When I went into the MGM Studio Machine Shop as an apprentice, I was put in charge of the tool crib and was immediately put to work on a 17" X 54" Cincinnati engine lathe, facing, drilling and reaming PVC roller blanks, which would become film rollers for the film lab.
After a few weeks of fighting with bores galled by heat from the reamer, I started experimenting with plunging a brazed carbide boring bar to a rough diameter, then a second time to finish size. When I approached the boss and showed him what I was doing, he said that was great, but could I hold tolerance? Tolerance was .751 +.002/-.000. I showed him a stack of roller blanks all well within tolerance and no rejects. He liked it, but cautioned me that, unlike aerospace, in that machine shop I was responsible for QCing my own parts and if I produced one bad part that caused the shut down of a film developer or a delay on a movie or TV production, at best it would cost the company tens of thousands of dollars and my apprenticeship would be over.
Union or not, if you didn't produce good parts, you didn't last long in a studio machine shop.