Totally random... thoughts on cauls

[Jamie Baalmann]

I don't know if anyone else even uses cauls to try to flatten panels in glue ups but.... I was just thinking if you put a bowed caul on both sides of a panel after clamping it together... what if one caul has less spring then the other and curves your glue up...
Has anyone ever had this happen or should I not even try to use cauls to flatten things???

[Tom Veatch]

I've never used cauls in that particular manner because, as you surmise, the surface between a relatively limber caul and a relatively stiff caul will tend to take the shape of the stiffer caul. That's why I try to ensure that there is a flat rigid support behind the caul, such as the bench or table top.

(like your tag line and have often wondered that myself)

[Brad Shipton]

I have seen router jigs made like this for cutting veneer stock. Usually they only camber one side to avoid the exact problem you mention. It works well, but you might need to consider the size of the caul and camber to make sure the clamping force will flatten properly.

Brad

[glenn bradley]

I use bowed cauls to clamp panels at right angles like a cabinet side to a fixed shelf. I do not try to flatten glue up or other things with opposing bowed cauls as I see no reference point to assure the behavior. I have some four-way clamps that I have used a couplke times. They did not turn out to be beneficial enouhg to offset the clumsiness of using them IMHO for most things.

[Chris Padilla]

See the bowclamp forum. I have 3 sets of varying length cauls from them and they work very nicely.

[John Schreiber]

A trick to ensure that the two cauls put equal tension in place is to clamp . . . never mind. A picture is better. Imagine that their are clamps at either end holding these two boards together over a spacer. Then snap a chalk line, unclamp and cut along the now curved line.

98680

[Jamie Baalmann]

A trick to ensure that the two cauls put equal tension in place is to clamp . . . never mind. A picture is better. Imagine that their are clamps at either end holding these two boards together over a spacer. Then snap a chalk line, unclamp and cut along the now curved line.

98680

I like that John... I'm assuming you mean to mark both of them and then cut both of them then you know that they are equivalent. I guess just make sure you mark the pair so that you don't get sets mixed up when using more than one set of cauls.

[John Schreiber]

I like that John... I'm assuming you mean to mark both of them and then cut both of them then you know that they are equivalent. I guess just make sure you mark the pair so that you don't get sets mixed up when using more than one set of cauls.
Yep and Yep. I guess you can't be sure that they'd be exactly right, but I've used it for table top glue ups and it has done the job.

[Bob Ross]

Jamie,

Great topic. I have not used nor thought to use cauls since I started using clamps on both sides of the panels. This I learned from a pro on one of the forums. I also use a lot of clamps and I don't use much pressure. IMO, the clamps do not exert perfect lineal force across the panel. It seems that most clamps exert part of their force away from the bar (or pipe), causing some bow. Alternating them top and bottom seems to negate this wayward force. The high number of clamps allows a cumulative effect, spreading the force evenly, I think :confused:. Anyway, it works.

[Peter Quinn]

Not much to add. But for fun google 'Larry's clamp' or check it out at Schmidt. Now that is a caul!

[Jamie Baalmann]

Larry is pretty proud of his clamp at those prices... Production shops have been using the same idea for years.

[Jim Becker]

I use my Bowclamps for this. While one can make similar in the shop, I have found that the precision machining that Craig does makes for very even pressure.

[Peter Quinn]

Larry is pretty proud of his clamp at those prices... Production shops have been using the same idea for years.

I have seen factories using similar custom clamps but don't know of any others available to the average small shop. Larry isn't giving those things away, but in a production environment those things are gold. I demoed them at an industrial show and they really do work great. For the average wood worker? Probably overkill, no?

I work in a small production shop, occasionally making stair treads en mass and I would kill for a clamp like that. I use, lets say, other methods (bowed cauls, swearing, chants, clamps, very large dead blow, more swearing, etc.) The stair treads I make sell for $120 each, wouldn't take the boss long to pay for Larry's clamp, but then what would I do with all my free time? I have not bought one for my own shop yet as there was a drought that wilted my cash tree this year:D, maybe next year?

[Peter Quinn]

Ps, there really is a man named Larry, very pleasant older gentleman that designs and sells those pneumatic monsters. He demoed the clamps to me himself, with much glee I might add.

[Aaron Dunham]

I use 2" x 2" x .125" square steel tubing top and bottom with the top in between, x 5 or maybe 6 depending on the top length. Wax paper between the steel and wood prevents the wood from blackening.

[Jacob Reverb]

A trick to ensure that the two cauls put equal tension in place is to clamp . . . never mind. A picture is better. Imagine that their are clamps at either end holding these two boards together over a spacer. Then snap a chalk line, unclamp and cut along the now curved line.

98680

That's slick!

[Brad Shipton]

Peter, Larryclamp seems interesting, but wouldnt a glue joint be just about as accurate?

Brad

[Samuel Brooks]

What determines the size of the spacer used between the boards?

Thanks,

Sam

[Maurice Ungaro]

Bowclamp.
Bowclamp.
Bowclamp.

[John Schreiber]

What determines the size of the spacer used between the boards?
When I did it last, I used a 4x4 on end about 8" tall. When I screwed down the clamps, I just tightened until the tension felt about right. :o The 2x4s I was bending lost about 3/4 of an inch at each end.