Leonardo da Vinci’s ball-bearing mechanism used steel balls between moving surfaces to reduce friction.
Leonardo sketched a bearing system around 1498 while working on mechanical studies in Milan. The design placed balls inside a ring-like arrangement so that surfaces could move with rolling contact instead of sliding contact. This principle is the basis of modern ball bearings.
Leonardo did not invent every form of bearing, and rolling elements had ancient precedents. His contribution was a clear mechanical arrangement showing how separate balls could prevent one rotating surface from rubbing directly against another. The sketch is often cited as an early modern study of the ball bearing.
A common mix-up is calling Leonardo’s drawing a complete modern bearing. Modern bearings use carefully manufactured races, cages, lubrication, and standardized dimensions. Leonardo’s design was a conceptual mechanism, but it captured the essential advantage of rolling friction and influenced how historians describe the development of machine engineering.