Freshley kilned lumber warping when ripped

[Joe Hillmann]

I picked up a few red oak boards from a nearby sawmill yesterday to make into picture frame molding, when I got there they were unloading the kiln and pulled my boards off of one of the piles they just pulled from the kiln. When I started working on them I decided to rip them into 1.5" strips before planing them due to the cup that some of them had. As I was ripping them the strips were bowing maybe 4 or 5 inches over there length. And with every strip I cut off what was left of the boards warped more and more until it was as badly warped as the rest of the strips.

I have used this exact same method in the past to make picture frame molding 2 or three time with red oak from the same mill and bowing was never problem. So my question is, Was the bowing caused by the wood being so recently kilned or did all the boards I got just come from a tree with stress in it?

[Andrew Gibson]

my guess is that the boards need to acclimate to your shop. if they just came out of the kiln they are most likely at a very low moisture content and your shop is not as dry as the kiln. the boards may actually straighten back out as they acclimate. if you have a moisture meter you could check the MC and see where the wood stands. I would definitely let the wood acclimate for a week or so before trying to do to much with it.

[Mark Bolton]

I would say you've either got some boards from a gnarly tree or they are improperly dried/case hardened. If they are pretty straight grained I would put it on the drying.

We buy most 1C or FAS and have never acclimated material. When ripping face frame material for instance (1.5" wide) we may get an occasional board that will pinch, spread, hook, while being ripped but its rare. Our supplier however does a very good job drying. I can often run 8"+ boards for face frames and have every one be straight.

[Howard Acheson]

I was told years ago never to use wood directly from the dryer. Instead, give it 2-4 weeks for the drying to even out throughout the thickness of the board. The outer surfaces of the wood will always be at a different moisture level than the interior of the board.

[Joe Hillmann]

The wood is select grade but not very straight grained, just no or very small knots. I have gotten wood from this sawmill in the past for the same job and I don't remember it moving at all. The largest frames I plan to make are 8x10 so even the worst bowed pieces will still be useable but the bowing made it difficult to work. I have two boards left that I will wait a week or so before I start milling it to see if the bowing is less of an issue.

[Mel Fulks]

If you run the profiles on the convex side it will straighten some. The worst drying related problem Ive seen with oak is brashness ( brittle splintery) caused by over doing. For that reason we have always bought from one particularly good dealer. I have not seen brash lumber remedied by ageing.

[Richard Coers]

The supplier I buy from will flat stack the lumber coming out of the kiln. If acclimation was needed for good wood, they would have to sticker it. Since they don't, there is no way that board in the center of the stack is going to acclimate. The center of the board better not be different coming out of the kiln. If their is a differential, it will be after sitting around for a while. Just out of the kiln should be the same all the way through. I say it can either be bad lumber, or not equalized in the kiln. Take it back.



I was told years ago never to use wood directly from the dryer. Instead, give it 2-4 weeks for the drying to even out throughout the thickness of the board. The outer surfaces of the wood will always be at a different moisture level than the interior of the board.

[John TenEyck]

I'm with Howard; I would never use wood immediately out of the kiln. I would love to actually measure the moisture content of a board fresh from the kiln cut as the OP did. I'll bet it varies several percent from edge to center, especially if it wasn't reconditioned at the end. Regardless, it is just prudent to let wood acclimate to your shop for a week or two before you use it so that you know it will be the same MC throughout and at equilibrium with your shop.

John

[Mark Bolton]

Regardless, it is just prudent to let wood acclimate to your shop for a week or two before you use it so that you know it will be the same MC throughout and at equilibrium with your shop. John

Unfortunately this just isnt the case for even big production shops. The material comes in and often times goes straight to the line. I dont know that many manufacturers/shops would tolerate being told the reason their wood went whacky is because they didnt warehouse it long enough. I expect my wood from my suppliers to arrive in usable condition.

As Richard said, material out of the kiln is flat stacked which means there is no acclimatizing happening even if they, or I, were to sit on it. I have no way to store several thousand feet of material stickered to where it even "could" acclimatize. My material spends a tad more time at my supplier because of s2s, SLR1E, but its not resting there that long, they like to turn material quickly.

To each his own but when my lumber hits the floor its usually for a pending job and goes straight to work sometimes before the last board is even off the truck and while a few randy boards are par for the course I can honestly say its 1 in 20-30 if that.

[Mel Fulks]

If the wood is not full of cracks,honey combing,twisted back and forth like bacon, and is not knotier than grade allows; I think there is little reason to take it back .Like Mark I believe in buying from the same place all the time.We bought some oak once that was so brash it was costing too much in labor ,glue ,and tape to repair splintering edges ;when we went back to our regular dealer that ended.

[Jim Andrew]

I had some ash that I dried, jointed it flat and surfaced it, then later went to use it and it had gone nuts. Let it set a few weeks and it straightened back out.

[John TenEyck]

Production shops like yours should expect high quality material from their suppliers because of the volume you buy. Hobbiests like me have far fewer options but the wood we get almost never comes straight from a kiln or dense stacked much less dense stacked and wrapped. I've bought wood from mail order two states away, local lumber shops, even individuals who mill and AD their lumber. (The only wood I am confident in is the stuff I mill myself and dry in a dehumidification kiln.) Clearly, what you buy and what I buy are two different animals. I can't demand anything, much less constant or consistent MC, and it sounded from the OP's post that he was in much the same situation although he was at least getting it straight from the kiln, although that guarantees nothing if you are a small purchaser. When you can't control your lumber source, you learn to use and trust your moisture meter. Mine has proven that the wood I buy is almost never close in MC to the EMC of my shop, especially in the Summer months because my shop is humidity controlled. I've tried using it straight away with a couple of painful results. Conditioning my lumber until the MC is at/close to equilibrium has eliminated any further surprises. We work in different woodworking worlds.

John

[Scott T Smith]

Hi Joe. I'm a kiln operator. A couple of questions. First, is there a correlation between the direction of the warp and the grain pattern on the board? Second, what are the board dimensions? Third, do the strips all warp the same way, or do the outer strips from the board bend towards the inside of the board and the center strip from the board stay relatively straight? Fourth, does there appear to be any sapwood in the boards?

If there is a drying related problem, there should be some consistency in the direction that the strips warp relative to their position in the board. If there is no consistency, it sounds like the underlying problem may have been tension in the log.