Cauls for panel gluing ?

This may be a very low-tech response, but I use whatever scraps I happen to have laying around when I need cauls to glue up a panel.

As far as the glue issue, I just put a folded piece of waxed paper between panel and caul.

-- Charlie M. "Woodworking - patience = firewood"

Here is a response for a similar question that Marc Spagnolo sent out today via e-mail:

How To Make Cauls? – Question of the Week

Posted: 09 Jun 2008 07:49 PM CDT

This week’s question comes from Geoff. He writes:
I have a question about cauls and how to make them. I have made some small ones (about 24″) out of some 2x pine. They did the job of gluing up a small table top, but… I want to make a real “set” of them but I don’t know what to make them out of. Could I laminate 1/4″ ply (I have a lot of scrap!) over a curved form to create a slight camber or should they be made out of maple or another hardwood? Thanks for the help and keep up the great work!

And here was my response:

Here’s the great thing about cauls Geoff. They can be made out of just about anything. I have a little bucket that I keep behind my bench that is full of little scraps of wood of all shapes and sizes. But they are really just scraps. Nothing made specifically for that purpose. The only time I specifically make cauls is when there is a very special clamping situation. And usually I use them for that task and wind up losing them a few weeks later.

So I use everything from plywood to solid wood scraps of all species. If you are making a really nice set, you probably can’t go wrong with oak or maple. Poplar would be a fine choice too, as would plywood (if done correctly). If you make a cambered caul out of 1/4″ ply, like you mentioned, you’ll need quite a few strips before the sandwich is sufficiently resistant to bending. You want enough resistance so that the crown of the camber provides the appropriate amount of pressure. You might have more luck using solid wood, but the ply is certainly worth a shot.

• For those who don’t know, a cambered caul is simply a caul that has a curve in it. These are most useful when clamping long surfaces where you can’t get clamping pressure in the middle of the joint. The best example I can think of is clamping a bookshelf into a dado in the side of the case. The crown of the cambered caul goes on the center of the joint and the ends get clamped down. This applies the needed pressure all the way across the joint. The trick, is figuring out how much of a curve to put into the caul in the first place.

-- With God's help all things are possible- even woodworking. Woodworking is not just a hobby, it is an (expletive deleted) expensive hobby.

I put a few coats of polly on mine and then a put a stip of painters tape on the faces that come into contact with the panel. So far this seems to work pretty good.

-- Glenn, New Mexico

Charlie, Scott, (Marc), I would ususally use scraps, but I quite honestly don’t have any scraps here suitable to use. That is why I had to borrow some. :^)
The last few projects have been toys, therefore, scraps gone.
I decided that if I had to buy wood to make cauls, I may as well do it right. That way I won’t get caught without, again.
I think as far as crown goes, I’ll try 1/16th each end from centre.
Thank you all for your replies.

-- If we learn from our mistakes, I'm getting a fantastic education.

Clear packing tape is a good solution to keeping the glue from sticking.

I have some cuals that I bought and the work great. A fellow woodworker on a different forum makes them. Here is the link to his site http://www.bowclamp.com/. I have used them for pressing veneer on to a dresser and had exellent resulsts.

For keeping the glue from sticking use wax paper.

I just do like Charlie.

-- Gary, East TX -- The longest journey begins with a single step.

Another vote for the BowClamp cauls. They work great.

-- Use the fence Luke

I have a set of cauls that came from Charlie & Gary’s place. Keep an eye out and when you have a number of similar sized dropoffs from good, thick, ripped stock that will hold up to clamping tabletops & etc., Keep them and use them for that. More than several times I’ve had customers ask what those “boards” are for under my glueup table. I’ve had some of them for years. bbqKing

-- bbqKing, Lawrenceville

I must admit I use cauls routinely, mine are about 30 inches long and are crowned to about 1/16” on either end. They are made from 2×2 maple stock that I got at the sawmill as junk wood. When I first started using them I never thought that squaring them perfectly would critical however after a few uses I found out that taking the time to square them up made a huge difference. As far as glue goes the packing tape sounds like a great idea. I happen to have a doctor friend who gets me rolls of the table paper they use on the examining table that I use for my glue ups.

-- Derek Tay, Venerate the Tree Design

A question on cauls – I see many references to cambered cauls but don’t have a bandsaw so can’t figure out how to make them. I sometimes use a thin shim in the middle of the length of the caul – doesn’t this serve the same purpose as the cambered caul?

Jim,

I just hand planed my caul’s to camber them.

Derek

-- Derek Tay, Venerate the Tree Design