wood movement


Recently saw pix of a telephone stand made from maple with a mahogany top. The top was about 18" square - couldn't tell if it was one piece or a glue up but it was solid wood. It sat in rabbets notched in the tops of the legs and was glued ( doweled?) in the corners.
With two different species of wood and the top anchored to the legs, wouldn't that top be a candidate for splitting?
I'm thinking of building one. Usually I attach table tops in different ways, all so that it can move freely.
Thanx,
Vic
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Vic wrote: Recently saw pix of a telephone stand made from maple with a mahogany top. The top was about 18" square - couldn't tell if it was one piece or a glue up but it was solid wood. It sat in rabbets notched in the tops of the legs and was glued ( doweled?) in the corners.
With two different species of wood and the top anchored to the legs, wouldn't that top be a candidate for splitting?
I'm thinking of building one. Usually I attach table tops in different ways, all so that it can move freely
Recently saw pix of a telephone stand made from maple with a mahogany top. The top was about 18" square - couldn't tell if it was one piece or a glue up but it was solid wood. It sat in rabbets notched in the tops of the legs and was glued ( doweled?) in the corners.
With two different species of wood and the top anchored to the legs, wouldn't that top be a candidate for splitting?
I'm thinking of building one. Usually I attach table tops in different ways, all so that it can move freely
http://www.woodzone.com/properties.htm Certain species of mahogany are pretty darn stable. An 18 inch panel may move very little. I'd still allow for movement, just 'cause it's a good practice. Tom
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You sure the corners are actually doweled? Could have a screw in a slot to allow for movement and capped with a plug. Screws INTO end grain aren't the best way to go but for a small, light table ...
charlie b
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Good point Charlie - I "assumed" a dowel but it could be a plug.
Vic b ( no relation :) )
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legs
ways,
If it's doweled perpendicular to the grain on the top - safe. It moves, and presumably floats in the groove in the other direction. The wood moves across the grain.
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My guidebook (Wood - The best of Fine Woodworking) says that maple moves .3/12" and mahogany moves .2/12"
You said it is 18", so the differential motion is a max of 0.15". If they were cut at mid-moisture, are varnished, or in an air-conditioned/humidified room, it could be much less.
I don't see that as a problem, even if fully glued.
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Check your math. 0.2 per 12" is 0.3 per 18", not 0.15.

Even if your math was right, your conclusion is still wrong - 0.15" is more than enough shrinkage to break a panel that's not been attached in a way that allows it to move freely.
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Doug Miller (alphageek at milmac dot com)
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On Wed, 15 Jun 2005 00:41:09 GMT, Doug Miller wrote:

OK. The maple is 0.3 per 12 inches, and mahogany is 0.2 per 12 inches. They will move in the same way (both expanding, or both contracting). Doesn't that mean that the *relative* motion over 12 inches is the *difference*, or 0.1 inch? Then, over 18 inches, it would be 0.15 inch. This assumes two pieces are pinned at on one side, free to move at the other.
Do I misunderstand?
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snipped-for-privacy@none.invalid wrote:

My fault, I misunderstood. My main point still stands, though: 0.15" movement is more than enough to break a joint.
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Doug Miller (alphageek at milmac dot com)
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wrote:

Hey, is that you AlphaTurd! (No one else says I am wrong just to be obnoxious.) Is your problem with math or reading?
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Thanx all - good points to consider!
Vic
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You don't mention any aprons between the legs. If there are none - and the only thing connecting the legs together is the top - then I don't see how there could be any wood movement issues. As the top changes size, the legs would move with it.
OTOH, if the legs *are* connected by aprons - thus fixing the legs at a constant separation from each other - then it's only a matter of time before something breaks.
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Doug Miller (alphageek at milmac dot com)
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wrote:

top.
glue
legs
before
Good catch, Doug! I didn't mention that in the post. Yes, there is an apron about 3/4 down the legs. Couldn't tell how it was attached.
Vic
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...

Any chance you can point us to a picture of this table?
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