Surface table alternative?

if you can find genuine "plate" glass from a shop window, or a large glass shelf, this was mechanically ground and polished both sides for absolute clarity and lack of distortion, so it should be near as dammit for most purposes. plate glass is usually 1/4"or more thick. Float glass is made by floating molten glass on a long tank full of molten tin, so that all the imperfections melt out and gravity provides the flatness. the problem is that it is a bit on the thin side and can flex a bit under pressure unless it is adequately supported. I have used a couple of 18" square pieces of plate glass for surface plates for many yyears, with no problems, and a check using the "best straight edge and a light" method remarked on above shows them to be still just about perfect. I use another peice as a lapping plate for carburretor and manifold flanges that have warped. Works a treat!

Phil

How long has float glass been around? I'm sure I saw the process being explained on Tomorrow's World when I was a kid.

Neil

I seem to remember that Pilkington's invented it in the 1950's. (I stand to be corrected on this)

Dennis

I don't mean to be provocative with this but given the relatively low-cost of small, imported granite surface plates, why do people go to so much effort to find substitutes?

I have one 12" x 9' x 2" which is adequate for everything I do and cost me less than a number of my cutting tools. It's (relatively) light and not only is it way within my needs for flatness, the faces are also parallel. So I can lug it onto the mill table to give me a decent flat surface for alignment checks. It can be a little cramped on some jobs but it's never stopped me doing anything.

I just checked and my local (Canada) supplier isn't listing this one any more - although I know it's still available from other sources. They are selling instead, one that is 18" x 12" x 3" for $40. So I guess the smaller one would be worth around $25 at that rate.

Because we're mean?

Russell