When I worked at a smelter Myself and my crew had both Imperial and metric tools.
We used both every day in doing our job.
Alot of the old timers on crew talked in imperial measurements.
We had to refit, refurbish and recalibrate the casting technology.
As you can imagine the need for accuracy was vital.
Having and using both imperial and metric systems was never an issue or underminded the safety or the accuracy of the work.