How did Henry Maudslay's screw-cutting lathe produce accurate screw threads?

Henry Maudslay’s screw-cutting engine lathe, designed in 1797, achieved precision through the integration of a lead screw used to drive the tool carriage.1

By gearing this lead screw directly to the lathe's spindle, Maudslay ensured that the cutting tool advanced at a constant, controlled rate relative to the rotation of the workpiece, which guaranteed the production of accurate screw threads. By 1800, he further refined this system by equipping the lathe with 28 change gears. This allowed for the cutting of threads with various pitches by precisely controlling the ratio between the speed of the lead screw and the speed of the spindle.1

This innovation was a foundational development in the history of machine tools, as it provided the mechanical consistency necessary for the later realization of mass production and interchangeable parts.1