With a buscuit or fly cutter on a drill press.
>2. Grinding it? Anything different?
No.
>3. What is the minimum thickness to diameter ratio to prevent sagging?
6 to 1
> Ie, with my .5" thick glass, can I expect intolerable results from
> an 8", 9", 10", ... blank?
Depends on the annealing. This is the crucial factor. Use two polaroid sheets to sandwich the glass with a light shining through the assembly. Rotate one sheet and observe the darkening/lightening. If it's smooth, annealing is good. If it's spotty or blotchy, annealing is poor.
> I know with glass this thin, that I'll have to go with a really
> slow f/ratio.
>4. Got any clever cell designs to prevent sagging?
Shag carpet has been used to good effect, even with fast f ratios.
>5. Am I crazy to even think of attempting this?
Not at all! Ultra-light optics are a very desirable goal.
>6. Got a means to melt it all down and spin cast it into a 1 meter
> class blank with pregenerated curve? ;>
>
>http://www-name.engin.umich.edu:8001/people/seguin/astronomy/MirrorLab/MirrorLa
>b.html
>
>
>What worries me is the thickness and how I'm going to get it cut
>into circles.
Buy a fly cutter for $20 and do it on a drill press.
>
>Oh, I forgot to mention, that I want to do this inexpensively;
>I cannot afford most pyrex blanks, otherwise I would simply go
>that route.
>
> Thanks, Ralph
-- Steve Strickland Lensnut@tpoint.net