Matt you are correct, the actual dimension was 1 1/4", which is 5/4, and the resawn wood is 9/16, not 10/16 (5/8). If I had started with 6/4 the 1/8" bow could be jointed away.Originally Posted by Matt Day
Thanks,
Len
[OP]
Contributor
Matt you are correct, the actual dimension was 1 1/4", which is 5/4, and the resawn wood is 9/16, not 10/16 (5/8). If I had started with 6/4 the 1/8" bow could be jointed away.
Thanks,
Len
Last edited by Chris Padilla; 06-22-2015 at 11:58 AM.
Member
A very slight tangent.....
Most will agree on a "balanced' approach to finishing.You can apply that to resawing as well.Test it for yourself,take a resaw,leave one side jointed or planed....and leave the other side with the kerf marks from BS.See which way it "bows".To a lessor degree,the same is true for your sanded finishes,one side vs other(the more drastic the diff,the more it shows up).Good luck with your table,BW
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Have you considered plain-sawn maple, with 1/8" veneers cut from the piece you have?
When I started woodworking, I didn't know squat. I have progressed in 30 years - now I do know squat.
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I don't get it. What is that supposed to tell you?
Never, under any circumstances, consume a laxative and sleeping pill, on the same night
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have any idea what issue this is in?
David
Confidence: That feeling you get before fully understanding a situation (Anonymous)
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I'd need a bit of convincing on the dropping deal - it'd presumably have to shock the wood hard enough to cause problem/highly stressed fibres to fail or stretch for it to work.
There's to my mind two naturally occurring causes of warping in the wood - moisture induced stress, and locked in stress.
With moisture imbalance one face of your resawn board is wetter than the other when cut free. So it as a result promptly warps as it dries out.
It's possble in this situation (presuming poor kilning) that uneven moisture content may also have pulled a bow into/put stress into the plank before the mill sawed it straight - so that what looked like a straight piece before resawing was in fact relying on this moisture induced uneven internal stress to hold it (temporarily) straight.
The other possibility is that there's as a result of the growth pattern (e.g. from uneven loading of the tree) or case hardening during kiln drying stress built into the timber independently of anything to do with moisture. Which was held in balance in the plank as received, but is made unbalanced once the board was resawn free. So it immediately warped.
Since your wood was very well dried/fully equilibriated before it was resawn Len, perhaps the latter is the greater possibility? (poor kilning seems to be a major issue these days)
If a board was straight after resawing, but got damp on one side afterwards and warped then it'd seem likely that it might straighten again as it dried (presuming it's held straight as it does so). i.e. the 'resting'/relaxed/unstressed state of the wood is basically straight. This is different to the situation in either of the above cases where the resting state of the wood is warped.
Changing this later requires the wood to stress relieve in some manner.
Steaming (which isn't all that controllable, and which may have other undesirable side effects) is one treatment that definitely causes stress relieving. Another is kilning. I'm not sure its applicable to already machined wood (it'd require a great deal of precision - it may be more applicable prior to milling), but here's a discussion on using kilning processes to stress relieve wood: http://www.woodweb.com/knowledge_bas..._stresses.html Wonder if it's the heat, or the moisture or both that do the business here? Wonder if anybody has ever made a proper investigation of the use of heat and/or moisture to straighten wood after it's been machined?
One useful point made in the piece is that if the problem is down to built in stress (rather than moisture), then the board will warp immediately when it's sawn free. If on the other hand it's down to moisture imbalance then it'll likely take some time (maybe a few hours) for the water distribution to change and for the warping to kick in...
Last edited by ian maybury; 06-22-2015 at 2:05 PM.
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I think the trick is to drop it enough times so that in addition to still being bowed, it's dented and dinged enough to require another trip through the jointer and planer to shave away the mess. After that it will be straight and flat.
Chuck Taylor
Contributor
Len, when Jason asked if the top would be in a frame I'm guessing he meant attached to an apron. Exactly how will the top be attached to the table structure? An apron with figure 8's would easily flatten the top.
Scott Vroom
I started with absolutely nothing. Now, thanks to years of hard work, careful planning, and perseverance, I find I still have most of it left.
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Len
My experience has echoed Brian's summation.
What I have done is take the face that was jointed and flip the two new board so that the jointed faces are against each other. I have then clamped them immediately coming off the bandsaw. Sometimes they stay that way for weeks.
If it helps to alleviate you beating yourself up, this same reaction could have occurred on either board later on in the project. As material is removed from the sides of the board, the internal stresses are able to relieve themselves. Sometimes even removing material equally from each side doesn't help, and the wood just does what it's going to do. If there was one sure fired way to "read a board", we all would know how to do it. You try your best.
If it doesn't straighten itself out, you might consider re-sawing the piece that didn't move for book match, and glue to a Qsawn piece of "plain" maple, or baltic birch ply, and then finish to thickness.
"The first thing you need to know, will likely be the last thing you learn." (Unknown)
Member
More from Gene Wengert here about stress relieving wood: http://www.woodweb.com/knowledge_bas...ng_Lumber.html
How a billard cue maker stress relieves maple to minimse warping: http://www.cuecomponents.com/strema.html
It's very possible that doing XYZ on occasion solves a problem, but the chances are that there's no reliable answer at the level of sawing procedure. Because the situation in the wood can vary so widely. Juddging by this lot there's some possibility that a one size fits all stress relieving process (before working on it) can leave most (but not all) timber in a relatively stable condition...
Last edited by ian maybury; 06-22-2015 at 2:32 PM.
Member
I had a 20"x10"piece of 4/4 QSWO I re-sawed a while back. When the two halves came out the other end of the bandsaw there was at least a 1/2" gap between the two halves in the middle. It might have even been 3/4", but in any case the two pieces were completely unusable.
What I finally did was take them out into my back yard and throw them into my swimming pool. A half hour later I put them into my oven at 300 degrees for an hour, then as fast as I could took them out into my garage (that is where my shop is), supported the edges with some wood strips, and put about 40lbs of weight on the center. Since the pieces were only a little more than 1/4" thick I expected them to just crack right down the middle, but they didn't. Amazing stuff that QSWO.
After a couple of hours I took all the weight off and they looked to be aaaaaalmost flat. After a couple of passes through my drum sander, they were in a usable condition. I didn't really expect them to maintain that flatness so I left them in the garage for a couple of weeks. During that time we had some warm days and some cold rainy days, but they held their shape. Then I put them in the house for a week or so and they still held it.
If they ever do decide they want to warp again, they are going to damage a really nice dart board cabinet. It was a present for my son to put in his new shop which for now is simply a 30x50 steel building. I would guess that the summer temps in there hit at least 130 in the summer but at least it's a dry heat. :-) In the winter it gets cold and humid but no problems yet.
The bottom line of all this is that maybe you could try steaming the pieces.
Wayne
P.S. For those of you in the north I know that Cold is relative and here it rarely freezes. And for those of you in the south (Like Baja for example) hot is relative too, but we have had a few 110+ days.
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That's an interesting idea. I wonder if, with a "complex" piece of wood, it would be wise to wet the outsides before resawing?
Member
IMO, it's primarily the heat, with steam / moisture only aiding to distribute the heat deeply into the cells.
I say this based on one simple fact: violin bowmakers set the curve of their bows with nothing but heat, and that curve remains, under a bit of stress, for decades & even centuries.
I have always assumed that the heat softens the lignin in the cells, allowing them to become pliable. - Just like heat softens any glue. Then the lignin cools, hardens, and Bob's your bent lamination.
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It is hard to say. It might appear to work or maybe it would have been fine had you not wet the wood. I say in this case with a piece of wood acclimated and probably dried to an acceptable 6-8% moisture content, that that would not have helped. The stress was built into the wood.
Contributor
My guess is case hardening and wood on thin side to start with. I'm skeptical about methods to straighten. I would try light jointer facing on CONVEX side ,that will often make both sides straighter at once. Use a straightedge to check progress on concave side. Try it. And as mentioned before you can resort to making it a thick veneer or facing.
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