What type of bearing did Leonardo da Vinci sketch using balls between two rings?

Leonardo da Vinci sketched a ball bearing using balls between two rings.

His late-15th-century notes show a design intended to reduce friction between moving surfaces. The balls were arranged so they could roll while remaining separated, an important detail because direct sliding contact creates more resistance and wear.

Leonardo did not invent the modern standardized ball bearing in the industrial sense. His drawing was an early recorded concept, and later engineers developed practical cages, precise races, hardened steel, and manufacturing methods. This distinction matters: Leonardo’s design was a mechanical study rather than a mass-produced component.

Ball bearings later became fundamental in wheels, turbines, motors, bicycles, and machines. Leonardo’s sketch is often cited as an early milestone in the history of rolling-element bearings, but modern bearings are the result of centuries of refinement.