87 



The pattern for a sheave pulley has been explained because it 

 embraces so many profitable points and conditions, not only in 

 gluing and building up, but especially in chucking and turning, all 

 of which must be done with great care and accuracy. 



The 1-inch holes in the web are bored out with a 1-inch center 

 lit, which, when well sharpened, will not split or splinter the thin 

 webs xjf the two halves of the pattern, if care is taken to reverse 

 the bore from the opposite BI 



side when the point of the i 



center bit comes through. 

 The holes should be given a 

 slight draft as shown in Fig. 

 159, with a small half-round 



cabinet file. When very large 



Fig. 1666. 



SECTION AT 

 A B 



sheave pulleys, having arms, are to be made, such as are common 

 for power transmission by rope or cable, the patterns are not halved 

 but are made in one piece and the groove is cored around the rim. 

 Such a pattern is illustrated in Fig. 166#, with a wide core print c c 

 extending entirely around the periphery of the pattern. 



A segmental core box is made for one sixth or one eighth the 

 circumference of the wheel, as shown in Fig. 166 5, and here again 



only half of the core box for 

 a full core is needed. When 

 coring the rim as above, the 

 core print must be made wide, 

 at least two to three times the 

 depth of the groove, so that 

 the core may rest firmly and 

 remain in position without 

 tilting w r hile the metal is 

 Fig. 167. being poured into the mould. 



The 12-inch hand wheel, Fig. 167, with five arms and a round 

 rim finished to 1| inches in diameter, will also serve as a good illus- 

 tration of pattern construction. On the rim of the pattern, -fa inch 

 over all its surface must be allowed tor finish, making the diameter 

 of the rim of the pattern 1| inches, and the outside diameter of 

 tha pattern 12^ inches, while the inside diameter of the rim will 

 be-8 inches. 



