116 



PATTERN MAKING 



When the cylinder is small (ten inches or under in diameter) 

 the pattern is usually built up solid, but if more than ten or twelve 

 inches in diameter it should be built of staves, as shown in Fig. 211. 



Fig. 211. 



When the size is thirty inches or over, a loam mould is usually 

 made as will be fully described in the section on Foundry Work. 

 The size limit, however, varies greatly in different foundries. 



The construction of the pattern is 

 illustrated in Fig. 211, and needs no de- 

 scription here, it being the same as already 

 given for Fig. 207. The flanges, however, 

 should be built up of segments of two or 

 three layers each as shown in Fig. 212. 

 After gluing up to the necessary thickness 

 Fig. 212. to make the flange, it is sawed in two 



halves, jointed and carefully centered on a wooden chuck and 

 turned to the dimensions required. 



9 



Fig. 213. 



The centering must be done with accuracy, or one half of the 

 llangc ring will be larger than the other. The steam chest is next 



