What machine did Leonardo da Vinci design to produce uniform metal sheets?

Leonardo da Vinci designed a rolling mill to produce more uniform metal sheets.

A rolling mill passes metal between rotating rollers, reducing its thickness and helping create a flatter, more consistent sheet. Leonardo’s notebooks include mechanisms for driving rollers and controlling the movement of material through the machine. The design reflects his broader interest in making workshop processes repeatable and less dependent on hand finishing.

Rolling mills became especially important in metalworking because they could shape material continuously and with greater regularity than hammering alone. Leonardo’s proposal should not be confused with a blast furnace, which produces molten iron, or a press, which applies force in a different way.

The surviving drawings are design studies rather than evidence of a large industrial mill built by Leonardo. They nevertheless show his ability to connect gears, shafts, rollers, and human or mechanical power into a practical manufacturing system.