Glue up warped, options to fix

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Forum topic by lumberjoe posted 09-25-2012 02:08 AM 13196 views 0 times favorited 43 replies Add to Favorites Watch
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2899 posts in 2276 days

09-25-2012 02:08 AM

Topic tags/keywords: ash warp

I’ve been working on a table for a while, It’s my first venture into arts and crafts and I am taking my time with it. The table top is made from curly ash and is 21×24 – 3 pieces laminated. That was the first thing I did about 3 weeks ago. I only sanded it to 80 grit so far – no final sanding and no finish. It has significantly warped despite being laid flat. One high spot is right at a glue line. The glue up was actually nice on this one, you can only see the glue line if you look for it at the end grain, and the middle board developed quite a bow.

I don’t have a drum sander or 21” jointer. I could flatten it with a router plane, but the warp is significant enough (the middle is about 5/8” off the table) that I would need to remove too much material. Here is what I am thinking, but I would love to hear your options:

1 – Rip along the glue lines, ditch the middle board and re-glue (I have a piece that will ft and match)
2 – Instead of three 7” strips, rip them down into smaller pieces. The overall dimensions will be 20” x 22” so I still have some room for a blade kerf here and there.
3 – Lay it down on the cast iron table saw with some even and significant weight on the top of it when the TS is not in use

I doubt #3 will work and it will likely compromise the glue joint


43 replies so far

View Grandpa's profile


3259 posts in 2704 days

#1 posted 09-25-2012 02:18 AM

I was taught woodworking many years ago when Industrial Arts was taught in the high schools. I even have an Industrial Arts degree. I still am not sure what to do but I will tell you what I was taught. Rip the glue lines then rip each of those 7” boards and flip every other board. Let the wood hold itself straight by alternating the grain. The glue lines will likely show worse. This usually happens unless you veneer a substrate. When you glue the boards, use cauls to hold it straight. Leave it clamped for a couple of days and see what happens. I have done these things and still ended up glues another board on the back side to hold if. Big pieces want to move on you. Good luck. Maybe someone will have a miracle cure for you but this is what I was taught and what I would do.

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1021 posts in 2314 days

#2 posted 09-25-2012 02:36 AM

I personally would try option 1 and hope for the best. I think the less glue lines you have, the less opportunity for problems you will have. I’ve got plans for a similar table with a 5/4 curly maple top, so I may be in the same boat soon.

-- John, BC, Canada

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8209 posts in 2605 days

#3 posted 09-25-2012 03:47 AM

Maybe glue them up like the picture?

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Joseph Jossem

492 posts in 2297 days

#4 posted 09-25-2012 03:52 AM

go with #1 I have dealt with that before even with grain match up pictured above

View a1Jim's profile


117127 posts in 3605 days

#5 posted 09-25-2012 04:01 AM

Laying wood flat exposes one side to more drying than having it on stickers, possibly causing warping. It could be your wood is not dry enough or you did not let it acclimate long enough in your shop before making your panel or one board just had internal stress causing it to warp. This is a good example of why you rough cut material in advance and let it sit in your shop as long as possible before building. All said and done the easiest way to go is option #1

-- wood crafting & woodworking classes

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#6 posted 09-25-2012 04:07 AM

Rip the glue lines, mill the boards square, and alternate the rings.

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2374 posts in 2861 days

#7 posted 09-25-2012 08:39 AM

Just what all the guys above already said. You might want to invest in a wood moisture meter, too.

-- Thomas - Pondering the inclusion of woodworking into physics and chemistry classes...

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8057 posts in 3404 days

#8 posted 09-25-2012 11:38 AM

I’d try option #1 first. Jim raises a good point about moisture differences.

-- Happiness is like wetting your pants...everyone can see it, but only you can feel the warmth....

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2899 posts in 2276 days

#9 posted 09-25-2012 11:51 AM

Thanks for all the replies. I’m going to rip the glue lines and re-glue it square. I still have 36 mortises and tenons to cut, so I am going to wait until I am closer to final assembly (which thanks to the cold weather already could be a few weeks) I did alternate the grain on these, but Jim pointed out my mistakes that I didn’t even know I made:

1 – These were glued up about 3 hours after I sent them through the planer at the mill. They were dry to begin with, the guy at the mill measures MC for me (these were 6%, and it is KD lumber)

2 – I don’t know why I didn’t think about the laying flat thing. That makes total sense now. I’ll use stickers from now on.

Now the question is, what is the ballpark amount of time I should let the wood acclimate to my shop before working with it? I don’t have a lot of room to store wood long term, so I buy it on a per-project basis. This little end table is going to end up being about 23bf. I generally lay out and rough cut right when I get the wood home so I don’t have to trip over 10’long boards


View BinghamtonEd's profile


2298 posts in 2398 days

#10 posted 09-25-2012 02:28 PM

I had a similar experience. I glued up a 20”x96” panel out of maple. Left it on the concrete floor for a few days and came out and it had cupped. Luckily I was able to put some cauls on it, flip it over on the floor, and over the course of a week or so occasionally tighten the cauls down and get it to almost level back out, and cleaned it up with some hand tools. I will never make the mistake of leaving them directly on the floor again. And neither will you!

I use the process that Tommy Mac kept stressing on Rough Cut, just because that’s the only instruction I’ve ever received : I cut about 10% larger than final dimension (within reason, obviously the amount you overcut depends on the size of the piece, you wouldn’t want to waste too much), sticker the parts for a couple days, and then when I’m closer to assembly time, I bring them down to final dimension. I think if I were going to need longer parts that could cup and bow more, however, I wouldn’t cut them and leave them sitting around too awful long.

Good luck, Joe!

-- - The mightiest oak in the forest is just a little nut that held its ground.

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2899 posts in 2276 days

#11 posted 09-25-2012 04:16 PM

I never let any wood touch the concrete floor for any appreciable length of time after I learned that important lesson. That’s a good tip on waiting a few days. I generally cut everything right when I get the lumber, and I do cut oversize, generally an inch or two. I like to pre-finish my work as I go along, so I start with the top and the large pieces like the aprons. by the time the legs and other details are done, the finish is just about dry.

Looks like I need to be a little more patient and let the wood acclimate first.


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2899 posts in 2276 days

#12 posted 09-25-2012 04:18 PM

One other thing, I’m a little concerned sending this through the table saw due to how warped it is. Is that an unrealistic concern? The edges are still flat and they both make contact with a flat surface evenly.


View BinghamtonEd's profile


2298 posts in 2398 days

#13 posted 09-25-2012 04:32 PM

You would probably be OK, but if the edges are on the top and the part you’re cutting is not, you might run the risk of the workpieces pinching the blade as the two sides separate. Given the size of the piece, you could just clamp a straightedge to it and use a circular saw if you’re concerned, and then clean up the edges on the TS afterwards.

-- - The mightiest oak in the forest is just a little nut that held its ground.

View a1Jim's profile


117127 posts in 3605 days

#14 posted 09-25-2012 08:23 PM

When your concerned about sawing warped wood I would use a band saw to rip . If I were going to use a hand tool and a guide I think I would use a router with a bearing, Doing it this way your router is riding on the guide(another board) not the wood.It may take several passes lowering the bit each pass.

-- wood crafting & woodworking classes

View joeyinsouthaustin's profile


1294 posts in 2101 days

#15 posted 09-25-2012 09:05 PM

All good leads, especially grain orientation, cauls, air circulation, etc. Here is some more input

Clamping: Was it clamped over and under to equalize the cupping action of the clamps??

It appears you mention only the center board cupped. May be it has a mind of it’s own, or can’t get along with others… discard it if you can. (No I don’t talk to the boards…that often. keep reading.) Moisture is not the only thing to consider. Natural oils can remain through the kd process. I always plane both sides when doing table or counter tops and rest my boards,(24 hours, based on species)every board separated by cauls, after planing. When you open all those cells they can create the a fore mentioned mindfullness. (I have watch properly dried tropical woods relax and tighten right before my eyes while jointing) When milling 10/4 mahoganies for door style and rails I’ll join, rest, join, rest, plane, rest, and even rest after shaping. The door I just completed rested for 3 months before final glue up. In my experience curly grains have concentrated amounts of the oils and such, and even pressure from lignins. (and like shirley temple can have trouble getting along with others) Some of the turners might know more about this.

-- Who is John Galt?

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