The art of pattern-making
Chase, I. McKim (Isaac McKim), 1837-1903
?'^s?^^3Kr^-'t':>'y!',-'»' <r-,'-'' t-"^! M^ ".•■ ^Ai '■IK*'-'; ,'. •V - < '♦-, ■■:;< ?v, . r^% '^ v^,r.fi>^3riSrn 5^v *'^^^i^!11?^^^ r*:^ ^ OANNQT LEAVE THE LIBRARY. Chap. ZX^.^Xl^-O Shelf. lC^.^T. C, i COPYRIGHT DEPOSIT. ^ 1^^ LIBRARY OF CONGRESS, ml ^^^^^^■s? ^. .•A; "'■; 'vl 7 )V' /i^^^3i^ 0-. ^ r^' J^rjf^j .'>/ K* / ?rA: ^a- .c< ,/^' i2 0 WORKS OF I. McKIM CHASE PUBLISHED BY JOHN WILEY & SONS. Screw Propellers and Marine Propulsion. 8vo, X -f- 230 pages, 31 full-page plates. Cloth, $3.00. The Art of Pattern-making. A Comprehensive Treatise. Numerous Examples of all kinds of Pattern Work for Green-sand, Dry-sand, and Loam Moulding. Pattern Work for Marine En- gines and Screw Propellers. Also Useful Inforii a- tion and Rules for the Practical Use of Pattern-makers and Others. lamo, vi -|- 254 pages, 215 figures. Cloth, I2 50. THE ART OF PATTERN-MAKING. A COMPREHENSIVE TREATISE, NUMEROUS EXAMPLES OF ALL KINDS OF PATTERN WORK FOR GREEN-SAND, DRY-SAND, AND LOAM MOULDING. PATTERN WORK FOR MARINE ENGINES AND SCREW PROPELLERS. ALSO USEFUL INFOR- MATION AND RULES FOR THE PRACTI- CAL USE OF PATTERN-MAKERS AND OTHERS. BY I. McKIM CHASE, M.E. FIRST EDITION, FIRST THOUSAND. NEW YORK: JOHN Wn.EY & SONS. London : CHAPMAN & HALL, Limited. 1903- THE LfBRARYOF CONGRESS. Two Copies Received JUL 28 '00? copyright Entry kSsO ^ XXo No. ic U- 0 ^ o COPY A. T Copyright, 1903, BY JOHN WILEY & SONS. fcCC , c t ROBERT DRUMMOND, PRINTER, NEW YORK. 3 f/i^l PREFACE. The author's extensive experience in connection with pattern-making in nearly all of its variations impressed him with the belief that great benefit would be derived by many members of the craft by acquiring a more general knowledge of the busi- ness. No individual can have had the experience of many. The acquisition, then, of the knowledge of others must be gained through lectures or litera- ture. The literature pertaining to pattern-making is by no means as extensive as the importance of the business warrants. There are many pattern-makers competent to treat the subject in a satisfactory manner, but have been deterred by the amount of time and labor necessary to do the subject justice. The subjects chosen for illustration herein are chiefly those with which the author has had per- sonal experience and were originally written for publication in "Machinery." He also records the experience of others in pattern -making ; these ex- amples have been selected chiefly from the corre- spondence of the ''American Machinist." He has iii IV PREFACE. embodied whatever in his opinion would be of interest to the pattern-making fraternity. Providing for the interior of castings, or core-box work, is correctly regarded as the most intricate and important part of pattern-making. Amongst the subjects several excellent examples of core-box work will be found. Screw propellers are a special feature, and the examples given are thoroughly elucidated. The author has always entertained a deep interest in pattern -making owing to its intricacy, the skill and intelligence required for its execution. In present- ing this volume to its readers he hopes and believes it will be found a useful and desirable acquisition to the literature of pattern-making. CONTENTS. PAGE I. Introduction ^ II. Equipment of a Modern Pattern-shop 13 III. The Management of a Modern Pattern-shop 24 IV, Pattern Work for Moulding in Loam 34 V. Pattern Work for a Cylinder 39 VI. Pattern Work for an Elbow 44 VII. Pattern Work for Steam-cylinder of Marine Engine 49 VIII. Pattern Work for a Pedestal 5^ IX. Pattern Work for Screw Propellers when Swept Up in Loam « ^i X. Pattern Work for Rifle-projectiles 74 XI. Pattern for Launch-engine 7^ XII. Patterns of Deck-lug for Dry-sand Moulding 83 XIII. Pattern Work for Water-collar 88 XIV. Pattern Work for High- pressure Cylinder for Marine Engine 93 XV. Pattern for a Gun-mount Pedestal 100 XVI. Pattern Work for Screw Propeller Cast Entire 104 XVII. Method of Making a Pattern for a Screw Propeller with Separable Blades "2 XVni. Construction of Small Screw Propellers 123 XIX. Pattern Work for Moulding a Large Belt-pulley or Fly- wheel \ ^32 XX. Pattern for an Oblique Chute 137 XXI. Patterns with Branches 1 43 XXII. Teeth of Gear-wheel Patterns • • I55 XXIII. Belt-pulleys and Fly-wheels - 160 XXIV. Standard Patterns ^^ V VI CONTENTS. PAGE XXV. Glue and its Use i68 XXVI. Loose Pieces 170 XXVII. Wood Lagging for an Elbow 171 XXVIII. The Lathe and Lathe-work 175 XXIX. How to Make a Wooden Face-plate 182 XXX. Marking, Recording, and Storing Patterns 184 XXXI. Sectignal Lining in Mechanical Drawings 190 XXXII. Practical Geometry 192 XXXIII. Some Useful Rules for the Shop 200 XXXIV. Handy Tools for Pattern-makers 212 XXXV. Method of Making Special Shrinkage Rules 216 XXXVI. A Handy Straight edge for Marking 218 XXXVII. Filing Hand-saws 219 XXXVIII. Wax Fillets 222 XXXIX. Inserting Wood-screws into End Grains of Wood 224 XL. Board Measure 226 XLI. To Compute Volume of Squared Timber 227 XLII. Timber Measure 228 XLIII. Strength and Weight of Woods 229 XLIV. Miscellaneous Tables, etc 230 XLV. Standard Wood-screws 234 XLVI. How to Approximate the Weight of an Iron Casting from its Observation 236 XLVII. Prismoidal Formula 241 XLVIII. To Compute the Area of a Figure Bounded by a Curve . 245 XLIX. Weights and Measures 248 THE ART OF PATTERN-MAKING. I. INTRODUCTION. The art of pattern-making comprises the model- ing of objects that are intended to be cast of metals. Its origin is contemporaneous with that of the cast- ing of bronze, and, like that of the latter, the period of its inception is lost in the oblivion of remote ages. The first patterns were probably made of clay or of similar material, and were models of those rude bronze castings that have been found in ancient ruins. At a later period wax was employed for patterns which represented the more artistic bronze articles. In both these methods the models were usually destroyed in the process of moulding, and their consequent disappearance, in conjunction with the then existent limited knowledge of bronze found- ing, made the castings rare and valuable. In the ancient wax process the modeling was done directly in the wax. When the object was large a core representing the interior form of the 2 THE ART OF PATTERN-MAKING. object was made of the same materials that formed the mould. Over this the wax was modeled and the mould was built around the model or pattern thus formed. In building the mould, inlets or gates through which the metal entered, and vents through which the gases escaped from the mould, were pro- vided; these were also represented in wax. When the mould was heated in the process of baking, the wax melted and escaped through outlets provided for the purpose during the construction of the mould. Wax is still used for patterns, although chiefly for ornamental work. In the modem process the modeling is done in clay, and a plaster mould made of the object thus modeled. The wax model is then produced by filling the plaster mould with molten wax. Plaster patterns are also used to a large extent in ornamental work. The process of producing them is similar to that of making wax patterns. For many kinds of patterns plaster is a convenient material. It will readily take impressions with fidelity, its durability is such that it will withstand repeated use, and it is sufficiently cohesive to allow of a pattern being made in sections for convenience in moulding. As the various arts requiring castings advanced and demanded larger and more complicated cast- ings, the art of founding progressed with it. To meet this created demand it became necessary to produce larger and more complicated as well as more durable patterns. INTRODUCTION. 3 Wood, then, of all materials, has been found to possess the qualities which are requisite in the con- struction of large and intricate patterns at moderate expense. Of the various kinds of wood suitable for pattern work, clear, dry white pine stands pre- eminent. Its abundance and cheapness, the ease with which it can be worked, combined with its constancy in retaining its form, has induced its employment for pattern work to a greater extent than all other materials combined. The kind of pine that grows in the neighborhood of the Great Lakes is the best. It is better without knots or sap, although a small knot or a little sap occasion- ally is not objectionable, especially for large pat- terns, provided the wood is thoroughly seasoned and dry, for this latter quality is of the first importance. The shrinkage of white pine across the grain is well understood. It has been asserted that it will also shrink with the grain lengthwise, and under certain conditions this is possible to a small extent when the wood is of curly or cross-grained nature. A case of apparent shrinkage in length of white pine was related to the writer by a reliable person. In making a pattern he joined together two pieces of white pine and then planed off their ends, thus insuring their being of the same length. Subse- quently, after the pattern had been used for mould- ing and had been stored in the pattern loft for some time, it was noticed that the two pieces were of imequal lengths. From the nature of the construc- tion of the pattern and the position of the two pieces 4 THE ART OF PATTERN-MAKING. in it, the opinion was formed that the shorter piece had shrunk in length. The resistance that soft, white pine offers to compression is not very great. If a piece of this wood, of cross-section small in comparison to its length, is left standing on end a sufficient space of time, it is possible for it to de- crease in length owing to its small power of withstand- ing compression, and thus create the belief that shrinkage was the cause of the change. For all practical purposes it may be said that soft, straight- grained white pine will not change its length by shrinkage. When patterns are to be subjected to rough usage, or are to be used for many castings, harder woods, such as baywood, cherry, ash, maple, etc., are selected. The first-named of these possesses some of the qualities of white pine, in that it is easily worked and will hold its shape well; but it is the most expensive of the woods used. Of late years redwood has been largely employed in mak- ing patterns, but, although somewhat cheaper, it does not work as freely as white pine. Except for large and plain patterns, where the cost of material amounts to a large proportion of the entire expense of construction, the use of redwood for pattern work is of doubtful economy. Metal patterns are also largely employed, but of course the original must have been made of wood or other material, and the metal pattern produced by process of founding. Green-sand moulding is practiced to a greater INTRODUCTION. 5 extent than other methods, because it is the cheap- est for producing castings, especially for small work that is to be much duplicated. In .this the mould- ing is done in a suitable sand, moistened sufficiently to make it adhere together. Patterns for green- sand moulding are models of the object to be cast, and are made in such a manner that they may be readily withdrawn from the sand without mutilating the mould. To enable this to be accomplished the pattern is made in two or more sections, as the case necessitates, and so joined together as to allow the different parts to be withdrawn separately and in a manner depending on the form and position of the part. Core-prints are provided where necessary to locate and support the cores. Cores are bodies of prepared sand, baked. Their exterior form cor- responds to an interior part of a casting, or to under- cuts on its exterior that will prevent a model of it being withdrawn from the sand. In such a case the pattern is provided with core-prints which abolish the imdercuts and leave impressions into which cores are inserted to supply the part or parts of the mould made vacant by the core-prints. Dry-sand moulding is next in importance. In this method the moulding is done in sand mixed with raaterials that will cause it, after being baked in an oven, to adhere firmly together and withstand greater pressure without distortion than with green sand. Another advantage the dry-sand method possesses is that the mould may be "cheeked," as foundrymen say; that is, it may be divided into 6 THE yiRT OF PATTERN-MAKING. a number of parts and those parts lifted away to relieve undercuts and similar places in the patterns. Statuary is moulded in this manner. Patterns for dry-sand moulding are constructed and finished in a similar manner to those for green sand, except that they can often be made with fewer pieces when the mould is to be " cheeked ' ' and drawbacks employed. Loam moulding is used for the larger and heavier castings. In this method the moulding is not done in a flask, as in the case of the two previously de- scribed methods, but is built up of brickwork, strengthened by rods and plates where necessary. The moulding material is a mixture of sand and other materials of about the consistency of mortar. It is worked into the mould between the pattern and brickwork. By this method the mould can be made into any number of necessary sections, which can be disjointed, thus relieving the pattern and allowing its withdrawal. When the sections are assembled in a pit and clamped together with sand firmly rammed around the mould the latter is prepared for the metal. In constructing a pattern to be moulded in loam it is advisable to use wood sparingly, and where it is used provision should be made for its swelling, which it will do by absorbing moisture from the loam. A strike or sweep used in loam moulding is a flat piece of board with the edge so shaped as to conform to the profile of a part of the desired casting by revolving it on a spindle or moving it INTRODUCTION. 7 along guides, as the case requires. The required part of the mould can be formed without necessitat- ing the pattern being worked out for it. A pattern to be moulded in loam is often but a skeleton of woodwork, some parts of it representing corre- sponding parts of the intended casting and other parts forming guides for sweeps. For instance, the mould for a plain cylinder may be formed alto- gether with sweeps by securing them to a spindle and revolving them while building up the mould. Wooden patterns are usually finished with a coating of shellac dissolved in alcohol. This method is quick, furnishing a smooth surface, and provides protection against dampness when the pattern does not remain in the mould very long, as generally is the case with green-sand moulding. But when the pattern reraains in the mould for a length of time, especially in a loam mould, which is very wet, shellac does not afford a very good protection against the absorption of moisture by the pattern, and swelling is then the result. Painting the pattern is the alternative in this case, but it is seldom prac- ticed in this country, in consequence of its incon- venience. Thoroughly oiling the pattern previously to its being placed in a loam mould is the usual practice. All metals in passing from the liquid to the solid state suffer expansion when in the plastic condi- tion. It is this feature in the transition that en- ables metals to take and retain the impressions of moulds with such fidelity. In cooling from the 8 THE ART OF PATTERN-MAKING. plastic condition to the solid state metals contract; the amount of this contraction to normal tempera- ture will vary for the various kinds of metals. Patterns have therefore to be made larger than the intended casting by this amount, and here occurs the necessity on the part of the pattern-maker for the use of discreet judgment based upon extended experience in order to obtain the best possible results, because different kinds of varying mixtures of iron as well as that of alloys will contract with varying amounts. Moreover, the varying propor- tions of castings when made of the same material will vary in their amount of contraction. Thus an extended and plain casting will contract differently from one of more compact form, though both may be of equal weight and cast at the same time and of the same material. It is necessary also to make an allowance for the parts of a casting that are to be finished, taking into consideration the liability of imperfection in the form of the casting. All woods contain moisture to some extent. Wood kept for several years in a dry place will contain 15 or 20 per cent, of water. Wood that has been thoroughly kiln-dried will, when exposed to the air under ordinary circumstances, absorb 5 per cent, of moisture in the first three days, and will continue to absorb until it approximates 15 per cent, of water. Wood, however dry, is subject to change; it will swell or shrink according to the humidity of the atmosphere or the hygrometric conditions under which it is placed. These circumstances INTRODUCTION. 9 must be taken into consideration when a pattern is about to be constructed, and the material so manipu- lated that its swelling and shrinking will counteract each other in order that the pattern may retain its form and dimensions as nearly as possible. There is another peculiarity of wood — its ten- dency to warp in one direction, the cause of which needs to be considered when a structure is to be built up with pieces of wood of various shapes and dimen- sions. When a tree is sawn across it is observed appar- ently to be made up of a number of annular rings. One ring is reckoned for each year in the age of the tree. These rings are composed of numerous minute tubes known as capillary tubes. The sap which gives life and growth to the tree is absorbed by its roots from the soil through which they run. This sap is conveyed through the capillary tubes or veins of the tree by a mysterious force known as capillary attraction. When the capillary tubes are deprived of moisture they contract in diameter and consequently the system which they compose becomes smaller. Fig. I illustrates a section of a tree with the capillary tubes somewhat exaggerated. If such a piece is cut at a season of the year when the tubes contain sap, it will split in the course of drying, as shown by Fig. 2, because the outside tubes dry out first and in shrinking the tenacity of the wood is not sufficient to overcome the resistance to compression offered by the wood within, which has not shrunk lo THE ART OF PATTERN-MAKINC. SO much, and consequently as the shrinkage occurs with great force the outer wood is pulled apart. To prevent this tendency to split, a hole is often bored through the center with the grain; this enables the Fig. 1. Fig. 2. wood to dry and shrink from the inside as well as from the periphery. Fig. 3 shows the section cut with the grain into three parts, and Fig. 4 shows it cut into six parts ; they also show the direction in Fig. Fig. 4. which the shrinkage and warping occur. A knowl- edge of this tendency of wood to shrink and warp in INTRODUCTION. ii drying is important to possess, and a proper regard for it in joining woodwork will avoid many difficul- ties. Pattern-making is of infinite variety, and the pattern-maker is never done learning. New forms and devices are continually appearing ; these necessi- tate constant study and scheming on the part of the pattem-rriaker to meet the new conditions. An extended range of thought, skill, and experience is necessary for efficient pattern-making. A model of an object is not necessarily a pattern, because it may be made in such a manner that it will be im- practicable to mould it. To become an expert pattern-maker necessitates talents superior to those required for any of the branches of the machine business except designing. The pattern-maker should possess the qualifications of a moulder and also a draftsman, and must be able to read any mechanical drawing readily and conceive the form and intention of the object illustrated by the draftsman, and comprehend its details in the mi- nutest degree. He must be able to determine how and in what manner the object is to be moulded be- fore he can intelligently begin the construction of the pattern, and avoid the errors likely to occur by his inability to do so. Expert pattern-makers are classed with the best general mechanics. It is a mistaken opinion of some persons that any mechanic working in the trades where the chief material used is wood can work at pattern-making. The pattern-maker is trained to the greatest refine- 12 THE ART OF PATTERN-MAKING, ment in the art of working wood. There are few employments which require greater speciaHzed knowledge of rather a wide range than that of pattern-making. Good carpenters and cabinet-makers can become pattern-makers after the necessary training, their degree of success as pattern-makers depending in a great measure on how great an impression the habits acquired in their respective trades have made upon them. II. EQUIPMENT OF A MODERN PATTERN-SHOP. The most advantageous arrangement that can be given a modem pattern-shop depends upon the floor- plan. Assuming that the room is rectangular, of ample dimensions, and is sufficiently lighted on the sides, the most convenient disposition is to place the work- benches along one side and the machines along the other. By this arrangement the dust and shavings can be kept under better control and the trans- mission of the power to the machines facilitated. Where the dimensions of the floor are about equal lengthwise and across, and there is sufficient room for the benches along both sides, it is advisable to place the machines in the middle or at one end of the workshop. A room in which to keep the various articles used about the shop by the workmen and belonging to the works, such as hand-screws, clamps, and other tools, should be partitioned off. It should be the duty of the sweeper to see that these articles, when not in use, are kept in a place provided for them. Stands or shelves should be erected at each lathe, and the various attachments, such as chucks, cen- ters, etc., kept upon them when not in use. Simi- 13 14 THE ART OF PATTERN-MAKING, lar fixtures should also be provided, where neces- sary, for the other machines. The line shaft should run from 250 to 300 revolu- tions per minute. All wood-working machines require high speeds. With a moderately high speed to begin with, the necessary speed of the ma- chines can be transmitted from the line shaft to better advantage than when a lowerer speed of the shaft prevails. Wood-turning lathes are indispensable in a pat- tern-shop, and there should be several of them, their number depending on the number of workmen employed. In a shop having a force of forty pattern-makers at least four lathes are necessary. One of these should be a face-lathe for large diame- ters, ten feet or thereabouts. Another should be a combined face and tailstock lathe, having an ovei*- hanging face-plate capable of swinging pieces of about six feet in diameter, and a capacity of two feet in diameter between the centers. The others should be ordinary wood-turning lathes of smaller capacity, one of which should be suitable for the smallest work. Wooden cones are preferable for wood-turning lathes, and they should be carefully balanced. The speed for wood-turning may vary from 1200 to 2500 feet per minute, according to the nature of the work. In a shop of the foregoing capacity two circular- saw machines are necessary, both of which should be provided with an iron table and an arrangement by which the vertical height of the saw may be EQUIPMENT OF A MODERN PATTERN-SHOP. 15 adjusted. One of these should be capable of receiv- ing a saw 28 inches in diameter, and the other a saw 14 inches in diaraeter. The smaller machines should combine both cross-cut and rip saws, and be so arranged that they can be made to ''wabble" for rabbeting. The usefulness of the machines depends largely on the condition in which they are kept. An excellent system is to have the teeth of circular saws shaped as in Fig. 5, and do all the filing on their front or cut- ting sides, the backs of the teeth being spiral curves. By this method, when the teeth are all filed equally on their fronts, the saw will be reduced uniformly in diameter, the amount of reduction depending on the spirality of the backs of the teeth and the extent of the filing. To gum such a saw, a rotary or milling tool should be used. There are various neat little machines of this kind on the market, using mills of various sizes which can be clamped on the saw and the mill re- volved by means of a crank, while it is fed to the tooth automatically. The mills make a rounded throat, which should extend slightly under the face of the teeth, so that in filing it will be unnecessary to extend the filing to the throat. This method requires but little filing to keep the saw sharp. If the saw is of sufficient size to admit of the employ- ment of a swage for the setting of the teeth, this method should be adopted, as with it better results can be obtained from the saw than by bending the points of adjacent teeth in opposite directions. An i6 THE ART OF PATTERN-MAKING. excellent swaging-tool is on the market with which the swaging is done by a cam operated with a lever. The style of tooth here commended is shown at Fig. 5. Fig. 5. The bearings for the arbor of circular saws should be of ample length and babbitted. They require careful attention, and should be taken apart and cleaned periodically, as it is practically impossible to prevent dust working into them. Circular saws give good results when running at speeds of from 8000 to 10,000 feet per minute. Circular saws are usually belted so that the revolu- tions of the arbor cannot be varied. In course of time saws become worn until their diameters are reduced considerably from their original dimen- sions; consequently there may be several saws of different diameters used on the same arbor, and of course their speeds will vary in proportion to their EQUIPMENT OF A MODERN PATTERN-SHOP. 17 diameters. These conditions are met and the best results obtained from the machine by driving the arbor to the hmit of speed for the largest diameter of saw to be used; that is, at about 10,000 feet per minute for the periphery of the teeth. A handy device for use when dressing saws is shown in Fig. 5. It consists of a T frame with the horizontal bar secured to a bench. The upright has a slot for the vertical adjustment of the saw. To the right is a swage, whose pivot can be adjusted on the horizontal bar; to the left is a small vise, 7, to receive one tooth of a saw. This vise is adjustable on the horizontal bar, to which it can be clamped by a thumb-screw. By gluing a piece of paper around the end of the file and keeping it bearing on the shelf while filing, all the teeth can be filed alike without difficulty. The next most important tool for a pattern-shop is the band-saw machine. In a shop of the before- mentioned capacity there should be at least two of these, one to carry saws up to ij inches wide, and the other to carry saws up to one inch. One great disadvantage in the use of these machines is the want of stiffness in the frames. There are but few made which are not deficient in this respect. Band-saws give good results when run at a speed of 3500 to 4000 feet per minute. These machines are usually provided with breaks for the stoppage of the saw, and should always be so arranged that a pressure on a pulley beyond a certain fixed limit cannot be produced by them. If they are not so 1 8 THE ART OF PATTERN-MAKING. provided and the saw is stopped very suddenly, it is likely to break in consequence of the strain thus created. A great drawback to the use of these machines is the cost of the saws, which consequently break. That a band-saw will give way in the course of time is inevitable. Every time that a saw passes over the wheels while running, it bends and straight- ens again. This fatigues the material, and with continued running it is distressed beyond ultimate endurance, just as any similar piece of metal would be broken by being bent back and forth a sufficient number of times. The breakage of saws may be reduced by careful attention to their condition and that of the ma- chine. In joining them they should be scarfed and lapped two teeth and brazed with silver solder. Immediately the tongs are removed from the joint, a few drops of oil should be dropped on the saw by the side of the lap. If not so treated, the saw is likely to become too soft on either side of the joint and will break there earlier than at any other part. Band-saws should always be kept sharp and have a proper set to the teeth, and the wooden jaws on the guide-bar of the machine should be kept set up close to the saw. The mouth-block in the table also requires frequent attention, as the deflection of the saws, especially the smaller ones, cuts them away. An excellent little machine for sharpening and setting band-saws is to be found on the market. It can be secured to a post and occupies little room. EQUIPMENT OF A MODERN PATTERN-SHOP. 19 Being driven by power, a saw can be put in, the machine set going and allowed to run without fur- ther attention until the saw is finished. Another important machine in the pattern-shop is a hand-planer. There should be two of these machines, one with 16-inch knives, to be kept for rough work, the other with 24-inch knives, to be reserved exclusively for the cleaner and finer class of work, because, if allowed to be used indiscrim- inately, the latter will seldom be in the condition essential for the kind of work required of it and for which the machine is specially adapted. The back table of a hand-planer should be provided with a locking arrangement, in order that its posi- tion cannot be changed after having been adjusted to the knives. The speed recommended for hand-planers is 4000 feet per minute, but they will work satisfac- torily between that speed and 3500. A surface or cylinder planer is also a useful ma- chine in a pattern-shop. An improved machine of this kind does not require a great amount of atten- tion; it suffices to have the knives kept in proper condition and the bearings inspected occasionally, to see that the oil is properly performing its functions. The speed is the same as for the hand-planer. When it is difficult to obtain 4000 feet per minute, a speed between that and 3500 feet will give satis- faction. A Daniels planer is very useful in a pattern-shop. It is simple, effective and durable, requiring but 20 THE ART OF PATTERN-MAKING. little instruction regarding its care and use. With this planer the lumber can be planed out of wind, which cannot be done with a cylinder planer, although the work is not so rapidly done as with the latter. The cutters of a Daniels planer should run at a high rate of speed, say from 10,000 to 1 1,000 feet per minute. The style of cutters recommended for a Daniels planer are shaped like the letter J, the cut- ting edge being on the side. A jig-saw is required in a pattern-shop for inside sawing. The band-saw, which has supplanted it for outside sawing, is not adapted for positions bounded entirely by the material. An advisable speed for this machine is from 500 to 1000 strokes per minute, according to the char- acter of the machine. A vertical boring-machine is also useful in a pattern-shop. One having a capacity for boring holes up to 2 inches in diameter is preferable, and should be arranged with two speeds, one to produce 850 or 900 revolutions of spindle, for bits more than i\ inches in diameter, the other 1200 or 1300 revo- lutions, for smaller bits. A core-box machine is another very useful ma- chine in a pattern-shop. A machine of this kind is on the market, on which core-boxes of any length and from f to 20 inches in diameter can be worked. Staves and similar pieces can also be worked accurately and rapidly on their hollow sides by this machine. EQUIPMENT OF A MODERN PATTERN-SHOP. 21 Among the minor power machines that a pattern- shop should have are a grinder for planer-knives, a wet emery -grinder for bench-tools, and two grind- stones, one of the latter being corrugated for the convenience of grinding inside bevel gouges. Trimmers are indispensable in a modem pattern- shop. It is advisable to have at least two of the largest size for the general use of the shop, and several of smaller size, one being located convenient to each two benches. There are several other necessary adjuncts to the complete equipment of a pattern-shop, but these are so well known that description of them is here unnecessary. The bearings of wood-working machinery require very careful attention, in consequence of the high speed at which it revolves and their liability to the deteriorating effects of dust. Bearings should always be provided with tallow-boxes, which should be kept filled with tallow or, better, with Albany grease. A small hole should be made through the grease near each end of the bearing, into which a little oil should be dropped before starting the ma- chine ; then, should the oil work off with continuous running, the grease will continue to keep the bear- ing lubricated. The foregoing is noted as to machines necessary for the equipment of an up-to-date pattern-shop, one that should be able to perform with precision, expedition, and economy, as far as facilities are con- cerned, the work required of it. 22 THE ART OF PATTERN-MAKING. Of course it is possible to get along, in a manner, with less machinery, but such a shop would be at a disadvantage when competing with a better- equipped concern. In many shops a great variety of woodwork is done other than that of pattern-making. In such establishments additional machinery is necessary, the kind and quantity of which will be governed by the nature and extent of the work. The style of work-bench usually furnished pat- tern-makers is the ordinary carpenter's bench, i6 feet long. Pattern-makers seldom have need of a bench more than 12 feet long, and Fig. 6 repre- sents a convenient style. ^<~7y T-^ 4^ ^ |"-.r-vr-vr-vW^^^M-x Fig. 6. The dimensions of a double bench of this kind, well adapted for pattern work, are: 12 feet long, 4 feet wide, and 3 feet high. For a single bench the width should be 3 feet, and the other dimensions the same as for a double bench. Each bench should EQUIPMENT OF A MODERN PATTERN-SHOP. 23 have a shelf about i foot from the floor, extending over the entire space between the legs of the bench. It should also have a drawer for each workman. The framing and the top should be of hard wood about 3 inches thick, except for about 18 inches in the middle of the width of the top; this can be of I -inch pine placed flush with the bottom of the side pieces, forming a recess in the middle of the bench, as illustrated. This recess is convenient for the retention of small tools and articles to be used about the bench. The jaw of the vise is placed horizon- tally, and to it is attached a ratchet bar sliding in bearings under the end of the bench. A pawl is fitted into the bench over the bar by means of which the jaw can be adjusted to suit the work to be clamped. This device is shown in detail, marked a. The vise-screw is of iron, which works more easily than if made of wood. The above arrangement of the vise is more convenient than the ordinary ver- tical position, as this necessitates stooping on the part of the workman in order to attend to the ad- justment ; and rather than do this he will often use the vise in an awkward position, at the risk of result- ing damage. Of late years iron bench- vises are becoming much used and are meeting with justly increasing favor. When sufficient space is available, single benches are preferable. With double benches the space necessary per workman in the length of the bench row is about 5I feet ; with single benches it is about 6 J feet. III. THE MANAGEMENT OF A MODERN PATTERN-SHOP. The qualifications necessary for a foreman to possess in order to successfully manage the affairs of a large pattern-shop are that he should be a draftsman, a good arithmetician, should have a thorough knowledge of the art of moulding, and should be a good judge of human nature as well as of the different materials used in his department. He should be able to decide the manner in which any pattern is to be moulded, and to direct the construction of the pattern accordingly. He should also have a thorough knowledge of the construction and care of wood-working machinery, and not the least of the necessary qualifications are energy, good character, and good habits. By some persons the pattern-shop is considered a drawback to the machine business in consequence of the expense because patterns do not show in a completed structure as other materials do, and are considered unproductive. Yet the pattern-shop is more essential than the drawing department, to which it is closely allied. It is possible to dis- pense with the latter in the machine business, 24 My4NAGEMENT OF A MODERN PATTERN-SHOP. 25 though not with the former where castings are required. But unfavorable criticism of the pattern- shop is frequently the result either of the critic's inexperience in mechanical pursuits, or the assump- tion of knowledge that he does not possess. The person who invents a method of making castings without the aid of patterns has both fame and fortune awaiting him. The expense attendant on the use of patterns is often unnecessarily increased, owing to the abuse which they receive in the foundry. Some mould- ers are veritable pattern-smashers, and will do more damage to a pattern in making a half-dozen castings than others will in making a hundred. Pattern work, like all other kinds of model work, is expensive, and can be made more or less so accord- ing to the work required of the pattern. In this respect patterns may be divided into three classes, and the cost of producing them should be varied accordingly. a. Patterns of a temporary character, those not likely to be used more than once. These should be made with as little expenditure of labor and ma- terial as possible to enable them to perform their functions. These patterns should not be preserved, as they unnecessarily encumber the pattern-loft. h. A class "of patterns likely to be used occasion- ally, sometimes at long intervals. These should be preserved, and more pains be taken in their con- struction than with the former, as they have to withstand the usage in the foundry as well as the 26 THE ART OF PATTERN-MAKING. distortion likely to occur to them during their storage in the pattern -loft. c. A class of patterns regarded as standard and which are frequently used. These cannot be made too well, and when properly constructed are neces- sarily expensive in first cost. When a drawing is received in the pattern-shop the first duty of the foreman in connection there- with is to acquaint himself with it and decide how the pattern is to be made, and in what manner moulded. If detail drawings of a machine or other device to be constructed are received, a general drawing should accompany them, or else the fore- man should be made acquainted with the general arrangement of the parts. When this is done he will often be able to detect errors which might not otherwise be discovered until after the castings have been made and the machining of them is in progress. There are several allowances necessary to be de- termined previous to beginning the construction of a pattern. The one most troublesome to the pattern-maker is that for finishing. The amount that will answer for one machinist will not suit another. It is advisable to leave as little as possible for finishing, and to have sufiicient to allow for the proper finishing of the castings. This allowance will depend a great deal on the result of the casting and its likeness to the pattern. This is likely to vary according to the manner of moulding the pat- tern. As a rule, the castings requiring the greatest amounts for finishing are those which have been MANAGEMENT OF A MODERN PATTERN-SHOP. 27 moulded in loam, and castings made of steel. These are liable to vary from the proper dimen- sions to a greater extent than those moulded by the other methods. Large castings of steel are never as true to pattern as those of other metals. For patterns to be moulded in loam and for steel castings an allowance of from one fourth to one half of an inch, according to the part to be finished, is necessary. For ordinary castings moulded in green or dry sand an allowance of from one eighth to one quarter of an inch is sufficient. For the smaller castings, which have been moulded neatly and are of sound metal, an allowance of from one sixteenth to one eighth of an inch will answer. The allowance for shrinkage, or the amotmt the pattern is required to be made larger than the in- tended casting, is another important preliminary matter to be determined before constructing a pattern. The conventional allowance for iron cast- ings is one eighth of an inch per foot, but this rule needs modification in applying it to castings of various shapes, dimensions, and mixtures of metals. To insure accuracy in castings much depends on the judgment of the pattern-maker in providing for their construction. Hard irons, as gun-iron, will shrink more than the above amotmt, while soft iron will shrink less. Yellow brass will shrink more than bronze. A plain cylinder will shrink less in diameter than in length. With large cylindrical or box-shaped castings 28 THE ART OF PATTERN-MAKING. of iron it is good practice to allow one tenth of an inch per foot for shrinkage in length, and one half of this amount in diameter, or across. The shrinkage in length of such castings is generally very little restricted, while in diameter it is resisted by the cores or internal parts of the mould. Two castings of the same weight and of the same kind of material, one of which is extended and the other more com- pact, will shrink differently, the latter shrinking less than the former. Metals, like water, are densest in their liquid state, the point of greatest density being near the temperature at which they solidify. From this point they will expand either with a reduction or an elevation of temperature. Iron, when about to solidify, undergoes a sudden expansion, owing to the effort of the molecules to arrange themselves in definite positions. After solidification takes place it begins to contract, with a further loss of tem- perature. When the contraction begins, the metal is just leaving its plastic condition, and its cohesive strength is considerably below that of its normal state. If at this period the contraction of the metal is resisted by parts of the mould, a fracture of the metal is likely to occur. With some of the more contracti- ble metals, as with steel, to avoid fractures it be- comes necessary, as soon as the metal has set, to relieve the interior parts of the mould and allow the metal freedom in shrinkage. In the case of a plain cylinder, where its shrinkage is resisted by an internal core, the metal will contract within its MANAGEMENT OF A MODERN PATTERN-SHOP. 29 annular wall until its cohesive strength becomes sufficient to compress the core, at which period it will have undergone part of its contraction. This accounts for the reduced shrinkage of cylinders diametrically. The usual allowances for the shrinkage of castings of different metals are, per foot : For iron one eighth of an inch. " bronze five thirty seconds of an inch, " brass three sixteenths of an inch. " yellow brass seven thirty seconds of an inch. " steel three sixteenths of an inch. " aluminum seven thirty-seconds of an inch. " zinc seven thirty-seconds of an inch. 