Leonardo da Vinci designed a ball bearing using paired wheels and balls to reduce friction between moving surfaces.
His notebooks from the late fifteenth century include sketches of bearing mechanisms in which small balls separate parts that would otherwise rub directly against each other. The basic engineering principle is rolling contact: rolling generally creates less resistance than sliding, allowing a shaft or platform to move more easily.
Leonardo’s sketches are important early examples of the concept, but they were not the same as a modern manufactured bearing. His designs vary in form, and some historians note that the balls could touch one another or become displaced, limiting efficiency. Modern bearings use carefully shaped races, cages, hardened materials, and precise manufacturing.
The invention is sometimes credited to Leonardo as though he created the complete industrial ball bearing. More precisely, he documented and refined an early bearing idea. Ball bearings later became essential in machinery, bicycles, motors, turbines, and many other devices requiring controlled rotation.