120 



PATTERN MAKING 



of fitting, placing the dowel pins, and forming the two hexagonal 

 ends, is done in the lathe. The construction is shown in the 

 sectional illustration of the half- pattern, Fig. 221. The wood for 

 the two halves must be of sufficient length to allow for gluing at 

 rach end or for the insertion of iron staples. In turning, the 

 greatest care must be taken to center exactly on the parting line of 

 the two halves. 



Fig. 220. 



A carefully shaped template, such as is shown at , Fig. 221. 

 must be used in turning. This template may be made of a thin 

 piece of wood, but for all purposes for which templates are 

 required in pattern making, and their use is necessarily very great, 

 sheet zinc is the best material. It is soft, and easily cut and 

 filed, and does not dull the cutting tools so much as other 

 metals 



Fig. 221. 



Before marking out the template, that the lines may be more 

 readily seen, it should be cleaned with a piece of emery cloth and 

 have a dark coating of the following solution. Dissolve an ounce 

 of sulphate of copper in about four ounces of water and to this add 

 one teaspoonful of nitric acid. Treat the surface of the zinc with 



