Leonardo da Vinci sketched a ball bearing as a way to reduce friction between moving parts.
Around 1498, Leonardo studied a bearing using balls placed between moving surfaces. The balls were intended to replace sliding friction with rolling friction, allowing a shaft or other component to move more easily. His drawings show an understanding of the need to keep the balls separated rather than letting them crowd together.
Leonardo did not invent every form of bearing, and ancient machines used other friction-reducing arrangements. His importance is that his notebooks contain an early clear design for a ball-bearing mechanism. The modern term covers many later forms, including radial and thrust bearings.
The sketch also demonstrates Leonardo’s habit of examining small mechanical details. Bearings were crucial to the machines he studied because friction could waste power, generate heat, and slow movement. His concept anticipated a component that became central to clocks, engines, vehicles, and industrial machinery.