Leonardo da Vinci sketched a ball bearing using balls to reduce friction between moving surfaces.
His design placed rolling balls between rings or tracks so that one component could turn more easily against another. Rolling contact generally creates less resistance than sliding contact, making the arrangement useful for rotary motion.
Leonardo’s notes from around 1498 show an early attempt to prevent the balls from crowding together. That detail matters because freely moving balls can bunch up and interfere with smooth operation. His sketch therefore addressed both friction and the practical control of the rolling elements.
Modern ball bearings use carefully manufactured races, cages, lubrication, and hardened materials. Leonardo’s drawing was an important early concept, but it was not equivalent to a modern precision bearing or proof that he produced one for industrial use.