Leonardo da Vinci drew a ball bearing using interlocking spheres to reduce friction.
His late-fifteenth-century studies explored how balls could be arranged between moving surfaces so that sliding friction would be replaced by rolling friction. The idea is recognizable as an early bearing design and is frequently cited in histories of mechanical engineering.
A bearing supports a moving part while allowing rotation. In a ball bearing, hardened balls roll between rings, reducing resistance and helping shafts turn smoothly. Leonardo’s arrangement was not identical to the sealed, precision-manufactured bearings used in modern machines, but it shows the essential mechanical insight.
The drawing is sometimes described as the invention of the ball bearing. More precisely, Leonardo produced an early recorded design for the principle. Earlier cultures used rollers and related devices, and modern bearings required later advances in metallurgy, manufacturing accuracy, and lubrication.