Warped tabletop - to plane or not to plane?

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Forum topic by Anthon posted 12-10-2015 04:31 PM 2260 views 0 times favorited 8 replies Add to Favorites Watch
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1 post in 921 days

12-10-2015 04:31 PM

I have bought a 2m x 1m x 4cm (78 inch x 39 inch x 1.5 inch) oak tabletop .
Unfortunately, I got warped.
Not much, but still unacceptable for a design I’m making – it needs to be perfectly flat.

So my question is – should I try to straighten it by soaking in water and putting weights on it or is it better to start planing?
Not sure how it will react to water – I’m afraid it will make everything worse.

Here is a picture of the tabletop I’m talking about.

The warp is described by fig 3

8 replies so far

View pintodeluxe's profile


5702 posts in 2836 days

#1 posted 12-10-2015 04:33 PM

Anchor it down to the table frame through slotted holes. This will cinch the table flat to the frame, while still allowing for seasonal wood movement.

Good luck.

-- Willie, Washington "If You Choose Not To Decide, You Still Have Made a Choice" - Rush

View BinghamtonEd's profile


2298 posts in 2392 days

#2 posted 12-10-2015 05:58 PM

Question … how did it end up warped? Did it come that way? Did you leave it laying on the floor? Or, did it just seem to happen?

If its just a hair off, and can be pulled flat, it should be fine, but if it doesn’t want to flatten out, don’t force it too much.

If it came that way when you bought it, can you get a replacement? If you can’ I’d do that, and get it attached ASAP to discourage it from happening again, or at minimum, get it properly stickered.

If you laid it flat on the floor, or some other surface, with only one side exposed to air, this can happen. Its happened to me. You may be able to fix it by laying it with the opposite side on the floor for a couple days, with some weight on the high spots.

If it just naturally happened, and can’t be replaced, and has time to fully acclimate, I’d go at it with hand planes. A top that size shouldn’t take too awful long (I recently finished a table top, 70” x 22, wasn’t too bad, and was probably in worse shape to

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

View jmartel's profile


7951 posts in 2173 days

#3 posted 12-10-2015 06:05 PM

For that I’d consider ripping it down the middle. That would remove the warp. Then glue it back up and it should be much flatter. I think those tops are stapled/nailed together for each strip, but a good carbide tipped blade should cut through those without much of a problem.

-- The quality of one's woodworking is directly related to the amount of flannel worn.

View Tennessee's profile


2873 posts in 2537 days

#4 posted 12-10-2015 06:25 PM

Hard to believe that it left the factory warped, so you have to assume that it was a little too green and relieved itself.

I have had no faith in the water method over the years. The main reason is that although it might come back with water, weight and time, it almost always goes back to the original warp when you dry it all out, stickered or not.

I also am iffy about cutting it down the middle. It will create two edges that are not completely 90’ when cut, and when you glue it back up it will try to reestablish the edge, and possibly just set up warped in the clamps.

How many MM is it warped? You are 1 meter wide and only 40MM thick. I’d think if you are less than 10-12% of the thickness warped, (4-7MM), you could pull that down into the table frame and be done.

If it is more than that, I’d think in terms of what Ed suggested, get out the hand planes.

-- Tsunami Guitars and Custom Woodworking, Cleveland, TN

View mahdee's profile


3888 posts in 1790 days

#5 posted 12-10-2015 08:20 PM

You can get two white oak boards slightly smaller than the apron width and length, screw them to the underside of the top (make the holes slightly bigger than the screw diameter on the boards for movement) at intervals to flatten it. (you can also use shims if needed to aid the flattening but I doubt you need them. Insert the top and screw the boards to the inside of the aprons.


View rwe2156's profile


2958 posts in 1503 days

#6 posted 12-11-2015 01:30 PM

I’ve never had any luck with differential water/heating on wood this thick. Mechanical fasteners OK for minor cupping but overpowering a significant warp with mechanical fasteners is not the best way IMO.

The “cut apart/glue back together” method is the best way to handle cupped panels in my experience.

Rip along glue lines. Use a bandsaw to minimize waste. If you don’t have one, use a thin kerf blade.
Test and see what you have (you don’t say how much warp) it may be necessary to rip the other two pieces as well. Before making cut, mark pieces to put back together the same.

Note: Do not glue together right away. Sticker and allow to dry for at least a week for something this thick. Its possible you could be relieving stresses incurred during glue up.

Rejoint & reface and glue up. Be sure to do test clamp up and test for flatness with straight edge and winding sticks before gluing. Final tweaking can be done with hand planes. You’re panel will probably be a few mm’s thinner due to resurfacing.

Good luck.

-- Everything is a prototype thats why its one of a kind!!

View martyoc's profile


42 posts in 940 days

#7 posted 12-11-2015 02:46 PM

Is there any type of finish on either side? If there is I’d suggest sanding it off and then placing the tabletop vertically on one side edge for a few days to see if that helps. Place a small fan to keep the air moving will help. Measure the cup before you do. Do this in an interior room, not in a garage or damp basement where the temperature and humidity can change dramatically. If it helps, great. if not there are some good suggestions already given by others.

-- Marty O'C

View AZWoody's profile


1346 posts in 1247 days

#8 posted 12-11-2015 04:36 PM

I’m not sure what I would do but the only reservation I would have about planing the top is that if it, for whatever reason decides to settle back down to it’s original shape, then you’ll have a depression where you planed it.

First thing I would do is try to just fasten it down.

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