ATM 3" F/6 and basics

["Dymicki, Krzysztof" <Krzysztof.Dymicki@hit.com.pl>]

Hi,

I started to play with mirror grinding. Because I didn't know, where to grab
a right blank from, I took a plate glass square 10 mm thin,
and broke from it a 8-sided 'pre-blank'. I have rounded it (mostly by hand).
The tool were two 3 mm plate glass squares. Also by hand broken and rounded
and glued together with epoxy. I know it is only a play and I do this mostly
for fun.
Would be nice to became truely right mirror from this piece of glass. Even
if not, experience counts also.
In nearest future I'm going to grind 6" f/8 10 mm thin mirror.
Here the question. From Mel Bartels homepagehe made succesfully: 

" 12" diameter x 3/8" center thickness, f/4, plate glass 
  20" diameter x 1" center thickness, f/4, fine annealed pyrex 
  30" diameter x 1 1/4" center thickness, f/4, fine annealed pyrex"

One could think, if he made succesfully  such mirrors then for 6" is
adequate (?) 3/16" center thickness - only 2 mm ? 
(1/2 from thickness from 12" mirror ) ? Does mean that, 10mm glass is OK
for 6" f/8 ?
Should tool from same glass be OK aslo ? Or will be better if I glue two of
such pieces together ?
What with astigmatism during grinding with such (10mm) tool same 10mm mirror
?

Thx in advance


Krzysztof Dymicki     Dzial programowania i rozwoju 
kdymicki@hit.com.pl,  tel (22) 5330 814, -815   

HIT Centrala Polska Sp. z o.o. 01-460 Warszawa , ul.Gorczewska 212/226 
hitcent@ikp.atm.com.pl tel (22) 5330 990, fax (22) 5330 829