Айналма біліктің қимылын беру немесе алуға арналған құрал (қолдық)

Simple machine transferring motion to or from a rotating shaft at a distance from the centreline

A crank is an arm attached at a right angle to a rotating shaft by which circular motion is imparted to or received from the shaft. When combined with a connecting rod, it can be used to convert circular motion into reciprocating motion, or vice versa. The arm may be a bent portion of the shaft, or a separate arm or disk attached to it. Attached to the end of the crank by a pivot is a rod, usually called a connecting rod (conrod). The term often refers to a human powered crank which is used to manually turn an axle, as in a bicycle crankset or a brace and bit drill. In this case a person's arm or leg serves as the connecting rod, applying reciprocating force to the crank. There is usually a bar perpendicular to the other end of the arm, often with a freely rotatable handle or pedal attached.

Almost all reciprocating engines use cranks (with connecting rods) to transform the back and forth motion of the pistons into rotary motion. The cranks are incorporated into a crankshaft.

[[File:Bundesarchiv Bild 135 BB 152 11, Tibetexpedition, Tibeter mit Handmühle. jpg|thumb|upright|Tibetan operating a quern (1938). The upright handle of such rotary handmills, set at a distance from the centre of rotation, works as a crank. but since then a series of similar pottery models with crank operated winnowing fans were unearthed, with one of them dating back to the Western Han dynasty (202 BC 9 AD). Historian Lynn White stated that the Chinese crank was 'not given the impulse to change reciprocating to circular motion in other contrivances', citing one reference to a Chinese crank and connecting rod dating to 1462. A Roman iron crankshaft of yet unknown purpose dating to the 2nd century AD was excavated in Augusta Raurica, Switzerland. The long piece has fitted to one end a long bronze handle, the other handle being lost. A ca. long true iron crank was excavated, along with a pair of shattered mill stones of diameter and diverse iron items, in Aschheim, close to Munich. The crank operated Roman mill is dated to the late 2nd century AD. An often cited modern reconstruction of a bucket chain pump driven by hand cranked flywheels from the Nemi ships has been dismissed though as "archaeological fantasy". [[File:Römische Sägemühle. svg|thumb|Roman Hierapolis sawmill (3rd century AD), the earliest known machine to combine a crank with a connecting rod. On the pediment of the Hierapolis mill, a waterwheel fed by a mill race is shown powering via a gear train two frame saws which cut rectangular blocks by the way of some kind of connecting rods and, through mechanical necessity, cranks. The accompanying inscription is in Greek. The crank and connecting rod mechanisms of the other two archaeologically attested sawmills worked without a gear train. In ancient literature, there is a reference to the workings of water powered marble saws close to Trier, now Germany, by the late 4th century poet Ausonius; The three finds push back the date of the invention of the crank and connecting rod by a full millennium:

The crank appears in the mid 9th century in several of the hydraulic devices described by the Banū Mūsā brothers in their Book of Ingenious Devices. These devices, however, made only partial rotations and could not transmit much power, although only a small modification would have been required to convert it to a crankshaft. Al Jazari (1136–1206) described a crank and connecting rod system in a rotating machine in two of his water raising machines. His twin cylinder pump incorporated a crankshaft. After al Jazari cranks in Islamic technology are not traceable until an early 15th century copy of the Mechanics of the ancient Greek engineer Hero of Alexandria.

A crank axle is a crankshaft which also serves the purpose of an axle. It is used on steam locomotives with inside cylinders.