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: www.safeclimbing.org/education/SoftRockBolting.pdf 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.