Re: [ATM] cutting a big piece of plate glass into mirror or toolblanks

["Bob May" <rmay@nethere.com>]

I too have done a fair number of pieces of glass inot round
mirror blanks.  Most of my work ha been with three quarter thick
glass but the process is still the same although a bit faster.
Largest that I've done was 13.1" and that took a fair bit of
energy to do.  One guy that did a mirror in the class did a
sixteen inch byhand and he said that he'd never do it that way
again!  I use several layers of plywood for larger mirrors and
some two by stock for smaller mirrors and put roof  flashing
around it with a small gap between the ends.  Do backwards teeth
in it about every four inches or so to drive the grit down and
then start turning it with something.  Smaller stuff goes on my
HF drill press while larger stuff goes on Peter's version of a
MOM which will drive a trepanning tool at the bottom of the
shaft.  It seems that the steel goes away at about a tenth of the
speed of the glass.
The first time you use a tool, you will find that it often won't
track at the beginning.  Get agressive with the leading edge to
make it track and things will be better.
Don't try to uuse your coarsest grit  as you will get a more
tapered edge than with finer grit.
Bob May
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