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post #1 of 10 Old 03-01-2011, 09:53 PM Thread Starter
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Table top

Best way to keep a big table top from warping ? Top will be 40x80x2 in with 5in. aprin not sure thats rite word
thanks tator
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post #2 of 10 Old 03-01-2011, 10:02 PM
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Keeping boards as narrow as possible, and alternating grain patterns. Finishing the top and bottom. Cleats can be put in across the grain. They can't be glued and screws need to be in slots to allow movement. After that, if you try to restrain movement, it will probably crack.

What kind of wood you planning on?
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post #3 of 10 Old 03-01-2011, 10:32 PM Thread Starter
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table top

they wont red oak, would another wood be better ?


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post #4 of 10 Old 03-02-2011, 05:20 AM
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http://www.woodworkingtalk.com/showt...ferrerid=16743

Here's a thread I started on a similar project.

White oak would probably be better. On the table I'm building, the client specified red oak.
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post #5 of 10 Old 03-02-2011, 05:58 AM
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Agree with Brink. A few other ideas. If you have the time, rough cut your wood slightly oversize, stack and sticker it for a few weeks in the conditions the furniture will live. Then mill the wood to final dimensions and sticker it again for a few weeks. Always start from the beginning - use the jointer to flatten the boards then use the planer. When possible, try to take the same amount of wood from each surface. Do this for both millings. Make sure the wood is restrained while it is equibrialates. Every time you mill wood it exposes a new surface to the environment, and looses or gains some humidity. The stickereing process allows the wood to equilibrate under restraint and helps prevent warping. This is often impossible since you have what you have, but constructing the piece in a shop thatís about 7% relative humidity will help, since the average indoor RH is about that.

Donít count on the fact that the wood is Ďkiln driedí because itís moisture content will equilibrate to the environment. Wood will gain and lose moisture forever, and that is what causes warpage later. It can happen 100 years after you make the piece.

Then finish both surfaces of the table the same - same finish, same number of coats. Using a sealing finish like varnish or poly also slows down water exchange.

A breadboard end will also help if the design permits.
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post #6 of 10 Old 03-02-2011, 08:42 AM
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I agree with the steps to be taken. If you could use QSRO (quarter sawn Red Oak), that might help. Or, if you use Red Oak plywood with a solid wood edge, you won't have a movement problem.

You can't prevent wood movement, cupping, or warping. All you can do is follow some steps that might make it less likely to happen. Sometimes it's difficult to acclimate the stock where it will live as furniture. It will likely be worked in a shop somewhere, and then delivered/moved to its final resting place. It could go from a 98% ambient humidity to 50% humidity condition.

In Florida, that's what we have to deal with. Problems could also arise when the furniture has been acting real nice and behaving. Then it gets moved to a different part of the country with different weather conditions. The problem never really goes away.








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post #7 of 10 Old 03-02-2011, 09:07 AM Thread Starter
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table top

Thanks for the imput. This table will be in heat in wenter and verry little ac in summer central illionis.

My shop runs 35-45% , I can run the wood thru Daron kiln to get it to 7% fi thats what i need to do

thanks tator

God bless
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post #8 of 10 Old 03-02-2011, 09:59 AM
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Quote:
Originally Posted by tator234 View Post
. . . . I can run the wood thru Daron kiln to get it to 7% fi thats what i need to do . . .
I can't add anything to the great advice you've been given above. But as to kiln drying of course you should considering where it'll be placed in service. Also, once you take it out of the kiln if there's going to be any substantial amount of time between when you take it out and when you work it, you can make dead stacks and wrap them completely with stretch wrap and the wood won't absorb any moisture at all while wrapped.

And with your shop's low RH that's very much in your favor once you do start to build the piece.







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post #9 of 10 Old 03-02-2011, 06:48 PM
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Originally Posted by cabinetman View Post
In Florida, that's what we have to deal with. Problems could also arise when the furniture has been acting real nice and behaving. Then it gets moved to a different part of the country with different weather conditions. The problem never really goes away.

.

Imagine what will happen when a piece gets moved from Florida to Arizona!
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post #10 of 10 Old 03-03-2011, 12:06 AM
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Originally Posted by TGRANT View Post
This is often impossible since you have what you have, but constructing the piece in a shop thatís about 7% relative humidity will help, since the average indoor RH is about that.
I realized I expressed myself badly in my previous post quoted above. I meant to write that the shop humidity should be such that the moisture content of the wood would be about 7%. That's something close to a 30-40% relative humidity in the shop at a typical room temperature, and thatís what typical indoor relative humidities run in fall/winter/spring (though there is a lot of variation, but close is good enough in this situation). Summers are higher unless the air is dehumidified. Sorry about the confusion.
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