PATTERN MAKING. 



PAKT II. 



SIMPLE PATTERNS. 



The simplest patterns are those which are made in one piece, 

 and which require no coring, although the castings themselves may 

 be hollow. 



The first thing which the pattern maker should decide in com- 

 mencing a pattern, is the way in which it is to be removed from 

 the sand, and where the parting line, if there is one, should be. 

 As an example of a simple pattern of one piece made without a 

 dry-sand core, the stuffing-box gland (shown in Fig. 134, Part I) 

 is a good illustration. It is readily seen that if the pattern of such 

 a gland were to be imbedded in sand, as shown, there is no reason 

 why it could not be lifted out without disturbing any of the sur- 

 rounding or the internal sand. The drawing represents the pattern 

 with draft and finish added, the finished gland being shown by 

 the dotted lines. 



In every pattern of this kind, forming its own core, it is neces- 

 sary to allow double draft on the inside, so that the pattern may be 

 rapped and removed without injury to the green-sand core, which 

 at best is not very stable, and which should be used only when the 

 gland or other hollow casting is of such size- as to give a large and 

 stable core. 



Except in a few special cases, it is much better to put core 

 prints on the ends of the pattern and use a dry-sand core in place 

 of the green-sand core illustrated above, thus avoiding the unnec- 

 essary waste of metal added by the double draft on the inside of 

 the casting, and the expense and labor of removing it in the 

 machine shop. 



In order to give a better understanding of the methods em- 

 ployed in Pattern Making, the object itself will be illustrated; and 

 when it is to be finished, the finished dimensions only will be given. 

 If the object is not to be finished, the sizes of the completed cast- 



