Help needed for stone insert in coffee table

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. This raises a few questions that possibly someone could help me with:
1) How thick should I make the granite/marble? The table top is 32" by 54", so I am planning to make a rabbetted frame with 4" wide rails and stiles using 1" thick mahagony. That leaves about 24"x46" for the stone. In addition to the rabbets, I am planning on using three 1x1's running across the underside of the frame to further support the stone. I'm guessing that the weight of the stone shouldn't be an issue, but maybe I'm wrong.
2) Any suggestions about where one can get a nice piece of 22"x44" granite of the right thickness for furniture? Chicago area? A friend already cautioned me to cut out an MDF template to give to the stone dealer to be sure that the size is perfect. Any other advice?
Thanks.
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I built a similar table but used tile. Tile set in a mortar bed. You may want to consider this so your stone is 100% supported. You could then also use granite tiles (1/4" thick and readily available). If you plan right you can use a 2x4 pattern with no cuts. If your too far along then the blue or orange store will cut for you.
My table has held up to 15 years of abuse, including 3 years in a dorm room!
A single stone would look cool though but I have no idea where you could get one except from a granite counter fabricator. Weight would probably be a huge factor though.
Have fun.
-B

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There's a huge raw granite piece outside our local home depot. The advertisement says that it's for a kitchen counter top. I'm sure they're contracting it out, but I bet you could get a cutoff piece or part of a broken counter or something for next to nothing.
brian
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On Mon, 25 Oct 2004 16:54:37 -0500, LStole

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

That's 2' squares of unsupported stone. Hmmmm..... Not how I'd do it.
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.
Some fool _will_ try to dance on top of this.
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.

Ha ! You're wrong.
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 bastard!

I like to buy mine second-hand. Fire surrounds in an architectural salvage yard that were broken in half during demolition are a bargain, if you can still use the smaller pieces.
I also live practically next door to a stoneyard with a real problem for spoilage in their yard (I wouldn't like to run a business that badly). If you can persuade them to let you walk around the stacks, make them an offer on the breakages!
A 9" angle grinder and a _good_ diamond blade is a reasonably good way to cut stone these days. It's incomparable to abrasive blades or the diamond blades of just a few years ago - both for speed, and for cut quality.
--
Smert' spamionam

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wrote:

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).

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.

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

Lay it on some plywood subflooring.

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

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

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

1" granite for this will weigh about 100 pounds.

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.
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