What bearing design is Leonardo da Vinci often credited with sketching?

Leonardo da Vinci is often credited with sketching an early ball bearing design.

His mechanical studies include arrangements of balls intended to reduce friction between moving surfaces. In a ball bearing, rolling elements separate the surfaces, allowing one part to rotate more easily than it would if it slid directly against another.

Leonardo’s design is notable because it addressed a practical problem that affected many machines: friction, wear, and the tendency of balls to bunch together. His concept included a cage-like arrangement to keep the balls separated, an important feature of later bearings.

The attribution requires care. Leonardo did not invent every bearing principle, and his drawing was not a mass-produced modern bearing. Ancient and medieval machines used related rolling elements, but Leonardo’s documented study is one of the best-known early bearing concepts.