^* Improvements made a long while ago can seem mundane and trivial with the benefit of contemporary sophistication, but were critical in the evolution of precision engineering. John Hall’s improvements are very much of this kind: he tinkered with the means of ejecting a workpiece from the milling machine, and so prevented the die’s temperature from changing dramatically during the process and thus risk losing its temper. He also designed so-called fixtures, the devices that hold a workpiece absolutely secure during milling, further ensuring that his milling cuts were made with all needed precision, an essential for guaranteeing the fit of the pieces.