Leonardo da Vinci studied a ball-bearing mechanism in sketches made during his investigations of friction.
Around 1498, Leonardo drew arrangements of balls that could move between rings or surfaces. The purpose was to reduce rubbing between parts by replacing sliding contact with rolling contact. This is the basic principle behind a ball bearing, although Leonardo’s sketches do not constitute a complete modern bearing specification.
The drawings are associated with his work on friction and mechanical motion. He recognized that rolling elements could help keep moving surfaces apart, but his concepts were not mass-produced and did not create the modern bearing industry. Standardized bearings required later advances in materials, manufacturing, lubrication, and precision engineering.
Leonardo’s design is sometimes described as the invention of the ball bearing. That wording is too absolute because earlier rolling-element ideas existed, and the history of bearings developed gradually. His sketches are nevertheless an important early record of a recognizable bearing principle.