WOOD PATTERN-MAKING puKriELp Book Goipght]^"_ COPYRIGHT DEPOSIT. •■Si o Wood Pattern -Making The Fundamental Principles and Elementary Practice of the Art. To which is added an appendix on the Care and Use of Woodworking, (Bench) Tools. BY Horace Traiton Purfiki^d Instructor in Woodwork and Pattern Making, in the Department of Engineering OF THK University of Michigan PUBIvISHED BY THE AUTHOR 1906 THE SCHARF TAG, LABEL & BOX CO. YPSILANTI, MICH. ■^0 -p, n LIBRARY ntCGNGRESS Two Conies Received MAY 5 !906 ^ CoDyrifiiii Entry CLAS-v OC '«o. COP^r B, COPYRIGHT, 1906, BY HORACE TRAITON PURFIELD (q-'\(o1^0 PREFACE An experience of seventeen years in teaching pat- tern-making and kindered subjects has made me feel the great need of such a work as this which I now offer as a text -book for students in technical and manual training schools, and universities. A number of excellent books on the subject have been published, to be sure, but most of them assume on their reader's part previous acquaintance with the fundamental ideas of pattern -making; such as do treat at all of the elementary part of the subject, happen to be works of an exhaustive character, which are consequently too expensive for use as text -books. The present work, therefore, will, it is hoped, find a field of usefulness for itself. It is of course to be recognized that as pattern -mak- ing is an art, it cannot be learned simply by reading any book on the subject; but only by practice. Still a text- book may afford valuable assistance even to the artisan. This work, however, has a further and more important purpose, — that of imparting to the engineer or the drafts- man the fundamental principles of pattern -making. For only as he is In possession of these can he make designs for patterns in accordance with which shop work can be performed in the most efl&cient and most economical manner. The reader should also understand that this work, being designed only as an elementary treatise, in no way exhausts the subject. It is claimed however, that the examples of pattern -making submitted indicate, on the whole, the best methods of construction and those most easily understood by the student. VI PREFACE In preparing the body of this work, I have received many valuable suggestions which have been incorporated herewith, and which will have contributed to any success the book may attain. The works of many previous writers on the subject have been consulted also; for specific ideas derived from them credit should be given to Joshua Rose, M. E., J. McKim Chase, and P. S. Dingey. In preparing the appendix considerable help was afforded me by the little book of W. F. M. Goss, on "Bench Work in Wood." With these few words of introduction, I leave the book to its readers with the hope that it will assist them to master the important subject of which it treats. H. T. P. CONTENTS CHAP. PAGE Preface V List of Ili^ustrations VIII I. INTRPPUCTION 1 n. Molding .... 6. III. Generai, Principi.es 12: IV. Materials 20 V. Fillets .... 30 xVI. Cores . . ... i . • • 37 xVII. Moldkr's Joints or Partings 46 VIII. CpNSTRUCTIONAL JOINTS . 55 IX. Special Types of Patterns . . . 66 X. Plate Work and Irregular Parting . 83 XI. Pulley Patterns .... 93 XII. Patterns for Cast Gears 108 >^III. PiPE^ Fittings, . 126 XIV. Miscellane;ous . , . 132 Stove Pattern-Making , , 145 APPENDIX Reading Mechanical (Working) Drawings . . . 154 Lumber 161 Pattern Turning 199 ^LANES and Plane-Like Tools 188 Cutting Wedges . . , 195 Boring Tools 181 Saws . . . . Ill Index .212 UST OF IIvLUSTRATlONS FULL * 'Oliver" Combination Lathe —Frontispiece "Oliver" Bandsaw, 82 "Oliver" Handjointer, 36 "Oliver" Trimmers, 97. Bed of Trimmer, 98. "Crane" Core Box machine, 45. PAGE Wood Lathe with Compound Rest, 54. Universal Sander, 29. Universal Bench Saw, 65. Williamsport Scroll Saw, 65. "Rogers" Double Surfacer, 153 IN THE TEXT FIG. 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. Cylinder, with coreprints, 6 Holder's Flask, 7 To illustrate "draft," 14 Coefficients of shrinkage, 16 Screws in end wood, 28 Fillets sqr. corner, 31 Fillets round corner, 31 Pattern with square hole, 38 Mold made from No. 8, 38 Core and full box, 39 Different size core prints, 41 Taper core print system, 44 (a) Section of a mold, 47 Single flange wheel, 47 Double flange wheel, 48 Worm wheel, 48 Hook lever, 49 vSmall bracket, 50 Loose pieces skewered on ,50 Hollow cylindrical cast- ing, 51 Hollow cylindrical pat- ern, 51 Fig. 22. Hollow cylindrical core- box, 52 23. Built up disc, 56 24. Built up disc edge, 56 25. Thin board and counter ribs, 57 26. Open joints cylinder hd., 58 27. Open joints boxing up pat- ems, 58 28. Open joints up corner, 58 29. Lagged or staved up cyl- inder, 60 30. Lagged up cylinder narrow lags, 61 31. Lagged up core box, 61 32. Annular pattern, 62 33. Square frame (plate work), 63 34. Square frame (plate work), 35. Round corner, 64 36. Gland (the casting) , 67 36. (a) Gland leaving its own core, 69 ILLUSTRATIONS IX 2>7. Gland Pattern, 67 38. Gland core box, 71 39. Laying out core box, 71 40. Core box plane, 72 41. Core box plane with guide. 73 41. (a) Conical core box, 74 42. Chuck with pieces nailed on, 76 43. Cylinder with flange both ends, 77 , 44. Cylinder with flange both patterns, 17 45. Cylinder with flange (core box), 77 46. Pump standard (casting), 84 47. Punipstandard(pattern) , 86 48. Core prints for No. 47, 88 49. Core box for No. 47, 89 50. A, Turning bosses, 90 50. B, Hook lever drawing, 91 53. Pulley, 93 54. Shoot board, 96 55. Center of spider, 100 56. Three armed chuck, 109 56. A, Foim of gear rim, 110 57. Methods of forming gear teeth, 112 58. Box for laying out gear teeth, 113 59. Laying out No. 58, 113 60. Laying out tooth curves, 117 61. Bevel gear lay out, 121 62. Chuck, 122 63. Chuck, large, 123 64. Pipe bend, 126 65. Pipe bend, 127 66. Pipe bend, 127 67. Pipe bend, 128 68. Pipe bend, 128 69. Pipe bend, 128 70. Pipe bend, core box, 128 71. Pipe bend, core box, 131 72. Pipe elbow, 129 73. Pipe elbow ring, 129 74. Pipe elbow ends and prints, 130 75. Pipe elbow built together, 130 76. Pipe elbow core box, 131 77. Steam chest cover (cast- ing), 132 78. Steam chest cover pattern, 133 79. Skeleton pattern, 134 80. Skeleton pattern core, 134 81. Skeleton pattern, boiler plate form, 136 82. Gluing feather edge board, 137 83. Piston ring, 140 84. Piston ring pattern, 140 85. Drill press column, 141 86. Loose piece dovetailed on, 143 Fig. APPKNDIX Fl G. 1. Pattern-maker's bench, 167 1. (a)Pattern-maker's vise, 168 2. Bench hook, 168 3. Saw-horse, 169 4. Two-foot rule, 170 5. Framing square, 171 X ILLUSTRATIONS 6. Tr3' square, 171 7. Combination square, 172 8. Bevel, 172 9. Laying out angles with dividers, 173 10. Marking guage, 174 11. Mortise guage, 174 12. Tanged firmer chisel, 175 14. Socket firmer chisel, 175 15. Inside gouge, 176 16. Outside gouge, 176 17. Sweeps of guages, 177 18. Draw shave, 177 19. Handsaw, 178 20. Backsaw, 178 21. Keyhold saw, 178 22. Compass saw, 178 23. Ripsaw teeth, 180 24. Cross-cut teeth, 180 25. Auger bit, 182 26. Square hole auger, 182 26. (a) Countersink drill bit, 182 27. Syracuse drill bit, 183 28. Expansive bit, 183 29. Forstner bit, 183 30. Center bit, 183 31. Countersink, 184 32. Bit-brace, 185 ' ^l. (a) Screwdriver, 185 33. Miter box, 186 34. Handscrew, 187 35. Iron clamp, 187 36. Iron plane with single iron, 190 37. Iron plane with double iron, 191 38. Wood plane with double iron, 191 39. Jackplane, 192 40. Blockplane, 192 41. Rebate plane, 193 42. Plow plane, 193 43. Dado plane, 194 44. Spoke shave, 194 45. Spoke shave, round, 195 . 46. Grinding a cutting wedge, 197 47. Turning lathe, 200 48. Fork center, 201 49. Screw chuck, 202 50. Cup chuck, 203 51. Turner's gouge, 204 52. Turner's chisel, 204 53. Group of scrapers, 205 54. Core box plane, 195 55. Use of turning gouge, 206 . 56. Use of turning or skew chisel, 207 57. Use of turning chisel (two positions), 208 58. Scraping a cylinder, 209 59. Outside caliper, 210 60. Inside caliper, 210 CHAPTER I. INTRODUCTION A pattern may be defined as a model about which is to be formed a sand mold, in which a casting is to be made. It is usually of wood or metal, and often con- structed in several parts so as to facilitate removal from the mold. In the foundry and machinery business the word pattern is understood to mean any form or deviCC by the use of which a mold may be made. Pattern -making differs from all other wood-work in several ways. The product of the pattern shop becomes a part of the tools or working outfit of another workman, viz., the molder. The joiner, in making a door, makes it just the size required by the drawing or specifications; the cabinet- maker does the same when called upon to make a table or other piece of furniture; the carpenter also follows this same idea when building a bridge. In all these, the ultimate object is reached when the work is complete. It is not so, however, with the pattern-maker; his product is only one step in arriving at the desired end. that end being the production of one or more castings of some kind of metal. Allowances must be made in con- structing a pattern, that do not have to be considered in other wood -work; the principle of these allowances are for draft, shrinkage of the metal of the casting, and the machining of the casting where required. A pattern- 2 WOOD PATTERN MAKING maker must be a good wood -worker, and able to work wood to accurate dimensions, both on the bench and in the lathe, as pattern -making consists largely of fitting, joining, and making circular and other forms to correct size. This knowledge and ability are necessary to the pattern-maker, because a large majority of patterns are made of wood. The pattern-maker must also know something, and the more the better, of the practical work of the molder. This is necessary in order that he may be able to produce easily-molded patterns. He should possess a good practical knowledge of the properties of metals, as, for instance, the contraction or shrinkage that these undergo in passing from the molten to the solid state, the strength of cast metals, and also their relative rate of cooling. He should also thoroughly understand the principles of Orthographic projection, so that, if it becomes necessary, as is frequently the case, he can make full sized working drawings of the work in hand. The production of ordinary metal castings, such as those of iron or brass, involves three distinct operations. First, making the pattern; Second, from this pattern a mold is made in sand or some other substance that is refractory enough to withstand the action of melted metal; Third, the metal is melted and poured into this mold. Each of these operations require especial skill, and has given rise to a special trade, although the second and third, called respectively molding and founding, are often performed by the same person. These operations are sometimes so intricate, and admit of so much variety, that the above statements are only true in the main. Nevertheless, they hold good in gen- eral, and in a consideration of this subject the pattern- maker may be understood to be a wood -worker, the INTRODUCTION 3 molder as one that makes the molds, and the founder as the one that has charge of the furnace and the melting of metals. In the first of these operations, that of the pattern- maker, there is needed a fine degree of skill in the arts of cabinet making and wood turning. Moreover, the two trades, the molder's and pattern-maker's, are so intimately connected, that it is almost impossible to describe one without frequent reference to the other, and as a matter of fact there is almost as much to be learned of pattern -making in the foundry as in the pattern shop. So intimately connected are the operations of pattern - making and molding, that one of the chief qualifications of a good pattern-maker is the ability to form a rapid and reliable judgment as to the best way of molding a given pattern out of several ways possible. As there is usually more than one way of molding a given pattern, it is advisable that the pattern-maker, if in any doubt, confer with the molder as to his preference in the matter; as the molder is responsible for the production of the casting, he should have the pattern as he wants it. As pattern - making, therefore, is to be regarded primarily from the molder's standpoint, and not from that of the wood- worker, the following matters are of first importance: (l) Patterns being entirely enclosed in matrices of sand, provision must be made for pulling them out; this involves draught or taper, which is a thinning down of certain parts, division into sections, and provision for loosening by rapping. v2) Molding sand is always used damp, and pat- terns are subject to rough usage, consequently they must be made so as to resist any tendency to change their form and size from the absorption of moisture from 4 WOOD PATTERN MAKING the damp sand, and they must be strongly constructed. (3) Most metals shrink or contract in passing from the molten to the solid state; therefore, patterns must be made larger than the required casting to allow for this. (4) Patterns may be entire or complete, exactly like the castings wanted ; however, if there are cavities to be formed in the casting, these hollow places will be represented by core prints. Moreover, the part the pattern-maker has to do with getting out a given casting may be the preparation of a sectional part or parts of a pattern from which only a part of the mold is made; the other partis made with a sweep, the boards for which are also prepared by the pattern-maker. (5) The practice of pattern -making is largely gov- erned by the requirements of the engineer; these require- ments are that patterns must correspond to drawings in all dimensions, that all centers be correctly located, and that all necessary allowances be made both for machin- ing and for the shrinkage of the metal of the casting. It will thus be seen that the pattern-maker has very little in common with carpenters, or indeed, with any other wood -worker, except for the fact that he uses the same tools and processes. To understand, then, the fundamental principles of pattern-making, it is necessary to master the principles of molding, and much of its details as well ; and to have a good working knowledge of modern machine shop practice. It is well to remember also that mere outside polish or finish on a pattern does not count for much if such matters as correct construc- tion and others already spoken of, are neglected. In many trades, to become an expert in handling tools, is the most neceesary requirement, but this is not INTRODUCTION 5 the case in pattern -making, there being something far more important than cutting wood. In the construction of many patterns it is not so much a question of work- manship, as of knowledge. Certain patterns, for example, are very difficult to design, but after they are once made, they can be duplicated by any good wood -worker. In fact, it often requires but little skill to construct the necessary core boxes, etc., that may be required to produce certain castings. On the other hand, there is much pattern - making that calls for fine workmanship; in any event, pattern -making is not merely cutting wood. From what has been said, then, it will readily be appreciated that pattern -making is an important and responsible trade. For while the duty belongs to the draughtsman of preparing the design, yet the pattern- maker must be able so to interpret it as to get the idea the draughtsman intended to convey. Moreover, he must look forward to the requirements of the molder; consequently, from the drawing alone he must be able to imagine the completed casting, and build a pattern that will produce it. As the medium by which the designer's ideas are put into the tangible form of a casting, his, then, is a two-fold responsibility. Another fact that adds to his responsibility is, that there are so many different ways of molding. This gives a great field of study for the pattern-maker. The fact that there are so many dif- ferent ways of molding makes it advisable for the pattern- maker to consult the molder before making patterns for complicated work. CHAPTER II. MOLDING A pattern-maker should know something about the operations of the molder, so that he can make a particu- lar pattern of such a shape that it can be molded in the easiest way possible. This being the case, it is necessary to explain some of these operations. The form of pattern used in this illustration is what is known as a parted pattern; the molding operations that this form involves are generally few and simple. As will be seen by Fig. 1, the pattern is made in two parts, the parting or joint being along the axis of the cylinder. It is made in this way Fig. 1. for the convenience of the molder. These two parts are held sideways in relation to each other by what are called pattern pins, represented by dotted lines, c and d. Parts marked A and B are core prints, and will not appear on the casting. The appliance used by the molder in which to make the mold is called a flask, and is illustrated by Fig. 2. The upper part, A, is called the COpe, the lower part, B, MOI.DING 7 the nowcl; C is the bottom board, D, cope bars, E, guide pins. Each flask is composed of at least these three main parts, viz., cope, nowel, and bottom board. Sometimes another part is introduced between the nowel and cope, called the clieck, or middle part. This is necessary when the casting is of such shape that its pattern cannot be taken from the mold with the one parting obtained by the use of cope and nowel alone, that is with the simple form of flask shown by Fig. 2. In addition to these Fig. 2. parts a molding board is needed, which may be just like the bottom board. Only one molding board is required by one workman for any number of flasks of the same size. The words top and bottom will be frequently used in writing of this flask. They refer to the flask when standing in what may be called its normal position, that is, as it stands when the mold is ready for the melted metal to be poured in. The relative position of these two 8 WOOD PATTERN MAKING parts is that the cope is always on top, the nowel at the bottom. Each part is a box having neither top nor bot- tom, the sides generally being about 5 or 6 inches high, and rough inside. In order that, after being separated, these may be put together again in the same relative position, they are provided with guide pins (K) Fig. 2, the pins proper being on the cope, and the lugs into which they fit, being on the nowel. The cope is also provided with some form of handles. In Fig. 2, one of these is shown at E, being in this case a strip of wood about one inch square nailed across the end, directly above the guide pins. These handles are provided for the purpose of lifting the cope from the nowel at any time it becomes necessary to do so during the process of molding. There are also cross bars fastened across the cope (D Fig. 2) to assist in retaining the sand, which is held in place by friction only, the cope from necessity having no bottom. In all other respects cope and nowel are alike, except that in some cases one may be deeper than the other. In using this appliance the molder first places the molding board on the sand floor of the foundry in an approximately level position, and so it will not rock. He then places the half of the pattern that is without pins on its flat side in the center of the molding board. The nowel, or drag, which is the lower half of the flask, is next placed on this board, bottom side up, with the half pattern in the middle of it. Next he sifts -molding sand on to this board until the half pattern is covered to a depth of an inch or more ; he now shovels in sand until the nowel is filled and heaped up; then, with an implement called a rammer, he rams it down MOI.DING 9 solid. The sand is now struck off even with the bottom of the nowel, some loose sand thrown on, and the bottom board placed on and rubbed around so as to make a solid bed for the body of sand in the nowel. Clamps are now put on so as to hold all together, the whole is turned over, the clamps removed, and the molding board lifted off. This completes one half of the mold, or, as the molder expresses it, "the nowel has been rammed up and turned over." He now sleeks the surface with his trowel until it is even with the flat surface of the half pattern, which is thus exposed to view, surrounded by sand. He now scatters on some parting sand, which is a very dry sand, usually burnt sand that has been cleaned from castings already made. The purpose of this is to prevent the next body of sand from sticking. The other half of the pattern is now laid on, its position being determined by the pins already spoken of, and the cor- responding holes in the other half of the pattern. The sprue pin or stick is now set up on the sand or parting just finished. This pin is a piece of wood, whose shape is the frustrum of a cone about ten inches long; its pur- pose is to make a hole through the cope sand into which the melted metal may be poured. Sand is put into the cope in the same way as was done with the nowel ; struck off even with the top, the sprue pin pulled out, and the whole surface brushed over so as to remove all loose sand. The cope is lifted off carefully, aqd set to one side. Both halves of the mold now appear exactly alike, except that the cope has the sprue hole running through it. The two halves of the pattern must now be drawn or pulled out. This the molder proceeds to do in the following manner: If the pattern is provided with lift- 10 WOOD PATTKRN MAKING. ing plates, as all standard patterns should be, he intro- duces the end of the lifting screw into the hole provided for it in the lifting plate, and turns it in so that it is solid. If there are no lifting plates, he drives what he calls a draw spike into one of the halves. Then, with a mallet, a small hammer, or perhaps a sprue pin, he raps on all sides of the lifting screw or draw spike, so as to loosen the pattern. This operation, called rapping the pattern, enlarges the mold so that the pattern may be pulled or drawn out. This he now does, very slowly and care- fully, gently rapping the pattern until it is entirely free from the mold. This is done to both halves. A channel is now cut in the sand of the nowel from the spot on the parting where the sprue pin was set, to the mold or cavity left by removing the pattern. Thus is provided a passage through which the melted metal may run and fill the mold. This channel is called the gate. The mold is now ready to have the core set in. After the core is set, the cope is put back into its original or nor- mal position, which is determined by the guide pins; the whole is then clamped together, and set in position for pouring. As stated at the beginning, this process applies only to parted patterns. This same flask may be used in several different ways, the particular way being determined by the Shape and size of the pattern. For some shapes of patterns it is necessary to use three (3) boxes or partS; this is usually called a three-part flask, thereby meaning that the mold is composed of three dis- tinct bodies of sand. The central part of a three-part flask is called the cheek. The cheek has on it a set of guide pins the same as the cope, and also a set of lugs like those on the nowel, on the opposite edge. It is made in this way, so that any cope or nowel of the same size may be used with it. MOLDING 11 These simple explanations will be enough to give the student of pattern -making a general idea as to the use of patterns in the foundry. Of course there are many- details to be observed and carried out in the production of castings that are not mentioned above, but as these more particularly concern the molder than the pattern- maker, they will not be noticed here. CHAPTER III. GENERAL PRINCIPLES In building foundry patterns several ideas must be be kept in mind, either consciously or unconsciously. These are four in number, or (.when we have no source of information as to what is wanted, except a drawing of the required casting), there may be five, as follows: (1) What may be called the designer's idea; (2) the way in which the pattern is to be pulled from the sand ; (3) the draft, or taper,' which is a thinning down of cer- tain parts of the pattern in order to facilitate its removal from the mold or sand; (4) the SlirinRage of the metal of the proposed casting, while passing from the molten to the solid state; and (5) the machining or finishing of the casting after it is made or cast. An experienced pattern -maker may not be conscious that he has in mind any one of these ideas, because he uses them so frequently that he does so without thinking especially of them; in other words, they become second nature to him. It is these last four ideas, among others, that separates this trade from all other wood -working trades and connect it with the engineering profession, for there is not one of them that has even to be thought of by those working at any other of the wood -working trades. Before we explain these ideas in detail, it will be best to have them arranged before the mind in such a wav that GENKRAL PRINCIPLES 13 they may be easily remembered, and in the order of their use and importance. For convenience, then, we will put them in a vertical column, thus: 1. Designer's idea. 2. Way to be drawn from mold. 3. Draft. 4. Slirinkage of metal. 5. Macliining. Besides these five ideas, the last three of which may be called allowances, there are two other allowances that sometimes have to be considered, viz. : for shake and for warp. The two first of these five are purely abstract ideas. If it is desired to make a pattern from a drawing only, that is, if there is no other means of knowing what is wanted, then it will be necessary for the one building it to form as nearly as possible the same mental picture that the designer had in mind when making the drawing. This may be called the designer's idea, md to some extent, at least, must be realized before much can be done towards building a pattern. After having thus formed in mind the general shape and approximate size of the required pattern, it can be decided in which way it shall be drawn from the mold. This must be decided before very much can be done towards building the pat- tern, so that the draft may be made in the right direc- tion, which is a very important matter. The other three points that were mentioned are sometimes spoken of as the allowances to be made in pattern -making. They are really additions made to the size of the pattern in some one direction, or, as in the case of shrinkage, in all directions. The first of these, and in some respects the most important, is what 14 WOOD PATTERN MAKING is technically called draft. This is a thinning down of certain parts of the pattern; that is, the vertical sides of the pattern are tapered, and it is sometimes spoken of as the taper. The amount of draft to be allowed is governed by the case in hand, some patterns requiring more than others. The usual amount is 1-8 inch for 1 ft. in height; this is generally enough for small and compara- tively plain work, but for complicated work it is not enough. No hard and fast rule, however, can be given for this allowance, or indeed for any work in pattern - making. What is nearest to a general rule may be Fig stated thus : Give the pattern as much draft up to 1-4 Inch per foot in height as will not Interfere with the design. Whatever amount is allowed should be added to the size of the casting as given in the drawing. For small and plain work one -sixteenth of an inch will be enough, but if the pattern is at all complicated, one -quarter of an inch will not be too much. Of course, the requirements of the molder have to be considered, and if he was asked about it he would always say, give it the larger amount. To make this more plain, we will suppose that a pattern was wanted from which to make a mold for the casting rep- resented by Fig. 3. GENERAL PRINCIPLES 15 Now applying the above principle, we should make the top longer and wider by % inch than the size given, so that the top of the pattern would be S}i inches long and 6% inches wide. This addition, or allowance is shown by the dotted lines. In this case the pattern would be drawn out of the mold in the direction of the arrow. In practice it would not be necessary to allow so much draft on as plain a pattern as this, but we use it as an illustration of what is meant by the term draft. All vertical sides of the pattern, whatever its shape, must have some taper in order that the molder may get it out of the mold without breaking the mold. If no draft is allowed, the molder has to rap the pattern so much that the mold will be distorted and the casting will not be like the pattern. The next important principle to be observed, especi- ally when the casting is required to be exact in size, is that relating to Shrinkage. Whenever this word is used in connection with pattern making, it always means the shrinkage or contraction of the metal of which the cast- ing is made. An iron, brass, or steel casting is always smaller than the mold in which it was made, and this is true also of castings made of any of the other metals in common use. This is due to the shrinkage of the metal when cooling. The amount of the shrinkage varies in the different metals, and also in the same metal under varying conditions. Brass will shrink more than iron, and iron that is very hot when it is poured into the mold, will shrink more than iron that is comparatively cool when poured. The size and the shape of the casting also have much to do with the amount of shrinkage. An iron that will shrink one-eighth of an inch to the foot in light work, will shrink only one-tenth of an inch, or less. 16 WOOD PATTERN MAKING in large work. For instance, in casting large box or cylindrical -shaped castings, one-tenth of an inch per foot is usually enough to allow for this shrinkage in the diameter, but one-eighth ot an inch will not be too much in the length. The reason for this difference is due to the fact that the castings are practically unrestrained in their length, and are comparatively free to shrink in this direction, while in the diameter they are restricted by the cores and internal parts of the mold. The amount of allowance usually made in common practice is 1-8 inch per foot, measured in all directions. But since the coefficient of shrinkage is different for different metals, this is only approximate. The following allowances for the different metals are made in the pattern when it is surely known just what metal the casting is to be made of, as, of course, is the case usually. One good way to remember these is to arrange the figures that represent these amounts in a group like Fig. 4. Fig. 4. then, this allowance is 1/ i,< '/lO inch ; for I/' For iron, brass, Wie inch; aluminum, }{ inch, and for steel, 74 inch; the general amount, which is in the center of the group, is /8 inch. It must not be understood by this that these metals will always, and under all conditions. GENERAL PRINCIPLES 17 shrink just these amounts; for, as has already been men- tioned in the case of iron, the amount of shrinkage varies somewhat under varying" conditions. For the use of pattern-makers, scales or rules are made. The one most commonly used provides for an allowance of }i inch per foot; that is, the rule is made ^8 inch longer than the standard foot rule, and each "inch" is cor- respondingly longer on it than the standard inch. Scales or rules can be bought at dealers, graduated for the other shrinkages above spoken of. It has been a mooted question as to just when this shrinkage or contraction takes place in the casting, but it is generally conceded now that it takes place in passing from the plastic condition to the solid state. All metals, in passing from the liquid to the solid state, suffer expansion when in the plastic condition. It is this feature in the transition that enables metals to take and retain the impressions of the molds with such fidelity. Allowance for shrinkage is not regarded on patterns that are Six inches or leSS in area, as the rapping of the pattern will usually make up for any shrinkage that may take place. Patterns that are four inches or ICSS in size, are made slightly smaller than the desired size of the cast- ing. This is called an allowance for shake. It is not regarded unless it is necessary that the casting be exact in size. Patterns between six and four inches may be made without regarding either shrink or shake. In building machinery it is often necessary to fit two castings together. Wherever this is done, the two sur- faces that come into direct contact are usually machined in someway in order to obtain a smooth, clean surface of metal. A part of a pattern that represents a surface of this kind on the casting, must be made larger. This is 18 WOOD PATTERN MAKING the case, whether the two surfaces are to slide or rotate on each other, or whether one is simply bolted to the other. It is called an allowance for machining or finish. The amount of this allowance is generally /i inch, measured perpendicular to the surface to be machined or finished. If the surface is simply to be machined to fit another sur- face, and the work is comparatively small, this will be enough. But if it is required to have a very nice finish, free from all sand holes, or if the work is large, it might not be enough ; in some cases it might be necessary to make it twice the amount, or }{ inch on each surface. Moreover, as the casting increases in size, its irregulari- ties also increase, so that a larger amount must be allowed. In the case of large work, such as engine beds, the allowance is frequently made from % to 1 inch. A large allowance is especially necessary on very irregular and new work, as the amount of distortion caused by the strains set up in the casting by shrinkage is very uncertain. I^arge steel castings are usually very rough, and also become more or less distorted in cooling and anneal- ing, so that it is necessary to allow more on this account. Of course, the exact amount must be determined by the circumstances of any given casting, but there should be enough so that in taking the first cut, the tool used may get beneath the sandy scale that is always present on a casting, and still leave enough for a second cut at least, and a third or finishing cut if necessary. It, therefore, cannot be much less than one-eighth of an inch. There is one other allowance to be mentioned that is not usually called for in making machinery patterns, but is frequently in making what are called architectural patterns. Some castings, because of their varying thick- ness, or because of one surface being more exposed than GENKRAI. PRINCIPI.es 19 another, therefore cool more rapidly, warp or become distorted in the mold when cooling. To overcome this, patterns for castings of shapes that are known thus to warp, are made of such a shape that in cooling they will assume the desired shape. This change in shape of patterns is called an allowance for "warp." CHAPTER IV. MATERIALS Wood is the material used for a large majority of patterns. At first thought it would seem that wood is a particularly unsuitable material to be used in matrices of damp sand, and to be subject to such rough usage as the ramming and rapping of a pattern necessarily involves, but there are several reasons why wood is used. The first that may be mentioned is that it is easily worked and altered. Secondly, it is light and portable. Further- more, by exercising due care in construction, its dis- advantages may in a degree be overcome. The pattern- maker, of course, meets with the same difficulties with which other wood -workers have to contend, and as inter- fere with the durability of patterns. The chief one among these is due to the tendency of wood to shrink and swell, which cause warping and change in form and size. This cannot be wholly overcome, but by arranging the different pieces in a given pattern with a due regard for this natural tendency, it may to a degree be counter- acted. To prevent warping it is necessary to know the effect this tendency has upon the individual board ; and this may be determined, if the position of the board in the log is known, which may be determined by examin- ing the end. If a board is cut from the middle of, and directly through the diameter of the log, it is not very MATERIALS 21 likely to warp; but if a board is cut from a position mid- way between the heart and the outside of the log, it is sure to do so, for it will assume a curved outline between the edges, the heart side always becoming convex. This is caused by the more rapid drying of the board on the sap side. For as the board is cut through the concentric cylindrical layers of which the log is composed, the outer side of the board contains more exposed fibre ends and more open pores than the heart side. Consequently, the sap side of a board gives off the moisture it contains more rapidly, and it will also absorb moisture more rapidly. In view of this fact, the sap side of any board should be placed where it will be the least likely to be exposed to any change in atmospheric conditions. That is, whenever it is possible, this side of the board should be always placed on the inside of any pattern work. What is known as quartcr-sawn lumber is the best for pattern -work and all wood-work, because it is not so likely to warp as is the regular, or bastard -sawn. Quarter-sawn lumber is lumber that is sawn approxi- mately parallel with the medullary ray. The trunk of a tree is made up of concentric cylindrical layers, bound together with radial fibres, which are known as medul- lary rays. It is the exposure of these rays that gives to quartered oak the beauty that is so much prized. How- ever, quartering is a very wasteful way of sawing lumber, and involves an extra cost. But for pattern work that must be made thin, it pays to use quarter-sawn lumber, even if it does cost more. Another very important factor in connection with lumber for patterns is, that it should be thoroughly seasoned before being used, if possible, by what is known as the natural or air seasoning process. The seasoning 22 WOOD PATTERN MAKING should continue for at least tWO years, in order that the natural gums of the wood may be fixed ; that the rapid drying of the kiln will not drive them out and in that way make the wood more porous. Lumber intended for pattern work, if allowed to remain in a shed with a waterproof roof for two years, will give better results than lumber exposed to all sorts of weather for six months, and then placed in a dry kiln to finish the pro- cess. For one-inch lumber two years is enough; thick- er planks will, of course, need more time, say four years for two- inch. However, lumber cannot be so thoroughly seasoned as to give entire permanence of form and durability to patterns made from it. Besides being thoroughly seasoned, lumber for patterns should be Straight, and evcn in grain, not too hard to be easily worked, yet not so soft as to be unduly injured by the rough usage patterns must necessarily undergo in the foundry. There is no wood that fulfills these conditions better than what is known as White Pine (Pinus Strobus), sometimes called "cork pine" because of the cork-like appearance of the bark. This wood, when thoroughly seasoned, will retain its shape very admirably under the excessive atmospheric changes that patterns have to undergo from pattern-shop to foundry, and from foun- dry to the storage loft. When first cost need not be considered, and it should not be in the case of small standard patterns. Mahogany, what is known in the market as Honduras M., is the best wood for all patterns; it is very even and straight in the grain, not so hard but that it can be easily worked, and retains its form and size to a remarkable degree. One thing to be men- tioned in this connection is the arranging or MATKRIAI.S 23 combining the several pieces of which a pattern is made in such a way that any shrinking or swelling of the wood shall not change the shape or size of the pattern. This is an important matter in some classes of work, and should have the careful consideration of the pattern- maker, especially in the case of standard patterns. If this is done it will add considerably to the durability of a pattern. There is one principle it is well to observe in combin- ing the several pieces of wood in a pattern, and that is to have as near as possible the grain of the wood run in the same general direction, so that as it shrinks or swells it will do so in the same direction, and there- fore will not distort the pattern. Special patterns are often made of braSS, iron, whitC metal or alumnium. These metals would be used in light or curved work, and also when a large number of cast- ings of the same size and shape are wanted. With few exceptions, however, original patterns are made of wood. Statuary and other ornamental work is usually modeled in wax or clay, which serves as the pattern. When it is proposed to use a metal pattern for the production of castings, the original pattern is made of wood and is called a master pattern or double -ShrinRage pattern. This is made with a double -ShrinKage allowance, so that a casting made from it will still be large enough for the pattern from which to make the castings wanted. Patterns made of wood must be varnished or they will soon go to pieces. SANDPAPER In pattern work sandpaper should be used with dis- cretion. The pattern should be formed as nearly to shape and size and finished as accurately as possible with the 24 WOOD PATTERN MAKING cutting tools before sandpaper is used. Under no cir- cumstances should sandpaper be used for cutting down or removing any considerable amount of stock, or for doing anything that can be done with tools. Otherwise the draft and the accuracy may be impaired. Sandpaper, as its name implies, is made of sharp sand (Quartz or Garnet) glued on paper. It is graded according to the grains of sand, and numbered accordingly. The grades most useful to the pattern-maker are Nos. 0-2. No. ij is best for use directly on the wood, and No. 1 for the varnished surface. Ordinarily, sandpaper should be rubbed across the grain of the wood. In the last two or three years, what are called pattern -grinding or sanding machines have been introduced to the trade to take the place, in some kinds of work, of sandpapering by hand, and they accomplish the work much better and more rapidly. Any kind of abrasive that can be fastened to the machine may be used. GLUE In pattern -making as in most of the wood -working trades, glue is depended on for adhesive fastening. For fastening leather fillets, shellac varnish is sometimes used. Since much depends on the character of the glue used, it should be of the best. There are many kinds and qualities of glue on the market, including liquid, pulverized or ground, and sheet. The liquid glue is always ready for use and is very good for small work. The sheet or flake form, ground, dissolved and applied hot is the best for general use. Animal glue comes in thin sheets; it is the best, and likewise the most expen- sive. Of late years the large manufacturers of glue have taken up the practice of grinding these sheets, which MATERIALS 25 makes it much handier for use. However, this enables dishonest dealers to g:rind the cheaper kinds of glue and pass them off as the best, for when ground it requires an expert to tell the difference, but when it is cooked, the odor given off will generally indicate its quality. As a rule, the best quality of glue is of an amber color, and the sheets rather thin. Whichever kind (excepting of course the liquid) is used, it should be soaked in cold water for a short time before cooking; only a small quan- tity should be prepared unless the shop is provided with a steam glue heater that is kept hot. Glue is much stronger if used while fresh, as frequent heating and cooling destroys its strength. To obtain the best and strongest joint, the wood should be slightly warmed too, say from 90 to 120 degrees, and the glue applied as hot as possible, and the work quickly clamped. As a rule, the harder the glue the better it will resist moisture. When it is necessary to glue two pieces of wood together so that the joint is on the end grain, the end should first be given a coat of thin glue, which should be allowed to dry before applying the glue for the joint. This is called sizing the joint. Plenty of time should be given the joint to dry — ten to twelve hours, according to the size of the work, will usually be enough if in a warm and dry shop or room. To much care cannot be exercised in the use of glue for pattern work, indeed it is not advisable to use it at all when nails or screws will answer the purpose. But there are some kinds of patterns that cannot be made without it. VARNISH All wooden patterns should be covered with some kind of protective coating so as to prevent as much as possible the absorption of moisture from the damp sand 26 WOOD PATTERN MAKING of the mold, for this is very injurious to all wood work. The protective coating should be of such a nature as to be unaffected by RlOisturC and also to insurc a hard, SmOOth surface that will "draw" easily from the mold. In practice there are two general classes of varnishes, Shellac and Copal. The first, which is the kind most generally employed, is composed of common Gum Shel- lac cut with alcohol and colored, if so wanted, with some kind of coloring ingredient. The second comprises the better grades of Copal varnishes used by finishers. This may also be colored. By changing the color of the var- nish employed, it is possible to distinguish between core prints and the body of the pattern, and also between patterns for castings of different metals, such as brass, iron and steel. For shellac varnish a good grade of gum should be used as the cheaper grades will not stand up to the work. This is usually called ycllOW varnish. BlacK varnish is made by adding lampblack; a good quality of lampblack should be use, one that is free from grit. Red varnish is made by adding some red powder, usually Indian red, or Vermillion (Chinese is best) to the yellow varnish. The use of these in varnish seems to give it a better body and greater durability. Copal varnish, how- ever, is still more durable, and if time (about three days) can be given it to dry, it is much the better and will out- last several coats of shellac varnish. BKKSWAX Beeswax is used for making small fillets, and filling small holes, such as nail holes, etc., and any other slight defect in either material or workmanship. It may also be employed for making a slight change in the form of MATERIAI^S 27 a pattern that is not much used. It is not good practice, however, to use it in this way on standard patterns, as it is very liable to melt and run out in the storage loft during warm weather. Wax is sometimes used for coating iron patterns to prevent them from rusting. To cover iron patterns with wax, they should first be made as warm as they can be handled, then the wax should be spread on them as evenly as possible and brushed over with a soft brush. NAII,S For pattern work, what are known as "wire brads" are the best nails. They can be driven almost anywhere in the wood without splitting it. They may be had of all lengths from one-half inch to three inches and of different sizes of wire. However, owing to the necessity of rapping patterns when drawing them from the mold, it is always best to use screws when fastening the differ- ent parts of a pattern together. They are much better than nails on account of the clamping effect they give to the pieces to be joined. This is a very desirable effect in the case of standard patterns. Another reason why screws are much better than nails for this purpose is that when it is necessary to change or repair a pattern, screws can be taken out without tearing the wood of the pattern, and if needed, can be replaced exactly in the same place. Screws are also handy for temporarily securing loose parts of a pattern, and for this use are much superior to nails or pins, When screws are to be used for fastening two pieces of wood together, holes as near the size of shank of screw as possible should be bored through the upper piece. If this is not done the screw will cut a thread in both pieces thus hindering the clamping effect 28 WOOD PATTERN MAKING that is Otherwise obtained by the use of screws for this purpose. As is well known to most wood -workers, end grain wood, especially soft wood, does not hold a screw very securely, unless some special method is used. One of the best ways of putting screws into end grain is to bore a hole of a size as near as can be to the size of the solid part of the screw. The thread of the screw will then cut its way into the wood without disturbing the fiber and thus the full shearing strength of the wood will serve to hold the strain put upon the screw. The hold of a screw in end wood may be increased by taking it out, placing a small amount of glue in the hole, and putting the screw back in at once while the glue is soft. It is Fig. 5. sometimes necessary to take out and reinsert screws in end wood, repeatedly, — for instance, when pattern work has to be taken apart for convenience in molding. In such cases, simply screwing them into the end wood should not be depended upon, as they get loose and do not hold. A good way to overcome this difficulty is illustrated by Fig. 5. It is to bore a hole at right angles to the direction of the screw in such a position that the screw shall pass through it; fill this hole with a hardwood MATERIAI.S 29 plug, bore a hole of suitable size for the screw and insert the screw. If now the screw from frequent taking out and screwing in becomes loose, the plug may be taken out and another put in its place. As noted elsewhere, screws make a much stronger fastening than nails and should always be employed in pattern work that is to be much used, as in the case of a standard pattern. Clement Universal Sander CHAPTER V. FILLETS Sharp corners on a casting, whether inside or out- side, generally detract greatly from its appearance, and also, in the case of internal angles especially, injure its strength. This being the case, sharp corners must be avoided in the pattern, as the casting will be of the same shape as the pattern. The weakness due to sharp cor- ners, especially in the case of internal angles, is caused by the way iron acts in cooling, or in passing from the Fig. 6. Fig. 7. molten to the solid state. There are always more or less strains set up in a casting by the shrinkage or contrac- tion that takes place at that time. As the iron hardens the crystals seem to arrange themselves in such a man- er that their lines of strength are perpendicular to the FII,I,KTS 31 faces of the casting. For instance, in a casting of the general shape shown by Fig. 6, these lines arrange them- selves as shown by the short lines drawn perpendicular to each face and thus leave the space (a) open or honey- combed, consequently the casting will be very weak through the line (be), and when a strain is put upon it, it will be likely to break. In some shapes of castings these strains caused by shrinkage will of themselves crack the casting at this point and at all similar sharp internal angles. If the above casting is made with a fillet or rounded -in angle, this is not so likely to be the case, and if it is made as represented by Fig. 5 it will be just as strong at that point as at any other. For, as will be noticed, there is no place for this irregular crystalli- zation to take place. In view of these well-known facts, all internal angles should be thus rounded in or "filleted" on the pattern. There is another advantage gained in thus rounding in these internal angles that is appreciated by the molder. In molding a pattern of the general shape of Fig. 7(a), that for some reason has to be pulled or drawn from the mold in the direction of the arrow, a very sharp corner of sand 32 WOOD PATTERN MAKING will be left at the point (c). As the pattern is pulled up by it, a slight movement of the pattern sidewise would break it; then as soon as the pattern became clear of the mold, the sand would fall down into it, thus making what the molder would call a dirty mold. It would cause him some trouble to remove this sand from the mold, and it must be all cleaned out, for otherwise it would surely make a poor spot on the casting and might render it unfit for the use to which it was intended to be put. Therefore, for the molder's benefit as well as to strengthen the casting, it is best to round in any internal angles. Fillets may be made of wood, wax or leather. The last is undoubtedly the best; it also is the most expensive, at least in its first cost. Wood is generally used for straight work, the best practice being to fit and glue a piece of wood of the right size into the angle and allow it to dry before cutting the required curve. By work- ing the curve after it is glued in place, the tendency of thin edges of wood to curl when made wet, which of course is done in the glueing, is entirely overcome. There is no objection to using wood for this purpose if the wood that is used is straight in grain, and if the grain of the wood of which the fillet is made lies in the same direc- tion as the grain of the wood composing the part of the pattern to which it is glued. Leather is the best material of which to make fillets, since it is elastic enough to come and go with the wood as it shrinks and swells. It is as permanent as the pattern itself, gives a very smooth finish, and is easily applied. Wax is not very good except for very small fillets or for temporary patterns. It should not be used for fillets on standard pattern work as it is likely to melt and run out when exposed to summer heat in the storage loft. FILIvKTS 33 In making and applying fillets of wood, the process is something like this : First, a piece of wood of the proper length is ripped out square, so that each side is equal to the radius of the curve of the proposed fillet. One corner is fitted to the angle proposed to be filleted ; it is better if this does not exactly fit clear into the angle, that is, the fillet piece may be a little loose at the apex of the angle but should fit tightly on the other two sides of the triangle. When this is properly fitted the remain- ing or outside angle may be planed off with the jack plane so as to make a triangular- shaped piece. The third side, the one last made, is a good place in which to drive brads for holding the piece in place while the glue is drying. The brads should be placed about four inches apart. When a sufficient number of brads have been started, the glue may be applied to the piece, the piece set into the angle and the brads driven in as far as Fig. 6 (a) can be, while still leaving the heads protruding, so that they may be pulled out when the glue is dry. When the glue is thoroughly dry the nails may be pulled out, and 34 WOOD PATTERN MAKING the required curve cut or worked with gouge and sand- paper, making it as nearly tangent as possible to the two sides it connects. This work is illustrated by Fig. 6 (a). In order to apply leather fillets successfully, a tool known as a "filleting tool" is needed. It consists of a sphere of iron, or, still better, of brass, fastened to a short rod somewhat smaller than the sphere. The diameter of the sphere should be equal to that of the fillet. After the leather fillet is cut to the required length, moderately thick, clean glue, not too hot, is applied; the leather is placed in the angle, and the fillet- ing tool is run along the angle, pressing the leather firmly into place. The pressing should be done heavily enough to squeeze out all surplus glue, which should be cleaned off at OnCC with a piece of cloth or waste dampened with hot water; then the surface thus made wet should be wiped as dry as possible with a dry piece of the same material. The filleting tool should be quite warm for this operation. Wax fillets are put in in the following man- ner: Some wax is softened by heat and rolled into a omall cylinder, the diameter of which is governed by the size of the fillet. It is then laid in the angle. The fillet- ing tool before mentioned is warmed enough to soften the wax, and the cylinder is pressed into the angle. The wax, being softened, conforms to the shape of the tool, which, as it is passed along, leaves a circular surface tangent to the two sides of the angle The surplus wax should be cleaned off up to the line made by the tool. This makes a very nice job, and is a good way of making fillets for patterns that are not to be much used. There are on the market small presses that turn out cylinders of wax for making wax fillets. They are so arrange FILI.ETS 35 that different sizes of cylinders are made for different sizes of fillets. These small cylinders of wax are also used for venting cores and molds. These machines save considerable time and trouble in this kind of work, and also do it more satisfactorily. CHAPTER VI. CORKS. When castings with holes through them, or with internal cavities, are to be made, a pro- jecting body of sand must either be made in the mold at the same time as the rest of the mold, or else be introduced into the mold after the pattern is removed or pulled out. These projecting bodies of sand are called cores. When the pattern can be withdrawn from the mold Fig. 8. Fig. 9. and leave a core, or cores, as a part of the mold, it is said to leave its own core or cores. This is illustrated by Figs. 8 and 9. Fig. 8 represents a pattern that has been molded and removed from the mold; (Fig. 9) leaving core (a) projecting above the lower surface of the mold. When the cope is closed^'the'^'cope sand will, of course, 38 WOOD PATTERN MAKING touch the upper surface of these cores ; when the mold is filled with melted metal, it cannot get where these cores are. The result is that the casting will have a hole through it the shape of the core (a). Where pat- terns cannot be so made and molded with the ordinary appliances of the foundry to form their own cores, there is added to the pattern an attachment or projection that forms a mold in the sand, into which a separate core may be placed. These attachments are called COrc prints. These cores that are made separate from the mold are usually what are called dry Sand cores, although ^rcen sand cores are sometimes made in the same way. A simple form of pattern for a mold with a dry sand core, is represented by Fig. 1, parts A and B being core prints. A dry sand core is made in a separate device called a COFC boX. In the case of a symmetrical core, a core box is made only for a small portion of it. For a cylindrical core only a half box need be made; two cores from such a box be pasted together, thus form- ing a complete core. This same principle may be used in the case of very large work. A symmetrical mold, like one for a fly wheel, may be built up almost entirely with cores. Core boxes require as great care in their manufac- ture as patterns, and as much thought must be given to their shape, durability and finish. The shape of a pattern is nearly like the required casting; but the inside of the core box, which is, of course, the necessary part, is just the reverse, resembling more nearly the shape of the mold. When cores are made in boxes and inserted in the mold, it is necessary that they be supported in such a way that there will be no chance for a change of position CORES 39 during the time the mold is being filled with the molten metal. To give this support, special recesses are made in the mold to receive them. These recesses are made by the core prints previously mentioned. The core should exactly fill the recesses left by the core prints, and this part of the core should be large enough to support the core properly in place, so that the sand of the mold will not be crushed out of shape by the weight of the core, nor by the action of the metal while being poured into the mold. Core prints should be given more taper than the pattern itself, so that the work of withdrawing the pattern from the mold may not be unduly increased by their presence, and also so that the core may be the more easily adjusted to its proper position. In the case of plain cylindrical cores, whose length does not exceec" Fig. 10. five times their diameter, or of such as may be stood on end while drying, a full box may be constructed and the cores made whole. This, of course, saves the time of the core-maker, as he does not have to cement the two halves together. A core made in this way, with its box, or mold, is represented by Fig. 10. In making these core boxes and core prints, care should be taken that the 40 WOOD PATTERN MAKING part of the box corresponding to the print on the pattern should be exactly the same size and shape as that print, so that when the core is set into the mold it shall exactly fit. All core prints should be of ample size, so that their impression will hold the cores in their place, and so that the weight of the core and the weight and action of the melted metal will not change the position of them. It is well to remember that the material that must do this holding is only loam, or, as it is technically called, "sand. ' ' It therefore requires a comparatively large sur- face to make them secure against the weight and action of melted metal during the process of pouring it into the mold. On account of the varying shapes and conditions there can be no exact rule given for the sizes of these prints, that will cover all cases. The length of the core prints for a plain cylindrical horizontal core should approximate its diameter, and its shape should be that of a cylinder. For a VCrtlcal core of this same general shape, the print should be the frUStrum Of a COnC, with the large end next the pattern; the height should be Onc inch, and the diameter of the small end onc-half inch ICSS than the large end. In core work that requires prints of other shapes than those mentioned above, that is, where the opening into or through the casting is not round, then the prints should correspond in shape. The making of core prints properly located and of correct size and shape is a very important part of the pattern-maker's art, especially so from the molder's standpoint. Prints that do not show the exact position of the core may be very misleading and may result in the loss of the casting. One form of core where this mistake might easily be made and not be noticed until the cast- CORES 41 ing: was formed is illustrated by Fig. 11. The figure represents a casting that requires a cylindrical horizontal core with a part enlarged to make the cavity (A) which, it will be noticed, is not in the center of the length of the casting. In this case if both core prints are made of the same size, the molder will be quite likely to set the core wrong end to. The molder would not be altogether to blame for this mistake as he generally does not have anything to guide him in this work except the pattern and core box furnished by the pattern-maker. I Fig. 11. But if one core- print is made larger than the other, then it will be impossible for him to set it incorrectly without deliberately cutting the mold. In all core work, there- fore, the prints should be of such size and shape that it will be impossible to set the core into the mold in any other than the correct way. As mentioned above, one method is, as shown in Fig. 11, to make one print larger than the other or of a different shape. For cylindrical 42 WOOD PATTERN MAKING cores, the first is of course the best, and is sure to accom- plish the desired result. Sometimes it is required that a cylindrical core should lie in the mold in a certain position with regard to its circumference. In that case it would be necessary to change the shape of at least one of the prints, making one or both square so that the core cannot be set wrong or revolve after being set. Some prints for horizontal cores are not made long enough, consequently the metal when poured into the mold will, by its own static pressure, raise or displace the core and make the casting thinner on the cope side because of this movement. It is advisable to make the prints of cylindrical hor- izontal cores about equal in length to the diameter of the core. This may seem excessive and in some cases it may be, but it had better be too long than too short. When it becomes necessary to make them shorter than this on account of the size of the flask to be used, or of the core oven, and the casting is quite heavy, it is good practice to imbed a plate of iron in the mold for the core to rest on, thus the weight of the core will be distributed over a larger area of sand than the core -print alone would afford. A great many castings are lost because the lower print of vertical cores are made nearly parallel or with the ordinary pattern draft. The probable cause of this is that the core does not go down to the bottom of the mold since the sand is cut down by the core on setting. So when the cope is closed, being too long, it breaks the mold around the print of the core, allowing metal to flow into the vent and thereby causing the casting to **blow." This may be overcome to a large degree by tapering the lower print as is usually done in the case of the upper CORKS 43 one. If this is attended to there can be no trouble in setting the core. Indeed, in the case of small cores, the molder can set them enough faster to pay for the extra work of pasting such cores together. As this is the main objection to this shape of print, viz., the necessity of making the cores in halves, it will be more than overbal- anced by the advantage of the greater facility and rapid- ity with which the cores can be set, to say nothing about the larger output of SOUnd castings. The subject of taper core -prints for vertical cores is one of considerable importance, especially from the molder's standpoint. It is well to adopt some standard taper, so that if a core-print is lost, another may be made of the correct size whether the core box is in sight or not. Probably the best taper for the purpose is one of one- fourth inch to one inch in height. This is an easily remembered taper and will give entire satisfaction to the molder. This taper can be employed for all vertical prints large or small, (the smaller sizes being reduced in length) one inch is long enough for any size of cylin- drical vertical core. A good rule to follow for cores less than one inch in diameter is to make the length of the print equal to the diameter, while preserving the same taper. It might be objected that one inch is too short for large cores, say of 12 inches or more in diameter. But there is not much strain on the print, that is on the print in the sand of the mold which holds the core in place, — for it simply locates the core. Nearly all the strain, if, to be sure, there is any, comes on the end of the core. Therefore, any extra length given the print would be of no advantage, and one inch is as good as a greater length. One reason why there is but a slight strain on the sides of these prints is that the metal on 44 WOOD PATTERN MAKING being poured into the mold completely surrounds the core so that the pressure is practically equal in all direc- tions. This, however, is not the case with the horizon- tal cylindrical core. As has been already mentioned a taper of one -fourth inch on each side is the best. This is illustrated in Fig. 12, where it is reduced to a system. In this system, for cores that are less than one inch in diameter, the dimensions of the print are derived from ^^ ^ Ut^ Fig. 12 the diameter of the core; for instance, if it is required to provide for a core that is seven -eighths inch in diameter, the length of the prints will be seven -eighths inch, or the diameter of the core, the large diameter also, seven - eighths inch, the small diameter seven -sixteenths inch or one -half the large. Therefore, in using this system, all that we need to know is the diameter of the core, and this will give the other dimensions. Now if a print is lost, as often happens, another can be made without seeing the core box, if this system is carried out for all cores of this kind. 9 9 9 to o ^ :;JW CHAPTER VII. holders' joints or partings. The jointing of patterns is fundamental, and must be considered from two points of view; that of the molder, and that of the wood -worker. The first is concerned more particularly with the removal of the pattern from the mold, or, as the molder expresses it, pulling the pat- tern. The second is constructional, and into it enters the combination and arrangement of the different pieces of wood composing the pattern. The joints that are arranged for the purpose of removing the pattern from the mold are usually called partings, or pattem-maRcrS* partings, and strictly speaking, are not joints. The joints made in the construction of the pattern are true joints, and should be made as nearly perfect as possible, since the strength and durability of the pattern depends largely on their efficiency as joints. The first mentioned of these joints, the molder's part- ings, will be considered in this chapter. Whether a pattern is made correctly or not, from the molder's standpoint, will depend largely on the understanding that the pattern-maker has of these partings, and of their position in the mold itself. In order to explain these points a few examples will be mentioned. It requires at least one of these molder's partings for every pattern, as the mold must consist of two bodies of sand, MOI.DKRS' JOINTS OR PARTINGS 47 SO that the pattern may be taken out. The simplest form of pattern is a square block like that represented by Fig. 13. The parting will be made on the line A B, Fig. 13. Fig. 13 (a) the part of the mold below that line being in the nowel ; in this case all the mold will be in the nowel, the cope forming the top surface only. The next in point of simplicity is known as a Simple parted pattern, and is represented by Fig. 1, on page 6. In a mold made off this pattern, one-half would be in the nowel, and one- half in the cope, as represented by Fig. 13 (a). The line A B is the parting line of the mold and also of the Fig. 14. pattern. In this form of pattern, it will be noticed, the molder's parting and the pattern-maker's parting exactly coincide. When a pattern is so made that the partings can be arranged in this way, the molding may be very easily and quickly done. The process of molding such a pattern is described in Chapter II. Fig. 14 may be 48 WOOD PATTERN MAKING considered typical of a large class of pattern work. It is a pattern for a small car wheel having a central web. The molder's parting will be made on line A B. No parting is required in the pattern except that the boss, or hub, C, is usually left loose, so it will lift with the cope. Fig. 15 represents a pattern of a double flange wheel, and is a good example of a class of patterns where the molder's and pattern-maker's joints dO not coincide. ^ ^ I \ JL > L...J r , ^ Fig. 15. This would need what is called a three-part flasR, meaning that the mold is composed of three distinct bodies of sand, which, of course, involves the making of two molder's partings. One of these will come in the centre of each flange or lines A B and C D. The pattern will be parted at B F. The sand, or cores, that will form the part of the mold at G and H will be lifted with the cope -AK Fig. 16. down to the upper line of the web. The mold for a worm wheel is another good example of molding where the parting of the pattern does not coincide with that of the mold Fig 16 will make this quite clear. The pattern holders' joints or partings 49 will be parted along the line AB; the molder's partings, of which there must be two, will come on the lines C D and G H. All of the teeth will come in the middle part, or cheek, included in the space K. The two halves will, of course, be drawn from the mold in opposite directions, the inner curves of the rim, and the taper of the hub, affording plenty of draft. There is another form of molder's parting known as an "irregular parting," that must frequently be used on account of the shape of the pattern. The pattern represented by Fig. 17 is an example of this form of parting. In the molding of this pattern the molder's parting will be made along the Fig. 17. dotted line DD, so that the most of the mold will be in the nowel, which is very desirable, as it leaves less to be lifted by the cope. As indicated by the tapered prints 50 WOOD PATTERN MAKING shown at A and B in Fig. 50, a core will be used for forming a round hole through the casting. Another, but a more simple joint of this kind is shown by Fig. 18, which represents a cast-iron bracket. The parting of Fig. 18. the mold will be made along the dotted line AB. If a number of comparatively small brackets of this shape is wanted, the pattern can be parted through the central web, or a follow board can be made and fitted to a one- piece pattern. Fig. 19. A contrivance frequently used in molding, called sRcWCrin^ on loose pieces, saves considerable time and HOLDERS JOINTS OR PARTINGS 51 work in both pattern shop and foundry. An example of this is illustrated by Fig. 19, which represents a part of a cast-iron base for a wood -working machine. The whole casting is cored out; and, for convenience in molding, the pattern was boxed up to form a one-piece pattern, to be pulled from the mold in the direction indi- cated by the arrow. If the two bosses, A and B, were fastened on , they would tear up the sand . In order to pre - vent this they are sKcWCrcd On, that is, held in place tempor- arily with wire'skewers, as shown. As the mold is being rammed up, after sand enough has been rammed around the bosses to hold them in place, the skewers are pulled Fig. 20. Fig. 21. out. This, of course, allows the main pattern to be pulled out, thus leaving in the mold these loose pieces which can be pulled sidewise into the mold. Of course, this pattern could be parted through the center line, but that would entail a large amount of extra work in both 52 WOOD PATTERN MAKING the foundry and the pattern shop. By the use of this method, therefore, the extra work of making another parting is saved. Another way sometimes adopted for forming projections on a casting is made clear by Figs. 20 and 21. They represent a hollow, cylindrical cast- ing, with a flange on both ends, a projecting boss for a pipe on one side about midway of its height, and an opening through the top. The pattern will have to be parted on the line CC, and will require a three -part flask, with molder's parting along line BB. To form the projection on the side, one of two methods may be adopted: One, the use of a core print and core; the Fig. 2L other a core only, to be set in place at the time of ram- ming up the mold. If the second method is used, all that the pattern-maker needs to do is to make a core box with a pattern projection located in it. This core box is represented by Fig. 22. If the first method is adopted, a core print will have to be put on MOLDKRS' JOINTS OR PARTINGS 53 the side of the pattern, so as to extend from the top parting down to a point just below the projection. If a hole is to be cored through the projection, this would be the best way of doing the job. The examples given above of molder's joints do not introduce nearly all the ways and means employed by the molder for making molds. But they do give a good gen- eral idea of the most common ways, and will afford such suggestions to the beginner in pattern -making as to enable him to make patterns so that they can be "pulled" without injury to the mold. This should be the first consideration of the pattern-maker, as on it depends in la large degree the accuracy of the casting. If the mold is injured in any way by the pulling of the pattern, so that the molder has to mend it, the casting is rarely correct in shape. In the next chapter, the mat- ter of constructional joints will be taken up, that is, the building of wood patterns from the view point of the wood -worker. o a to O CHAPTER VIII. CONSTRUCTIONAL JOINTS In a consideration of this part of the general subject of pattern -making, two things must be given prominence, viz. : the strength and durability of the pattern, and its permanence of form. This latter is very likely to be interfered with by the absorption of moisture from the damp sand, thereby causing the wood to swell, and per- haps to warp. The amount of moisture thus absorbed depends upon the time the pattern has to remain in the mold, and upon the condition of its protective coating of varnish. To overcome any change likely to take place from this cause, several methods of arranging the various pieces of which the pattern is built up, are used. The par- ticular method to be employed in a given case depends on the size and shape of the pattern, and also depends, to a degree, on whether a large number of castings is wanted or only one. In order to secure the requisite permanence of form, it is better, other things being equal, to build a pattern of several pieces rather than to cut it out of one piece. For then the warping in the whole pattern is reduced to a minimum. In small patterns, however, this warping may be disregarded; therefore, a small pattern may be cut from a single piece of wood. This matter of constructional joints may be most easily comprehended by studying examples of forms likely to be required. 56 WOOD PATTERN MAKING When thin disks are wanted it is best to build them up of three layers with the ^rain of the pieces running tangentially to a small circle in the center, as illustrated by Figs. 23 and 24. The grain of the wood must run Fig. 23. Fig. 24. lengthwise and parallel to the longest side of each sector. After the pieces have been fitted together, a groove is cut in the edge of each, in which tongues of wood are glued and driven as illustrated by Fig. 24. When one disk has been glued up and the glue has dried, the sec- tors for the other disks may be glued directly to it with the joints running across the others, the angle depending on the number of sectors used to form the circle. This makes a very rigid construction and one which will no warp. If in building a pattern a thin, wide board is required and the other parts of the pattern are of such shape that they do not afford to it sufl&cient support to keep it from warping, a good way is to rip the board up into strios of CONSTRUCTIONAL JOINTS 57 from two to four inches wide (according to the width of the required board) and then glue the strips together with each alternate strip reversed, as shown in Fig. 25. In this way the warping will be reduced to the minimum because the alternate pieces are inclined to warp in oppo- site directions. A good way to support patterns of this general shape during the process of molding is illustrated by the lower part of Fig. 25. The additional pieces B and C are called counter ribs. The recesses made by them in the sand will be filled by the molder, or, as he expresses it, they are "stopped off in the mold." The shape of these counter ribs, which is more clearly shown at D, indicate to the Fig. 25. molder that they are to be stopped off in the mold. When - ever possible these should be put on the pattern so they will come in the nowel of the mold; these are also called "stop-off" pieces. Another way of building patterns that are round and flat and are supported by segments running around them, is to make the flat part of several strips rather than of a wide board. This is illustrated by i ) r 1 ese strips should not be glued together, hv^ 58 WOOD PATTERN MAKING held in position by the segments that are built on to them. If the pattern is more than 12 inches in diame- ter on the inside, it is advisable to insert at least one dowel in each of the joints between these strips to keep Fig. 26. them from springing sidewise. This need be done only for three or four of the joints near the center. A "slip" tongue joint may also be used instead of dowels. An- other way to overcome the effect of shrinking and swell- ing in large patterns is the use of what is termed Open joints. Fig. 27 -Fig. 28 If it is required to build a large pattern that is flat and comparatively thin, either circular or square, it CONSTRUCTlONAIv JOINTS 59 would be built as shown by Fig. 27; that is, the sides would not be built up by gluing narrow boards together, but they would be laid side by side with open joints between, of from one -sixteenth inch to one -eighth inch in width, and a slip tongue inserted. If the boards expand with moisture the width of the pattern as a whole does not increase ; the only effect is to partly close these open spaces. If the boards shrink the only effect is that the spaces increase in width. As broad -plated work is usually stiffened with ribs and flanges, the fact that the joints are open will not lessen the rigidity of the pattern. If a case should occur where there could not be support enough in the pattern itself, then the boards could be held in place as shown in Fig. 27, by a method which is practically paneling. A frame is made as for a panel door, and the ends of the boards fitted to a groove. This method may be used in connection with what is known as boxing up a pattern. This is illustrated in Fig. 28. Open joints are represented at a, a, a, Fig. 27. This method, bOXing Up, is frequently used for large pat- terns which if made solid would be unduly heavy and would be especially liable to become affected by mois- ture and dryness. The rebated joint should always be used at the corners in boxing up a pattern that is of a square or rectangular cross section. This is illustrated by Fig. 28. If the pattern was to be pulled from the mold in the direction indicated by the arrow, and was built as at (a) Fig. 28, then any change due to shrinking or swelling of the relative position of pieces b and c would leave an uneven surface on the vertical side which on being pulled from the mold would be likely to tear up the sand and thereby cause the molder some trouble If the joints are arranged as at (A) Fig. 28 this cannot 60 WOOD PATTERN MAKING occur. This form of ioint has another advantage, for if the joint were simply a butt joint, the ramming of the sand of the cope down on the face (E) would be likely to drive the top board down below the edges of the sides, but in this case, the piece K, being rebated into A and C, cannot be driven down. Fig. 29 represents an example of another type of hollow work, which, however, is not called boxing up, but lagging or lag^in^ up. This method may be defined as the building of patterns with longitudinal strips that run parallel with the axis of the proposed cylinder. It is used for turned work. The figure represents a sec- tion of the pattern of a pipe or column of any diameter ver four or five inches. A A is the joint of both pat- FiG. 29 tern and mold. B B are cross bars of polygonal shape on which the strips or lags are laid and fastened with glue and screws. The lags are also glued to each other except on the line A A. Fig. 30 illustrates another way of building by lag- ging. In this way much narrower strips are used, there- by reducing the work of turning and also requiring less lumber-. The parts for the core prints are built up first, and then the lags for the rest of the pattern are fitted an CONSTRUCTIONAI. JOINTS 61 glued and screwed to these, as is indicated by the figure. Should the body of the cylinder be long, two or more semicircular discs must be used to insure rigidity. Fig. 31 shows how this method of building up may be used for large cylindrical core boxes. If the work is done accurately, the work of finishing the inside of the box is reduced to a minimum. Fig. 30. Fig. 31. When annular patterns of six inches or more in diameter are wanted they are made by what is known as building up Witll segments. This is illustrated by Fig. 32, and when properly done makes a very strong construc- tion. The several pieces should be cut from the board in such a way that the grain of the wood follows the circle as near as may be. Therefore, in laying out the segments the chords of the curves should be parallel to the grain of the wood. In building patterns of this type, a number of short segments are sawn out and glued in 62 WOOD PATTERN MAKING courses, one over the other with the end joints alternat- ing or breaking joint, when the glue is dry the correct outline is imparted by turning or otherwise. By this construction shrinkage in the segments is reduced to practically nothing. Fig. 32. Examples of constructional joints of still another type of patterns, sometimes termed plate work, is repre- sented by Figs. 33 and 34. Fig. 33 shows a frame cut from solid wood, 18 inches wide and 2 feet 6 inches long, by 1 inch thick. It is clear that strength and per- manence of form is entirely lacking in bars (a a). Contrast the construction in Fig. 34. In this there can- not be any material alteration in width or length, in gen- eral or local dimensions, and there is the maximum of strength. The frame is made of five narrow strips. Alternative methods of making half lap points are shown. At the corners plain halving is shown. At D the dove- tailed form of halving is illustrated. The plain halving if properly made, glued and screwed, is very strong CONSTRUCTIONAL JOINTS 63 and permanent. For standard patterns, however, it is advisable to employ the dove-tail form. Another example of this same type, but of a very distinct form, is shown by Fig. 47. The finished casting is shown by Fig 46. It will be noticed that the joints are of the half -lap form. This figure (Fig. 47) shows the plate part of the pattern only, Fig. 33. Fig. 34. made up of three pieces. The pieces are so arranged that wherever there is a curve there is wood with the grain running practically tangent to it; consequently, if the joints are properly made and glued, it can be worked into shape without being broken out. Moreover, there is wood enough at all the angles so that the fillets may be worked in the solid wood instead of separate pieces being glued in for the fillets. For standard plate work it is always best to do this, even if it does take wider material. The added durability will more than pay for 64 WOOD PATTKRN MAKING the extra lumber, and then it also saves the time of mak- ing and gluing in the separate pieces. Round corners maybe formed, as shown by Fig. 35. Fig. 35. In this case the two pieces, A and B are joined in the usual way with a butt joint as at C; the piece D is glued into the angle and allowed to stand long enough to dry ; then the corner is worked to the required form outside and inside. In work of this kind it is best to work the inside first, because the piece can usually be held better if the outside corner is square, than if it is rounded. The block, after being fitted to the angle, may be sawed or planed to form, as indicated by lineB. This can be done more easily before, than after it is glued in place. As pattern -making is one of the most comprehensive of trades, and the demands of the engineering profession for complicated castings are limitless, it is impossible to anticipate the next forma pattern-maker will be called on to make. This being the case, only general methods can be considered in a volume of this size, treating on the subject. The joints and methods of construction that have thus far been considered are those most frequently employed in pattern -making. Special examples of types of pattern -making will next be taken up, for which one or more methods of construction will be given in detail. Clement Universal Bench Saw Williamsport Scroll Saiv CHAPTER IX. SPECIAL TYPES OF PATTERNS. Before taking up the subject of making special types of patterns, certain matters that apply, not only to special types, but to all patterns, must be considered. One of these is the preparation of the lumber. This consists in the first place of cutting roughly to size, the several pieces required for making the proposed pattern. They are then allowed to stand for as long a time as the job will allow, so that they may warp into and assume a nearly permanent form. If this is done, when they are cut to the final shape, they will not again warp and change the original form of the pattern. This additional seasoning is necessary, because lumber will change more or less in shape, when much of it is cut away, exposing a surface that has heretofore been on the inside of the plank or board. The foregoing constitutes the first step and may be termed Cutting thc Stuff POUghly tO size. The next step is planing up one or two sides to a true plane, and marking them as Working faCCS. Usually these planes should be made at right angles to each other. This is quite important, as, generally speaking, the accuracy of the work will depend to a degree upon the accuracy of these two faces. All lumber to be used in making patterns should be planed by hand before being put into the pattern, especially if a flat surface is SPECIAL TYPKS OF PATTERNS 67 desired. The ordinary rotary knife planer will not plane stuff fiat, therefore the hand plane must be used. If there is a Daniels planer in the shop it may be used to plane one side of the board ; the other may be passed through the ordinary planer. But even if this is done, the lumber should be planed by hand to insure a good finish, as the rotary knife will leave the surface more or less corrugated. The simplest patterns are those which are made in one piece, and which require no coring, although the F all over Fig. 36. Fig 37. castings themselves may be hollow. In commencing a pattern, one must first decide how it is to be removed from the sand, and where the parting line, if one is needed, should be. A simple one-piece pattern, around which to form a 68 WOOD PATTERN MAKING mold with a dry sand core, is exemplified by ihe stufiing box gland shown in Fig. 36. This figure shows the finished casting, which is to be finished all over. This is a type of a very large class of patterns which must be cast on end. It is what is generally known as a stufiing box gland. The finished casting is represented by Fig. 36, the finished pattern by Fig. 37, and the requisite core box by Fig. 38. Fig. 36 repre- sents also the drawing that would be sent to the shops. The gland is made from this drawing. Considering this pattern from the molder's stand- point, it is clear that if it is molded endwise, with the flange up, and if the molder's parting is made along the top of the flange, it can be readily pulled. The draft in this case should be one eighth inch for 12 inches. Each core print should be one inch long. When the amount of draft and finish is decided on, it is a good plan to make a full size sketch of the pattern as it will appear when ready for the molder, and with all required dimensions plainly shown on it. This should be done before one begins to make the pattern. Indeed, one may well fol- low this in the case of every pattern, for thereby many mistakes and much loss of time will be avoided. Accord- ing to the drawing Fig. 36, this gland is to be finished all over, so that in making the pattern there must be allowance for both finish or machining, and draft. As none of the dimensions are over six inches in any one direction, shrinkage may be disregarded. As this pat- tern is to be pulled from the mold endwise, the draft on the outside will have to be like that shown by Fig. 3, on page 14. One way to make a pattern for this casting is shown in Fig. 36 (a). If it is made in this way, it may be molded and leave its own core, but the hole can- SPECIAL TYPES OF PATTERNS 69 not be made parallel. It is usual to allow double the amount of draft on the inside for all small cores similar to this one. This would make considerable more work for the machine shop if the hole had to be finished. For this reason, if a large number was wanted, the pattern would be made as described in the following pages : To make this pattern it will be necessary to build Fig. 36 (a) Up a block of wood that is at least 3Mx3%x7 inches long. The best way to do this is to use two pieces 1/4 inches thick, and one piece three-fourths inch thick, glu- ing them all together, with the thinner one in the middle. In gluing up work of this kind, it is always best to have the thicker pieces on the outside ; for if the piece on the outside is too thin, it will, during successive moldings, be likely to become loosened on account of the action of the damp snnd on the glue. As soon as the glue is quite dr}^ the corners may be cut off with an axe or a chisel and mallet. The piece is now ready to be mounted in the lathe, and should be turned to a cylinder of three and five -eighths inches in diameter, which is the out- side dimensions of the flange. Now, laying a rule along the tool rest up against the cylinder, point off the measurements as indicated by the drawing, preferably 70 WOOD PATTERN MAKING commencing at the right hand end, that is, next to the back or dead center of the lathe. By commencing at that point any surplus material will be left at the other end, so that it will not be necessary to get so close to the chuck or driving center with the tools. First, then, make a mark about one -sixteenth inch from the right hand end for the end of the print. From this point measure one inch for the- length of the print; from this measure three and three -fourth inches for distance from the end of the pattern to the under side of the flange; from this point measure three -eighths inch for the thick- ness of the flange ; from this mark measure one inch for the length of the print on this end. Check up by measur- ing total length between the outside marks, which should be six and one-eighth inches. Now hold the point of a pencil at each of these marks, allowing the side of the pencil to lay on the tool rest; give the belt of the lathe a pull which will turn the cylinder, making a mark all the way around it. Now cut the cylinder to the required size below the flange, remembering that the core prints will have to be tapered, because this will be a vertical core. Now, if the successive steps have been done cor- rectly, the pattern will be like Fig. 37. The top print should be loose for the convenience of the molder. All the lathe work on this pattern should be done with scraping tools, except that the gouge should be used for roughing it to the approximate diameter. The next thing will be the making of the core box in which to make, or form, or mold the dry sand core. This box is shown by Fig. 38. This being a symmetri- cal core, one half box will be enough. To make this we proceed as follows : Take a piece of straight -grained pine, of such a width that after the semicircular groove SPECIAL TYPES OF PATTERNS 71 forming the body of the box is cut out, there will be left about three -fourths inch on each side. In this case, the box being two and one -quarter inches in diameter, and one and one-half inches for the two sides, the width of the piece will be three and three -fourths inches. The Fig. 38. Fig. 39. depth of the groove will, of course, be one and one- eighth inches, and there should be at least seven -eighths inch thickness of wood below this, which will make the required block 2x3^ inches and five inches long. The block should be planed on all sides ; one of the wide sides (for the top of the box,) and its adjacent narrow sides are to be straight and exactly at right angles to each other. To lay out the lines for this, fasten the block in the vise with one end down even with the top of bench, or vise. Now set the dividers to the radius of the required curve, one and one-eighth inches, and put one leg of the dividers in between the block and the vise jaw, on the side intended for the top of the box, approxi- mately in the center of the side; then describe a semi- circ e on the end of the block, as shown at Fig. 72 WOOD PATTERN MAKING 39. Now with the gauge set to the distance c to a, make a mark along the top or face side for the whole length from the point a, then extend the gauge to point b, making another line the whole length of the block. On the other end make another semicircle. This completes the laying out of the core box The wood must now be taken out just to these lines. This may be done in two ways, the better of which is by the use of the core box plane. This is a plane whose face instead of being just one surface, is composed of two surfaces set at right angles to each other, as shown by Fig. 40. The cutting iron is narrow, and ground to Fig. 40. an acute angle, so as to conform to the shape of the plane at the apex of the angle forming the two sides of the face of the plane. The principle of its construction and use is, that the greatest inscribed angle in a semicircle is a right angle. The whole of the wood on the inside of semicircle cannot be cut out with this plane, so first use a gouge to cut it out to within one -eighth inch of the mark ; then cut it exactly to line along both gauge marks; then, holding the plane in such a way that the fingers of the left hand will form a guide to keep the plane to the line, cut a shaving along the line on the side SPECIAL TYPES OF PATTERNS 73 farthest from the operator. This is illustrated by Fig. 41 , in which the upper curved line represents the work as done by the gouge, and the semicircle immediately below it is the circle to which the work is to be cut. There is now a guide for both sides of the plane, so that by exer- cising a little care the plane may be passed along through - Fig. 41. out the length of the block, cutting a shaving at each stroke. This may be continued until about one -third of the whole is worked out. Now the block may be turned end for end, and the other side treated in the same way down to about midway of the distance; then turn the block again and finish the other side. This will make a very neat and accurate job if the plane is in proper con- dition. Another way by which the plane may be started is to nail a thin strip of wood along the gauge line as represented at (a) Fig. 41. This is used as a guide for the plane. After the groove has been cut down a short distance (about one -sixteenth inch), this extra piece must be removed to the other side and again used as a guide. This guide piece must be taken away before work- 74 WOOD PATTERN MAKING ing the groove down very much, for if allowed to remain it would change the size of the semicircle made by the plane. The cutting iron of the plane should be so sharpened and set as to cut on one side only, preferably on side A, Fig. 40. If it is allowed to cut on the other side, and used as indicated by Fig. 41, it will cut the groove too large, making the core box larger in diameter than wanted. Another way to cut out this part of the core box is to use a gouge to remove almost all the material, using a round plane to finish with. Doing the job in this way will involve the use of a straight edge to test the straightness of the work from end to end. For this purpose, a straight edge with a thin cross section is necessary. A try -square if long enough, is a very good tool for this purpose. Fig. 41(a). It will be a great advantage to set the cutting iron so it will cut the wood on one side of the plane only. In order to do this it is best to cut away a small amount of wood on one side of the plane, as indicated at A Fig. 40. This plane is almost indispensable for making core boxes of the shape represented by Fig. 41 (a) , for what may be SPECIAL TYPES OF PATTERNS 75 called conical cores. As the curve changes continually throughout the entire length, it is almost impossible to make a cavity that is uniform, if one uses the gouge and round plane. A straight edge and templet must be used frequently to test the work. But the core box plane overcomes all these difficulties, and if only the two sides of the cavity are correctly located, and then worked to the lines with the gouge, the plane will do the rest of the work. There are machines on the market which do this kind of work very accurately and rapidly. One of them is illustrated on page 45. This is the Crane Core Box Machine. Whichever method is used in making this part of the core box, it needs to be smoothed on the inside with sandpaper. If the box is small, this is best done with sandpaper placed around a cylinder of wood, the cylinder being about one-fourth inch smaller in diameter than the box. If the box is large, a piece of wood about four or five inches wide and an inch thick, with one side planed approximately to the curve of the inside of the box, will be better. To form the ends of the box marked A A in Fig. 38, the following is the best way: Make two pieces of wood four inches long and two inches wide, and exactly one inch thick. Plane them so that two of the narrowest faces will make a good joint at right angles to the wider sides. Now face up a chuck about six inches in diam- eter, and while it is revolving in the lathe, make a fine pencil mark or dot in the center. Place one of the pieces flat on the chuck, so that one of the face edges will pass through this dot mark; nail it to the chuck in this posi- tion, and then place the other piece alongside, and nail it also. If this work is correctly done, the chuck, with 76 WOOD PATTERN MAKING pieces nailed on, will look son:ething like Fig. 42. This is now to be put on the lathe, and a hole of the shape of the core print on the pattern turned into it. If the blocks were properly placed, each will have a semicircular hole in it, representing one -half the frustrum of' a cone, whose dimensions correspond exactly with those of the core print on the pattern. These are now to be taken from the chuck and nailed and glued, one on each end of the body of the box previously made. This must be cut to the exact length required, which in this case will be four and one -fourth inches. It is necessary that a core box for a Vertical core should be about one -eighth inch Fig. 42. longer than the pattern, so that the cope of the mold will be sure to fit tightly around the core ; then no metal can flow up alongside of it and over the end of the core, thus covering up the vent and causing the casting to blow. For the above reason all Vertical cylindrical cores should be one -eighth inch longer than the total length of the pattern and prints. To complete the box it is only necessary to nail pieces (B B. Fig. 38) one on each end, and then give a taper at the point C. To make the core, SPKCIAI. TYPKS OF PATTERNS 77 two halves are made in this box; after drying, they are pasted together, making a complete core. The next example is very similar to the former one, but, having a flange at both ends, it will have to be molded horizontally, and will therefore require a horizontal core The completed casting is represented by Fig. 43, and a pattern for producing it by Fig. 44. On account Figs. 43. Fig. 44. Fig. 45. of the shape of this casting it will be best to make the pattern a parted pattern. This will save the molder some time and work, as it will give a form that is easily removed from the sand. In making this pattern, the first thing to do will be to get two pieces of wood of such dimensions that when they are put together the pattern can be turned out of them. As will be noticed by the 78 WOOD PATTERN MAKING drawing, there is no finish required except on the face of the flanges. Allowing for finish, the length of the pattern without the core prints will be six and one- fourth inches. The core is to be one and one-half inches in diameter, so the prints will be one and one -half inches long; then two inches more must be added for fastening together at the ends, making a total of eleven and one- fourth inches for rough size. Two pieces then are needed, eleven and one -fourth inches long, four inches wide and two inches thick. The next step will be to plane one of the larger sides of each piece to a true sur- face, to form a joint between them. The next thing is to locate the holes for the pattern pins that will be necessary to locate the two halves in relation to each other after being separated. The most practical way to do this is as follows : On the plane sur- face of one of the pieces locate these holes with a pencil mark; this mark to be, say four and five inches from a center line approximately on the center of the width. If the pins are thus located, the molder will not err in putting the two halves together, for if he happens to do it incorrectly, he will at once recognize his mistake. Having marked the points where it is desired to put the pins, take two small brads and lay them on the block with the heads at these points; now carefully lay the other piece on these brads, and having brought it into exactly the desired position, strike the top piece a light blow with the hammer or mallet. This will cause the heads of the brads to make corresponding impressions on both blocks. At these impressions, bore holes one-half inch deep. The diameter of the hole is of small moment; for patterns of this size, one -fourth inch is about right ; the larger the work, the larger the pins should be. SPKCIAIv TYPES OF PATTERNS 79 The next thing will be to make the pins, for which a piece about ten inches long will be found the best. Select a piece that is straight in the grain, and rip to such a size that one side of the square stick equals the diameter of the hole, plus one-eighth of an inch. With the jackplane plane this into an octagonal form. Then, grasping one end in the left hand and laying the other end on the bench, with the block -plane plane off the the corners, making it as nearly round as possible for about three inches of its length. This round part should be made to fit the hole exactly, that is, at the extreme end. With knife and sandpaper, or file, round this end to an approximately parabolic form. Now set it into the hole in the piece into which the pins are not to be fas- tened, far enough so that it exactly fits the hole. Make a pencil mark part way around it, right at the surface of the block. Now measure the depth of the hole into which the pin is to be fastened, and mark this distance along the pin from the mark previously made. This is the point at which to saw the pin off. Now, if this pin be driven down into the hole clear to the bottom, the first mark will come even with the parting and will exactly fit. By means of these pins, the two parts, after being separated, may be brought together again in exactly the same relative position, and will be held firmly so that they will not slide or shift sidewise during the process of molding. They should be loose enough so that the pattern will fall apart of its own weight, but still not loose enough so that there is any perceptible movement sidewise. When both pins are in place, the blocks are ready to be fastened together. There are three ways in which this may be done. If there is time to wait for glue to dry, the best way is to put glue on the ends of each piece for a dis- 80 WOOD PATTERN MAKING tance of about one-half inch, and clamp them together with a handscrew or other clamp. If it is desired not to wait for the glue, then a screw may be put through the ends, fastening them together in that way. It is advis- able, for convenience in turning, to use a short screw, boring a hole large enough to receive the head of the screw. For a piece of this size a one and one -fourth inch screw may be used. If care is taken to have one- half the length of the screw in each piece, it can be turned to the required size of the print, out to the extreme end. The third method is to clamp them together with "dogs, ' ' which are small square staples made for the purpose. When the pieces are thus fastened together, they are ready to be placed in the lathe and the turning proceeded with. This may be done practically in the same way as in the previous example. One must allow for draft, and also for finish on the faces of the flanges, making these faces, and the ends of the prints convex as shown in Fig. 44. The next thing will be the core box. As this pattern requires what is known as a plain, cylindrical, horizontal core, and is therefore symmetrical, only a half-box is needed. But if it is desired to reduce the cost in the foundry, a core box like the one represented by Fig. 10, page 39, in the chapter on cores, would be used, the core being made complete at one operation. The half- box would be made as directed for the straight part of the core box in the last example, with end pieces, as repre- sented by Fig. 45 If a whole box is made, then the block would need to be twice as long, and worked out as in Figs. 38 and 39. After this is worked out, it should be cut in two pieces and pinned together in the same way as was done with the two pieces for the SPECIAL TYPKS OF PATTERNS 81 pattern. One way that is quite practical is the fol- lowing: After cutting the pieces the correct length, place them together in their proper relation to each other; fasten them in the vise in a vertical position, with one end above the bench top, and bore a hole of the size required for the pin clear through the first piece and about half an inch into the other. Now by putting the pin through the hole, it will be filled and make an accurate and workmanlike job. If brass pins are used, this could not be done, because the pin would not fill the hole; and as the pin and its tube are of a different size, the hole could not be bored with the same bit. The inside length of this core box should be about one -eighth of an inch shorter than the total length of the pattern and prints, so that the core may be more easily set into the mold. Oliver^ ^ Bandsaw CHAPTER X. PI.ATK WORK AND IRREGULAR PARTING The next example to be taken up is typical of a quite large class of pattern - work, generally known as plate work. It is usually comparatively thin in cross -section in at least one direction. This class of work includes shafting, hangers of different patterns, some kinds of small pump standards, and any kind of work that is composed of two webs running into or crossing each other. This last is illustrated by Fig. 46. The example to be used to demonstrate the methods usually followed in building patterns of this type is represented by Figs. 46 and 47. In order to make the best pattern for durability and per- manence of form, the foundation should be built of three pieces, as shown in Fig. 47, which is almost self-explan- atory. Of course, this part of the pattern could be built of one piece of board, but it would be very weak through the portion marked A. By building it as represented, two things are gained; it is uniformly strong throughout, and smaller pieces of wood may be used. As in the case of all other patterns, so in this, it should be first deter- mined how the pattern is to be withdrawn from the mold. It will soon be seen that the best way will be to have the face marked B (Fig. 46) down in the nowel ; thus there will be left an almost flat surface for the molder's parting, which will then occur along line C D. It will, of course, be neces- 84 WOOD PATTERN MAKING sary to make part E loose, so it will lift with the cope sand. This is a type of what is known as lOOSC piCCCS molded in the cope and drawn therefrom after it is lifted off from the nowel, or lower part of the mold. The Fig. 46. method now to be described of laying out and building this pattern, may be used in building any pattern of this PLATE WORK AND IRREGULAR PARTING 85 general type ; modifications of it may be introduced when needed. The first step to be taken in making this pattern is the making of two pieces of board about fifteen inches long, by two and one -half inches wide, and five -eighths inch thick, and one piece about nine inches long, four inches wide, and five -eighths inch thick. These must be planed on one side to a true plane, with the edges straight and at right angles to the side ; a faCC mark should be put on each piece. Now the two long pieces should be cut to shape, so as to make a good joint at F, care being taken that the two lower corners are far enough apart to include all of the pattern at that point. Tack these to the bench or laying-out table in their proper position with relation to each other; then locate points G H, and lay the third piece on the others with its edge at these points, and make knife marks across the two pieces. Now, without moving the third piece, make marks on it with the point of the knife at the points K, L, M, and N; then finish the laying -out, and cut out gains halfway through the two long pieces. Then cut out the ends of the short piece to the same thickness, but on the opposite side ; fit them together and glue them and put them in clamps till dry. While this is drying, a piece of board about fifteen inches long, six inches wide, and one-half inch thick, can be gotten out. Out of this can be sawn pieces for making the curved pieces that are built on to form the raised portions that are to be glued on to the main piece. These should be cut from the board so that the grain of the wood will run parallel with a chord of the curve, making the segment not to exceed one -quarter of the circumference of the circle. If they are made longer than this, there will be too much end 86 WOOD PATTERN MAKING grain. The straight pieces may also be gotten out at this time, so they will be ready when wanted. When the glue is dry on the three pieces that together form an A -shaped piece, it is to be planed on both sides to true planes until it is one-half inch thick. It is now ready to have the lines laid out on it as shown by Fig. 47. In Fig. 47. laying out these dimensions, the shrink rule should be used, as that will allow for the shrinkage of the metal in the casting. After these are all laid out, it may be sawn PIvATE WORK AND IRRKGUI,AR PARTING 87 out on the band and jig saws. In doing this sawing, it is best to cut just outside the line, so that in filing and finishing the edges, the marks may serve as a guide. It is now ready to have the pieces set on to form the pro- jecting webs, which may be cut from the one -half inch piece already mentioned. It will be best to commence at the top of the pattern. The first will be a solid piece extending all over the upper end down to and including the semi -circle that joins the long outside webs. After this the other cir- cular parts may be cut out and put on. Now the pieces to form the feet may be made and glued in place ; then the straight pieces should be nicely fitted to these and glued in place. Now a piece of wood may be gotten out to form the fillet around the bearing where it joins the main part of the pattern. This should be about three -eighths inch thick, and should be large enough to extend three - eighths inch all round outside the bearing. For con- venience in cutting out the fillet, it is best to let the grain of the wood in this piece run parallel with the out- side line of the pattern at this point. A piece is also needed to go on the other side to form a fillet on which to pin the loose piece. (K Fig. 46.) Now a piece to form the bearing itself may be made. As this is required to be more than a half circle, it will be best to make it with the planes. According to the dimensions given, it will need to be of the following finished measurements : about four inches long, two and one -fourth inches wide, and one and three -eighths inches thick. It should be planed square to these dimensions, and a semi -circle described on each end, and then planed and sandpapered down to it. A piece can now be cut from this just two inches long, and fastened on top of the three -eighth inch fillet 88 WOOD PATTERN MAKING piece. Both ends of this piece must be square, so it will set in a vertical position on one end, and so the core print to be made later will fit well. Apiece of this is required for the other or cope side, one inch long. This, how- ever, will not be fastened in place permanently, but will be pinned on so that it will lift with the cope sand when the cope is lifted off. The best way to do this is to place it in a correct position and drive two small brads through it, taking care not to put them where the pin holes are to be bored. Now, with brace and bit, bore two holes clear through it and into the other part of pattern to a depth of about one- half inch. A one-fourth inch auger bit is a good size to use for this purpose. Now make* pins as directed for use in the parted pattern on page 78. In this case they can be put through I. Si ■ Fig. 48. and fill the holes, as they will have to be on the loose piece. The next thing will be to make the core prints. These will extend the whole length of the bearing, and of course the length of the prints besides, and as this is a vertical core, will project one inch beyond the pattern on each side. To make these prints for this particular job, take a piece of wood about seven inches long and one and one -half inches square, place it in the lathe and turn to shape and dimensions as shown by Fig. 48. The shaded portion will be cut out so it will fit down on to PLATE WORK AND IRREGULAR PARTING 89 the pattern already made. The line just above the shaded part is the point to cut through so as to coincide with the pattern parting. To complete this example a core box will be needed, which will be made as shown at Fig. 49. The process is Fig. 49 the same as already described, except as to the pieces marked X. These are to form a crease or groove in the core, to form the babbitt pieces on the casting shown at O, Fig. 46. These are simply pieces of wood one -eighth inch thick, of a size equal to the cross -section of the core box, and with a semi -circle cut in on one side, whose diameter is one -inch, that is the size of the shaft the bearing is intended to carry. In building the box, the pieces must be nailed in between the body of the box and the parts forming the prints. The completed box is shown at Fig. 49. The pattern for a hook lever for Corliss valve gear will be the next one taken up. This gives a good exam- ple of what is known in the foundry as an irregular part- 90 WOOD PATTERN MAKING ing, and is illustrated in the chapter on molders' joints by Fig. 17, the molders' parting following the heavy dotted line. It is also a good example of what may be called a built up solid, Onc-piCCC pattern, meaning that the completed pattern has no parting. This is typical of a very large class of patterns, as all patterns would be made Onc-piCCC if they could be conveniently molded in that shape. Before commencing the actual work on this pattern, notice particularly the position of the molders' parting and then the direction of the required draft. The first pieces to be gotten out will be the two of which to make the arms, each about four and one -half inches wide, ten inches long and three -fourths inch thick. These should be planed to a true surface on both sides Fig. 50. to the exact thickness, three -fourths inch, then nailed together so their center lines will be at the required angle PI. ATE WORK AND IRREGUI.AR PARTING 91 of 105°. On one surface of these lay out the shape accurately as indicated by the drawing, allowing about one -sixteenth inch for draft around the central boss. The arms may now]»be sawn out on the band saw, leav- ing the marks as a guide for finishing with a file. The round boss or disk A (Fig. 50) may now be made. This should be sawn out about four and one -fourth inches in diameter, one and one -fourth inch plus one -eighth inch for "finish" in thickness, and mounted on the lathe and turned to exact dimensions , which are four inches in diam - eter at B and four and one -sixteenth inches at C, Fig. 50 (a) . Another boss is needed at D, Fig. 50, but only three- eighths -inch thick. These may now be nailed in place on kA>| k-2 T 4" r 5