What machine did Leonardo da Vinci design to make a continuous screw from wood?

Leonardo da Vinci designed a screw-cutting machine to produce a continuous screw from wood.

His mechanical drawings include a device in which a workpiece could rotate while a cutting tool followed a guided path. This arrangement was intended to create a regular helical thread, an important shape for screws, presses, lifting mechanisms, and other machines. The design shows Leonardo applying controlled motion and gearing to a manufacturing task.

A screw-cutting machine should not be confused with a simple hand tool for carving threads. The key idea is repeatable production: the relationship between rotation and tool travel determines the pitch of the thread. Renaissance workshops commonly made screws by laborious manual methods, so a guided machine could improve consistency.

Leonardo’s surviving drawings do not prove that a fully working version was built. They do, however, document his interest in machine tools and in turning complex mechanical forms into repeatable workshop processes.