For finer work in the machine shop, this isn't really an issue and has been done for probably a hundred years. You just decimalize the inch. For farmer type tolerances, I usually concern myself with thousandths (.001). The digital scales on my equipment resolve to .00001, but seriously, we're really fooling ourselves if we think the equipment can hold those tolerances. Half a thou (.0005) might be attainable.
The big advantage in the old style leadscrew type machine shop is seen in the fractional basis of our measure system. Leadscrews on my mill are cut at a 5 TPI. A full turn of the leadscrew moves the table .2. Half a turn moves it .1. A large enough dial on the screw allows 200 marks around the circumference, which works out nicely to each mark being .001 and with a little estimation, it's easy enough to guestimate to half a thou.
I guess they do it with metric machine tools, but I'm curious what you would use for a thread pitch that is resistant to wear while still being precise enough to resolve to 12.7μ. How is 12.7μ easier to work with than half a thou (.0005)?
The next thing I'd like to see is for you or any accomplished machinist for that matter, explain how using a threading dial on a lathe for single point threading works so much easier on a completely metric lathe and cutting their myriad of supposedly superior standards of multiples of ten but in real life, we see pitches of .4, .45, .5, .7, .8, 1, 1.25, 1.5, 1.75, 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5.
Here's a comparison of Imperial and metric threading instructions for a lathe. Imperial has a 8 TPI leadscrew and the Metric uses 4MM pitch. Kind of comical to see a system that is supposed to be multiples of ten and see those pesky fractions like 5/8, 3/4, 7/8, 1-1/4, 1-3/8 pop up only in their decimalized forms.
Also check out how many different imperial pitches can be cut by just waiting for the threading dial to get to any mark, or an eighth of a turn instead of a half turn or fourth at best. For the uninformed, it might not seem like the difference between half a turn and an eighth turn on the threading dial is a big deal. I'd encourage you to try it once and see just what the difference in time required is.