cam, mechanical device for converting a rotating motion into a reciprocating, or back-and-forth, motion, or for changing a simple motion into a complex one. A simple form of cam is a circular disk set eccentrically on a shaft in order to induce (when the shaft rotates) a rising and falling motion in a rod or some other moving part held against its edge. There are cams of many diverse shapes, e.g., oval, elliptical, and scalloped-edged, each shape being designed to induce the particular kind of motion required in a moving part. Cams are widely used in many different kinds of machines.
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