Leonardo da Vinci studied a ball bearing using six balls inside a ring.
Leonardo’s notebooks contain a design for a bearing in which balls separate moving surfaces. The purpose was to reduce friction between parts that rotate relative to one another. His sketch is often cited as an early ball-bearing concept, although later bearing designs and manufacturing methods were needed before reliable industrial bearings became common.
A ball bearing uses rolling contact rather than allowing two surfaces to slide directly against each other. The balls transfer load while reducing resistance, and a cage or retainer in later designs keeps them spaced apart. Leonardo’s concept recognized the value of preventing the balls from bunching together.
The invention is sometimes overstated as the modern ball bearing. Leonardo did not create the standardized, mass-produced bearings used in modern machines. His importance lies in identifying and illustrating a key mechanical principle centuries before precision manufacturing made it broadly practical.