how to fix cupped table top

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Forum topic by redwing98 posted 12-18-2010 04:00 PM 5928 views 0 times favorited 4 replies Add to Favorites Watch
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6 posts in 4040 days

12-18-2010 04:00 PM

Topic tags/keywords: question trick

I glued up an oak top 20”x20”x 3/4”. I forgot to stain the underside and now it’s cupped on me with about 1/4” from base on 2 sides. I can pull it flat with clamps and I’ve since stained the backside. My concern is the stress it’ll put on the glue joints. The planks are 3-4” wide and have biscuits in them.

Can I clamp and screw or is there a way to make it right?

-- Woodworker wannabe in training

4 replies so far

View Mark Shymanski's profile

Mark Shymanski

5623 posts in 4323 days

#1 posted 12-18-2010 05:01 PM

Do you have sufficient thickness on the top to just plane it flat again and not fight with straightening it? Once its cupped it means the moisture is already in there, I guess if you could dry it out before staining it it may return to flatish, and then you could plane it true again.

-- "Checking for square? What madness is this! The cabinet is square because I will it to be so!" Jeremy Greiner LJ Topic#20953 2011 Feb 2

View Lee Barker's profile

Lee Barker

2172 posts in 3461 days

#2 posted 12-18-2010 05:56 PM

First of all, don’t blame yourself for not staining the bottom. I can’t imagine that would have made a significant difference.

If you dry it out and plane it flat, I suspect the whole scenario will repeat itself.

If you are confident the boards have reached equilibrium, now is the time to cut the joints apart and flatten the boards and reglue.

Are you alternating growth ring patterns in your boards?

To prevent this in the future, the big fix is a moisture meter. The low tech fix is to be sure the boards are in your possession long enough to become stable.

The key thing here is that you don’t want to be flattening that top with some kind of structure which forces it to be flat. You don’t want to build that kind of stress into your project. So kudos to you for stopping at this point and regrouping, which may include recutting and replaning and regluing!

-- " his brain, which is as dry as the remainder biscuit after a voyage, he hath strange places cramm'd with observation, the which he vents in mangled forms." --Shakespeare, "As You Like It"

View jmichaeldesign's profile


66 posts in 3393 days

#3 posted 12-18-2010 06:35 PM

If the table is a personal project I’d just screw battens to the bottom to flatten in out. If it stays it stays, if not you cut it apart and re glue it up.

If it’s for someone else, especially if you’re selling it then I would probably just go ahead and make a new top. Its not even 4bf of material so I’d personally start over instead of fixing the current one.

View redwing98's profile


6 posts in 4040 days

#4 posted 12-18-2010 09:33 PM

Thanks for all the advice. This was a table that had a nice oak base that I salvaged but the top was wasted. My mom will be using it for a night stand and being 80yrs old, I’m sure she’ll have some sort of cloth covering like she does on all her other tables.

I’m gonna clamp and screw it with battens. If it splits, I’ll cut it and re-glue. The only reason I haven’t done that yet is I didn’t give myself a lot of room to spare in my overall dimension so I can’t make too many more cuts. Never notice just how much those 1/8” saw cuts and those light passes on the jointer add up until you don’t have it to spare.

-- Woodworker wannabe in training

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