Fixing a cupped board on tabletop

[Scotty Gadlin]

If this is a rough table anyway, you could place several battens across the bottom of it with lag bolts pulling the boards flat. I'd probably use something about two by three inches, the stiffer the better. Short of that, you'll have to disassemble the table and either rip, joint, and plane the top boards flat and glue them into one large panel or redesign another top. Construction lumber is going to move unpredictably unless you dry it out properly which would take months.

Dan

Thanks, I will give this a try

[Robert Engel]

I think where you went wrong was using too wide boards + not supporting all the way to the edge.

I'm with Kent here, once a thick board cups like that, there's not much hope short of ripping it down, squaring the edges and regluing back together.

And it may still warp even after that.

Using construction lumber for furniture projects is a perilous undertaking because the moisture is so high unless you take care to let the stock acclimatize.
You need to sticker it and let is dry out at least a month or two or check the moisture content with a meter.

BTW, I've had plenty of boards cup even though they were finished both sides.
Don't know how to explain it, but it happens.

[Greg Cuetara]

Not that this is an ideal solution but why wouldn't his idea #4 work. I have seen others make kerf cuts on the bottom side of tempermental wood to 'flaten' it out. The cuts could go about half way through and then filled with epoxy.

Why wouldn't this work? So many people just say to rip down, joint, plane and then glue back together and that is the only way. This is not a Thomas Moser piece costing tens of thousands of dollars. I would think maybe a combination of a few kerf cuts on the underside filled with epoxy and then some straps on the underside to help it stay flat over time. It might even be worth it to try and get 3/16" or 1/4" steel plate about 2" wide, then paint it to match and screw in from underneath. The only reason I suggest steel is to minimize what is sticking down from under the table.

Greg

[Scotty Gadlin]

So I decided to make a bunch of kerf cuts with a circular saw, to the distal half of the board. It was moderately successful, about 60% improvement. Makes a huge difference though.

[Charles Lent]

Another method for dealing with "construction lumber" when you want to make furniture with it is to make it into quarter sawn. Rip the pieces into 1 1/2" squares or squares of whatever the thickness of the wood is, then rotate the squares until the grain is vertical and glue it back together. With the grain lines running across the thickness of the board (in this case vertical) it will be much less likely to cup, although it will still shrink. I've never done this with long boards, but it should work. My experience has been making pine end tables and coffee tables.

Charley