62 



PATTERN MAKING 



Fig. 128. 



removed, leaving the parts 5 and c still in their positions in the 



sand, as in Fig. 127. These may now be carefully moved toward 



the center of the opening and lifted out 



In some cases there is 

 not sufficient room, when the 

 main part of the pattern has 

 been taken from the mould, to 

 remove the projecting pieces. 

 In such cases, the overhang- 

 ing pieces or projections must 

 be made by using dry sand 

 cores. To illustrate this, we 

 shall consider the pattern for 

 the small cast-iron turbine 

 case illustrated in Figs. 128 

 1 and 129. A section view of 

 the casting through A B (Fig. 

 129) is given in Fig. 130. 



The pattern is parted on the 

 line C D and will form its own 

 core. The boss , however, 

 will prevent the main part of 



the pattern from being removed from the sand, and if a were made 



loose it could not be taken out through the narrow space made by 



the thin side of the pattern. 



To overcome this difficulty a 



core print is fitted on the side, 



extending from the parting 



line C D to the bottom edge 



of the pattern, as illustrated 



in Figs. 131 and 132; and in 



the impression made by this 



core print a dry sand core. 



formed in the core box shown 



in Fig. 133, is placed. It will 



readily be seen that this core will, in connection with the pattern, 



form a mould which will give the cast ing required. 



Examples in ''Methods of Moulding" could be multiplied 



Fig. 129. 



Fig. 130. 



