Leonardo da Vinci drew an early ball bearing using balls to reduce friction between moving surfaces.
Around 1498, Leonardo studied a bearing in which rolling balls were placed between rings or raceways. The balls could move freely instead of rubbing as one solid surface against another. This arrangement addressed a practical problem: friction makes machines harder to move and causes wear in shafts, axles, and gears.
Leonardo’s sketch is often credited as an early design for a ball bearing, but it was not a modern sealed bearing and may not have been intended as a fully manufacturable component. His design also included a separator-like arrangement to keep the balls from crowding together, an important issue in bearing operation.
Ball bearings became widely practical much later, as precision manufacturing improved during the Industrial Revolution. They are different from roller bearings, which use cylindrical or tapered rollers instead of balls. Both belong to the broader family of rolling-element bearings.