What mechanical tool did Leonardo da Vinci sketch for cutting threads on screws?

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

His mechanical drawings include devices that used a rotating workpiece and guided cutting action to produce regular threads. A threaded screw was valuable in Renaissance engineering because it could fasten parts securely and provide controlled movement in mechanisms such as presses, jacks, and adjusting devices.

Before specialized machine tools, screw threads were often made by hand, so consistency was difficult. Leonardo’s concept belongs to the long development of lathes and other machine tools that transformed irregular manual work into repeatable manufacturing. The drawing is evidence of his interest in production methods, not simply in isolated machines.

Leonardo did not create the basic screw. Screws and screw-like devices were known in antiquity, and Archimedes’ screw served a different purpose by moving water. Leonardo’s innovation was to investigate machinery that could manufacture precise mechanical components, an issue that became increasingly important in later industrial engineering.