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red oak TOO dry?5/21
I have been having problems making straight parts lately only with red oak. I flatten all frame material on the jointer then run thru thru the planer. When it comes out of the planer it is not flat anymore. This is only happening with red oak...not poplar, maple, cherry, alder etc. I measured moisture with my Wagner meter and it is consistently at 4.5-5.1 %. This oak is from a major mill who i have been using for a couple years now. Going to talk with supplier monday. What should i do and will this cause me problems with warranty down the road?
This is off Wiki:
Case hardening describes lumber or timber that has been dried too rapidly. Wood initially dries from the shell (surface), shrinking the shell and putting the core under compression. When this shell is at a low moisture content it will 'set' and resist shrinkage. The core of the wood is still at a higher moisture content. This core will then begin to dry and shrink, however any shrinkage is resisted by the already 'set' shell. This leads to reversed stresses; compression stresses on the shell and tension stresses in the core. This results in unrelieved stress called case hardening. Case-hardened wood may warp considerably and dangerously when the stress is released by sawing.
The wood is effectively defective. You should be able to return what you haven't used at the very least. Don't keep it.
Should i request that they take care of any warranty work that should arise?
My supplier has the exact same moisture meter as i do so i will be able to see what theirs reads. I just went out and measured more...some of it is down in the 3.5-4% range !
Them take care of warranty work? All they might do is replace the material. It'll take a lawyer to get any more than that. They will likely claim you knew there was an issue and you continued to use the product. How could they be responsible for you using faulty product? I'm surprised you did continue to use problematic material. When I have issues, everything stops and it gets corrected right NOW!
Been using oak from that mill for a couple years with no problems. Only the last 3 weeks or so i have had problems and it has only been 200 bf or so. Sorry for the confusion.
Indeed, casehardening results in immediate warp when machining.
The description has several points that are incorrect
Case hardening describes lumber or timber that has been dried too rapidly. Wrong...even when dried at the normal accepted rate,mood does caseharden.
Wood initially dries from the shell (surface), shrinking the shell and putting the core under compression. Partly true, but the shell is also under tension and it is this tension exceeds the proportional limit and moves into the plastic range that stress becomes permanent, which is casehardening. So, it develops very early in drying. If the tension exceeds the strength, then a check occurs.
When this shell is at a low moisture content it will 'set' and resist shrinkage. Totally incorrect. Set occurs at high MCs, not low. The wood is too strong at low MCs to develop set.
The core of the wood is still at a higher moisture content. This core will then begin to dry and shrink, however any shrinkage is resisted by the already 'set' shell. This leads to reversed stresses; compression stresses on the shell and tension stresses in the core. This results in unrelieved stress called case hardening. Correction...set causes casehardening, not unrelieved stress.
A better description is in DRYING HARDWOOD LUMBER.
Casehardening in dried hardwood lumber for furniture, cabinets, etc. is totally unacceptable and is considered incorrectly dried lumber. There are tests for measuring casehardening. Lumber should be easily returned for credit.
However, subsequent damages will be hard to collect, but I have seen it in a court case where the award was $3 million. Very expensive to pursue legally.
This incident makes a good argument for checking every load that comes in for moisture content. I venture to say it is rarely done consistently, but would save a lot of heartburn.
My supplier measured the same readings i took and we both have the Wagner 220.
Tried resawing some today...terrible.
Low moisture content does not cause or contribute to casehardening.
It is virtually impossible to dry lumber to 3.5% MC. Even a steam kiln cannot to that.
You should edit the Wiki post
The information is in DRYING HARDWOOD LUMBER, see page 99 plus. It is free, can be copied, etc. In fact, this book and its previous versions are widely available and represent the best source of info on drying. Canada has similar info. So, why would someone spend the time to make a wiki post that is so far off from the published info?
Note that many of the smaller dehumidification kilns do not have the ability to relieve casehardening. Is it possible that this is how your lumber was dried? Also, if we air dry carefully, there is close to zero casehardening, as the high humidity every morning relieves a bit of this stress. So, a DH kiln with well air dried would be ok.
So my salesman says the mill rep says he "thinks" the wood will stabilize once it is milled. Salesman says they surfaced the rest of the material and most of it has stayed flat. The guy running the machines said the wood looks good.
Maybe I should invite them over for a 101 lesson? I can tell you that their idea of flat and my idea of flat are nothing alike.
This wood warps AS it is being run across the jointer! Time to order my oak from another supplier but i really hope they get some higher MC stuff in.
Salesman is incorrect