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Thread: cupped drawer face

  1. #1

    cupped drawer face

    I recently installed a 3/4", 12Hx18W solid maple drawer face on some drawers that I made from Baltic birch and after painting the cabinets moved them down in to my basement from my shop outside. The drawer face is made up of two pieces edge glued together then trimmed to size. Unfortunately, it didn't occur to me at the time that I might run in to some cupping issues due to the height of the panel. What I'm left with after a few weeks acclimating in my basement is a drawer face that is cupped 1/8" or so out at the bottom and the top from the face frame. Is there anything I can do to fix this mistake? Is wetting the concave side, or taking the face off to let the backside dry more likely to bring this panel back to flat? I could try pulling the panel flat with a screw in each corner of the face through the birch ply drawer box but there isn't much meat to grab on to in a 3/4" thick face.

  2. #2
    If the face is a piece of wood applied to a different piece of wood, then I would remove the "show face". Use a router
    to to make some grooves in the back that stop short of showing at the ends. That will make the face piece flexible
    enough to glue and screw the backer piece.

  3. #3
    Quote Originally Posted by Mel Fulks View Post
    If the face is a piece of wood applied to a different piece of wood, then I would remove the "show face". Use a router
    to to make some grooves in the back that stop short of showing at the ends. That will make the face piece flexible
    enough to glue and screw the backer piece.
    That's a good idea. I'll try routing a single 1/4" groove on the backside and go from there. Any idea what depth I should start at to be able to get the 3/4" face to become flexible? Maybe 1/2"?

  4. #4
    One solution to cupping is to rip the panel in half, rejoint and reglue. Bandsaw will minimize wood loss to about 1/16"

    I try to always apply a drawer face with the bark side out. Tendency to cup will be countered by hand drawer front screws and hardware pulls.

  5. #5
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    You mentioned painted...did you paint the back side of the drawer front? That could certainly contribute to cupping as much as a moisture imbalance after milling can do so. Hopefully, the groove will work for you. You can also install additional fasteners between the drawer box and the face as long as the holes in the plywood drawer box are enlarged a little to allow for seasonal wood movement across the grain of the solid stock drawer fronts.
    --

    The most expensive tool is the one you buy "cheaply" and often...

  6. #6
    I did paint the back side, but not as many coats as the front which I know will affect the evaporation rate.

  7. #7
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    I would take the drawer front off, stand it on edge so air can circulate around both sides, and just wait a couple of weeks for the MC to equilibrate. It may end up flat again of its own accord. If the MC was constant when you made it it should end up flat again when it's constant again, even at a different mc.

  8. #8
    Quote Originally Posted by David Prochniak View Post
    I recently installed a 3/4", 12Hx18W solid maple drawer face on some drawers that I made from Baltic birch and after painting the cabinets moved them down in to my basement from my shop outside. The drawer face is made up of two pieces edge glued together then trimmed to size. Unfortunately, it didn't occur to me at the time that I might run in to some cupping issues due to the height of the panel. What I'm left with after a few weeks acclimating in my basement is a drawer face that is cupped 1/8" or so out at the bottom and the top from the face frame. Is there anything I can do to fix this mistake? Is wetting the concave side, or taking the face off to let the backside dry more likely to bring this panel back to flat? I could try pulling the panel flat with a screw in each corner of the face through the birch ply drawer box but there isn't much meat to grab on to in a 3/4" thick face.
    A cup warp is normally caused by a imbalance in moisture content from one side to the other. Assuming you finished the front and not the back there is likely a crown on the back side. If that is the case if you can take the front off lay it in the sun and keep an eye on it. The sun should remove the moisture from the back side until it flattens. As soon as it does take it in and put a finish on the back side before putting it back on the box. Another option would be to go ahead and make another drawer front and go ahead and finish it on both sides and then change out the fronts.

  9. #9
    Chances are, if you have a cup problem now with that piece of wood in the drawer face, you probably will always have some problems with cupping, regardless of what you do. It is just something that happens with wide boards (including glued up boards) of unstable wood like hard maple. Getting the moisture content/distribution back to what it was when you milled it will make it flat, but there is no way to make that permanent, regardless of how you dry or finish the wood. You might be able to get away with more screws holding it in place (hard to do with 3/4), but then you will need to account for expansion/contraction across the 12"

    Which brings us to another potential problem in waiting, you may also have issues with expansion and shrinkage with the drawer face. 12 inches is pretty wide for solid wood drawer front of maple. Not sure of your location, but around here (MN), flat sawn maple can change in size something like 3/8 or more per foot across the grain between winter and summer.

    Depending on your design, you could maybe use two pieces with a tongue and groove or shiplap between them. That would halve your cupping and expansion/contraction issues.
    Last edited by Andrew Seemann; 10-09-2019 at 11:52 PM.

  10. #10
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    That amount of seasonal expansion/contraction only applies to unconditioned houses. Most folks now have some sort of AC in the summer, and that likely cuts the value in half. That said, I completely agree that a 12" wide solid wood drawer front will likely be problematic unless the RH remains within a pretty tight range year round.

    John

  11. #11
    The drawer front in question will spend it's life in a WI basement that is either humidified or dehumidified to a pretty constant level year round. Do you think that I'll still likely see a problem?

  12. #12
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    Wood moves in response to a change in RH. If the RH doesn't change much it won't move much. Hoadley's book "Understanding Wood" shows how to calculate how much.

    John

  13. #13
    Quote Originally Posted by David Prochniak View Post
    The drawer front in question will spend it's life in a WI basement that is either humidified or dehumidified to a pretty constant level year round. Do you think that I'll still likely see a problem?
    It's hard to say and depends a lot on your individual situation. I'm near Mpls, and indoor relative humidity here can be in the high 80s in the summer (with AC!), down to below 20 in the winter. We don't humidify our house much in the winter, because our windows can't handle any more condensation than they already get.

    Needless to say we probably experience more expansion/contraction and wood movement issues in MN than most areas of the country.

  14. #14
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    It sounds like yours is cupping concave towards the front? That's what I would expect if the back side is tight against a drawer box (no air circulation) and the front is exposed to drier air. Some stopped kerfing of the back and letting it dry face down so that it starts to cup towards the back side will probably do the trick.
    JR

  15. #15
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    Quote Originally Posted by Andrew Seemann View Post
    It's hard to say and depends a lot on your individual situation. I'm near Mpls, and indoor relative humidity here can be in the high 80s in the summer (with AC!), down to below 20 in the winter. We don't humidify our house much in the winter, because our windows can't handle any more condensation than they already get.

    Needless to say we probably experience more expansion/contraction and wood movement issues in MN than most areas of the country.

    Your AC unit must not be sized appropriately or not functioning properly. One of the primary benefits of AC is that it dehumidiies the air. Mine drops the RH into the 40% range in summer, same as the house runs much of the time in the Winter. It's only in the buffer seasons when the AC and heat are off that the indoor RH swings higher.

    John

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