Pecan won't stay flat? Especially with resawing.

[Matthew Schneider]

After resawing pecan on my bandsaw, it instantly cups. At first I thought the blade might be flexing, but both pieces will cup symmetrically towards the blade. If I mill the pieces, they'll just warp again. Waiting weeks and trying again doesn't seem to help either.

I now have a number of very thin boards that have been inside for months, but if I try to joint them they'll still warp. Is pecan just like that? Could it still not be dry after so long? Or is it just a thing with thin boards? I've tried it with poplar as well with mixed but generally better results. My thicker pecan boards are warping too, but not nearly as badly.

I'm presently trying it with maple. So far the same thing after resawing it, but I haven't yet seen what it'll do after milling it again.

I've tried clamping the thin pecan flat for some time. It helped a little bit with some of them, but not that much or reliably.

[Ralph Boumenot]

It sounds like the stock is case hardened. As you bandsaw the stock should stay flat. With it cupping like that it is an indication that it was not dried properly.

[Robert Engel]

I suspect the wood is not dry enough. Resawing is the most radical thing you can do to a board in terms of moisture imbalance, especially when resawing from very thick stock.

Two things cause wood to warp:

A) moisture imbalances (good excuse to buy a moisture meter)

B) internal stresses

Things to consider:

- How are you storing the wood? Stickered? Air flow? Ambient humidity?
- How long is the wood out of the sawmill? It can take 2 years or more for a 4/4 board to air dry.
- If the wood is cupping even after clamping, then it might be stresses in the wood. I usually clamp the boards together in stickers and keep in a climate controlled room for a week or so. If you resaw thin stock and don't keep it flat when drying it will cup almost 100% of the time.
- Use Quarter sawn wood when possible it gives best results when resawing.

Most recently, I resawed some wide cypress boards for drawer bottoms. I immediately put them in a stickered stack, moved to an air conditioned room, and put a few weights on top. 2 weeks later I check the stack and they boards are cupped about 1/2". They eventually came around after some more convincing and I was still able to use them but lesson learned: use clamps, not weights.

Also keep in mind when you take the wood out of the clamps, things can change quickly. I've had resawn boards warp on me in a matter of 30 minutes just due to a fan inadvertently blowing air across it.

[glenn bradley]

In a word, no; this is not just how pecan is. I have built several large pieces out of pecan. I have never found it to be an "active" wood. I would assume improper stock storage/preparation by your supplier or the stock is just not ready yet to be worked.

[John TenEyck]

A moisture meter and RH vs. EMC chart are your best friends to diagnose problems like this. Better still, they help you avoid it.

FWIW, it often only takes a few months for 4/4 stock to air dry; depends upon the time of year, what the wood is, and where you live. Nevertheless, most often AD stock needs to be further dried before it's suitable for use building furniture, and that can take at least several weeks and often months. IMHO, any wood you purchase is suspect until you measure the moisture content outside and at the core.

John

[Howard Acheson]

What you are seeing is what is called a "barrel cut". It is caused by either insufficient blade tension, incorrect blade, damaged blade or improper alignment of blade guides. Go to a library or purchase Mark Duginske's Band-Saw Handbook for more details about the problem and how to solve it. It's an excellent book that every band saw user should have in his library.

[Danny Hamsley]

Pecan is the devil. I have sawn thousands of BF of it, and it is one of the more difficult woods to dry. Also, there can be a lot of growth tension in pecan, especially the fast grown orchard pecan. Nothing you can do about it. It can vary a great deal from tree to tree. Also, as it dries, it is bad to kink at the knots. Beautiful but difficult wood. Some turns out flat and great, some turns out just the opposite. Quartersawing tames it somewhat. That is your best bet, quartersawn pecan.

[Matthew Schneider]

Thanks for all the responses.

Casehardening sounds like it might match the description. I guess I'll try buying it from somewhere else next time and see if I have more luck with it.

Barrel cut sounds like what I thought was going on at first, but I think the pieces should fit together, whereas I'm getting something that looks like a pair of parentheses: ()

The bigger problem compared to it warping straight from the bandsaw is that it seems that there's nothing I can do to flatten it afterwards... it always just warps again. I think that sounds like internal stresses, maybe caused by improper drying?

It's possible I'm not storing it properly. I have 100 board feet layed down on three even piles on the floor by species, with a large cloth over to keep dirt off. But I have some really thin boards of pecan off by themselves on a shelf that I'd expect would be dry by now that I can't flatten.

[Mike Henderson]

In a word, no; this is not just how pecan is. I have built several large pieces out of pecan. I have never found it to be an "active" wood. I would assume improper stock storage/preparation by your supplier or the stock is just not ready yet to be worked.

Me, too. I've used a fair amount of pecan and it milled fine. Pecan is a type of hickory, if I remember correctly.

Mike

[Yonak Hawkins]

My experience is the same as Danny's. Pecan is a quirky wood. Some will curl ; some stays straight. I don't think there's much you could have done to prevent it nor anything can do now to correct it.

[Danny Hamsley]

I have air dried and kiln dried thousands of BF of hardwood lumber. Most of the bad things like warp and cup happen as wood dries from green to 25% moisture content. When air drying, the boards are naturally conditioned at night when the humidity rises, allowing for the shell and core to equalize and produces gentle drying. Then, once below 25% moisture content, you can finish in the kiln to the final moisture content. Here is a pic of some quartersawn white oak on the bottom and some cherry on the top (sorry for the blurry picture). This stack has been air drying for over 6 months. You can see very little cup because of the gentle air drying.

IMG_1409.jpg

Here is some pecan that has been air drying for 1 year. A much different picture. The 6/4 cherry has gone fine. It is on the bottom. The pecan on the top is a different story. Very difficult to dry straight without cup, warp/twist, and bow. That is why I call it the devil.

IMG_1411.jpg

[glenn bradley]

I wonder if this is a geographical (environmental) problem? If so, I better never move this thing to a climate with wide humidity swings or it may self destruct

Kit-Hut-(227).jpg

Seriously though, I appreciate the info from folks who actually process this wood from tree to lumber. No better source for info than someone who has been there. I'm lucky to be in an area where pecan seems to behave and appreciate the sawyers who bring it to market . . . wait a minute . . . lucky!?!

Danny H. is right, this wood is the devil. After I finished the kitchen unit shown above I had to send all involved cutters out to be sharpened . . . some woods are hard but, pecan is one of the more abusive materials I have worked with. Its the devil (a role possibly shared with wenge . . . or ipe . . . or . . . ).

[Robert Engel]

I think that sounds like internal stresses, maybe caused by improper drying?

It's possible I'm not storing it properly. I have 100 board feet layed down on three even piles on the floor by species, with a large cloth over to keep dirt off. But I have some really thin boards of pecan off by themselves on a shelf that I'd expect would be dry by now that I can't flatten.

My understanding is internal stresses are inherent in the wood, but can become evident during the drying process as Danny has illustrated ^^.

Storing may be an issue. You don't mention, but is it stickered? I use 4X4's on the bottom every 16 inches and 1X stickers between layers. Good air flow is required. I would get rid of the cloth. Don't stack against a wall or in a corner.

[Cody Colston]

No doubt Pecan/Hickory is a difficult wood to dry properly (and saw, too). There is always a high percentage of degrade from warping. What one buys at a lumber dealer is the stock that somewhat behaved. You don't see the stuff that was too poor to make grade. One also doesn't know how the wood was initially dried and without a moisture meter, how dry it is when purchased. The core could still be wetter than the shell, even after months in your shop.

One thing you can try is to immediately place the two resawn pieces together, sawn face to sawn face. Stack them with some weight on them and let the stock acclimate further in your shop. That may or may not limit the warp enough to joint it flat (and have it stay flat).

[Dennis Ford]

I don't have anywhere near the experience that Danny does but have noticed that any wood which goes from wet to dry with minimal warping will tend to stay straight during minor moisture changes. Also any piece that warps a lot when drying is much more likely to warp again when machined. Limbs are a good example; they warp from stress while drying and will warp again every time they are machined. Nice straight trees make straight lumber, crooked trees make crooked lumber regardless of the variety.