Leonardo da Vinci studied a ball-bearing concept using freely moving balls to reduce friction between surfaces.
His notes and drawings from the late 15th century show balls arranged so that they would roll rather than slide. Rolling contact can reduce friction and make rotational movement easier, which is the central principle behind a ball bearing. The design also addressed a practical problem: if the balls touched one another, they could hinder smooth motion, so Leonardo explored ways to separate them.
Leonardo’s sketches are often described as an early bearing concept, not proof that he invented the complete modern ball bearing. Later engineers developed standardized races, cages, materials, lubrication, and manufacturing methods.
The device should also be distinguished from a roller bearing, which uses cylindrical rollers rather than spherical balls. Both reduce sliding friction, but their shapes and load characteristics differ.