[cucumber3732842]

The unit itself doesn't actually matter. Even industries with the least precision set their stuff up with so much precision that the unit you use basically doesn't matter.

Your machine may spit out widgets that are plus or minus an inch. But when you set up the machine you set it up to the 1/16 regardless. Swapping all that to metric doesn't actually change anything other than the number the guy setting it up dials it in to.

[relaxing]

1/16” is just over 1.5 mm, so yes, the guy setting the machine in millimeters is giving you more precision. In the real world measurements aren’t just abstract figures you can move around losslessly.

I have a socket set in half-millimeter sizes for the absolute plague of cheap bolts and nuts that are being manufactured with obscene levels of slop.

[throwway120385]

He's not giving you more accuracy though. A machine that's accurate to 1/32" is accurate to .75mm. If those cheap bolts were in US customary they would still need to be in smaller increments.

[cucumber3732842]

You're missing the point.

The guy buying the widgets doesn't care because he's expecting a widget that's plus or minus dozens of the unit the machine is being set to. The setting is just as precise as it is in order to set the fat part of your output curve over the middle of your quality control pass range.

The machine might not even be calibrated in a direct measurement, it might be calibrated in a secondary measurement. Like tons of force or rpm or cycle speed or something that then translates to the dimension of your output part.

The units on machines mostly only exist for calibration. Beyond that they can just be made up "my amp goes to 11" type scales because they're so divorced from the outputs, either in precision (or are literally indirect as described above) that you "just have to know" that if you want a "X<unit>" widget you'll actually set the machine

Tons and tons and tons of stuff in our world is even intentionally spec'd out in this manner. A 14" tire rim is not 14, there's a tolerance. A 3" pipe isn't 3". These are all just nominal sizes. Just about everything in our world is nominally sized. A nut and bolt manufacturer doesn't care whether they're making 12mm or 1/2 on a given day. Those are just nominal sizes, arbitrary names, in their minds. It doesn't matter whether the factory runs on metric or imperial or something else because they're just shooting for an arbitrary number.

The only time your unit really matters is when interfacing with other parties and it only matters insofar as you need to know what each other are uses.