[Caprirs]

Most VMCs made over the past 15 years will hold a few tenths positioning and repeatability when set up properly. However, in the real world, jobs with those requirements are rare so few machines are maintained to hold it. For example, whenever the machine gets relocated in the shop, it's not commonly re-leveled and trammed back in to being square. That isn't negligence, simply cost effectiveness. Just as fpworks mentioned, although the machine can be set up to hold tenths over two feet, how many shops can inspect such parts?

My experience (limited for sure) is that the machine will be very consistent and predictable. So even if a dimension is off, it will be consistently off and can therefore be compensated. It's the way the part is fixtured and the human who's loading the parts that is one of the biggest variables. Also, some machines and parts are more sensitive to temperature change, especially as the part gets bigger.

[werks]

For a couple of hundred dollars you can have a good service guy inspect a used machine. Have him/her run a ball bar on it.