A type of gravity A term generally applied to forging hammers wherein energy for forging is provided by gravity, steam, or compressed air. See also Air-Lift Hammer, Board Hammer, Steam Hammer. where wood boards attached to the The main reciprocating member of a press, guided in the press frame, to which the punch or upper die is fastened. are raised vertically by action of contrarotating rolls, then released. Energy for The process of working metal to a desired shape by impact or pressure in hammers, forging machines (upsetters), presses, rolls, and related forming equipment. is obtained by the mass and velocity of the freely falling ram and the attached upper The machined recess in a die that gives the forging its shape.. See also Drop A machine that applies a sharp blow to the work area through the fall of a ram onto an anvil. The ram can be driven by gravity or power. See also Gravity Hammer and Power-Driven Hammer..