At one point, the precision claimed for that brute was claimed to be better than the best measuring tool available. (Which sparked a sort of arms race between the tool operators and the metrology team. . .) The work envelope was/is something like 2% of the total volume of the tool. There was a requirement that if an operator had to go physically touch anything on the actual tool, there was an extended wait period while the thermal and humidity disturbance from his/her visit propagated through the room, tool and workpiece before machining could be restarted.
The thing was on a truly impressively thick slab laid over a set of equally impressive compacted, washed sand sub-grade in a cleanroom inside a (very tightly controlled) environmental chamber in a dedicated building. The thing is an absolute edifice!
Things haven't changed much in the truism, either. . . Witness the LHC for further proof.
