What machine did Leonardo da Vinci design to produce a continuous supply of threaded screws?

Leonardo da Vinci designed a screw-cutting machine to produce a continuous supply of threaded screws.

Leonardo’s notebooks include a machine for cutting screw threads, an important step toward the standardized production of mechanical fasteners. The design used rotating work and coordinated movement so that a cutting tool could follow a regular helical path. This was more systematic than shaping each screw by hand.

Threaded screws were already known before Leonardo, but producing them consistently was difficult. A dedicated screw-cutting mechanism could improve uniformity and make screws more useful in machinery. Leonardo’s drawings show his interest in converting skilled manual operations into repeatable mechanical processes.

This invention should not be confused with the water-raising Archimedes screw. The two devices share the word “screw” but have different purposes: one moves water, while the other forms a helical thread on a workpiece. Leonardo’s screw-cutting idea belongs to the development of machine tools and precision engineering.