Leonardo da Vinci studied the ball bearing as a way to reduce friction between moving parts.
His notebooks contain sketches of a bearing arrangement in which balls separate two surfaces. Instead of allowing one surface to slide directly against another, the balls roll between them. Rolling contact generally produces less friction than sliding contact, making rotation easier and reducing wear.
Leonardo’s drawings, usually dated to the late fifteenth century, show his interest in applying the principle to machines. He did not create the standardized, mass-produced bearing used in modern engines and machinery. Later engineers developed races, cages, lubrication systems, and precise manufacturing methods that made bearings reliable at industrial scale.
The idea also appears in several of Leonardo’s other mechanical studies, including devices involving axles, gears, and wheels. A ball bearing is different from a roller bearing: both use rolling elements, but ball bearings use spherical balls while roller bearings use cylindrical or tapered rollers.