Warped board . Can anyone help please?
randomwoodguy
| Posted in General Discussion on
I brought some kiln dried oak and planned it down to 1/2 inch thick then made square shaped plate stands for them . I then applied danish oil over them and then they cupped/bowed up out of shape .
any ideas why this has happened when the were from kiln dried wood ? Is it because I applied the danish oil straight after sanding and planning?
any advice would be greatly appreciated thanks in advance.
Replies
In my experience the single most common cause of wood warping is improper milling and preparation. Properly Kiln dried wood is usually 7-10% but wood constantly takes on and gives off moisture depending on the environment around it. My process is to buy my wood well in advance of actually using it, usually 3-4 weeks or more for thick stock and storing it in my shop properly stacked and stickered to insure air circulation. This let's the wood acclimate to the humidity condition in my shop. When I do start to mill it I do it in 2 stages. The first includes the face jointing and rough planing, being careful to take the same amount of wood off of both faces leaving it about an 1/8"oversized. It is then stacked and sticker again for 2-3 days to let it rebalance its moisture content after having exposed the wetter inner core of the wood. Then I check it again for cupping and if need be I face joint it again before planing to final thickness alternating passes on each face. If you don't alternate faces when planing you increase the chance of wood warping because you will expose more moisture laden wood on one side and it will create an imbalance as the wood re-equalizes.
I have no mental image of what your plate stands look like but if they are simply flat pieces of wood they will always be more subject to warping than a piece of wood assembled into a cabinet or drawer box etc. Because there is no support or structure to help resist the forces involved. This means additional care needs to be taken in preparation.
The other thing is to make sure you finish all sides to insure that moisture can't be absorbed or released from one side more readily than the other.
Brilliant information thank you very much!
What "esch" said!
I have a question/concern about the lumber. Is it flat, rift, or quarter sawn? It is my personal experience (lesson learned) that flat sawn lumber from other than the "best" part of the tree will be prone to cupping when milled thin.
Planing unequally off both sides can do it b/c it creates a moisture imbalance.
Good idea to hold it in cauls and let reacclimate.
There's never any guarantees. White oak can be one of the "trouble makers".
Agree with the previous replies. The other thing to be aware of is that being kiln dried can be functionally a temporary characteristic. If I take some kiln dried lumber and put it in an open shed for a year here in humid Tennessee, it will end up essentially like air dried lumber again, with a moisture content of around 14%. The first time we ran into this, we bought our first moisture meter with the money we made on the project. Most of the hardwood lumber dealers I've visited don't have climate controlled warehouses. So how long has it been since the lumber was kiln dried? A good moisture meter is your friend.
Kiln dried lumber gets case hardened. This affects the outside faces, but not the interior. If you plane most of the material off one face and little or none off the other, you are apt to get cupping. If you resaw a thick board in half, the same thing happens.
As noted above, make sure to remove equal amounts from both sides of the board.
Thanks everyone for your replies Iv learnt a lot Iv managed to undo the the cupping with a moist towel and an iron this time but now I know where I went wrong I think I planned to much off one side . Thanks again
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