Leonardo da Vinci sketched a ball bearing using balls to reduce friction between moving parts.
Around 1498, Leonardo drew a bearing arrangement in which metal balls separated two rings. The balls could roll rather than allowing the rings to slide directly against one another, reducing friction in a rotating mechanism. This principle is the basis of the modern ball bearing.
Leonardo’s drawing is frequently cited as an early description of the idea, although it was not a complete modern bearing specification. His design also included a cage-like arrangement intended to keep the balls separated, an important practical issue because touching balls can create extra friction.
The invention is sometimes described as the first ball bearing, but historians usually distinguish between an early documented concept and the later industrial manufacture of standardized, hardened bearings. Modern bearings also use carefully made races, lubrication, seals, and controlled tolerances.