Official Luthiers Forum!

Hello,
Several of my cam clamps slip back and do not hold well. I roughed up the surface with sand paper but it did not make much difference. I hit it with a rat tail file to make it rougher and it still slipped. I slid a piece of sandpaper in and it seemed to work better.
Any ideas on how I can get these clamps to work well? Thanks...

Some cam clamps have a smooth metal bar, some have little grooves every 1/16" or so. For me the ones with the grooves work better. I assume yours do not have the grooves if you put some in with a file it has to help. But, I have never tried it.

_________________
Joe Beaver
Maker of Sawdust

Don't over tighten the clamps, that can cause it to slip. Use just enough pressure to mate the joint.

Alex

_________________
"Indecision is the key to flexibility" .... Bumper sticker

Hi, Richard. Do mean the clamping head is slipping on the bar, as Joe surmised? I've got one or two home made cam clamps that do the same thing. If so, I think the fit of the pins that ride up and down the bar needs to be more snug. The slot itself can have a loose fit, but the pins need to bear against the edge of the bar without the head pivoting up. The problem with roughing up the edges of the bar is that you're loosening the fit at the same time. Do you have pins or rivets that bear against the bar when the cam is thrown? If so, they are probably worn or bent, or perhaps not positioned close enough to the bar. You can consider driving those out, plugging the holes and then re-drilling and inserting new pins for a better fit. Or, if you have room, drilling for a supplemental set of pins that ride closer to the bar. Pictures work better for me. In this schematic, the black dots represent pins as they SHOULD be positioned relative to the bar. On my two slipping clamps, the pins have become bent and loose. Check for this on your clamps.

Whoops...let me clarify...When I pull the cam over...it is not as snug as it used to be.
The cam moves backward some..after I pull it over.. the wood on wood area is slippery, no bite.. It is not slipping at the bar

Richard, if your jaws are slipping on the surface to be clamped, try gluing some cork pads on them. You can buy rolled cork gasket material at most hardware stores or in hobby shops. If the cam itself is slipping, it's probably worn. You could easily make a new cam.

Thank you...

I'd try some fiddle bow resin.

Pat

_________________
formerly known around here as burbank
_________________

http://www.patfosterguitars.com

Some excellent tips, definitely a borrower ty.

Steve

Pat...
You got me thinking !! Create friction..How? Wet the wood.
I took a Q tip and wet both surfaces with water. Water probably swelled both wood surfaces somewhat also..Bingo..it's tight now.
Works for now..we'll see in the long run...thanks guys...