A sphereometer about 20-33% of the mirrors diameter is nice to be able to check that the surface is uniform and one is not grinding astigmatism into the mirror.
Enco has dial indicators that measure .0001" with a travel of 0.100 " for $50-60.00 That and a base with 3 holes drilled equidistant around a hole in the center for the dial indicator, and then epoxy ball bearings into each of the 3 holes for little feet.
Something like this will provide more than enough accuracy for all but the most demanding work.
Hope that helps, Preston
Enco has dial indicators that measure .0001" with a travel of 0.100 " for $50-60.00 That and a base with 3 holes drilled equidistant around a hole in the center for the dial indicator, and then epoxy ball bearings into each of the 3 holes for little feet.
Something like this will provide more than enough accuracy for all but the most demanding work.
Hope that helps, Preston
