any tips for removing bow from pine?

[thetyreman]

I am making my toolchest, there is one piece of pine that has decided to bow on me, it's enough of a bow to cause a problem, do you have any tips on removing bow, or should I just get another piece of wood and think again? if possible I'd like to try and remove some of it,

regards,

Ben.

 

[John15]

Any planing to reduce the bow will obviously reduce the thickness. If that's not a goer then best to buy a new piece. Not sure if you can support the ends and weight the middle to ease the bow out over a few weeks. I've got a nice 6' board of cherry and that's bowed on me. I store my timber upright with just a slight slope so maybe that's what's done it - very annoying.

John

 

[ED65]

Is the board at finished dimensions?

Assuming you can't take any material off you can remove some, most or all of a warp by clamping to flat, or slightly over-corrected to bent in the opposite direction, and then leaving it for a while (days at minimum). Some careful damping of the wood can be beneficial too.

 

[thetyreman]

Is the board at finished dimensions?

Assuming you can't take any material off you can remove some, most or all of a warp by clamping to flat, or slightly over-corrected to bent in the opposite direction, and then leaving it for a while (days at minimum). Some careful damping of the wood can be beneficial too.

the piece is 19mm thick, final thickness will be 14mm so theres room for some movement, the problem though is it still might end up slightly undersized.

having checked it again today, the bow is still there but not quite as severe so it's moved again since last night, the bow was around 4-5mm, now it's probably closer to 2-3mm higher in the centre, didn't do anything to it, moved on its own.

 

[ED65]

...the bow was around 4-5mm, now it's probably closer to 2-3mm higher in the centre, didn't do anything to it, moved on its own.

Wasn't flipped over by any chance was it?

If you want to try to get the rest out nothing to lose trying clamping and a bow is the easiest warp to fix, it generally only needs one clamp placed centrally and two support blocks near the ends. I've successfully taken bowing out this way a few times but had it not work as well other times, although there is always some improvement.

If you do manage to get it flat enough that you're comfortable using it it's common advice to wrap it in plastic or put it in stick with weight on top to keep it stable until it's needed. Then dimension and use it in one session if poss, if not get it to dimension and again store it under weight until assembly.

 

[Orraloon]

I would not risk the whole project for a bent stick. You may get the bend out following the advice so far but will it stay flat. Get another board for the chest. Then play around with that one getting it flat to be used in something less important.
Regards
John

 

[Woody2Shoes]

Once in a while I get a piece of pine which goes quite banarama along its length.

Usually, there's an asymmetry in the growth rings that suggests it's got "reaction wood" in it i.e. it grew at an angle off the vertical.

This sort of thing: http://forestryforum.com/gallery/albums ... mpwdop.jpg

I have learned to avoid timber with asymmetrical, i.e. non-concentric, growth rings as there's nothing to be done with it.

A certain amount of cupping across the width of a board is mostly survivable, as already mentioned, if you've got a few mm of spare thickness to sacrifice and your design constrains (and/or allows for) future movement.

Cheers, W2S

 

[deema]

If it’s bowed since you bought it rather than cupped it’s highly probable that in the recent heat you have uneven drying out. Before planing etc, dampen the inside of the curve, put it in stick so air can get around it and leave it a couple of days. Damp the inside curve each day until straight. Once straight leave a further two days to stabilise or longer if possible.

 

[thetyreman]

I've tried what you said deema and there are some improvements already, I am clamping it down to my bench overnight just to see if it can be improved any further before it's ready for glue up as part of a panel. The weather has been ideal here, unbelievably dry and hot, and I had it out in the sun.

 

[memzey]

As it’s not some expensive hardwood we’re talking about, I’d just get another length of pine if it were me. The time and effort that goes into projects is much more valuable than what a stick of redwood would set you back.

 

[custard]

Wood will go where it wants to go. If it's secured all around, and thin enough to be tamed, then okay. Otherwise if a board is determined to act up then it gets fed through the woodburner.

A board that's crook or cupped can sometimes be reduced in size to find a use somewhere, but if a board is seriously in wind then it'll likely always be trouble.

 

[thetyreman]

As it’s not some expensive hardwood we’re talking about, I’d just get another length of pine if it were me. The time and effort that goes into projects is much more valuable than what a stick of redwood would set you back.

depending on how it looks tomorrow, that's what I am going to do, I will see how it looks, valuable lesson learnt, buy more wood than you need.

 

[profchris]

If it's really dry conditions now I'd want to see how it reacts to higher humidity. Maybe put it in the bathroom and check it an hour or so after a shower or bath.

It might be that you released stresses by cutting it and it's finding its new stable shape. Stable is fine.

But if it keeps moving you need to decide if your finished piece is up to controlling that movement. If not, don't use it!

 

[Jacob]

Might it be OK in situ if you just put the box together? It's often the case that things get pulled together when the item is actually built.

 

[memzey]

My concern would be whether the temporary measures you have taken to straighten it out now will keep it straight in future. I would have thought that you don’t want to be faced with a misbehaving board in the finished item if your chest demands that piece be true.

I should say however that personally I haven’t completed enough projects to build up a body of experience adequate for me to judge a bowed board as being redeemable or not, hence my reluctance to rely on a delinquent bit of pine when I might be able to get a spot on length for relatively little outlay. In fact the last time I experienced something similar I posted about it on here and got some great advice from Custard on how to deal with it. That was, however, in the context of 3/4” oak being glued up into a table top and held down and true in the final piece with buttons (so not too similar to what you are attempting in all honesty).

I’ve also just had a similar galling experience where I’ve had to think again as regards some pieces of oak I’m using for a box for my daughter (thread in the projects section). There I needed to set aside a couple of lengths of oak after thicknessing and start again. What I have learnt however is that wood will do whatever it wants to do and it always pays to make sure you have extra stock to work from. Good luck!

 

[custard]

From a purely practical point of view there's a problem that regular occurs with thinner (say anything under about 18mm) cupped boards. If you run them across the machine planer and the knives are at all blunt then the workpiece starts to "flutter" as the blunt knives try to lift the workpiece up over the cutter block rather than cut it.

So you press down harder to bring things back under control, which then just flattens the board and so removes the cup. End result is that instead of removing the high spots of the cup you just get a uniform cut right across the full width of the board, and you're left with exactly the same degree of cupping but now it's on a thinner board!

The best solution of course is to sharpen the knives, but the second best solution is to just do the job with a bench plane, where you can direct the cut exactly where it needs to go. Not a problem with a crook or bowed board, but a common hurdle with twisted or cupped boards.

 

[fiveeyes]

What i have done in the past...if the board is wide enough, remove the bow best you can, then rip on center. Swap one side ..end 4 end.. edge glue it back together, and use it. YMMV