CHAPTER XXXVI 

 PATTERNS, CORES, FLASKS, AND MOLDS 



506. Descriptions and Use of Patterns. A pattern is a 

 wooden or metallic model of an article, made to size, from 

 which a mold is formed in sand. Pattern-making is the 

 art of making these wooden models. The cavity correspond- 

 ing to the pattern is subsequently filled with fluid molten 

 metal, which, when it has cooled and become solid, retains 

 the shape of the original pattern. 



507. Method of Making Patterns. The first step in 

 making a large or complicated pattern is to provide a full- 

 sized working drawing for the mechanic. Next comes the 

 selection of the proper wood, which should be of the best 

 grade, close-grained and well seasoned, so as to stand hard 

 usage in the foundry. After the wood is selected it is run 

 through a planer, then cut to size and shape by a hand-, cross- 

 cut-, or rip-saw. If necessary, the lathe is used for turning up 

 the necessary parts. After being cut to approximate shape 

 and size, the different parts are assembled by the use of 

 brads, screws, and glue. The hand-tools now come into 

 use, and the model is made to the exact size and shape desired. 

 It is then sandpapered all over to a finished surface, and the 

 core prints are placed in position. The pattern is next 

 varnished with gum shellac dissolved in alcohol. One coat 

 is applied and smoothed off with a piece of partly used sand- 

 paper, after which two other coats are given to make a hard, 



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