PATTERN MAKING American School of Correspondence Copyrighted 1898 BY American School of Correspondence BOSTON, MASS., U. S. A. K ^AVi\xj, s : '/ PATTERN MAKING maker will be called upon to work out the designs from which he is to make his patterns and he thus becomes the real designer. Finally, the pattern makeris seldom required to make two patterns that are identically the same. His work is, therefore, varied and he must be prepared to apply to the solution of new problems, such principles as he may have learned. flaterials for Patterns. As patterns are subjected to more or less rough usage, and are alternately wet and dry, it follows that the ideal material is "one whose hardness is such that it can withstand the wear and tear of handling, and at the same time be impervious to the effects of moisture. Such a material is to be found in the metals but, as the cost of working them into the proper shape is considerable, some kind of wood is usually sub- stituted. Kind of Wood Used. If, then, wood is to be used, another qualification is to be added, namely, it should be easily worked. The best wood for the purpose is undoubtedly white pine. It can be obtained with a straight grain and free from knots. In choos- ing the wood, that which comes from the Northern States or Canada and has grown upon high ground, will be found to be the most satisfactory. Care should be exercised in the inspection of the wood, that it is clear, straight grained and free from knots. The straightness of the grain can be determined by the appearance of the sawn face. This should present an even rough- ness over the whole surface. It should be seasoned in the open air but preferably sheltered by a roof and be piled so that the air has free access to all parts of the stick. Kiln dried lumber is likely to be brittle and does not wc rk as easily as that which has dried more slowly in the open air. If the selection is to be made for any special work, the size of the timber should be proportioned to the place in which it is to be used, but for general pattern work, planks two inches thick will be found a convenient size. Lumber of this thickness can be properly dried and is also large enough for almost any pattern. It has the further advantage of not checking or cracking as easily as thinner stock. Pine, however, is soft and weak so that, if small and strong patterns are desired, a harder wood is usually employed. Mahogany is the most suitable for this purpose, and the same care should be PATTERN MAKING. exercised in its selection as in the case of pine. Genuine mahog- any, straight grained and free from defects, should be used and not the cross-grained bay wood that is often sold in its stead. Cherry is also extensively used and black walnut, beech, and maple to some extent. Black walnut is brittle and may crumble ; beech and maple are likely to warp. It may be stated, then, that, in the United States, white pine is the material commonly employed for pattern making. Warping and Twisting of Wood. Observation shows that if one side of a piece of wood is kept damp and the other dried, the former will expand and the latter contract so that the piece which was originally straight becomes curved as in Fig. 1. A common example of this is to be found in the planking of a board side- walk, where the upper surface is exposed to the drying effects of the sun, and the lower to the moisture arising from the ground. It requires more time under the same conditions for a large piece of timber to become dry than it does for a small piece ; because the moisture at the center has farther to travel before reaching the surface. Hence, small pieces cut from a large stick that has been seasoning, will not possess the same degree of dryness throughout their respective masses. If two of these pieces are fastened together the combination will warp as a result of the drying of the damper piece. It is well, there- fore, when making a pattern to get out all of the pieces and allow them to season for a while so as to avoid warping. Tools. The tools of a pattern maker's kit do not differ essentially from those of a carpenter who is doing first-class work. While it is impossible to give a list of all the tools that a pattern maker may find convenient, the following are the more essential. Saws, — cross-cut, rip, and miter. Planes, — jack, jointing, smoothing, compass, rabbet, and core box. Chisels, — firmer and paring of various widths. Gouges, — firmer and paring of various sizes, both concave and convex. Squares, — fixed and bevel. e PATTERN MAKING. Gages, Compasses, Trams, Calipers, Mallets, Hammers, Screw- drivers, Pliers, Spoke shaves, Brad awls, Oilstone, Scriber, Stand- ard and Contraction rules, and Clamps. Saws. Cross-cut and rip saws : these two kinds of saws are Fig. 2. as their names indicate, for cutting across the' grain and ripping with the grain of the wood, respectively. Their general appear- The difference between them is It is to be noted that that nearly all ance is shown in Fig. 2 the shape of the tooth. i a Fig. 3. A Fig. 4. Fig. 6. woodworking tools do the cutting as they are moved away from the workman. The cross-cut saw has a tooth with the front or cutting edge inclined back from 1 f^xT^M^V^xN Fig. 5. the front, with the two edges beveled to form a cutting edge as shown at a of Fig. 3. The alternate teeth of the cross-cut saw are beveled on opposite sides as shown in Fig. 3. In addition to this, the alternate teeth are given a set as indicated by Fig. 4 at a and b. This set causes the saw to cut a wider slot or kerf in the wood than the back of the blade and thus prevents the material from pinching. The front edge of the teeth of a rip saw are at right angles PATTERN MAKING. to the line of the blade and are sloped back as shown in Fig. 5. They have no set as in the case of the cross-cut, but the points are broadened or swaged out by hammering as in Fig. 6. In this case the kerf is the width of the swaged points. A cross-cut saw can be used for ripping, but it is exceedingly difficult to use a rip saw as a cross-cut. Fit niter saws are used for sawing joints and miters across the grain. The teeth are usually very fine and the blade is stiffened by a heavy strip of metal along the back edge. It is illustrated by Fig. 7. Planes. The jack plane is used for removing the rough sur- face of the timber as it comes from the saw and thus preparing it for the jointer and smoothing planes. The stock of the plane is usually made of beech though it is sometimes of metal. The blade Fig. 8. or plane iron is of steel and is often made in two pieces : one the cutting blade and the other a strengthening piece or cover held to the former by a screw. The blade is held in position in the stock by a wedge which is usually made of wood. The blade should be ground slightly rounding on the corners so that they will not dig into the material for the pattern. The sharpening should always be done on the bevel face of the knife and not upon the flat sur- 8 PATTERN MAKING. face. This applies to all wood-cutting tools. After the iron has been sharpened the cover should be screwed on, the iron projecting a very short distance below it, as in Fig. 9. The whole is then put in the mouth of the plane and adjusted with the wedge, so Fie. 9. that the blade projects a short distance (about ^ inch) below the face of the stock. By looking along the face of the stock the amount of the projoction is seen and if it should be too much, a light blow on the top of the plane at the front end will drive the iron back. The amount of the projection determines the thick- ness of the shaving. Fis?. 10. Jointing Plane. This plane resembles the jack plane except that it is longer, and, therefore, gives a greater surface for straight- ening. It is shown in Fig. 10. The iron is ground the same as in the case of the jack plane, except that the rounding should not extend in for more than from Jg inch to | inch from the edge. The projection of the blade below the surface of the stock is also less than in the case of the jack plane. Smoothing Plane. This plane is shorter than either of the others. The blade should be sharpened and set like the jointer. PATTERN MAKING. 9 It is used for smoothing a surface rather than for trueing it. The plane is illustrated by Fig. 11. Compass Plane. This tool resembles the smoothing plane except that the working surface is convex instead of flat. It is used for smoothing concave surfaces where the curvature runs with the grain of the wood. It is shown in Fig. 12. Pig. 11. Fig. 12. Rabbet Planes are tools whose sole or working face has a shape to conform to the surface of the work to be done. They may, therefore, be of an infinite variety of forms, but the two in most common use are the narrow convex and the concave as illus- trated by Figs. 13 and 14. The flat sole, as shown in Fig. 15, is also frequently added to the kit. The use to which these planes are most extensively applied is the making of mould- ings and fillets. Core-box Planes. The Fi^r. i3. woi-king out of cylindri- cal core-boxes is of every day occurrence in all pattern shops. This is done by first roughly shaping the work with a gouge, then bringing it to a circular shape with a core-box plane, and finally smoothing with a round-soled plane, Fig. 16. The core-box plane, Fig. 17, is con- structed upon the principle that two chords drawn from any point on the circumference of a circle to the opposite extremities of any diameter, form a right angle with each other. Such a plane is 10 PATTERN MAKING. shown in Fig. 17. The two sides forming the soles are at right angles to each other, and have a knife or plane iron in the corner. The method of using is as follows ; one-half the core-box is roughed out with the gouge as shown in Fig. 18. The points b and d on the edges of the groove are cut away as in the finished box and are made exactly to size throughout the entire length. Stock is left below for removal as shown by the solid line. The finished core is to correspond to the dotted semi-circle. The plane is so placed that the sides occupy the posi- Fi, r> !4 # tion shown by the two full lines a b and b c and these faces always kept in contact with the edges b and d. As the plane cuts away the surplus material its sides will occupy the positions indicated by the angles a' b' , Fig. 78, it is well to make wooden templates so that the core may be easily cut to the required depth. If made too deep the metal of the seat would be thinner than it should be ; if not deep enough, the passages would be contracted and the weight of the valve increased. These templates should have a form resembling the contour of a vertical section of the passages for which they are intended. Thus a template for the narrow neck of a would be shaped as in Fig. 80, and for the space beneath the valve seat in b as shown in Fig. 81. After the core-boxes have been carefully cut out with the hand tools, they should be scraped, sandpapered, and shellaced. The pattern itself can be turned in the lathe, the two parts being held together as by the method described in connection with the pipe pattern, Fig. 69. After the turning has been done the hexagonal ends should be cut out of the same material. This may be done if the rough material at these points is left untouched by the turning gouge and chisels. Turning leaves the body in the shape of a globe. After the hexagonal ends have been cut, the neck for the stuffing-box and the stem is to be turned and glued in position. As the line of intersection of the cylindrical neck and the spherical case is a circle, it is simply necessary to flatten the top of the case and lay the neck upon it. The connection between the two at a, will then be angular and must be eased off by the use of a fillet. The coreprint of the neck is turned solid with the neck itself which must, of course, be made in halves like the body of the valve. Where a piece is laid upon a pattern in this way it is well to 50 PATTERN MAKING. strengthen the glued joint by the use of a thin plate of metal firmly screwed to the two parts thus united. Pillow Blocks. In the ordinary pillow block, Fig. 82, we revert, once more, to the single-piece pattern. These patterns are exceedingly simple to construct. They are in such constant Fig. 82. O o o o Fig. 83. demand that every pattern shop is frequently called upon to make the different sizes. Where the width of the block of the length of the bearing is not more than 12 inches, the base, B, may be made of one solid piece of board ; one face should be left smooth if it is intended to finish the bottom in a machine. If the bottom is to be chipped to PATTERN MAKING. 51 fit into its position it should be ribbed as shown in Fig. 83. The height of the ribs should be about |- inch. Upon the upper face should be glued and nailed the body of the block. It should be built up and the shaft core should be cut out with the core-box plane as already described for the core-box. It will facilitate this work if the grain of the wood is laid to run across the block. As blocks of this kind are usually babbitted upon the rough casting, provision must be made to hold the same. For this pur- pose a narrow rib is made around the inside of the box at the ends as shown by the dotted lines of Fig. 82. The top of this rib should be ^ inch wide, the bottom | inch and its height should be dependent upon the nominal size of the box. For large boxes of Fig. 84. eight inches or more diameter they may be f inch high, but for ordinary boxes \ inch is enough. The top of the rib should be | inch from the shaft. That is to say, the diameter, d, should be \ inch greater than that of the shaft for which the box is intended. After the box has been formed the coreprints, a a, are to be fastened on, and the prints, b b, put on loosely so that they may be imbedded in the sand of the cope. The cores which are set in these prints form the bolt holes by which the block is held to its foundation. In moulding, pillow blocks are cast bottom up, thus insuring sound metal for the completed casting. The cap for this block, Fig. 84, is made in one piece, it being quite possible to cut away the sand so that the parting between the cope and the drag will come along the line e e as described in connection with the handwheel, Fig. 58. 52 PATTERN MAKING. This pattern is also cast bottom up, insuring sound metal on . the top that is exposed to view. Bearings. Where babbited boxes are not used, it is custom- ary to insert a brass or soft metal bearing for which a special pattern is to be made. The details of such a pattern do not differ in any way from those intended for use in iron castings, but a slightly different shrinkage rule must be used. Columns differ somewhat from pipes. Instead of a smooth outer surface they are commonly fluted or fitted with ornamenta- tions of some sort. It will be seen by reference to a half section of a fluted column, Fig. 85, that if the pattern were to be made like the completed casting it would be impossible to get it out of the mould without tearing away the sand where the pattern is under cut as at a! a'. Loose pieces are therefore used. The body of the pattern is made , octagonal as shown by the line ABODE. The loose pieces forming the flutes are held to the main body by pins that stand at right angles to the line A E. After the sand has been rammed, the body included in the lines A B C D E is lifted out leav- ing the parts A a b B, B b c C, etc., imbedded in the sand. Then one after another these are lifted out. These fluted sections should never be so faw in number that they cannot be lifted out without tearing the sand. In small work six sections can be used ; eight is better and in some twelve are needed. Other forms of ornamentation are put upon columns in a similar manner. Leaves or flowers are held by pins or in grooves in such a way that the main body of the pattern can be lifted out without disturbing them, and they are then withdrawn from the sand through the cavity left by the main pattern. Cores for Columns. Cores for columns may be made in core- boxes as in the case of those for pipe, but where the core is long and straight no core-box is needed. The core is usually built of loam about an iron pipe as will be explained in the section on Foundry Work. Fig. 85. PATTERN MAKING. 53 5 Where the core is to follow the lines of the ornamental mould- ings on the outside of the column, it may be provided with a special core-box or better with a sweep as shown in Fig. 86. This sweep is used to shape the loam core that is to be built up on an iron pipe. Fig. 86 is the outline of the template that is to be used in sweeping the core for the interior of the columns shown in Fig. 87. Thin Patterns. Where the casting to be made is thin extra precaution must be taken. The unequal pressure caused by ramming the sand will distort a thin pattern so that the casting will not have the proper outlines. This may be prevented by support- ing the pattern while the sand of the nowel is being rammed about it. Fig. 88 represents a section of a railing cap. If the pattern B were to be set with its edges a a resting upon the moulding board and the sand of the drag rammed down upon its upper face, it would be sprung out of shape. To avoid this the follow board A is made to exactly fit the under side of the pat- tern. Then when the sand is rammed, the f^ whole pattern is supported and there will be no distortion. When the cope is rammed the follow board is removed and the sand of the drag supports the pattern. Thin patterns and all that are likely to suffer from distortion due to sand pressures should be pro- vided with accurately fitting follow boards, and where the number of castings is large, the patterns themselves should be of metal. Engine Cylinder. Engine cylinders may be made in either of two ways. There may be a regular pattern or a loam mould may be constructed. The latter method will be fully described in the section on Foundry Work. It may be stated in general that loam moulding is used for cylinders of large dimensions and pat- I 86. Fig. 87. Fig. 88. 54 PATTERN MAKING. terns for those of small. The dividing line varies in different foundries and ranges from 24 inches to 30 inches of diameter. In order that a pattern maker may construct a cylinder pattern, he should be provided with drawings showing in detail a Fig. 89. longitudinal section, a cross-section, and a plan of the completed cylinder as in Figs. 89, 90, and 91. The longitudinal section should be redrawn to full size on a chalked board as described on page 3. In order that the weight of the pattern may be as small as possible the cylindrical portion should be built up and hollow. The dotted lines (Fig. 89) at A, B, and at the ends indicate the core-prints on the pattern. First as to the two latter, it will be seen that they are smaller in diameter than the finished bore. This is to allow for finishing as already explained. The barrel of the cylinder is to be constructed first. This should be made up of strips one inch thick. First cut four pieces as A A (Fig. 92) carefully jointed in pairs along the line a a. Fie. 90. PATTERN MAKING. 55 These are to form the ends of the barrel. They should be fastened by dowels. The number of faces of the polygon should depend upon the size of the cylinder. Next cut and fit on each face of the polygon the strips b b, glueing and nailing them in position. Thus a hollow polygonal ; ! s * -I Fig. ©1. prism will be formed, which may be centered on its parting line a a and turned to a cylindrical form. When this has been done the casing for the passage of the ports and the plugs for supporting the cylinder are built upon the curved faces of the cylinder as turned ! a and the steam-chest seat laid on. The core prints for the ports and exhaust pipe are then glued on and finally the core-prints for the body fastened. These latter may, however, be built on the polygonal ends at the same time as the body. Or, they may be made in the same way and screwed to the ends after the completion of the pattern. The latter method usually makes the lightest job. The core-boxes of a cylinder pattern are usually somewhat intricate. The core for the main body is simply cylindrical like that used for pipes except that in two places a piece is set upon the inner surface of the box. These form indentations or prints in the core itself to receive the cores forming the ports. If desir- able the core may be made of loam. Fig. 92. 56 PATTERN MAKING. The cores of the ports must have a curvature on their cross- section at the points d d, Figs. 93 and 95, to conform to the curve of the cylinder's shell. In order that the shape of the port shall correspond with that called for by the drawing, first make a template to exactly correspond with the full-size drawing of the port as given in Fig. 89 and duplicated on the chalk board. a b r i r ^y /; ro iiL 8 Fig. 93. *b^ "TTl — * ! C -a Fig 94. Fie. 9i Build up a block of which Figs. 93, 94, and 95 are general outlines. In these three figures the same letters refer to the same parts. Square the edge a a and from it lay off the width and length of the port according to the dimensions b and C respectively. On the face d describe the arc of a circle g h from the point e, letting the perpendicular distance / from a to e be equal to the distance from the valve face to the center of the cylinder plus the height of the core-print on Fig. 89. Then with the template of the port for a guide, cut out the material of the block so that it fits accurately along the center line PATTERN MAKING. 57 from the edge a to the curve g h. Take the distance a b on Fig. 89 for a radius and strike an arc whose cord is equal to the length of the port (Fig. 94). With the concave surface of this arc as a template cut away the material of the block to form the bottom of the core as shown by the line i k of Fig. 94. The edges, almd of Fig. 93, bounding the core ends i h should rise the width of the port, away from the bounding line at the bottom as shown by the dotted line p r s. The cover to this core should fit the. faces A and B of Fig. 94 and have the same curvature over the body of the core as i k. The sides of the core where they intersect the valve-seat at a and along the shell of the cylinder at d s are flat. These two parts exceed the length of the cored passages by the length of the prints. One core-box will answer for both steam ports. The core-box for the exhaust passage is a simpler box to make. It is made in halves the face view of each being the same as that of the exhaust passage A, as shown in Fig. 90 and its depth beneath the port is equal to and shaped like the correspond- ing portion A of Fig. 89. Beyond the valve-face the part B is a half-circle in each box. The length of the box exceeds that of the cored portion by the dotted lines indicating the core prints on Fig. 90. Gears. Spur gear patterns may be made in either one of two ways : by a complete pattern or by a segment. Complete patterns are usually made where the gears are not more than 30 inches in diameter and a large number of castings are needed. The propor- tioning and shaping of the tooth will be treated elsewhere in this course. The hub and spokes of gear wheels depend for their size and proportions upon the work which the wheel is to perform. Wheels whose pitch diameter is from 10 to 24 inches should have four arms and for smaller diameters should have a continuous plate or web. A safe rule for the width of the arms at the rim is to make it twice the pitch. The following formula is, however, preferable : B 2 . _ 7-34 X P X W X y/N" A 58 PATTERN MAKING. In which P = the pitch, W = length of the tooth, N = number of pinions to be driven, A = number of arms, B = breadth of arms. The arms should be tapered from the rim to the hub ; the amount being about -| inch to the foot. The rim should be built oip of thin strips carefully fitted and always breaking joints. The teeth may be glued and nailed or dovetailed to the periphery. The for- mer is the cheaper method ; the latter the more durable. In either case the blocks from which the teeth are to be cut are put on in the rough as shown in Figs. 96 and 97. After the glue has thoroughly set, the teeth are laid out and then shaped with a chisel. Where the length of the tooth does not exceed 4 or 5 inches it is best not to allow any draft, or if any is allowed to make it as little as possible, for it is very desirable that the line of the tooth should be at right angles to the plane of the pitch circle. Where there is a draft, that of the gear and the pinion should run in opposite directions so that the teeth may have a proper bearing throughout their whole length when placed on par- allel shafts. These gears are usually in one piece and are moulded like the handwheel, Fig. 58. For large gearing it is customary to make only a short seg- ment containing from three to five teeth, which is swung from a center and successively used in different positions to mould the whole gear as will be explained in the section on Foundry Practice. PATTERN MAKING. 59 Bevel Gearing. To make a bevel gear pattern is much more difficult than that of a spur gear. The hub, spokes, and rim are laid up and made in the same way. In cutting the teeth it must be remembered that all lines marking the contour of the teeth con- verge to a common point, which is the point of intersection of its own shaft and that of its mate. Fig. 98 illustrates the method to be pursued in the laying out and shaping of the teeth. The drawing gives the taper of the crown and root of the teeth along the bound- ing lines towards the vanishing point C. On the face a at right angles to the pitch line a C lay out the face of the larger end of the teeth, and on the corresponding end g lay out the smaller ends. Then work them down to size with an even taper from a to g exactly as in the case of the spur gearing. Worm Gearing. To strike out a worm and its gear. First draw a right angled triangle in which a c (Fig. 99) is the cir- cumference of the worm ; a b the pitch and the angle a c b will represent the inclination of the teeth. The worm pattern should be made first and in two pieces. Lay out the shape of the teeth as in a rack as described in the course of Mechanical Drawing, Lesson 20, Cut a triangle like Fig. 99 out of paper and wrap it about the turned block of the worm. The edge b e will indicate the center line of the tooth. Con- tinue this until the whole length of the worm has been laid out with a continuous helix. Then with a template shaped to fit the spaces between the teeth either work it out by hand, or better still, turn it out on a screw cutting lathe. The wheel may be built up like those of other gears but must be made in halves held together by dowels. Fig. 98. 60 PATTERN MAKING. The most expeditious way to cut the teeth will be to lay them out as they would come from the repetition of the work for a gear in connection with a rack (see Lesson 20, Mechanical Drawing). This shape is laid out on the center face of each half of the pat- tern, and, after roughing them out but not working down to the line, the worm is placed in a lathe and the gear on a shaft. Then the teeth are red-leaded and worked down e until a complete surface contact is obtained. This is a rule-of-thumb but will be found more expeditious than an attempt to make a scientific laying out of the work. Cogging. Gearing with wooden teeth is in common use where it is desired in case of accident that the teeth may break rather than anything more important and where the noise of common gearing is to be avoided. While the placing of new cogs in a gear is not, strictly speaking, pattern work it is usually assigned to the pattern maker. The body of the cogged wheel is of cast iron and the rim is cored out with rectangular holes corresponding in number and approximately in size to the teeth in the completed wheel. It is into these holes that the teeth are inserted. In the selection of the wood for these teeth, only strong, dry, straight-grained hard wood should be used. Maple is probably the best for the purpose. It should, above all things, be dry for if it is damp or contains any sap, it will shrink after it has been put in position and become loose in the casting. The teeth when first inserted are cut with a shank that has a driving fit in the cores of the rim. This shank projects down through the rim for a distance of 1| or 1± inches where one side should be cut away to form a half dovetail and a wedge may be driven tightly between it and the adjoining tooth. This wedge should bear against the shank of the teeth on each side and the inside of the rim. These wedges should not be inserted and Fier. 99. PATTERN MAKING. 61 driven home, one at a time, but should all be put in position and then struck in rotation until all are tight. The wheel should then be allowed to stand in a warm, dry place for a week and the wedges again tightened. The shape of the teeth is laid out on each end of each tooth and the wood worked down to the proper form as directed for the making of spur gearing. Finishing Patterns. A pattern should be made hard and smooth so that it can be easily drawn from the sand. It should be protected by a coating that will not be affected by the moisture contained in the sand. Shellac varnish is a good material for such a coating. In the finishing of a pattern it should first be sandpapered smooth. It is then given one coat of shellac varnish. This will roughen the wood and after the varnish is dry a second sandpaper- ing will be required. Then a second and sometimes a third coat of varnish is laid on, when the pattern will be ready for the foundry. Never put on a coat of shellac until the previous one is perfectly dry and hard. Let the varnish dry slowly in the air and do not hasten it by putting the pattern near a stove or heater. An hour is usually quite sufficient to harden a coat of shellac varnish. Parts where slivers or small pieces have been chipped off may be mended with beeswax. It is best applied with the warm blade of a knife. Hold the blade in an alcohol flame or that of a Bunsen burner for a moment and then cut off a bit of wax which will melt on the blade and may be rubbed into the broken part of the pattern; the process being repeated until the break is filled. Paint and ordinary varnish should not be used on patterns. Files are frequently of service in finishing patterns ; the half- round being a particularly convenient tool. PATTERN MAKING EXAMINATION PAPER American School of Correspondence Copyrighted 1898 BY American School of Correspondence BOSTON, MASS., U. S. A. PATTERN MAKING. Instructions to the Student. Place your name and full address at the head of the paper. Work out in full the examples and problems, showing each step in the work. Mark your answers plainly "Aus." Avoid crowding your work as it leads to errors and shows bad taste. Any cheap, light paper like the sample previously sent you may be used. After completing the work add and sign the following statement. I hereby certify that the above work is entirely my own. (Signed) 1. What woods are most suitable for small patterns? 2. What tools should be used for finishing lathe work? 3. What is the usual allowance for finishing? 4. Why can work be done more rapidly upon a band than upon a jig-saw ? 5. How can a solid pattern be moulded so that it is imbedded in both cope and drag ? 6. Why is it usually necessary to make a pattern in two parts ? 7. What precaution should be taken in the preparation of the wood in making a glue joint ? 8. What should be the outside diameter of the original wooden pattern for a pulley rim, the finished pulley to be 3 feet in diameter : (a) when measured by a common rule ; (ft) when measured by a shrinkage rule ? 9. How are iron patterns usually protected from rust ? 10. Should a gear wheel 16 inches in diameter have spokes or a web to connect the rim and hub ? 11. What are the principal requisites of a material for patterns ? 12. What are the qualifications of a pattern-maker ? 13. What are the two parts of a flask called ? 14. What is a faceplate? 66 PATTERN MAKING. 15. How are the two parts of a round pattern held together for turning ? 16. How can the setting of glue be quickened? 17. What should be the breadth of the outer ends of the spokes of a pulley whose diameter is 2 feet, 6 inches and the width of the rim 8 inches, there being five spokes? Ans. 1.81 inches. Use 1-| inches. 18. In the making of a pattern for an engine cylinder, what is made first? 19. What woods are in most common use for patterns? 20. What is the advantage of a sliding carriage on a turn- ing lathe ? 21. What is the usual allowance for finishing? 22. Why are large patterns not made of a single piece of wood ? 23. How is overheating avoided in the preparation of glue ? 24. What should be the breadth of the outer ends of the spokes of a pulley, whose diameter is 3 feet, the width of the rim 10 inches, there being five spokes? Ans. 2.08 inches or 2 inches. 25. How are engine cylinders made? 26. How should wood be inspected? 27. What will be the linear velocity of the rim of a circular saw 16 inches in diameter when running at a speed of 2,500 revolu- tions per minute. Ans. 10,472 feet per minute. 28. How should a saw table be equipped ? 29. What are dowel pins and what are they for? 30. What is the effect of prematurely chilling the glue after it has been applied to the surface which it is desired to unite ? 31. How are the coreprints of a pattern designated 9 32. To what extent should a pattern maker be a draughts- man? 33. At what speed should the pulleys of a band saw revolve if they are 3 feet in diameter ? Ans. About 370 revolutions per minute. PATTERN MAKING. 67 34. What is the purpose of the allowance for finishing on patterns ? 35. What effect does overheating have upon glue? 36. What is the purpose of a rapping-plate ? 37. Why does wood warp? 38. What is a convenient allowance for draft? 39. What is a two-part pattern ? 40. How many spokes 21 inches wide at the rim should be put into a pulley 4 feet in diameter and having a rim 9 inches wide? Ans. 5.6. Use 6. 41. How should wood be seasoned ? 42. What power-driven tools should be in a pattern shop ? 43. How long a time does glue require to set? 44. How can a pattern that has been slightly damaged be repaired ? 45 . What is the draft of a pattern ? 46. Why are two shrinkages allowed for in the making of a wooden pattern for an iron one ? ' 47. Why is white pine a suitable material for pattern- making? 48. When should cores be used instead of allowing the pat- tern to make its own cores ? 49. How long a time is required to harden a coat of shellac varnish? 50. How is a round core made ? 51. Which will dry the more rapidly, large or small timber and why ? 52. How can the tendency of glued strips to curl be diminished ? 53. What is the use to which cores are put? 54. What should be the breadth of' the arm of a gear wheel whose pitch is 1^ inches, the length of whose tooth is 4 inches, which drives one pinion and has five arms ? Ans. About 2.7 inches. 55. How is shellac varnish prepared? 56. What proportion of glue and water should be used in the preparation of glue ? 57. Are coreboxes needed for columns? 68 PATTERN MAKING. 58. What is the proper way to hold a tool on the grind- stone, when sharpening? 59. Are complete patterns needed for the moulding of gears ? 60. What is the use of cores ? 6.1. What is meant by "allowance for finishing" on a pattern ? LIBRARY OF CONGRESS 003 318 170 ft •