What device did Leonardo da Vinci design to make a screw thread by rotating a workpiece?

Leonardo da Vinci designed a screw-cutting machine to make a screw thread by rotating a workpiece.

His mechanical drawings include a device in which a workpiece could be turned while a cutting tool advanced along it. Coordinating rotation and linear movement is essential for producing a regular helical thread.

The proposal reflects Leonardo’s interest in precision manufacturing. Screws were already known before his time, but making consistent threads by hand was difficult. A guided mechanism could improve repeatability and reduce the labor needed to produce threaded components.

Leonardo’s sketches should not be treated as proof that he built a complete industrial machine. Many notebook drawings are exploratory designs, and later machine tools developed through contributions from many engineers. The concept nevertheless anticipates the controlled screw-cutting machinery used in metalworking.