"Andy Dingley" wrote in message
...
On Mon, 25 Oct 2004 16:54:37 -0500, LStole
wrote:

I'm designing a mahagony coffee table and would like to have a wooden
frame with a stone insert -- preferably a green granite or marble --
for the table surface.

1) How thick should I make the granite/marble?

The thickness it comes. Go talk to your stone supplier, see what they
can offer, see what it weighs and take their advice.

Yep, Find this out first. An inch should be sufficient. Granite is far
stronger than marble and won't stain or get eaten by mild acids (wine for
example).

You don't get much choice over stone thickness, and you have no
control over the exact thickness compared to the nominal. The mason
can probably saw it to any size you want, but that thickness depends
on how the quarry supplied it. If you're lucky it will be vaguely
parallel surfaced, but I wouldn't count on that (certainly not for
cleaved stones, like slate).

Actually, most of the granite I see for countertops is very uniform in
thickness. Slate certainly does vary, but the granite should offer two
parallel surfaces.

There is no way I would begin making a
wooden carcase for any piece of stone until I already had the stone in
my workshop and could measure it.

Talk to your stonemason about edge finishes too. A small chamfer
allows you to raise the stone above the frame level, which looks
better.

Absolutely.

For a 4'6" long slab, you're probably looking at a minimum of 1".
Generally I'd prefer 1/2", just to keep the weight down. For buying
new granite, my stock choices are 20mm or 30mm. Silestone (a
maunfactured stone) comes in more thicknesses, down to about 1/4".

I think he said 46" not 4'6" but what is 8" among friends?

The table top is 32" by 54", [...] I am planning on using three
1x1's running across the underside of the frame to further support the

That's 2' squares of unsupported stone. Hmmmm..... Not how I'd do
it.

Lay it on some plywood subflooring.

I have no real idea what I'm talking about here - someone with serious
knowledge of the stone can design you a cantilever that won't break.
But _my_ practice (on anything more than a foot square with a
replaceable tile) is to build a plywood sub-top all the way across the
tabletop, lay 3mm polythene foam floor underlay on that, then lay the
stone on top of that. The plywood is sized to not sag appreciably
under any reasonable load, and the foam is just to couple across any
surface irregularity. I have a horror of unsupported stone cracking.

You could do without the foam. It just lets the stone flex a bit more.
Flexing is bad.

Some fool _will_ try to dance on top of this.

If people are really going to dance on it then use a steel plate.

Incidentally, a couple of large circular holes sawn in the plywood
make lifting the stone out for transport _much_ easier. Even granite
is very easily chipped on the edge, if some fool tries to lever at it.

Of course. You will use these when you first install the stone.


I'm guessing that the weight of the stone shouldn't be an
issue, but maybe I'm wrong.

Ha ! You're wrong.

1" granite for this will weigh about 100 pounds.

You've got to not only make this thing, and make it usable in service,
but it also has to be deliverable / carryable upstairs / installable /
relocatable when they move house. Stone's a *******!


2) Any suggestions about where one can get a nice piece of 22"x44"
granite of the right thickness for furniture?

This depends where you live. I can find it from dozens of sources where I
live. You don't want to ship it. Find someone local.