Thanks guys! Any luck with removing those mammut ring bolts (besides using a dremmel)?
Yes. You are left with a shallow 5/8" hole. The next bolt would need to be a glue-in and not a mechanical bolt. We still have some questions about whether our method pulverizes/weakens the rock at the lip. We are still refining the method before using it on a route. Here is the jig we tested successfully in February along with some early failed experiments in core drilling around stud bolts:
Interesting video on the ring bolts. Luckily there's not too many of those around to worry about. Coming from a guy who has no experience with glue in's; In theory would the glue solve the issues of weakened rock (unless of course it was a large fracture internally).
Thanks again for researching these methods and putting them to use. It's awesome to think that same hole replacements aren't limited to triplex and 5 piece bolts.
...In theory would the glue solve the issues of weakened rock (unless of course it was a large fracture internally)...
I have no experimental data to go on, but my guess would be 'no'. I suspect you could get a failure like the soft rock crushing situation on page 4: safeclimbing.org/education/Sof... The hydraulic punch driver can press against the rock with several thousand pounds of force. The ring bolts are beefy enough to sometimes hold until the ring flattens and breaks - that's a scary huge load. The 3/8" studs have all slipped out or snapped off at much lower forces.