Case hardened wood

[Alex Zeller]

I was recently given a little over 100 bdft of 8/4 cherry that I believe was kiln dried improperly. Most of it is warped (hence why I think it's case hardened). I just moved it into my shop so I figured I would wait a few weeks before checking it. The wood has been sitting inside an unheated shed for at least 15 years. I know this because the mill it was bought from closed back in 2008. I helped remove it from the shed so I know how it was stored. It was not stacked on top of each other and was up in the rafters. I'm guessing by now the moisture in the wood has equalized by now.

I've seen a test that will tell if it's case hardened where a section of the wood is cut into a U shape. If the 'legs' move in different directions then it's a sign of case hardening. Is there another test? Of course it could be just from natural stresses in the log. Either way after sitting so long what are the odds that once I start to mill it the wood isn't going to move? While the lumber is 10' to 12' long I figured I would only make stuff 2' and shorter with it.

[Kevin Jenness]

If it's case hardened the wood will probably cup when you mill the first face and relieve the tension on that side. Warping can come from many other causes. I would block out some pieces, give them a rest, rough mill and rest again, then mill to dimension. After processing a few pieces you will get an idea how usable the batch is.

[Alan Lightstone]

I found an interesting link that shows a test to see if the wood is case hardened. Might be worth a try, it's simple enough.

https://forestrynews.blogs.govdelivery.com/2021/10/07/casehardening-of-lumber-what-it-is-and-how-to-relieve-it/#:~:text=However%2C%20drying%20stress%E2%80%94comm only%20called,later%20re%2Dsawn%20or%20machined.

[Prashun Patel]

You just cannot tell from the below information.

Warp doesn’t mean it’s case hardened necessarily. The short lengths you need will work in your favor.

You have to start using it to tell. Do some tests. Also, your chances of stability will increase if you are willing to rip the boards into more narrow sections use the quartersawn parts of the board

[Bill Dufour]

Watch out for the rips. It is likely to twist and bind on the blade causing kickback. Think about how you will turn off the saw in the middle of a rip if it start to bind without removing your grip on the wood.
Bill D.

[Prashun Patel]

Rip them on a bandsaw.
Rough wood on a table saw is not a good idea in my shop.
YMMV.

[Richard Coers]

If it's case hardened, you will usually see some honeycombing on the inside. Is there a lot of sapwood on the cherry? It shrinks at a different rate than heartwood and can cause a lot of movement in the boards during drying. But as others have said, you can't see casehardening just by looking at the wood. Also the test you are talking about is not a U cut, it's just a bandsaw kerf cut into the board. The U develops if the case hardening is bad and the board really opens up. A moisture meter will also tell you it is case hardened because the center of the board will have a higher moisture level than the outside.

[Maurice Mcmurry]

I found an interesting link that shows a test to see if the wood is case hardened. Might be worth a try, it's simple enough.

https://forestrynews.blogs.govdelivery.com/2021/10/07/casehardening-of-lumber-what-it-is-and-how-to-relieve-it/#:~:text=However%2C%20drying%20stress%E2%80%94comm only%20called,later%20re%2Dsawn%20or%20machined.

Great article! I am glad to have learned about the test. I am also glad to see that my experiments with going very hot in the last stages of kiln drying is producing very stable wood.

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[Alex Zeller]

I actually read that article. Once the wood has been in my shop for a few weeks I'll test one of the worst pieces. The article says "Once casehardening or moisture gradient is observed, additional stress relief and/or equalization are required" but it doesn't actually say what stress relief or equalization. I'm assuming that sitting so long there's not going to be much moisture gradient present.

I don't have any plans for the wood but I would like to know what I can expect from it so I don't plan a project for the wood that it'll be able to do. One of the boards is a 12+" wide 12' that's perfectly flat. Not knowing if it was dried in the same manor as the rest means it could also be case hardened. Like others have said, I would like to know before I put it on the table saw and find out the hard way that it also wants to twist.

[Kevin Jenness]

If your lumber is case hardened you are not going to change the condition now. Equalization is a kiln drying practice using steam to put moisture back into the outer layer of the wood at the end of the kiln cycle once the core has hit the target mc. True case hardening results when the shell "sets" in size as it dries too rapidly and is unable to shrink around a wet core. When the core dries it creates tension in the shell. If the tension is great enough you get honeycomb checks. If it's not that great it's invisible but causes milling problems.

There's no particular reason to think your lumber is case hardened just because it's warped. It's safer to block out rough lumber, especially if twisted, on the bandsaw. Just dice some up, give it some time, and evaluate it based on behavior.

[Alex Zeller]

The main reason why I think it might be is because the person who gave me the wood felt it was. He didn't want to mess with it and was tired of it taking up room. It could just be from how the tree grew. I should just be patent and after it's had a few weeks in my shop cut one of the boards down to 2' so I can try the test. I'm thinking the best way to handle it is to cut it on the chopsaw and then flatten one surface and edge. Then I can rip the other edge off on the bandsaw (which should give me a good idea how much it's going to twist. Finally run it through the thicknesser. I''ll let it sit for a week or to in a way air can get to every side and see if it remains flat.

My problem is now I have it I feel like I must make something with it. I recently made an oval cheval mirror. The wife loves it but when I showed her a 3d carved flower I made on the cnc she now thinks it would be "awsome" if I did either Irish themed scroll work or flowers on the oval frame. Of course she watched me bring the wood into the shop and made the comment of what she felt the wood could be used for.

[Maurice Mcmurry]

Cherry is a lovely wood. 100 BF for free is a great score. I hope you find it to very useable.

[Lee Schierer]

I'm thinking the best way to handle it is to cut it on the chopsaw and then flatten one surface and edge. Then I can rip the other edge off on the bandsaw (which should give me a good idea how much it's going to twist. Finally run it through the thicknesser. I''ll let it sit for a week or to in a way air can get to every side and see if it remains flat.

Be sure to remove equal amounts of waste from each wide face of each board. If there is unequal moisture, removing all of the waste from one surface is a sure way to produce cupping, etc. If you don't have a moisture meter now would be a good time to get one and use it to insure that the wood is in fact dry enough to work. I had the misfortune of getting some maple from a "shed" that had been there for years and years and it was far from being dry. The wood had previously been kiln dried.

[Scott T Smith]

After 15 years of equalization, I would be highly surprised if that wood was case hardened (even if it was 15 years ago).

Warpage in dry lumber is not usually a sign of case hardening - it is a sign of either poor grade lumber or in some instances a poor milling technique.