What Leonardo da Vinci invention is associated with the modern ball bearing?

Leonardo da Vinci is associated with an early ball-bearing design showing balls arranged to reduce friction.

In his mechanical studies, Leonardo explored ways to prevent moving surfaces from rubbing directly against one another. One surviving design places spherical elements between rings, allowing motion to occur with rolling contact instead of sliding contact. That arrangement resembles the principle of a modern ball bearing.

The idea is often credited to Leonardo in popular histories, but it is more precise to say that he documented an early bearing concept. His drawing did not establish the modern industrial bearing industry, which required later advances in manufacturing, hardened materials, lubrication, and precision engineering.

Ball bearings are used to support rotating shafts while reducing friction. They should not be confused with roller bearings, which use cylindrical or tapered rollers. Leonardo’s importance here lies in recognizing a useful mechanical principle long before factories could produce such parts accurately and reliably.