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Help! Warped table top

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Forum topic by arlodaniel posted 11-21-2013 04:41 PM 2192 views 2 times favorited 45 replies Add to Favorites Watch
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arlodaniel

3 posts in 306 days


11-21-2013 04:41 PM

Topic tags/keywords: question traditional

Hi! I am brand new to lumberjocks, but have read many posts with great interest and am continually impressed by the level of knowledge and willingness to help that I’ve noticed!

I’ve just completed a farmhouse table based more or less on these plans:
http://ana-white.com/2012/11/plans/farmhouse-table-updated-pocket-hole-plans

I used kiln-dried fir, and allowed the lumber to acclimate to my apartment for a week.

And yet, in preparing to attach the tabletop to the base, I discovered that the tabletop (made of 4 boards joined with pocket screws and capped with breadboards) is warped such that the two opposite corners float above the legs:

I thought I could simply clamp it down and screw it in… but unfortunately as I clamp the opposite corners, rather than pulling the tabletop down to meet the base, it lifts the base up to meet the warped top, so that one of the legs ends up about an inch off the floor!

I could just put a shim under that leg, but it’s a big enough distance that the table will then be on a noticeable angle; I suppose I could put 1/2” shims under the two opposite legs but, again, not ideal.

Thoughts I’ve had:

1) Leaving the warped wood on the cement floor overnight with weights on the corners. -Did that; ineffective
2) Wetting / steaming the concave side to make it expand -I don’t really quite know how to do this, especially as the warp is on an angle so I’m not certain where to apply the water. And I don’t think I have the necessary tools to steam it.
3) Kerfing? -I don’t know much about this option, but it sounds maybe promising? If I could kerf the bottom correctly, maybe I could more easily clamp it down and screw it on without it pulling up the legs? But, again, I’m not clear on exactly how / where to make the cuts; cutting corner-to-corner at an angle across the boards somehow doesn’t seem right. (I have a skillsaw, by the way, no table saw)
4) Disassembling -I have a feeling I will get this suggestion, but I’m not going to do it. First of all, I don’t even see individually warped boards, just the whole thing seems cupped. Secondly, I joined it as straight as I possibly could the first time, taking hours with each joint to make sure that it was as flat as possible before I put in the pocket screws; it’s not going to be any better next time around. Thirdly, this project is to be ready for Thanksgiving next week—and I’d rather just suck it up and shim it than take out fifty screws and scrape out the epoxy/sawdust filler I used in the seams and probably have no table next week :(
5) Anything else?

Thank you so so much for any advice or suggestions!!


45 replies so far

View a1Jim's profile

a1Jim

112104 posts in 2235 days


#1 posted 11-21-2013 04:48 PM

Your construction does not allow for wood movement ,so when the wood moves due to atmospheric conditions it is going to crack ,warp or twist. Pocket screws is not the best way to connect a table top.

-- http://artisticwoodstudio.com Custom furniture

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a1Jim

112104 posts in 2235 days


#2 posted 11-21-2013 04:49 PM

Here’s some info that will help
http://www.finewoodworking.com/media/TabletopsFlat.pdf

-- http://artisticwoodstudio.com Custom furniture

View Micahm's profile

Micahm

135 posts in 390 days


#3 posted 11-21-2013 04:52 PM

I don’t know much, but had and idea. If you could take it somewhere and the keep pouring boiling water on it and get a clamp to clamp it down little by little. I don’t know if it would work, as I am a beginner woodworker also, but just had that idea. Not sure if you would be able to do that though.

-- The things I make may be for others, but how I make them is for me. - Tony Konovaloff

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a1Jim

112104 posts in 2235 days


#4 posted 11-21-2013 05:00 PM

Unfortunately there are lot of plans out there buy companies and individuals that don’t know what their doing, even a long standing woodworking tv show does not build things taking wood movement into consideration . Just because pocket screws are an easy way to accomplish joinery does not mean they can be used for all applications .

-- http://artisticwoodstudio.com Custom furniture

View Rick M.'s profile

Rick M.

3978 posts in 1038 days


#5 posted 11-21-2013 05:11 PM

Kerfing would help as it releases stress but I would save it as a last resort. Try moisture first. You might try laying it concave side down in the grass for a few hours. I would not shim it as that will look like failure.

-- |Statistics show that 100% of people bitten by a snake were close to it.|

View Tennessee's profile

Tennessee

1447 posts in 1172 days


#6 posted 11-21-2013 05:57 PM

You’ve made two mistakes that I can see. First off, Jim is right, you have to allow for movement. If you look at the very first picture in that pdf. file he listed, you can see how that construction will allow for movement.

But let’s talk about the movement itself, and some ways to minimize it.
It starts with picking out the wood.
Flatsawn wood will warp the worst. This is when the board is simply lopped off the log, with no consideration taken of grain direction. I’ve bought wood like this many times from local people who own portable tree bandsaws, and to be honest, I just know about 15-20% of it will warp way more than acceptable unless I rip it down and try to keep it flat and stacked.

When you pick out your timbers at the lumber store, which is what these look like on your project, you should have the growth rings on the ends of the boards come in and leave the same side at about 45’. Think half-moon. This is basically quartersawn. That’s about the closest you’ll get with big box lumber. Then, when you put them in a row as your project calls for, you MUST flip every other one, in other words have rings facing up, next one down, and so on. This will not cure all warp, but it will cause the boards to fight one another and keep some semblance of order. The end board is what holds all of them together, and there is a reason why people use dado joints to put these on, not pocket screws. It allows for a little movement, and holds the boards firm in the middle of the board. Pocket screws come in from under, attacking only one side of all boards. They don’t allow for movement, so the whole top starts to move.

At this point, I think you have to think in terms of taking off the breadboard ends, making sure every other one is flipped, and start over.
Then you should attach it to the lower stringers and legs with the attachment blocks you will make like the ones in the picture shown in the article Jim listed. Sorry…

-- Paul, Tennessee, http://www.tsunamiguitars.com

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Rick M.

3978 posts in 1038 days


#7 posted 11-21-2013 06:01 PM

Many people believe that alternating growth rings is a myth, I’m one of them. Well I shouldn’t say myth, but that by alternating you end up with warp instead of cup or bow which are easier to remove.

-- |Statistics show that 100% of people bitten by a snake were close to it.|

View Tennessee's profile

Tennessee

1447 posts in 1172 days


#8 posted 11-21-2013 06:04 PM

Interesting. I have to be honest, I’ve never talked or met with a woodworker that thought that, until I read your post. I must have dozens of articles and books where they talk about alternating growth rings. Well, people also used to think the world was flat, so maybe we’re all wrong.

-- Paul, Tennessee, http://www.tsunamiguitars.com

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Tennessee

1447 posts in 1172 days


#9 posted 11-21-2013 06:07 PM

Ah, you changed up on me while I was typing…I would agree that it is not a cureall for the warps. It is much more suited for cupping. But to me, if two or three of the boards all had the growth rings facing the same way, it would be easier for the multiple cuppings and any warp to work together.
It’s not guaranteed, but I bet he got the boards all off the same stack at a big box store. That makes their chances of coming off the same set of logs higher. They would all share the same warping/cupping tendencies.

I guess I’ll just keep on alternating. Old habits die hard.

-- Paul, Tennessee, http://www.tsunamiguitars.com

View wanderingwest's profile

wanderingwest

17 posts in 327 days


#10 posted 11-21-2013 06:16 PM

Seeing the doug-fir here made me think of crowning the apron which is something I would do when laying joists or building trusses but never thought about with a table. Would that work too? Just a thought.

View Tennessee's profile

Tennessee

1447 posts in 1172 days


#11 posted 11-21-2013 06:18 PM

If you mean re-leveling the apron to match the top, that would be something I’ve never seen done.

-- Paul, Tennessee, http://www.tsunamiguitars.com

View Rick M.'s profile

Rick M.

3978 posts in 1038 days


#12 posted 11-21-2013 06:23 PM

I’ve never bothered alternating growth rings in the half dozen or so tables I’ve built nor in the benchtop and the only one that bowed or cupped was a small side table that someone placed over a heat register. The heat dried out the bottom and cause the top to bow. That was also my first table and I used 3 coats of finish on the top but only 1 sealer coat on the bottom. Had I finished it properly it might not have bowed at all. Basically I believe that orientation of the growth rings is trumped by many other factors.

-- |Statistics show that 100% of people bitten by a snake were close to it.|

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wanderingwest

17 posts in 327 days


#13 posted 11-21-2013 06:26 PM

I mean using the warp of the apron to counter the warp of the top and pull it straight. There’s a ton of situations in framing a home where you would us that technique but I just never thought of it being an issue with furniture. I just thought of it seeing the soft wood here.
http://greenwoodconstruction.us/%20/191/crowning-your-lumber/

View a1Jim's profile

a1Jim

112104 posts in 2235 days


#14 posted 11-21-2013 06:29 PM

I think the article in fine woodworking covers the subject very well .I think it’s important to know that although selecting quarter sawn wood will help it does not element wood movement all together and even though the school of though has been that it’s alternate plain sawn wood with alternating up and down end grain pattern it is not always necessary and still does not stop wood from moving,it’s more of a precaution to help keep tops some what flat. I know others have offered an answer to your question about flatting your warped wood out but it still won’t help if you don’t let your wood move. One of your above questions was if having your wood on a concrete floor can affect your wood,the answers is yes. The reason being that concrete holds a good deal of moister and laying a board directly on a concrete floor inparts moister to one side of your wood while the other side of the wood is dried by the air,this is exactly what causes wood to warp. I’m not trying to give Paul a hard time but quarter sawn wood has it’s grain at 90 degrees on a boards edge like the photo below

-- http://artisticwoodstudio.com Custom furniture

View Tennessee's profile

Tennessee

1447 posts in 1172 days


#15 posted 11-21-2013 06:35 PM

You are right, Jim, but when was the last time you saw a board like the one you show in a pile of fir at your local HD or Lowes? Your picture is true quartersawn. The banana ring pattern is usually about as good as it gets with these fast growth trees they cut up now for “kiln dried fir”.

-- Paul, Tennessee, http://www.tsunamiguitars.com

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