What machine did Leonardo da Vinci design to cut threads in screws more consistently?

Leonardo da Vinci designed a thread-cutting machine to make screw threads more consistently.

The machine used coordinated mechanical movement to guide a cutting tool along a rotating workpiece. By controlling the relationship between the workpiece and the cutter, the design addressed the difficult problem of producing regular threads by hand.

Screws were already known before Leonardo, but accurately matching a screw with its nut required careful craftsmanship. A machine that standardized the pitch could improve the manufacture of mechanical parts and make complex mechanisms more reliable.

Leonardo’s device belongs to his studies of machine tools and workshop production. It should not be confused with the later industrial screw-cutting lathe, which used developments in precision engineering and powered machinery. Leonardo’s design was an important early mechanical proposal, not a modern factory machine.