Machine tool that changes the size or shape of a piece of material, usually sheet metal, by applying pressure to a die in which the workpiece is held. The form and construction of the die determine the shape produced on the workpiece. A punch press has two components: the punch, which is attached to the reciprocating (back and forth, or up and down) ram (plunger) of the machine; and the die, which is clamped onto a bed or anvil whose flat surface is perpendicular to the path of the ram. The punch pushes against the workpiece, which is held in the die. Punch presses are usually driven by electric motors. See also hydraulic press.
This entry comes from Encyclopædia Britannica Concise.
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