Warping Wood

[BozInOz]

I started with a Jarrah slab, 2" x 10' with rough edges.

On sunday resawed it and thicknessed it 210mmx20mm wood, and stacked it flat, on even pieces of wood.

Last night I noticed the start of the warp... its subtle but when it's already "dressed" I'm not happy jan.

Any pointers? Am I doing anything wrong? I bought it as dry, but should I get a moisture detector or does this happen with dry wood?

[whitewood]

I have limited experience with milling and then only with Paulownia. My guess is that the timber is not fully dry. Paulownia is unstable until it is completly dry and performs better if it is kln dried to 11% before it is dressed. Air drying does not appear to be enough to maintain wide stable planks.

[Exador]

Yes, it can happen with dry wood, since even "dry" wood has a certain amount of moisture in it. when you machined it, you provided a fresh surface which will then dry rapidly, causing the slight warping you have noticed. If you want to prevent it, you should machine it immediately before use (on both sides) and then finish as soon as possible. It will be especially noticeable if you have machined the "outside" face of a backsawn board.

[Takura]

The side of the timber that has cupped is the drier side, it has shrunk or the other side has expanded, meaning it has taken in moisture, you have unequal conditions on each surface. If dressed and placed on a moist surface and a dry air flowing over the other surface will cause this to happen.It can happen to seasoned and green timber.
Hope this helps

[Waldo]

Had a sizeable piece of blackwood, 150mm x 2.4m x 40mm, which I needed to resaw into 2, as soon as I did it parted ways like the Red Sea. It's now waiting to get thrown out.

The other boards of the same size after that I ended up thicknessing down to size, instead of two pieces from one, I had to settle with one from one.

Not happy Jan.

[BozInOz]

I'm glad to see that I'm not the only one that has the occasional frustration with wood that would not behave!

I cut some 6mm thick panels for a small project of spotted gum. They warped one way, so I wet them, restacked and clamped, and they warped another way.... after a few attempts... I put them in the porject the best I could. I now have a wavey spotted gum pattern with a wavey spotted gum feel. lol. It sounds worse then it is though. 2 pieces I couldn't use.

[petersemple]

I had it happen once with a very nice figured maple piece for a guitar top. I had it ripped for thickness and so it could be bookmatched. It warped badly before it could be joined and thicknessed, and I just couldn't get it to work. Still have the pieces somewhere waiting for a use. The next one I ripped, thicknessed and jointed in one session, and glued it as soon as I got it home. That way if it warped a bit at least it was together, and a bit of clamping pressure would hold it down onto the guitar if needed - it was fine of course. No warping at all.

Peter

[Sigidi]

Another thing to Boz, after you dressed and stickered it out, did you weight it down?

you started with a 50mm peice and dressed it down to 20mm is that right? if so you took 15mm of dry timber off the top and bottom face which (as exador said) exposed 'green' timber, if you dress this much out of a peice of timber you need to treat it as green timber again - sticker,stack and strap it, then weigh it down for good measure

[BozInOz]

I'm usually quick onto these things. I had them laying on the floor trying to work out which pieces to use. As soon as I saw some warp I restacked them with spacers and some redgum on top to hold it down.

I won't have time to look at them again till next week... should be interesting then.

[Sawdust Maker]

Once had two sawhorses made out of radiata. had them for years used them occasionally.Moved to Sydney still used them occasionally got them out one day and one leg wouldn't sit on the floor, was about 1 inch off. Bloomin top piece had twisted.

Don't know how or why (had been in Sydney about 7 years then). They must have been 15 - 20 years old.

Ended up dismantling both, thicknessing the timber and making blocks for my son

Made new ones when they were building next door

[Isaac Hunt]

It is normal for timber to move when you resaw it.Apart from creating moisture uptake differentials you also release tension /compression within the timber.

The best thing is to rip the timber and strip stack it for a few days before planing and thicknessing.

Quarter sawn timber is less prone to cupping than backsawn when ripped.

[Chipman]

Timber sure can move after sawing. I have seen plenty of seasoned timber do weird things...as I say some "do the splits" as it is ripped and others "cross their legs"! I agree with it having something to do with releasing tension in the wood. Also just the heat of the sawing process will cause cupping and warping when resawing. Just this week, I bought some dead straight pine studs and was ripping them in half for a woodwork class at school.... most came off the saw straight but a couple not only began curving out, but started to twist as well. I have seen this happen with other species too (Silky Oak seems to be quite prone to it and Makore does it as well).

Timber does need to be stacked correctly and used reasonably quickly but sometimes it is if it has a mind of its own.


Cheers,

Chipman

[DougStowe]

I'm usually quick onto these things. I had them laying on the floor trying to work out which pieces to use. As soon as I saw some warp I restacked them with spacers and some redgum on top to hold it down.

I won't have time to look at them again till next week... should be interesting then.

Doc,
Sometimes things will adjust on their own if left stickered for awhile. but I've observed more than once that laying fresh resawn boards on the floor may be part of the problem. A concrete floor seems to be always adjusting to the moisture conditions in a shop, either aspirating moisture or sucking it up. You can observe the same conditions more dramatically if you leave a board on the ground outside. Within hours or sometimes minutes, the cupping can begin. Just laying your resawn materials someplace other than the floor can make some difference in results.

Students usually ask me during demonstrations whether it would be better to sticker wood and let it acclimate before final dimensioning and cutting into parts for a box and of course the answer is yes. But the funny thing is that when teaching, I never have time for that and the boxes still turn out successfully. So I suspect that there is some possibility that going as straight as possible from re-sawing and planing into a glued up box offers some advantages, or at least advantages over wood left on the floor where air circulation is only one side.


Doug

[JDarvall]

my experience tells me when your planning on resawing stock....maybe just resaw one stick first say 10mm oversize (depending on length etc) and see what it does. Make the decision on resaw width based on that, so that you've always got enough meat to get your final dimention after thicknessing.

As you'd know, you don't always need timber to be perfectly flat. If its flexible enough in certain applications it can bow like a banana even and it'll be fine. don't want to waste wood if you don't have to try to get it flat.

at work we're using kwila at the moment. Its been kiln dried, and the boss asked me to rip up draw fronts just for these day beds we're making. I have to rip 45mm sticks in half ...leaving about 21mm after bandsaw kerf....just enough to flip each piece twice through the thicknesser to 20mm. Can't go any less than 20. Unfortunately the resaw through the bandsaw causes a bow immediately, and I end up with slightly bowed dressed timber. But, even though undesireable, its passable because there's plenty of flex to them . these faces will pull in fine with screws. .....ie. if it wasn't passable I'd loose tons in waste just trying to get flat timber. just an example.

[Sigidi]

Guy's , one thing you have to realise with a piece of timber ( and any of the sawyers will agree) the sawyer mills each log in a way dependent upon how it is re-acting while milling, each piece is cut out so that it is as stable as the sawyer can get it from that log and that place in the log -we try to even out the circular forces in the log to give us a straight true stick...

If someone goes ripping it into small bits, you now have forces which did hold it straight together, but apart work on their own - yielding the gamut of changes described.

Imagine a 12" board if you want to 6" boards and you try ripping it in half, more often than not, the two boards will move away from a straight line. I always advise folks to rip equal amounts from each side thus taking an equal amount of stress from each side of the board, thus hopefully leaving a straight true stick