On Nov 25, 10:58*am, "Ed Huntress" wrote:
...And concrete
grows (or shrinks; I forget) for decades after it's cast. It's not enough to
matter in building structures but it can be an issue when you're dealing
with thousandths of an inch.
Ed Huntress

I wonder if you could get around that by decoupling the ways from the
frame, perhaps mount them between clamping cap screws and supporting
setscrews and realign them to a straightedge before a critical job. It
would be like spotting and scraping, but quicker.

I've built a few instruments using that principle and found I could
hit micron accuracy as long as the screw seating surfaces were smooth
and lubricated and I left room for a wrench on both the pushing and
pulling screws at the same time, so I could slowly increase the torque
on both as the position readout approached zero.

My proof-of-concept demo to get permission was adjusting a 4-jaw lathe
chuck to within a micron. They brought me in as the electronic tech
and I had to prove that I could do the mechanical design and
construction of the lab prototypes as well.

jsw