Ben Jackson wrote:

Ok, this is a stupid question, but are the inside faces of a machinists
square supposed to be square, or only the outside faces? Or, put another
way, are the blade and base faces both parallel?

I've got the old "never take two clocks to sea" problem -- I've got two
squares and I piggyback them and I can see light between the blades.
So now I don't know which one is off...


If you have access to a surface grinder with precision angle plate then
clamp the short leg of the square to the vertical face of the angle plate
so the long leg is horizontal, and take a cleanup grind (very light) on
the long edge.

If your square is out, that is.

GWE