A crank is a bent portion of an axle, or shaft, or an arm keyed at right angles to the end of a shaft, by which motion is imparted to or received from it; also used to change circular into reciprocating motion , or reciprocating into circular motion. Familiar examples of a crank for manual use include the crank on a manual pencil sharpener and the cranks on the pedals that drive a bicycle.

Cranks were formerly common on some machines in the early 20th century; for example almost all phonographs before the 1930s were powered by clockwork motors wound with cranks, and internal combustion engines of automobiles were usually started with cranks before electric starters came into general use.

See also crankshaft.