How Can I Fix This Warped Top?

[Derek Arita]

Just got this box that measures about 12 x 12 x 16 and looks to be pine. It's probably about 20 years old and has a clear finish on it. I'd like to put hinges on the lid, but as you can see, the lid has warped, despite the use of some cross members to prevent it. Is there any way I can safely flatten out the lid?
http://imageshack.us/a/img854/2128/mv6w.jpg
http://img23.imageshack.us/img23/7325/gj43.jpg (http://imageshack.us/photo/my-images/23/gj43.jpg/)

[David Wong]

It is interesting that the top has warped despite the use of what looks like quarter sawn boards. Perhaps the cross members are at fault. I would first loosen or remove the cross members, and give the top panel a few days to readjust. Seems like you could fix this by replacing the cross members and perhaps adding a 3rd one.

[Jerry Miner]

I'm with David. I would pull the cross members off. How straight are they on their own? Make replacements, or cut a crown into the existing to pull the top into flat. Maybe even use a stiffer species for cross members.

[keith micinski]

I'm with jerry, I would taper the cross supports to a crown except I would probably make new ones instead of using those because it's obvious they want to be warped. If I was going to reuse the existing ones I would flip them over giving you a crown and going against the existing warp in them.

[Dave Zellers]

I'm with Keith. Make new ones, use a few more screws, NO glue.

After removing the old ones clamp the new one to test to see if you need to crown it. I doubt you will.

Although, thinking about it, if you are going to hinge the back, a tiny crown would insure the front sits down tight.

[Ken Fitzgerald]

Try placing a known good straight edge against the cross supports to check them for flatness though visually they appear to be warped.

Then remove them and give the top a few days to rest. Then check it for flatness.

Then try clamping a couple flat pieces of wood in place of the support cross members and see what the top wants to do. In doing so, listen to the wood and look for signs of cracking as you draw it straight.

If necessary, as recommended by others possibly put a small crown in the cross members to flatten the top.

[Lee Schierer]

Place the side with the cleats toward a heat register for a couple of days. It should flatten out.

[Jamie Buxton]

The top is likely curved because the builder made a mistake. He screwed the cleats to the top. He'd probably have had less curving if he hadn't put the cleats on at all. What's happening here is that the top is trying to shrink across the grain. If there were no cleat, the quartersawn top could have gone about the contraction. It would have gotten a little narrower, but stayed flat. When the cleat is added, the only way the top can contract is to curve the top.

The first thing to try, as the others have said, is to remove the cleats and see if the curve goes away. I predict it won't; it has been held curved for a long time. If it stays curved, make new cleats. These should be a little curved, so when you screw them to the top, the curve of the cleats counteracts the curve of the top. You may need to tweak the cleat curves a few times to get it right. These new cleats should be attached firmly to the top in the middle, but the ends should be a sliding connection. Usually that's an oval hole through the cleat, and screws through them that aren't quite tight.

[Ronald Blue]

I agree with Jamie. The cleats are the cause of the warpage. Remove them and see what happens. I had a similar experience on a lid. I thought I was making it stronger by adding the cleats. After a couple weeks it was warped. I removed them and it straightened back out on its own. The topside shrunk and the cleats didn't allow the bottomside to do the same. Lee's suggestion of placing the former cleat side towards a register might bring it back flat. Let us know how it works out.

[Howard Acheson]

The cross members are the cause of the warping. The top wants to expand and contract with changes in the moisture content of the wood. The cross members are trying to prevent this movement. You have classic cross grain situation.

You can try removing the cross grain members and see if the top becomes flat. It probable won't if its been warped for a year or more. If you end up rebuilding the top--which might be the best solution--be sure to affix the cross pieced in a manner that allows the top to freely expand and contract. Make the screw holes in the cross members as slots and don't tighten them down too tight.

[eugene thomas]

Maybe just nothing but looks like glue stain next to one of the cleats?

[Ole Anderson]

Maybe just nothing but looks like glue stain next to one of the cleats? I agree, which of course complicates the fix by a whole lot if the cleats are glued to the top. Also confirms the error of not allowing for cross grain wood movement during construction as many have already said.

[Peter Aeschliman]

These new cleats should be attached firmly to the top in the middle, but the ends should be a sliding connection. Usually that's an oval hole through the cleat, and screws through them that aren't quite tight.

Exactly. It cupped because the bottom (underside) of the top wasn't allowed to move. So the top surface shrunk more than the bottom surface. Derek, you didn't mention whether the cross-braces were screwed on with slotted holes, or if the cross braces were glued. But based on the way the top cupped, I'm willing to bet it was either glued, or the screw holes in the cross brace are not slotted. Also, make sure to use pan head screws (not countersunk) to allow the top and the cross brace pieces to "slide" past one another. Counter-sunk screws could fight that motion, which is bad.

It looks to me like the top is made of pine- if so, you might just want to build a new top. Pine isn't very expensive. Depends on how attached you are to the painted detail on the top.

You might also consider exposing the "top of the top" to moisture if it doesn't flatten out on its own after the cleats are removed. I.e., put it in the shop with a damp towel on top for a day or two. This could ruin the finish though...

[Kent A Bathurst]

Battens caused it, as everyone has noted. NO slotted holes, and maybe glue.

If it was mine, I would remove the battens, sand it back to bare wood, soak it real good with water, put it by a heat source as Lee said. Potentially even put cauls on both faces and clamp it tight.

It should straighten out. Then - refinish. I'm not so sure I would use battens on something that small, to be honest.

[Derek Arita]

Well, thanks for all the help. I tried the remove the battens, only to find that they are glued...bummer. I guess I'm glued and screwed! This taught me a good lesson however, so all is not lost. Just wish the maker of the box had known what you guys know.

[Dave Zellers]

The battens would have been just fine on that top if they had not been glued. It was the glue and only the glue that caused the warping.

NEVER GLUE BATTENS!

The slotted holes at the ends is a reasonable step but often unnecessary especially with pine and something that small.

[Dave Zellers]

You could still cut or chisel them off, plane them to the glue line, scrape off the glue and put new battens on, slightly wider to cover the edges of the old ones.

[Jamie Buxton]

Well, thanks for all the help. I tried the remove the battens, only to find that they are glued...bummer. I guess I'm glued and screwed! This taught me a good lesson however, so all is not lost. Just wish the maker of the box had known what you guys know.

Here's what I'd do to remove the glued-on battens... Remove the screws. Stand the top on edge against the rip fence on the table saw. Set the fence so the rip cut removes about one kerf-width of wood. Do the other batten too before you move the fence. Move the rip fence one kerf with toward the blade and remove more material. Repeat until the battens are mostly removed. (I'm doing this nibbling approach because I suspect the top may try to straighten out somewhat as the batten is removed. Trying to cut the entire batten off in one pass may result in trapping the blade.) Then put the top down on the bench (bench dogs would be convenient to hold it), and remove the remaining batten bits with a handplane. Complete the task with a cabinet scraper or sander.

[Ronald Blue]

You have nothing to lose by using some creative techniques to remove the cleats. Possibly the router table? I would experiment with trying to salvage the lid.

[Derek Arita]

OK...so I took off the battens, then clamped some boards to the top, with spacers in the middle, forcing the warp in the opposite direction. I did this on both ends of the top. The top sat like that for 3 months with no change. All of a sudden, I checked the other day and viola...the warp is gone and is headed in the opposite direction. I think now I will take off the clamps and bows and see how it settles. I plan on not replacing the battens. Just thought I'd let you know how it turned out.

[Chris Padilla]

Pictures, Derek, pictures!!! :) Very cool! We have some smart folks here!

[Derek Arita]

Sorry...I'll try to post a pick of the setup. The sanded areas are where the battens were. Not very fancy, but it was effective...
http://i63.photobucket.com/albums/h151/derekarita1/IMG_0733_zps10441300.jpg (http://s63.photobucket.com/user/derekarita1/media/IMG_0733_zps10441300.jpg.html)

[Derek Arita]

By the way, I ended up using my Bosch multitool with a flush cut blade to cut the battens flush, then sanded off the residual glue and wood residue. That multitool was the perfect solution here.

[Jeff Duncan]

You have a LOT more patience than I do! Something that small and simple I would have just made up a new top and been done with it;)

JeffD

[Derek Arita]

I would have done that too, however the top is old and has ducks painted on it. The box does as well and is at least 30 years old.

[Chris Padilla]

Nicely done, Derek! I, too, would have done it your way to preserve everything as much as possible.