Leonardo da Vinci drew a ball bearing using balls to reduce friction between moving parts.
His notebooks include a bearing concept in which balls move between rings, allowing one component to rotate more easily against another. The principle is simple: rolling contact generally produces less resistance than sliding contact. Leonardo’s arrangement also aimed to keep the balls separated so they would not bunch together.
The drawing is often cited as an early description of a modern bearing principle, not as proof that Leonardo manufactured a standardized industrial ball bearing. Later engineers developed stronger materials, accurate manufacturing, lubrication systems, and cages that made bearings practical at large scale.
A ball bearing should not be confused with a gear. Gears transmit rotary motion through toothed wheels, whereas bearings support moving parts and reduce friction. Leonardo’s sketch is important because it shows him applying geometric and mechanical reasoning to a problem that remained central to machine design.