386 APPLIED SCIENCE 



the other mixtures, an addition of litharge will tend lo 

 toughen it. 



Since the invention of the molding machine, the match is 

 not so much used as formerly. The great advantage of the 

 molding machine is its facility in the production of small 

 castings in which the patterns are of metal, mounted, or 

 " gated," as it is termed, on a runner. Several castings may 

 be obtained in each mold with no more labor than is needed 

 to obtain one casting if only a single pattern is used. 



The making and preparation of the patterns for match- 

 molding are usually the work of the metal pattern-maker. 

 The first pattern is usually of wood and is called the master- 

 pattern. From it the metal patterns are obtained. 



430. The Molding Board. Many patterns are of such 

 an irregular shape that a straight parting line cannot be ob- 

 tained while molding. In cases of this kind, the pattern is 

 usually mounted on a molding board (sometimes called a 

 follow board). This board is so contrived as to support the 

 pattern upside down in the desired position in the mold. 

 The drag is reversed and rammed while the pattern is sup- 

 ported upon the molding board. Then the drag is turned 

 over, the board removed, and the cope rammed as usual. 



The molding board is used also to support small patterns 

 which tend to spring from the force of the ramming. All 

 stove-plate work that is not mounted on machines is molded 

 in this way, the method, of course, making necessary a special 

 equipment of flasks. 



431. The Match Plate. In the molding of small cast- 

 ings where a great number are required, it is customary to 

 mount several patterns on a plate called a match plate. This 



