# Warped tabletop



## cgp4312 (Sep 20, 2012)

I am making a new kitchen table that is solid cherry with breadboard ends when I glued the table top it was dead flat but when I unclamps it it slowly started to warp and is now warped bad if I clamp one side down the other is about 1" off my workbench. Is there any way to fix this and why would it warp like this all my wood was between 5-7% moisture to thanks for the help


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## Steve Neul (Sep 2, 2011)

You might try wetting the cup side of the top with water and see if it flattens. If it does I would attach a skirt to the table as quick as possible before it curls up again. Cup warp is normally caused by an imbalance in the moisture content from one side to the other. If it works be sure when you finish the table you seal the underside as well to keep moisture from the air out of it.


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## cgp4312 (Sep 20, 2012)

Ok I will try that and I also haven't put the breadboard ends on it yet do you think when I do it will help straighten it out or will it just now the ends to


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## Steve Neul (Sep 2, 2011)

The breadboard end is suppose to help prevent the top from warping. I would wait until the top is flat before you install them. Anyway when you wet the table it will cause the table to expand a little so I wouldn't fasten the breadboard end just yet. I would just put it on and put a single screw in the center for a couple of days to let the top shrink. Forgive me for saying this but I don't know your experience but the breadboard ends are never glued on. They are just installed with a few screws to allow the top to shrink. If it was glued and the wood shrunk it would cause the top to split. Some folks also elongate the screw holes to make sure the screws don't make the top split.


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## oakcutter (Jan 23, 2013)

*Table Top Warp*

I too am in the process of building a table top and am concerned about keeping it flat. My guess is there is a fine line between too much clamping force and not enough. So question is, how does one know what's enough. I have tried glued up panels before and wondered if I was forcing it to warp/bow because of too much pressure. Any thoughts?


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## BZawat (Sep 21, 2012)

oakcutter said:


> I too am in the process of building a table top and am concerned about keeping it flat. My guess is there is a fine line between too much clamping force and not enough. So question is, how does one know what's enough. I have tried glued up panels before and wondered if I was forcing it to warp/bow because of too much pressure. Any thoughts?


Not to aid in your hijacking of this thread, but I can offer you a few suggestions. 
First, the joints between boards in your panel (or tabletop) should fit together with no gaps before they are clamped. If you're clamping tight enough to pull gaps in the glue joints together, you're clamping too tight and it certainly could cause warping. Clamps just hold the panel together till the glue dries. 
Second, you should maybe consider using cauls to aid in keeping your glue up flat and properly aligned. They are easily made from any chunky stock you may have laying around. I used spruce framing lumber for mine. 

As far as straightening a warped top, good luck man! I've never had any success at it, short of some creative planing haha. But then you lose thickness so...


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## Smith Brother (Dec 9, 2012)

I am betting you will need to cut down the middle of your glue joints and start over. 

When clamping, alternate the clamps on both sides of the table, this will apply pressure more equal, and aid in preventing the issue you have. 

Personally I have found that bread boards, or end boards as I call them won't solve this issue. The Cherry long boards will move at a different rate as the end boards, and you will probably at some point down the road find gaps, IMO.

Like one said, DON'T CLAMP TO TIGHT. Are you using any biscuits in the boards? I have had good results in burying 1/4" strips of plywood approx. 1" deep in each board, then gluing. It's more work, but has worked well for me. 

I wish you well,

Dale in Indy


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## Steve Neul (Sep 2, 2011)

oakcutter said:


> I too am in the process of building a table top and am concerned about keeping it flat. My guess is there is a fine line between too much clamping force and not enough. So question is, how does one know what's enough. I have tried glued up panels before and wondered if I was forcing it to warp/bow because of too much pressure. Any thoughts?


Its pretty difficult to put too much pressure on a glue up. I've seen guys tighten their clamps and then take a crescent wrench to get a little extra umph on it. That is too much pressure. Normally a good snug is all it needs and try to put the same pressure on each side. The biggest problem in putting too much pressure is squeezing too much of the glue out of the joint which weakens the joint. The most important thing is to make sure the joints fit well before gluing so you don't need to use much pressure to begin with. If your forcing the a bad joint together then that much pressure is trying to pull them apart after your done.


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## woodnthings (Jan 24, 2009)

*+1 on cuttin' it apart and startin' over*

Cherry is some wild wood occasionally and will have a mind of it's own. I agree also that clamping pressure should just be adequate to get some squeeze out with an even uniform glue application. I usually go tight then another 1/2 turn on the pipe clamps, top and bottom about 8" to 12" apart. If you have to muscle it to close the joints, the boards aren't straight in the first place. Rejoint and dry fit again. Alternate cupping grain when possible. I generally clamp up on a flat surface if the size permits, then lift the whole thing off the bench and put the reverse side clamps underneath and snug them up to even the pressure. 

When thickness planing wood try to remove equally from both faces to avoid excessive movement. It's nice to have access to a wide belt sander when making a large glue up, door or table. Seek out a cabinet shop or mill and pay for the time on the machine, it's well worth it.


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## HowardAcheson (Nov 25, 2011)

How and where are you storing this glued up panel? Is it in a place and position where air can freely get to both surfaces? In other words, is the panel lying directly on another flat surface?


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## WillemJM (Aug 18, 2011)

Wood unfortunately moves and this can happen.

The way I design my tables is aprons closer to the edges, which would pull an inch flat without a problem.

It is also important to match the grain and growth rings prior to glue-up, which if done right will prevent cupping, as wood movement is not a constant, but can vary within the same species.


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## rayking49 (Nov 6, 2011)

HowardAcheson said:


> How and where are you storing this glued up panel? Is it in a place and position where air can freely get to both surfaces? In other words, is the panel lying directly on another flat surface?


+1 I try to keep the table top stickered on my assembly table till I can get it installed. That way air get to top and bottom alike.


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## TimPa (Jan 27, 2010)

+2. if it was laying on another flat surface, flip it over and wait. it may likely come back, but usually takes a little longer.


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## Midlandbob (Sep 5, 2011)

Panel warping is going to be from selecting the wrong boards. Some boards are prone to warping as they are cut from too small trees visible by small radius growth rings on the ends of boards. Also beware of uneven growth rings from "reaction wood" which is cut from trees growing in any other than very vertical. Any lean in the tree causes the tree to grow unevenly on one side vs the other. 
The most common abnormality is using wood that has not been well or evenly dried. If it has not been equilibrated to the environment it can/will distort/ warp after it has been glued up.
If the warping is too much to easily restrain, you will want to start over changing something significant. Reject any board that has irregular growth rings or has growth rings that are too tight.
As mentioned it is rare to impossible to over tighten the clamping.


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## BZawat (Sep 21, 2012)

Midlandbob said:


> Panel warping is going to be from selecting the wrong boards. Some boards are prone to warping as they are cut from too small trees visible by small radius growth rings on the ends of boards. Also beware of uneven growth rings from "reaction wood" which is cut from trees growing in any other than very vertical. Any lean in the tree causes the tree to grow unevenly on one side vs the other.
> The most common abnormality is using wood that has not been well or evenly dried. If it has not been equilibrated to the environment it can/will distort/ warp after it has been glued up.
> If the warping is too much to easily restrain, you will want to start over changing something significant. Reject any board that has irregular growth rings or has growth rings that are too tight.
> As mentioned it is rare to impossible to over tighten the clamping.


I respectfully disagree. Board selection is one possible cause of warp, but certainly not the only one. 
And it is definitely possible to cause a panel to be warped/cupped/twisted due to over tightening and/or improper clamp placement and balance. 

Perhaps the OP needs to determine exactly which of the factors mentioned in this thread contributed to his top warping before deciding how to proceed in fixing it.


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## firemedic (Dec 26, 2010)

Pictures... Need pictures.


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## HowardAcheson (Nov 25, 2011)

>>>> Perhaps the OP needs to determine exactly which of the factors mentioned in this thread contributed to his top warping before deciding how to proceed in fixing it.

Too true. There seems to be a propensity for offering solutions before there is a full understanding of the problem.


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## cgp4312 (Sep 20, 2012)

Thank you everyone for your response I finally gt around to working in the shop again and I had the tabletop sitting on the floor while I was gone and a lot of the warping left and when I put the breadboard needs on it is almost perfectly flat now thanks for all the responses they were a huge help


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## Midlandbob (Sep 5, 2011)

BZawat said:


> Board selection is one possible cause of warp, but certainly not the only one.
> And it is definitely possible to cause a panel to be warped/cupped/twisted due to over tightening and/or improper clamp placement and balance.
> 
> Perhaps the OP needs to determine exactly which of the factors mentioned in this thread contributed to his top warping before deciding how to proceed in fixing it.


Just what aspect of a glue line is going to cause cupping or warping??????
Unless you think you can clamp hard enough to crush fibres, the glue line is NOT the cause of warping. If you did "over clamp" you would get an angle in the top where the crushing occurred not a gentle curve as is the case with a warp.
An improperly jointed joint also would have an angle NOT a curved surface/plane.
Studies done and reported in FWW showed than conventional clamps do NOT have the force to over clamp. Maybe if you put a clamp every inch!
Wood deforms due to it's hygroscopic nature of taking on or losing water depending on the humidity and the fact that the dimensional change is different in the tangential vs the radial direction. 
Boards have built in properties/tendency of warping that vary from board to board. Board selection is critical.
A current FWW has an article on building flat doors which discusses the importance of wood selection to ensure flat panel glue ups.
Certainly Temporary warping can be caused by uneven changes in moisture like only finishing one side of a board or exposing one side to higher humidity than the other but warping is caused by undesired wood deformation due to changes in moisture content!!!


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## BZawat (Sep 21, 2012)

Ok


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## Tony B (Jul 30, 2008)

Are you clamping over and under - that is, gluing with one clamp under the boards and the other clamp on top of the boards and so on in a staggered pattern? This provides equal pressure across the boards and helps prevent warping and cupping.

One other thing I could think of is ..... is your table saw blade at exactly 90* to the table? Just a hair off could result in a cupping similar to barrel making where all the edges are angled. 

Just some thoughts. 


As for straightening the top out, I have never had any luck doing that. I go with some of the other guys on slicing the top up and re-gluing. Then flatten out the small ridges with a planer or a belt sander.


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## Midlandbob (Sep 5, 2011)

That's a good point.

Ideally a jointer fence(or saw blade) is perfectly squared. When jointing for a table top, it is valuable or important to mark the top by the sides of each board whether the face was in to the fence or out from the fence. Ensuring that each joint has an in and an out cancels any small error of the fence's vertical set that could add up to a none flat panel. It could give an angled glue line like a barrel as mentioned. It is not warped: it is coopered.. This can be used for an interesting curved door on a small cabinet. 
I do clamp top and bottom. If the clamping is a bit uneven it results in one side of a joint not being properly glued often with a crack . It is bad to find a small crack on one side of a glue line instead of a small squeeze out. I do use only hardwoods. Maybe a softwood might get crushed on on edge of a joint but it seems unlikely. 
The only solution is to rip, joint and re glue.


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