Table Flatness Question

[JohnM Martin]

I'm working on a dining table (~ 40" x 70") and I'm confused about why it won't stay flat. I've built it using 8/4 walnut that was dried (properly stacked and stored) in a garage for 7 years. I did everything I thought to do during the build - alternate growth ring direction, used breadboard ends, careful edge glue up, glue up in stages, and gave it plenty of time to acclimate in between gluing sessions. Before and after installing the breadboard ends, I flattened it with planes. Now, about a week after installing breadboard ends (and the last flattening), it seems to be cupping. It's not a lot, maybe 1/8" in the worst place, but I'm confused on what I should do next. I don't want to do finish prep and finish and have it move on me again. I'm pretty new to this, is this normal? What should I do next? Any thoughts/suggestions?

For Reference:

389471

[Simon MacGowen]

Looks fine to me, despite the measurement you reported.

Putting a finish (the same no of coats on top and bottom) will help reduce wood movement, but will not prevent it, if your piece is subject to humidity changes. You have done what you can do (yours is the textbook approach), and if I were to you, I would finish it and enjoy it. That is how solid wood should and will behave with some degree of unpredictability.

Simon

[Kees Heiden]

The under structure will help to keep it flat too. Make sure the wood can move in the width!

[Brian Holcombe]

A table top is kept flat not only by the breadboard ends but also by the battening supports that attach it to the legs. Without them even well seasoned material may cup.

[Andrew Hughes]

Are you keeping it lifted up off your bench to get air circulation.
Too much temp change where it sits.
Bread bored ends not done right
These are all mistakes I’ve made in the end as others mentioned no one cares about a slight cupping but me.
Looks like some nice walnut I see a purplish color

[Steve Jenkins]

Any unfinished panel will warp if layed flat an not covered due to moisture changes on the top surface. Either set it on edge or lay a piece of plastic or scrap plywood on top.

[glenn bradley]

I believe Andrew and Steve have hit on your issue. If the assembly is still unfinished it is very susceptible to moisture absorption and release. If it is not stickered any exposed surface will react much more than the unexposed surface resulting is some wonky movement.

I try to leave the top to last in the build sequence so that it is in an unfinished state as little as possible. if your base is not ready to finish I would just go ahead and put the finish on all sides of your top; at least the first couple of coats. You can apply additional coats while you are applying finish to the base when it is ready.

[JohnM Martin]

Thanks, all, for the suggestions. I guess it makes sense now that I think about it that it is only getting moisture to one side. I guess I'll sticker it or lay it on edge until I'm ready to flatten it one more time... just before finish prep and finish.

[John Kananis]

Try flipping it over for a day or so - may correct all on its own that way, then stand and/or finish it. Best of luck.

[Robert Engel]

Try flipping it over for a day or so - may correct all on its own that way, then stand and/or finish it. Best of luck.

THIS ^^^!!!

You'll be OK, I promise!!

[Simon MacGowen]

(properly stacked and stored) in a garage for 7 years.

Was surprised to hear that you did not follow the same stacking procedure after you planed and glued up the table top and let it sit in your shop.

After you reflatten your top (by planing or reapplying moisture), remember to put the same finish treatment on both sides of the top...else you may be surprised to see a cupping again after you move the table into your house!

Simon

[Kees Heiden]

I always sticker the parts of my projects in between work sessions, and I always add a cover as the top layer. Lately I have used pieces of laminate flooring. If I feel very thourough I'll even put a weight on top.

Without the cover the top panel in the stack will still see unequal humidity levels to either side.

[Marc Jeske]

Probably, As talked about above, the convex side has gained moisture compared to the convex side, or vice versa.

Do whatever you need to to either remove moisture from the convex, or add moisture to the concave - CONSIDERING what direction you want the general MC to go.

Lets say that it rained 3 days straight while this top was sitting flat on a bench.

I would then expect the exposed to ambient topside would go convex.

One could try, very attentively, to bring out and set on sawhorses exposed to Sun.

Check w straightedge maybe even every 15 minutes.. change can happen rapidly w this extreme method.

Be VERY attentive, I would bring it in to stabilize after a half hour max I would say.

Next morning, re check .. straightedge feeler gauging.. document movement.. proceed from there.

Or just run a fan over convex side if a "Dry" ambient day.

These are just MY experiences, more experienced feel free to comment on my post.

From then on store it w equal air circulation , temp, humidity, etc to both sides equally.

Marc

[Simon MacGowen]

I always sticker the parts of my projects in between work .

+1

I try to finish a project within the same week or two henever possible, and never saddling two seasons.

Simon

[JohnM Martin]

+1

I try to finish a project within the same week or two henever possible, and never saddling two seasons.

Simon

This is good advice, and it makes sense. Unfortunately, never enough time in the shop. Having said that, I've re-flattened the top and stacked it with stickers and a top cover layer with hopes of starting finish prep tomorrow and finish application this weekend. We will see how it goes.

[Marc Jeske]

How did you "re flatten" ?

Marc

[JohnM Martin]

How did you "re flatten" ?

Marc

I put it up on stickers for a day, then took it off, and took the planes to it. After I got it flat again, I put it back up on stickers and added a cover to the top as others have suggested. We will see if it works :)

[lowell holmes]

I had a top flattened at a cabinet shop near my house one time. See if there is someone close that can help you.

[Marc Jeske]

I just hope that the additional removal of material will not rear it's ugly head to bite you once the tabletop reaches equilibrium.

May or may not happen, all depends on "Where the wood was "at"" when you did previous flattening, and exposure after that.

Only time will tell.

I would be curious to hear down the road.

A common woodworking challenge for wide panel projects.

Marc

[Matt Lau]

Worst case scenario- claim it was intentional...to add a whimsical twist to tired, old fashioned, mass produced commercialism.