PIT MOLDING METHOD

Molds are large jobs are generally prepared in pit dug in the foundry floor which facilitates in lifting the pattern and casting the mold easily. Since a pit which functions as drag cannot be rolled over, the sand under the pattern may be rammed by bedded-in. The pattern may be suspended in correct location as the sand is rammed under it. In other cases, if the bottom surface of a pattern is flat, the pattern can be placed on a flat-level surface rammed up for it.

A bed of coke is laid on the bottom of the pit, covered with straw and then a layer of sand , which is rammed and leveled . The coke bed is connected with atmosphere by vertical vent pipes in the corners of the pit to provide an outlet for the gases generated. If the floor is lightly damp, the inside surfaces of the pit are lined with tar-paper, bricks, or wooden planks. Generally, one box is required to complete the mold. Runners, pouring basins, feeders, are cut in it.

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ELECTRICAL COMPARATORS AND ITS WORKING

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Mechinopedia For Mechanical Engineers

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