88 



PATTERN MAKING 



The rims of such patterns are usually turned in two halves. 

 A wooden chuck, in this case a plain board 12 inches in diameter, 

 and inch to 1 ^ inches in thickness, is screwed to the iron face-plate 

 of the lathe, and turned true on the face and on the edge to 12^ inches 

 in diameter. Ten blocks 2^ inches long, 2 inches wide, and ;| inch 

 in thickness are glued radially at equal distances around the face 

 of the chuck as in Fig. 168. These blocks are turned even with 

 the edge of the chuck, and the faces are also turned off true and 

 straight so as to form a joint with the first row. of rim segments. 



The segments, ten in number, five for each layer, are sawed 

 from a ^-inch board, and should be 2 inches wide. 



Fig. 168. 



Five of these are carefully fitted and glued to the face of the 

 blocks, as shown by the dotted lines in the drawing; and when the 

 glue is dry the chuck is returned to the lathe, and the face of the 

 segments turned flat and true to receive the second row, which is 

 fitted and glued to the first. 



Small hand screws must be used, three on each segment, to 

 press the first layer to the blocks, and again to press the second 

 layer to the first. The joints of the second layer must be over the 

 middle of the alternate blocks from the joints of the first, so as to 

 break joints with the first. When the glue is dry, place the chuck 

 in the lathe, and turn the half rim thus constructed to a true semi- 

 circle with an outside 'diameter of 12^ inches and an inside diameter 

 of 84 inches, using a semicircular template of sheet zinc or copper 

 to test by while turning. 



