Jack,
See IPC-2221 page 25, Table 5-1 (Board Thickness).
This isn't exactly what you are looking for, where you should look would
be a specification
for your frame, such as VME, PCI etc. You need to specify according to
what you
are inserting the card into, and its tolerances. I think the VME spec
is .063 +/- .008
Karl