Boards bending after planing

[Quickben]

How long do you leave your boards after planing before you start thicknessing them ?

I can plane a board down to a decent flatness (checked with straight edge three ways) but then I come to thickness and they’ve curved longitudinally. My initial thought is that I’m planing too fast, as in I’m making each pass at too high a frequency and heat is building up in the timber. Or is it that I need to leave them for a few hours to straighten out before I start thicknessing.

Or am I just unlucky in that I’ve got loads of boards with mega internal tension ?

 

[MikeG.]

'tis a bugger, wood. It sets out to trick and deceive you.

My best advice is to try to remove equal amounts from each side. It is nothing to do with the heat from planing, and everything to do with both internal stresses and moisture levels. These two factors operate at differing speeds, and there really is no blanket answer to the question you ask about "how long". If I'm working on something special where flatness and straightness are important, I will try to clean the boards up well in advance of finishing them, and set them aside for a week or two, in the house if possible. Then final dimensioning (again, trying to take roughly the same amount from each side) at the last minute just before building it into place. It often doesn't work out that way, just because of circumstances, but if you are working with something tricky then this is the sort of thing you might consider.

 

[Orraloon]

Its a general rule to treat both sides of a board the same so plane one side then thickness strait away. If you expose new wood to drying out on one side then that side shrinks and the board bends or cups. Same treatment both sides tends to balance things. The less well seasoned the wood the worse the effect. Flat sawn is worse than quarter sawn. Cheap wood like pallet wood and some construction wood is just sawn any old way where furniture quality wood is selected for quality and grain direction and sawn for best effect. Some of the crappier timber can just never be made to behave whatever you do.
Regards
John

 

[CHJ]

Gets even more frustrating if that 'nice' bit of wood has come from a prime 'Reaction Source' This explanation and associated thread may be of interest.

 

[Hornbeam]

My approach is similar to Mikes. I flatten the concave sides on the planer and then put the boards through the thicknesser until n consistent thickness. I then write A or B on each side and take alternate passes through the thicknesser taking about 1mm per side. For drawer sides and critical stock i will only take it part way and then put it into stick for a few days often in the house before further thicknessing. In general I have found that straighter grain boards cause less issues than wilder grain but you can always be surprised.
Some people restrain the material in stick with clamps. It also depends on what you are making and how everything will be restrained in the final construction

 

[AJB Temple]

I agree with the others. My main approach (apart from what they said) is to do a moisture reading on the wood, and keep it in a drying environment for as long as I realistically can. For example, I bought a great deal (for me - about three dozen long wide and thick) boards of maple and wenge last year to do a kitchen and utility room. It has been in the building where it will end up, all sticked and carefully stacked, for about 6 or 7 months. It will be summer by the time I start using it. I monitor and control the heat and humidity in the room. I very rarely get good quality wood moving about much, and I think this is largely due to planning well ahead.

 

[RWood]

I usually dimension roughly, taking equal cuts from each side, then come back to it the next day and do final dimensioning then straight into joinery - Generally works, but some boards just won't play (and it's my fault for buying them in the first place!!)- they joy of woodworking

 

[woodbloke66]

What Mike G and others have said. I generally take a little off from both sides and then let it do it's own thing for a week or two. Currently I've got some bits of Brown Oak conditioning in the workshop and one or two of the 180mm wide boards have warped by around a mm or so. As long as there's plenty of 'meat' left in the boards, it doesn't matter as once they've become stable they can be hand planed/machined to final thickness - Rob

 

[thetyreman]

after bandsawing some wood recently I let it settle for a good 3-5 days before planing it, the final dimension was 1/4" thick you have to take it down to size slowly and even then it can still move, the thinner you go the trickier it can be.