PATTERN MAKING 



GEAR WHEEL PATTERNS. 



In this special class of pattern work, the greatest accuracy 

 and care must be taken, not only in building up the rim of the 

 wheel, but in fitting and placing on the rim the blocks, out of 

 which the teeth are to be formed, and most of all in laying out 



Nut for valve 



Valve 



Fig. 284. 



Fig. 233. 



the teeth regularly and accurately on the tooth blocks. A pattern 

 for a gear wheel, whose teeth are carelessly made is almost worthless, 

 the time lost" in chipping and filing, for the purpose of correction, 

 being too great to allow the use of such a pattern. 



o 



Valve Spindle 

 Fig. 235. 



To insure greater accuracy and smoother running gears, it 

 is now the custom in many shops to have the wooden pattern 

 made in the form of a blank, (without teeth) from which a metal 

 pattern is cast. 



This cast pattern is turned up and placed in the milling 

 machine where the teeth are cut and spaced with accuracy and 

 to the exact form of tooth required. This metal pattern is used 

 without draft. 



