To: "Peter" ,
, 
From: tkrajci{at}san.osd.mil
Reply-To: tkrajci{at}san.osd.mil


> Please explain a bit more about the aluminum tool. I'll be hogging out a
16"
> soon (by hand) and I'd like to try an aluminum tool. You mentioned it
should
> be made to the desired curvature of the mirror. Can I do this on a lathe
by
> simply trimming or beveling the ends? What size should the tool be
relative
> to the mirror? Should I do the hogging out with mirror on top or TOT?

The alu. tools that Jack Schmidling made for me where turned on his
lathe...every inch radius or so of the tool was turned to a different
height, which approximated the desired curvature in a stepped fashion.  I
then had to spend some time at 120 (maybe 80, I no longer remember) grit to
do a decent job of mating the tool to the blank.  (The blank had been
hogged out previously, or came molded/pregenerated.)  If you are careful,
you can generate the curve on your slid alu. tool with your lathe at home. 
(Or mold a dental stone version, and then 'tile' it with 1/4 inch
aluminum.)

My tools for smaller mirrors were full size (4 1/4, 6, and 10 inch).  For
my sixteen inch mirror I used a ten inch alu. tool for all grinding (the
blank came pregenerated).

As for hogging out the mirror, I recommend TOT, but my blanks came molded
or pregenerated, so I can't commenet with any real experience in this
matter.  However, for most of my mirrors, from 4 1/4 to 16 inch diameter, I
did almost all (or 100% in the case of the 16 inch) with TOT...for
grinding, polishing, and figuring.

Tom Krajci
Tashkent, Uzbekistan

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