It's Moving!

[jackellis]

I bought a pile of 6/4 Ash several weeks ago that was supposedly kiln dried. I'm using some of it to make frames for pull-out drawers in the kitchen, which requires resawing it to 7/8", then milling.

It seems like time after time, I cut or mill pieces of this stuff and then watch it move on me. Yesterday I resawed a 34" long piece that's 9" wide, hoping I could use the waste side for something. While the good piece remained fairly flat, the waste side curled in two dimensions. A straight rule laid across shows about a 3/8" ap (not matched on the good piece) and about 3/16" measured along the length.

I'm suspecting the lumber moves somuch because it hasn't fully dried yet. we're seeing some weather change here, but average temps have only dropped about 10 degrees. After all, this IS California.

Any thoughts?

[bmyers]

That wood will still be moving long after you have stopped moving

Wood, unlike most other building materials will ALWAYS move. Changes in temperature and humidity will cause movement. Tension in a piece of lumber changes when you cut the lumber also so a straight chunk of 6/4 3 feet long has forces pulling it directions that equal out but once you cut it those forces change again and things are not so straight.

Even if the wood is sealed up in poly it's still going to expand and contract in your completed project over time. You always have to take in to consideration that the wood is going to move and make provisions for it to do so, don't bother try to stop it from moving. Best you can do is minimizing the impact of the movement.

It's good to take into account what time of year you are building something when making provisions for movement and clearance. A 1/8" gap on a drawer front in December can end up being a 1/64" gap in August or vice/versa depending on your climate.

The wood may have been kiln dried correctly and still have major movement because of how it was sawn. 1/4 sawn wood tends to have less movement due to how the growth rings line up with the board. Plain sawn lumber tends to have a little more movement in it but you get more lumber from a tree when it's plain sawn so it's cheaper and you see more of it.

Is your lumber plain or 1/4 sawn?

Hope this helps.


Bill

[jackellis]

Bill,

Thanks for the reply. I knew I'd have to deal with movement but I wasn't prepared for so much movement. Short of buying an expensive moisture meter, I'm trying to rule out poorly dried lumber as a cause. The amount of movement has been a big surprise.

As far as I can tell, it's plain sawn lumber. Same thing with two groups of fresly cut black walnut lumber I just purchased. At least I know the walnut isn't ready.

I could have cut the 9 inch board in half lengthwise before I resawed it, and I may do that next time. I'm not sure my 14" bandsaw has the power to resaw a 9 inch high piece, though I still need to fix a few things on it.

[Ken Massingale]

Jack,
Since the thinner piece 'curled', I suspect stresses in the wood.
Even tho the wood is kiln dried there is a difference in moisture content from the outside to the interior. When I started resawing in earnest I too was surprised at how the stock would change from nice flat stock to have some distortion. Some research showed that resawn stock needs to be sticked and have some weight on it for a few days to let it acclimate again, since what was inside is now outside.
Always something, isn't it?
Good luck
ken