442 APPLIED SCIENCE 



sawing weakens the pattern. The joints of the different 

 layers or courses of segments should be so arranged that the 

 segments of one course will tie together those of the course 

 immediately below it. 



510. Arrangements of Parts. In building up patterns, 

 the wood should be so arranged that its tendency to warp is 

 opposed in the different layers. This prevents the whole 

 mass from warping in one direction. Also it is not wise to 

 arrange one layer with the grain running across the grain of 

 the other layers, as is done in cabinet-making. A pattern 

 is used roughly and is exposed to the dampness of the mold- 

 ing sand. If two layers have the grain running lengthwise 

 and one layer crosswise, the two layers will swell in one 

 direction and the one in another at right angles to it. This 

 swelling practically ruins the pattern for the molder, as 

 the outside layers project beyond the middle layer on each 

 side, while the middle layer projects at each end. Not only 

 is the pattern distorted, but in many cases the drawing of 

 the casting is made impossible. 



511. The Pouring of Metal into Mold. All molten 

 metal when solidifying forms into crystals in lines at right 

 angles to the surface from which the heat is given off. This 

 tendency has no ill effect on a square, round, or flat surface 

 or object, but when a projection or corner is formed on some 

 casting it may lead to serious defects, especially if the corner 

 be particularly square or sharp. To prevent this defect, 

 it is customary to use round corners, called "fillets. " These 

 "fillets" may be of wood, leather, or wax. Sometimes they 

 are worked solid out of the material of the pattern, and at 

 Other times they are glued or melted in ? The "fillet" also 



