78 



PATTERN MAKING 



being glued, from four to six hours, depending on the temperature 

 of the room in which the gluing is done. Our pattern block is 

 now ready for the lathe and will be as represented in Fig. 153, 

 which is a longitudinal section through the dowel pins. 



When centering for the lathe centers, great care must be lakeu 

 to mark the centers exactly at the intersection of the center-gauge 

 lines on the ends of the blocks and the glued joint of the two 

 pieces. The hard glue will force the lathe center to one side of the 

 connecting joint unless a center dot or hole is first made with an 

 awl in the exact position required. As in the case of the pattern 

 in Fig. 140, the block is roughly turned to dimensions, all of which 

 are a little larger than the finished pattern, by using the ordinary 

 turners' gouges, but the final turning and finishing to exact si/es 

 must in all cases be made with scraping tools, as described for the 

 pattern of the 'brass Crushing. 



When marking off the pattern on the rounded cylinder in the 

 lathe, care must be taken to locate the pattern in the exact center 

 of the block, so that the dowel pins may be equally distant from 



each end and from the center of the 

 pattern. Fig. 154 shows the pattern 

 as ready to be taken from the lathe. 

 The core print ends should be cut down 

 to f inch at each end, and finally cutoff 

 with a saw, and the ends finished with file and sand paper after remov- 

 ing from the lathe, when, as will be seen, the glued end having 

 been cut off, the two halves of the pattern will separate clean and 

 free from glue, and the dowel pins will always bring them into 

 accurate alignment when used by the moulder in the foundry. 

 Before removing the turned pattern from the lathe, it should 

 be smoothed and finished with sand paper, but care must be 

 taken not to allow the sand paper to come in contact with the 

 sharp corners and angles of the pattern, or they will be rounded 

 off' and the- work ruined. For pine, only the finest paper, "No. .', 

 and No. should be used on lathe work, and the paper must not. 

 be held in one position on the revolving work but must be kept 

 moving laterally, that is, from side to side, to avoid cutting depres- 

 sions in tin- siirf'.-ii-e. 



