andrewmcleod
Well-known member
If there was an award for most niche equipment question, I suspect this would be in the running...
What is the best tubing for blowing out 8mm drill holes? Ideally I guess you want something thin-walled with roughly the same surface area inside the hole and between the tube and the drill hole. In any event it is going to be much harder to blow down than a larger bit of tubing (which won't fit in an 8mm hole). If you were going to massively overengineer it, you could put a short 4mm (or whatever) stub on a bit of larger tubing...
PS there are a set of nice Raumer double expansion bolts in a cave I have bolted (abroad) where the holes weren't blown out. The bolts that weren't blown out have all crept out significantly further before biting (and violated the Raumer 'good bolt' criteria) so it does make a difference!
What is the best tubing for blowing out 8mm drill holes? Ideally I guess you want something thin-walled with roughly the same surface area inside the hole and between the tube and the drill hole. In any event it is going to be much harder to blow down than a larger bit of tubing (which won't fit in an 8mm hole). If you were going to massively overengineer it, you could put a short 4mm (or whatever) stub on a bit of larger tubing...
PS there are a set of nice Raumer double expansion bolts in a cave I have bolted (abroad) where the holes weren't blown out. The bolts that weren't blown out have all crept out significantly further before biting (and violated the Raumer 'good bolt' criteria) so it does make a difference!