Panel gluing suggestions?

[Boilermaker]

I'm in the process of making a dresser/changing table for my son (due in January). I decided against plywood and I'm using solid cherry edge jointed to make one large panel for the top and sides. For the top and sides I have four boards about 5 inches wide that I've joined and glued using biscuits. When I glued everything up, I'm noticing that there is a small cup in the middle of the panel. I'm suspecting that when I clamped everything together I may have put too much pressure on the boards causing the middle of the panel to cup a bit.

What tools/techniques does everyone else use to prevent this? The cup isn't too bad that I think it will affect the project too much (although putting in the drawer rails should be interesting), but I would like to find a way to eliminate this altogether in future projects.

 

[timf67]

Did you alternate your boards after jointing? if your jointer is out of square by even a small amount, the error will multiply as you add boards. To fix this, you alternate which board face is against the fence for each board in the glue up.

 

[bobby g]

Did you alternate your boards after jointing? if your jointer is out of square by even a small amount, the error will multiply as you add boards. To fix this, you alternate which board face is against the fence for each board in the glue up.

+1 ....and then I use cauls and clamps to keep it flat and everything aligned. See photo below. No biscuits are needed using this method. The cauls are covered with packaging tape to prevent them from being glued to the panel. I have found this method to be bullet proof! You can get complete details on NewWoodworker.Com. http://www.newwoodworker.com/cauls.html

bobby g

View image in gallery​

 

[striker]

Scott,

Generally, I hand plane the board edges being glued back to back so any variance in the edge squareness ends up being complimentary to one another. There’s a better chance the panel will remain flat.

My preference is to glue up in a sort of rub joint fashion. After applying glue I rub the halves together then clamp with a minimal amount of pressure while checking flatness. Possibly adding cawls if necessary. Usually, I plane after the glue up which addresses any issues such as cupping.

At this point if the cup is severe to warrant it, you can saw down the glue joint, rejoin, then glue back again.

Stephen

 

[SteveHall]

Several places sell this sophisticated aluminum panel clamp that compresses the parts from all directions to minimize slippage and warp. I've never used one but am always tempted to when I encounter the same issues you've seen, if not for the price.

There's also a derivative clamp mechanism that lets you make the cawls, like the Veritas panel clamp, Woodcraft clamping system, and the Rockler clamping system. But I tend to think aluminum/steel would be better since the flexure of the panel piece might be similar to any wood cawl you could make short of it being 6" thick. A considerably cheaper solution than the first one though.

Finally, I once saw a home made panel clamp that used a sheet of melamine with bracing behind as one flat side. The panel parts laid on top and were compressed in both directions with a sort of clamp-and-wedge cawl system. You can see a similar guitar panel clamp about half way down this Lumberjocks thread. (Some other suggestions within this thread as well.)

HTH.

 

[Ken Massingale]

I suspect too much pressure also. If you had to apply significant pressure to get the edges nicely together, the edges weren't right. Proper cauls are needed too as others mentioned.
HTH

Ken

 

[mkepke]

Another tactic is to place clamps on both side of the panel - this equalizes the tendency of the (unbalanced) clamping force to cup the panel.

-Mark

 

[petebucy4638]

Did you alternate your boards after jointing? if your jointer is out of square by even a small amount, the error will multiply as you add boards. To fix this, you alternate which board face is against the fence for each board in the glue up.

That is an excellent technique that you hardly ever hear anyone talk about. It is simple to do and can save a lot of grief afterward.

Pete