Five years ago I bought a dozen of these from Amazon.  This brand was subsequently top-rated by FWW.  Over time three of the twenty-four inchers started slipping when tightened, making them unusable.  I called a couple of years ago to ask about a fix and Jet said they’d simply replace them since they have a lifetime warranty.

Recently I called again with the same problem on more of the clamps.  This time Jet (Walter Meier) said I’d have to go through Amazon.  Amazon refused and said I had to go through Jet.

Finally I found someone at Jet who didn’t replace them but did know how to fix them.  Instructions follow if you need to save a couple of hours on the phone.

On the sliding jaw there is a cover held down by four Phillips head screws.  Remove these.  Each screw has a regular and a lock washer so don’t lose those.  Below the cover is a spring so be ready as you remove the last screw.  Set aside the cover and remove the spring.  Below the spring is a metal plate.  Take the plate out and flip it over – not top to bottom but front to back.  Reinstall the plate, spring, cover and screws.  It’s hard to say why this works.  The plate has very, very slightly rounded edges as installed by Jet and flat edges after you flip it.  Hopefully, this will be a long-term solution.