Leonardo da Vinci designed an early ball bearing using rolling elements to reduce friction between moving parts.
His studies of bearings appear in drawings from the late 15th century. The basic idea places balls between surfaces so that rolling replaces much of the sliding friction. Leonardo explored the design while investigating machines, rotating shafts, and methods of making mechanical movement more efficient.
The principle is straightforward but technically important. A bearing must keep its rolling elements separated and guide them as a shaft or ring turns. Leonardo’s sketches include ideas resembling separators, although his design was not a standardized industrial bearing.
Claims that Leonardo invented the modern ball bearing should be qualified. Rolling bearings existed in earlier forms, and mass-produced precision bearings came much later. Leonardo is best credited with an influential early design study and with recognizing the value of controlled rolling contact.