PATTERN MAKING 



after being shaped and finished, from the face of each tooth into 

 the rim. 



Patterns for Bevel Gears are built up as illustrated at , 

 Fig. 244, the wooden face-plate, or chuck, being provided with ten 

 or more radial blocks as shown and described in Fig. 168. The 

 advantage of the blocks is that they keep the first layer of segments 

 out from the face-plate and give easier access to the back edge or 

 angle of the rini while being turned. 



The segments are usually made to overlap as shown, which is 

 not only a saving of wood but also saves the time which would be 

 required to turn the angu- 

 lar rim from a square con- 

 struction. When a suffi- 

 cient number of courses 

 have been built up, the face 

 and two edges are turned 

 to the required angles, as 

 indicated by the dotted 

 lines in , Fig. 244. The 

 rib c which will finally be a 

 continuation of the arms, 

 is also turned to shape and 

 to the thickness of the ends 

 of the arms. The rim will 

 then present the appear- 

 ance shown at J, Fig. 244, 

 except the arms which are 

 here shown in place. 



The rim is next cut from the blocks, and an angular groove 

 turned in the face of the chuck which will fit and center the 

 finished edge of the rim on the faceplate. In this position the 

 inside of the rim is turned aud finished as shown in Fig. 245. 

 The rim is retained on the chuck by four or six cleats, '/, 

 Fig. 245, the cleats fitting over the rib c, Fig. 244, and preventing 

 the rim from moving and changing its position on the chuck. 



It is not necessary here to describe tho method used in finding 

 the required angles for the face and edges of tho rim, but as in 

 the case of spur-gear teeth, the student should refer to Mechanical 



Fig. 244. 



Fig. 245. 



