So I’ve been using the Park PRS-4W-2 for a few years now and find that I need to fix it or get something different. I can’t get it to stop losing it’s grip on the tubes and it’s constantly slipping.
What is everyone else using? Is there a hack to keep the grippers from slipping all the time? It’s a huge pain.
I weld by keeping some tube blocks on the frame and clamping on them/the bottom bracket faces/etc with a spare vise I can slide around on my bench. Probably not the most elegant or fastest solution but it’s working so far!
I have the same clamp. You could try using something with a little less grip, like a rag or some leather, in between the jaws and the frame tube and then increase the pressure a tiny bit. Somewhere between too loose and too firm you should be able to find a happy place. I’ve seen some setups where the rubber pads have been replaced with thick leather. I’ve not gone that far, but it probably works great.
I made leather jaws. They won’t work on 7/8” tube as built, but probably would fit with a second piece of leather stacked. I need to make new ones, they are burnt up now.
The clamp you mentioned has a smaller jaw, but the plastic jaw covers are the same material and the attachment method is the same.
I made leather jaws because I noticed that they got soft and slippery when hot, allowing the frame to turn in annoying ways, just before I melted them…
Someone mentioned using a tube block as a heat sink to protect the plastic jaws and that is definitely helpful, but leather jaws work really well for frames and they still hold the frame in place, even when they are on fire!
I just wrap leather around the tube and then clamp the park jaws over it rather than gluing it to the jaws or anything. My jaws are also bare as the rubber inserts have long ago given up the ghost
Feedback Sports Sport Mechanics Stand, operating principle of clamp is to be very adjustable, no unnecessary cams or ratchets:
Sport Mechanic Bike Repair Stand - Feedback Sports
For brazing I use a spring loaded park stand clamp with thick leather instead of the plastic pads. Then I wrap scotchbrite around the tube as it provides friction but also allows it to spin. The leather deals with heat pretty well. I have considered making a clamp but it’s in the middle of the project list - around 70th position on the list.
I used screws with modified heads to do the same thing. That’s a clever little holder for the leather.
Thanks all. I think I need to get some leather and possible a wider clamp. I’m super tired of the frame rotating as I’m brazing.
Here’s what I’m using.
You may be able to find scraps at a local shop that makes leather goods.