At an area near me there are lots of old 1/2" drop in anchors. I think they are the self drilling type, something like what Petzl sells for caving. I'd like to rebolt a couple routes that currently have the original drop ins. I would like to reuse the holes if I'm able to get them out. Has anyone had success removing them, and if so, how?
Somewhere I read you can put a couple ball bearings in the sleeve, and tighten a bolt on top, forcing the sleeve out of the rock while pushing on the cone in the back, adding more ball bearings if you run out of travel. Has anyone used this method? How likely do you think this is to blow out the hole to an unusable extent? The rock is a super crumbly conglomerate.
I've pulled some of the 8mm (12mm hole) and 10mm (14mm hole) self drills in schist and granite. I've had like 50/50 luck getting them out in one piece. I've tried using the ball-bearing method and using a hydraulic punch driver. Both work about the same 50/50. Most of the time I've snapped the sleeve in the removal process. Biggest problem with the larger models is you're pretty limited on what you can use to re-use the hole because it's 14mm (1/2 is like 12.7mm or something). Basically a beefy glue-in is your only option. Shoot me a PM if you want to discuss this more.