A molder in seven hours will make from 70 to 150 molds. They are stacked two or three high. Wooden frames or jackets are slipped over some molds to prevent the iron from bursting out at the sides. In pouring the molds, cast-iron weights with slots in them to expose the sprue holes are placed on the row of molds nearest the bench to prevent the iron from rais ing the cope. These weights are changed as fast as a row is poured.
Floor Molding. (Stove plate, etc.).— Each piece is molded in a wooden or in an iron flask. The cope is barred with cross bars six or seven inches apart, with the lower edges con forming to the shape of the inside of the pat tern and about one inch away. If the bars are of iron they have holes cast in them and if of wood nails are driven in the lower edges to pre vent the sand from dropping out. The pattern, usually of iron, is fitted to a wooden mold board. The gates are generally separate from but set against the pattern. Whenever possible flat gates are used.
The molder's floor is perfectly level and gen erally of brick or cement. The sand heap ex tends the whole length and the flasks and mold boards are piled at one side.
The pattern on its mold-board is placed on the front of the floor. The pattern is brushed, the drag is inverted on the board, sand is riddled on and then heaped up with a shovel.
The rammer for all floor work is about four feet long with a metal pene and butt. Sand is pened twice around the edge of the flask to prevent the iron running out and to make a hard parting. The sand is leveled with the hand and then stepping on the sand, by a series of backwardjumps, the molder jumps it off, in rows lengthwise and crosswise. He then butts it all over, a little harder under the gates. He fits the bottom board, then removes it, cuts gutters across especially under where the gates will be and runs a vent wire one-. eighth of an inch in diameter all over the drag nearly to the patterns. Then replacing the bot tom board and damping together the bottom board, drag and mold-board the mold is rolled over. After knocking the clamps off, the molder removes the. mold-board, puts on the cope, and fastens it to the bottom board with clamps opposite each sprue. The sprue pattern is put in place, sand is riddled on, and then shoveled one quarter full. Then with a hand on each side of each bar, the sand is tucked with the fingers under the bar and around the sprues. The cope is heaped with sand and is
perked around the sides of the cope and on each side of each bar. Then the sand is gathered by the hands between the bars and jumped off. The molder cleans the bars of sand and butts the sand all over, being careful not to hit the bars or the sand will not lift.
All loose sand is brushed off the surface of the mold and the sprue is removed. Metal wedges are pressed in between cope and drag at each corner, the clamps knocked off, and the wedges pushed clear in. The cope is rolled up nearly perpendicular and held ,there by an old file or piece or rod. The sprue is taken out and with a bellows all loose sand is blown from the drag and from the front and back of the cope. The sand is sponged at the edges of the pattern and the set gates.
After the pattern is drawn lead facing is dusted from a bag all over the mold to prevent the sand burning into the iron. Then charcoal facing is dusted on to prevent the lead sticking to the pattern. After printing the pattern back in the mold the set gates and pattern are drawn and the flask is closed and clamped. The iron should be poured as dull as possible to prevent the sand from burning into the iron. In the molding thus described the man molds the same piece over and over and becomes very expert, and generally working by the piece makes very good wages.
General Jobbing and Machinery Castings. (Roll Over Work.)— The previous description applies to this class also. Patterns are generally of wood and are made one-eighth inch per foot larger than the casting to make up for shrink age. The pattern tapers at least one-eighth inch in a foot to help in drawing the pattern. Any overhanging parts of a pattern must be held by dowel-pins and such parts are drawn after the other part of the pattern is out.
It is better to have iron enter a mold from the bottom and for this purpose the sprue passes down to the bottom of the pattern and across to the mold through a hollow core molded into the drag. One or more risers are placed on the highest points of the mold through which the iron will rise after the mold is full. Dirt and gas will rise also and the riser may be large enough to allow churning with a rod-to keep open a channel to the centre of the casting and through which melted iron may be poured to prevent spongy spots form ing in the parts that cool last.