Wood "warping" definitions - Woodworking Talk - Woodworkers Forum
 
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post #1 of 6 Old 06-19-2009, 10:42 PM Thread Starter
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Wood "warping" definitions

People say "My wood is warped, what should I do to fix it?"
Warning: Do not attempt to saw a warped board on the table saw!
How should I joint a "warped board?" Of all places to have this discussion this is the place. So, here are some definitions:
Wood warping

From Wikipedia, the free encyclopedia



Wood warping is a deviation from flatness as a result of stresses and shrinkage from the uneven drying of lumber.
The types of wood warping include:
  • bow : a warp along the length of the face
  • crook: a warp along the length of the edge
  • kink: a localized crook, often due to a knot
  • cup: a warp across the width of the face, in which the edges are higher or lower than the center
  • twist: a distortion in which the two ends do not lie on the same plane
Wood warping costs the wood industry in the U.S. millions of dollars per year. Straight wood boards that leave a cutting facility sometimes arrive at the store yard warped. This little understood process is finally being looked at in a serious way. Although wood warping has been studied for years, the warping control model for manufacturing composite wood hasn't been updated for about 40 years.

The answer to your question will only be as detailed and specific as the question is detailed and specific. Good questions also include a sketch or a photo that illustrates your issue. (:< D)

Last edited by woodnthings; 06-19-2009 at 10:50 PM.
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post #2 of 6 Old 06-22-2009, 03:22 PM
 
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This has to raise some discussion. I guess the next thing is how do you "unwarp" wood?
Based on what I've read so far, it's not worth the time to try to unwarp it.
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post #3 of 6 Old 06-22-2009, 03:27 PM
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Quote:
Originally Posted by nelcatjar View Post
This has to raise some discussion. I guess the next thing is how do you "unwarp" wood?
Based on what I've read so far, it's not worth the time to try to unwarp it.
plane it
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post #4 of 6 Old 06-23-2009, 09:50 AM
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I don't know if you can unwarp wood successfully, but I have had some success uncupping wood by clamping it using pipe clamps so that the cups are back to back. It seems that you should be able to unwarp wood to a degree using a similar technique.
I have also uncrooked wood by stacking and stickering it with the back of the crook up in the center, and then loading a large amount of weight on it.
The big question of course will be if it stays straight when used in an application.

Gerry
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post #5 of 6 Old 06-23-2009, 03:45 PM Thread Starter
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Quote from the wikipedia

"Wood warping is a deviation from flatness as a result of stresses and shrinkage from the uneven drying of lumber."
It seems to me that the drying process is not and cannot be equal in different types of wood and in different ways in the same species and piece, due to the pressence of stress, grain, knots, the place on the log from which the board was sawn, IE. quartersawn, flat sawn etc. So it's my opinion that you can't really "unwarp" wood. Quatersawn is the least likely to warp in the drying process. When you can acclimate it and let it reach the humidity level of it's intended environment, then mill it flat, and remove the twist and cup etc. then assemble it as soon as practical and apply the finish to seal it from additional changes in humidity. If you do anything other than that you will end up fighting with the warp, as it will return eventually. As the cells in the wood lose their moisture in the drying process the wood shrinks and takes a set. This is why roughsawn boards are 1/4" greater in thickness before milling than the finished wood. It may take a 1/4" of total stock removal to get the dimension lumber flat and straight. JMHO bill

The answer to your question will only be as detailed and specific as the question is detailed and specific. Good questions also include a sketch or a photo that illustrates your issue. (:< D)

Last edited by woodnthings; 06-23-2009 at 07:38 PM.
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post #6 of 6 Old 06-23-2009, 06:37 PM
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It's hit or miss. Just when you think you're good to go, Mother Nature rears her ugly head. Simple tasks like ripping straight lumber can produce what I call "walking". As the wood gets cut, it just gets all squirrley and twisty. If you haven't experienced that yet, you're in for a surprise.

It helps to buy KD (kiln dried) stock, but in the end the wood will acclimate itself. Hopefully we get lucky more often than not.






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