Once you get down to below 1/1000 of an inch or so, you start to notice that metal is really like playdough. it squishes out in all directions when you clamp it, it springs back when you cut it. it is never exactly the same shape after it has been handled.
Just another thing that adds to the difficulty of super high precision work.
Yup. I often refer to aluminum as “rubber” when chasing that last few thau while machining. I do this to remind myself and others to have the right perspective and expectations when approaching things at this scale. Just because the machine displays four digits after the decimal point it doesn’t mean you can actually cut at that level.
You can use an optical flat. Interference fringe patterns will tell you how a surface that was cut perfectly flat on a machine becomes bowl shaped when you unmount the part.
Just another thing that adds to the difficulty of super high precision work.