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Bowed wood - How to straighten

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Forum topic by garberfc posted 03-28-2013 12:27 PM 4881 views 0 times favorited 10 replies Add to Favorites Watch
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garberfc

57 posts in 913 days


03-28-2013 12:27 PM

I have a couple of boards that are bowed and I’m wondering if they need straightening / how to do it, or, are they okay.

I’m building a faceframe out cherry. The stiles and rails are two inches wide and are going to be joined using mortise and tenons. The faceframe is going to be attached to the carcass using biscuits and Titebound III glue.

As seem in the photos I’ve been attempting to straighten these boards by bending them in the direction opposite their bow. They’ve been clamped for about a week and at least half the bow is gone. I’d say the bow in the middle is about 3/32. The rail is ~21 inches. I’m wondering if all the bow will eventually be removed and if it’ll return to it’s original shape over time.

Another question: Do you think that M&T joints, biscuits and glue are strong enough to hold a piece of bowed wood flat over time?

Please advise…

Thanks in advance for your help,
F


10 replies so far

View knothead's profile

knothead

149 posts in 2607 days


#1 posted 03-28-2013 12:48 PM

Wood does what wood does no matter what we try to make it do…..If they are already milled to final width and thickness you are not going to be able to fully correct this, you gotta either live with it or work the bow into your project somehow or remake them from better material.

IF, ON THE OTHER hand they are still oversized and long, Charles Neil has a trick that he uses that appears to help a great deal, He would rip a centered slot in the inside edge of the stiles and rails that is nearly all the way thru the width of the piece and then mill a piece that fills the entire slot you just milled out of the same material and glue it in. Clamp it up tight and straight, say against your bench or assembly table, anything that is flat and wait overnight for the glue to completely dry and then re-mill your pieces. Actually I would let them reacclimate to the shop again for a few days as you have just added a lot of moisture from the glue to the pieces The 2 additional glue joints really arrest any future bow or twist.

I suspect there are folks here with much more experience than I, and if there are better solutions I bet they will post them for you to consider. But this is what I would do if it were in my shop.

Just 2 cents worth of opinion no more – Have a good’n

-- So Much Wood - So Little Time! --

View redSLED's profile

redSLED

687 posts in 551 days


#2 posted 03-29-2013 12:55 AM

I am watching this with interest since I would love to “correct” some maple 1×4 and 1×6 pieces in my shop if possible.

Also, in the photo I think that’s too much pressure for those types of clamps. Might be better for some annoying-to-use big-arse C-clamps to take on that job – and extend the life span of the quick-grip clamps.

-- Perfection is the difference between too much and not enough.

View garberfc's profile

garberfc

57 posts in 913 days


#3 posted 03-29-2013 12:04 PM

A friend of mine mentioned adding some humidity as that’s how a lot of wood is bent. I don’t have the equipment for that. This is all in my basement shop where the humidity is pretty low (~40%) this time of year.

View Miles King's profile

Miles King

28 posts in 1350 days


#4 posted 03-29-2013 12:48 PM

That minor bowing of the wood doesn’t look too bad to me. As “knothead” said wood does what wood does. As an example look at some cabinet doors that were “flat” when originally made and after a few years some will exhibit some bowing but for the most part they still function and on some rare occasion some will need a little repair. It’s wood.

-- Miles

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garberfc

57 posts in 913 days


#5 posted 03-29-2013 01:27 PM

I think I’m just being stubborn (as usual). There’s nothing special about the pieces in question (other than their lengths exactly match their corresponding rails). It must just be another personality flaw…

View Rick M.'s profile

Rick M.

3978 posts in 1038 days


#6 posted 04-01-2013 05:35 PM

If it really bothers you, rip them down the center, flip one and reglue. As for bending, humidity will cause wood to warp or bend because it is absorbed unevenly so if one side is ‘wetter’ it will bow up. Wood bending is done through heat, the steam just acts as a carrier but does not help bending.

-- |Statistics show that 100% of people bitten by a snake were close to it.|

View Net55's profile

Net55

78 posts in 246 days


#7 posted 02-26-2014 04:05 PM

I’m removing the bow from a beautiful piece of milk chocolate colored walnut. This piece had about a 1/2” crown to it. Place a damp rag underneath it to add moisture to the wood. Raise the 2 ends, clamp down (both sides, just one side is shown in my image) in increments, in my case about an 1/8” per day. Use a household drape steamer or iron. You’ll need to over-correct, each piece will be different. This does not always work perfect. Let the wood sit flat for a few weeks, if it goes back a bit, repeat.

-- Bill, SW Florida

View runswithscissors's profile

runswithscissors

957 posts in 683 days


#8 posted 02-26-2014 08:27 PM

A crude, simple but effective old trick is to lay the board cupped side down on the ground. Moisture in the earth will expand the concave side and straighten out the board. Of course, that doesn’t address what’s going to happen to it when it dries out again.

If you have sufficient thickness, jointing and planing would be a surer way to go.

View Grandpa's profile

Grandpa

3136 posts in 1334 days


#9 posted 02-27-2014 04:25 AM

straighten the board by moistening the cupped side. Clamp it as shown in the lead photo above so it is straight. Wrap it in black plastic and heat it by placing it in the sun on a hot Oklahoma afternoon. Let the board cool and take it out of the plastic and unclamp. It will often stay pretty true. Try it on a scrap and see what happens.

View fernandoindia's profile

fernandoindia

1073 posts in 1602 days


#10 posted 05-16-2014 08:01 PM

Hi Garber,

How did the straightening go. I´m having the same problem. so far after several attempts mine are still bowed

Thank you

-- Back home. Fernando

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