[OP]
Member
I just resawed a beautiful piece of 8/4 Qsawn white oak in the hopes of producing bookmatched pieces for a tabletop. To my horror both pieces came off the saw really warped, which i assume is internal stresses being relieved. My questions for theose with more experience:
1) Could i have done anything to avoid this?
2) is there anything I can do to re-straighten the boards? Steaming?
If i try to joint and plane them i will never get the 3/4 thuckness i want. The warp is too severe.
thanks!
Member
I have had this issue resawing oak to 3/8" thickness and found that if I keep the ortiginal board in my shop a few days before re-sawing it , this issue goes away. Gives the wood a chance to warm up to the temp that I saw it in. At least it has worked for me.
No PHD, but I have a DD 214
Contributor
Temp. was not likely the cause, more likely it was the moisture content. When the center of the board has a higher MC than the outside faces the boards will spread apart as the original board is resawn. If it's lower in the center, the boards will try to pinch together. The solution is still the same - don't work wood until it's been in your shop long enough to come to the EMC of your shop. For the OP, all you can do now is wait; often the boards will straighten out again after the MC equilibrates within the cut board. Just leave it standing up or on edge on the bench and leave it for a few days. If it doesn't straighten out, not much you can do that will be permanent.
John
Guest
(1) Not if the movement was due to wood tension.Originally Posted by Clay Fails
(2) Not if the movement was due to wood tension.
If, OTOH, the movement was due to a moisture imbalance, setting the pieces aside for a time may result in flatter stock.
BTW, I've seen so many times people note that movement after resawing is because of a moisture imbalance. But we've all had reactive wood that when ripped on the table saw (for example) pinches the splitter or riving knife. This is due to internal stresses of the wood being released. Well, resawing can release the same sort of internal stresses.
Last edited by Phil Thien; 10-23-2014 at 10:53 PM.
Member
How much tension can their be in a quartersawn board?
Member
There can be tension in a board regardless of grain orientation. It results from imbalance between shrinkage in the outside and the inside of the board, not from grain orientation (i.e. the radial vs tangential shrinkage that makes qs more stable after drying).
[OP]
Member
Thanks for the input. This board was in my shop for about a year and a half before yesterday. It may still be due to unequal moisture content between outside fibers and inside fibers. Hoping it will straighten itself, but not betting on it!
Contributor
Re-sawing is a crap shoot. Plain and simple. You never know what will happen.
Never, under any circumstances, consume a laxative and sleeping pill, on the same night
Member
It can have a lot to do with how well the wood was dried in the first place. This is more of a problem with kiln dried wood where stress can be dried into the wood. Much less of a problem with air dried wood, solar kiln dried wood, and vacuum kiln dried woods. Production 'kill dried' wood can really spring a lot. With the other methods of drying, I often get no movement/spring at all.
robo hippy
Member
I disagree that there is risk in re-sawing but I can agree that kiln dried wood is probably more prone to a release reaction.
Contributor
Very true. The OP's result could just as easily have been caused by tension as moisture imbalance. Probably more likely seeing now that the wood had been in his shop for 18 months.
John
Member
Jim, there are several ways that tension can be present in a QS board. The most common way is if the log had an off-centered pith, which indicates internal stresses in the lumber (comes from a leaning tree). Other ways are if there is pith wood or sapwood present along the edges of the board.
8/4 white oak takes a long time to acclimate; however a year and a half is more than sufficient. Additionally, even if the board was improperly dried (case hardened) it would still most likely have equalized over the course of a year and a half.
Clay - can you post some photo's of the board? Show close-ups of the end grain (include as much of it across the width of the board as possible), as well as photo's that show the cup that developed (put the board halves back together for the photo).
Member
It would have equalized MC, but if it was case-hardened during drying, that is permanent damage that won't be undone by equalizing moisture content.
Case hardening occurs when the outside and inside of the board are dried at rates that differ too much. The outside dries first, and tries to shrink. The still moist inner parts haven't shrunk yet, so the outer part comes to be in tension. It reacts to the tension by stretching horizontally and microfracturing. Drying "sets" the outer layer in this stretched state. Then when the inner part finally dries and shrinks, the outer part can't follow it and comes to be in compression.
[OP]
Member
Will do Scott, as soon as I get them out of my last ditch clamping effort to straighten them! Probably tomorrow I can upload photos.
Member
Hate that man, and I've been there. Not seeing the boards, I cant say it's a lost cause. However, I have tried a few things that have helped with cherry. Don't know it would work for you but ya never know. When I resaw a couple boards and see first sign of them getting funky, I'll put them back to back (wet faces to outside) tape them together, and put them in a black garbage bag wrap as tight as I can and put them under weight for a couple weeks. I've had them level out. Take them out of the bag and put them back under weight, and leave them another week and see how it goes. Like I said some times it works some times it was just not meant to be. If it happens a few times from the same mill that's doing the drying, I'd find another source they don't know what they are doing.
Posting Permissions
Reply With Quote