Official Luthiers Forum!

So far I've been using those cheap HW store iron clamps, with screw and "flexible" jaw. They are sometimes awkard to use because they can slip off small or rounded stuff, but they have excellent clamping power.

I ordered a Klemmsia especially for gluing bridges. The clamping is let's say ...delicate, for example if I clamp two flat pieces of wood, i can slide one against the other without much elbow grease.

And the jaws are not parallel. Is it common for these to require tuning, as in removing cork and truing jaws, and maybe insert some veneer in the slot to increase the clamping strength?

Thanks!

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Build log

Cam clamp jaws will never be exactly parallel to each other in the loaded position. The upper jaw needs to pivot a tad and bind the slide bar between the locking pins to hold the jaw position, this means the upper jaw will be either slightly tilted down or up to get both the lower pin and upper pin to be engaged to the slide bar at the same time. The Cam moves the tong down to add the required griping pressure. I suppose you could tune the foot on the tong if you wish but I have never worried with as I tend to use a caul between the cam clamp and the bridge. So I never worried that the tong was only partially engaged with the caul or component. it still provides a specific lbs per sqin of clamping pressure no matter it is engaged on part of the tong or the complete tong. The slide bar will wear over the yeas of use and the upper jaw will pivot more as this wear takes place but I see no issue with that. If you tune the tong you will for ever tuning the tung as the slid bar and locking pins wear

It is my belief that a cam clamp was not designed to have the tong setting dead flat to the component when fully engaged but rather to provide a certain pressure at a given point of cam engagement and allow a caul to spread that load.

Thanks; you are quite right about the wear and subsequent angle change.

How about the clamping force. Another similar example to the above: I can't use it to reliably clamp a small jig to the bench. It will wiggle around.

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Build log

even though the slide bar and pins wear they continue to work equally as well. What happens is the angle of the upper jaw increases allowing the pins to wedge into the slide bar. the griping or clamping pressure has not changed and the clamp is no more prone to slipping that's it was new. It still offers the same clamping pressure and is just as reliable as it was freshly built, to a given point of wear. What will change the clamping pressure exerted is excessive wear of the cam. As the cam wears the amount it will push down the tong will decrease. But a cam is easy to make and replace as are the wedge pins for the mater.

I have some cam claps my grandfather made in the 50's. Well worn the pins were getting near flat on the side facing the slide bar but they still work fine and I have never had on come loose of it own fruition.


Screw type bar clamps have an advantage of cam in the amount of clamping pressure that they can be made to exert. But I can mot think of anything in most wood working when a cam clamp is insufficient for the job. I think you must have miss understood my opinion on cam clamps. I love them. I use them in most every clamping process in my building.