Leonardo da Vinci studied a ball bearing using balls between moving surfaces.
His late-fifteenth-century sketches show rolling balls intended to reduce friction between components. The principle is straightforward: rolling contact generally creates less resistance than sliding contact, allowing parts to move more easily. Leonardo’s design also aimed to keep the balls separated so they would not bunch together.
The sketches are important in the history of bearing ideas, but Leonardo did not invent every form of bearing. Ancient and medieval machines used related methods of reducing friction, and modern ball bearings developed through later engineering and manufacturing advances.
A ball bearing is not itself a complete machine. It is a machine element used in wheels, shafts, tools, and engines. Its significance lies in making rotational movement smoother and more efficient.