router thicknessing jig and wood movement.

[mleichtle]

I glued up a panel for a coffee table, 4 boards 1-1/4" thick to make a panel 20" x 40". The wood I used, soft maple, is from a local mill. Its been in my shop almost a year, so its been well over a year drying since it was first cut. So I built a router thicknessing jig to flatten it. The panel had a little cup to start out so I put the crown up in the thicknessing jig and took off just a smidge down the center, basically flattening the center 12 inches. then let it go for a day since I had to go to work. The next day I find the panel had reversed its cup, about 1/4". I flipped it over and planed the other side barely taking 1/8", samething, off to work. This time the corners curled up about 5/8". Dicouraged, I let it sit for a few days. I looked at it this morning and its laying pretty flat. Is this normal? Anyone else have this dilema?

[JR]

I've never had that happen. It sounds like the wood is still a bit damp.

But now that it's decided to be flat, I'd install it! Git while the gittin's good!

JR

[Carlos]

Weather.com says your city has had some rainy and some dry days lately. Maybe you just have some humidity-induced movement going on. I've had that happen when I cut on a rainy day and tried to glue up on a dry day.

[Uncle Cracker]

Sometimes, after cutting or planing wood, even if it's dry, you get what is called reaction movement. This is where built-up stresses internal to the wood are allowed to release when the wood is "vented". Some woods are more prone than others, and how the wood is stored (and what condition it was in when storage began) and grain characteristics of the piece are contributing factors. Sounds like you took off enough to let your board boogie down.

[Carlos]

I had a lot of that recently with Wenge, but didn't think Maple was so prone to it?

[Uncle Cracker]

I think hard maple not so much, but soft maple can.