How do you straighten/bend wood planks without removing any material?

17

1

I have some 6' long 2"x12" planks of douglas fir that dried into a twist, I need to straighten it out but I don't want to plane this any thinner. So basically I'm trying to bend the board back into shape.

I was thinking of doing something like physically twisting the board the other way past its yield point, and hoping the board does not snap. Maybe I could try steam bending to straighten wood.

I am planning on making 6' long benches and shelves with this material, for indoor use.

Netduke

Posted 2015-05-19T15:15:56.800

Reputation: 623

1Stupid thought for the day: Theoretically, it might almost be possible to resaw the high spots off one side and laminate them onto the other, if you could manage to cut that line despite the warp... – keshlam – 2016-09-15T02:15:45.423

Obligatory watch: https://youtu.be/VaNW4ZcXrMY?t=21

– Damon – 2016-10-30T10:23:17.497

1Are your final cuts going to be 6' long? – Steven – 2015-05-19T17:04:22.787

Yeah the final result is 6' long. The original plan for this was to make some simple benches. – Netduke – 2015-05-20T14:27:58.243

I doubt that steam bending is going to actually work, but you have a much higher likelihood of failure with this if the wood was kiln dried to begin with. (If I remember my theory from carpenter school, it's that the lignins have been set by the KD process and are much less likely to set differently.) – Aloysius Defenestrate – 2015-05-22T02:23:09.357

A year late, but I've been trying to figure out a similar thing. What if you soak the boards overnight (like on your lawn with a sprinkler) then stack them and park your car on them length wise for a few days? – None – 2016-05-28T17:36:30.460

Answers

14

Steam bending would be your only option. Wetting the fibers and allowing them to bend and twist. It might not work, but there is a chance. Not using a moister measure, you will just split the wood where the stresses get to great.

On top of that, you will have to redry the wood back to where you need it and you will need to keep a lot of weight on it so it will dry flat. Otherwise it will just rebend and twist.

Birch likes to bend and twist when it dries, but if you keep it flat with weight (like more drying wood on top) it will dry flat and stay that way (mostly).

Ultimately it will be a bit of work and it might be easier to just acquire new lumber for your project.

bowlturner

Posted 2015-05-19T15:15:56.800

Reputation: 12 431

Would it be good to stress the wood passed the wanted shape so as to loosen [whatever it the wood's internal chemicals are called] before set to final shape? I'd like to remember I have read about this in FineWoodworking magazine; it was like, after steaming, bend it a lot, twist it and finally the wood loses it "initial" shape. – LosManos – 2015-05-20T08:02:24.603

3@LosManos, yes bending past the shape you want can be advisable because there is usually 'springback'. But the way the wood will be used determines whether this is necessary or even desirable. With the original question, bending twisted boards back to flat, I'm not sure it is really feasible to bend a little further than flat unless a very complex and involved bending jig were constructed (different for every board). – Graphus – 2015-05-20T09:21:15.503

11

The other answers have covered how you can bend the wood, but one thing they left out relates to the length of the wood. The following applies to some other defects too like bows.

You mentioned you have 6ft boards, but you don't say what your final board length will be. If the length will be shorter than 6ft, then it would be advisable to cut them to approximate length before attempting to correct the defect. The twist might be noticeable over 6ft, but it won't be as severe over 2ft, you might even get a 2ft section with no noticeable twist.

Once you have a shorter board, you will have an easier time correcting it. In the case where you are removing material, you will end up removing a lot less wood than if you did the entire board at once. This applies to running wood through a jointer as well.

Steven

Posted 2015-05-19T15:15:56.800

Reputation: 3 663

Hmm. I would have thought it would be less trouble to set up a jig to twist back one 6' board, and then cut it down to two 3' lengths, rather than do two 3' boards. (OTOH, I agree that the amount of the error will be less for the shorter board.) – Martin Bonner – 2016-09-16T11:45:05.683

He mentioned that he would like to build 6' benches for indoor use. – CharlieHorse – 2015-05-22T16:12:15.887

@CharlieHorse that just got edited in after I had answered already.... So unfortunately this won't apply to him, but I still think it's good general advice! – Steven – 2015-05-22T17:35:12.027

You are absolutely correct. – CharlieHorse – 2015-05-22T18:04:38.260

6

Bending using heat (usually steam) is one of the only ways to bend wood reliably. But, when a board twists as it dries that is usually not permanently fixable because the wood may have 'taken a set'. So while you could steam, bend back to perfectly flat and hold it there until it has cooled, and it may stay that way initially, it is likely to have a natural tendency towards warping back to the twisted shape again in time.

Because of this, generally, when a piece of wood does twist or bow when drying the usual way to get flat wood from it is to remove material until a flat board is revealed from within the bowed board. Obviously there can be a significant loss of thickness when doing this (and some loss in width) and sometimes it is so great that the board can't be used as originally intended.

Graphus

Posted 2015-05-19T15:15:56.800

Reputation: 38 608

5

I have tried to straighten a wood screen door with steam with very little improvement. I then forceably bent it well past straight, 1 1/2 inches in center of the 7 foot span. Then saturated it with linseed oil and carefully heated the board with a propane torch. It is holding it's shape after a week.

Leo Becker

Posted 2015-05-19T15:15:56.800

Reputation: 51

1I very much like answers of the sort "This is what worked for me." I would be interested to hear how the repair is doing a year from now. I don't doubt that it will hold, but would like to know. I suspect the success was almost entirely from the heat source and that the linseed oil was not necessary. – Ast Pace – 2016-09-14T17:16:34.160

1

Little late but...I tought about how you straighten a door, using wood block on the 'to in' corner and close the door for a 36h, door is most time corrected. So, I put wood blocks under the two lowest corners, whem board lying flat on floor, then put heavy weight on middle on a high humidity day. Seems to work for now, will follow up.

robert g

Posted 2015-05-19T15:15:56.800

Reputation: 11

0

I have used this method to make a badly twisted board useable.

  1. Rip the board into about three or four narrow pieces. Each piece will carry only a small part of the twist.

  2. Joint and plane each piece

  3. Joint the rip cuts so they come square to their new faces.

  4. Glue up, keeping the pieces in their original order. With luck, the grain will match nicely.

Philip Roe

Posted 2015-05-19T15:15:56.800

Reputation: 101

Yes this is one approach but the OP as on how to do it without removing any material? – Matt – 2017-09-12T00:46:15.373

This is an approach that removes as little material as possible. Trying not to remove any material at all is setting yourself up to fail. The OP starts with 2". This way he might not lose more than 1/8". But if the boards are bowed as well, I dont think any method could be relied on. – Philip Roe – 2017-09-12T13:41:07.957