Have the 6/4 piece of cherry that's 5 7/8" wide and ~7' long. Had it finished to S2S and and edge.
Then I cut it in half lengthwise. The piece w/the jointed edge was fine. The piece with the one rough edge (that I then sawed off to make 2 even width pieces) warped (bent) along the long axis. This is no good, needless to say.
Why did only half of a single board do this? How do I fix? (I've got i clamped down o try to ingrain a new memory of straightness into the board, but this may take forever. A more timely/effective soltution is desired).
If you look closely at the grain of the two halves, you will probably note a significant difference. If this piece of cherry came from a large limb or from a trunk that had grown out at an angle, one part of the board would have grown under tension, one side under compression. Ripping the board has now removed one half of the force that was helping to maintain equilibrium and it warped.
That's one possibility. Another is that one board has picked up or lost more moisture on one face than the other. Dampen the concave side and lay it on some stretchers so air can get at all sides evenly and place a weight on it to help. Amount of weight you ask? Leeseee...less than the weight of a car engine but more than a loaf of bread.... 30-40lbs should be about right.
Worth a shot since what you have now can only be cut to make smaller pieces and re-milled.
Because wood comes from trees, and trees grow differently depending on if it was a wet year, or if that side of the tree is shaded by other vegitation, etc. This results in differing desities throughout the board and corrsponding internal stresses. Sometimes, this results in what you observed. Careful stock selection (clear, straight grain) can mitigate this risk, but not totally eliminate it.
In short, it was probably not preventable, sometimes that just happens.
"Training" a board doesn't work. You can remove a cup temporarily with the application of a little moisture/sunshine (leave a board on the lawn in the summer and it will cup down. But that is just temporary until the moisture content equalizes again.
Options:
The expensive option is to buy a jointer.
You can configure a router table fence (with a slightly offset infeed fence and the outfeed fence tangent to the edge of a straight cutter) to function like a jointer
Fasten the bent board to a straight one such that the straight board will ride along your table saw's rip fence, while just the bent board makes contact with the saw blade.... rip away.
hard telling. wood is a natural material, so it's properties will vary from point to point. the wood closer to the waney edge was a different age than the wood closer to the center of the tree. how the wood was stacked for kiln drying can make a big difference, as can how fast it was dried.
generally speaking you can't.
if you can, use that piece in a location where it will be held straight by other pieces, or cut it into short enough pieces that the warp ceases to be a factor.
alternatively, you could try ripping it in half, reversing the halves and gluing them back together- so they will pull each other straight. given the history of this board, I doubt that the two halves will have equivalent warpage, however.
if I were trying to coax it back to straight with clamps I think I'd overshoot the curve by a fair bit.
whatever you do, if the board is going to have to hold it's own shape (freestanding it's length, not bound to another member) within the finished article let it sit unrestrained for a while before using it. it would suck to get it bent back to straight and make the door stile or whatever out of it only to have it go wild again a few days later....
The piece that bent have sapwood in it? Good bet that'd bend.
Were the annual rings consistent in interval? Difference is what you see if you have "reaction" wood.
Did you rip close to the heart? Smaller radius rings pull harder.
It's wood, so you take your best shot based on what you observe. If any of the conditions above pertained when you evaluated the wood for cutting, you might well have thought of using the piece at its largest. I mentally discard the heart (pith) and sapwood as I plan the cuts.
I've tried this many times, with very limited success. As other posters have noted, the plank had inbuilt stress, probably through bad seasoning. By ripping it, you've released that stress and the two halfs have now found their equilibrium. All you can do with the bent one really is to leave it as is is and cut usable bits from it now that it is stable. And that isn't to say that, if you rip it again, you won't release a bit more stress...
The answer to that is yes, you can. Steaming relieves the stress in the wood. However, there's usually some spring back when you take it out of the clamps, so you'd need to guesstimate it and overbend slightly. It might be worth it if it's a particularly precious piece of wood.
: You can steam wood to bend it. Can you steam wood to straighten it?
I believe that kiln managers can recondition timbers, but if tried on a home-workshop basis, I reckon that the item would need to be under pressure during the steaming/drying cycle.
I've often thought of it, but never tried it - possibly because the process is likely to require greater control than possible in the workshop.
Jeff G
-- Jeff Gorman, West Yorkshire, UK Email address is username@ISP username is amgron ISP is clara.co.uk Website
Aaaahhhh! You folks gotta stop abusing... I better stop here since I'm sure anything I say will be convoluted further.
I can cut it up to nice 18" pieces and throw it into the fireplace this evening. Supposed to get a nice little snow storm.
Actually, I'm debating whether to try and salvage it. Over a 80" length, the bend start about 3/4 of the along and bends out ~1" by the end. This wood is going to be fastened to the side panel of an tv armoire, partly in an effort to restrain the panel from bowing out where the large opening for the TV is. I'm thinking I'm going to rabbet the piece and fasten it w/biscuits to the panel. Where the bend in the wood is, the panel will be stiffened by two shelves about
14" apart, which would restrain the wood from it's desire to bend. I'm just a little concerned about unthought of stresses from which I might find undesireable consequences later (like, when the dang thing is completed).
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