Leonardo da Vinci sketched a ball bearing as an early low-friction mechanical component.
His studies of bearings date to the late fifteenth century. The drawings show balls positioned between moving surfaces so that sliding friction could be reduced by replacing it with rolling motion. Leonardo also explored ways to keep the balls from bunching together, including arrangements resembling a cage.
The principle is simple but important: a rolling ball generally encounters less resistance than two surfaces rubbing directly against each other. Modern bearings use carefully manufactured races, balls, lubrication, seals, and cages, but Leonardo’s sketches addressed the central mechanical problem long before industrial precision manufacturing existed.
Leonardo was not the sole inventor of every form of rolling bearing, and ancient and medieval devices also used rollers or rotating supports. His significance is that his notebooks clearly record a sophisticated ball-bearing concept and a solution to ball separation. The design remained a study rather than a mass-produced component in his lifetime.