Tutorial: Shop Made Cauls

[Matt Day]

I need to make some too - thanks so much for the step by step!

However, I think I'll make one using a hand plane but to make copies of it I'll probably use the router with a pattern bit so I can knock out mutiples. What do you think?

[Kent A Bathurst]

.... to make copies of it I'll probably use the router with a pattern bit so I can knock out mutiples. What do you think?

Matt - I think that's a great idea - then they will all be the same, and will all act the same way, regardless of which one you grab. Tee it up.

[Mike Henderson]

I need to make some too - thanks so much for the step by step!

However, I think I'll make one using a hand plane but to make copies of it I'll probably use the router with a pattern bit so I can knock out mutiples. What do you think?

That should work. Bill Huber (above) says that he has a template. Contact him and maybe he can send you a copy. He only needs to send you one side, then you can duplicate it.

But you can knock these out with a hand plane pretty quick. It's not something you're going to do every day and you don't take a whole lot of wood off so my recommendation is to use the plane and enjoy the feeling of some hand work.

Mike

[dan sherman]

Mike, how does this jive with your real world cauls?

my assumptions:
1. over a 24" span I would use 4 clamps
2. each clamp applies 75% of maximum clamping pressure
3. cauls are SYP

thus:
1) 0.75 * 1000 = 750lbs. (force excreted by each clamp)
2) 750 lbs * 4 = 3000lbs. (4 clamps)
3) 3000lbs. / 2 = 1500lbs. (divide by 2, because cauls are used as sets)

running this through the sagulator, says the center of the cauls should be roughly 3/64" of an inch thicker then the ends.

[Ben Martin]

Yep, those are the 12" and I find that I use them quite a bit. When I first got them I thought they would be "special purpose" clamps but they're more like "general purpose" clamps for my use.

Mike

[Oops, I hope we're both referring to the same picture. Most of the pictures show the 12" and I think that's what you were referring to.]

Yep, that's the one! I got a steal on some 24" Jorgy's, I think that I will be modifying them a bit down to 12".

[Mike Henderson]

[This is in response to Dan Sherman's post above]

What I did was go out to my shop and measure the gap on one of my 48" cauls - see pixs.

With the end and the middle clamped, the opening on the other end is about 5/16". Another set would probably have more or less of a gap since I decide the gap by feel (pressure on the clamp). Also, remember that I'm using fir.

I can't really analyze that for you except to say that it works for me. A bigger gap would give more force in the middle of the cauls.

Mike

[Scott T Smith]

Great info here - thanks Mike, Wes and others. This thread has been printed out for my shop notebook.

Scott

[Wes Grass]

Hmm. Mine are Poplar, 36" long, 2" thick, and I think about 3" tall. I'd have to double check to be sure.

I arched one side 1/8" and the other 1/4". According to the Sagulator, 900lbs in the center should straighten the 1/8" side. That sounds like quite a bit, but when I actually tried them it seemed like not nearly enough force to keep the panel straight, so I flipped them to the 1/4" side. That didn't seem like a lot either, actually. But getting 4 or 500 lbs thrust from a screw doesn't take a lot of torque.

[Brent Ring]

Just one other suggestion - I frequently check the scrap bins at the orange borg, and recently found some 4', very straight (and straight-grained), reasonably knot-free, KD cutoffs - while not free, they were only .51 a piece. I bought 6 boards, and have enough to get started making my cauls now. Every orange borg that I have been to in Utah puts their cutoffs in a scrap bin. You have to pick thru, but you can find some gems once and awhile. I even built a router table a few years ago and the bulk of the carcass only cost me about $15.00. Someone left some awesome 3/4" melamine coated mdf and top grain plywood.

Just an idea for the cost cutters out there

[Michael Schwartz]

I recently did a tutorial on making cauls. I'm sure many of you already know how to make cauls but new woodworkers often do not.

For those of you experienced, I'd appreciate comments and suggestions - especially on better ways to make cauls.

Mike

nice cauls, I made a very sturdy set out of 8/4 ash a few weeks ago but regardless of the material they have endless uses.

My next shop project is a flat MDF torsion box to be used in combination with cauls.

[Cody Colston]

Great tutorial, Mike. I personally don't believe that caul design is rocket science but your method is an easy way to keep them consistent between pairs. I'll be making a few when I get home.

Thanks again for taking the time to document the process.

[Salem Ganzhorn]

Thanks Mike! I made some using your method a couple days ago and used them for a glue up. Really nice! My only additional comment is to use a setup like Kent's to elevate them to make room for the clamps. That worked great!
Salem

[Karl Brogger]

I'm not sure I understand what these are for.

Using a stick to spread out clamp pressure is pretty much SOP, but I don't understand how using two clamps is better than say 5 with a straight piece.

[Stephen Edwards]

I'm not sure I understand what these are for.

Using a stick to spread out clamp pressure is pretty much SOP, but I don't understand how using two clamps is better than say 5 with a straight piece.

I've only worked with cauls a few times. I'm not certain that it is better. But, the few times that I've used them they worked just as well as the traditional method of using a straight stick and a bunch of clamps.

To me the advantages are twofold.

You don't need as many clamps for a particular glue up. If you have a lot of glue ups going at once, not having enough clamps isn't a problem.

On some glue ups that I used them for, using two clamps was the only practical way of performing the operation, one clamp on each end of the caul.

[Mike Henderson]

I'm not sure I understand what these are for.

Using a stick to spread out clamp pressure is pretty much SOP, but I don't understand how using two clamps is better than say 5 with a straight piece.

Cauls are generally used where you can't get a clamp. Suppose you had a cabinet with a shelf set into a dado and you wanted to apply pressure along the outside panel where the shelf is to make sure the shelf was fully seated during glue-up. If you had some clamps with very long reach jaws, you wouldn't need cauls. With cauls, you can put a caul along the outside of the cabinet, in line with the shelf and get pressure all along the panel. You might only use two clamps, one on each end of the caul.

Another common use is for flattening a panel during glue-up. You can use cauls without any curvature, but you won't get a lot of pressure in the middle of the panel because the caul will flex. By using a curved caul, you can apply pressure all along the caul, which will help align the boards of the panel, and will keep the panel flat while the glue sets.

There's a whole lot of situations where cauls can be used, and Craig Feuerzeig of Bowclamps has described many here on the forum and on his web site.

Mike