Cutting Vermuculite Board

[JenniferB]

I have several sheets of 1" thick vermiculite board from which I'd like to make some fusing moulds. I particularly want to be able to fuse a composite of several pieces of glass into a disc or circle. I assume I can make the straight cuts for the outside edges with a chop saw, but how would I cut the 8" diameter circles I want in the middle?
Jennifer

[Brad Walker]

Anything that would cut wood will cut vermiculite board. So you could use a jig saw or any similar tool.

[Marty]

I'd use hand tools over electric- the stuff cuts like butter and the electric tools throw up an awful lot of dust.
For the circle, drill a starter hole and then use a jig saw.

[JenniferB]

Thanks Brad and Marty,
I'll try to cut it with a hand jig saw. I'm a bit apprehensive about cutting a smooth circle (I don't want the glass disc fused inside it to have 'wobbly' edges) but I'll do a test piece first. Should I use a hardener on it once I've cut it?

[Marty]

I've never used hardener on VB. Once you've cut your circle you can sand the rim smooth with coarse sandpaper.

[Bert Weiss]

I once made a putty by mixing vermiculite board sanding dust with colloidal silica hardener. This was used to patch a Best Mix mold with pits in it. It could also fill gouges in a kiln shelf. The putty hardened and was sand-able.

[Brad Walker]

I once made a putty by mixing vermiculite board sanding dust with colloidal silica hardener. This was used to patch a Best Mix mold with pits in it. It could also fill gouges in a kiln shelf. The putty hardened and was sand-able.

Jim Wiles (Neuex) also sells a product that can be used to repair vermiculite board. I suspect it would have other applications as well.

[Ron Bell]

I cut 1 inch VB with a table saw but I have never had good luck cutting good inside circles. I usually just rough the circle and use a wood rasp to clean it up. Remember to wear a respirator, that stuff puts off a ton of dust! As an aside, I have been using VB for my kiln shelves for over 15 years now and I am convinced that I get more even heat distribution and can work at somewhat lower temperatures in my big JK kiln.