86 



PATTERN MAKING 



half , and change 5 until a perfect fit is obtained between the two 

 halves, not only in the central recess and projection, but also in the 

 two curves which form the semicircular groove of the rim. A 

 cross-section of the pattern at this stage of construction is shown 

 in Fig. 164. 



^ 



Fig. 164. 



Fig. 165. 



A disc or chuck of wood 5^ inches in diatneter is now screwed 

 to the iron face-plate, or the screw chuck, and turned off tnie on 

 the face with a projection inch high whicL w:.x fit n^to the recess 

 in the middle of the parting face of a. This projection will center 

 the half pattern a on the face plate, and it can be held in position 

 by two or four short wood screws driven through the web into the 

 wooden chuck as shown in Fig. 165. 



Care must be taken to place the screws in such a position that 

 the screw holes will be cut or bored out when making the four or 



six openings 1 inch in diameter 

 in the finished web of the pulley. 

 The screws must be small and 

 slender and the heads well coun- 

 tersunk out of reach of the turn- 

 ing tools. The face of the half 

 pattern is now turned to the re- 

 quired shape, the template shown 

 at e in Fig. 165, being used for the 

 purpose. Having finished with 

 fine sandpaper, remove the half 

 pattern, and turn off the projec- 

 tion on the center of the wooden chuck; turn a recess instead 1<> re- 

 ceive the projection on Z, and proceed with this second half as with 

 the first. If the wood has been well seasoned, and the work caref ul ly 

 done a perfect 6-inch sheave pulley pattern will be obtained, such 

 as is shov/n in Fig. 159. 



Fig. 166a. 



