as a mechanic working in a hodgepodge US/EU factory line, I have to suffer through always carrying double the tools to service metric and SAE machines. and after so many years in the industry, I still slip up and say 3/16 when I mean 3/8 sometimes, because fractions are a shit system for wrenches.
oh, and some of our linear encoders readout decimal-feet, because fuck it, why not?
it's very easy to enter wrong numbers on a calculator, but you need some basic reasoning and familiarity to know when an answer is off, and you need to start over
I'm trying to take a more active roll in training new machines operators at my job, and it's only because the current training manager actively does the opposite of 90% of the stuff on this list. I'm getting tired of being called in to "fix" stuff that's just an error of bad training.
rock and stone!