Leonardo da Vinci sketched a ball bearing as a way to reduce friction between moving surfaces.
His late-fifteenth-century studies included balls placed between rings so that one surface could roll against another. Rolling contact produces less friction than sliding contact, which is the basic principle behind modern bearings.
Leonardo’s sketches are often cited as an early recorded design for a ball bearing, but he did not invent every bearing concept. Ancient and medieval engineers had already used rollers and other friction-reducing devices. Leonardo’s contribution was a clear, documented exploration of a compact bearing arrangement.
Modern ball bearings use precisely manufactured balls, races, cages, and lubricants. They appear in machines ranging from bicycles to electric motors. Leonardo’s version was a conceptual mechanical study rather than a standardized industrial component.