What machine tool did Leonardo da Vinci design for cutting screw threads?

Leonardo da Vinci designed a screw-cutting machine for producing screw threads. The concept belongs to his extensive work on machine tools, mechanisms, and the controlled manufacture of mechanical parts.

A screw thread must follow a regular helical path, so cutting one accurately requires coordinated motion between the workpiece and the cutting tool. Leonardo’s design addressed that problem mechanically, anticipating the later development of specialized screw-cutting lathes.

This invention is sometimes confused with the ordinary lathe. A lathe rotates a workpiece so it can be shaped, but a screw-cutting machine adds a mechanism that synchronizes the tool’s movement with the rotation to form a continuous thread.

Leonardo’s drawings were often more important as technical studies than as ready-to-build workshop plans. Many of his machine concepts were not constructed in his lifetime, yet they documented principles that later engineers and machinists developed into practical equipment.