Any tips to un-warp a butcher's block bench top?

[strantor]

The table top on the floor is the same type as the bench to the left. The one on the floor I took apart a few years ago and left the table top leaning long-ways against the wall. Apparently over time it drooped under its own weight. Now I want to reassemble and use it again, preferably in its former flat form.

As you can see I've stacked some random heavy-ish stuff on it to try and flatten it out but my intuition tells it might take years for that to work. I'm going to check it again in 24 hours and see if there has been any progress but I don't expect any. That's why I'm asking.

I have a feeling that some heat would quicken the process, maybe I could set up a heat gun to blow underneath it. But I worry that might compromise the glue that binds it, and then it could split.

 

[lordbeezer]

Put some real weight on it. Heavy.

 

[strantor]

I have 16 pieces of unistrut between 4 and 5 feet, I think I'm going to clamp it between unistrut once every foot and leave it out in the weather. Plywood always seems to take the shape of its surroundings when I do that, so I assume this will do the same.

 

[homebrewed]

Heating the bottom side would cause it to expand and reverse the curve, but that probably would only be a temporary fix. The heat might also dry out the wood more on the bottom, causing it to shrink & making the problem worse.

Maybe the top absorbed more water and expanded? If so, running dry, warm air across the top would flatten it....once it all cools back down to equilibrium.

Just guesses here. I suggest browsing some woodworking sites to get some ideas on what to do.

 

[7milesup]

Is the butcher block finished, i.e., Does it have a coat of varnish, etc. on it?

The likelihood that it warped from its own weight is slim. Most likely, the side facing the wall absorbed more moisture and the side facing out dried out a little more, causing the warping.

You are correct about letting it take a while for natural drying to occur. The general rule of thumb is 1" of thickness per year of drying.

If it were me, I would do one of two things (or both, actually).
1.) Place it in the sun just as you have it sitting. Keep an eye on it because that may be more effective than one may think, especially considering where you live. The sun will give it a very nice, even heat and will work much better than any attempt to heat it with a heater.
2.) Use some angle iron to bolt it onto your bench to straighten it out. Use a lot of clamps, though, and take your time; otherwise, you will pull fasteners out. If you are through bolting it down, then that wouldn't apply.

I will bet placing it in the sun will fix your issue.

(35 years of woodworking exp.)

 

[extropic]

It took "a few years" to get it warped like that. IMO, it will take "a few years" to flatten it (unless you have access to a large enough steam cabinet) without cracking it. The alternative, that I have used, is to take it to (assumed you don't have one) a wide belt sander and have it worked on both sides. If there are metal screw thread inserts installed, REMOVE them first, regardless of your estimate of how much material the sanding will remove. YMMV

 

[strantor]

Is the butcher block finished, i.e., Does it have a coat of varnish, etc. on it?

Yes, lacquer or something, I'm not sure.

If it were me, I would do one of two things (or both, actually).
1.) Place it in the sun just as you have it sitting. Keep an eye on it because that may be more effective than one may think, especially considering where you live. The sun will give it a very nice, even heat and will work much better than any attempt to heat it with a heater.
2.) Use some angle iron to bolt it onto your bench to straighten it out. Use a lot of clamps, though, and take your time; otherwise, you will pull fasteners out. If you are through bolting it down, then that wouldn't apply.

I will bet placing it in the sun will fix your issue.

(35 years of woodworking exp.)

Ok thanks. I did these two things (basically)



It turns out I was right to be hesitant about applying too much weight to flatten it. I ended up splitting it while clamping it between unistrut using just wrist strength to tighten it with a t-handle wrench.



I can't tell you how many times I've heard that wood glue is stronger than wood, but this what I've come to expect from glued joints.

 

[matthewsx]

Cut it down into sizes that are useful around the house.

 

[7milesup]

I can't tell you how many times I've heard that wood glue is stronger than wood, but this what I've come to expect from glued joints.

If you look carefully, the wood broke, not the glue. If the glue failed, it would be a perfectly straight break, but it is not.

 

[markba633csi]

You could make a series of parallel saw cuts lengthwise underneath and fill with epoxy then clamp
That's the only quick way I know of