Resawing and Warpage

[Chris Jenkins]

Just trying to get a general consensus out there as what is a better method when resawing and gluing up.

I am aware that resawing causes many boards to release internal stresses and so your two new pieces tend to warp. What is the better method?

Resaw and glue up right away and try to force the boards to stay free of shifting by using clamps

OR

Resaw and wait a few days hoping that the boards with proper air flow may straighten back out THEN glue up?

Is their another method that's better that I don't know about?

Thanks,
Chris

[Marc Casebolt]

Chris,
I have never seen a re-sawn board right itself by letting it dry out more. Assuming that the lumber is properly dry, the internal stress will do what it wants to when cut, and you have to make sure you cut it thick enough to re flatten it once it's had time to take its final shape.
This depends entirely on the board you have, and the extent of warpage will vary between each board you cut.
With dry lumber the warp is apparent right off the saw, and doesn't seem to get much worse with time, so you can adjust the thickness of your cut accordingly as you go. If the lumber is not dry enough, give yourself a little extra thickness and hope it doestn't go crazy on you.
I've heard of people clamping the re-sawn board flat to prevent warp, but have never tried it.
Hope this helps, Marc

[Terry Beadle]

I've tried clamping a resawn board with only moderate success. The forces involved are directly from Mother Nature and she's no push over.

If it gets bad, then you have to cut with the grain, joint and reglue...bummer but it works.

[Alan Turner]

My method is to cut heavy, let it do its thing, and then deal with it as new, non-flat lumber. Clamping, weights, etc, are not solutions, in my experience. Even from the same lot of boards there are variations.

[al ladd]

I've had best luck by stickering resawn material with weight on top, or even clamping presssure. So airflow, (a fan trained on the stck helps --coat ends with glue if you expect to lose more than 1 or 2 %) but also applied force coercing in the direction of flat. Let sit for 36-48 hours, then rejoint flat and thickness plane off that face. It's a good idea to measure moisture as you're resawing to check for gradients --then wait for everything to even out before glueing or final flattening and thicknessing.

[jim gossage]

if the wood has already acclimated to the ambient humidity of your shop, then stickering and fans probably will not do much - in this case the wood moves due to grain related stresses. if you are resawing a thin veneer, then movement won't matter much as it will easily conform to the veneer substrate. if you are resawing thicker pieces, say 1/4-3/4 inch thick, try to resaw in a straight-grained area (which should minimize movement); if you can't find a straight-grained area, then resaw thick and joint/plane to final thickness after it stabilizes.