60 



PATTERN MAKING 



will be lifted with it. The pattern is now removed; the bolt-hole 

 cores are placed in position ; and the cope is returned to its place 

 on the drag. 



In this case the core prints should be in length at least twice 

 the thickness of the metal 

 through which the hole is to 

 be cast, and the length of 

 the cores will be equal to the 

 thickness of the metal plus 

 the length of the prints. 



In the small sheave pully, 

 Fig. 121, we have an example 

 of a casting the construction 

 of the pattern for which, so as Fig. 121. 



to make it easily removable from the sand, may give some trouble to 

 the beginner. The pattern is shown in cross-section in Fig. 122, and 

 is moulded in a two-part flask. At first it would seem impossible 

 to place the pattern in the 

 sand so that either half could be 

 removed when the cope and drag 

 are separated on the parting line 



of the pattern. This is readily accomplished, however, as follows: 

 The half pattern C is placed in the inverted drag, with the part- 

 ing downward on the moulding board, and is rammed up in the usual 

 way. After the drag is turned over, the sand is cut away and 





Fig. 123. 



removed to the center of the rim edge, as shown in Fig. 12H. The 

 cut is carefully smoothed, and parting sand applied to the cut 

 surface. The part A of the pattern is placed in position on C, and 

 is rammed up carefully, the sand being then cut away to the center 

 of the rim edge of A. Parting sand is ,-ipplied to the new surface, 

 after which the cope is placed in position and rammed up. 



