# Flattening a large bowed piece of wood w/o losing thickness



## DTrak (May 25, 2015)

I am making a 100" table top and now have all my boards more or less flush on the sides (in case you saw my question yesterday about that). One of them is cupped and therefore rocks when it is laid on the floor with the others. It is 8"x100". Even if I had a joiner that could handle that, I cant remove any thickness because all the boards are currently the same thickness so this board would not line up. Is there some other method? Can it be bent somehow? If I put some heavy weights on the ends and then screwed it into the other boards, would it hold?

thanks


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## JayT (May 6, 2012)

First off, is it cupped or bowed? Talking about weights on the ends makes me think you are actually referring to bow. Cup is warp across the face, while bow is warped down the length of the board.










If you are really talking about cup, then the only success I've ever had with "fixing" a cupped board was to take a spray bottle and mist the concave face of the board, then lay it out with the convex side up for a while in a place where it'll dry-like out in the sun or a heated shop. The cupping is a result of moisture leaving the board unevenly. Doing this process helps to equalize the moisture.

No guarantees it'll work. I've had it work perfectly (then stored the board in its edge to prevent it from happening again) but more often the board tries to cup again because the grain structure in flat sawn boards allows moisture to leave from one face faster than the other.


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## DTrak (May 25, 2015)

Sorry, you are right, it's bowed. 
That's an interesting process. This wood is 2" thick, so I am not sure it would work, but I can try it.


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## JayT (May 6, 2012)

Doesn't usually work for bowed. Nothing hurt by trying, but a lot of bow is the result of tension in the grain of the wood. How have you been storing the wood? If you've had it laying flat, try standing it on edge with at least an inch of air on both sides for several days and see if allowing the moisture to equalize gets it closer to straight on its own.

Sounds like the wood was not properly dried before you got it. A dry 8/4 board shouldn't move much.


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## DTrak (May 25, 2015)

I just updated the title of this post to say "bowed" instead of "cupped"


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## johnstoneb (Jun 14, 2012)

Your best bet is probably using dowels or biscuits and cauls in the glue up to get it straightened. This will work if the bow is not to bad. Your other option is probably replace that board.


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## fuigb (Apr 21, 2010)

Doubt that anything short of flattening/jointing the board and its peers will deliver professional results. Sorry for the buzz-kill.

Is the heart of your question an unwillingness (inability? ) to flatten and then remill all of the boards in the top? Just asking because while I sympathize with the desire for an easy solution I'm also curious as to why flattening isn't the solution that you settled on, however reluctantly it may have come.


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## DTrak (May 25, 2015)

If I hold it down flat with weights and then screw it into the adjoining piece with lots of pocket screws, would that hold it flat?


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## fuigb (Apr 21, 2010)

Ugh, OP updated from cupped to bowed while was hunting and pecking. A bow is more manageable than a cup for a hail Mary play, but I still expect the result to be frustration with the end product.


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## JayT (May 6, 2012)

> If I hold it down flat with weights and then screw it into the adjoining piece with lots of pocket screws, would that hold it flat?
> 
> - DTrak


Maybe. As the others mentioned, since bow can be dealt with easier, it could work, depending on how bad the bow is. It could also screw up the entire project. Depends on how much tension is in the bowed board and how much more it wants to move. You might also consider a cleat across the bottom, with the center screwed down tight and screws in the outer sections in elongated holes to allow for seasonal movement.

Doesn't really matter how many screws, glue, etc you use, wood will move. That is why we try to start with dry, stable stock to begin with. That wood has already shown how it wants to move.


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## bondogaposis (Dec 18, 2011)

Your best bet is to get another board.


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## DTrak (May 25, 2015)

The reason I can't flatten and remill all the boards is I don't have access to a joiner. And dont want to buy one just for this purpose. But even if I could, these boards are 8" wide and any joiner under $1k is 6" wide.

I can't replace this board because it is a live edge that matches the other live edge on the other side of the table. top.


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## Snipes (Apr 3, 2012)

You could put some saw kerfs on the bottom side, maybe 3 then fill in with matching wood. this would work best if it bowes up.


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## dhazelton (Feb 11, 2012)

If it's a very minimal bow, I'd do the glue up keeping the ends of the bowed board flush with the ends of the adjacent boards, and have the bow facing up. Then use a hand plane or belt sander to flatten that board flush with the surrounding area. If it's two inches thick you can remove quite a bit before you have to be concerned about anything.


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## Pezking7p (Nov 17, 2013)

I would recommend a hand plane. Get a #5 or a #7 - #5 will be cheaper, but not as easy to get your board flat as with a #7. For this scale of project and because it's a table top, I would go with a #5 because perfectly flat is not super important, it just needs to look flat and contact your underlying table support in all locations.

Now, I recognize that suggesting you go get a hand plane opens up a whole other can of worms - sharpening, flattening boards by hand, using a hand plane in general. But to be honest, there is plenty to learn with a power jointer as well, maybe more so because a jointer's operation is not always intuitive (I almost quit woodworking trying to get mine to work correctly).

Anyway whatever you decide, check back because we're here to help.


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## ThomasChippendale (Nov 6, 2015)

It all depends on how much effort (force) is required to bring it in line while it is being glued to the adjacent boards. It is normal in a glue up to have boards bowed slightly and to tap them in place while in the clamps at low pressure to even them so when planing the entire surface, you loose less thickness.

It is easy to figure, place the board bowed side up and press it down, if you can flaten it with your hand just pushing down, its fine, it will not distort the entire table top.

If you require standing on it to bring it down flat, then, if you absolutely want to use this board and the underside and edges are hiden, you could cut a serie of kerfs, evenly spaced along its length, say ay every 6 inches and 3/4 of the thickness and make it more flexible, once glued-up it will not weaken the table top and the entire assembly will be more stable.


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## Gixxerjoe04 (Jan 31, 2014)

Got any pics?


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## DTrak (May 25, 2015)

Thank you all! I dont think I want to plane it because all the boards need to stay the same thickness. Dont feel like getting into the steaming idea although it's great to know and will come in handy. 
The bow isnt that bad, so I think I will try glue and lots of pocket screws. I have gotten very comfortable with a kreg jig. 
thanks again
Dan


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## Tennessee (Jul 8, 2011)

+1 for dhazelton's idea. The "thinner" part will be on the bottom, and will be in the middle, thus not open to inspection.

I think trying to bring it back with pocket screws & glue and holding it firm will not work over time. It will win out and bend another plank, and you will end up with a warp in the tabletop.


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## Woodbum (Jan 3, 2010)

With your parameter of all of the boards needing to be the same thickness, you are pretty much SOL. Even with a jointer and planer rework, you will lose some thickness. Steaming is a decent idea, but extremely hard to do with a 100" piece. Not wanting to replace the board, plane it down etc, you are pretty much out of options short of forcing it in plane with dowels etc. kerfing the bottom and/or putting cleats across the bottom at 12-18 inch intervals, but that is a short term fix only. The bad board will win out in the long run. I wish I had a magic bullet for you, but I threw mine out with my old board stretcher and a box of old chrome muffler bearings. :-( Sometimes you just have to say: " Well ********************" and move on with a complete redesign etc. Good luck, work safely and have fun


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## dhazelton (Feb 11, 2012)

"I dont think I want to plane it because all the boards need to stay the same thickness"

They will all look the same thickness even if you remove material - who will see it from underneath? Anything you do to fight a bow or cup or twist may fail at some point - wood has a memory.


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## 280305 (Sep 28, 2008)

By how much is that piece bowed? How much effort does it take to push it flat by hand?

As others have mentioned, any difference in thickness can be made to appear on the bottom interior of the table top and will only be seen by dogs and drunks. I recommend against using a lot of force to get the board straight and then holding it in place under tension. Clamps and so on should be used to hold pieces together during glue-up, not to mold the piece into the desired shape.


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## Nubsnstubs (Aug 30, 2013)

From what I seen posted here on this topic, Dtrac, you have a serious misunderstanding of the uneven seam you might have on the bottom of the piece being unsightly, but you're willing to drill lots of pocket holes.. I think that would be even more unsightly than having an uneven glue seam….... 
You evaded the unevenness question that several posters asked you about, so I'm going to ask again. How bowed is this piece when all 3 pieces are laid out together. Is it 1/16" or is it 1"? ............ Jerry (in Tucson)


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## RichardHillius (Oct 19, 2013)

I have done what you are trying to do with limited success. Your results are going to depend on how well the other pieces of the top do at holding the glued up panel flat under the stress that board will be adding to it. Given that you mentioned it's a live edge that tells me it's on the end which makes me concerned it will end up twisting the top over time. Where your method has worked for me in the past I was sandwiching the bow between two or more flat boards and even than sometimes the bow still wins and you will end up with a twisted table top.

I'm not sure pocket screws would add a lot here other than alignment while the glue dries. It's a long grain to long grain bond which is very strong with glue so while a few wouldn't hurt it's the glue that's going to supply all the holding power. Cauls and lots of good clamps will be a must if your going to attempt this with a 2" top.


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## DTrak (May 25, 2015)

Didnt mean to be evasive about how bowed it is. I think about 1/8".

Since I posted that question, I have been working on gluing more of these boards and found some others have similar issues. Some boards are 1/16" thicker than the others to begin with (I had no access to a planer). So what I am thinking is just glue it all together the best I can, add cleats on the bottom (the metal actually goes with the aesthetic anyway) and then just go nuts with a belt sander with a very rough grit to even everything out on top. Like people mentioned, it doesnt matter what the bottom looks like, but it does have to be flat enough for the cleats.

I'm hoping you will now say, "That sounds great, that will work!" because Ive already spent so much money and time on this table.


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## waho6o9 (May 6, 2011)

Welcome to the learning curve and some have fun now!


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## rwe2156 (May 7, 2014)

> If I hold it down flat with weights and then screw it into the adjoining piece with lots of pocket screws, would that hold it flat?
> 
> - DTrak


No.



> You could put some saw kerfs on the bottom side, maybe 3 then fill in with matching wood. this would work best if it bowes up.
> 
> - Snipes


Only works for cupping.



> Your best bet is probably using dowels or biscuits and cauls in the glue up to get it straightened. This will work if the bow is not to bad. Your other option is probably replace that board.
> 
> - johnstoneb


Your best choice if the bow is no more than 1" or so.



> Your best bet is to get another board.
> 
> - bondogaposis


What you're going to end up doing if the above doesn't work.


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## dhazelton (Feb 11, 2012)

"That sounds great, that will work!"

IF you elongate the holes in your metal cleats in the direction of the width so the wood can expand and contract widthwise without cracking. Good luck.


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## DTrak (May 25, 2015)

dhazelton, that is a really interesting idea, but I'm not sure I get it. If the holes are bigger, doesnt that defeat the purpose? Then the strips of wood can pull apart, no?


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## Tennessee (Jul 8, 2011)

DTrak - what dhazelton is referring to is the natural expansion and shrinkage of the wood AFTER you glue it all up and create one big tabletop.
The wood does not stop moving after you glue it up, and if you try to lock it down into your cleats with no movement allowed, it will crack somewhere, eventually.

The glue will not give, but if you try to completely arrest the movement, and you change humidity in the home from winter to summer, shrinkage followed by expansion will make it do things you do not want.

It is why a lot of old chairs fall apart, why table legs get loose, why breadboard ends gain gaps and cracks, etc. And since you are using a natural edge with that big knot in it, there is a huge difference in movement between the rather stable knot section which is very dense, and the more porous sections of the table.

By elonging the holes in the cleats, you allow the wood to move the attachment hardware in the hole with the wood, without losing the cleat.


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## DTrak (May 25, 2015)

Thanks for explaining. I understand now about the wood expanding and contracting over time, but the part I am still fuzzy on is what is then the purpose of the cleats? I thought their job was to arrest the movement.


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## DTrak (May 25, 2015)

This is what I am using. Maybe I was using the wrong word? Maybe this is not considered a cleat?
http://www.homedepot.com/p/Simpson-Strong-Tie-1-1-4-in-x-36-in-18-Gauge-Strap-LSTA36/100375213


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## Snipes (Apr 3, 2012)

rwe - if you say so


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## Tim457 (Jan 11, 2013)

Ok, dumb question, but since one way of making tight bends is to laminate thin resawed strips then glue, is it possible to take the bow out of a board by resewing and laminating back together flat? I'm guessing it's not practical in this case unless the OP has a good size bandsaw and you'd lose some thickness, but how many times would it need to be resewed to take the bow out? Once, twice, or too many?


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## shampeon (Jun 3, 2012)

> is it possible to take the bow out of a board by resewing and laminating back together flat?


That's a tried and true way of reducing the total bow, cup, etc. of boards. Cut it, flatten and square the pieces, and glue them back. You're essentially bisecting the arc, halving the total amount of bow or cup.


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