PATTERN MAKING 



107 



before they are glued in position. When this is done, all angles 

 formed by the rim, ribs and 1mb with each other should be care- 

 fully rilleted. 



After the fillets are in position, it remains to provide for the 

 coring of the holes. This is done by first laying out upon the face 

 of the pattern the location and size of the holes. It is upon the 

 points thus located that the core prints are placed. Before this is 

 done it must be decided which side of the casting is to be made 

 uppermost. 



Where a large, flat surface is to be given a finish, it is desirable 

 that the metal should be as clean and free from sand and blowholes 

 as possible. As the iron has a greater specific gravity than the 

 sand of the mould, all particles of sand that may be washed away 

 and all gases generated, rise to the surface of the molten metal. 

 Those imprisoned by the cooling of the iron form the dirt and 

 blow r holes that disfigure the completed casting. In a casting such 

 as the face-plate under consideration, it is desirable, then, that the 

 face should be upon the lower side when the metal is poured. For 

 the sake of convenience in setting the cores, the prints are put 

 upon the face and make their impress in the sand of the drag. 

 They should be glued and nailed in position after the pattern itself 

 has been sand-papered. The core prints for the hole through the 

 center are also put on in the same way. 



PIPE CONNECTIONS. 



Many patterns which at first may seem to be quite formidable, 

 will, after a little study, resolve them- 

 selves into a few very simple parts, nearly 

 all the work for which may be done in 

 the lathe. Of this the tee pipe connec- 

 tion shown in Fig. 184, is a good illus- 

 tration. 



A sectional view of the casting, 

 threaded and having a pipe screwed into 

 the right-hand end, is shown in Fig. 185. 



The completed pattern for this casting is illustrated in Fig. 

 186, with its core prints a, a and a, and must be parted as shown 

 in Fig. 187. The entire pattern may be made at a single turning 



