[daveinjersey]

Just noticed that a couple of the boards I bought a few weeks ago for a table top are slightly warped across the length. Six foot boards for a planned five foot table top are, when laid on a flat surface, maybe a quarter inch high at the center or ends. Not sure if I just failed to look closely when I picked them up, or if they warped a bit sitting in my garage.

What success should I expect from stacking them on a flat surface with heavy rails stacked above to flatten them out? Please tell me something good! I plan to edge-glue these six inch boards. Should I expect to be able to? Should I expect the top to be stable after glue-up?

 

[BernieL]

Good and bad news - The boards that are bent can probably be pressed flat but once you release them and walk away, they will bend again. That's the nature of wood. That was probably the bad news...

The good news is that when it comes time to glue these boards together, alternate the grain on the boards and try using the bent ones between stable ones. Maybe someone else can advise you differently, but without seeing pictures of how badly these boards are bent... I stabbing in the dark. Other factors can play into the equation... like the atmosphere in your shop etc.

 

[TylerJones]

Any reason you can't flatten the boards? When you purchase lumber, and again between each step in milling you need to have the boards stickered so that they can breathe on all sides evenly. You can try stickering them and see what happens.

If you can't flatten them with a jointer then I would just glue them up as Bernie suggested and take down the high spots with a plane or (carefully) with a sander. This is one of the few times it's nice to have a belt sander. I would not try to push them all flat to glue them up, that's asking for trouble later. Realistically you could probably get away with pushing about 1/8" out of them and then just take down the rest until the panel is flat.

Also just like Bernie said I wouldn't try to flatten them with weight, if they are still warped after they sit stickered for a bit then that's where the wood wants to be. Better to deal with the devil you know.

 

[TylerJones]

Next time you set aside some cash for a new tool I would highly recommend a moisture meter. That and a $10 digital thermometer/humidity guage will go a long way towards eliminating guesswork with wood movement.

 

[cabinetman]

You could try overbending. Put a spacer in the middle of board bowed up, and clamp it down past flat. Given time to air out, it may straighten out. Gluing up in that condition could cause the flat ones to bow.

.

 

[MNsawyergp]

I would rip the 6" boards to 3", square the edges on a jointer, and flip-flop the growth ring pattern when you glue up the panel. That is the only way to combat warping in boards or in a glued up panel. Six inch boards are prone to warping unless quarter sawed from the log.

 

[woodnthings]

this is always difficult

Let's say you lay the board down on a flat surface. How much pressure is required to flatten it out? A 5 lb bag sugar? More? If it's not that much you are probably OK.

Is the board just bowed or it it twisted as well? Can you push down the high corner with 5 lbs of pressure? If the boards can be flattened by that amount of pressure you are probably OK.

Lay out everything on a flat surface and see which boards can be used to counter-act each other and place them next to each other.
Using cauls clamp them up dry and see how it goes. If it goes well, and they flatten out rather easily, then you are probably OK.

You are stuck with them probably by now, so go ahead and try the glue up and see how it goes after they dry out. Check the diagonals or have some means to keep the glue up flat on the bench until the glue sets up. Post back your results. :yes:

 

[Al B Thayer]

I would rip the 6" boards to 3", square the edges on a jointer, and flip-flop the growth ring pattern when you glue up the panel. That is the only way to combat warping in boards or in a glued up panel. Six inch boards are prone to warping unless quarter sawed from the log.

This seems the best way. I've flattened lot of boards by gluing them to other boards. I face everything under 8" so no need anymore.

Al

Nails only hold themselves.

 

[daveinjersey]

Just to be clear

My board isn't cupped across it's width, but warped along it's length. Doesn't seem to be twisted, either. It deflects a little under 1/4" at the midpoint of it's six foot length.

An 8 pound weight seems to close it up.

I can give it a few weeks to dry further, but if it's still bent, should I (hand) plane it flat before glue-up?

 

[TylerJones]

I would rip the 6" boards to 3", square the edges on a jointer, and flip-flop the growth ring pattern when you glue up the panel. That is the only way to combat warping in boards or in a glued up panel. Six inch boards are prone to warping unless quarter sawed from the log.

I just can't understand why we are still giving people this advice. It's just not true. We just touched on this discussion in another thread so I won't go into all over again. But I challenge you to go to ANY well respected furniture maker's shop and find a table top glued up with 3" strips. You won't, and they'll look at you like you're crazy if you suggest the 15" boards used in their table will warp because they aren't quarter sawn or the growth rings alternated.

 

[cabinetman]

I just can't understand why we are still giving people this advice. It's just not true. We just touched on this discussion in another thread so I won't go into all over again. But I challenge you to go to ANY well respected furniture maker's shop and find a table top glued up with 3" strips. You won't, and they'll look at you like you're crazy if you suggest the 15" boards used in their table will warp because they aren't quarter sawn or the growth rings alternated.

His statement was that it was what he would do. I agree that some advice is made to sound like gospel. Hard to tell where some get their information. Some get it from reading forums. Some get it from actually doing the work. So, whatever the case, don't let it get under your skin if you don't agree. Stating your beliefs entitles you your opinion. It would be unique in forums though, if there was some sort of 'truth filter'.:yes:

.

 

[Maylar]

My board isn't cupped across it's width, but warped along it's length. Doesn't seem to be twisted, either. It deflects a little under 1/4" at the midpoint of it's six foot length.

An 8 pound weight seems to close it up.

I can give it a few weeks to dry further, but if it's still bent, should I (hand) plane it flat before glue-up?

What you are experiencing is one reason I don't buy dimensioned lumber from the box stores - you start with 3/4" and by the time it's planed flat you don't have enough thickness for the project.

I would flatten it before gluing... but, a 1/4 inch is a lot to lose. Maybe you get lucky and the bowed part is toward the end that will get cut off?

 

[woodnthings]

This covers the basics of making a table top

At the end is a video showing how to make a tongue and groove joint using a router table. This will align the boards to eliniate any mismatch along the edges, assuming they are held flat to the router table when processed and will take any warp into consideration as well. The warped boards must fit together using this joint and when clamped up are self aligning. A full length spline would do the same. A glue joint bit would do the same. A series of cauls would do the same.

http://www.fundamentalsofwoodworkin...g-Articles/edge-joining-panels-and-table-tops

A plank door build from 2 x 10's could also be a table top:
http://www.woodworkingtalk.com/f2/door-build-2-xs-1-4-ply-55717/

 

[Al B Thayer]

I just can't understand why we are still giving people this advice. It's just not true. We just touched on this discussion in another thread so I won't go into all over again. But I challenge you to go to ANY well respected furniture maker's shop and find a table top glued up with 3" strips. You won't, and they'll look at you like you're crazy if you suggest the 15" boards used in their table will warp because they aren't quarter sawn or the growth rings alternated.

I don't think he meant ALL boards would warp.

After looking at the pictures. While not perfect, there doesn't seem to me to be a big enough problem to warrant calling the wood police. Alternate the glue up and deal with what you have left after. Gees.

Al

Nails only hold themselves.

 

[BernieL]

Daveinjersy - I see the boards have a slight problem and that's their nature. Left alone, even if you force them straight for a couple of weeks and dry them out, they will return to their natural state. But you can glue them straight by alternating the grain like Al stated above. The end result may give you a slight uneven edge but a simple cabinet scarper will make that disappear.

I have no idea what the table top will be used for or if it will have a skirt around it... but would it be possible to put the bent boards in the middle of the build and screw a cross member across the bottom to snag those bent boards straight. Even a 1/2 plywood strip would suffice.
If that doesn't work - just glue them up!

 

[daveinjersey]

Daveinjersy - I see the boards have a slight problem and that's their nature. Left alone, even if you force them straight for a couple of weeks and dry them out, they will return to their natural state. But you can glue them straight by alternating the grain like Al stated above. The end result may give you a slight uneven edge but a simple cabinet scarper will make that disappear.

I have no idea what the table top will be used for or if it will have a skirt around it... but would it be possible to put the bent boards in the middle of the build and screw a cross member across the bottom to snag those bent boards straight. Even a 1/2 plywood strip would suffice.
If that doesn't work - just glue them up!

Thanks, Bernie. It's for a coffee table without breadboard or skirt. I could do a cross member underneath, though. I think I'd be ok with alternating grain at the edge. Just to be sure I understand you - you mean something like this - right?

 

[FrankC]

His statement was that it was what he would do. I agree that some advice is made to sound like gospel. Hard to tell where some get their information. Some get it from reading forums. Some get it from actually doing the work. So, whatever the case, don't let it get under your skin if you don't agree. Stating your beliefs entitles you your opinion. It would be unique in forums though, if there was some sort of 'truth filter'.:yes:

.

What would be handy around here sometimes is a second button beside the "THANKS", one that says "BULL$HIT".

 

[cabinetman]

What would be handy around here sometimes is a second button beside the "THANKS", one that says "BULL$HIT".

Not a bad idea, but that's a little too direct don't ya think Frank? Maybe a bit more discrete...like Bull Puckey or NF Way. :laughing:

Wait...I did see on another forum...BIOYA. :laughing:

.

 

[FrankC]

Not a bad idea, but that's a little too direct don't ya think Frank? Maybe a bit more discrete...like Bull Puckey or NF Way. :laughing:

Wait...I did see on another forum...BIOYA. :laughing:

.

What ever works.:laughing:

 

[MNsawyergp]

I just can't understand why we are still giving people this advice. It's just not true. We just touched on this discussion in another thread so I won't go into all over again. But I challenge you to go to ANY well respected furniture maker's shop and find a table top glued up with 3" strips. You won't, and they'll look at you like you're crazy if you suggest the 15" boards used in their table will warp because they aren't quarter sawn or the growth rings alternated.

(end quote)

Forgive me for being "old school", but that is how I was taught back in 1967-8 in high school shop and again in Woodworking 1 and 2 in college as part of my Industrial Arts Teaching major. I also owned and operated a furniture factory for several years. I would guess that I have glued up more solid wood panels than you will see in your lifetime. My experience tells me what I wrote in my first reply. I don't go by what others say. If you don't like my advice. That is your choice, but I do know that flip-flopping the growth ring direction does lessen the warping problem when gluing up panels. Another thing...factories that glue up panels very seldom use boards wider than 4".

As for the 15" planks used by some furniture makers, Most of these wide planks come from a center cross section of the log and therefore do not have the curvature of the growth rings to distort (warp or cup) the plank. If you go to any lumber yard and look at 2 x 12 planks you will see the affect of warping on wide planks. All you have to do is look at the growth ring pattern on the ends of the planks and you will see what I mean.

Now, back to the problem at hand...the questioner uses the word "warped" along the length. That is the wrong term. Warping (cupping) happens across the width of a board. Bowing happens along the length.

For bowed boards to be used in a glued up panel, they need to be cancelled out. It is best to alternate bow up, bow down. I would put the bowed boards in the middle of the panel. If they are put at the outsides of the panel, they could cause the panel to twist.

The small amount of bowing showed in the pictures should be able to be pulled out as the panel is glued up by starting the clamping at the middle of the panel and working toward the ends. At the ends, use C-clamps to bring the boards into alignment. You can use a scrap board across the panel on top and bottom along with the clamps to draw all the boards into alignment.

You can use a spline or biscuits to align the boards, but I don't like the hassle of lining up biscuits while glue is drying on big panels. We had a glue joint 2 sided jointer at our factory that put a small tongue on one edge and a matching groove on the other. When we glued up the panels we would pound the boards into alignment with a mallet so the tongue and groove mated.