# Table top glue up cupping for this newbie



## Tom5151 (Nov 21, 2008)

Hello,

I just attempted my first table top glue up for a little hall/side table for my mom.

I am using select pine from one of the big box stores. The wood needed a little milling to make it flat, sqaure and of uniform thickness. There are three boards in the glue-up. Peices are 5 inches wide and about 33 inches in length X 3/4. I joined the edges and did not use biscuits. A simple butt joint. I was even careful to stagger the end grain so they weren't all going in the same direction.

All went well with glue up and clamping. After about 2.5 hours I unclamped and everything looked nice and stratight. However this morning I looked and overnight the whole unit cupped quite a bit. By the way, the unit cupped across the width of the table top. I have pics if you would care to see.

I am wondering what I might be doing wrong. I milled and glued up on the same day. Since I exposed new wood when doing that should I have allowed the wood to set a few days before glue up?

Any advice would be most welcome.

Again, I am a newbie, you won't offend me at all if you directly tell me how you think I might have screwed up and what i need to do to get it right. I really wanna get this right eventually.

Regards,
Tom


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## Rob (Oct 31, 2006)

I always set newly planed boards on edge, sitting on something narrow so the air, humidity and temps can get to the entire board. 
Just wondering if after you took it out of the clamps, it laid flat on a surface? If that's the case, the underside wasn't allowed to acclimate like the top face.
Just a thought.
Set it overnight with the other face down and see if it self-corrects.
Frustrating, ain't it?


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## mics_54 (Oct 28, 2008)

Post photos of the ends.
Did you wipe glue off with a wet rag during the glue up? Did the individual 1x6 cup? I normally rip to 2 3/4 inches and make sure the rips are 90 degrees. I usually check my saw often by ripping a wide board an standing it on edge on the saw top and check it with a square.


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## Tom5151 (Nov 21, 2008)

Hello,

Yes I did use a wet rag to wipe off excess glue right after clamping. I am thinking this actually caused one side to swell. Then when I took the assembly out of the clamps I laid it flat on a carpeted surface. As best I can tell all surface were 90 degrees. I checked and rechecked and made several test cuts.

From what I am gathering I should have laid it on edge to allow both surfaces to dry uniformly?

I got a tip from someone to lightly wet the concave side of the assembly causing it to swell and thusly straighenting out the cup. I am amazed but now in the last 30 minutes the assembly is almost perfectly flat. I have it drying on edge for about the past 45 minutes. I am wondering though if this will keep happening until I finish it and ultimately attach it to the aprons.

Tom


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## mics_54 (Oct 28, 2008)

yeah...on edge or at least stickered so it has air flow to all sides. It will probably stay flat unless it gets moisture on it again.


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## Rob (Oct 31, 2006)

I would put a quick coat of sanding sealer or spit coat of clear shellac on it. It will help to keep it stabilized.


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## Tom5151 (Nov 21, 2008)

got it guys....thanks for all your help......can I ask what the term "stickered" means?


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## Jason W (Dec 18, 2008)

Tom5151 said:


> got it guys....thanks for all your help......can I ask what the term "stickered" means?


Set up on strips of wood so air flows under.:thumbsup:


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## cabinetman (Jul 5, 2007)

Pine is relatively soft. When you clamped up you may have applied too much pressure along one edge, that didn't show immediately when removed from the clamps. Alternating the sides for the clamp positions will help, using cauls, and applying just enough pressure to make a good glue bond will prevent overclamping problems.


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## Tom5151 (Nov 21, 2008)

Hi Cabinetman,

Thank you for your reply.

I actually used 3 clamps on the bottom side and two on the top. I also used cauls. But I am wondering now if maybe i used too much clamping pressure. I cranked them down pretty tight. This was the very first time i have ever done a glue up ever.....lol......I have a lot to learn.

I know it's hard to describe this without actually being there, but is there anyway you can describe the appropriate amount of pressure I should apply when clamping with pine? Is there such a thing as a "clamping rule of thumb?"

Regards,
Tom


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## mics_54 (Oct 28, 2008)

When clamping a "glued up" panel of this type I lay out the pieces on a flat surface as they would be glued up and inspect the assemblage for uneven spaces indicating bowed members. If any members appear bowed I would attempt to mitigate or eliminate the 
the problem entirely by re-sawing as needed. I push the pieces together gently so as not to force them but to reveal any joints that aren't square. Once I am satisfied with the joints I apply glue to both surfaces of each joint and clamp them loosely untill all clamps are in place. In a glue up of the size you mentioned I would use 4-5 clamps...one on each end laying on the table rather than on top of the assembly....and at least two equidistant from the ends (aprox) I tighten the clamps until I get glue being squeezed out of the entire length of the joint and until no more will come out. I try to estimate the approximate force to be the same on all the clamps. Maybe..snug plus half a turn?


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## GeorgeC (Jul 30, 2008)

mics_54 said:


> When clamping a "glued up" panel of this type I lay out the pieces on a flat surface as they would be glued up and inspect the assemblage for uneven spaces indicating bowed members. If any members appear bowed I would attempt to mitigate or eliminate the
> the problem entirely by re-sawing as needed. I push the pieces together gently so as not to force them but to reveal any joints that aren't square. Once I am satisfied with the joints I apply glue to both surfaces of each joint and clamp them loosely untill all clamps are in place. In a glue up of the size you mentioned I would use 4-5 clamps...one on each end laying on the table rather than on top of the assembly....and at least two equidistant from the ends (aprox) I tighten the clamps until I get glue being squeezed out of the entire length of the joint and until no more will come out. I try to estimate the approximate force to be the same on all the clamps. Maybe..snug plus half a turn?


Sounds like a pretty good description to me.

I also have a tendency to over tighten and have to watch myself. If you tighten so much that you squeeze out all of the glue there is nothing left to hold the assembly together.

G


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## red (Sep 30, 2008)

We live and learn. Post some pics when you have the project complete. Red


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## Rob (Oct 31, 2006)

I give a light coat of glue to both edges. Light enough that the wood grain can be seen under the glue.
I tighten enough that uniform "droplets" of glue form at the glue line. If the glue drips on the underside, I've applied too much glue.
After I'm satisfied with the glue-up, I'll give each clamp just the slightest "oomph" for good measure.
If the boards are already at the desired thickness and the joint line is perfect, I'll let the droplets dry and scrape off after taking the clamps off. If the boards will need more work to even things up after glue-up, I'll wipe the wet glue off with a damp sponge.


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## Tom5151 (Nov 21, 2008)

Thank you all for the great tips.....

I think eventually I am going to get this......I have sooooooo much to learn.

Best regards and Happy Holidays to all,
Tom


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## AZ Termite (Dec 20, 2008)

In the beginning it is a lot of trial and error. Make notes on what works and what doesn't. The more you do the eassier it gets, and the better the projects turn out. Keep at it, as Red said, we live and learn. I tend to get a little carried away with clamp pressure as well.


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## djonesax (Mar 3, 2008)

I read this a day late... I had some 12x12 squares of walnut that werent perfectly flat so i ripped them into 6 inch widths, jointed, glued and planed. They were perfect..... until I woke up the next morning and discoved that they had cupped. I had mine laying flat after planing. I decided to just go with it because I didnt have enough thickness to plane again and it would cost me $16 for more wood. I have already finished the wood and they are being used as bases for speaker stands. I figured I would make up for the cupping with adjustable feet. is there anything I can do at this point being that they are aleady finished?


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