What machine did Leonardo da Vinci design to cut threads in metal?

Leonardo da Vinci designed a thread-cutting machine for producing helical threads in metal.

His mechanical studies explored how a workpiece and cutting tool could move in a controlled relationship. Such coordination was essential for making consistent screws, whose threads must follow a regular spiral path.

Thread production was an important engineering problem because screws were used in presses, mechanisms, and structural assemblies. Leonardo’s design reflects his interest in converting continuous rotary motion into precise, repeatable tool movement.

The machine should not be confused with the modern metalworking lathe as a whole. A lathe is a broader class of machine for rotating workpieces, while the specific Leonardo study focuses on the controlled production of screw threads.