PROBLEMS IN PATTERN-MAKING 387 



plate is of metal (as are also the patterns), % m - thick, pro- 

 jects beyond the flask, and has two holes, one on each end, 

 through which the flask pin is inserted. 



In the use of the match plate, a molding machine is 

 generally used, but the plate can be used without the machine. 

 The patterns are mounted on the plate, one-half on each side 

 directly opposite to each other. One side of the flask is 

 rammed at a time, the flask pins locating the plate so accu- 

 rately that the two parts of the flask form a perfect match 

 when placed together. 



The making of these match plates by the metal pattern- 

 maker is expensive because of the difficulty of working metal. 

 Hence it is only profitable to use the match plates when a 

 great number of castings are desired and when a firm is con- 

 tinuously engaged in the production of a line of small goods. 



432. The Molding Machine. The cost of production is 

 reduced by the use of a match plate on a machine. The 

 rapidity with which the molds can be produced and the 

 possibility of producing castings which require the minimum 

 of machining, lowers the cost. Machine-work in finishing is 

 always a costly process. 



In recent years the molding machine has been improved 

 so that at the present time very large castings are produced 

 by it. Of course, its use is only possible or profitable for 

 large-scale production, as the machines for large work, with 

 their patterns, are very expensive. 



A large machine of this type is the stripping plate machine 

 in the operation of which the sand is rammed by hand and 

 the pattern drawn down through a metal plate which sup- 

 ports the sand and prevents breaking. By this method, 

 castings can be produced close to uniform size. 



