M 



PATTERN M AKIN (I 



The groove is a semicircle 1 inch wide, and the rim containing 

 the groove is connected with the hub by a solid web \ inch in 

 thickness, and having four or six holes, each 1 inch in diameter, 

 this web taking the place of arms. If then; is to be no finish on 

 the sheave, as is usual, the only allowance to be made on the pat- 

 tern, which must be parted, will be for shrinkage and for draft. 



A cross-section through the finished pattern for this casting is 

 shown in Fig. 159. 



In all large patterns of this kind, the web is first glued up 



Fig. 159. 



in sectors, six, eight or more in number, according to the size of 

 the sheave (see Fig. 160). The sectors are fitted by hand or on the 

 trimmer, the ends are glue-sized, and when the sizing is dry the 

 joints are carefully scraped smooth, and the whole glued together. 

 After drying for four or five hours, it is sawed to a circle of J-mch 

 greater diameter than the finished pattern, and the block for the 



Fig. 160. 



Fig. 161. 



hub is glued over the center. Six segments to form the outer rim 

 are glued around on the outer edge, care being taken to break joints 

 as shown in Fig. 161. If the groove is to be large, the six segments 

 should be of half the thickness only, and a second set of segments 

 of like thickness glued over the first, breaking joints not only with 

 the first set, but also with sectors of the web. 



In other words, in all glued -up rims, no two joints should be 

 directly over each other. All joints must be so broken and so dis- 



