What Leonardo da Vinci machine was designed to cut a screw thread mechanically?

Leonardo da Vinci designed a screw-cutting machine to form screw threads mechanically. His notebooks show an interest in making standardized threaded components with controlled rotary motion.

The machine used a rotating workpiece and guiding mechanisms to coordinate the cutting tool with the material. Producing a consistent thread by hand was difficult, especially when matching a screw to its nut, so a machine that imposed regular spacing offered an important manufacturing advantage.

This concept is related to the later screw-cutting lathe, but Leonardo’s drawing should not automatically be treated as a complete modern lathe. The industrial screw-cutting lathe became especially important much later, when precision manufacturing and interchangeable parts developed. Leonardo’s design is significant because it applies mechanical control to a task that had traditionally depended heavily on skilled handwork. It belongs to his wider interest in machine tools, gears, and repeatable production.