOLS AND PATTEINS are plaeed and used one after tlie other, or else a magic elin<;k or its equivalent is used in a single spindle machine, and sockets for each of the drills are provided so that one can be interchanged for the other while the spindle is in motion. Drill Jig for a Rod-Supporting Bracket. — ^The sup porting bracket for a rod or shaft, shown at A, Fig- ure 124, has been previously machined in a hole which extends entirely through the hub indicated. At the time when the hole was reamed, the end of the hub was also faced. In a subsequent operation the surface, K, was milled in a definite relation to the reamed hole. In the operation indicated by this jig, the work to be done is the drilling of the two holes, B, and also the one from the opposite side as indi- cated at 0. As the hole, F, shown entirely through the hub has been previously located from the milled surface, K, when it was machined, it is obvious that a loca- tion from the hole and the miUed surface can log- ically be considered as the correct method of locat- ing for the present operation. In order to support the flanges while they are being drilled, the two set- screws, E, operated by the workman's fingers are used. These set-screws are conical on the end, so that they set up a slight wedging action and liokl the work securely. The piece is slipped upon a locat- ing stud in the large hole, and after it has been damped against the opposite end of the hub by means of the C-washer shown at F, by the nut indi- cated, the set-screws, E, are tightened as previously mentioned. When drilling the holes, B, the jig is set CLOSED JIGS 273 274 TOOLS AND PATTERNS CLOSED JIGS 275 up upon the legs, D. When the hole, C, is to bo drilled, the entire jig is turned over until it rests upan the legs on the opposite side. This completes the drilling operations on this piece of work. This is one of the simplest types of jigs which can be devised, but it can be made to give^ excellent re- sults in ordinary practice. A point which should be mentioned in connection with a jig of this sort is that the surface on the jig shown at K should be so milled in relation to the center stud on which the work locates that there will be a slight amount of clear- ance between the surface of the piece and the pad on which it locates. A very slight amount of tipping may be caused when the thumb-screws, E, are tight- ened; but in actual practice this amount would never be sufficient to cause any trouble, so that the jig can logically be considered of good design. In addition, this jig is easily made and easily cleaned, and chips are not likely to accumulate on the locating point, thereby causing errors in locating. Jig for Automobile Hand Lever. — Sometimes an occasion arises to make a jig which can neither be considered an open jig nor yet a closed jig. Such an example is indicated in Figure 125. In this example, the jig is a kind of half and half type, and is not really one of the two types, but is midway between them. In this case, the work, A, is a hand lever used for operating a pull rod or latch on the brake lever of an automobile. Previous to the operation of drilling, the work has been milled on the surface, F, and it is therefore safe to use this surface as a locating point in the drilling operation. The piece, FIG. 125. JIG FOR AN AUTOMOBILE HAND LEVER therefore, is laid on the surface, P, in the jig as indi- cated, and is pushed over into a vee-block, D, by means of the set-screw, B. This set-screw strikes against a corner or fillet on the lever in such a way as to force the work into the vee-block and at the same time to throw it over until it strikes the end of the set-screw, 6. It will be seen that then the set-screw, G, acts as one side of a vee, the other side of which is formed by the thumb-screw, E. All of TOOLS AND PATTERNS the elamping action is aeeomplislied by means of this one screw in the case mentioned. Little difficulty is experienced in setting up the work for the operation and in obtaining a correct location. The work which is to be done in this setting of the piece is the drilling of the two holes, B and C, and the entire jig is set up on the leg shown at E, in the lower portion of the illustration, when the work is done. Bushings, natnrally, are provided at B and C to guide the drill and to insure correct locations for the hole. Nearly all of the jigs shown so far in these two chapters are made of cast iron, as this material lends itself to a variety of forms and can be made cheaply and quickly. But the same types of jigs can be bnilt up from steel if desired, and in the case of gun jigs and of jigs for use with a great many dull pieces, the steel built-up jig is to be preferred. Its cost, however, is prohibitive in anything but very large production. Drill Jig for a Bearing End*Cap.— When a piece of work has been previously machined and it is nec- essary to locate it for a drilling operation subsequent to the other operations on the work, it is essential to locate the piece by means of the finished surfaces. An excellent jig for a piece of work of this kind is shown in Figure 126. In this case the work. A, has been previously faced at B and has been recessed at C. It is necessary then to locate the work for the drilling of the four holes shown at F, by the previously finished surfaces. The method of doing this is to set the work upon a shallow stud or plate, CLOSED JIGS 277 ]S^2^ _ ^ « «. J„ H' i 1 ; • 1 • : n : 1 c no. 126. DIOU. JIG IW A BEABINa S£il) GAP locating it by means of the recess at C, and clamping the work by means of an equalizing collar, H, oper- ated by the thumb screw, K. In placing the work in the jig, the square side of the piece strikes against the two set screws, G, thus giving a sqnaring-up effect. It will be seen that the 278 TOOLS AND PATTERNS action of the clamp collar, H, is such that when the thumb screw, K, is tightened, the entire collar rocks sufficiently to permit an equally distributed pressure on the work. The thumb screw, K, is mounted in a strap, N, which extends entirely across the jig. This strap is slotted at L and M in such a way that it can be quickly removed when placing a piece of work in the jig or removing one from it. In operation the jig is set up on the four legs shown at D, and the work is slipped into position. After this is done the strap is put in place and the thumb screw, K, is tightened. The entire jig is then turned over until it rests on the legs, E. Bushings are provided at P to guide the drills to their proper positions. This type of jig can be used for many varieties of work of a similar character, the only variation nec^usary is in the manner of locating the piece and in little details of clamping, and so on. The type itself is a common one, the use of which can be adapted to numerous kinds of work of similar char- acter. Drill Jig for an Eccentric Bushing.— The eccentric bushing shown at A, Figure 127, is used as an ad- justing bushing for obtaining the correct relation between the worm and worm-gear sector of an auto- mobile steering gear. This piece of work has been previously bored and reamed at B, and has been faced on the end. The drill jig shown in the illus- tration is for the purpoae of drilling the hole, D, in the end of the arm as indicated in the illustration. The body of the jig is provided with feet, K, on 0Ij03£iD 11X08 280 TOOLS AND PATTBINS which it rests on the table of the driU press. The work is located on a short stud shown at C, and is clamped down upon the shoulder of the stud by means of the thumb screw, L. This thumb screw operates a square plate, M, which bears against the top of the bushing at E. The correct location for the arm in which the hole is to be drilled is assured by means of the thumb screw, F, which acts as a stop for the end of the lever, and also by the screw, G, which forces the work over against the screw pre- viously mentioned. A suitable bushing is provided at D, which is so arranged that it can be removed and replaced by another bushing of suitable size for the reamer. The method used in drilling and reaming a piece of work in a jig of this kind, is first to drill the work, using the drill-sized bushing, and immediately after this operation to remove the bushing and sub- stitute a larger one of the proper size for the reamer. This reaming of the hole sizes it correctly to the given diameter and produces a smoothly finished piece of work. The slip bushing shown in this iUustration is one of many types which can be used when it is neces- sary to remove one bushing and replace it by another, as in reaming a hole after it has been drilled. There is very little difference in the types of bushings, the essential point in design being that the bushing shall be so made that it can be easily and quickly re- moved and secured firmly when in position. Drill Jig for a Radius Bracket.— A somewhat odd- shaped piece of work which requires a rather pecu- CLOSED JIGS PIG. 128. DRILL JIG FOB A RADIUS BRACKET liar type of jig is shown in Figure 128, The work, A, has been previously machined on the surfaces, B and C, to the angle indicated. It is necessary, there- fore, to locate it by the previously finished surfaces, and also to provide an end location and clamp the work securely in position in the jig. The end loca- tion is assured by means of the stop screw, E, and by the thumb screw, Wm This thumb screw* F, is hand operated after the work has been thrown over 282 TOOLS AND PAOTBBNS into the position shown, by means of the screw, K, at the other end of the jig. The work to be done in this operation is the drilling of the hole, D, through the angular side of the piece, and also two other holes indicated at B. Suitable bushings are provided for all of these holes, as can be clearly seen in the illustration. The bushing used for the hole, D, is of the slip variety and is indi- cated at G. On the opposite side of the jig a bush- ing, H, is located for a counterbore which is used in one side of the hole; D. In operation the work is placed in the jig until the surface, B, rests against the angular part of the jig, after which the set screw, K, is used to move the work forward in the jig until it strikes the set screw, E. The thumb screw, F, is then brought up to make a contact and to assist in supporting the work, and the screw, N, is used to bring up the angular shoe shown at L, against the angular side of the work. The work itself rests on the set screws, 0 and P, and is clamped down by the screw at M. It will be seen that the position of the screw, K, is such that it tends to throw the work down against the stop and over against the two set screws, E and P. A jig of this kind is provided with feet on the sides opposite to all points which are to be drilled, so that the jig will have a firm foundation on which pressure can be brought to bear. In drilling tiie pece shown, the slip bushing, 6, is first used, and a large hole is drilled through the portion, D. After this the bushing is removed, and a counterbore of special shape is fed down through the CLOSED jias 283 liner bushing indicated. The jig is then turned over and the process is repeated through the bushing, H. In like manner the other holes are drilled by spindles in a multiple-spindle drilling machine, these spindles being arranged in proper location to give the correct spacing for the various holes. Jigs of this character are used for many kinds of work and can be adapted to suit different conditions. Drill Jig for a Crooked Lev^— The work shown at A, Figure 129, is a crooked lever, both ends of which are to be drilled and reamed as shown at B and C. In addition to these two holes, there is a smaller hole at F, which is to be drilled in the same setting of the work. For this operation the lever is placed in the jig through the open side and rests on the finished pad at each end. At the large end, the flat surface of the work rests on a fixed support, as indicated, but at the smaller end, B, the support is assured by means of the screw bushing shown at H. After the work has been placed in position, this screw bushing is jacked up by means of a pin placed in the holes shown at 0. The location of the work is gained by the V-blocks at E. It will be noted that the V-block at this end of the lever is fixed, but at the other end there is a floating member attached to the thumb screw, L, which also acts as a V-block locater. This is clearly shown in the upper view. After the work has been placed in position and located as mentioned, the thumb screw, D, is turned down firmly against the web of the lever. The work is now in position to be drilled, and the jig is turned over on the legs 284 TOOLS AND PATTERNS FIG. 129. OBILL JIG Wm A CROOKED liEVER shown at P and K for the various drilling operations involved. The principles involved in this jig are identical with those which can be applied to many other varieties of lever jigs. Naturally it is always neces- sary to adapt any jig to the work on which it is to be used, but the principles underlying the design of jigs of this kind are much the same, and suitable adaptations can be made for various conditions of work in the shop. Large Tnumioa Jig.— When the work to be handled is of large size and somewhat awkward in shape, it is sometimes desirable to hold it in some CLOSED JIGS 285 sort of Jig which can be easily loaded. After the piece has been placed in the jig, the entire mechanism can be turned over by means of a crank or other mechanical device, so that it will lie in the correct position under the drill-press spindles. Furthermore, a jig of this kind should be arranged so that several sides of the work can be drilled without removing the piece from the jig and without any necessity for more than one operation of clamping. A suit- able indexing device can be made, so that the accu- racy of the holes which are to be put in from differ- ent sides of the work can be assured without diffi- culty. A jig of the Mnd ntenlioiied is generally termed a trunnion jig. The possibilities of a trunnion jig are dependent on the number of sides of the work which are to be drilled. When the work is such that it must be drilled from four or five directions, it is possible to make a double trunnion jig which can be indexed in several directions to provide for the drill- ing of holes from several different angles. However, a jig of this kind is more or less complicated, and it does not always prove a profitable investment to make one unless the work is in sufficient quantity so that the expense incurred will be offset by the saving in the manufacturing time. Nevertheless, drill jigs of the trunnion type having a suitable bearing on which they can be swung, are more or less common. An example of a trunnion jig of this kind is shown In Figure 130. The work, A, in this case is a trans- mission-case casting made of aluminum and pre- 286 TOOLS AND PATTERNS m. 130. SZAMFUB or TRUNNION JIG fOB A TRANSHISSION CASE C0¥1R viously machined along the surface, C. It has also been drilled at two points for dowels, as indicated at By and these holes are nsed as locating holes for the work when the piece is being drilled. In locat- ing the piece, A, in the jig, the position of the entire jig is as indicated in the illustration. The work is {daeed in the XT-shaped easting, H, locating on the dowel pins at B. After it has been placed in position the latch, F, is swung down into position and the thumb screw, 0, is tightened to secure the latch. After this the two thumb screws shown at D and B are tightened to make the work absolutely secure in the jig. The piece is now ready to be drilled, but it will be noted , that the holes, J, which are to be drilled are in the under side of the work. The entire unit, H, is hung on two bearings at S, and these bearings are situated in the carriage, L, which is furnished with wheels, N, traveling along a track located on the bed of the drill press. An enlarged section of tlie diOSISD JIGS 287 track is shown at P-Q, which makes the construc- tion of this part of the jig clearly apparent. The purpose of the track is to provide a means of mov- ing the jig from one machine to another when one part of the work has been drilled by a series of spindles and another set of holes is to be handled on another machine. When the jig is to be indexed preparatory to drill- ing, the pull pin, K, is removed from the bushed hole indicated, after which the handle, L, is operated, thus indexing the entire jig by means of the gears shown at M. This indexing operation turns the entire jig over, so that it is in the correct position for drilling the work. An arrangement of this kind will show very satisfactory results when a high production is to be obtained on a given piece of work and when the piece is of such size and shape that it can not be conveniently handled in a single operation. By ar- ranging a track like the one indicated in the figurei and by suitably fastening this track on cradle cast- ings, like those shown at E, the round shaft, 0, makes an exceUent track used in connection with the grooved wheels. It is entirely possible, with an ar- rangement of this kind, to set up two or three ma- chines with properly-spaced spindles so that the jig can be rolled from one machine to the other with very little loss of time and without the necessity for more than one setting of the work. In this chapter an attempt has been made to de- scribe' a variety of drill jigs which are in common use, but it is eivdent that it is entirely out of the ques- 28aB TOOLS AND PATTERNS tion, in a work of this kind, to go into every matter of design in great detail. Enough examples have been given, however, to make the subject as clear as the space will permit and the examples given have been selected with a view toward simplicity and variety* CHAPTER XIX LUBRICATION OP CUTTING TOOLS lecessity of Lubrication.— If a man has an auto- mobile, a bicycle, or some other piece of machinery and wishes the machine to be at its best, the irst thing that he considers is the proper lubrication of the varions bearings so that the mechanism will run as smoothly as possible. Now, in cutting any piece of metal the question of lubrication also arises, for as the cutting tool is in constant contact with the metal which is being cut, it is obvious that a great deal of friction is produced. The friction heats the fool, and if the amount of heat generated is excessive, the result will be disastrous to the cutting tool and eventually result in its ruin. It is necessary there- lilre on some Mnds of material to provide a suitable cutting lubricant in order to carry away the heat generated by the friction of the tool and to make the work easier. Certain kinds of material do not require lubrication, but on others it can be used to great advantage. The question of lubricating a cutting tool is of so great importance that it must be thoroughly consid- ered. A great many points come up in connection with cutting lubricants for different classes of mate- rials. It is out of the question to attempt to prescribe 290 TOOLS AND PATTERNS LUBRICATION OF CUTTING TOOLS 291 a cutting lubricant which will be suited to any par- ticular kind of metal without knowing the exact nature of the alloy of which the metal is composed. Let us suppose that some one were to ask the question, "What is the best cutting lubricant for aluminum?" It would be difficult to answer this question abso- lutely without knowing of what alloy of aluminum the casting was composed. This reminds me of an anecdote which I once heard of two Englishmen who were in this country for the irst time and who were talking about the peculiar- ities of Americans in general. The two men were in a railroad station at the time, and one remarked to the other, ''They say that an American always an- swers a question by asking another one." "That seems very improbable," replied the second. **Well, let us see if this is really the case. I'll try it now." So he strolled over to tke ticket office and asked the ticket agent, want a ticket. HoW much is it?" And the agent replied, Where to!" So in the matter of cutting lubricants for different materials, if I were asked to state the type or* kind of lubricant best suited to a given material, I would have to ask what the composition of the casting was before it would be possible to name the proper kind of lubricant to use on the work. There is considerable difference of opinion among manufacturers as to what particular lubricant is bet- ter for certain classes of work. However, a variety of lubricants have been proved to give excellent results, and although the proportions of their com- ponent parts may vary somewhat, the ingredients themselves are very similar. In this chapter we will describe a number of lubricants which have been used with success on different kinds of materials. Although modifications of the formulas herein given may be found advisable in some cases, the ones given are thoroughly practicable for commercial purposes. Cromposition of Gutting Lubricants.— In the first place it must' be remembered that all materials do not require lubrication. Cast iron, for example, is not lubricated to any extent. (Some manufacturers have attempted to use various lubricants on cast iron, but I do not believe that the results obtained have been at all convincing. At any rate, cast iron is generally cut dry.) Brass is usually cut dry. Aluminum is sometimes cut dry and at other times it is cut with a lubricant. We have decided that the purpose of a cutting lubricant is twofold, one of the purposes being the lubricating of the cutting tool, thereby eliminating the friction to a certain extent, and the other is a cooling action intended to keep the cutting tool in such condition that it will not be ruined by too great heat. Now, in discussing the kinds of lubri- cants used for these purposes, we can consider that practically only two kinds of lubricants are in use. One of these is composed of lard oil or mineral oil, or of mixtures of mineral and lard oil. The other compound is of a soapy nature and was devised in order to provide a greater cooling effect than that obtained by the use of oil only; at the same time it carries sufficient grease so that it provides a certain amount of lubrication also. m TOOLS AND PATTERNS A solution of sodawater was formerly used as a cooling medium, but as this compound possesses little lubricating action it bas been gradually re- placed by other compositions carrying greater per- centages of grease. A number of solutions are on the market at present, and most of these are in the nature of emulsions. A saponaceous, or soapy, fluid is formed by means of potash, or soda, added to animal oil which is readily soluble in water. Li mixing a compound of this kind it is only necessary to dissolve soap in mineral oil and then add water sufficient for the purpose in hand. It is important in mixing a solution of cooling or cutting compounds for any kind of work to make sure that the action of the compound is not such that it will cut away the lubricating oil used in the bear- ings of the machine. Unless care is used in making a proper mixture, there is some danger of obtaining SO "sharp" a mixture that it will eventually remove all the lubricating oil from whatever portion of the machine it touches, and the natural result will be that the machine itself will be seriously injured through friction. The different compositions of cutting lubricants as used by various manufacturers are much the same, although their method of mixing and the various projKirtioMPiw the mgredients may differ somewhat. In general, the following formulas will be found to give good results, although the mixing of the compound may vary according to the amount of water which is used. Bar stock or machine-steel forgings caa best be LUBRICATION OF CUTTING TOOLS 293 cut with a mixture of lard oil, borax, and water, or lard oil or mineral oil can be used alone. Steel castings, and bronze or malleable iron can be cut to advantage with a lubricant composed of min- eral oil alone. A mixture made of half lard oil and half kerosene will prove the best for aluminum castings, and pro- duces a very smooth cutting action that is much better than kerosene alone. Kerosene alone is advo- cated by many manufacturers, but it is not equal to the lubricant mentioned. Wide-faced and forming tools seem to give better results when lard oil alone is used with them, and tools that are made of carbon steel seem to have longer life with this lubricant. Lubricating Compound for SteeL— An excellent borax compound for steel is made as follows: Dis- solve one pound of borax in seven gallons of hot water and allow the mixture to cool. After it has cooled, add to it one gallon of lard oil thoroughly mixed. Enough borax should be used to make the oil and water mix thoroughly. The quality of the lard oil used will affect the amount of borax, and hard or soft water will also make a difference in the proportions. The quantities mentioned are safe to start with, although slight variations may be needed to suit particular cases. A convenient method of mixing cutting lubricants of this kind is to use forty gallons of hot water to seven pounds of borax, mixing the solution in a fifty- gallon barrel. When the solution has cooled, seven gallons of lard oil can be stirred in, after which it is 294 TOOLS AND PATTBKNS ready for use. As previously mentioned, the greatest care should be used in the amount of borax, because too much borax has a tendency to cut away the lubricating oil used on the machine, so that trouble may be caused from imperfect lubrication of the machine parts. In general, however, it will be found that a tool will wear away more quickly when borax solution is used than if pure lard oil is used, but the cooling action on the tool is considerably greater with the borax water. CkKding by Lubrication.— The matter of cooling the tool and lubricating it at the same time is of so much importance that it is well to speak at this time of the particular necessity for proper lubrication when heavy cuts are being taken. As an example, let us consider that a piece of steel is being cut with a heavy feed and at about the maximum speed, and it is desired to select a suitable lubricant for it. As the friction produced by a heavy cut is so much greater than if the cut were to be a light one, it is apparent that in order to produce as good a lubricat- ing effect as possible it will be necessary to use an oil rather than a borax compound. But if the same piece of steel is being machined at high speed and the amount of stock which is being removed is not very great, the heating of the tool will be very much greater, and a borax solution will therefore be found to give better results. Another factor that is worthy of comment in re- gard to the use of cutting lubricants on machine tools, is the matter of power consumption. Author- itative data on this subject is difl&cult to obtain, but JiUBRICATlON OF CUTTING TOOLS ^ 295 as it is known that a machine will run easier with oil in the bearings, I am firmly convinced that a cut- ting tool will remove metal easier if it is properly lubricated. Experiments that have been made along these lines have been widely different in the results obtained, and to my knowledge no absolute tests under careful management have been made that give contradictory data. Lubiicating Stream to Remove Chips.— Another function which should be mentioned is the use of a stream of cutting compounds to wash away the chips that are generated by the tool. This item is more serious in some cases than in others. For ex- ample, take the drilling of a deep hole in a piece of steel: Here, at times, it is difficult to get the chips that are being rapidly removed out of the way, and they stick in the flutes of a drill or pack around a cutting tool in such a way as to interfere greatily with the proper machining of the piece. Let us take as an example a piece of steel which is being drilled on a horizontal turret lathe. Refer- ring to Figure 131, the work. A, is held m a special collet chuck as shown in the illustration. The turret lathe in this case is provided with a system for lubricating the tool through a pipe, B, which con- nects with the turret as it is indexed from one posi- tion to the other. The drill, C, is of the "oil type," that is, it has a hole through the center and two ducts which lead out directly at the point of the drill through which the cutting lubricant is forced by means of the pump on the machine. As the pump forces the lubricant to tlve drill, the high pressure 296 TOOLS AND PATTERNS 4|l IIG. 131. INTERNAL OILING ARRANGEMENT FOR DRILLING ON A HOftlZONTAL TURRET LATHE of the fluid tends to force out the chips as they are generated by the end of the drill, along the flutes, so that eventually they find their way to the end of the work and drop out. A method of forcing lubricants through tools used on the turret lathe is not uncom- mon, although the practice varies somewhat with different manufacturers. Boring bars are not as easy to lubricate as some other forms of cutting tools. Lubricating Through the Spindle of a Turret Lathe.— The device shown in Figure 132 was applied to a hclrizontal turret lathe in order to provide proper lubricating facilities for the cutting tools used in the inside work on the piece, A. The device was applied from the rear end of the spindl||||pit the pump used to force the lubricant to the spinffle was a component LUBRICATION OF CUTTING TOOLS pi HQ. 132. LUBRICATION OF SPECIAL NATURE APPUED TO A TURRET lATHE part of the machine. A reference to the illustration will make it apparent that a boring bar, B, is used to bore two diameters on the inside of the work, and is piloted by a bushing, C, in the chuck. In order to provide the inside cutting tools with proper lubrication, a pipe, D, is connected to the lubricant supply pump and is passed through the end of the spindle where it is guided in the packing bushings. Through the spindle and at the forward end, E, it is provided with a telescoping tube of smaller size, as shown at F. This smaller tube reaches forward and enters a hole in the end of the boring bar. Prom this hole other smaller holes lead out directly in front of the cutting tools. A coil spring takes care of the variations as the bar, B, progresses into the hole during the cutting action, and a stop collar, 0, limits the forward movement of the tube, F, as it strikes against the end of tie boring bar. The application of a device of this kind to a turret lathe is not costly, and the results obtained by its TOOLS AMD PATTBBNS LUBRICATION OF CUTTING TOOLS 2^9 use are very satisfactory. At different times I have made a number of equipments for oiling tools through the spindle, most of which have been on a similar order to th|M|| shown in this illustration. It is obvioufii tMHlKerent conditions require slightly different methods of handling, but the principles in- volved in the design are much the same in all cases* Fliiod Lubrication. — ^Nearly every machine of a manufacturing type is provided with lubricating devices of one kind or another, according to the type of machine and the nature of the work to be donel A turret lathe of the horizontal variety, for instance, is usually equipped with outside lubricating devices which will direct a copious supply of fluid against a piece of work that is being machined A milling machine is also provided with an outside supply system for furnishing cutting lubricants to the cut- ters and the work, and flood lubrication (which means an excess supply of lubricants) is the usual method. The production of work from machines which are provided with flood lubrication for the cutting tools is far in advance of that obtained from machines of the older type which had an inadequate supply of lubricant. In order to supply a machine with a proper amount of lubricant, or cutting fluid, and to direct the stream or streams to the proper position, it is necessary to arrange the piping in such a way that the spouts can be swung in any direction, longitudinally and vertically. By referring to Figure 133 an excellent 6xa»qple may he seen of the application of a cutting ^0. 133. OUmNO-IiUBRIGANT SYSTEM m A BWLA»D VERTICAL TURRET LATHE m TOOLS AND PAf TEENS lubricant system to a vertical turret lathe. This system is used by the Bullard Machine Tool Co. on their vertical boring mills and vertical turret lathes. A standpipe at one side of the machine contains two sliding tubes which can be adjusted vertically to suit the height of the piece that is being machined. These two tubes have spouts, A and B, and suitable cocks, ais shown at to cut off the lubricant or reduce the flow. It will be seen that the fluid can be directed immediately onto the work, D, without difficulty. One of the nice features of the device shown lies in the fact that the supply of lubricant is copious and can flood the work with a suitable cutting compound forced through the pipe by a pump located on the machine. After the cutting fluid has been used, it flows downwards and finds its way eventually through a fine screen back to the pump and is immediately sent forth again through the same channel to the work. CUTTING FEEDS AND SPEEDS A Careful Study Eequired.— In order to obtain maximum efficiency from any machine tool it is an essential point that the proper cutting feeds and speeds should be used. The question then arises as to what cutting speed is correct for any given kind of material with a given feed. It is evident that a very little difference in the cutting speed and a slight variation in the feed used on a piece of work will make considerable difference in the number of pieces of work that may be produced in one hour, one day, or one year. Let us suppose that a certain piece of work is being machined, and that the feed and speed are a little less than they should be. If it takes an oper- ator ten minutes to produce a piece of work at the feed and speed that is being used, then a reduction of one minute in the time necessary to machine the piece would mean a considerable saving in total pro- duction time. In order, then, that the maximum production should be obtained from any machine, it is evident that the cutting feed and speed should be very carefully studied. Definition of Cutting Speed. — The term cutting speed in feet per minute'' is not always thoroughly m 302 TOOLS AND PATTEKNS understood by the non-technical man. In order there- fore to make the matter more clearly evident to the reader a short explanation will suffice. Considered in elementary form, cutting speed means the nnmber of feet of metal, considered as a continuous strip, which passes a given point upon the edge of a cut ting tool in one minute. For example: Let it be supposed that I am planing a piece of cast iron 5 feet long, and that it takes me 10 seconds, or one-sixth of a minute, to make a cnt the length of the work. It is evident that the cutting speed which I am using is 30 feet per minute, because it takes one-sixth of a minute for 5 feet to pass the cutting tool, and six- sixths of a minute will elapse while 30 feet of metal are passing the tool, not considering the return stroke of the planer. In the same way a piece of cylindrical work which is revolving and passing a given point on the cutting tool, can be considered as a ribbon of metal unwind- ing from the outside of the work as fast as it passes the tool. In this case the circumference must be considered in determining the cutting speed. Let us assume that I have a piece of cast iron 20 inches in diameter which is running at a rate of 10 revolutions per minute, and I wish to know at what speed 1 anj cutting the work, and whether it should be decreased or increased, and how much. Formula for Determining Cutting Speeds.— -It is evident that the circumference of the work, multi plied by the number of revolutions per minute at which it is running, and divided by 12 (which is the number of inches in one foot) should equal the CUTTING FEEDS AND SPEEDS number of feet per minute at which the work is being cut. Or the solution of the problem would appear as follows: 20 X 3.1416 X 10 ^ 12 =52.4 ft. per mm. As this process is a rather tedious one, let us take an approximation of the necessary figures, and from them derive a formula. If we take the constant, 3.1416, and divide it by 12, which is the number of inches to the foot, we obtain the figure 0.262, or, in round numbers, 0.250. Then by substituting this figure, 0.250 (or y^), we obtain in place of the solution of the problem given above, another one: 20 X 0.250 X 10 = 20 X ^ = 50 4 While this is not exactly correct, it is near enough for all practical purposes. If we resolve the matter into a formula, then, we obtain the following: D X C Where D = diameter of work. N = number of revolutions per minute. , C = euttiiig speed in feet per minute. If we reverse this process in order to find the necessary number of revolutions per minute required for a piece of work of a given diameter to obtain a given cutting speed, we use the formula ^ ^ ^ %i 304 TOOLS AND PATTERNS TakiBg the same example as given above with the work diameter, D = 20; cutting speed desired, C== 50 feet per minute, then 4x50 — ^ — = 10 r.p.m. 20 It will be found that most of these formulas are very simple and can easily be memorized, so that all cutting speeds for any given diameter can be de- termined very rapidly by mental calculation. The number of revolutions required to obtain cut- ting speeds for given diameters can be found in any mechanical handbook, but such a book is not always conveniently at hand when it is desired to know what a cutting speed is for a certain class of work. In such cases the above formulas will be found of great assistance. Relation of Speed to Feed.— There are certain well- defined rules which can be applied to the correct set- ting of a feed and speed for a given piece of work when the composition and the quality of the work are known. An important factor in production work is the depth of the cut to be taken on the work. If a large amount of material is to be removed, and if, there fore, the depth of the cut is considerable, it is evi- dent that the amount of pressure brought to bear upon the tool and the amount of power required to pull tiie tool through the work are of first impor- tance. Speaking generally, the depth of the cut has a powerful effect on the feed which can be used and also on the speed. It would seem that there should CUTTING FEEDS AND SPEEDS 305 be, then, a direct relation between the cutting speed and the feed. That is to say, if a speed of fifty feet per minute were to be used and a feed of 1/32 of an inch per revolution of the work with a depth of cut of 1/8 of an inch, it would appear logical that if the cutting speed were to be changed, the amount of feed would need to be changed also. Just how much change a variation of ten or fifteen per. cent in the cutting speed would be required in the feed in order to produce the same results with the same amount of damage or injury to the tool, is a difficult question to decide. However, the amount of stock to be removed from a casting or a forging is, in the majority of cases, very nearly uniform when the work is to be put through the shop on an interchangeable basis. We shall assume in our discussion of cutting feeds and speeds, then, that the amount of stock to be removed from any given piece of work is according to the usual practice. Speaking generally, the larger a piece of work is, the more stock is left to be re- moved by the cutting tool, because on large work, variations in the casting are more likely to be found. On a piece of cast iron, six inches in diameter, the ordinary amount of finish left on the casting would not be apt to exceed % of an inch on a side. On work 30 inches or more in diameter, there might easily be from % to % of an inch of stock to be removed. It is very apparent, then, that in ma- machining large work the depth of the cut would need to be deeper and, therefore, the feed would not be apt to be so great. 306 TOOLS AND PATTERNS But there are other faetors which enter into the machining of any piece, and these factors sometimes seem to contradict themselves. In the machining of a large casting, 30 inches or more in diameter, with a depth of cut % of an inch, it might be entirely possible to take a feed even a little greater than would be possible on a small piece six inches in diameter. .The factors which would influence this matter are the power of the machine, the weight and rigidity of the work which is being machined, and the sectional area of the tool which is doing the work. The area of the tool would be proportionately greater on a heavy and large machine than on & small machine. Conservative Cutting Speeds. — ^It will be noted from the foregoing statement that the amount of feed and speed which can be used on a given piece of work is not by any means an absolutely fixed amount. Given, however, a comparatively uniform amount of stock to remove from a casting of a known degree of hardness, there are certain conservative feeds and speeds which can be used with safety. It is always necessary in making an estimate of production on a given piece of work, to assume a certain cutting feed and speed which has been found by long experience to be within the limit of safety. Assuming that the metals to be cut have been pickled or sand-blasted to remove any injurious scale that may be upon fheni prior to the machin- ing operaton, and further assuming that the amount of stock to be removed is not excessive, the follow- ing table of cutting speeds for different materials CUTTING FEEDS AND SPEEDS 307 will be found to give results well within the limit of safety. It is always well in making an estimate of production on a given piece of work, to assume that the work is normal and not very hard, and that it has no excessive material to remove. Under these circumstances, after an estimate of production has been made, it is easily possible to speed up a ma- chine slightly in order to gain a little in production, providing the material which is being cut proves to be of such a quality that it permits a little higher speed than normal. Cast iron — 50 feet per minute. Cast steel — 60 feet per minute. Malleable iron— 70 feet per minute. Machine steel forgings (15 to 20 point carbon) — 65 feet per minute. Machine steel (black stock) — 70 feet per minute. Tool steel forgings— 35 to 40 feet per minute. Sted alloys (containing nickel and chromium)— 30 to 50 feet per minute (depending on alloy). Yellow brass— 200 feet per minute: Composition brass— 120 to 150 feet per minute. Bronzes— 30 to 80 feet per minute (depending on alloy). Importance of Proper Speeds and Feeds.— The im- portance of a correct cutting speed and feed cannot be overestimated. It is safe to say that the afHHW manufacturer loses more money in the course m a year by incorrect setting of speeds and feeds in his factory than by any other single item in his total outlay. A number of reasons are responsible for this, but probably the most usual one is the fact that no work- 308 TOOLS AND PATTERNS CUTTING FBBDS AND SPEEDS ao9 man likes to grind tools. If a workman has a num- ber of pieees of work to do on a maehine which re- quires rather careful ** setting up," he is quite apt to run his machine a little too slowly so that it will not be meessary for him to grind the tools* very often. It is the duty of any foreman of a department in a factory, to make sure that the production time on the work in process is as great as the nature of the work will permit. It is furthermore the duty of the progressive executive to make certain in his own factory that he is obtaining the results that he should obtain by making a personal examination of the methods in use from time to time, and to keep himself posted in regard to the work, so that produc- tive inefiSeieney shall not be laid to a lack of knowl- edge on his part. Allowance for Exceptional Cases. — ^While it is all very nice for a tool engineer, an executive, or a fore- man in a factory to determine positively beforehand exactly at what speed any piece of work must be run, it is an entirely different proposition to tell the man in the factory who is doing the work that h^ must mn that work at exactly the prescribed speed and feed. Getting back to first principles, it would be entirely possible to fix absolutely every cutting speed and feed in the factory, providing the material which was being cut were exactly of the same quality in each and every case. Unfortunately, however, foundry practice is not such as to give abso- lutely certain results. Sometimes a group of castings will be fopad very hardi while in other cases they will be soft. It is evident that the first group cannot be machined as rapidly as the second. In these days of rapid production and high speed, it frequently happens that several patterns are made of the same piece of work, and in order to obtain the castings as rapidly as possible, the patterns are sent to different foundries. Invariably the castings from one foundry will differ in some respect from those of another foundry, and due allowance in set- ting speeds and feeds must be made for such condi- tions. So also in the case of alloy steels, a very great difference may be found in two lots of forgings, al- though in this case the trouble is not caused by the composition as a general rule, but is more likely to be the result of an improper treatment of the forg- ings after they have been made. The remedy for conditions of this kind is apparent. It is certainly not the part of economy for the manu- facturer to reduce his production speed just because a foundryman or a drop-forge department has made errors, or has neglected to do some of the things that should have been done before the castings or forgings were delivered. However, it may happen that the manufacturer does not feel disposed to send back a lot of imperfect or improperly treated castings or forg- ings, and prefers to machine them as they are. In such a case he will have to establish arbitrary ma- chining speeds, and his decisions must be governed by the conditions. Effect of Lubricant on Feed and Speed. — ^In the previous chapter the matter of cutting lubricants was discussed and various data were given in regard 310 TOOLS AND PATTllNS to the most suitable lubricant for various classes of materials. In tool-room work, however, it is very often the case that the workman does not wish to use a lubricant in cutting a piece of metal. This is largely because the use of a lubricant results in much dirtier work, which is difficult to handle. Hence, the toolmaker prefers to cut his work dry as a gen- eral thing. There is no particular reason why a workman on this class of work should not use his own judgment as to lubricants. He might be able to produce some classes of work more rapidly by using them, because he could use a little higher speed and a little more feed, but in the long run no par- ticular gain would be found. Of course, in making heavy roughinqo^ cuts in the tool room, or anywhere else in the factory, a lubricant will undoubtedly be found of great advantage. In the table given pre- viously in this chapter, it is assumed that a proper lubricant is to be used on work which needs lubrica- tion. General Rules.— Speaking generally, the amount of feed and speed to be used for any work produced in quantities! should be as great as the work will permit without obliging the workman to re-grind his tool more than three times in one day. Naturally, there are exceptions to this rule, but as a general thing if the workman is not obliged to grind his tool oftener than once a day, he is losing time in produc- tion. But, on the other hand, if the workman finds it mmmmm to re-grind his tool about once every hour, Wtrnmre indication that the speed is too rapid or the feed is too deep. CUTTma FEEDS AND SPEEDS 311 I recall a rather peculiar incident connected with the use of the proper cutting speed and feed that hap- pened some years ago. In passing through a factory, Tworkman stopped me and asked if I could tell him what kind of steel he could use in place of the tool he then had. On questioning the man it appeared that he was grinding the tool after he had produced about two pieces, and this tool grinding kept him busy for some minutes each time. On examining the work, I found it to be a piece of bronze about 4 inches in diameter. The workman proceeded to cut one of the pieces while I was standing by his side. 1 noticed that the speed seemed to be excessive, and by counting the number of revolutions per minute, i saw that he was running the work at something over 600 feet per minute. As the work was a piece of manganese bronze, it is evident that the tool was being ruined about as fast as he could ^^f^^ After he had reduced the speed to about 100 feet per minute he had no further difficulty with the tool. This example simply illustrates conditions which sometimes obtain in a factory on account of the igno- rance or carelessness of the worker. As it is absolutely impossible to set a cutting speed or feed for a piece of work without making a trial to see whether the work is hard or soft, it t>f ooves every factory manager or executive to see that the greatest care is used in making these determinations. After the speeds and feeds have been set as nearly correct as possible, it is well to make an examination to prove that the results show that the work is being produced to the best advantage. The foreman should S12 TOOIiS Am PATTERNS test the various maebines from time to time in order to make sure that the maximum efficiency is being ob- tained. For, next to proper cutting tools, speeds and feeds are of first importanee. In order, then, to see that the factory is obtaining the maximum output, all these various points must be considered, and each one must be planned in such a way that there will be mo loss either from incorrect handling, from improper setting of tools, or from incorrect speeds and feeds. When all these matters have been looked into by the proper men, the executive can feel assured that he is obtaining the full capacity of the machine, and when he has done this he has approached closely to max- imum efficiency. CHAPTER XXI PLANNING AND LAYING OUT WORK # Business Aspects of Planning.— If a man were about to build a house, his first step would be to de- termine what kind of house he wanted. He would devote considerable time in sketching out certain ar- rangements of rooms, and after he had determined about how many rooms he wanted and how much he wanted to pay for the house, he would take his sketches io an architect who would draw up a set of plans from them. After the architect had planned the house carefully, he would make an estimate on the cost of the various building operations. That is to say, he would estimate the amount of excavation required for cellar and foundations and the cost of all other matters connected with the actual building. He would then submit his plans to a number of car- penters and builders and obtain bids from them.* At least, this is the procedure that would be fol- lowed by the average man; but here and there one will find a peculiarly constituted individual who, quite probably, would take his rough ideas to a car- penter and say, **Here are some ideas of a house I want built. Go ahead and build it like that." The resulting house can readily be imagined. * Full discussUm of the mechanism of planning wiU be found in l^lanning and Time Study, hy O. S. Armstrong, Factory Management Course. 813 TOOLS AND PATTERNS In any kind of business venture involving the out lay of a number of dollars, a business man would be sure to investigate thoroughly all matters connected with the project. In fact, in any buying or selling proposition, the man whose money was to be used would be apt to look up every point in connection with the spending of his money. So also in the manu- facture of any kind of product, it is of the first im- portance to study the methods of production that are to be used and to plan carefully in advance all of the operations necessary to complete the various parts for the finished product. The importance, then, of the planning department in manufacturing can readily be seen. It would cer- tainly be the height of folly for any manufacturer to go ahead and obtain a great number of castings, forgings and other material from which the various parts were to be manufactured, and then, without further thought about the matter, to put these parts out into Ms factory without any particular plan or scheme of operation in his mind. And yet in many cases, especially in old-established factories, the mat- ter of planning and laying out the various operations for any given piece of work is almost entirely neglected. It is true that the operating official, in cases of this kind, depends largely upon his foreman and workmen to step into the breach and produce a finished piece of work which resembles the mechanism which he is attempting to build. In the progressive factory, however, the planning department receives the most careful attention, and the .men who are at the head of it are specially trained. In addition, their PLANNING AND LAYING OUT WORK 315 long experience enables them to plan in advance every detail of the work to be done. In no other way can the greatest efficiency be obtained from any fac- tory, and although the outlay necessary for a well organized planning department is fairly large, the results obtained more than offset the expenditure. One of the best examples of careful planning can be found in the Ford Motor Company plant in De- troit. Were it not for the care and forethought which has been used throughout this factory, it would have been impossible to obtain the tremendous pro- duction of these Ford cars. Tool Engineering Methods. — The importance of tool engineering has only recently been brought to the at- tention of the manufacturer. A few years ago the tool designer in a factory was supposed to lay out the various operations on the work which was to be done, but this laying out of operations was in the main a rather unfinished procedure. It is true that the old-fashioned tool designer would make a rough layout of operations necessary to complete a certain piece of work, but he would not go into the matter very thoroughly. The method used by the modem tool engineer, however, is such that every point in the manufacture is taken up with the greatest care and nothing is left to chance. All the operations which are to be done on the wojrk are simply planned in accordance with the equipment of the factory. More than this, the equipment (if it is insufficient to do the work required) is added to, in order that maximum efficiency on the work in process may be obtained. 316 TOOLS AND PATTEBNS The matter of planning is of such great importance that I intend to take it up in this book in consider- able detail I believe that the best way to describe the methods used and the processes which are ap- plied by the tool engineer, is to describe the various steps which are taken. In order that the subject may be as dear as posmblcy let m assume that a modem factory, very well equipped with machine tools of good design — one which has been used for automobH work — ^is about to proceed with the manufacture of a new model, and that the drawings of the complete mechanism have been handed over to the tool engi- neer ready for him to design the tools and fixtures for the work which is to be done. Let us also assume that the tool engineer has been employed by the same company for several years, so that he is thoroughly familiar with the machine tool equipment. Let us follow the steps taken by the tool engineer in this work, noting the various points of impor tance, which will be discussed at length later in this chapter. Let us assume, then, that the tool engineer has a pile of blue-prints on his desk — ^he picks up one of the important pieces (usually one of good size and considerable importance), and takes up the points logically about as follows: 1. — ^Looks over each blue-print, compares it with the assembly drawing, and notes the important fits, the relation of the piece in question to the other parts of the mechanism, and so on. 2. — ^Makes rough notes of the various operations necessary for the completion of the work. 3. — Looks over the machine-tool equipment of the 817 factory, to see what machines are best adapted to produce the work necessary. 4. — ^Determines the jigs and fixtures needed in the work of production, notes gauges necessary, and also the accuracy required for the various fits. 5. — ^Lays out the operation sheet in detail. 6. — Makes rough pencil sketches of jigs, fixtures and other tools necessary in the production. 7. — ^Makes layout sheets. 8. — ^Makes time-studies from layout sheets. 9. — Designs jigs, fixtures, and special tools, together with gauges needed for the work. 10. — ^Notes number of machines required, deter- mined by the time-studies made for the various oper- ations. 11. — ^Tums over the time-study sheets to the cost department, in order that piece-work prices may be set from the estimated time of production. Now these various steps which are taken by the tool engineer are not all undertiiten at once, but ap- proximately in the sequence just given, although the practical engineer is often able to combine several at a time. Let us now take up each of the points in detail. 1: Preliminary Processes. — Now in the first step which the tool enginetftalkiikes, he makes a rather rough analysis of the work which is to be done, but he does try, in this preliminary inspection, to grasp the im- portant details of the construction and obtain a very good general idea of what lies before him. In addi- tion to this, he familiarizes himself with the general TOOLS AND PATTERNS points in the construction of the mechanism which he is to build, by an inspection of the assembly draw- ings. He studies these assembly drawings carefully, in order to learn the general construction of the en- tire mechanism of which the piece shown on the blue- print that he is examining, is a component part. He notes very carefully whether certain of the parts should be a tight fit, or whether they should be a sliding or a running fit, and he determines the im- portance of their relation to the entire mechanism. After the tool engineer has gone over a few pieces of work in this way, he begins to form a very good idea of the work which he is about to do. He is now ready for the second step in the process. 2: Preliminary Layout of Operation.— Taking up the piece now in detail, the tool engineer roughly plans the operations which are necessary for the comple- tion of the work, and makes notes in pencil in the form of a memorandum, by which he is guided when he makes the more serious, careful planning. For example, he makes a note to this effect on his mem- orandum pad: **This piece must be chucked, the hub must be turned, and the inside must be bored out on a turret lathe. The other end of the work also must be fiiiished and turned, requiring another screw-ma- chine or a turret-lathe operation. There are to be six drilled holes around the flange of the piece, and these must be bored in a drill jig on a multiple- spindle drilling machine. There are also several other operations of milling and counterboring, and perhaps even one or two besides these." In any event, the tool engineer's memorandum on this work will FhANNWQ AND LAYING OUH WOEK 319 cover everything which is to be done to the piece, hut it may be that the operations, as noted by him, may not be in the sequence to produce the piece to the best advantage. This matter will be taken up later as the careful layout of operations is made. 3: Kadiiiie-Tool Iquipment.— Now it must be understood that although the points mentioned are given in sequence, in reality often, as I have said, many of these points are taken up by the tool engi- neer at the same time, since he is trained to this kind of work, and therefore when he thinks of a piece of work or an operation which is to be done on a given piece of work, his mind automatically selects the type of machine which, in his estimation, is most suited to the work in hand. He also is pos- sessed of a knowledge of the various machine tools which the factory has on hand, and knows something about their condition and their adaptability to cer- tain classes of work. It is obvious, however, that in a large factory the tool engineer cannot carry all of these details in his mind, so that it is necessary for him to have a complete record of the machine tools contained in the factorv. This matter brings us to the point of a reference machine-tool index, whieh every progressive tool en- gineer must have. The amount of detail contained m a record of this kind is governed by the size of the factory and the kind of product which is being manufactured. It is evident that in a small factory It would be comparatively unnecessary to have a de- tailed record of every machine tool in the shop, with Its feeds, speeds, and other data regarding its capa- 320 TOOLS AND PATTERNS eify. But it will be fomid that in a large faetory detaik of this Mud are of the greatest importance. For work of this sort, then, the progressive engineer in a large factory endeavors to make his index of machine tools as complete as possible. I have found in my own work of tool engineering, that a large card with an outline of the machine tools upon it, in at least two views, and with various data con- cerning feeds, speeds, and capacity,* is of the great- est valne. I believe that a card is much better than a loose-leaf book, because the card can be taken out of the file and used as a reference by the tool de- signer without disturbing other data which may apply to other machines. Perhaps a still better scheme would be to have the data on the various machines drawn up in such form that it can be blue*printed. It is apparent that if a blue-print were to be made there would be little danger of any cards getting lost and of the conse- quent large amount of labor to accumulate the in- formation | DCSCRIPTIOt* OF OPERATION TYPE Of MACHIN J. DEP1 ■ OR FIXTURES No. CAGES dm N< 1. Pen 1^ 90 W & IN c* - % / /; r 2 In f 1 trn 1! " S-i/ - — ■ ^ ' > tn * «^ 7 ^ f*f.Jtr t d /» r t-» ^ttfl £Um» 'J' «r Mr w m n // I '^'^ %^ «^;-- i WG. 135. TOOL AND OPERATION SHEET ON A CAST-IB0N PISTON— J*OUA PI£G£S F£R UNIT PLANNING AND LAYING OUT WORK 325 of the tool engineer in this respect, were to stop for a moment and think that every word written on the sheet represents the most careful tiiight, and that only as a result of a number of years of hard ex- perience has the tool engineer acquired the knowledge and skill necessary in the laying out of an operation sheet — ^then the executive would acquire a more wholesome respect for the tool engineer and for his work. It is only recently, as I have said, that the executive has been abk to see the value of prelimi- nary planning as carried out and brought to com- pletion by the experienced tool engineer. Therefore, to the executive who has not reached this point, and who still seems to consider that this work is more or less of a **cut and dried" proposition, I would recommend that he reconsider his attitude in this re- gard and give the tool engineer the credit to which he is entitled. In the first place, an operation sheet in itself should be made in such form that it gives all the information necessary in regard to the tool equip- ment and the machines necessary to do the work. I have laid out a number of operation sheets for different firms and on various classes of work, and I have found that a sheet similar to the one illus- trated in Figure 135 is about as complete as any- thing of this kind can be made if the sheet is to be of a size to allow of binding in a loose-leaf holder, for ready reference. The form indicated is preferably about 14x17 inches in size, but it can be made a tnfle smaller if desired. It is bad practice, how- ler, to endeavor to make a sheet of this kind very 326 , TOOLS AND PATTERNS small, as the necessary infonnatioB cannot be in- cluded on a sheet of mnch smaller size than that just mentioned. Referring to the sheet shown in the illustration, the reader will see that the data con- tained on it is complete to the smallest detail. At the upper left hand comer a small scale drawing of the piece appears, in order that a reference to the various operations may be made by means of letters, as indicated. Generally the drawing of the piece can he made about one-quarter scale, but on very large work it may be advisable to leave a larger space for the outline drawing. This matter is largely determined by the class of work which is to be done. I believe that the form shown gives every essential detail in regard to any piece of work which is to be manufactured, and forms a complete record > which can be referred to at a moment's notice. If desired, the operation sheet can be printed on tracing paper, and afterward blue-printed so that any num- ber of record proofs can be made. It will be seen that a reference to a sheet of this kind will give the executive or the tool engineer all the information which he needs, from the process used in manufacturing the product, down to and in- cluding the type of gauge needed and the drawing number of the gauge, or of the tool, jig, or fixture. In addition to this, the estimated hourly production per machine is given in the ''Remarks" column, and the number of machines which are required for what- ever production may be determined upon before- hand. The "Remarks" column also has a little additional space, which can be used for any data PljANNINe ANB LAYINO OUT WOEK 327 in addition to that for which space is provided in the tabulated list. After the tool engineer has gone into the matter of machining the work, and has laid out the operations, the tool designers use these sheets to work from, and as fast as the drawing numbers have been ob- tained from the clerk, they are entered up in their proper place against the tool or fixture which they represent — ^so that before very long, the record is complete. When this point has been reached, the sheet should -be either blue-printed or copied, and an original should be filed away in a record book, from which no sheet must ever be taken for any pur- pose whatsoever. If it is found necesary at any time, during the progress of the work, to make a change in the method of handling, a record of the change which is to be made should be filed in a separate book devoted entirely to this purpose. A statement of the reasons for the change should be embodied in the record, and the authority for making the change must also be given. It is not an uncom- mon thing for an operation sheet for a difficult piece of work — like a crank case for an automobile, or a receiver for a military rifle — ^to be worth several hundred dolars in actual labor expended on the plan- ning of the operations shown on the sheet. It is therefore evident that it behooves any factory execu- tive to see that the greatest care is taken in regard to these points. In laying out the operation, the tool engineer goes into every detail of manufacture carefully, as will be seen if the illustration is referred to. At the 328 TOOLS AND PATTERNS /*'■ Tu/HterfAce Sizm - O I'ftn Chuck - 1 /ieq Dira. /to Mode by PMJ I- Rouqh Taming Tool / Rftf Std 4- Radi'us Tool ■ l lfeeq Di^-N^ HH 7- Rough Boring Tool- I fftq l>¥fM0>t9 S- Finish Boring Tool- I RtQ-DwaMltOi 3-Sizinq Bar- l-Req Dwg.fh. ISiO Kh Sizing Tool ■ '-^eq Dr»g Ma Ii20 Ih Rough Facing Tool - 1 Req Std. a- Holder- ? Req Sid. for 2A -HkJS. J.L rS Fixlure for Drilling ■I Re^Omif.mia H- Drill • i Req 20 Dia is- Jig for Cenfenng ■ I- Req. Dwg. HOi W BLANK MOTOR COMPANY TOOL LAYOUT FOR PISTON li"^ To 6'" OPERATIONS OukrBv ho 166-1-6 scMx rN--€™ PLANNINa AND LAYING OUT WOBK 329 tiinTM O^mATiOM CLCVtHTM OfrltATIOI* 1- Rough OoasSMt Block- hHtq. Dig. Ak OH ^-"^ ■ ^ 2- Rouqh Ortoiing fyol-3-Ht^ Dtn. Me /37S J- Knish Turning T99I • l-Rwg. SM 4- fmisM lUonts taol - i-»ig. Omf.ma» 5- Omrtmad Turr»t AHoOt- Std Ar *4 lint MX 6- Turmng Stem - sid. for '4 Unh. MTi A 1-Cenlmr- I Rtq D»ig.Mo.l3n i- Dram Bock Chuck- IRt SO 96'%7 I5%f 48 0.O4O Size * * t *■ t * * 1 Attow fyr 5»/ tf/r m*el nmonnq work, indrxf r*q etc. /4 4 so 2S0 0005 2 Altmr iSfr st^u^ontl rmnovmg wwrk. ckemtmgi Jig 9 ic 1 3 6 Center End (C> Sens Dr. so 12 500 i AUow for setup ami rtmowng irork: c/eamnt 7 Finish Turn (A) V MS. 50 130% 48 0.040 Rough 6nored — 40 m 6% 36 0.006 1 Finish • tB) m 50 m 6% fi 0.006 Form ffod. fO • 30 m 1% 28 Hand 1 2 Aiiotv for setting ami removirtg, indexing andgoging 2 8 Rough Bore Co/bum 50 22%, 58% 250 0.010 / '4 Finish Bore < F> » SO « m m »• / Ream f /\> m 30 m ISO Horul i Altow for rwnomng and iftaerfing foo/s am i work 2 S 9 Pri// SensDr SO sm i I Allow for rtm^vmg €m i inserting » rork >4 \'i 9A Drill 12 Holes < H> SensDe 60 ts% exiz 4000 Hand ti Al/0¥f for indexing, S^ffirrg and ren ) Orind Q.a (A) Norton 4000 13 0 900 oooos meoi s Allow for wMngmtdremomtg work, gaging etc. 6 II ^Benck mm kdnd fi no. 138. TIME-STUDY SHEET ON A QJS&T-JSm Vmm TOOLS AND PATTERNS It is entirely possible for an experienced man to determine very closely the mnpunt of time which will be required for the performance of a given operation on any piece of work. His experience will tell him approximately what feed and speed can be safely used on the work, and as he can easily ascer- tain the length of the surface which he is about to cut, the time can be quickly estimated. A very good illustration of a time-study sheet is shown in Figure 138; it will be noted that various columns are pro- yided for the different data used in connection with the estimates. The time-study sheet itself is self- explanatory. Now let us take up the method of figuring— :or per- haps we should say estimating — ^the amount of time for a given piece of work, as indicated by the layout sheet. If the tool engineer is about to figure the time necessary on the work, his first step is to deter- mine the rate and settle the matter of cost of the tool. The best method of holding the work must al- ways be determined, and also the points from which the piece is to be located. Other matters in connec- tion with the design of tools and fixtures have been taken up in the previous chapters. 9: Machine Tools Required. — ^After the time-study sheet, mentioned previously, has been made, the amount of time necessary with each machine can be easily determined, and in order to make sure that a sufficient number of machine tools are at hand to give the production necessary, and within the proper time, a record must be kept to show how many pieces are to be handled by any one type of machine, PLANNING AND LAYING OUT WOEK 335 and how much of this machine time will be needed. The best way to determine whether the requisite number of machines is available, is to make a tabu- lated list of the various machines in the factory, and after the time-study sheet has been mde, the amount of time which each piece consumes on a given type of machine can be tabulated in the Ust mentioned. In this way, as the work of the tool engineer progresses, it is very easy to see when any one machine or type of machine is overloaded. Then, when it is found that a certain type of ma- chine has more of a burden than it can reasonably be expected to sustain, some of the work which has been placed upon it can be transferred to some other type of machine adapted to the work. By using a process of this kind, and by carrying all these mat- ters along together, the matter of distribution of the work in the factory can be adjusted to the best ad- vantage. The last point can now be taken up by the tool engineer. 10: Setting Piece-Work Prices.— The matter of set- ting piece-work prices does not strictly come under the head of the tool engineer's work — the time-study sheet for the various operations on each piece of work is used by the cost department in obtaining a basis upon which to figure the cost of production. If the work 01. the time-study sheet has been carefully done, the piece-work prices can be determined with great accuracy by the cost department, and the prices so set will be found to give excellent results. If, after a test has been made of the production time as wwlicated by the time-study sheet, there is found TOOLS AND PATTERNS to be a considerable difference in time, then the mat- ter should be immediately referred to the tool engi. Beer for Ms attention. If it should be found that an error has been made in his estimate of produc- tion, then the piece-work price may be changed to allow for the error On the other hand, if it is found that the workman is really consuming too much time in doing the work, the matter of speeds and feeds which he is using should be carefully looked into, in order that the source of the trouble may be deter- mined. Often I have found that the only reason why the production time did not check with the time-study, was that the operator was not using the speeds and feeds whieh would produce the best results. There are, of course, exceptional cases in which the work is of such a nature that the speeds and feeds wliicli have been estimated upon cannot be used, but if this eontingency occurs it is time for the factory super- intendent or the general foreman to step in and find out why the castings or forgings are not what thsy diould bOt CHAPTER XXII ESTIMATING COSTS Time Factor in Estimating Ck>sts. — The problem of estimating costs of manufacturing work is one which is of interest to every manufacturer. In some eases a small factory is engaged in the building of jigs, fixtures, or other tools for outside concerns, and in many cases the firm which is doing the work is com- pelled to submit a bid in competition with other factories. It is therefore of the utmost importance to make sure that the bid which is submitted to the customer, is such that it stands a fair chance in the competition with the others. In order to make sure that the prices which are quoted to the customer are reasonable and proper, and at the same time that the estimate submitted is made with a wide enough margin to give a substantial profit to the manilic- turer, a careful estimate of the time necessary to produce these Tarious pieces which are to be made, is a very important factor. Broad Experience Necessary. — This is one way in which the estimating of costs can be applied, but there are other applications which are fully as im- portant. Let it be supposed that a manufacturing concern is about to submit a bid for up a large number of pieces which are componelits of a 338 TOOLS AND PATTERNS military fifle; or that a great number of shrapnel shells are to be made, and that the bids which are to be submitted are in competition with those of numerous other manufacturers who are looking for the same work. It is very evident, then, both that the maniifaetiirer who intends to do this class of work should be well prepared as regards his mechan- ical equipment of machine tools and shop tools, and also that his engineering- force be well fitted to make estimates of production and of the costs of machui- ing. In the first place, either of the proiwsitions mentioned requires the services of men who have had long experience in the shop, and also in the planning of operations for work which is to foe done in quan- tity. Let us take the case of the factory which is pre- pared to build jigs and fixtures. It is much more difficult for a concern of this kind to make an esti- mate on the cost of a jig or fixture, than to estimate the production which can be obtained for certain pieces of work which are being put through the fac- tory in large quantities. In the case of the manu- facturing of jigs or fixtures, the work must be re-set a number of times during the process of manufacture, and every precaution must be taken to insure accu- racy. All these operations take a certain amount ot time, the exact amount depending largely upon the skill of the tool-maker. It is therefore difficult to estimate this class of work as closely as the other kind mentioned. In the case of the manufacturing of a great many parts of the same kind, it is entirely possible for ESTIMATING COSTS the manufacturer to provide means of holding and locating the work for the various operations which are to be done upon it in such a way that the parts will come to the desired size almost automatically. It is a matter of judgment. Unless the man who is selected for making estimates of this kind is one of broad experience, unless he has had a number of years of actual shop work, together with considerable experience in the actual engineering processes, and unless he has a logical mind, he is very likely to make a complete failure of estimating the cost of work which is to be done. Usual Causes of Failure. — ^If a jig or a fixture is to be made up, and there is a drawing from which the estimate can be made, the estimator can proceed to take up the various machining operations which are necessary to complete the piece of work, and can jot down the amount of time which he thinks it would be necessary to consume for the various operations, always remembering to make- due allowance for the time lost by the tool-maker in looking up tools and in setting up the work preparatory to the machin- ing. Allowance must also be made for careful measuring, in order to insure proper accuracy in the finished product. It will be readily seen that in order to do this kind of work the estimator must be a man who has actually done the work in the factory, in order that he may know exactly how a nmn would be obliged to go to work to do the necessary ma- chining. The usual causes of failure in estimating a piece of work such m that mentioned, are that . sufficient allowances are not made for the setting 340 TOOLS AND PATTERNS up and the getting ready to go to work, as well as for time which the man consnmes in actually making the fixture. Secret of Estimating Costs. — ^Briefly stated, the entire secret of estimating costs of production lies in allowii^ a man sufficient time to do the work, remembering at the same time that there are little incidental things which tend to increase the time neeessaiyy because of a failure to find a certain tool that is wanted, or owing to difficulties that arise when castings or forgings are not made in exactly the right way. All these points must be taken into consid- eration by the estimator, and the time allowance must be made on an hourly basis. The amount of profit which is to be made by the manufacturer is depend- ent, to a great extent, upon the overhead expense in the factory. There are many other items, also, which must be considered in making up an estimate of the cost of production. Among them are the matter of the cost of material. In some cases the jig or fixture is made of cast iron, and the pattern is to be made by the same person who is to build the fixtures. In a case of this kind, it is obvious that the pattern-maker's time must also be charged against the account. Also, the amount of stock and flie weight of the cast iron which goes to make up the jig, together with the cost of the iron in the jig, must be taken into consideration. Skilled and UnsldllBd LalNir.— Due time must be allowed for the hardening of any parts of the jigs or fixtures which are to be hardened, and it must also be remembered that after a part is hardened, it is ESTIMATING COSTS 341 usually necessary to grind it, in order that the dis- tortion caused by the hardening process may be re- moved and the piece may be properly fitted. Of course there are some parts which may be hardened without affecting the jig or fixture in its vital points in the proce8«-for example, snch things as the heads of screws or their points, a C- washer, a lever, or some other part of minor importance. No mat- ter how small the piece of work may be, however, it must be considered in the making of the jig or fixture, and if there are a number of pieces of the same kind (such as locating pins or something of similar character), several of these pieces can be made up at the same time by a boy or an apprentice, or by a comparatively inexperienced man. This being the case, the time for these various pieces need not be charged against the work at as high a rate as that charged for some of the actual tool-making. As a matter of fact, it is customary, in factories which do a considerable amount of this kind of work, to portion out such parts as can be made by an inexperienced man, and thus obtain the benefit derived from a cheaper rate of labor. In cases of this kind, the man who roughs out the part leaves a certain amount of work to be done or completed by the tool-maker, doing only the crudest part of the work himself. No Hard and Fast Rule. — There can be no definite rule which a man can follow in estimating costs for work of this character. As stated before, it is always necessary to make a generous allowance for the set- ting up time and incidental time needed by the work- 342 TOOLS AND PATTERNS men in obtaining tools from the tool room, and in making measnrements, laying ont the work, and so on. Let it be supposed that a number of jigs or fixtures of very similar character are to be made by a mannfaetnrer for an outside concern. Then the esti- mator would consider that these various planing or shaping operations which are to be done on the work, can be carried along at the same time; if this plan be f ollowed, a considerable saving in time will be effected. There are so many conditions which affect the building of tools of this type, that it is a very difficult matter to go into the details of the processes used in different factories. About all that can be said in this regard has already been mentioned. A specific example or two could be given, but they would not serve any valuable purpose, and might only confuse the reader. However, in the estimating of costs for work which is to be put through the factory in large quantities, other factors which are more nearly stable come into play. A ManofaetaTing Case. — Let us now consider the estimating of cost for a manufacturing proposition involving a number of pieces of a similar kind, which are to be made up entirely on an automatie screw machine. Under such circumstances it is a very simple matter to decide exactly which are the tools that must be used for the work, and since the material from which the work is to be made is of a certain character, and, furthermore, since the feeds and speeds of the machine can be easily de- termined, it is evident that a very close estimate of ESTIMATING COSTS 343 the actual tim^ needed to produce the work can be obtained without great difficulty. Let us assume further that the job includes a number of pieces which must be machined on an automatic screw machine, that a series of holes must be drilled in each piece, and that a single milling operation is called for. It will be seen that although this piece of work is some- what more difficult to figure than the other one men- tioned, it is nevertheless, a simple manufacturing proposition. In this latter case, however, it is neces- sary to take into consideration the fact that certain tools and fixtures must be made, if the work is to be done properly and is to come within the required limit. A jig and a milling fixture will both be neces- sary. The cost of these fixtures must be estimated, and the price must be, included in the cost which is submitted to the customer for whom the work is to be done. Overhead Expense. Hourly Basis,— The matter of overhead expense is so broad, and furthermore it is of such a variable character, that it is difficult to give anything more than a general idea of it in this chapter. Briefly, the overhead expense of a factory conskts of a burden, or load, over and above the ap- parent cost of labor. That is to say, if a workman spends one hour in turning out a piece of work and if his rate is 30 cents an hour, this burden must be added to the workman's actual cost of labor, in order that the cost of equipment, cost of power, and various other costs, may be taken care of properly. In addi- tion to these matters, the manufacturer's profit, and the dispreciation of his machinery and equipment, TOOLS AND PATTERNS iniist also be oonsideredi together with the percen- tage on the investment, in order that when the work is completed there may be a large enough profit to prove to the manufacturer that his business is a profitable one.* It is evident that factories of different kinds and under different management would have a proportion of overhead expense that would differ according to the factory conditions and many other items pertain- ing to ilie management. In the past few years I have noted a wide difference between the bids sub- mitted by different manufacturers on the same jigs and fixtures. This difference in prices makes it clear that either there is % tremendous difference in the ■ way in which different manufacturers estimate on the same piece of work, or else the equipment which these viyrious manufacturers use for producing the work is in some cases better adapted than in others to the class of work on which these prices were submitted. Different Methods but One Piinciple.--One particu- lar inslanee is worthy of mention. A set of blue- prints of a group of three indicating gauges was sent to five different manufacturers, with a request for bids. The lowest bid received was $670, the highest bid was $1472. The work was given to the man whose bid was tie lowest, and the work produced was of so high an order that it passed a most rigid inspec- tion. It is evident from this case that the manu- facturer whose bid was the highest would have been * A full discussion of the factors affecting the determination of burden or overhead will be found in Industrial CJost Finding, by N. T. Flcker. Factory Management Ck)urse. ESTIMATING COSTS 345 able to make a very high profit on the work, had he succeeded iu obtainiug the coutract, or that his operating methods were very inferior. As a matter of fact, I have found that many manufacturers who bid upon this class of work do not go to the trouble of figuring out all the details of manufacture carefully, but merely look over the work and form a rough estimate from their previous knowledge of how long it takes to do the work. To be sure, a man of wide experience can, even by this method, obtain a close approximation of the time necessary to produce a given piece of work, always provided that this man has had experience with other work of a similar kind. On the other hand, a careful estimator who has had the necesary shop experience and many years of actual shop training, can obtain a much closer ap- proximation of the cost of production by figuring out the actual amount of work which must be done to complete the piece. Evidently, then, different processes of estimating cost are used by different manufacturers. It is hard to say just what method is best suited to a particu- lar class of work, since so many factors enter into the matter. It is always safe, however, to act upon the principle that the careful estimator who figures the work on the hourly basis will obtain, in the long ran, a much more uniform and satisfactory estimate of cost than the man who depends upon snap judg- ment. Each manufacturer must be a law unto him- self in this regard, but the careful man, who adopts the principle of safety first," will find himself better off than the one who uses the **hit or miss" method. CHAPTEB XXin INTERNAL, EXTERNAL AND THREAD GAUGES Aeenraiqr Beqnired in Intrndiangeable Muiufac- tore. — When a number of parts are to be made that will be interchangeable one with another, it is neces- sary to make the parts within definite limits of accu- racy. Before going into this subject let us first under- stand the different terms which apply to gauging and gauging systems. Let us also determine the use of a gauge and its applications to the work. In the first place in assuming that a number of pieces of the same size are to be made, it will be necessary for the workman to measure each piece as he is pro- ^ ducing it in order to be sure that the sizes are kept to the dimensions, unless a system of gauges is made for the work. He would use for this pur- pose a set of micrometer calipers and other measuring instruments of precision depending upon the class of work on which he was engaged. But as these instru- ments are all capable of being set to certain sizes, and are, therefore, flexible, it is obvious that in using these tools he must be able to discriminate in their applica- tion. He must guard against error in reading the Jis micrometer, or other instruments. And, again, the continual use of such delicate instruments in manu- facturing is not to be commended on account of the m iNTBlNAIi, EXTERNAL AND THREAD GAUGES 347 wear involved. In order, then, to take the place of these delicate instruments, especial gauges can be made to give fixed readings; also in order to provide for slight variations in the work, *Mimit" gauges can be used. Let it be supposed that automobiles are to be made up in large quantities complete in every part and on an interchangeable basis, such that one part if injured or worn out can be replaced by another which will be the counterpart of the previously used portion. Assuming that a condition of this kind is found, the first step in the gauging system must be a determina- tion of the different kinds of fits which will be used in the different parts of the automobile. In this connec- tion the quality of the product must be taken into con- sideration. That is to say, if an excellent machine is to be manufactured, the workmanship will be natu- rally of a high grade and, therefore, the allowances for the various fits must be consistent with the quality of the machine to be manufactured. Let us consider this matter in detail under the various headings given here- with. Terminology. — ^When two parts are to be fitted to- gether the relation of these parts to each other is in the nature of a fit of some kind. For example when a shaft is to be fitted to a bearing in such a way that it will revolve freely in the bearing, the fit will be called a running fit". A *'push fit" is somewhat closer than a running fit; the parts are not free to revolve, but can be assembled by hand without using much pressure. A ''drive fit" is such that the parts can be assembled only by means of pressure under an arbor press or by dri^' 348 TOOLS AND PATTERNS ing with a hammer. A "force fit*' is such that the parts must be assembled by means of teat and hydrau- lic pressure. It is evident that there may be several kinds of run- ning fits; that is, there may be several grades of these fits. If we should assume that a farm machine, such as a harvester or mowing machine, was to be made, it would be apparent that such a machine subjected as it is to heavy usage and in the hands of men who are not mechanical, w^ould need to be rather freely put together. This class of fit would obviously be less accurate than if the machine in question were to be an automobile or a sewing machine or some other type of mechanism requiring careful workmanship. Therefore it is plain that several grades of running fits must be made to suit different kinds of work. These matters are entirely dependent upon manufacturing conditions and also the requirements of the mechanism after it is completed. Manufacturing conditions are such that it is easier to make shafts or studs to a size a little under or a lit- tle over a specified dimension than it is to make a hole over or under a given size. This is due to the fact that a hole is usually drilled, bored, reamed, or ground. It is not a very easy matter to make a reamer so that it will •cut a hole much different from the standard size (although a new reamer is inclined to cut a trifle over- size, and after it is worn a little it may cut a little under-«ize). Therefore the size of the holes are usually kept as nearly to a standard as the* uses of tools will permit. As a general thing it is not customary to put any kind of a limit on a hole which is to be drilled, but holes which are to be reamed or ground can be INTERNAL, EXTERNAL AND THREAD GAUGES 349 machined within close limits of accuracy. It is well to state parenthetically at this point that as the hole is usually made as nearly standard as possible the limits of accuracy within which it must be machined are de- termined by conditions. The shafts or studs, however, which fit the holes are made within limits determined by the class of fit for which they are intended. Terms Used in Oangiiif . — In mentioning the terms used to describe various points in connection with gauging, there are three words the meaning of which are not always clear to the average man. These termis are "allowance,'' "tolerance," and "limit." The term allowance is used to describe the relation that one piece bears to another when the two parts are assembled. For example, if a shaft were to be fitted into a hole so as to revolve freely, it would be neces- sary to make an allowance between the size of the hole and the size of the shaft so that the right relation will be maintained between the two surfaces and permit the shaft to revolve with the proper amount of clearance and sufficient freedom in the hole. If a hole were to be reamed to 1 inch in diameter and a shaft were to be revolved in this hole, we can assume that an allowance of 0.001 inch must be made on the shaft under the size of the hole so as to permit free turning. It will be seen that the kind of fit which must be obtained be- tween two pieces of work determines the possible al- lowance. The term tolerance applies to the total amount of variation permissible in manufacturing any given piece of work. As an example, let us take a shaft 1 inch ^ diameter which must be machined to a given size. 350 TOOLS AND PATTERNS Tolerance is determined by the machining possibilities and the quality of fit which is to be made. If it is sup- posed that the shaft is to be machined within a toler- ance of 0.0005 inch, then the maximnm and minimum variations must not differ by more than the amount mentioned. The term limit is applied to the maximum and muii- mum size of work to be produced as determined by the tolerance. For example, if the work is to be made FIO. 139. DIAGRAM SHOWINa APPLICATION OP LIMITS TO A 8HAPT AND HOLE within a tolerance of 0.0005, then the limits within which the piece may be permitted to vary must be such that their total amount will not exceed the prescribed tolerance. Let us take a concrete example of the shaft and hole diagramatically shown in Figure 139. This illustra- tion shows that the limits as set for the dimension of the hole are given in terms of plus (+) and minus (— ) It will be seen that the shaft sizes are also given in limits but that the limits are both minus dimensions. INTERNAL, MXWmKH^ THREAD GATOESmi From the figures given on the diagram, the greatest amount of variation possible is as follows: Maximum hole = 1.00025 Minimum shaft = 0.098 Clearance = 0.00225 Minimum hole = 0.99975 Maxuaum shaft = 0.999 Clearance = 0.00075 From the diagram and the foregoing figures it will be seen that in such extreme cases the allowance or clearance will be sufficient to obtain a running fit for the shaft in the hole. It is true that in the greater extreme the clearance is a little more tl|||^^ be, while in the smaller allowance the fit is a little closer than it should be; but if the gauges which are used for the work are properly used, there will be no doubt that the fits obtained are commercially good. The principles shown in this diagram can be applied to other kinds of gauging, and it is an easy matter to determine whether the proper allowance, tolerance, and lunit have been set for any given piece of work by means of a careful inspection of the results in mari- mum and minimum sizes obtained by following the limit given. Setting Limits for fiiterchaiigeable Work. — Gauging work in order to produce interchangeable parts is de- pendent upon so many factors that it is out of the question to give hard and fast rules here that will be applicable to all conditions. Manufacturers have established no system of limits which fit every con- I ■M +0.00200 -0.00100 0.00300 +0.00275 —0.00150 0.00425 1 isi +T e 1 •-• r-l C^J Q to SSq OiOUS e^^ fSI^ +T ooe testa 0 c5 e» 35 « CO dee +T 5 « 1 K (M sii ooe +T |8| oee +T to SS8 « o 888 +T 888 888 + T 5 < 1 ; 8SS "888 990 +T 1 §§'|^;' +T 8|S 888 ooe +T 8|| C3^ 4-T 8SS Oee c<» 5 000 ^^e SS9 "-H Q sis woo 0x3 •<> i§§, II « » • Nomiiial '. ten.Ix 852 1 -0.00850 —0.00425 0.00425 —0.00625 —0.00350 0.00275 —0 00350 —0.00175 0.00175 V4 j> 0 <£>0>0 lis 888 fr Q lO X3 §88 s 0 toiao lis tr ssg §88 ?r o>o>o t^coco 888 000 0x310 lis TT" to 8SS e<5 eo sss It SSS ir sss sss tr ill •eioo 888 ?r 888 e^o s ft*" sss ill •oioe SSS tr 000 000 Tr « s S 888 s 0x3 X3 X3 (M (M — — 888 CO sss is . sss ^^d J! 888 TT' |SS 8SS Tr MS too §0 ej>^d Z 888 §§§ III ^^e ill ^^0 Nominal Diame- ters, Inches. . . ail 1 ill 353 INTBINAIj, external, and thread gauges 355 ditionj and there is mor^ or less diversity of opinion. Tables used by the Newall Engineering Co. are given on the preceding pages which may be helpful to a manufacturer in establishing a system of limits for his own factory. As previously stated, the class of work to be done has a great effect on the setting of limits for mterchangeable manufacture, but a basis from which to work can readily be established and suitable changes made to suit requirements which later may be found necessary. The man who establishes a system of manufacturing limits for interchangeable manufacture must always understand the requirements of the work to be done and its nature. He must know just wfcere the finest work- ing parts of the mechanism are situated and how closely these parts must be fitted in order to give the results required. The conditions of manufacture must always be considered, and the vital parts of the mechanism must have special attention. As pre- viously mentioned, tolerances for all work should be as great as possible consistent with the quality of the work to be produced. In this connection it is well to mention the unfor- tunate practice of the majority of manufacturers in regard to shaft lengths. , It is seldom that they pre- scribe limits on this class of work, and therefore the workman in making a shaft is unable to determine how closely the shoulders must be made to the given sisses on the drawing. In order to obviate any trouble in this regard it is good practice to establish a system of some sort to govern such work. It must always be remembered that small tolerances mean careful work m TOOLS AND PATTERNS and tliat careful work is always expensive. Therefore it is highly advisable to specify the limits on shafts and shoulders in order to obviate difficulties in machin- ing. It is frequently possible to give shoulder toler- ances on shafts of 1/64 or 1/32 of an inch, and when it is possible to give such tolerances the cost of machining will be much more reasonable. Many manufacturers set tolerances entirely too dose in the effort to obtain a fine product. Some even go to the expense of finishing parts which do not fit others in order to improve the appearance of the finished product. Such practice as this is expensive and unneeessarjTy except in cases where parts must be balanced on account of the high rate of speed at which they are to run or else to prevent vibration due to excessive speed and lack of perfect balance. All these points must be considered in the setting df liinits, and therefore it is very obvious that the engineer who does this work must be perfectly fa- miliar with the product in its actual working points. Maridng Lunits on Drawings.— The marking of drawings with limits is commendable, and much eon- fusion can be avoided by using fractional dimensions for aU unimportant sizes. A notation can be made on the drawing to the effec); that an error of 1/64 + or — is permitted on fractional dimensions given on the drawing. Decimal dimensions can also be used to indicate tolerances to a certain degree, although this practice in general is not recommended. There may be a notation or an understanding in regard to the matter, however, such that if decimal dimensions are given to four places of decimals, the work must INTBBNAL, EXTERNAL AND THREAD GAUGES 357 be kept within a limit of plus or nunus 0.0005; if three places of decimals are given on a drawing then the limit is to be kept within 0.001 plus or minus; if two places of decimals are given on the drawing then it may be understood that a limit of 0.005 plus or minus is permissible. The better way, however, is to mark the drawings positively with the limit when- ever possible, so that there is no chance for errors on the part of the workman. Internal Limit Gauges.— If it is necessary to ma- chine a hole within certain limits of accuracy, a gauge should be provided which is so constructed as to permit the workman to use it in determining whether he has produced the work within the re- quired size or not. If the hole to be measured is a cylindrical one of small size, say 2 or 2% inches, then the type of gauge which is used is termed a plug gauge. And if the hole to be gauged is tapered, the type of gauge used is termed a taper plug gauge. If the hole is threaded, the gauge used is called a male thread gauge. These three gauges are of different types and are made differently to suit the various kinds of work for which they are to be used. A limit gauge is a gauge so constrncted as to de- termine more or less automatically whether work has been made within the specified limits or not. There are several types of gauges for this purpose, which differ from each other only in certain details of con- struction; the principles on which they are based are the same. The type used for gauging a cylindrical hole has one end made of such mm that it will just enter the hok providing the hole has been made large 358 TOOLS AND PATTERNS 60 N OT 60 00 NCT OO 00 NOT 60 no. 140. SEVERAL VARIETIES OF PLUG GAUGES enough; the other end is very slightly larger than the hole should be, the difference in size being the ex- treme limits or tolerance permitted in the work. Therefore a gauge of this kind is frequently spoken of as a ''go and not go" gauge, meaning that one end should go into the work and the other end should not go. Sometimes the go and not go portions are on the same end of the gauge. Beferring to Figure 140, the two types of gauges commonly used will be noted at A and B. The upper figure, A, shows the double-end plug gauge, and the lower figure, B, has both of the limiting portions on one end. The lower type, B, is to be pre ferred for work in which the hole extends cona- pletely through the piece, as the workman in this iNTBRNAIi, BXf BBNAL AND THEEAD GAUGES 359 case is not obliged to turn the gauge end for end in using it. These gauges are often made with a slight taper on the end, in order to facilitate their use. Another type of plug gauge for cylindrical work is shown at C in the same figure. This gauge does not differ from the one indicated at A in any respect ex- cept that the go and not go portions are made in the form of bushings which can be removed and replaced with others in the event of their becoming worn. Although gauges of this kind cost a little more to produce, they have many advantages, which are plainly apparent, in the line of upkeep. Intamal Taper Gauges.— The gauging of a tapered hole is an entirely different proposition from the gauging of a cylindrical one, for two gaugings are re- quired, namely, the taper itself and the diameter at the large end of the hole. It is obvious that a tapered hole is made to fit a tapered shaft or some- thing of similar nature. In a gear which is made with a taper hole, for instance, the gear must be made to mesh correctly with its mate, and therefore its longitudinal position on the tapered shaft is im- portant. This means that the tapered portion must be of such a diameter at the large end that it will slip upon the tapered shaft to a definite distance and fit snugly on the shaft at the same time that it attains its correct position longitudinally. It is plain, then, that a gauge for such a piece of tapered work must be so made that it will determine the taper as well as the distance that the actual fit will take place on the shaft. As it is rather difficult to measure a tapered hole 360 TOOLS AND PATTERNS at the large end, or in fact in any other portion of the hole, without special instruments. The method used in gauging the diameter is by the distance that a marked section of the gauge enters the large end of the work. By reference to Figure 141, the type of gauge used for a tapered hole will be clearly noted. This gauge is a limit taper gauge, and the WG. 141. TAPER UMIT GAUGE FOR INTERNAL. TAPERED HOLE limiting portions are determined by the flatted part, B, on one side of the gauge and the cylindrical por- tion, C, which extends beyond it. Now when this gauge is used in a tapered hole, the operator places it in position and notes whether the flatted portion is below the surface of the hole or not. If he finds that it is below the surface and that the opposite side of the gauge, C, remains slightly outside of the work, then he is certain that the work has been made within the required limit longitudinally. In addition to the longitudinal dimension, how- ever, it is necessary to determine whether the taper INTERNAL, EXTERNAL AND THREAD GAUGES 3(ii MO. 142. FEMAU: MASTER GAUGE FOE TESTING MALE TAPEE GAUGES is correct or not. As a general thing the taper in a hole is determined by means of a special tapered reamer and, therefore, there is little chance for varia- tion at this point. However, in order to determine the taper with certainty, the inspector may use a little Prussian blue on the gauge and by revolving it slightly in the hole, he may see whether it is in contact along its entire length or not. In connection with the use of taper gauges and, in fact, other types of gauges, mention should be made of the necessity for reference gauges. Gauges of this kind are made with great care and should be kept in a safe place so that they will not be subject to injury or marked variations in temperature. It is apparent that a reference gauge for a male taper gauge, such as that just described, would be such that when placed in conjunction with the reference gauge any variation might be readily detected. A 362 TOOLS Am PATTBI^S male gauge is usually tested by placing it in a female gauge, and conversely a female gauge is tested on a male gauge. When a number of tapers of different diameters but of the same angle are to be tested, a reference gauge like that shown in Figure 142 can be readily made. This gauge is marked with the piece numbers and the limits in such such a way that the accuracy of the gauge to be tested can be quickly determined. This gauge is made with three adjustable blades of steel to facilitate manufacture. After the gauge has been set properly by means of suitable measuring in- struments, the screw holes can be filled with wax or composition so that they cannot be tampered with. Male Thread Gauges. — ^When an internal thread is to be ganged the type of gauge used is generally called a male thread gauge. The gauging of a thread requires special precautions as there are so many points to be determined: First, theVe is the diameter of the thread at the pitch line; second, the angle of the thread; third, the diameter of the hole at the bottom of the thread; fourth, the lead of the thread.* The ordinary commercial gauge only gives an ap- proximation of these four points, otherwise several gauges would be needed to determine whether a thread was correctly made or not. The simplest form of thread gauge is a piece of ♦The lead of a thread is the distance from the center of one thread to the center of the next« measured longitudinally. That Is. In a 16 pitch thread, the lead is i inch, because there are 16 threads to the inch. On multiple threads, i. c, double or quadruple threads. lead denotes the longitudinal distance from one thread to the same thread after it has passed once around the piece. Thus the lead -of ft 16 pitdi thread qiiadnqile, would be 4x ^ = H incb. • UNTKRNAL, EXTERNAL AND THREAD GAUGES 3a steel threaded on both ends, one end of which is made so as to enter the threaded hole and the other end slightly larger so that it will not enter the threaded hole. This type of gauge is clearly shown in Figure 143. Commercially, a gauge of this type gives results sufl&ciently close to the limit. The majority of threaded holes are made by taps, and if the thread gauge does not enter the work freely, it is generally found that something is the FIG. 143. STANDARD TYPE OF MAO: THBEAD QAVm matter with the tap that has been used. The taps should then be examined to find where the error lieis and be discarded if found faulty. In most cases it will be found that a variation in the lead is the cause of the trouble. The tap may have been made up properly and have changed considerably during the hardening process, so as to give a lead slightly dif- ferent from what it should be. It is an easy matter for a workman to tap a hole to the proper size, but 'f the lead of his tap is incorrect, great difficulty may be found in assembling the parts after they have been machined. A variation in the lead of the thread 11 364 TOOLS AND PATTERNS INTEBNAL, EXTERNAL AND THREAD GAUGES 365 means that only a few threads will be doing all the work while the other ones are free. Several inBtraments are made for measuring the lead of a serew, based on the pitch line m^ure- ment. Usually these instruments are provided with ball points to reach down into the thread and measure directly on the pitch line. The type of thread gauge shown in the illustration is practically the only one which is commercially used today. The amount of tolerance permitted should never be more than 70 to 80 per cent of a full thread. Some gauges are made in such a way that a por- tion of the gauge will act as a plug to measure the root of th-e thread or, really, the diameter of the hole. In this case the thread itself is measured sepa- rately. The majority of commercial screws are made with two much clearance; this results in a loss of strength and is productive of considerable difficulty when used on machinery otherwise all right. The result of poor workmanship on threaded work is that the threads, not having a full bearing, strip easily and are generally useless. The limit on threaded work should be sufficient to avoid such conditions. Ixtanal Oaiigea.— External gauges are made for cylindrical, taper, or threaded work. There are sev- eral kinds: snap gauges, ring gauges, receiver gauges, and female thread gauges. The snap gauge is the most common and is used for gauging cylindrical work. The ring gauge is generally used for reference, although occasionally it is used for actual gauging processes. Receiver gauges are made for determining several diameters at the same time and* also for taper MG. 144. STANDARD TYPE OF SNAP GAUGE YTTTH ADJUSTABLE POINTS work. The female thread gauge is used for gauging male threaded work, such as screws and the like. In gauging cylindrical work which is to be held within definite limits of accuracy, the snap gauge shown in Figure 144 is commonly used. This gauge is provided with surfaces or pins which limit the amount of variation, as shown at A and B in the illustration. The '^go" portion of the gauge is rep- resented at A; the "not go" at B, This gauge is used directly on the work and is extremely simple. As an example, let us suppose that a piece of cylin- drical work is to be held within the dimension 0.998 and 0.996. Then A would be made 0.998 and B, 0.996; hence if the work were to be made so that it will enter A and not go between the points B, it is m TOOLS AND PATTERNS flG. 145. SNAP GAUGE FOR FIG. 146. TEMPLET GAUGE FOR A IIOBE THAN ONE DIMENSION SPECIAL STUD sure to be right. When this gauge becomes worn, the points A and B can be adjusted by size blocks or regronnd to size. In order to avoid either acci- dental or intentional changes, it is well to pour melted wax into the holes at the adjustable points, or else to put a drop or two of solder at these points so that no change can possibly be made without per- mission from the inspection department. Snap Ganges for Widths.— Gauges of the snap variety are also used for determining* widths across lugs and between them, for shoulder distances on shafts, for distances between bearings, and for other work of like character. Sheet metal gauges are fre- quenUy made for this purpose, and several gauging points can bemiill I HIWl ingle gauge. For examp^ having a casting, such as shown above in Figure 1^^ in which the dimensions A and B are to be gauged, a snap gauge similar to that shown in the lower por INTERNAL, EXTERNAL AND THREAD GAUGES 367 tion of the figure can be employed. This type of gauge is made up of sheet steel, usually Vs to 3/16 inch in thickness, and hardened after it has been made very close to size. After the hardening, the gauging points or surfaces are carefully ground to correct dimensions. Gauges of this kind can be used in confined situations, and as they can be cheaply made their use is almost infinite. Templet Gauges. — Frequently it is necessary to determine the form of a piece of work after it has been machined, especially when the shape of the piece is more or less irregular. Take as an example the work sho\\Ti in Figure 146, in which the general form and correct spacing of A, B, and C are essential. In a case of this kind a templet gauge, similar to that shown at D, can be made to the form desired and the workman can use it when making up the piece, applying it to the work from time to time to obtain correct spacing and foriii. The templet gauge as ordinarily used is not, how- ever, an accurate method of gauging for it does not **tell the story," but only determines whether the shape of the work is correct or not. It does not show just where the points of inaccuracy are, but it does show that the piece is not correct if it does not fit the gauge. When it is necessary to gauge the con- tour of a piece of work within close limits of accu- racy, another type of measuring instrument, termed an indicating gauge, can be used. This type will be described in the next chapter. Perhaps one of the most useful appBcations of the templet gauge is in the manufacture of bolts, cap 368 TOOLS AND PATTERNS FIG. 147. TEMPUBT GAUGE FOB A SCREW screws, studs, and the like, for determining the length of the work and the length of the thread. As an example, let us take the screw shown in Figure 147 in which the length, A, is 3 inches and the length, B, of the thread, 2 inches. A gauge can be made for this work similar to that shown in the lower part of this illustration. Its application is obvious: both the length of the work and the thread can be noted in an instant when the gauge is applied. There are many other uses to which the templet gauge can b®* adapted, and the forms used are naturally dependent upon the work to which they are to be applied. Ring Gauges for Cylindrical Work.— Bing gauges, such as that shown in Figure 148 at K, are used m a large degree for reference, but they are also occa- sionally called for in connection with manufacturing INTERNAL, EXTERNAL AND THREAD GAUGES 369 on certain classes af work. The ordinary snap gauge as used on cylindrical work simply gives the diameter of the work at certain places where it is applied, but it does not show the variations along the shaft, nor does it determine whether the work is uniform in size at all points. Let us take the piece of work shown in Figure 148 as an example: Here we see a shaft on which another member is to have a sliding fit from A to B. In gauging this shaft, the snap gauge would be used at two or three points, as at C, D, and E, and it will be assumed that the remainder of the shaft is correct, providing these points pass the inspection. By re- ferring to the exaggerated view, much enlarged, of the same shaft, it can be seen that if the work is found to be imperfect, as shown at F, G, and H, the ■ u ^ ^ 1 * A A t — 1 F. d c r Q D' FIG. 148. CTMNDMCAL RING GAUGE, SHOWING APPUCATION S70 TOOLS AND PATTERNS snap gauge will not reveal the defect Bat if the ring gauge, K, were to be passed over the work from A to B, the trouble would be located immediately. For work of this kind, therefore^ the snap gauge can be used as a work gauge and the ring gauge for the final in- spection. The workman can then gauge the work for diameter, and the inspector's test with the ring gauge will show any variations along the length. Reoeivitor Ganges. — On certain classes of work, such as the components of rifles, sewing machines, type- writers, and adding machines, it may be found neces- sary to gauge every part of the piece as a final check against errors in machining. In this work a receiver gauge can be employed to advantage. This instrument is so made that the work can be placed in the gauge itself, and if 'the piece of work has been correctly made within the required limits of accuracy, it will conf oni m. 140. EExmvm oaugs fob tafeb hns INTIBNAL, EXTEENAIi A^fg/gmM) aAUGES 371 closely to the contour of the receiver. Gauges of this kind can be made as limit gauges if desired, either by making them up with a series of sliding points to in- dicate the limits of variations permissible, or by making two gauges in one of which the work must go and in the other not go. Sometimes it is neces- sary to gauge a contour very carefully, and in cases of this kind an indicating gauge can be employed,, as described in the next chapter. MG. 150. RECEIVER GAUGE FOR A POPPET VALVE A common form of receiver gauge is that shown in Figure 149, which is made for taper pins. Keference to the illustration will show that it consists of a base plate and two blades, one of which may or may not be adjustable. In using this type of gauge the pin is simply laid between the two blades in order to note whether the taper corresponds to that of the gauge or not. An additional refinement can be incorporated in this gauge by placing a mark on one of the blades to gauge the diameter of the taper pin by determin. ing its length. 372 TOOLS AND PATTBKNS Another application of the receiver gange is shown in Figure 150. This gauge is made for a poppet valve, in order to test the concentricity of the stem, Ay and the valve seat, B. In addition to these points the angle of the seat can also he ganged. It will be noted that a part of the collar, C, is cut away to permit inspection along the seat of the valve. Many applications of this type of gange can he made when the nature of the work warrants it. Taper Ring Gauges. — In gauging a taper shaft or work of similar character several varieties of gauges may be used. These gauges are usually made from a cylindrical piece of steel having a tapered hole, such as that shown in Figure 151 at A. The limits are taken care of by cutting away half of the gauge at the large end, as noted at B. The correct size is de- termined by the junction of the tapered portion with the cylindrical part and the position of the gauge no. 151. FEMALE TAPER UIOT GAUGE INTKBSAL, EXTBENAIi AND THREAD GAUGES 373 longitudinally on the work. The gauge should not push onto the work far enough so that the flat part comes beyond the junction of the tapered and the cylindrical part. The taper itself is found to be cor- rect or not by placing the gauge in position on the work which has been coated with a thin film of Prus- sian blue and giving it a slight turn to determine whether the taper is touching at all points. FIG. 152. MALE MASTER GAUGE FOR TESTING FEMALE TAPER GAUGES Master Taper Gauge for Female Gauges. — ^As a reference , gauge to which a female gauge may be applied in order to determine whether it is correct or not, a form such as that shown in Figure 152 can be advantageously used when all of the tapers to be gauged have the same angle. This gauge was de- signed to go with the female gauge shown in Figure 142. But in this case the gauge is intended for test- ing female taper gauges while the other is intended for testing male taper gauges. It will be seen that 374 TOOLS AND PATTEBNS HG. 153. FEMAo: thread oauge there are three blades, A, which are set into a column of steel supported by a base, B. Along the blades, the limits for various sizes of tapers are marked, as indicated at C, D, E, P, etc. In use, then, a master gauge of this kind is set up on its base, the ring gauge is dropped over it, and an inspection will de- termine whether the ring gauge is made correctly both as to limit and proper taper. Gauges of this kind which are intended for reference only should be preserved very carefully and never used for anything except reference. ^ Female Thread Gauges.— When a piece of threaded work, such as a shaft or stud, is to be gauged on its threaded portion, the testing is usually done by screw- ing the work into a female thread gauge, such as that shown in Figure 153. This gauge is made from a piece of steel of rectangular form and is drawn toffeih^r or separated, as the case may require, hj means of the set screws indicated at A and B. INTBBNAL, BXTEBNAL AND THREAD GAUGES 375 Adiustment is simply for the purpose of fimshmg the 14e to the correct size with as little difficulty m possible. It also provides a slight adjustment after the gauge has become worn. Gauges of this kind are seldom made with limits; but for very particular work two gauges can be used, one of the -go'' variety and the other of the not ffo " For ordinary commercial work which does noi require very close limits of accuracy a gauge of this kmd will be found sufficient. For determining whether the lead of the thread is correct, a separate instrument must be used, as de- scribed in the next chapter. In general, threads ot this kind are not gauged for the lead unless they are particularly important, in which case the in- dicating type of gauge is used to determme the cor- ''^Therf are other types of external and internal gauges which are used for special purposes, but the maiority of them are modifications of those whicn have been shown or else they are of the indicating type of gauge for determining variations m mside or outside contours. The description of such of these gauges as are not mentioned in this chapter will be taken up in the following chapter. ' CHAPTER XXIV PBOFILE AND INDICATING GAUGES Gauges for High Accuracy. — ^The present tendency in gauging methods is to do away as far as possible with all gauges which do not show the amount of variation in the work. Many of the gnHH described in the previous chapter are made to indicate whether a piece of work has been finished within the required limits or not. The workman, in using ordinary limit gauges, has no means of knowing (except the sense of feeling) how nearly he is approaching the limits which are permissible. His first real knowledge that his tools have **gone the limit" is when his gauge tells him so. Hence it will be seen that for work requiring a high degree of accuracy, the ordinary types of limit gauges do not quite answer the pur- pose. For such conditions, then, some other type of instrument by means of which the actual variations in the work can be accurately determined, is essen- tial. Now let us see what principles can be used in gauging work, keeping it within the prescribed limits and at the same time indicating the variations which are taking place from time to time because of the wear and changes in size of cutting tools. It is evi- dent that indicating instrum^ts which will show FlOFILl AND INDICATING GAUGES 377 variations in the work make it possible for the work- man to change his tools as may become necessary and thus keep the work much closer to size than if the ordinary limit illpes were used. For instruments ofliis kind variations in the work can be shown by a pointer of some sort working over a graduated scale; by the sense of touch in the work- man's fingers as they are passed over one or more movable points; or by the sense of hearing, as in the case of a gauge showing limits by an electric contact which rings a bell or operates a buzzer. Of these three types, the dial-indicating, or multiplying-leyer type, is most common. This gauge has a sensitive movable pointer which works on a graduated scale or dial, and can be adapted to an infinite number of uses in gauging. The **feeler" or **flu&h pin" gauge is also used to a considerable extent on work of irregular form, or for depth gauging; it is sometimes found convenient to use it also in the case of deter- mining a correct shoulder distance. Micrometer gauges are also used to some extent on work requir- ing the highest degree of accuracy. And finally, there is a type of gauge which employs a delicate and sensitive arm so arranged that it multiplies the actual variation in a piece of work; if the variation is too great, it rings a bell by an electrical contact, or shows a red or green light if this scheme is pre- ferred. Standacrd Instimments of Predston.— Any mention of gauging systems which does not include some of the standard measuring instruments would be in- complete, but as we e for the most part concerned 378 TOOLS AND PATTEBNS SECTIONAL VIE>N OF MiCROMfJER CAUPCR MICROMETER HEM> HQ. 154. MICROMETER GAUGES SHOWINQ CONSTEOCTION FEATURES with special gauges, we will not devote a great amount of space to instruments which are adapted to the most minute variations, such as micrometer and vernier calipers and other instruments of precision. But as the principles on which these instruments are hased are also applied to gauging certain kinds of work, let us look into the fundamental pomts on which they depend for their accuracy. . The micrometer caliper, shown in Figure 154, is familiar to all, and a brief description is all that will be necessary. The upper portion shows at A a gen- eral view of the instrument; a sectional drawing jusi below, gives an excellent idea of the constructio^ The frame, B, m a drop forging which is supplied! PBOFILE AND INDICATINa GAUGES 379 with a hardened inserted anvil, C. The frame is bored out and has an adjusting nut, K, iiisid|||||d a short nut, L, to compensate for the wear on thte threads. The screw, D, is threaded at E, and is fast- ened to the thimble, G, so that it can be rotated by the fingers of the operator. Bach revolution of the screw moves it longitudinally 0.025 inches. The upper view shows the graduation on the thimble; and as there are 25 of these, starting with 0 and running to 25, each division represents 0.001 inch. It will be seen that by placing the work between the points C and D and adjusting the screw by means of the thimble, an accurate reading can be easily obtained. This type of instrument is used all over the world for accurate measuring. The' micrometer head shown in the lower portion of the same figure is sold as a separate instrument and can be applied to many forms of gauging by mounting it on a suitable fixture to conform to the work which is being gauged. Dial Indicator. — ^Another form of gauge, useful for inspecting a number of parts of the same kind, is shown in Figure 155. This instrument may be adapted to a variety of work by mounting it on a suitable holder to fit the conditions. It should not be considered as a gauge, however, but more as an indicator to show variations in size after setting it to a size block or plug. This instrument consists of the base, A, on which is erected a vertical shaft, B, absolutely perpendicular to the base. A sliding lever acts on this shaft m a holder for the dial indicator, C. The sleeve can be vertically adjusted and clamped at any desired height by means of a thumb screw TOOLS AND PATTERNS TO. 155. Aim MAh TOT rnVGE ABRANOED FOB INSPECTION (mi shown) at the rear of the instrument. The gauge point, D, is connected with the dial by means of a multiplying device inside of the instrument case, and the dial is graduated to read in thousandths of an inch, or finer if desired. In operation, a plug of the desired size, similar to that shown at S, is used for setting the gauge and indicator so that the pointer will read 0 if the work is correct. A piece of work, such as shown at E, is then passed under the gauge point, D, and the reading is noted. Variations can he quickly determined in this way, and a number of pieces tested one after the other. Indicators of this type are also frequently mounted on special gauging fixtures for special work. Prestwich Fluid Gauge— There has been a demani for many years for an accurate indicating gauge reading to one ten-thousandth part of an inch or finer, and a number of instruments are now on the market which will give readings as close as this, bit TO. 156. FllSfWI09 WLVm OAUCH 382 TOOLS AMD FAfTSENS they are quite delicate m construction and require careful handling as well as care in reading. The recently developed gauge shown in Figure 156, however, answers the demandB of modern engineering work most admirably, md the reading of the instn- ment is so plain that a variation of one ten-thou- sandths part of an inch is discernible across an ordi- nary room. Furthermore the work can be gauged to specified limits, with the gauge set to meet the re- quirements of the work. For ball bearings, thread gauges, or any other work which needs to be calibrated in large quantities and within very close limits of accuracy, an instrument of this kind is indispensable. The principles involved in the construction are as follows: A fluid-containing chamber, A, is provided with a flexible diaphragm, B, and a glass tube, C, finely bored and connected with the chamber, A. The diaphragm, B, is furnished with a hardened steel pin or anvil, D, and the base of the instrument also has a fixed anvil, E, between which and the anvil, D, the work is passed when calibrating. The chamber, A, contains a colored liquid which rises and falls in the glass tube, C, according to the pressure applied to the anvil, D, and transmitted to the diaphragm. The lil||i|||!ira of the diaphragm in comparison with the fine hole for the liquid in the tube makes possible such a fluctuation in the tube that it is easier to determine variations of a ten-thousandth of an inch with this instrument than it is to discern a thousandth with most other measuring instruments. The chamber, A, is provided with a thread and micrometer index and a pointer on PROFILE AND INDICATING GAUGES 383 the upper surface, as indicated, to show thousandths of an inch. This portion of the instrument is made for the purpose of obtaining rough adjustments; but it is not used after the instrument has once been set to the size desired. The carrier, F, is furnished with a scale, G, and three adjustable pointers, H, J, and K. The upper two of these pointers are so arranged that they can be set to indicate the tolerance limit between which it is desired to keep the work when gauging. The lower pointer, K, is set to the normal level of the fluid in the glass tube, C, so as to compensate for any fluctuations from changes in temperature. The in- strument is roughly set to the size desired by means flO. 156-A. FBESTWIGII GAUGE USED IN GAUGING A PISTON TOOLS AND PATTERNS of the rack, M, and the pinion, N, on the pillar, 0, to suit the piece which is to be ganged. The clamping screw is then tightened, and the final adjustment is made by the micrometer dial, A, to a standard gauge or a piece of the given dimension. In the illustration, a piston wrist pin, X, is being gauged, a small special angle plate being set on top of the anvil, E, for this purpose, as clearly indicated. It is evident that a reading can be taken on a pin of this kind by simply pushing it along and noting any fluctuation in the column of liquid, C. Referring to Figure 156- A, the same type of gauge m. 156-B. raESTWicH gauge used fob inspection of TOBEAD GAUGES PBOFIIil AND INDICATING GAUGES 385 is shown applied to the measurement of an auto- mobile piston. In this case it will be noted that the base of the gauge is furnished with a special block, S, and that a different indicating point, R, is used. In testing a thread gauge, such as that shown in Figure 156-B, another application of this most useful gauge is found. In this case the indication point is of special form, permitting the *Hhree-wire system" from the fixed diameter to be used. It will be seen that with this improvement, thread gauges or work of similar character can be determined with the utmost nicety and tl^at the most approved system of gauging from the pitch diameter can be adopted. This gauge can be applied to many other varieties of special work, and its sensitiveness and facilities for quick and accurate reading make it invaluable to the progressive manufacturer. Flush-Pin Gauges.— The flush-pin gauge is with- out doubt the simplest type of gauge based on the indicating principle. Several applications can be made of this principle, one of the most useful of these being the measuring of depths or shoulders. Flush-pin gauges usually consist of a base or holder of some sort in which one or more pins are inserted so as to form a diding fit in their bearings. The pins are made of correct length for gauging a given sur- face, the limit being determined by noting the amount of projection of ttie end of the pin beyond the end of the gauge itself. As an example, let us take the flush-pin depth- gauge shown in Figure 157. In this case, the work, A, is placed on a surface plate and the gauge is used TOOLS AND PATTKRNS f Surfacm .Pfofe^ • * no. 157. FLUSH-PIN DEPTH GAUGE to determine the correct distance, B. The gauge itself consists of a holder, C, through which the gauge pin, D, works, a small retaining pin being used to prevent the pin from falling out when not in use. The end of the gauge pin is cut away to the center line to show the amount of tolerance allowed in manufacturing the work. In using the gauge the in- spector simply notes that the shoulder on the pin is lower than the finished surface on the holder and that the end of the pin does not go below the shoulder. This indicates that the work has been machined within the desired tolerance. Gauges of this kind axe not suitable for work PBOFILl AND INDICATINa GAUGES 387 within very close limits. From 0.003 to 0.005 inijh is as close as this type of gauge can be used to advan- tage. When work permits a variation of 1/64 to 1/32 inch, gauges of this kind are frequently used, but for the closer work they are by no means to be recom- mended. They can be adapted, however, to fine read- ings by using an indicator to act on the end of the pin. This indicator can either be of the dial type, applied by mounting it on a suitable holder, or it can be a simple pointer pivoted in such a way as to provide a large ratio of movement at the end of the pointer. Referring to Figure 158, let us suppose that the push pin, A, in the upper sketch, is in contact with the work at the end, B, and that variations to 0.001 inch are to be noted. If the short end of the pointer has a fulcrum % inch from the bearing, C, on 17 7 37177 Oraduafhns 0.040'''^'- apart /feadinq Q/OOr ^ apart, ffeaamq wvt ,'Work vhnr A 'f\t$h Bh . .'Work wo. 158. FWJSH-Pm GAUGE lOT PRECISE WCMBK 388 TOOLS AND PATTERNS the end of the pin, and the pointer is five inches long, then the ratio of multiplication will be as % is to 5 or as 1 is to 40. Therefore, if the graduations on the arm or scale are cut 0.040 inch apart, a variation of the pointer on one of these divisions will indicate 0.001-inch variation on the push pin. Application of this principle can be made to many forms of gauges requiring a reading closer than that given by the ordinary flush-pin type. Still closer in- dications can be obtained by multiplying the levers, as shown in the lower portion of the diagram. One lever, working on another, F, will obtain a larger ratio. Flush-Pin Gauge for Tapered Shafts.— When a tapered shaft is close to a shoulder, as in the case shown in Figure 159, it is difficult to gauge the taper as to its position. In such cases, the flush pin, B, can be arranged so as to push the gauge on to the shaft until the pin strikes the shoulder, A, on the work, indicating the limit when the pin protrudes no. 159. FI^DSH-PIN OAUOE WGR TAFERED SHAFTS PROFILE AND INDICATING GAUGIS 389 through the gauge at C. Thi-s pin is shouldered to indicate the permissible limit of error similar to that shown in Figure 157. Gauges of this kind can also be used for determining shoulder distances on straight or taper shafts. Flush-Pin Gauge for Contours. — ^In some instances it is desirable to gauge one or two points with con- siderable accuracy and other points not nearly as closely. Take, as an example, the work shown in Figure 160. In this, case, the length of the work WG. 160. FLUSH-PIN GAUGE FOB CONTOURS between the points F and G, is not of the greatest importance, but the irregular portions at B and C must not be above a certain dimension and can be permitted to be under the dimension by 0.005 to 0.010 inch. The gauge in this case consists of a block, L, on which the pins, G, P, D, and E, are carefully set and against which the piece locates. Two flush pins, at H and K, are cut away on the end to show the amount of the tolerance permitted. It will be seen, then, that as the work is placed in the gauging 390 TOOLS AND PATTEBNS Ground. WMtC ^ I no. 161. DOUBLE FLUSH-PIN GAUGE fixture these two pins, H and K„ can be moved up against the points B and C, and the inspector can easily determine whether the projection of the end of the flush pin is too great or not. In this way the desired eontaar of the work can be kept within the required limit. Applications of this principle may be made to many other kinds of work where it is neces- sary to keep a certain portion within a specified tol- erance. Flush-Pin Depth-Ctonge for Indicating Two Sur- faces Simidtaneously. — ^Another type of flush-pin gauge for use on two surfaces at the same time is shown in Figure 161. This gauge is made up some- ; what differently from the others, as the pins are made of flat stock and the holder is composed of two ttr- side pieces, with fillers between them, the two side pieces, D, and the fillers, E, being riveted together as indicated. The pins, A and B, indicate different depths on the fly-wheel casting, C, and the limits are shown by the shoulders on the pins, as indicated at FandG. PIOFIUJ AND INDICATING GAUGES 391 Where the work is large, as indicated in the illus- tration, a gauge of this kind may be preferred to one made of a solid piece of bar stock with holes drilled and reamed for the pins. It is somewhat lighter m construction and, although no cheaper to manufac- ture, it is a trifle more convenient to handle. Its operation is similar to the flush-pin gauges previously described. In making a gauge of this kind, the various parts are hardened and are lapped to a finish. Suitable retaining pins are inserted so that the gauge pins wiU not be lost when the instrument is not in use. Indicator Ga;age for Testing Alignment of Con- necting-Rod Bearings.— The parallelism and align- ment of the connecting-rod bearings of an automobile motor is exeeedingly important. It is not enough to know that the alignment of the bearings may be in- correct, but the amount and direction of variation must also be known. In order to determine these two points it is necessary to use a gauge based on the indicating principle. An excellent type of gauge for this purpose is shown in Figure 162. The connecting rod, A, has been pre- viously finished in all of its dimensions, and is sup- posed to be correct and ready for the final inspec- tion. Previous to placing the work in the gauge, it is fitted with the special pins, B and C, hardened and ground to size, and fitting closely in the bear- ings at each end of the connecting rod. After the work has been supplied with these two pieces it is placed in the fixture, T, in such manner that the large end of the connecting rod lies between the finished 392 TOOLS AND PATTERNS PlOPILl AND INDICATING dAUGBB 393 surfaces, 0, on the fixtures and the pins at B and C rest on the hardened pins, D and F, at the large and small ends of the fixture respectively. When the work is placed in position tim spring pins, N, hold it liftpmly against the hardened pins, E, the pins, N, heing carefully adjusted so as to be perpendicular to the center line of the work. At the smaller end of the piece 4here is a fixed pin. F, and, on the opposite side, a pin, G, with an adjust- able knurled head and supported by the coil spring, H, in the body of the fixture. One side of the spring pin is slotted at K to receive the end of the indicator, L. This indicator works on a scale, M, reading to .001 inch. It can be seen, therefore, that any vari- ation in alignment of the connecting-rod bearings will be indicated by this pointer if the holes are not parallel in the direction indicated. Assuming that a discrepancy has been found in lie alignment, a suitable clamp can be placed on the piece while it is still in the fixture and it can be twisted until the alignment is correct. Having straightened out the alignment in this direction, it is then necessary to gauge the work in another posi- tion. For this purpose thMiMi P, bearing a dial in- dicator, S, is mounted in bearings, Q and B, these bearings being put on a line with the center line of the work. An indication of the parallelism of the shaft, C, with that of the other end, B, can easily be determined by swingmg the mdicatmg gauge, S,4tMMni one side to the other of the shaft, C, and noting whether there is any variation in the reading of the dial when this is done. The indicator should read I I 396 TOOLS AND PATTERNS the same on each side of the shaft if it is perfectly parallel with the other end. Applications of this type of gauge may be made to many kinds of work. It is possible to use either the dial indicator, as shown in this instance, or multiply- ing levers to indicate the amount of variation in the work. This particular gauge was designed by me on some work for the Russian government Special Indicating Oauge for an Automobile Cam Shaft— An automobile part requiring great care m gauging is the cam shaft. A special indicating gauge designed for such use is shown in elevation in Figure 163 and in plan in Figure 163-A. In this work the shape of the cam and the amount of throw are the imiK>rtant points to be inspected. Usually the amount of throw of the cam is not permitted to vary more than 0.003 inch; some manufacturers hold their work within tolerances even closer than this. In the cam shaft, shown at A, the cams indicated at D, D, D, have been forged integral with the shaft and ground to the desired shape. An essential point connected with the form and throw of the cams is their location with respect to each other and also in relation to the key way on the tapered end of the shaft at B. It follows, therefore, that the work should be located from this keyway in gauging the cam. The fiiinre itself consists of a base plate, K, which has been carefully scraped to a fine finish on* the surface. On this base plate three bearings, E, are set, which fit the outside diameter of the cam shaft. In gauging the work the shaft is laid in these three bearings and swinging clamps are pulled down on top of the shaft PROFILE AND INDICATING GAUGES 397 by means of the handles shown at F. As these handles are pulled down, the detent pins, H, snap into place in a conical hole in the side of the lever, and the spring plungers in the center of the swinging clamps, as shown at G, bear down on the cam shaft and hold it firmly in place in the bearings, E. Although these spring pins hold the cam shaft firmly in place they do not prevent its rotation. After the piece has been set into place, the finger lever, K, is pulled down until the work can be revolved suffi- ciently to permit the locater to enter the keyway at B. The work is now set ready for gauging. Let us assume that the work has been placed in position and that everything is ready to indicate the piece. ^ It will be noted that the block, L, is fastened to the. bed plate of the fixture and that the finger lever, E, is contained in a sliding cylindrical piece held in position by an internal spring. At the end of the shaft, M (which works in a hardened bushing on the inside of the block, L), a dial plate, 0, is keyed in the correct relation to the finger lever and keyway at B and B. This dial plate contains four tapered bushings in proper relation to the keyway, B, and the work can be indexed by pulling out the taper pin, P, and turning tie knurled hand-wheel, Q, for indicating the various cams. To indicate the throw of the cam, a special gauge — set on the stand, S, and having three feet of hardened steel, as shown at T, and an upper arm with indicating points at U and V for the **go" and "not go** limit of the throw of the cam^ — can be slid along the surface of the plate until the ^'go" and ^^not go'' points on the gauge come in con- TOOLS AND PATTBRNS PEOFIIjB and INDICATINa GAUGES 399 tact with the cam, thus determining whether the throw is within the desired limits or not. After these points have been determined, the indicating dial l« revolved and the next cam in rotation is similarly tested. The oontonr or shape of the cam is ganged by means of the block, W, which has a steel plate at X, formed to the contour of the cam. It is obvious that this gauge is also moved along on the surface of the plate until it comes in contact with the cam so that a comparison €an be easily made by the inspector. After the shaft has been completely tested, the entire mechanism of the indexing head is pulled away from the tapered end of the shaft until the lever, M, drops down into the recess on the shaft prepared for it. This holds the mechanism far enough back so that the cam shaft can be removed without difficulty. A gauge of this kind is somewhat expensive, but the results obtained by its use are most excellent. Feeler Gauge for an Automobile Crajik Shaft.— A limit gauge, rather peculiar in its character as it is nopwally an maicatmg gauge and yet ennMHI^ pended upon to hold the work within the prescribed limits of accuracy, is the crank shaft gauge shown in Figure 164. This instrument is used to determine the widths of the various bearings on the crank shaft and their relations to each other. One of the features of this gauge is that it can be used on the work while in process — ^it is not Becei|||||^^ until after the crank shaft has been rem^WKt the machine before testing it for accuracy. The gauge itself consists of a single hardened and 400 TOOLS AND PATTEBNS ground shaft, D, having at one end a templet plate, E, which fits the center bearing of the crank shaft and is prevented from moving sideways by means of the plate, C, which is ent ont to fit the bearing, as clearly shown in the end view. The other end of the gauge is also provided with a plate, cut out in like manner so that the operator may steady the gauge on the work and that it may have a correct location in re- lation to the axis of the work. In order to prevent the gauge from falling over sideways while the various bearings are being tested, a piece of sheet steel, M, is fastened to the shaft as indicated. Let it be assumed that the inspector is ready to test the crank shaft and that the gauge has been placed in position. It will be seen that the bushings lying between the spacing collars H and K, have each two plates or fingers, F and and 6 and G\ located one on each side of the bushings. Also the bushing at the end of the crank shaft and between the col- lars K and M has also a pair of feelers, L and L*. In testing the work, the feelers at these various points are swung by the operator's fingers between the bear- ings. If the first feeler goes through without diffi- culty and the second does not, the inspector is ready to pass the work. After one end of the crank shaft has been tested the gauge is reversed and the other end is tested in a like miKnner, using the center bear- ing as the gauging point in each instance. After the crank shaft has been gauged in this way, it is abso- lutely certain that all the crank pins and bearings are in correct relation to each other within the prescribed limits* PKOFILl AND INDICATING aAUGES 401 Although this type of gauge is somewhat out of the ordinary, it has proved successful in this kind of work. It is obvious that the greatest care must be used in making the instrument so that the various parts may have no more freedom than is absolutely necessary. Electrical Contact Gauge for Cams.— The use of electrical contact for determining variations within certain limits is well shown in Figure 165. Here, the WIQ, 165. ELECTRICAL CONTACT GAUGE work, A, which is to be tested, is a cam, the throw of which must be held within certain limits as in pre- vious instances. In this case, however, the cams are not on a shaft, but are separate and can be handled on a much smaller and simpler type of fixture. The work. A, is placed on a stud (not shown), the stud being located in the fixture plate. The gauge is so arranged that if the throw of the cam is cor- rect, a red light will show at J; while if the throw 402 TOOLS AND PATTERNS of the earn is too great, the Ml, K, will riiig. A reference to the illnstration will show that a hattery is connected with the screw, F, and through it to the tempered spring, E. A multiplying lever, C, is pivoted at B, and acts on the push pin, D, which in turn pushes up the flat spring, E, until it is in <}oii- tact with the adjustable screw, G. This completes an electrical circuit through the wiring indicated by the clotted line, and lights the red light at J. If the throw of the cam is too great, the push pin, D, forces the spring, E, up further until it touches the other screw, H, which also completes an electrical circuit and rings the bell at K. It must be understood that this is only a diagramatic illustration of the prin- ciples applied, and that various applications suitable to the particular piece of work which is to be gauged can be conveniently made. Profile Inspection Oange. — On certain classes of work the profile of the piece must be kept within certain limits. It is not always possible or conve- nient to make up a receiver gauge for this purpose and even when one is used, the results obtained do not show up the variations markedly enough. The tise of the ordinate principle can be employed, as shown in the Mgnre 166, in a case of this kind. This system of gauging leaves nothing to be desired where it is needful to inspect for accuracy and to de- termine, at the same time, the variation in the con- tour of the work. This gauge consists, first, of a sur- face plate, A, which has been carefully scraped to a plain surface. On this plate a master-gauge piece, X, is placed and fastened securely in position, and is PEOFILE AND INDICATING GAUGES 403 FIG. 166. PEOFHiE INSPECTION GAUGE furnished with two dowels, D and B, on which the piece to be gauged is located. A dial indicator, F, is mounted on a special block, C, and has a hardened point, G, directly under the gauge or indicator point on the dial. Before using the gauge it is moved over to the plate, B, and the dial is set at 0, the pin then being in contact with the perpendicular side of the Hock, B. After the gauge point has once been set in line and the indicator turned around so that the dial around the work to the various lines shown until the lines on the indicator correspond to the lines on the base plate, A. A reading can then he taken, and if the pointer does not show variation greater than that marked on the plate at the point where the reading is being taken, it may he safely assumed that the work is within the limits prescribed. The system of jrauging can he applied to many forms of work which require a careful inspection of the contour and where TOOLS AND PATTERNS WG. 167. GAUGE FOB DETERMINING CONCENTRICITY it is necessary to know kow much variation there is at various points. Oonooilrieity Indicatiiig Gauge for Higli-Ezplosive .Shells. — In the inspection of high-explosive shells the concentricity of the exterior surface with the inside is important In order to determine this rapidly and without difficulty, the gauge shown in Figure 167 was designed. This is a very simple type of in- dicator gauge and the principles upon which it is based «re applicable to many other forms. The work, A, is placed on the fixture and is located by the lower end, which is tapered, at C and also by means of the sliding tapered bushing at D. This latter bushing is supported by a light spring, E, in order to make sure that there is a contact on both tapered bushings. If this were not so arranged, it might he that the work would be placed in position and located only on one ^d, which would cause a wobble in the PBOFILB AND INDICATING OAUGES 405 work when indicating. The standard on which these two bushings are located may be revolved in the fix- ture, and the work can be turned around freely by hand when in position. As the work is revolved, the plunger, F, which is spring controlled, bears against the outside of the casing and operates the indicating pointer, pivoted at K, and has a fulcrum at G. The lower end of the pointer moves , along the arc of the graduated scale, H, thus showing variations in the concentricity of the work according to the amount of multiplication in the lev«r. In the case noted, the multiplication is 20 to 1, as this is amply sufficient to show variations in the concentricity of the work. The principle shown in this fixture can be used with an indicating dial; it is simply necessary to mount the dial indicator in some way on the fixture so that the push pin, F, will operate against it. loliaiisson Gauges.— Any description of gauging systems which does not include some mention of the testing blocks originated by Mr. C. E. Johansson would be incomplete, although the system is well known throughout the country. Briefly stated Johansson standard gauges are parallel-lapped blocks, in which the two opposite sides of each block are per- fectly parallel and the distance between them is equal to the size marked upon the block. These blocks are furnished in a number of sizes, so that any dimen- sion up to the limit of the various blocks can be obtained by placing the surfaces of blocks marked to the sizes required against each other in such close contact that a measurement across the blocks will give absolutely the dimension required. m TOOLS AND PATTERNS All Johansson standard-gauge blocks up to 6 inches are guaranteed to have no greater error than 0.00001 imhf that is 1/100,000 part of an ineh. They were originally intended for nse in the tool room only for the quick and accurate laying out and checking of jigs and fixtures, but their applications have become better known until now they are used for checking many varieties of work. The gauge blocks are made up in a number of sets to suit various requirements. With their standard holders for making up a num- ber of blocks to a required dimension, they can be considered as a valuable adjunct to the tool room for checking dimensions, limits, gauges, and other work requiring extreme accuracy. A lengthy descrip- tion of the Johansson system of gauging is unneces- sary, but it is safe to say that no manufacturer who is engaged in the production of interchangeable work or any kind of work requiring extreme accuracy can afford to be without a set of these gauging blocks. CHAPTER XX? PATTERNS . The Use of Patterns.— A casting which is to be machined must be made by a pattern. The simplest form of a pattern may be identical in sha.pe and size with the piece which is to be made; but, on the other hand, the pattern may differ quite Widely, depending upon the construction of the piece, the number of holes in it, and whether it has ribs or protuberances of different kinds which may necessi- tate that it be made up to provide for the use of core boxes or core prints. Speaking generally a pat- tern is a form which can be laid in damp sand or some other plastic material such that when molten metal is poured into the mold the desired shape will be re- produced in metal. Usually the outside of a pattern has the general form of the piece which is to be moulded and differs from that piece only in the various pieces called core prints, which stick out from the patterns here and there according to the require- ments of the work. Patterns are usually made of wood, but they may also be made of metal, rubber, plaster, and occa- sionally of other materials. Begardless of the ma- terial used, however, the pattern itself does not differ in form nor is the result obtained greatly different. m 408 TOOLS AND PATTERNS In work requiring a great number of pieces of the same kind, metal patterns are more commonly used, as they are more durable and will stand handling much better than the wooden. For work that is comparatively small and involving a number of pieces of the same kind, a number of small metal pat- terns can be made np and arranged in the mold about a **gate," so that a great many castings can be made at one time in the one mold. Wooden jiatt^nis and metal patterns are made in practically the same way, the difference being that the metal pattern must be cut and worked into shape with different tools than those used on the wooden pattern as it is obvions that metal cannot be cut properly with wood-working tools. Freqnently, in the making of a metal pattern, a wood pattern is first made which is a little larger than the work is to be, so as to allow for finishing and also for jdirink- age, and a casting is made from it in some kind of metal which can be conveniently worked. This cast- ing is then used for the metal pattern after the pat- tern maker has worked it np to the desired size. Form of Pattern.— In making a casting, the first thing for the pattern maker to determine is just how his work is to be molded. The important point in this connection is the withdrawal of the pattern from the sand which has been rammed around it. If the pattern is simple in character, no great difficulty should be experienced in this matter; but if the work has a number of bosses or Ings and is of a peculiar shape, the matter of molding must be carefully con- sidered by the pattern naaker in the making up of PAffBENS 409 his patterns. Obviously, it is necessary for the pattern to be made in such a way that the molder can with- draw it from the sand without disturbing the im- pression which the pattern has created in the sand The pattern maker must always possess foresight enough to make provision for removing the pattern from the mold after the sand has been paxjked ^"^MelJdd of Molding.— The best way to understand thoroughly iust how a pattern is molded is to describe the process in connection with a simple pattern, sncn as that shown in Figure 168. In the first place it must be recalled that the fine sand used for mold- ing is moistened slightly so that it will hold together in the flasks into which it is pounded or rammed around the pattern. These flasks are of various kinds, but in their simplest form they are boxes open at top and bottom and made either of wood or metaL The boxes are provided with lugs on the sides through which dowel pins may be passed so that two flasks can be put together in snch ^ way that l^ey always bear the same relation to each other. They can then be separated and replaced at will, with the - assurance that the parts of the mold m the^ sand will correspond. The upper half the flask is t^^^^ -cope- and the lower half is the -drag" or -nowel. limll be noted that the pattern shown at A m Figure 168 is what may be called a ''solid or one niece" pattern and that it has no core in it. It may be said of this pattern, therefore, that it leaves its own core in the sand and does not require anything special in its construction. This particular piece is 410 TOOLS AND PATTERNS an exact model of the casting which it will produce and is a good example of the simplest form of mold- ing. The shape of this particular piece is such that file angles on both outside and inside give an excel- lent draft, permitting the work to be removed with- out disturbing the sand in any degree. When the FIG. 168. METHOD OP MOLDING A SIMPUS PATTERN molder prepares to mold this pattern he takes a large flat board, such as that shown at C, and places it on Ms bench. On this board he places the pattern, A, with the large side down; over it he puts the drag portion of the flask. He then sifts or riddles" fine sand all over the surface of the pattern and rams it tightly. After this has been done, he fills the re- mainder of the flask with coarse sand which is also ranomed tightly, just filling the box flush to the top. PATTERNS 411 The entire box is then turned over until the cope side comes upward, as shown in the illustration. The ex- posed surface is now sifted or covered lightly with parting sand— that is, white beach or river sand. This is done to prevent the cope side of the flask from sticking to the drag. The cope side is then placed in position over the drag and the entire box filled with coarse sand, rammed in. Cope and drag are then separated, the pattern carefully removed from the mold, the cope replaced, and the flask is ready for molding or is set aside until required. Cores and Owe Boxes.— If the casting to be made requires a hole in it and, because of the shape of the pattern, it is not possible to place the pattern in the mold (as in the instance noted) in such a way as to leave a pyramid or conical portion of sand in the mold that will prevent the metal from flowing into that part and thus leave a hole in the resulting east- ing, it will be necessary to make a separate ''core." For example, in Figure 169 a separate core is neces- sary on account of the shoulder on the inside of the work. Thifi requires that a core box be made specially for it. Cores may be made from metal, dry sand, or green sand. The kind illustrated in Figure 168 is the green sand core and is made at the same time that the mold is made. There are occasional instances when a green sand core can be made up separately and placed in the mold, but these cases are rather rare and need not be considered here. Metal cores are chiefly used in brass work or other work in which considerable accuracy is required. They are not nsed 412 TOOLS AND PATTERNI JjSj m C — — Core Frmf I • • • • . • • . • .1 1 I ■ . • . • . • • • . • ' • • • • ' . • WG. 169. MOLD AND PATTERN SHOWING USE OF BAKED CCMHE in molding cast iron. The most common form is the dry sand core. This is made from a fairly coarse sand mixed with «ome binder material to hold it together and then baked nntO perfectly hard and thoroughly dry. Dry sand cores are molded in core boxes made np to the shape and size desired. Core boxes are nsnally made of wood in two or more parts, depending some- what on the shape of the core itself. The making of core boxes for jyattems is fnlly as Important as the making of the pattern itself. After the core box has been made, the mixture of sand, with the binder thoroughly incorporated in it, 13 plae^ in tiie core box until it is filled completely. PATTERNS 413 It must be remembered that the core in the box is stable, but when removed it is somewhat delicate. In some cases, then, it is necessary to reinforce the core sand by means of rods or bars of different shapes to conform to the size of the core and its contour. After the i5ore box has been filled, the core is removed, laid on a plate, and placed in the oven in order to dry out. It is then ready for use in the mold, having first been given a coating of blacking with a composition of plumbago or graphite, in order that the molten metal may not stick to the core. Eeferring to the pattern, A, Figure 169, a core print, as it is termed, is seen at each end. There is a taper on the upper of these prints, for it is on the cope side of the mold and the cope could not readily be removed unless this part of the print were made tapering. Occasionally the tapered end of the core print is removable, so as to make it easier for the molder to do his work. Otherwise the molder will bore a hole in his molding board to accommodate this end of the print when ramming up the pattern. Beferring to the casting, B, shown in the same illus- tration, an inside recess is seen of such a form that it would be impossible to mold the work from a pattern without a. separate core. Thereforei|||^^ is made up to give the form indicated at c7and after the pattern A has been rammed in the mold, this core C is inserted prior to the molding operation as in- dicated in the illustration. When the metal is poured into the mold it will flow all around thi« coJe and into the depression left by the pattern form, thus pro- ducing the desired shape. After the iron has cooled 414 TOOLS AND PATTERNS and the mold is dumped^ the core, being of a fragile nature, can easily be broken up and knocked out of the casting, which is then left in the condition shown atB. Two-Pari Pattarn and Melliod of Molding.— The casting, A, Figure 170, is seen to have flanges at each end of such form that the casting could not be molded in the same manner as that shown by Figure 169. In work of this kind the better method is to make up a two-part pattern, as shown at B, and prepare to mold the work as indicated in the illustration. It will be noted that this two-part pattern is separated on the center line and that there is a dowel pin, C, at each end of the pattern so that the two parts can be placed together in their correct relation at all times. In molding, one-half of the pattern is laid down on the molding board and the drag portion of the mold is rammed up around it. The mold is then turned over and the other half of the pattern laid on to. its fellow, after which the cope side of the mold can be rammed. After lifting out the pattern and placing the core in portion as noted, the work is ready for molding. ' Occasionally in cheap pattern work it may not he desirable to make a two-part pattern. When this is the ease, the imtlhod shown in the lower part of the illustration can be used. In tMs, the pattern is made in one piece, and the molder lays the pattern down on his molding board and rams up the mold in the drair portion. He then turns over the drag, as indi- cated in the illustration, cuts down the slope, D, PATTERNS 415 c LP u Pa /fern ^•^^^:r^ll^: •.v J % COPE:,' 'In jx. FIG. 170. TWO METHODS OF MOLDING A PATTERN WITH FLANGES Upper figure shows the split-pattern method. Lower shows solid pattern. with his molding tool, and removes the sand down to the center line of the pattern, leaving it all clear and clean. After sifting parting sand on the drag portion of the mold, he places the cope flask in position and rams this up also until it takes the form shown in the illustration. The cope can then be lifted care- fully off so as not to disturb the sand which is hang- ing below it, and the pattern can be removed and the core inserted as in the previous instance. TMs TOOLS AND PATTEBNS method of moMing is seldom used unless only one or two castings are desired from a certain pattern, for too great a portion of the molder's time is taken up than the work warrants. Girviilar Oovw PatteriL— Figure 171 shows a some- what different type of pattern. Here the work to he produced from the pattern is shown at A, and the method of molding the piece is indicated in the lower portion of the figure. In this case the parting line of the pattern is at C; there is a projection into the cope of the pattern itself, and also the portion, B, of the cope extends down into the pattern. To use this pattern it must be laid down on the molding board and a suitable recess provided for the flange no. 171. ontcuLae ooveb pavcebn showino pabt of the MIXi> IN THE OOFE SIDE PATTERNS 417 portion so that the parting line, C, will lie flat on the board. The sand is then rammed around the pattern, after which the drag is turned over in the usual way and dusted with parting sand. The cope is now placed in position and rammed up, the sand being forced down into the portion B, and lifting out as the cope is removed so that the part, B, remains hanging from the cope side of the mold. Pattern Requiring a Thrw-Part Flaak.— In some instances it is necessary to mold a certain kind of pattern in a flask containing more than two parts. An instance of this kind is shown in Figure 172 where the work. A, is a casting having four ribs and a flange at each end. It is apparent that it would not be possible to ram sand all around the pattern and then be able to remove it from the sand without dis- turbing the mold. The pattern is made up, therefore, in the form shown at B, the usual core print being applied and the pattern itself being arranged so that it can be separated along the line X-T. The process in molding this pattern is as follows: The large flange is placed on the molding board, the cheek" of the three-part flask is first rammed up as far as -the separation of the pattern X-Y, the cope being then placed in position and rammed in turn. Both cope and cheek are then turned over together on to the molding board and the drag side is com- pleted. In removing the pattern, one part is drawn from the large flange side and the other from the small flange side. The core can then be placed in position in the usual way, and the mold is ready for pouring. 418 TOOiiS AND FATTEBNS MG. 172. EXAMPLE OF MOLDING A FLANGED AND KIBBED PATTERN IN A THREE-PART YLASK. Other Forms of Patterns.— It is not necessary to present a lengthy discussion of the various forms of patterns, but several other kinds may be mentioned in a general way in order to make the snbject a little clearer. The matter of loose pieces i-s one which occa- sionally gives the pattern maker and molder more or less trouble. For instance, in making a casting that has a number of lugs or bosses on it of such a kind that they could not be readily removed from the molds, the pieces are frequently made loose with a pin in them to permit their ready removal. In molding PATTERNS 419 such a piece of work the pins are removed from the loose pieces before the pattern is taken out of the mold; the pattern can then be removed without dis- turbing the loose pieces which can be taken out by the molder 's hands afterwards. The type of patterns known as "sweep" patterns should also be mentioned. These are used for circular work when a very cheap pattern is desired. They can be made for almost any kind of cylindrical ring, and if made in sectional form to take up a certain portion of the mold desired, this part of the pattern can be attached to a radius stick pivoted at the cen- ter of the mold and a part of the mold rammed up at a time. After one section of the mold has been pre- pared in this way, the sweep can be moved around to another section which is treated in like manner. Skeleton patterns may also be used in a somewhat similar way. But attention should be called to the fact that each of these types just mentioned is used for the purpose of economy where only a very few eastings are to be made from any one pattern. The skeleton pattern is used in place of a complete pat- 1 tern, but its principal claim to distinction is that it can be made up cheaply for cylindrical work. While the pattern maker saves considerable time in making either a skeleton pattern or a sweep, the molder, how- ever, is required to spend very much more time in making up the molds than he would do if he were provided with the proper kind of pattern. Tools for Paittem MaUiig.— The tools used in pat- tern making are much the same as those used by any carpenter, except that a number of varieties of spe- 420 TOOLS AND PATTERNS ml tools are required, sucli as those used by the cabinet-maker and wood-carver. A number of spe- cial machines are in use in the pattern shop in order to facilitate the work of pattern-making. These in- clude such special machines as the core^box machine, which is specially designed to assist in cutting out the inside work in a core-box, and also sand-paper- ing machines of the disc type with adjustable tables to permit them to be set to different angles for the greater convenience of the pattern maker. Other tools used in the pattern shop are the circular saw, the band saw, the hand jointer or buzz planer, the mortiser, and the shaving machine. Special pattern- maker 's vises might also be mentioned, which are so constructed as to hold the work in any desired posi- tion withimt injury. The tool-maker's engine lathe is also found in the pattern shop and is largely used. In addition to all the above, each pattern maker has his own private supply of hand tools, most of which have been made up by himself for certain kinds of work which has been out of the ordinary. Aside from these, the cabinet-maker's or carpenter's kit of tools would represent general usage. CHAPTER XXVI PATTERN BEGOBDS AND STORAGE Desirability of Pattern Records. — ^Keeping patterns after they are made, in a safe and readily accessible place, is a matter that has deservedly received con- siderable attention in late years. Formerly, the boss pattern-maker had a system of his own; he located any desired pattern in from ten minutes to three or four days, depending on his memory and the amount of time he could spare in looking it up. The boss pattern-maker frequently was, and still is, a man who had held the position for a number of years and who might be expected to know what a given pattern looked like and where it was likely to be found. Memory is a poor thing to depend on, however, for locating anything, and the results from the sud- den death, illness, or resignation of the man having this store of knowledge can well be imagined. Con- sider the amount of time consumed by the boss pat- tern-maker under ordinary circumstances in finding a given pattern and estimate the cost of finding the pattern under these conditions. However, it is gratifying to note the progress made in this respect among present-day manufac- turers. Nearly all of them now-a-days have a well- ventilated, light, and convenient pattern-storage 422 TOOLS AND PATTERNS building, with suitable racks or compartments in which the patterns are kept. In former times it hap- pened not infrequently that the loft (if there hap- pened to be one above the pattern shop) was utilized for storage, and it took a man with a searchlight and a pair of good eyes some time to find what he wanted. Quality of Patterns.— Before going into the matter of pattern storage and records, I should like to say a few words in regard to economy in the construction of patterns; for it is always a good plan to consider other things in addition to the first cost of a pattern, and there are many factors affecting the construc- tion. It is obvious that the number of pieces to be made from a given pattern is an essential factor in deter- mining the character of the pattern. For example, a jig or fixture pattern is usually made as cheaply as possible, for it will only be used once or twice. Any other sort of pattern for a special machine or mechanism, which will be used for only one or two castings, would therefore seem to come under the same category, but here other factors vitally affect the construction. A special machine may be de- signed for use in a manufacturer's own shop, or it may be sold to a customer; in either case th^ appear- ance of the finished machine must be considered, and therefore the pattern should be well filleted, with comers rounded, and finished throughout so that the castings obtained from it will be of good appearance. Speaking generally, it is not necessary or even de- sirable to give patterns of this kind a high finish PATTERN BECOBDS AND STORAGE 423 with several coats of varnish. A good sandpaper finish is usually sufficient, although a coat of shellac is a very good protective covering that may preserve the pattern in better condition than if it were left without it, in the event that other castings may be wanted at a later date. These matters are generally left to the judgment of the pattern-maker when he is instructed by the foreman as to the kind of pattern wanted. Usually in making a pattern for a single castmg, the warping of the wood from which it is made and the consequent distortion arising therefrom are not taken into consideration, so that if another casting is desired at a later date, it may easily happen that the results obtained in the second case are unsatis- factory. If there is a likelihood of a pattern being used a second time, provision should be made to pre- vent undue warping. However, attention to this mat- ter should not permit too great an addition to the first cost of the pattern. Judgment should be used in all cases. Patterns which are built up in sections, with the grain of the wood running in opposite directions, are not generally desirable for single casting work on account of the first cost of the pattern; but when the shape of the work is such that there is strong likeli- hood of distortion, the pattern should be made sub- stantial enough to counteract any tendencies of this kind. For patterns which are to be used over and over again, the first cost should jg||||||p5ondary considera- tion. A poorly built patter|||ii||: o'ut of shape and TOOIiS AND PATTERNS become so damaged by frequent molding that it will soon need to be replaced by another. Of course, when the size of the work will permit it, and the number of castings to be made warrants the expendi- ture, a metal pattern is most satisfactory. The cost of a metal pattern, however, is very much greater than the cost of one made of wood, so that it is un- economical to use metal unless a great many pieces of the same kind are to be cast from the same pat- M tern. In machine-tool patterns there is always a pos- sibility of a change in design of the machine. This may make an entirely new pattern necessary, and therefore metal patterns shonld be rather sparingly used for work of this kind because of their expense and the likelihood of an early discard. Economy in Ctombination Patterns. — In the making of pnlleys or gears with spokes, which require sev- eral pieces of the same diameter but with different lengths or sizes of hubs, considerable economy can be effected by using one spider and ring pattern with loose bub pieces of different lengths and diameters. A combination of these loose hub pieces with the spider and ring will meet a number of different con- ditions. The spiders can also be made with a vary- ing nnmber of ^kes and the pulley rings can be made in different widths so that a wide variety of castings can be obtained. Hubs and spiders can be so made as to be interchangeable one with another, so that with only a few complete patterns combina- tions of all kinds can be quickly and satisfactorily effected. PATTERN RECORDS AND STORAGE Gear Molding Machine.-Another great economy in pattern making has been the development of the gear molding. This permits a special pattern to be made in sectional form which has only one tooth space on the rim and a part of a tooth on each side instead of an entire pattern of a gear with teeth all around it more or less accurately spaced a«oo^dmg to the skill of the pattern maker. The gear molding machine takes the sectional pattern and molds the remainder of the teeth far more accurately than is possible in any other way. Pattern Records.-Having considered the inakmg of the patterns and the economies which can be put into effect in their construction, let us see how we can best take care of them after they have been made, and how we can locate them when wanted without resorting to memory. It is apparent that any record for patterns must be based on the method used in identifying any component part in the class of work being manufactured. Thus, if machine tools are being made, the system used should identify the machine by number or name, the part by number and name, and the location of the pattern in its rack in the pattern storage building. It is useful also to have the date that the pattern was made, its cost, and the weight of casting incorporated in the index, together with information regarding core boxes and a record of castings made with date of order, ete. Figure 173 shows a simple index card that is ap- plicable in recording the patterns used m making machine tools. ,j v, i.i„j In any record of this kind the cards should be filed 426 TOOLS AND PATTERNS Machine Na_/^.. Piece No.„Z&L^ „ Naffiw of Hect— .5^&f^^±^-, Location EiiLtQ Patterns / Core Boxes ? Dale Cast* (s Ordorcd No. Whara Ordarad Weight Prica Cost m. ^. s /ff / - STOEAaE OF CRUCIBLES 433 easily controlled and not so severe in their action as burners which are designed for low-pressure oil and high-pressure air. In mmkg fuels, those which have a high content of sulphur form sulphur dioxide, whiiek is very injuri- ous to crucibles. Such fuels, therefore, should be avoided. Crucibles will last much longer if the metal is poured as soon as possible after the proper tem- perature has been reached so that they will not be subjected to the burning action of the flame any longer than is needful. The life of crucibles continu- ally kept at high temperatures is comparatively short. It is of advantage, therefore, to use a crucible first in melting alloys requiring high melting points, then, as it grows older, prolong its life by melting alloys requiring a lower melting point. It is necessary, of course, to clean out any alloy of one kind thoroughly before using the crucible for another alloy, in order to prevent hybrid mixtures. No mat- ter what melting points are used or what alloys are melted, care must be taken in charging the pot not to crowd it full of scrap or heavy ingots of metal, as the expansion of these in melting is sometimes suf- ficient to crack or otherwise shorten the life of the vessel. Crucibles will have longer life in round furnaces than in square ones, because the heating is more uni- form in the former. For this reason tilting furnaces are easier on crucibles than pit furnaces. In using a pit furnace the life of a crucible is prolonged by plac- ing it in the furnace to cool gradually with the fur- TOOLS AND PATTIBNS nace rather than to let it cool in other atmosphere and under various conditions. A protective paint or a wash made of pulverized carbonradiim fire-sand mixed with water glass or boric acid, has a resisting effect and prolongs th^ life of a crucible to some extent. A coating of this kind has been nsed sucessfuUy in Europe and has recently been put on the American market INDEX. MMultwm Aftiicial. 07 Ai^taUe FlztnM for ChMtag 9pw Gears, 248 AilMteWs Borlag Tool for Tta^ Room Work, 48 — yertieal Botteg KUk, StO •-^rinding, for UaHmHil Joist, 241. 246 ^late Hilling, for Qaoatltj FM- dvetion, 150 — Kstnre and Variety of, 139 — ^Simple, for Machining an Eccen- trie. 2S1 ^Sliding, for Boriag * FHir of Cylinders. 233 — -8poci^, with Tfcp o nfl Ii»> cater, 224 — Straddle-Milling, for a Obaaoet- tittg Rod, 141 — Swinging Eccentric, 178 — ^with Adjiutable Coanterbalanee, ITS — with Safeguarding Devices, 172 Tlangt, Automobile. Bnp^aiHng Arbor for. 186 Flask. Molding, 409 Flat-Cnttor Boring Bars, 48 Flat Twist Drills. 38 Flood Lnbricatioii. for Cnttias. MMI Flnld Gauge, Prestwich, 880 Flush-Fin Gauges. 385 — I>ottb]*, 800 — for Contours, 380 — for Tapers, 388 —with DM iBdicfttor. Stf Fluted Beamers. Plain, 42 Fljwhoel, Automobile, Fixtnro for, 224 Vmw VN^ DeAnltion of, 840 — Table of Tolerances for, 854 Ford Motor Flaat an Ezauplo of Plna- nhig. 818 fbrgod Tools. 1 — Varieties of, 19 Vorging, Drop, Principles of. !• Follow Dies. Example of, 32 Formed Milling Cutters, 81 Form Grinding, External, 106 W&mtng and OrooTtef AttadOMBl for Pistons, 206 Forming Attachment, Radius, for Crowning P)dlev«, SOS Forming Dim, 32 Forming TooU^ 68 — Ofarenlsr. Tl — ^for Turret Lathe W4ffk, ftf — ^Rectangular, 68 Wmm ■nUng; nxtnr* for. 148 Vtnnia for DetsnriBlaf Oiittiag Speeds, 302 VMT-Jawtd Independent Chuck, 181 Vfif^Wagr K«]rw»F BroMhes, 04 Tnm ITmi SketohM In iMglmg Out WoriE, 880 Gang Dios, EzMnple of, 88 Ooag MiniBg; FIstnro for, 145 OM-Control Plate, Set-on fttr. 107 OMgoSf Ames Dial Test. 380 — OoMtntrieity Iniientiag. 404 — Xloetrical Contact, 401 — Kxtemal, 364 — ^Feeler, for a Crank Shaft, 399 " F l w nale Thread, 874 — Plush-Pin, 385 —Indicating, for a Cam Shaft. 806 — Indicator, for Toatiag AUgaaMat, 391 — ^Internal Limit, 857 ^latmial TupiKr, 800 — Johansson, 405 — Master, for Female Tapor Gangea, 878 «^tec«r, tm Mala Tt^m Oaagai, 801 Micrometer, 878 — Plug, 858 —Prestwich Fluid, 880 «^ProiUe and Indicating, 370 — ^Proila Inspection, 401 . -—-Receiver, 870 — Ring, 868 -^a«|>. M6 — Taper Ring, 171 — ^Templet. 867 -—Thr aa d, Malo. 801 Oaaging, Terminology of, 340 Oaarod Scroll Chucks, 129 Oaicii; Bovd Ring, CMnding nztnra for. 251 — ^Bevel lUng. Vertical Turret Latha AttaeHMiMit for, 216 —Combination Patterns for, 424 —Double Bevel, Expanding Arbor and Faceplate for, 226 •"-^Uag, Cross- Slide for Ctoaaratiag Angular Cut on, 208 —Spur, Adaptable Grinding Fix* ture for, 248 Ooar Molding Machine, 425 Ooar-Tooth Milling Cutters, 81 QcOaMBg Angular Cut on Ring Gears. Cross-SUdo for, 208 — Curved Surfaces, 200 Oonerating Attachment, Angular, for Vertical Turret Lathe. 110 OO and Not Go Gauges, 358 ttOiM-Heck Threading Tools. 67 IMPIX Oiapliiie OxwdUev, Ctmmmm ef» 480 — ^Manufacture of, 430 Offniifig^ Bxtemal Cyllttdrl«»l. Hold- ing Work for, 239 — ^External Forms, 106 —External Tapers. 106 —Interior of Amtomeblla Cf ii»d«a. Spur Gears, 248 —Adjustable, for Bevel Pinions, 250 —for AutomobUe Pieton, 248 qrtB#itg nztnza for a Large Bevei Ring Gear, 251 —for Universal Joint, 241, 240 —Internal, fer a Ball-B«tfliit CSaga 244 — ^Internal, 107 — Surface. 100 Grinding Tool*. 24 Orindlng-WheelB, Shapes of, 99 OtoavlBg Attachment for Pistons, 200 MMtoaws, 10 „ . , Bkad and Forged Tools, 1 Bind Lever, Automobile, Jig «», 274 Biad Vises, 114 . „ , Bead. Multiple Turning-Tool, 62 Bob MilUng Cutter, 88 ig ^tMmirm for Tapa and Diee. 180 — for Tools, 25 BttMiBf Work, Necessity for. l» »"i- 'tng, 140 ^ - Belii, Cf^mmeal TUg Ganges for, — in^p ftirghige. Method of Fm- —Round, Broaching Cut for, 8» -—gonare, Broaching Cut for, 91 —Standard, Table of Tolerancea for, 352 mmmr Mins, 55 — Types of, 56 - , Boiiiontal twwl Lubrication of. for Drilling. 296 M Flange, F»ee-Plate Fixture for. 167 independent Chuck, Pour-Jawed, 132 Index Milling a Pair of Levers, 149 ■^-SHxtiife for ^ttihtlfsr Pw>«tt«tlon. 150 XBdaz of Machine Tools, 319 of Pattefjil. 415 Indicating Gauge for a Cam Shaft, 396 — ^for Concentric Surfaces, jmU fff ^ Oaage for Teatiag Align- aaent. 391 SaUeiMen, Dial, 379 maected-Blada Milling Ctttler. 85 — Reamers. 43 InspectKm Gauge, Profile, 402 Instnuaeota of Preetsloa. 877 Interchangeable Manufacture, 3 — ^Degree of Accuracy in. 346 Interchangeable Work, Limito for. 851 Interlocking Milling Cutters, 86 Intamal Grinding Fixture for a Bali- Bearing Cage, 244 mitail Grinding Methoda, 107 — ^Limit Gauges, 357 —Radius Boring Attachment, 117 — ^Taper Gauges, 359 magnlar Bratikal» Face-Plate Fixture for, 172 nge. Closed, 270 ^-for Automobile Hand Lever, 274 —for an Oil-Puinp Bushing, 270 -for a Rod »mppmUa€ Bracket. 272 Jig, doeed Drm, for a Beaviag Gep, 276 -*-for a Crooked Lever, 283 ^for an Eccentric BusMng, 178 for a Radius Bracket, 280 Jig Drill, for an Oil-Pump Cover, 260 —^Functions of, 258 Jig, Open, for i Lever, 261 for a Lever with Stud Locator, 263 — for a Small Bracket, 264 Jlgt, nnte, with Svpplementary 8«r porting Ring, 258 71gi Set-On, ioT a Gas-Control Plate, 167 »for a Traaemlailon-CaBe Cover, 266 Jigs, Simpio Floie, for DriRlng. 156 Jlg^ Trunnion, for a Tmaavieaion- Case Cover, 284 Johansson Gauges, 405 Xno^-Off Arboct for Threaded Col- lars, 106 —Threaded, 194 Threaded, for Vertieal Bonng MiU, 235 BiVVlV BvMdMt, 01 I«rd Oil as a Cutting Lubricant, 101 Lalhn^ Plain. Arbor fi». 181 Xisfha fooUi Gnttittg Aetioa of, 18 442 timating Costs, 340 Lajrinc Out Work in the Machins Shop, 817 • SifiNt of Jigs. FixtvM, TMdi, maM Oaaeres, 322 ~of Maehine-Tool Equipment, 319 — of Operations, 318 — of Operation I^Mta, 323 — Sheets, 330 Imd of Thread, Definition of. 889 £«for, Crooked, Drill Jig Utt, 988 — ^Hand. Jig for. 274 --Mis MflHiig • P»ir of. 140 — Open Jig for, 261 — Open Jig for, with Stud Locator, M8 Limit, Definition of, 350 Limit Gangea, Internal, 357 — ^Taper, for latonal Tapered Holo^ 360 Halting Dimensions on Drawings, 856 Itetts for Interchangeable Work, 351 iMBtlng WSHt; y-Blodi Friaeipte of. 170 Lubricants, Composition of, for Cut- ting Ahuninum, 298 — CompoaMoiB of. Inr Onttfag Stool. 893 •—Sffoot tit «i CHrttfBff Spooia wmA Wmis, 309 StW M M a of. for Removing Chipa. 995 IflfMcatlng a Horizontal Ttamt Lath*. IntemaUj, 295 — • muTOt Latho through the Spin- die. 296 — a Vertical Turret Lathe, 299 Lnhrleatimi, Flood, for Cutting, 298 —Off Cuttiag 1Mb, 999 Machine Equipment. 119 — ^for Molding Geara, 425 MiAine-Tool EquipMU, 919 — ^Index, 319 ~Sooor4 Card. 991 Machine Vises, 134 lAkgic Ohuek, 121 Mif OHff OfeMfca^ 940 — Description of, 100 Male Master Gauge for Testing Fo- male Taper Gauges, 878 — ^Taper Qfl«9«» B«tarOM« QMfa fM; 361 — ^Thread Gauge, 362 Mandrel, Definition of, 181 Manufacturing Details, 1 Manofacturing Vises, 134 jfaitiiig the Pattern, 490 liMlor Gfttigw for Malo Tmpw &m9m, 361 — for Female Taper Chragoa, 878 Metal Patterns, Advantages of, 424 Micrometer Ganges, Constmction Foft- twrea of, 878 Uniiiif Wima, Angiriw. 79 — Formed, 81 — Gear-Tooth, 81 — ^ob, 83 — Inserted-Blade, 85 — Interlocking, 86 — Plain, 86 — Shell-End. 77 —Spiral, 75 — Straddle, 85 — Straight-Fluted, 75 miling. Gang, Fixture for. 145 — Prooeases, 79 XUling Machine, Aitor for, 182 — ^Factora Influencing SoloctioB of; 78 Mills, Hollow, 55 MlBnal Oil aa a Catting Labrieaat. 391 MBlilBg a Flanged and Bi¥bod Pat- tern, 418 — Clay Crucibles, 429 — Method, 400 Molding Bfachlne for Goan. d9S Molding Sand. 411 llona Tkpw, 180 MOtlple-Splndle Drilling MacfMliaa, DriU Jigs for, 253 Ifalll^YaniBg Tool Head, 09 Natural AbzaaiTea, 07 Vawall BBftnoozliic Co.. TaUo of Limits, 355 Vowel, Definition of, 409 Vut, Adjusting, Expanding Arbor fw. 188 on aa a Cutting Lubricant, 291 OlliBff ARaafUMmt. Intwaal, for Drilling on HoriaoBtal Torrot Lathe, 296 Oa-Pamp Cover, Drill Jig for. 900 — Shaft, Bushing for, 970 Opon DzlU Jigs. 253 (^aa Jig for a Lover, 861 ^or a Levar witk Stai La oato r . 263 —lor a Small Bracket, 264 O pt S ide Turning Toola, 60 (^ration Layout, 318 Operation Sheets. Layout of, 328 INDEX 443 Overhead Expense, Estimating the. 848 Orerhead Turning Tools, 60 Packing Bing, Eccentric, Special Arbor for, 198 — ^E6centric Turning and Boring At- tachment for, 209 — ^Fixtures for Cutting, 166 PaddBg Ring Po^ Swinging Becentric Fixture for, 179 Parallels, 112 Pattern Makers' Tools, 419 Pattern Records, Importance of, 421 — Cards, 425 Patterns, Circular Cover, 416 —Combination, for Pulleya and Gears, 424 — Composition of, 407 —Construction of, 408 —Finish of. 422 —Fire Protection of. 428 ^Flanged and Ribbed, 418 — ^Index, 425 — Location of, 427 — ^Marking System for, 426 — Metal, Advantages of, 424 — ^Method of Molding. 410 — One-Piece, 409 — Quality of, 422 — ^Ring and Spider, 424 — Sectional. «98 — Skeleton, 419 —Sweep, 410 — Three-Part, 417 — ^Two-part, 414 — ^Warpage of, 428 Pallani Stoxaga Building, 421, 497 — ^Fire Prevention in. 428 — ^Method, 427 Pivmaaeat Tools, Definition of, 5 Parishable Tools, Definition of, 5 Plaoo-Work Prices, Determination of, 885 Pfloltd Turning Tool tor Rapid Pro- duction, 61 Pla Chock, Expanding, for a Piston, 199 MiaiB% Bavel, Adjustable Grinding Fixture for, 250 — ^Expanding Arbor for, 180 —Turret Lathe Attachment for Gen- erating, 211 Pipe Vises, 117 • plalOB, Automobile, Expanding Put Chuck for, 192 — Cast-Iron, Time-Study Sheet on. 333 — Caat-Iron, Tool and Operation Sheet for, 824 — ^Forming and Grooving Attach- ment for, 206 Generating Curved Bnda of, 901 — Grinding Fixture, 243 — ^Prestwich Gauge for, 388 ^Tool Layout Sheets for, 328 Plata Chucking Reamers, 42 — Fluted Reamers, 42 — ^Milling Cutter, 86 Plata MUCttag, Fixtures for, 189 plaaing Tools, 87 — Chatter in, 22 — Cutting Action of, 21 jpiannlng, Business Aspects of, 313 Plata Jig. Simple, for Drilling, 256 ^irlth Supplementary Supporting Ring, 258 Plug Gauges for Cylindrical Holes, 857 Plag Locator, Tapered, for Holding a Flywheel. 224 Poppet Valve, Receiver Gauge for, 371 Pooling the Crucible, 433 pfoelia Measuring. 877 Prestwich Fluid Gauge, 380 PxlBCiples of Drop Forging, 26 -^f V-Bloek in Locating Work, 170 Praflla and Indicating Gauges, 876 — ^Inspection Gauge. 402 PMgxosai^ft IMas, Example of, 82 ptiBoya, Combination Patterns for, 424 — Faeing on Vertical Turret Latho, 814 — ^Forming thO Crown of. 208 Plih Fit, Definition of, 347 Table of Tolerancea ftor, 854 Ponp Oofir, on. Drill Jig for. 900 llultly of Patterns, 438 Badiaa Boring. Internal, Attachment. 917 Badins Bracket, Drill Jig for, 280 Badtaa-Porming Attachment for Crown- ing Pulleys, 203 tttMoB-Qaa/vnlting Attachment for a Vertical Turret Lathe, 214 — ^Attachment, Simple, for an Ba- gine Lathe, 901 Baamers, 41 — ^Inaerted-Blade, 43 —Plain Chucking, 42 — TltAn Fluted. 42 — ^Rose Chucking, 42 — Tap^. 44 INDEX BMMSing Tools, 50 — for a Large Steel Casing, 54 — 4tor Tmnt WtoAt, tS — on an Enjcine Lathe, 51 Bacord Cards for Patterns, 4SS —of MaeMM Voals. tSl Records, Pattern, Importance af, itl Bftangator Forming Tools, — MagMlie OmOm, 240 Caference QsagM^ Vlniili|» MS —Male 378 BMti^ Roller-Back, for Adjustable Turning Tool, 59 BliS and Spider Patterns, 424 ■tug CNMigas for Cylindrical Work, 368 — far Tq^rs. 372 Mai Gear, B«vi|» CMa4iaf VIztaM for, 251 — Tarlieal Tmmii Latka Attadi* ment for, 216 Mng €toan, Cross-Slide for Oanerating Angvlar Cist on, 908 Ring Pot, Pace-Plate Fixture for, 177 — ^Packing, Swinging Eccentric Fix- tw fvt, 1T9 m§A Drill, Vertical B^rimg MM fla< ture for, 235 M-SBpp«rliBf BncMk IMll Jig far, 272 BaOar-Back Bests for Adjwialil* Tam- ing Tool, 59 Rose Chucking Reamers, 42 Rotary Magnetic Chucks, 240 Round Holes, Broaching Cut for, 92 BOTinlng Fit, Definition of. 847 — Table of Talaraaaii faa; M Safatj Davlcas on a Face-Plate Fiz- tare, 172 816 SanpM% 15 — ^Types of, 18 * — ^Use of. 16 8a«M» M easnring tha Laad af, ttt — Templet Gauge for, 368 Scroll Chucks, Geared, 129 Saexvl of Cost Estimation, 340 iMlllMl FlattanM, 4SS Mf-Cmterlng Fixtnra itr • Bobi^ Casting, 168 Sat-On Jig for a Gas- Control Plate, S67 266 asflit Dial Ttat Ganft far T— paattiig. — Limits for Length of, 355 — Tapered, Flush-Pin Gauge for, 388 ShapiBg IMaa, 80 Shell-End Milling Cutters. 77 Shells, Gauge for Indicating Concen- tricity of, 404 Shop EqnlxnBent, Standari, 110 SIda MilUng Cutter, 85 SkilaloB FrtlUM, 419 Sketches, FreO'Hiuid, for Work. 330 aUdlnf Flxtnxa for Boring a Pair of Cylinders, 888 ftolltac t hM m a , 78 Snap Gauge, for Cylindrical Work, 84i — ^for General Dimensions, 366 Soefcata; Drin, 120 Stiawatar as a Cutting Lubricant, 292 g pia da and Faada, Definition of, 801 -4ffaet of Ototttag LsMamI* «b. 309 — General Rules for, 310 — -InportaBca of Prapar, 807 S m ia, Cutting, Forarala Inr Boter* mining, 302 —batting. Table of, 807 — Relation of, to Feeds, 304 Spidar and Ring Pattema, 484 SpiZBl Miniiig Cottars, 75 Spline-MllliBf nztwaa* 160 Split-Ring Expanding Arbor, 184 —Expanding Arbor for mi A4ttMt- ing Nut, 188 Spotting Drill, 36 Spar (Jaars, Adaptable Grinding Fix- ture for, 248 Square Hole, Broaching Cut for, 91 Standard Face Plate for Engine Lathe, 165 — Tool Equipment for the Shop, 110 Steal, Lubricants for Cutting, 208 n&9 Otaeka» 186 aiatafa of Crucibles, 482 — of Patterns, 427 Straight-Edges, 112 Straight-Fluted Milling Cutters, 71 Straddle Milling Cutter, 85 atraidle Milling, Double-Indexing Fix- ture for, 149 MaAdla-Milling Fixtoxa for % Oo» necting Rod. 141 — ^Working ftroa a flaltlMi tafiM, 148 Stud Locator for Open Jig, 263 Sub-Press Dies, 34 Surface Grinding MaOutda. 100, lOS Surface Plates, 111 B m * m fiHtwii-Aio Maflit Sc««atrie nxtar^ 178 INDEX 443 Tandem Dies, 31 Sapazad Hoitb Bolding Wurk If tk^a, 225 Tapered Plug Locator for Holding a Flywheel 224 Tapar Gauge, Female, Reference Gaogo for, 373 — ^Internal, 859 — Male, Reference Gauge for, 861 Tapar Pins, Receiver Gauge for, 370 Vapw Baamaca, 44 Taper Ring Gauge, 372 Tapars, Designation of, 120 Flush-PIn Ganges for, 888 — Grinding External, 106 Tapping Attachment for Drill Press. 128 Taps, Dies, and Holdars, 180 Tao-Slot Cutters, 78 Templet Ganges, 367 — for a Screw, 368 TUB W6rk, Fixture foiv OH Taitiial Boring Mills, 221 Thiaad-Ohaabig Tools, 66 Threaded and Knock-Off Arbors, 194 Threaded Collars, Knock-Off Arbor for 196 Tbttadad Enock-OIT Arbor for Yartf- eal Boring Mill, 235 Tluraad Ganga, Inspaetioa of, by Viaid Gauges, 384 — ^Female, 374 —Male, 869 . Tlfaadlng Tools, 65 — Goose-Neck, 67 Tllna-Part Fattomi, 417 Time Factor in Cost Esttmataa, tST Time-Study Sheets. 332 Tolerance, Definition of, 349 — ^for Push. Drive, and Fwea Vila. Table of. 354 — for Running Fits, Table of, 358 — ^for Standard Holes, Table of, 858 Tool and Operation Sheet. 324 To(d Orlb^ Equipment for. 120 Todl BngtaawrlDf, Importance of, 815 Tool Equipment, 5 — Standard, for the Shop, 110 To«l ikoldera, 25 Ti«l Layont, 322 — Sheet, 328 Tooboakert* Adlnstabla Boring Tool. 48 — Tool Equipment of, 111 Tooll. Boring, 46 —treadling. 01 — Cutting-Off. 84 — Fozmiag, 68 ~~ioT Pattern Making, 410 —-Grinding, 24 Ifand and Forged, Clasiffioatimi of. 7 — listhe, 28 — Perishable, Definition of, 5 — Permanent, Definition of, 5 -splatter. 81, 87 — -Recessing. 50 — Threading, 65 T taMUlaato n-Caaa Ooioi^ 8«t-0n Jig for, 266 --Trunnion Jig for, 284 Tt tn i mtng Dia, Example of, on Rough Forging, 30 Trunnion Jig, 284 Tnnlaf and Boring Attachment, Ec- centric, for Packing Rings, 200 Taming-Tool Head, Multiple, 68 Sttnlng Tools, 57 —Adjustable, witb Roller-Baek Rests. 59 — for Vertical Boring Mills, 62 — Open-Side, 60 — Overhead, 60 — Piloted, for Rapid Production, 61 Tnirat-Latba Attaehmant for Oenatmt- ing Bevel Pinions, 211 Tnrrat Lathe, Box Tool for, 58 — ^Bnllard Vertical. Cuttlng-Lubri- cant System for, 299 — ^Forming Tool for, 57 — Horisontal, Internal Lubrication of for Drilling, 296 — ^Lubrication of. through Spindle, 296 — Machine-Tool Record Card tor, 321 —Recessing Tools for, 52 — Vartical, Angular Generating At- tachment for, 216 — ^Vertical. Radius-Generating At- tachment for, 214 Tvlat Drills, 37 — ^Flat, 38 Tipo-Jawad Olmeka, 127 T«a-Idp Slottliif Outtata, 78 HUvmal Joint, Grinding Fixture for, 841. 246 Valve Stem, Receiver Ganga far. 871 V-Blocks, 116 —Principle of. 170 ¥«ttleal Boring Mill, Expanding AllMr and Face-Plate for, 288 —Fixtures for, 220 Fiztare for » Fragil* Ahuninom Casting, 238 —Threaded Knock-OfT Arbor Ittt, ttS — Turning Tools for, 62 Ytctlcal Tnzxvt Lathe, Angular Gen- orating Attadunent fnr, 116 •— Catting-Lnbricant System for, 299 — Badiaa-0«ii«Tatinf Attaduaeat iwt, SU ViaM» Bench. 117 -—Hand, 114 — Machine ant HaanflMtafing^ IS4 — Hpe, 117 Wazpaga of Patterns, 423 Wom-Oear Hob MiUing Cutter, 88 WtnMtaV' SmIm^ ^Ifartaw for, 176 COLUMBIA UNIVERSITY UBRAIUES lB^mm» date iniksM Moir, or alfiM mintte of a ptriod afte^ pravlioi ir ^ libimiy rate or tir tiio IJtaariiii In oinrso. HAW WMno'wui oum hatk Boimowco DATS DUB W 17 1924 IOC' 1 fllSW NEH COLUMBIA UNIVERSITY LIBRARIES 0041396812 J* I I