From: Don Bates 
To: atm{at}shore.net
Reply-To: Don Bates 


Help! After a very frustrating and lengthy polishing session on my 10"
f6.6 plate glass primary, I have decided to drop back and punt to fine
grinding. There are several long scratches on the mirror, and the center
never polished out properly due to poor center contact with a hard lap.
After scraping all the pitch off the back of the original plaster-based
grinding tool, I discovered to my horror that one of the edges of the
plaster surface had buckled, cracking one of the 1"x 1" tiles. I
think I can repair it by pressing with a clamp and using epoxy to mend the
crack. But here are my questions:

1) Will the altered surface of the tool damage my mirror during a final
re-grind with 25 and 5 micron emery? I think I can get it close to the
original shape, but I'm sure there will be a slight difference from the
original curve.

2) If the cracked tile creates a defect in the mirror surface, can it be
corrected during polishing?

Thanks for any insight you can provide!

Don

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