pinion

Pinion refers to several related concepts, most prominently in mechanical engineering and in everyday language. In mechanics, a pinion is a gear wheel that engages with another gear or with a rack to transmit motion and power. The pinion is typically the smaller of the mating gears, and its teeth determine the gear ratio, torque, and speed of the system. Pinions are used in a wide range of machinery, from handheld devices to industrial gear trains.

A common configuration involving a pinion is the rack-and-pinion system. In this arrangement, the rotational motion of the pinion is converted into linear motion of a rack, or vice versa, enabling precise steering in automobiles and controlled movement in various machines. Pinion gears also drive larger gear wheels such as ring gears in reductions, blowers, and other mechanical drives.

Outside of pure mechanics, pinion appears in language with a different meaning. As a verb, pinion means to restrain or immobilize, especially by binding the wrists or ankles. The term is also used in animal management to describe the practice of pinioning wings, which involves trimming or clipping a bird’s wings to prevent flight.

Etymology traces pinion to Old French pignon, with broader usage evolving to cover both the mechanical gear and the act of binding or restraining. In modern technical contexts, “pinion” most often denotes the small gear that drives or meshes with a larger gear or rack.