Leonardo da Vinci sketched a ball bearing, using balls in a cage to reduce friction between moving surfaces.
The drawing appears in Leonardo’s Codex Madrid I, dating from the late 15th or early 16th century. The basic principle is to replace sliding contact with rolling contact: small balls move between rings or surfaces, allowing one component to rotate more freely against another. Leonardo’s cage arrangement was intended to keep the balls separated so they would not rub together and create unnecessary friction.
Leonardo did not invent every earlier form of rolling bearing, and historians have found ancient examples of rollers and related devices. His importance lies in clearly documenting a caged-ball arrangement resembling the principle used in modern bearings.
The sketch was not part of a mass-produced industrial system. Precision manufacturing, hardened steel, and reliable lubrication were needed before ball bearings could become common in machinery, bicycles, vehicles, and turbines.