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    User riverstwo's Avatar
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    Wood movement after dimensioning?

    How much wood movement is normal after prepping stock?

    It seems like I'm either not properly dimensioning my stock and then forgetting about it, or its moving around a bunch after I prep it. I've noticed this before to a lesser extent but tonight I went to edge-joint a panel and one of the boards has a pretty significant twist in it. I flattened one side of it yesterday, and squared an edge to the flat side....I know I threw the winding sticks on it because it to doublecheck when I was finished because the board was a little twisted when I started. I'm doing this work by hand, and the stock is 4/4 air-dried White Oak that has been drying for 20+ years. The lumber is reasonably straight/flat from the mill and pretty straight-grained as well.

    Any pointers/wisdom is greatly appreciated,
    Thanks,
    Randy

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    Re: Wood movement after dimensioning?

    Some woodworkers believe that twist always comes back. I won't go that far but I avoid twisted lumber whenever possible because even if you rip into narrower pieces, it still wants to twist unless you glue it into a QS panel.

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    Re: Wood movement after dimensioning?

    There is always a difference between the moisture level in the center of a board and the outside, no matter how long it has dried. Let it sit and see if it goes back close to square. It could also be stress wood...like from a limb or leaning part of the trunk.

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    Re: Wood movement after dimensioning?

    Randy, I'm in the school of twisted stock pretty much wants to twist back, but I've fiddled around with what I guess is called reaction wood from trees that grew on steep hills and also branch stock.


    Since you know how to use winding sticks, then I'm pretty safe to assume you have some idea about what you're doing and that the stock was well acclimated to your shop. I usually rough out and then sticker the stock to see if it's well behaved. Then I'll plane and for a panel, I always intend to glue up immediately. If it's for a captured panel like a raised panel door, I'll also try to get the glued panel into the frame ASAP.


    If you just plane off the high corners and don't touch the entire board, or if you flatten only one side, I guess there is some potential for uneven moisture. Most thickness planing reference will tell you to pull from both sides evenly. Some of that could be an allowance for the moisture content inside the board but I've also read references to the case hardening issues where taking wood from only one side could be a problem.


    As an aside, about 15 years ago I built a 42" round breakfast table that has at least a 15/16" thick top. The finishing books said I only needed to finish one side of the table, so that's what I did. Twice a year it would rapidly turn into a seriously crazy looking pringle potato chip. I coated the bottom and the amplitude of the distortion dropped a good 90% and the slowing of the moisture exchange smoothed out the whole thing. The wood still moves but nowhere near as severely as it did.

    BTW, that top tends to remain flat. The crazy bending (thankfully) was entirely due to the uneven moisture exchange from the uncoated bottom.

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    User riverstwo's Avatar
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    Re: Wood movement after dimensioning?

    Thanks for the responses. TENdriver, I had definitely taken more stock off of one side than the other. I'm going to let it sit an extra day or so and re-flatten it, fortunately I hadn't taken it all the way down to its finished thickness and have some extra stock to play with. It's hard to get stock milled/glued up in one session in the shop since I get much of my work in on evenings after the kids are in bed...I need to be more disciplined about that I guess.

    Thanks again all!

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    Re: Wood movement after dimensioning?

    The biggest part of twist is due to stress, not moisture. That being said, as a board dries a twist will increase because as the board dries and acclimates, the stresses are released.

    The reality is all you can do it re-flatten/re-mill and hope you will still have enough wood for a usable board. Of course, this depends on the amount of twist, which you haven't told us about ;-)

    With wood that seasoned chances are better you can get if flat and stabilized.

    Equal milling is is important, not so much for moisture equality, but trying keep the stresses equalized.

    What TEN is describing is not twist but cupping which is totally different & moisture-related.

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    Re: Wood movement after dimensioning?

    Dr. Bob, Yes! Somehow I started out with stress in reaction wood and wandered over to uneven exchange without fully explaining.

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    Re: Wood movement after dimensioning?

    Plant and wood movement is hydraulic. Most "stress" is moisture related. There are special cases like limb wood, leaning or twisted trees, the majority of the time it's moisture.

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