Casehardening in Wood

[algale]

This video https://www.youtube.com/watch?v=nMzQmZNrunY by Stumpy Nubs on the subject of casehardening in lumber was interesting to me. It's a term I had not heard of. But after watching the video and reading a couple of articles https://www.extension.purdue.edu/extmed ... NR-132.pdf and https://www.fs.usda.gov/treesearch/pubs/32396 I wonder if several past forum threads about Shopsmith users having trouble ripping construction lumber might very well be the result of casehardening rather than some of the usual explanations we have offered (saw not aligned, belts not tensioned, blade dull).

[nuhobby]

I will have to check it out, thanks!

I have a 'vague' recollection that Nick and Drew had a spot on wood case-hardening many years ago, but I can't swear to it.

Chris

[Hobbyman2]

Interesting , We have all ways called this inner stress , it can also happen with any lumber when it is still to wet to use , if you listen to his definition he describes the interior of the wood as still having a high moisture content . we have ripped planed down sos lumber and watched it bow as it was being cut . its all from internal stress built up in the board . the old timers use to tell me it can also be from the way the tree lived, a lot of wind when the tree was young can make a log twist splinter inside , "we called it shake" , it can stretch and even bend , as it grows it can heal however the internal stress is still there. never heard any one refer to improper kiln drying as case hardening but have heard of improper drying . I will try to add this term to my long list of wood working vocabulary terms .

[HopefulSSer]

Yeah casehardening to me was always a term applied to steel, not wood. Very interesting though! Could very well have contributed to the issue I was having (exacerbated by the undersized power cord)

[SteveMaryland]

I watched the videos. This is very useful and relevant information, thanks for posting it.

Rushing the batch through the kiln is driven by $ economics and is therefore not going to stop. Especially in the case of SPF lumber.

I don't know much about how high-end exotic hardwood pieces are treated compared to SPF but I am sure the specialty wood dealer is going to be a lot more vested in avoiding this problem since his customers are picky craftsmen, whereas the owner of the SPF lumberyard and big-box have customers who, typically, don't care much.

Lumberyard and big-box make ALL their money on pro house- and deck-builders not on woodworking hobbyists. There is no money for them in custom-treating wood for the hobbyist market. So forget about getting the lumberyard guy to care about your needs. Economic reality.

What I have done remedially is: a) build and use a router sled to clean up warped material, and b) do long-term storage of material and expect to wait months-years before I use the material.

"Annealing" is the general term used to describe the process whereby a material with internal stresses is made stress-free. That's the objective, stress-free. Long storage time, heat-cycling and periodic planing may be the only way for the hobbyist to obtain annealed wood. No instant remedy for internal stresses.

[nuhobby]

Well, I'm glad I'm not totally bonkers! Here's the old Nick and Drew video I was thinking about:

https://shopsmith.com/ssacademy/SS_Arch ... lude_2.htm

Chris

[algale]

Well, I'm glad I'm not totally bonkers! Here's the old Nick and Drew video I was thinking about:

https://shopsmith.com/ssacademy/SS_Arch ... lude_2.htm

Chris

He seems to be talking about a different phenomenon although he also calls it casehardening. Rather than about kiln drying, Drew is talking about machining and how a previously machined surface, if allowed to stand, will case harden compared to freshly surfaced. Maybe it is related?

[Majones1]

Well, I'm glad I'm not totally bonkers! Here's the old Nick and Drew video I was thinking about:

https://shopsmith.com/ssacademy/SS_Arch ... lude_2.htm

Chris

I remember watching that session, and it’s why I sanded my joints after letting them sit for a while after cutting them. I do think the two phenomenons are directly related because I believe it is due to oxidation, which over time, and heat, reaches greater depths. Oxidation affects all materials, even granite. Exposed rocks in the desert get what’s called “desert varnish” which causes them to redden over time. If you chip off a piece you will see the true color of the rock and the depth of the oxidation.

[Ed in Tampa]

I once watched a pro rip a piece of wood where the two legs almost crossed each other. Had to stop the saw to get the lumber off. Thankfully they had a power feed and nothing bad happened. The guy hollered over to his boss that this was the second or third time today. Boss said he already complained to supplier and replacement lumber was on the way. In the meantime he had the guy cross cut the wood into shorter pieces and set them aside. The guy that owned the shop told me his supplier was trying a new mill and he thought the mill tried to rushed the drying. He claimed the outside was dry but the inside was still wet. Mill admitted fault and claimed their vacuum or pressure was not working right. Replaced suppliers Order thus supplier replaced his. I had no idea of what went on until Stumpy explained it.

[Hobbyman2]

Keep in mind a saw mill cuts green wood all day long , the kerf on their blades are quite a bit wider than the blade in some cases by as much as 3/8 inch , it allows the dust to be carried away and not bind with the blade , wet wood contains sugars , sugars get hot and melt and will attach to the blade and burn , the gullet of the blade is designed to help carry the dust away when the cut is real deep. a wide kerf blade and slowing down the saw and feed rate along with making multiple passes on such thick wood in the scenario above could help but is not the cure for using wet unstable wood . JMO