IRON AND IRON MOLDING 



377 



FIG. 189. Making Cores for Cast Iron Pipe. 

 Cores for pipes are made on a bar. Hay is 

 wound on this bar and then loam is carefully 

 worked into the hay. The core is then dried 

 and given a second coat of mud, dried again, 

 and blackened. It is then placed in the mold. 



is covered to a thickness of V/2 in. 'with facing sand, after which 



the flask is filled with unriddled sand and rammed until it is 



compact. A form 



of pin, called a 



riser pin, is em- 

 bedded in this half 



of the mold until it 



touches the pattern. 



This riser helps to 



carry off the gases, 



and also causes any 



foreign matter that 



may have accumu- 

 lated in the mold to 



flow out; it also 



warns the molder as 



to when the mold 



is filled with metal. 

 The mold is then 



vented by J/g in. rods inserted into the sand about two inches apart, 



until they hit the pattern. When withdrawn, they leave small 



holes in the mold by which the gases escape. A cover board is 



placed over the flask 

 and clamped on, the 

 cope lifted and 

 dressed, the gate pin 

 and riser pin with- 

 drawn, and both 

 parts of the pattern 

 are rapped and with- 

 drawn from the 

 sand. The mold is 

 washed with a solu- 

 tion of lampblack 



FIG. 190.Drying Molds. Before the core can and ^molasses to 

 be placed, the mold must be thoroughly dried. ,. ,1 f 



This is done by either gas or coke fires. iorm a smootn lace. 



If necessary, the 



drag part of the mold can be vented by forcing }/ in. rods from 



