What machine did Leonardo da Vinci design to produce threaded screws continuously?

Leonardo da Vinci designed a screw-cutting machine for producing threaded screws continuously.

His notebooks include machine-tool studies in which a workpiece could be rotated while a cutting tool advanced along it. This arrangement anticipates the basic principle of a screw-cutting lathe: coordinated rotation and linear tool movement create a regular helical thread.

Renaissance craftsmen already made screws by hand, but producing accurate, repeatable threads was difficult. Leonardo's design aimed to mechanize that task and improve consistency. The surviving drawings do not establish that a complete machine was built or used in a workshop, so it is safest to describe it as a design rather than a proven industrial invention.

The machine belongs to the wider history of machine tools, which later became essential to precision engineering. It should not be confused with the printing press, whose main purpose was reproducing text and images.