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Thread: wood movement

  1. #1
    Join Date
    Sep 2007
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    Boca Raton FLorida
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    101

    wood movement

    I'm in the middle of my first project and I just finished the doors. I used solid mahogany which I trimmed with a solid maple 2 inch band. Am I going to have a problem with wood movement splitting apart my doors?

  2. #2
    Join Date
    Jan 2007
    Location
    Sacramento, CA
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    1,325
    Hi Gene,

    The answer fully depends on the direction the grain goes on your panel. If you have grain glued at T-intersections on wide panels, you may have issues. The idea is that you always allow for cross-grain to expand and contract. The species of a wood can be a guide for how MUCH movement, but the mixing of the two really doesn't do much to preclude or exacerbate the rule of allowing for it, I don't think.

    If you have a long grain to long grain glue, don't worry there. Wood doesn't do much swelling in the longitudinal dimension. Your biggest point of expansion will be parallel to the growth rings - that is to say quartersawn boards move less in width than flatsawn boards. They still move, just not as much.

    Edit: I should toss in some numbers to help. The general rule that I follow is to allow for up to 1/8" of movement for every 6" of width. It's possibly a little overkill in some species, but I sleep better with that rule
    Jason Beam
    Sacramento, CA

  3. #3
    Join Date
    Sep 2007
    Location
    Boca Raton FLorida
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    101
    I definately have T-intersections and my doors inside panels are 12x32. The banding adds 4 inches both ways and ends up being 16x36. I guess time will tell for sure. If I have to I can always remake the doors if they split.

  4. #4
    Join Date
    Nov 2006
    Location
    Austin, Texas
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    1,349
    Unless the maple is as thin as a veneer (so that it will be forced to follow the movement of the underlying wood) the simple answer is yes, you will have a problem.

    Here are a few rules of thumb... and as rules of thumbs, there will be exceptions and some disagreement. But for starters, assume ...
    1. Wood expands and contracts across the grain... anything more than a couple inches has to be accommodated.
    2. The expansion and contraction the length of the grain is negligible
    3. A veneer is wood that is thin enough (generally less than 1/16 inch thick) so that, when it is glued to a substrate, it will move with the substrate. It is too thin to force it's own movement across the grain
    4. Plywood has grain running both ways, in veneers, so is stable. You can assume plywood has no wood movement. Same for MDF and particle board.

    The reason raised panel doors have been around hundreds of years is that the rails and stiles are only a couple inches wide, so you can ignore the movement where the rail joins the stile. The panel in the center is larger than a couple inches, so you have to plan on expansion and contraction. The center panel "floats" in a groove in the rails and stiles, sometimes with rubber "space balls" or other tricks to keep the panel centered without rattling.

    There was a very dramatic example on another forum... Someone made a (presumably) very durable oak table. With lots of glue and screws in the wood braces across the bottom to hold the tabletop together. So many screws and glue that it tore the table apart in the first season of expansion and contraction. Multiple splits running the length of the table.
    Charlie Plesums, Austin Texas
    (Retired early to become a custom furnituremaker)
    Lots of my free advice at www.solowoodworker.com

  5. #5
    Join Date
    Sep 2007
    Location
    Boca Raton FLorida
    Posts
    101
    Thanks for the bad news and help. The next doors will be made like my kitchen with the rail and stile or a veneer on the inside over something that doesn't move like plywood or particle board. Thanks again for the help. It will be interesting to see how long before it splits. I hope I finish before that happens.

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