Leonardo da Vinci sketched a ball bearing that used free-moving balls to reduce friction between rotating surfaces.
His notebooks show bearing concepts in which balls separate moving parts, allowing one component to rotate more easily against another. This principle is familiar in modern machinery, where hardened balls transfer loads while reducing sliding contact.
Leonardo’s drawings are evidence of an early recorded bearing concept, not proof that he manufactured the modern standardized bearing. Bearings existed in simpler forms before his time, and later engineers developed cages, precise races, improved materials, and mass production.
A ball bearing is different from a roller bearing, whose rolling elements are cylindrical or otherwise elongated. It is also different from a sleeve bearing, in which a shaft slides inside a lubricated surface rather than rolling on separate balls.