This is normal if the clamping elements are exerting too much pressure. The faces cannot go down (into the MFT) so they push the timber up.

I suggest you do not tighten the clamping elements all the way, or loosen their maximum pressure setting by rotating the cams inside.

I believe what Richard is referring to is how close to the material you set the pressure pad on the moveable element and how far you stroke the handle. Both determine the applied pressure of the clamp.

The elements come with knobs to secure them in the MFT. There use will eliminate the problem also.

Tom

Richard,

I know about the clutch plate adjustment screw on the clamping elements. It just so happens Peter and I were in the same class.

The clutch adjusting screw does nothing for clamping pressure applied to the pieces being clamped. It only affects the clutch pressure against the arm of the element. When you apply clamping pressure with the lever, the clutch plates prevent the arm for retracting against the pressure. That is why when there are complaints about nicks in the arm, you adjust the screw.

One other thing to help prevent lifting, the shorter the arm is out of the element body, the less lifting there will be.

Tom

I'm annoyed about this thing, every time i have to use it.
It regularly lifts my workpiece up to 1-2 mm  .

It seems to me that it is badly designed, but has a fairly high price .

This is a situation where less is more.

You only need enough pressure to prevent the piece you're working on from moving, not a death grip. There is that sweet spot, once you find it you'll always go back to it.

Part of the cost of the elements are the retaining knobs. Those few times where I did have to apply a lot of pressure to the work piece with the clamps, the knobs prevented the elements from canting.

The knobs are nice to have and use on fixtures and jigs you make.

Tom

The engineers designed the clamps to apply pressure. How much pressure is out of their control. That is determined by the user. There are times the user may need more or less pressure, depending on the task at hand. I know I apply more clamping force when I am holding a tall piece vertical than when the same piece is flat on the MFT.

They include the knobs to fight the physics of the clamp cambering. In the clamping elements over all design, the issue is addressed an corrected for, by their suppling the knob. It is up to the end user to use the tool as designed, or not.

Adjust the amount of pressure you apply, as I said, once you get it you got it, or use the knobs.

Tom

The clamping elements are miniature vices.  To eliminate lift the rods would have to be heavy steel and and ride in steel bushings.  And the dogs would have to be a much tighter fit.  And the top would have to be maple or something because MDF wouldn't hold up.  

You're looking for stationary workbench with heavy duty vice performance from a light weight portable unit with a low cost sacrificial work top.  I don't think it's going to happen.

I have found this happens when I really exert a lot of force, but generally it is not an issue.  If I do notice it, then I break out the little knobs...not as convenient if you have to use a couple of different set-ups, but the knobs do help keep everything flat to the table.

Scot