Was: Linear rail, accuracy in general

Hi,

I noticed on this thread someone mentioned big high precision machining
centres that have thermal management etc to keep them at real close
tolerances at great precision. I remember seeing the working and result for
how much a lump of steel extends for such and such a temperature rise and
seeing how great it's effect was at these levels. But doesn't the wear on
the machine's tooling contribute even more to inaccuracies? I mean the wear
on a tool over tens of hours machining must be more than a few microns
easily. Yay or nay? Please don't tell me the machine can factor in for tool
wear? : )

Thanks,
John H.