What type of machine did Leonardo da Vinci sketch for producing threaded screws continuously?

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

His mechanical notebooks include designs for machines that could guide a cutting tool along a rotating workpiece. By coordinating the workpiece’s rotation with the tool’s movement, such a machine could create a regular helical thread. This was a significant manufacturing idea because accurately made screws were difficult to produce by hand.

Leonardo’s drawing belongs to the long development of machine tools. It does not mean that he invented the modern engine lathe or created industrial interchangeable screw production. Those achievements depended on later advances in precision engineering, including improved slides, lead screws, and metalworking methods.

The machine is easy to confuse with a drill or an ordinary lathe. A drill makes holes, while a lathe rotates a workpiece for cutting or shaping. A screw-cutting machine adds controlled helical motion so the tool follows the pitch of a thread.