I have a bunch of military mirror assemblies...two per unit at 45 degrees which are mounted by through-fasteners to a metal base. These are second surface mirrors, the front surface is flat to 4-5 fringes across the 4.25" square face. The 2nd surface looks silvered and is painted over. I'm strippng the backing off one to assess for strain and flatness.
At 4.25" M.A. it looks like I could core out 3" m.a.secondaries. The thickness is .68" so it's about 1:6 ratio. I don't know the glass type but it is water clear and I expect it is a good crown glass.
I've cored mirrors normal to the surface, but not at 45 degrees. I see sketches of setups with the glass invested in plaster...cover glass balsamed to protect the face, cored at 45 degrees with a rotating tube and grit.
Now that diamond coring bits are common, has anyone used them for this sort of project? I have 10 individual mirror pieces.
The plan is to cut them out @45, block them on a silica runner, fine grind and figure them as a flat. Angle is not optically critical. Would be nice to make good secondaries.
What comes up typically when blocking pieces like this? I have Horne, but find no discussion of that detail. I have mounting wax, blocking cement..