Problems - Fresh sawn wood

[Offcut]

I am about to make up some cabinet doors and bought some rough saw oak to resize, I cut the plank to 640mm long and ran it through the planner thicknesser to square it. I then ripped it down the middle producing to pieces of 70 wide x 50thk x 640 long, I then ripped them down the middle to produce four pieces 70mm and 23thk x 640 long.(still with me) Then disaster!!! The wood, which was lovely and square, now resembles 4 bananas. Is there any way of stopping this happening when I cut the next door, maybe leaving it at the 70 x 50 x 640 in the house for a week to stabilise. Just a guess though? I will now have to run the wood through the planner to remove the banana but it will reduce the thickness down quite a bit. I have never seen such bad bowing before.

Andy

 

[Anonymous]

Hi Offcut

Bad news indeed

I too had this happen a while back.

I think you can only saw it over size and then leave to 'settle' for a while as the stresses work themselves out before cutting down to final size and then P/T

Cheers

Tony

 

[Alf]

Andy,

Ouch. My commiserations. The longer you can leave it to stabilize between machining operations, the better (within reason of course). It helps to do things such as taking off equal amounts from both sides when you run it through the planer thicknesser, leaving pieces oversize during the machining as long as possible, getting the work assembled and glued up before it has time to move - although the latter isn't always practical, or even a good idea in some cases. As you've got so much movement, d'you know what the moisture content of the wood is? Could be it needs a little time in stick, depending on how reliable the supplier is. Also, if you've got a range of boards to choose from, try and select the straightest grained ones, as close to quarter sawn as possible for preference. Every little helps.

Sorry if all that's egg sucking instruction.

Cheers, Alf

 

[Offcut]

The timber is very low moisture content. Because the banana happened as it came off the saw I'm thinking it must have been stressed within the wood. I'm going to try cutting the larger sections and resize after a week sitting on the under floor heating and if the doesn't work I'll just have to make thinner cabinet doors!!

Can you give me an idea of the quarter sawn theory. When buying timber I usually look for the straightest piece of wood that will give me the most usable wood. I only worry about grain when gluing up wood for say table tops etc..

Thanks for the reply's

Andy

 

[Midnight]

Fit Like Offcut..

In this neck of the woods, movement like that isn't so uncommon I'm afraid... Personally, I leave new stock at least 2-3 weeks before touching it at all, preferably a lot longer, just to give it time to acclimatize to conditions in the shop. Rather than re-planing the bow out of the sticks, you could try re-stickering the boards as Alf said, bow side up, and add a little weight to them to encourage the sticks to straighten in the direction you want. If at all possible, I'd leave em like that for a couple of weeks.

 

[Chris Knight]

Andy,

If you are sure the wood is very dry (and I would ask how you know this, since you don't mention a moisture meter) then the bending is due mostly to stresses being released. This happens within a few hours of the machining operation and as people have said , the answer is to machine oversize, wait and then machine again ( I usually wait a day for stress relief but a lot longer if I am waiting for the wood to achieve equilibrium with the humidity in my shop).

Occsaionally distortion produced by stress relief can ease a little but there is not much to be done about it I am afraid.

Stresses can occur in wood due to the way it has grown - so-called "reaction wood" develops where the tree itself is opposing the stress of gravity for example in boughs or in the trunks on slopes. Stresses can also be induced by bad kilning. Selling wood with excessive amounts of either type is bad practice but as good wood gets harder to source, yards progressively reduce their stadards I am afraid.

Quarter sawn wood is less prone to movement due to humidity changes (and hence moisture content within the wood since wood shrinks/expands far less radially compared with tangentially. QS looks good in oak but is rather a dull looking cut in most other species.

 

[Offcut]

Nae bad mike,
Are you from anywhere in Scotland I might know?

I have the timber under weights at the moment, hopefully it will reduce the bowing and reduce the amount of planning required. I would normally leave the wood to stand for as long as practically possible but as the cabinets are made and her indoors wants them in as soon as possible, I thought I'd just go for it.

Andy

 

[ike]

Hi Offcut,

I had exactly the same problem as you describe with Oak. I acquires several slabs of it 16" W x 3- 1/2" T x 14 feet long (QS) ex bankruptcy stock.

It was dry as could be - years stored undercover yet it bowed terribly when I ripped it for 3/4"x 3-1/2" stock. I gave up in the end and use it only for thin stuff e.g. mouldings/picture framing.

I agreee with the internal stress theory. It either was stacked poorly when air drying and or kiln drying, or it was from a stressed trunk. No solution, it's just bad timber - so only good for v.thick or v.thin sections.

 

[mudman]

There was a technique espoused in a thread a while back: https://www.ukworkshop.co.uk/forums/viewtopic.php?t=1414&highlight=bow+lawn

Never know, may work.

Cheers,
Barry

 

[Midnight]

Andy...

I'm probably 20 minutes from you.. currently working on the exact same prob but on a bigger scale; 8"x1.5"x60" with a 3/8" bow along it's length...
Alf's remedy works...
Physio-therapy I calls it.. honest gov..
:wink:

 

[johnelliott]

Unless there is a very good reason not to, one should always buy wood already sawn to the thickness one needs for the work in hand. For 3/4" door thickness, then one should buy 1" wood. All wood will have internal tensions, especially after it has been kiln dried, and this is the only way to avoid trouble
John

 

[Midnight]

there's a slightly more detailed explanation of what's going on here :-

http://forums.taunton.com/tp-knots/messages?msg=17949.1

 

[Mike.C]

Hi Offcut,

I try and buy my through and through a few months before i need it. I stick it and keep it in the workshop for a while. I then cut it over size and i make sure that i plane and thickness it a equally number of times on both sides. After this i try and leave it in the room where i am going to use it for about 2 weeks.

Obviously the above is not always possible, but even if it is a rush job i find that if i at least plane and thickness it an equally number of times it usually turns out alright.

Like Mike i am up near you too about 40 minutes away.

Regards

Mike.C

 

[Offcut]

Hello all,
Well firstly the wood is kiln dried and has been sitting in the timber warehouse for the best part of a year, it's as dry as it will ever be. So I have to put it down to internal stressing. Leaving the pieces over night under weights has resolved about half the bow. I planned the pieces from 23 down to 16mm removing equal amounts from both sides(thanks mike.c) and hey presto flat square wood. I then took some more stock and created the back panel also having to cut the pieces much larger and plane down (removing 1/2 the thickness!!) routered, glued and bingo first door created.

John, I usually buy rough sawn because it is much cheeper.

I have some photo's but no way of putting them up on the forum!!!

For the people who live in this neck of the wood - where is best to buy timber?

Thanks all

Andy

 

[Alf]

I planned the pieces from 23 down to 16mm removing equal amounts from both sides(thanks mike.c)

Funny. Could have sworn someone else mentioned that too... :roll:

Cheers, Alf

Obviously typing in the wrong accent, d'ya ken. :wink:

 

[Offcut]

Sorry Alf,
All credit to you - you did suggest it first..

Andy

 

[Midnight]

For the people who live in this neck of the wood - where is best to buy timber?

Andy....

I buy all my hardwood through here:-
http://www.scottish-hardwoods.com/

It's a bit out of the way, but I kill a couple of birds with one stone; my sis stays about a mile from the mill. Good stock for the most part if a touch on the expencive side. Worth calling in advance though; last time I was there his stock of oak was near wiped out.

Glad to hear the sticks straightened a bit, though I'd keep an eye on em for a while yet...

 

[Alf]

No worries, Andy. Usually I never give it a thought; dunno why I bothered this morning. Fancied a tiny moan maybe?

Cheers, Alf

 

[johnelliott]

John, I usually buy rough sawn because it is much cheeper.

Sorry, when you said cabinet doors I thought you meant that you needed stock about 20mm thick planed and thicknessed, which can normally be achieved starting with 25mm sawn, rather than the 50mm mentioned in your first post
John

 

[Mike.C]

Hi Mike,

Isn't it a small world? Exactly where i get mine. I only live about 10 minutes from it. Paul Conroy is the owner.

Your right about giving him a ring before you go as he does travel about a bit to get more stock.

Regards

Mike.C