PATTERN MAKING 



45 



use only a plain board % inch to 1^ inches in thickness and of a 

 slightly greater diameter than the required pattern. This board is 

 screwed fast to the iron face-plate as shown in Fig. 89, to which, 

 after being placed in the lathe and turned true, the pattern is 

 attached, as will be fully illustrated and described farther on. For 



Pig. 88. 



patterns of a medium size, say 20 inches to 30 inches in diameter, 

 the board should be stiffened by means of a wide wooden bar firmly 

 screwed across the back, as in Fig. 90, 



When chucks are needed for very large or heavy work, 

 the chuck, in order to prevent 

 vibration, must be strong in 

 proportion. It is best made 

 as illustrated in Fig. 91, in 

 which the front of the chuck, 

 as shown at , will be least 

 affected by the moisture in the 

 air if left unglued, or at best 

 only tongued and grooved, 



being held together by the cross-bars only, as shown at 5, to which 

 it is firmly screwed, without glue. This chuck is simple and cheap, 

 and will be found in practice much stronger and more rigid than 

 one built up out of sectors or in a more elaborate way. 



