> After repeated copying and correction, Maudslay made a master screw five feet long and two inches across, with fifty threads to the inch and a foot-long nut that engaged six hundred of them at once.

That's the stuff I like to read about the historical endeavors. A fifty-threads nut doesn't average the distance between the grooves quite accurately enough? Then let's make a nut with six-hundred threads on it, and so what if it's foot long.

I actually didn't understand that paragraph. Is it saying that instead of averaging between two screws it instead averaged across 600? Edit: Or that the nut had 600 threads?