Replies

1. 
   flairwoodworks | Jul 30, 2010 10:08pm | #1

   Durability?

   If the clamps are slippng, I would guess that either the male or female threads are partially/fully stripped.  Probably female.  This is based on my experience with threads in general, not with clamps.  To restore them... I doubt epoxy would be durable enough.  You'd probably have to get the part replaced/re-machined.

   Or did you mean that the clutch plates are slipping?  If so, does it make a difference if you hold the quick release lever outwards?

   I've been using my Jet parallel bar clamps for about half a year and love them.  I'm wondering if something happened that caused them to start slipping, like dropping the clamp or overtightening it, etc.  I haven't had any issues so far and am hoping that I never have any.  It's good to know that Jet will honour their warranty.

1. 
   VAM | Aug 01, 2010 05:02pm | #2

   Good suggestion

   It's the clutch plates.  I'll try pushing the quick release lever outward to see if they work that way - although that's awkward.  The clamps have not been dropped - by me.  No telling what happened during shipping.  I hope overtightening is not the problem.  I tighten them as much as I need for any given job. 

   One clamp slipped when I first got it and the other started about three and a half years after I got it.  I have around twenty of them all together.

1. 
   flairwoodworks | Aug 01, 2010 11:58pm | #3

   Possible to overtighten by hand?

   I use my Jets in most of my big glue-ups.  And in most cases, I'm cranking them for all they're worth with my dominant hand.  I don't know if you could overtighten them with two hands, but suspect you could with a wrench or other tool to increase leverage.  Regardless, I don't think that would cause the clutch plates to slip.

   Trying to think this through logically, only a few things could cause the clutch plates to not grip fully - either a weak/missing/broken spring that engages them, or nothing on the bar for the clutch plates to bite into.   But the Jet bars (at least mine) are serrated.  I've heard of this problem with pipe clamps, and I think I heard the solution was to "sharpen" the clutch plates.  Emphasis on "think".

   If you can make them work while holding the quick release lever outwards, I'd have a close look at the spring.  Why not ask Jet?  I'm sure they have the answer.

1. 
   VAM | Aug 02, 2010 12:41pm | #4

   Calling Jet

   Jet tech support was the first call I made.  They offer no parts for these clamps and had no suggestions for repair.  It's also not obvious how to disassemble the clamps to look inside.  So Jet just replaced the clamps.

   That's great.  But it still goes against the grain to simply throw them out.

   Chris's suggestion works.  If you press the quick-release lever opposite to how you press it to release the clamps then they can be made to tighten.  Unfortunately that means to tighten the clamp you need to have both hands on the clamp, instead of having one hand free for the work.

   I use one hand to tighten, normally.  Have never tried using another tool to increase leverage. 

1. 
   roc | Aug 03, 2010 12:39am | #5

   Glue in the plates? Worth a look.

    I have a couple of these, I bought a few of each style/brand of clamp I could get my hands on for research,  I have had no problems with slipping but have used the Jets only lightly. I did have a clamp out of four Jets that would not travel without hanging up rather badly.  I rebuilt mine to fix that problem.

   I have yet to find a clamp I am totally happy with.  A bit of candle wax rubbed on the threads now and again should make a clamp of this high quality last a life time.

   Most of the clamps with plates can slip if glue gets in there and dries and keeps them from moving as designed.  Maybe clean out with . . .

   What ?

   Vinegar ?  Depends on the glue.

   PS: to look inside pull the bar all the way out of the clamp head.  Look in from under side of clamp.

   PPS: I just went and pulled mine apart.  Take out little black screws on sides, remove metal structure with rocking black part from plastic through the bottom opening.  Then can use screw driver to remove cover from black part to get at inner clamping plates.  Not that you are going to replace them but maybe chip the glue off the plates, wax them and reassemble.

    PPPS:  If no glue perhaps you can flip the plates over to use a fresh edge in the hole in the plates.  I don't know; I didn't take them that far apart this time and don't remember if these plates are symmetrical.

2. 
   VAM | Aug 07, 2010 04:39pm | #6

   Thanks everyone

   I appreciate all the advice.  If you disassemble your clamps as Roc mentioned, be careful.  The small black screws need to be loosened with a hex key.  The screw heads are soft plastic and have been well-tightened by Jet.  Be sure your key fits very tightly so you don't strip the screw heads.