Pitlamp
Well-known member
mikem said:
Yes, the self drilling anchor (of which one brand was named as "Spit") requires a 12 mm hole but the bolt which is then screwed in is 8 mm.
Langcliffe's comments about Parba bolts are right.
Interesting comment about the snap off variety - they had a slightly conical extension which was an interference fit in a hole at the end of the main drilling tool. Once the anchor was drilled down as far as a circular groove in the anchor (forming a weak spot), then set by hammering down onto the conical wedge, you knocked the tool sideways and the cone shaped end separated, leaving the anchor ready to screw in the bolt and hanger. You then had to drift out the snapped off part with a separate tool before the drilling tool could be used again to insert the next bolt.
Because these anchors were designed to be snapped off they were made of a rather brittle type of steel. As a result they were notoriously unreliable and sometimes the anchor itself would snap, leading to failure. I once took a big whipper (mid 70s) when leading an aid route in Alum Pot, which eventually led to the discovery of Matthew Coe Chamber and Skyhook Inlet. (The shower of drips from this inlet is the one falling in the area of the Greasy Slab pitch in the open shaft.)
The quarter inch threaded snap off anchors in question had been given to me by Rob Palmer, having come from some dubious source; no CE marks in those days. I fell about 8 m, being stopped by the climbing rope 50 cm above a large pointed boulder. The lifeliner was Gordon Kaye, who was a big lad and I fortunately hadn't managed to pull him up into the air, or I'd have broken my back on said boulder. I seem to remember buying him a pint or two that night.
Purely in an attempt to avoid confusion, there was also an anchor available in the 70s called a "Red Head". (I think these may have been made by Hilti?) From memory they accepted a larger bolt (probably 10 mm) so weren't used a great deal by cavers for lightweight applications. Even less certain memory suggests to me the name came from the conical wedge being captive in the end of the anchor and painted red and that these weren't self drillers; you had to drill the hole by some other means.
The name "self drilling" was a bit of a sick joke; these anchors needed a lot of hammering. When climbing avens you had to have both arms above your head to work whilst stood precariously in etriers and it could be very tiring during a long session. In the days before the first cordless drill appeared (mid 80s, Bosch 24VRE) which revolutionised aid climbing, we were hand bolting our way up the massive avens in Peak Cavern's Far Sump Extension. (This was long before the dry way in was established; the only access was by a dive almost a quarter of a mile long.) I have memories of staggering out of Peak after trips lasting round the clock and beyond, with arms dragging along the floor like some exhausted gorilla.
Happy days . . . .
Going back even further, does anyone remember spending hours (literally) with a lump hammer and a fat star drill, making the large hole needed for a three quarter inch diameter (or even one inch) Rawlbolt? You might literally devote a whole trip just to inserting one belay at a pitch head. The person who invented the cordless drill deserves an O.B.E. as far as I'm concerned!
