ATM boring blind holes

[Ina Ron Lippard Renaissance Reproductions <renrepro@surfglobal.net>]

   C'boring a piece of glass? Interesting problem. I agree with Stan on 
this one. Two saw cuts
and then take a 3-corner file and broaden them into wider V-notches. Use a 
soft metal such
as brass, or better yet cast iron. Let it dwell in the cut until it starts 
to screech,(3-5 seconds).
Be sure the work is held snugly without any rocking. Hard,thin rubber or 
cardboard works.
DO NOT CLAMP IT DOWN.Moderate side pressure will do.Add a drop of liquid 
soap to the
slurry occasionally for lubrication. This is how I did Nate's 4" 
plate-glass blank.
good luck!
regards, Ron