So many of you know what I do for a living. These past couple days I have been working on a startup on a mid-sized centrifugal chiller (815 tons). How does this correlate to machine shop? Well, we check alignment as well as soft foot on our machines before startup.
Here I am using a Starrett 196A6Z to check the alignment
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Is it in Cal.? 
When it was made 30+ years ago it was. Our tolerance on most of our couplings are 0.040-0.055" Thank god for flex couplings.
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I love seeing real world application of what we like to do.
that much? Why you could drive a truck thru that! (tiny truck). Most of my parts were 0.003-0.005".
Sometimes I even get that.
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The .040"-.055" I suspect is just to take up alignment errors for the rotating parts, that’s how much the flex coupling can deal with to be within alignment specification. More than that amount I assume would cause excessive wear or vibration.
The hole patterns themselves are probably .010"<
Shimming motor and compressor bolt down points to get within 40 thou sounds like hard work on equipment this size.
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Lol. Yeah, mis-alignment. TIR. That alignment is rim & face combined. The bolt holes themselves are tight, often we have to love tap them out.
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