Hello – I’m sure this is an overly asked question, but I’m new so please forgive me. I am building wood panel kitchen doors out of maple boards that I jointed and glued up. Clamped them square and as level as could be. Scrapped and sanded them flat – and then they warped/cupped.
I did the alternating growth rings when possible, but I still get the cupping. What do you experts recommend to avoid/reduce the warping and cupping? Thanks.
Rich
Replies
Are you talking cabinet doors or people doors? If they are on cabinets, are they base cabinets, upper cabinets, or both? Dimensions? Thickness? Finish? What size boards did you start with? Are the doors subject to significantly more water vapor on one side than the other? How badly are they cupped, i.e. if you put a straightedge across the concave side, what's the greatest distance between the door and the straightedge?
The simplest way to prevent cupping is to use only quarter sawn boards, but even that may not work if moisture and air circulation are very different on the two surfaces. Battens or breadboards ends are two other approaches. If you don't have your heart set on solid wood slabs, frame and panel doors of some flavor are likely to be a lot more stable.
To ad to what was already posted, did you leave them laying on a table for any period of time? Panels that have unbalanced air flow will tend to cause warping. Just remeber to sticker everything until it has a finish coat on it
Rich - The panels warped because the moisture content in the wood changed. The wood was not in equilibrium with the humidity in your shop at the time you glued the panels up - either too wet or too dry - and the panels warped as they gained or lost moisture. If they were sitting on a bench top at the time, the warping was exaggerated by the one-sided moisture transfer.
This happens all the time. There are various things you can do about it: allow the wood to equilibrate for at least a week in your shop before working it, use frame-and-panel joinery to help hold the panels flat, and most important, apply finish as soon as possible. A useful trick is to leave the panels slightly thicker than the final dimension until you are ready for final assembly; do the last planing just before assembly, then apply finish ASAP, making sure to finish both sides equally.
Finally, be aware that this is something that will continue to occur even after finishing (it just happens more slowly) as humidity changes. This is why stock selection and joinery are important.
"Everything should be made as simple as possible, but no simpler." A. Einstein
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