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Greg Barnes
climber
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Steve, aside from the obvious problem of 1/4" wedge bolts being non-removable (they will break off in the hole) - which by itself means that anyone hand drilling on lead and going back to replace wouldn't ever use them - why do you assert that they would be better?
Powers data for 1/4" Drives (split-shaft buttonheads) - ultimate load:
shear - 2090
tension - 1760
And for 1/4" Power-studs - same for carbon steel or stainless:
shear - 1620
tension - 1740
Especially considering that shear is what matters for climbing use when hand drilling on slab...
If it's because that type of steel (heat treated AISI 1018 steel) is likely to fracture, then I can believe you considering that one of Mineral's bolts just fell out due to a fracture, but on the other hand how many were placed over how many years with few cases of that?
Regardless, no one wants to be leaving 1/4" stud bolts broken off in the hole...much better to consider something else entirely like the Hilti Coil bolts (say...Norman or Brian B....did you ever funk test those suckers up in Tuolumne this year?). 1/4" Hilti Coil bolts are rated (assuming 1" embedment):
shear - 2625
tension - 2460
although 3/4" embedment:
shear - 1610
tension - 1595
Hilti coils: http://www.us.hilti.com/holus/modules/prcat/prca_navigation.jsp?OID=-12371
I'm interested in your take on all this - especially since I use 1/4" buttonheads a lot, and I have a growing list of ones that I haven't gotten back to replace (naughty me...kind of hard to find the time right now though...).
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Greg Barnes
climber
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Forgot to mention - the Drives are only made in carbon steel, stainless would be too soft. The bent-shaft 1/4" Spike bolts are available in stainless, but are SUPER weak - Minerals funk tested them and they pulled like butter.
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Steve Grossman
Trad climber
Seattle, WA
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I have written extensively on this forum about my concern with split shafts. The problem is stress fracturing due to hydrogen embrittlement and other factors where the metal is tortured (stressed) twice at the split. The test data for nice new bolts is not the issue.
I have been drilling 3/8" X 2 1/2" or deeper holes for decades. It just takes committment and practice to do it properly the first time. If the issue is really finding some way to drill small on the FA and then come back and pluck and redrill to finish the route then here are some thoughts.
The only parts of the tiny collar that actually contacts stone are the two bumps. If you alternate applying outward pressure short of breaking the shaft with the occasional inward blow to wear those two bumps down the bolt will come out intact. If you have ever had to remove blue Powers 5 piece bolts when grit has caused the cone to lock up then you have to do the same thing if you want to get the entire bolt out in one piece. Overdrill the hole a bit so that the broken fragment can be pushed past the collar and retrieved with a magnet (if mild steel) or drilled out. Very worst case, a second hole would be needed.
The inability of that collar to bite under tension especially in soft rock, a sloppy hole or under constant cycles of loading in an overhanging installation concerns me deeply. Equally, the cross sectional twist shearing that acts on the body of the bolt during the threading process stresses the metal exactly where the load is applied by the bolt hanger and where the cross sectional area is reduced especially in a bolt 3/8" diameter or smaller. A 3/8" shaft is actuall 5/16" in the threaded area.
Most of the bolts that we are using are not designed for climbing. The manufacturers don't want anything to do with us as a group. Unfortunately, bolts that are designed for the kinds of service loads that we are imposing on them are necessarily big ones.
I used to be the board chair of the Climbing Wall Industry Group while that organization existed and a 3/8" grade 5 bolt barely pencils out as adequate for stopping repeated hard falls on artificial climbing walls!
For a temporary bolt, a 5/16" Taperbolt ala JB would be better.
The word needs to get out to stop using split shaft bolts if they are going to be left behind. That is my main point. If you don't believe me then perhaps Ed Leeper's opinion will sway you. He wrote an article way back against their use. Unfortunately, I never saw that article until recently and have placed lots of the little timebombs. The light came on for me while I was rappeling down the Nose and came across a lone split shaft stud. It served no purpose that I could determine so I decided to chop it so that it wouldn't rip open somebody's haulbag. One blow up and one blow down and it sailed off into the air. I looked at the remaining portion of the bolt in the hole and almost all of it was covered in rust right at the split point where the bolt had sheared. My heart sank because I had totally wasted my time and energy believing that I was placing big bomber bolts when they are crap.
Ask yourself honestly, if you are really going to pluck and redrill properly with all fat stainless bolts immediately.....or not?
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Greg Barnes
climber
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Hey Steve,
I'm talking bomber granite only, typically low angle to vertical. And yes, I replace 90% of mine with stainless 5-piece, often the same day the 1/4" went in. And I lead with a 3/8" drill and a 1/4" drill, so from good stances (or hooks) I drill 3/8".
But I do have to admit that I sometimes take a bit to get back to some that are a pain. Actually I just checked and my list has 63 quarter-inchers that I haven't replaced, but the majority are on extremely obscure (no info anywhere) stuff, and most of the ones left on routes that people do are very low fall factor locations (I try to replace higher fall factor locations first).
I checked the Hilti info and the 1/4" coils are case hardened AISI 1018.
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Tom
Big Wall climber
San Luis Obispo CA
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Nov 13, 2009 - 04:55am PT
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Just an idea about using 304 stainless hangers on plain steel rivets:
If you heat 304 with a torch, the chromium combines with carbon as carbides, reducing the oxidation resistance. What's left at the heat-affected zone is a metal more like a 4130. It will get surface rust, but won't go cancerous like a plain steel.
If just the holes in stainless hangers were heated with a torch to create a heat-affected zone, the carbides would precipitate there, at the point of contact with the rivet. The galvanic reaction there would be reduced, but the rest of the hanger would be the original, cold-worked 304 stainless.
On the other hand, who leaves their hangers on the rivets long enough for galvanic corrosion to take place? Chongo, on his legendary Sea of Dreams ascent?
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