Tutorial: Shop Made Cauls

[Mike Henderson]

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

[Jim Rimmer]

Mike:

Thanks for the tutorial. I'm not a newbie exactly but not real advanced either. That's some good info I can use.

[Dan Forman]

Mike---Thanks for this, I need to make some. Don't you run into trouble though with planing against the grain on one half of the caul, when starting in the middle?

Dan

[Mike Henderson]

Mike---Thanks for this, I need to make some. Don't you run into trouble though with planing against the grain on one half of the caul, when starting in the middle?

Dan

Softwood, like fir used in construction 2 by 4's, is pretty forgiving. I never had any serious problem hand planing it.

Kent - how about some pictures of your setup. It would help to understand what you've done.

Mike

[Kent A Bathurst]

Kent - how about some pictures of your setup. It would help to understand what you've done.

Mike - here you go - sorry for the delay - camera was on vacation in Philly for a few days, but it eventually followed SWMBO back home.

Simulated glue-up. Real thing has pipe clamps alternating over/under. Also, some type of screw clamp on the glue joint at the ends to pull the joint tight there. The "X" is flat - cauls taper from the "X" to the ends. I center the glue line on the "X" on the bottom cauls, and then use the wrap-around lines to align the top cauls - so the 2" flat spots are centered on the glue line. C-clamp and crank the ponies. Cello packing tape on the "X" caul surfaces. All I need is a card scraper or scraping plane to smooth the joint.

Photo 001 shows the "U" fixtures nested - they stack real nice that way . The first version - I failed to allow enough room for the C-clamps to slip under the bottom caul - lesson learned - raised the "U" and pipe bracket height.

FWIW - a section of wall has those PVC clips screwed in vertically-aligned pairs between studs - the pipe clamps snap into place and stay where I put 'em. Also - you'll see PVC clips that slide on the pipe - keeps pipe out of the glue.

I need to do the "clamp on paper strips" trick noted in an earlier response. Mine seem to work great, but I could never think of how to check the curvature of the earth under clamp pressure - that is the way.

[Kent A Bathurst]

Mike - looks good - straightforward instructions. I got so aggravated years ago at scrambling around trying to find stuff to use for cauls that I bit the bullet and made a set - I think I have like 20 of them, all exactly identical.

Mine have a lot in common with yours, but there are some differences:
1. I used 10/4 hard maple, ending at about 2-1/4" square. Yeah - maybe overkill, but I wanted do do it once. That was 10 yrs ago.
2. I wrapped two lines around the centere of the caul, 2" apart (1" offset from the center line). On the face to be toward the glue joint, I put an X in the middle of that box. These lines tell me where the center of the caul is, looking from any direction, and the X tells me which side goes against the glue-up.
3. Mine are 32" long. I taped a stacked pair of dimes to one end, then set the dime end well past the running jointer head, and plunged the caul down, and moved if forward. Repeated until the jointer cut came to my line. Then, pulled those dimes, taped 4 dimes to the cut end, and repeated for the second end. No better than a handplane, just faster, and both bevels are identical. Clear packing tape, of course.

Accessories: I used scrap plywood to make pairs of U-shaped brackets (the U opening sized to receive the caul), attached to a piece of plywood as a base, with the pair offset by about 12". This gives me a flat, stable base to keep the cauls up off the bench. The height was designed to let me get a C-Clamp under the caul. The entire setup runs up to 1"+ panel with 6" C-clapms, over that takes 8" clamps.

Last, I used a bunch of 3" square pieces of plywood to make a bunch of short stacks. On top of each stack I screwed a piece of 1" PVC that has a slice of about 40% cut away. The height of the stack is correct to allow a 3/4" pipe-clamp to be snapped into a pair, and hit the correct glue-up height, as already determined by the U brackets and cauls. Someday, I'm going to make a set with grooves to receive and hold parallel clamps, but with this setup and the cauls, I have no trouble at all with the pipe clamps - the fixtures to hold the clamps lets me easily alternate above-below, without fumbling around.

As I am in the glue-up, the lines around the cauls tell me where the "flat spot" is to center over the joint.

Since I started using these, I have never again needed to run a glue-up through the surface planer. I use a card scraper or a scraping plane for the very minor offset I get, if any.

[Bill Huber]

Good info.... I will have to say I am lazy and can't use a plan for anything yet so I have an MDF template that I use with a trim bit to make mine.

[Peter Quinn]

Nice tutorial Mike. I use a jointer to do mine at work. A few light passes in each direction from a center line and maybe a bit of tune up on a big horizontal belt sander. A few seconds to make a set from the scrap bin for any given project. I usually use soft maple when its available, though I have used sappy WO, sappy black walnut, MC ash, whatever 8/4 material was left over from the last job and usable for other work. I think we use the same brand of tape!

I understand the bow clamps are nearly perfect renditions of this concept, and though I have never used them, I am amused that wood workers would pay so much for something they can make very effectively and cheaply to suit most purposes.

[Mike Henderson]

Craig Feuerzeig was kind enough to send me a PM and suggest a way of testing the contact along the cauls. He suggested putting pieces of paper along the joint and see if you can pull the paper out.

So I went out to the shop and did that test. I found one spot that was not tight but was able to adjust it easily. See the pictures.

And thanks to Craig for this excellent test technique.

Mike

[Wes Grass]

I clamped a pair together with spacers at the end, warping them until the centers touched, and then jointed the outside edges straight. Generates a proper catenary curve.

The trick is in clamping them together. I bored 1/2" holes across the center, and made a couple of steel bars with 1/4-20 threads in one and a clearance hole in the other, bolts on each side to pull them together. Putting the holes across the center line has little or no effect on the stiffness. Might be able to do this with dowel and wood screws too. Or if you make the hole big enough, you could hook a small f clamp through one at a time.

Since they hung out the sides I had to use the jointer. Or maybe use a long wood screw, *well* countersunk, and straighten them out on a table saw.

[Prashun Patel]

Thanks Mike. This was very useful to me.

[Mike Henderson]

I clamped a pair together with spacers at the end, warping them until the centers touched, and then jointed the outside edges straight. Generates a proper catenary curve.

The trick is in clamping them together. I bored 1/2" holes across the center, and made a couple of steel bars with 1/4-20 threads in one and a clearance hole in the other, bolts on each side to pull them together. Putting the holes across the center line has little or no effect on the stiffness. Might be able to do this with dowel and wood screws too. Or if you make the hole big enough, you could hook a small f clamp through one at a time.

Since they hung out the sides I had to use the jointer. Or maybe use a long wood screw, *well* countersunk, and straighten them out on a table saw.

Great idea, Wes. You're right - that will produce the proper curve, accounting for the flexibility of the wood, which is variable sample to sample. No calculations, no muss, no fuss.

I'm going to try that.

Mike

[Dan Forman]

This thread just made it into my woodworking folder. Thanks everyone.

Dan

[Garth Keel]

I appreciate the time you took to put this together and the pictures.

[Myk Rian]

Thanks for the writeup. Great info.
Definitely sticky material.