Panel Clamps - Do they make sense?

[Kent A Bathurst]

I like that idea of grooves for squeeze out, but how does that work with the packing tape over it? Any pics?

Allan - this is from a build sequence for a table top. Shows everything in its place pre-glue up, and then the process. Best story on the cauls and my accessories that I have.


Cauls in place. You can see the grooves for squeeze-out

Note the cradles they sit in. this gets them at the correct min height off the table for the c-clamps.

Note the holders for the 3/4" pipe. Sections of 1" PVC, snapped in place, Ply scraps to build a base to match the height of the wood.

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Grooved and taped blocks for the ends.

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C-Clamps in position. I want to know I have everything in place, so I don't have to stop and go running around mid glue-up.

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Boareds on the cauls - aligned over the grooves.

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Glued and clamped. NOtice that [for the most part] the pipe clamps alternate above and below the wood. COunteracts any bowing tendency.

Also - look closely at the pipes - you can see the PVC snapped on teh pipe - these are spacers to keep the black pipe out of the damn glue.

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End blocks in place. I had a problem once, where everything came out great except at one end -- not flat at the joint. Stopped that noise.

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Good photo of the glue squeeze out running through the tunnels.

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I have one card scraper assigned to glue squeeze out. It doesn't have to be really sharp, and it doesn't have to be clean.

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[Kent A Bathurst]

OK - could not get the entire photo sequence in above..

Change to a good card scraper for a few minutes.

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Now, then - You are looking directly at where the glue line is. Where's Waldo?

My point is simply this - if you have the right methods, attention to detail, and focus, you don't need biscuits or dowels or nuttin' to get a near-perfect glue joint alignment. Those boards were dead-nuts in line.

For top-end show surfaces, I only glue one joint at a time. They all come out like the one you have seen here.

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THe cradles for the cauls are made from scrap whatever-was-handy. THis one looks like 3/4" ply scraps.

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Same with the bases for the pipe clamps. Looks like I used some QSWO scraps for the end clamping blocks.

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[John TenEyck]

I wouldn't claim that all my panels come out so good that it requires nothing more than a card scraper to get perfect, as Kent's are, but mine generally come out well. I've found the most important thing is to get all the joints not only to fit together well but at a perfect 90 degrees so they don't squirm during clamp up. This sounds obvious but do you know if yours really are that good? Well, if you stack up all the boards for the glue-up it becomes crystal clear.

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When they stand up like this, they are. Any joint that's not will make the panel tip one way or the other. When the joints are perfect, glue up is pretty easy, and I generally need nothing more than finger pressure or a gentle wrap of a rubber mallet to flush the boards as I pull up the clamps.

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After removing the clamps:

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Note I'm gluing 4 boards, too.

John

[Keith Weber]

I'm trying to decide if I should get some kind of panel clamp. Either 2 of these:

http://www.rockler.com/damstom-38-in-panel-clamp...

Allan, just to point out what might not be obvious to everyone, those Rockler clamps that you linked do nothing in terms of keeping your boards from lifting relative to another like a caul would. They give the illusion that they'd be doing something because of the bar that sits on top of the glue up, but that bar does nothing more than provide symmetry and clamping pressure in the normal direction. I'd rather use a pair of K-bodies or Jorgensons than those.

I have a set of Frontline clamps that are awesomely great for this purpose, but they're priced on the ridiculous side, and you'd better be planning to visit Australia if you want them because Frontline won't answer your e-mails or phone calls if you don't live in Australia. I just about gave myself a heart attack hauling 6 of them through 3 airports to get them to my shop -- a task I would never want to repeat, no matter how nice the clamps are.

[Andrew Joiner]

I use the rubber mallet method like John. Simple and fast. The trick is to clamp one end of the glue-up tight with all faces flush, first. Then work your way to the other end like this: Barely tighten the next clamp so you can pound the faces flush. When flush, tighten and move on down the panel. I've done panels of 7 or 8 boards this way, but if the boards are long you have to work fast. Titebond Extend is my favorite glue for this.

Pipe clamps work fine for this. There is no need for any "panel clamps".

[Allan Speers]

Allan, just to point out what might not be obvious to everyone, those Rockler clamps that you linked do nothing in terms of keeping your boards from lifting relative to another like a caul would. They give the illusion that they'd be doing something because of the bar that sits on top of the glue up, but that bar does nothing more than provide symmetry and clamping pressure in the normal direction. I'd rather use a pair of K-bodies or Jorgensons than those. .

Wow, thanks. That's one seriously misleading ad / product.

[Allan Speers]

[QUOTE=Kent A Bathurst;2403572]Allan - this is from a build sequence for a table top. Shows everything in its place pre-glue up, and then the process. Best story on the cauls and my accessories that I have.......


VERY nice tutorial, Kent. Thanks.

[Chuck Hart]

I would start here:

http://www.highlandwoodworking.com/w...ril/cauls.html

[Allan Speers]

A new question regarding cauls:


I couldn't tell from Kent's pics, but in that Henderson tutorial Chuck Hart linked, above, he is clearly using cauls both above and below the stock.

Wouldn't it be better to have straight supports underneath, and just put the curved cauls on top?

[Keith Weber]

A new question regarding cauls:


I couldn't tell from Kent's pics, but in that Henderson tutorial Chuck Hart linked, above, he is clearly using cauls both above and below the stock.

Wouldn't it be better to have straight supports underneath, and just put the curved cauls on top?

You have to balances the forces on the top and the bottom to get a straight panel. So, if you want to use cauls top and bottom, you need to:

A) use identical cauls so that the forces balance out top and bottom, and
B) clamp the cauls together so that it is separate from the workbench.

If you clamp it as above, but use a straight support underneath (that's made similar to the caul, but without the curve), then the top caul will bend a cup into the top of your panel. You could use a straight support underneath, and a caul on the top, but that lower, straight support would need to be much stronger and rigid than the top caul to resist the cupping tendency - say, by using a 2" x 4" x 1/4" wall rectangular steel tube (on edge) as your lower support.

If you only wanted to use a top caul, you could get away with that if you clamped your whole setup to a rigid and flat bench. Your vertical clamps would go from the underside of the workbench to the top of the caul. The downside of this is that you cannot move the panel until it dries. Again, your workbench would need to be much beefier than your upper cauls so that the caul does not cause flex in your workbench.

The easiest and safest way would be to just use similar cauls top and bottom.

[Robert Engel]

Wood will do what wood will do, no matter how you clamp it. After you take the panel out of clamps it will go the way it wants to go. That's why stock preparation is so important.

Mike

This is exactly correct. I don't use them I just try to prepare the stock as uniformly as I can and glue it up as soon as I can.

Couple tips:
1. If using a jointer, edge them with alternating faces to cancel out any 90 error. If doing by hand, plane two boards facing for same purpose.

2. If you plan on hand planing the panel, make sure you have determined the grain direction is all the same prior to gluing. There's nothing worse than finding out two boards have the grain running opposite ways and you're stuck with scraping or sanding.

Sometimes reading the grain is almost impossible (and if you think you got it right, you find out later you didn't) dependingon the wood in which case I will actually (gently) try taking a test shaving just to be certain.

3. I'm a big fan of bagging in plastic bags during after each milling especially when the weather is changing.

I glue my panels based on grain direction and orientation (sometimes they conflict) but hardly ever on the alternation growth ring method.
Although theres nothing wrong with that, it will not cancel out cupping.

I never use cauls you shouldn't have to if your stock is straight and uniform.
If the stock is warped then you need a spline or biscuits.
I just put slight pressure with clamps and feel the joint use a soft hammer to adjust.
I usually clamp each joint at the ends till the glue is set.

Try them out and let us know how you do.

[Allan Speers]

You could use a straight support underneath, and a caul on the top, but that lower, straight support would need to be much stronger and rigid than the top caul to resist the cupping tendency - say, by using a 2" x 4" x 1/4" wall rectangular steel tube (on edge) as your lower support.

That's exactly what I was thinking. Use a straight bottom "caul" with steel rail reinforcement. Then you don't have to worry about the top & bottom cauls being perfectly matched, you'd always get a dead-flat result. I'm going to try this first, and see how it goes.


BTW - Clamping directly to the assembly table has another negative: No place for the glue to run out.

[Kent A Bathurst]

That's exactly what I was thinking. Use a straight bottom "caul" with steel rail reinforcement. Then you don't have to worry about the top & bottom cauls being perfectly matched, you'd always get a dead-flat result. I'm going to try this first, and see how it goes.


BTW - Clamping directly to the assembly table has another negative: No place for the glue to run out.

I always use the cauls top and bottom - one pile of cauls, interchangeable. No issue about dead-flat result - - the cauls are identical, the C-clamps are applying the same force equally to the pair, they came out of the same species [heck the same stick from the same tree] - and they react the same to the force.

I think you might be overdriving your headlights here............

On the flat table-top - - glue mess on the underside, plus - the required table top dimensions will vary with the size of the workpiece, no?

But - hey - if the flat table top gets you where you want to go, tee it up!!

One thing I did not emphasize in my earlier posts -- I use primarily QSWO. SOme of it is really big $$$. WO has deep pores. Any glue that gets smeared on the surface will fill those pores, and inhibit dye absorption. So - it is a critical step - and a non-trivial step - to get the glue out of there. I decided the best way to do that was to keep the damn glue out to begin with.