PATTERN MAKING 



indefinitely, but the foregoing, we think, will give such suggestions 

 as will enable the beginner in pattern making to construct all 



SECTION 

 AT EF 



Pig. 133. 



Fig. 132. 



ordinary patterns so that they can easily be removed from the 

 sand without injury to the mould. 



PATTERNS FROM DRAWINGS. 



As already explained, the pattern maker must understand 

 working drawings in order to construct patterns from them directly. 

 These drawings are usually made to a scale much less than the 

 actual size of the required work, and always represent the com- 

 pleted OT finished machine or one of its parts. 



Drawings are made for the machine shop to guide the machinist 

 in cutting, turning, planing, and fitting the parts given, so as to 

 produce in the castings the shapes, sizes, and general requirements 

 of the articles to be constructed. Hence there is less liability for 

 mistakes after the castings reach the machinist, as he has before 



O 



him not only the drawing with its accurate dimensions to work 

 from, but also the castings for the machine or its parts, from all 

 of which the construction and uses of these several parts can 

 easily be understood. 



On the other hand, the pattern maker, with the aid of the 

 same drawing, must imagine the casting before him, and must 

 build something in wood which will produce that casting in metal. 

 This pattern, in some cases, will be a duplicate of the required 

 casting, but more often it has only a general resemblance to it, 



