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W^oods Used For Foundry Patterns 



Patterns are used in different industries and in ways not at all 

 similar. The shoe last maker employs a pattern to guide the cutting 

 bits of the lathe in giving shape to the last The carver, who em- 

 ploys a machine in doing the work, puts his pattern to pretty much 

 the same service as the last maker, but the machine is quite different. 

 The mechanic often works according to a pattern when he makes 

 an intricate piece of mechanism, though he may have no further use 

 for the pattern than to measure it from time to time and see that he 

 is faithfully copying it. But these are not the patterns which fill 

 so important a place in the foundry. 



The foundry pattern is of the same shape and size as the casting 

 which is to be produced. The pattern is buried in a box of wet sand 

 (called a flask) and the sand is tamped hard around it. By devices 

 specially provided, the pattern is taken out, leaving a hollow mold 

 into which the melted metal is poured, and it hardens in the form 

 desired, which is an exact copy of the pattern. 



Pattern making is as old as metal casting, and that is older than 

 history. The maker of patterns has always held an important place 

 in the industries of the region. He has always been the connecting 

 link between the carpenter and the metal molder. The real artist 

 who made possible some of the fine bronze vessels, stands, and orna- 

 ments of the Romans was the pattern maker, not the metal worker. 

 The form with all its lines of beauty was in the pattern. The 

 foundry man did no more than pour the hot metal into the mold 

 formed around the pattern. The foundry man has been praised dur- 

 ing thousands of years for his skill, and the pattern maker has been 

 wholly overlooked ; yet without his patterns the foundry would 

 produce nothing useful or artistic. 



Woods Fit and Not Fit 



Every wood is not fit for patterns. Some are useless, others valu- 

 able. They must be chosen with care and tried out by experience. 

 If all the woods of the United States were placed on trial, it would 

 be found that ten would be rejected for every one accepted. The 

 line is not drawn between hardwoods and softwoods, or needleleaf 

 and broadleaf trees, or between strong and weak woods. Neither is 

 it necessary to draw the line between woods of rapid or of slow 

 growth. 



Pattern makers classify materials as "drywoods" and "water 

 woods. ' ' That has no reference to their condition of dryness. Trees 

 which grow on high, dry ground are more suitable for patterns than 

 those from low, swampy situations. The latter are known as ' ' water- 

 woods. " They absorb moisture so readily that they are liable to 

 swell in the wet sand and spoil the mold. A ' ' drywood ' ' is less liable 

 to do so, though the best wooden pattern, if left too long in the 

 damp sand, will swell by the absorption of moisture. It is supposed 

 that trees which grow in damp situations are not so compact of 

 structure as those in dry places, and the wood of the former is more 

 porous and will absorb moisture quickly. 



The mere fact, however, that a tree happens to grow in dry soil 

 does not make a good pattern wood of it, unless it is naturally so. 

 Many woods are not good for pattern making, no matter where or 

 how they grow. 



Virtues and Faults of Pine 



White pine is one of the best woods in the world for ordinary 

 foundry patterns, and it might be supposed that all other pines would 

 be somewhat like it, but it is not so. Longleaf pine, short leaf, Nor- 

 way, western yellow pine and northern pitch pine are useless to the 

 pattern maker. These woods are filled with resin which oozes out 

 when the pattern is subjected to the heat and moisture of the 

 foundry. This causes the sand to adhere to the pattern, making it 

 difficult to draw, and the surface becomes too rough for molding the 

 second casting. These woods likewise split easily, are hard to work to 

 a smooth surface and nails are driven into them with difficulty. 



The trouble is due primarily to the resin in the pine. There are 

 several white pines which contain little resin, and they are satis- 

 factory to the pattern maker. Among these are the following: The 

 common northern white pine, Idaho white pine, California sugar pine. 



and limber pine. The first named is the best of these. It checks 

 and warps but slightly, is easily cut, and though good grades are 

 now high in price, it is one of the cheapest pattern woods when the 

 maker's time is taken into account, and the length of service is 

 considered. 



That was the "pumpkin pine'" of early New England times, and 

 the "cork pine" a little later in Pennsylvania, western New York, 

 and Michigan. It was nothing more than large, finely-conditioned 

 white pine, usually more than two hundred years old. It was soft 

 and could be cut across the grain or with it. In fact, it had so little 

 grain that it was said to cut like a pumpkin, hence the name. 



Another and slightly different origin is given for the name. The 

 spheres or baUs used in early New England as ornaments for the 

 tops of flag poles and the prows of boats were called "pumpkins," 

 because of their shape; and since they were nearly always made of 

 the best grade of white pine it came to be known as "pumpkin pine." 

 Some Othee Softwoods 



After the white pine, the spruces stand highest as pattern ma- 

 terial, but they must be carefully assorted. There are hard and soft 

 varieties, and the former must be rejected. The soft kinds contain 

 little resin and are quite satisfactory. Spruce is generally not so 

 free from knots as pine, and has a harsher grain, warps more, and the 

 spruce pattern must be nailed to hold it true. It is said the best 

 spruce for this purpose is the Engelmann of the Rocky Mountain; 

 but when a clear trunk of blue spruce, which grows in the same region, 

 is found on high, dry ground it is equally good. 



Hemlock might be supposed to be worthless for patterns, because 

 it is crofs-grained, brittle, and warps badly; but it is cheap and is 

 useful in building up the frames of large patterns, which are then 

 covered with better material. 



California redwood, Washington cedar, and Port Orford cedar 

 of Oregon, are employed in their respective regions by pattern makers. 

 They are soft, fine-grained, and not inclined to warp. The redwood 

 is rather too soft, as it is easily scarred and dented, yet it will dull 

 tools more speedily than white pine. The southern red or pencil 

 cedar makes fine patterns, except that it is rather too soft. 



Cypress is occasionally worked into patterns, but it is classed with 

 the "waterwoods" and is disposed to absorb moisture from the 

 wet sand; but that tendency is overcome for a time by shellacking 

 the wood. If a limited number of castings are all that are wanted, 

 cypress is fairly satisfactory. 



The maker of patterns holds two chief points in view : The cost of 

 the article and the time it wiU last. It is evident that the amount of 

 service given is the real measure of cost. A five-dollar pattern which 

 is good for only a dozen castings is more expensive than one cost- 

 ing ten dollars and good for a hundred castings. Some of the hard- 

 woods may be used so long that their first cost is a matter of small 

 importance. The list of the hardwoods suitable for this place is not 

 large. The three most common are yellow poplar, cherry and ma- 

 hogany, though others, like ebony, lignum-vits, boxwood, and teak 

 are occasionally used. 



Yellow poplar has a fine texture with a satin lustre. It is straight- 

 grained, tolerably soft, shrinks moderately, is not liable to check, 

 warps but little when thoroughly seasoned, and is not apt to absorb 

 moisture. It quickly dulls the fine-edged tools used by pattern makers. 

 Mahogany 



Mahogany is an excellent pattern wood. It is hard, takes an ex- 

 cellent polish, is not inclined to warp, and it absorbs very little 

 moisture from the wet sand. It is the standard material for pat- 

 terns which are to be used many times, and the first cost is of small 

 importance. The best mahogany for patterns is that cut in Hon- 

 duras, though some is used from other parts of tropical America and 

 also from Africa. Straight-grained wood is wanted. The figured 

 mahogany which is so highly prized for furniture and interior finish 

 is not wanted by the pattern maker. It is too difficult to work to a 

 smooth surface. 



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