Wood Tension - Bending

[John Czaplicki]

Another newbee question.......

I recently purchased some QSWO. When I cut one of the 4/4 boards into long thin pieces, 1 x 3/4 x 36, I get an unacceptable amout of movement.

I've read about "wood tension", but the grain of this wood is relatively straight. I suspect this has to do with the drying process or moisture content. It did just come out of a kiln 2 weeks ago, I removed it myself, and as been sitting in my shop since. Unfortunately I do not have a moisture meter....yet.

Will allowing more time to dry or reach equilibruim in my shop get rid of this issue, or is it just a bad board or tree? Any other suggestion on how to stop the wood from reacting this way, or how to deal with it, would be appreciated.

[John Czaplicki]

If moisture or uneven drying is my issue, will the strips I previously cut staighten at all with a little time, or is it unpredictable?

[Mark Bolton]

What type of kiln was it dried in? Relieving the stresses in the wood (equalizing) while kiln drying is essential to eliminate case hardening which is the usual cause of a board "going wild" when you cut it. The kerf can either open, close, one leg can raise, lower, or in some cases any combination of the above and differently all through the cut.

The tension in the wood at the time of sawing can have an effect as can how it was sawn however generally if it comes out of the kiln ok those factors usually werent very great. Generally speaking, if the wood is going to move due to growing or sawing conditions it will not come out of the kiln straight even if heavily weighted.

Mark

[Chris Padilla]

How bad is the wood moving after cutting your thin veneers? How thick are the veneers? Any pics?

How about clamping the veneers to flatten them or putting lots of weight on them?

I've been resawing lots of walnut lately (3/32" resaws drum sanded down to 1/16") and it has all behaved very well but I'm uncertain how the walnut was dried.

I'm told that kiln-dried wood is not that great for bending because of how the fibers react during the "fast-drying" stress a kiln puts on wood. There are some threads here discussing bending and kiln dry versus air dried wood so do some searching.

[John Czaplicki]

Type of kiln....not sure. I didn't know there were different types. The guy who owned the saw mill built it himself. It was an insulated shed, for lack of a better description, equiped with heaters, moisture monitors, fans, etc. I believe he said it could hold 4000 bf.

What you describe as the syptoms of case hardening is exactly what I experienced.

[Chris Padilla]

Case hardening is wood that is dried inappropriately which, I think, means: too fast. Different trees react differently to the speed at which their moisture content is dropped. Some can take fast removal better than others. Perhaps this guy dried his oak too quickly?

[John Czaplicki]

Mark, thanks for the 'case hardening' key word. I've been searching online for a while with no luck, but case hardening did the trick.

http://sres-associated.anu.edu.au/fpt/drying/kiln.case.html

I guess I have to interogate my lumber supplier's drying techniques more carefully! Why is it so hard to get a nice piece of fairly priced wood? All part of the quest I suppose.

Thanks for your help everyone.

[Larry Edgerton]

Why is it so hard to get a nice piece of fairly priced wood?
.

Its not. You just are not buying at the right place.

You need to include your location so Creekers close to you can make suggestions. I use LL Johnson Lumber but if you are in Timbucktu Sas-catch-a wand my suggestion is useless.

[Brad Shipton]

How much do you consider unacceptable? If your supplier is following generally accepted drying practices I bet your wood is just as good as what we all use. Part of the quest is learning how to work with the imperfect realities of wood. The narrower the stock width, the more potential there is for it to deform.

When a tree grows in the forest it leans, it bends, it is subjected to variable moisture, and variable sunshine. All the time it is growing (except when dormant). Next we chop it down, debark it, cut it into the maximum number of saleable pieces, stuff it in a kiln to dry it out and then we want to cut perfectly straight pieces out the boards. Its not shocking to me that some of it will behave differently when cut. If you think a lumber grader looks at each board individually and carefully examines it, I suggest you take a trip to a mill. They do their best.

I am working on a project involving a great number of strips like you mention. All of the parts were cut from FAS Cherry stock and some of them deformed while cutting. I managed to get it all to fit with some jigs while cutting.

Good luck with your project.

http://i272.photobucket.com/albums/jj176/Brad805/House%20Stairs/DSC01952.jpg

[John Czaplicki]

Just updated my info with location....didn't know it wasn't there...thanks.

Brad, I hear what your saying, and I have a lot to learn, but when I say "unacceptable" I mean these strips were cork screws. I was actually hoping it was something I did, or did not do.