376 



APPLIED SCIENCE 



The sand forms a cavity 

 of a desired form in which 

 the hot metal flows. When 

 the iron cools, it forms the 

 casting. 



RG. 187-Cope and Drag of a Mold. ' Steps in Molding. 



The pattern is placed on a 



board or plate called a bottom board, and a special kind of sand, 

 called facing sand, is placed around 

 and above the pattern to a thickness 

 of about l l /2 in. The rest of the 

 flask is filled in with unriddled 

 (unsifted) sand and rammed (ham- 

 mered) properly. Sometimes gag- 

 gers or cast rods with projections 

 are embedded in the sand to help 

 hold it together. A board is then 

 placed on the top of the flask arid 

 clamped. The flask is then rolled 

 over. 



Next the molding board is re- 

 moved, and the face of the drag 

 smoothed over firmly with a trowel 

 to make it smooth and firm. After 

 this a gate pin is embedded in the 

 face of the mold about one inch 

 deep, or at least deep enough to 

 make it retain an upright position, 

 and a, groove is cut from this pin to 

 the pattern. Parting sand, a mix- 

 ture of burnt sand and charcoal, is 

 then dusted over this face and the 

 cope half of the pattern is placed on 

 the drag and centered by dowel pins. 



The drag part of the flask is then 

 placed in position, and the pattern 



FIG. 188. Ramming Molds 

 the First Step in Molding a 

 Cast Iron Pipe. A large 

 cast iron flask is placed in a 

 pit and a pattern is placed 

 in the flask. Sand is then 

 filled in around the flask and 

 rammed down hard . In this 

 case, the rammers are driven 

 by compressed air and are 

 suspended by a stationary 

 overhead crane. The pat- 

 tern is then drawn and the 

 mold is ready for the core, 



