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

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A diagram displays six types of simple machines with labeled illustrations: inclined plane, wedge, screw, lever, wheel and axle, and pulley, each shown with real-world examples like ramps, axes, screws, seesaws, door handles, and pulleys lifting objects. — machine Six simple machines for transforming energy into work.

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

This lead screw was geared directly to the lathe's spindle, which ensured that the cutting tool advanced at a constant rate of speed relative to the rotation of the workpiece, thereby guaranteeing the production of accurate screw threads. By 1800, Maudslay further refined this system by equipping his lathe with 28 change gears. These gears 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 fundamental advancement in machine tool technology, providing the consistency necessary for the later development of mass production and interchangeable parts.1