For glass thickness, the thinner you go, the more flex you get as you do your grinding, etc. You also run into the problem of the center being significantly thinner than the edge which can be a problem. 1:10 is the normal thickness for lenses and is pretty solid. 1:20 gets to the point where the glass may want to be slumped to the approximate curve before grinding and things like astigmitism and lumpiness of the surface from poor support get to be real problems. 1:30 is at the point where things get really strange and you need really mount the glass into fixtures to even think of getting a smooth surface.
The glass for table tops is usually tempered but you can get it before the tempering operations are done on it, it will make decent mirrors.
The process of making round glass blanks is called trepanning and is done with a ring of metal and carbide grit turning into the glass. Other methods can be done including wire cutting and high pressure water jets, all of which can be fairly expensive.
You may want to go to Dan Cassanro's site and see what he's got there. He's got a bunch of 7/8" glass that he's cutting up.

• Plate Glass - johns - September 21, 2001 - 02:21 UTC
  • Plate Glass - bobmay - September 21, 2001 - 17:50 UTC