You need the sharp edge along the Circumference to dig into the pipe. You might be able to touch it up by grinding a little bit away where the plate touches the pipe but that may prevent other plates from grabbing unless they all have been touched up equally. Better to buy a new clamp.
If I use your approach, I can at least try to sharpen the rings...Based on the theory you can't break something that is already broken. Apparently Pony/Jorgensen went out of business. Not going to be a source of repair parts or new clamps.
I can't say anything good about pipe clamps. They are heavy, they flex in panel gluing, they are hard to adjust, the don't grab will, you have to worry about iron stain. The aluminum bar clamps sold by Lee Valley and others are the best all around clamp available. The do panel glue up and for case assembly the light weight is a huge advantage. They adjust quickly both the bar stops and threads which can be spun by figure flicking. It is handy to go to the clamp rack and be able to grab 3 or 4 of them at a time.
the butterfly/wing nut handles? It looks like those are by Dubuque, made in the USA and they get good reviews. Are those handles too small? Does not look like much leverage.
I have sanded the pipe with coarse paper and had some improvement. It might buy you some time while you're searching for a long term solution. A rack of new bar clamps sounds nice, but you would probably have to lie to your wife to get them.
"lie to your wife to get them. " Who ever else has to sign off on capital shop purchases just needs to see clamps in use leading to a flow of finished projects from shop to service, or sales.
Woodworking is one of the few hobbies that can make money, either by selling product, or making/fixing as an alternative to buying with after tax dollars. A well made and useful piece of furniture becomes an alternative to purchase going forward for generations.
Woodworking is one of the few hobbies that does in fact produce useful items and financial gain.
Compared to fishing, one of my earlier hobbies ~ purchase of boats, motors, tackle, probably compares in dollars spent, I imagine the return in actual value would be somewhere around $150 / a pound for the fish we ate.
Others play golf, fairly expensive hobby with, other than exercise, zero return.
Sure I have invested several thousand in my shop and equipment, but son and I have produced several pieces of furniture, build all his cabinets, made all the baseboard, window trim and crown molding for an entire house. Probably close to 1/2 my investment and I still own all the investment and purchase very little now.
"Others play golf, fairly expensive hobby with, other than exercise, zero return."
Any activity with exercise has a valuable return of good health. Any activity that takes your mind away from worrisome thoughts has a valuable return of reduced stress.