Leonardo da Vinci sketched a ball bearing as a low-friction support for rotating machinery.
Around 1498, Leonardo studied the use of balls between two rings so that one surface could roll against another. Rolling contact produces less friction than sliding contact, making the arrangement useful for mechanisms that must rotate smoothly.
His sketches show an early form of a caged ball-bearing concept. The cage was important because it kept the balls separated rather than allowing them to bunch together. Leonardo’s design therefore addressed both friction and the practical movement of the rolling elements.
Leonardo did not invent the modern standardized bearing industry, which developed centuries later with improved materials, precision manufacturing, and lubrication. His drawings are significant because they show an unusually clear early understanding of the principle behind modern ball bearings.