What type of bearing did Leonardo da Vinci sketch using freely moving balls?

Leonardo da Vinci sketched a ball bearing using freely moving balls between surfaces.

In his studies of mechanics, Leonardo explored ways to reduce friction between moving parts. One surviving design shows balls arranged so that they would separate surfaces while allowing relative motion. This principle is the basis of a ball bearing: rolling elements replace much of the sliding friction that would otherwise occur.

Leonardo’s sketch is frequently cited as an early design for a ball bearing, but he did not create the standardized, enclosed bearings used in modern machines. Manufacturing accurately sized balls and races was difficult before later improvements in precision engineering and metallurgy.

The term ball bearing refers to the bearing type, not to one particular Leonardo machine. Roller bearings use cylindrical elements instead, while needle bearings use especially narrow rollers. Leonardo’s drawing is historically significant because it recognized the mechanical advantage of rolling contact centuries before industrial production made such components commonplace.