Sheared bolts

I recently went up to see what was up with anchor bolts on Midget Magic, a 5.8 at hairpin turn on Mt. Lemon, AZ. I had been told that one of the bolts was missing and that there was just the one bolt for the anchor. Since I put this route up less than a year ago I thought this rather strange. The holes were drilled to 3 inches with a Bosch and adequately tightened. 2 days ago I climbed it and what I found was disconcerting. One bolt was sheared off about half way into the bolt hole, and the exposed end appeared rust colored. The bolt was 2.5"x3/8" stainless sleeve type bolt. The other bolt was fine. This is the same kind that are all over the mountain and that many of us have fallen on many times.

This bolt was at the anchor and should never have been subjected to any sort of dynamic load. I looked for signs of rock fall but did not see any. I added another bolt so that the anchor has 2 bolts with chain. Any theories as to what might have happened. I speculate either rock fall or defective bolt.

What type of bolt hanger?

It does sound unusual, especially since it isn't sheared flush with the rock face.

Not trying to question your ability at all, but are you an experienced bolter?

Don't really got any answers for you, but maybe pictures would help. I'd say it requires careful evaluation of every bolt on the route.

Happy xmas
Evan

A year later, and the anchor fails. This is why I have a hard time clipping bolts, you never know who placed them.

If rockfall had caused it, you would have seen a leftover scar.
If a shock load (fall) had caused it, we all would have heard about it.
That leaves over-torquing. A bit odd your stainless bolt is rusting though...

The fact that the bolt broke half way into the hole suggests that it was a tensile failure not a shear failure. It was probably not from rockfall which would likely shear the bolt off at the rock face. A more likely cause is that the bolt failed in tension from being over torqued. The fact that there was rust at the failure point indicates that the break was not fresh; and this is consistent with the bolt being over torqued a year ago when placed. I suggest reviewing the manufacturer’s bolt torque recommendations and then consider how much you applied when placing it. Applying a large torque is actually one method of removing a bolt, or at least the outer portions of a bolt, and it takes less torque than one would expect.

If you really want to know if the bolt was defective or not, remove the section still in the rock and take it to a metallurgist. I expect that defects or substandard material would be evident to a trained person with the right equipment.

Appreciate all the comments. Just an FYI the bolt is a wedge type, not the 5 piece rawl style.

my vote is that clibmbaja is on the right track. it's pretty easy to snap an SS 3/8 wihthout throwing that much coal at it.

Chris Craig wrote:I recently went up to see what was up with anchor bolts on Midget Magic, a 5.8 at hairpin turn on Mt. Lemon, AZ. I had been told that one of the bolts was missing and that there was just the one bolt for the anchor. Since I put this route up less than a year ago I thought this rather strange. The holes were drilled to 3 inches with a Bosch and adequately tightened. 2 days ago I climbed it and what I found was disconcerting. One bolt was sheared off about half way into the bolt hole, and the exposed end appeared rust colored. The bolt was 2.5"x3/8" stainless sleeve type bolt. The other bolt was fine. This is the same kind that are all over the mountain and that many of us have fallen on many times. This bolt was at the anchor and should never have been subjected to any sort of dynamic load. I looked for signs of rock fall but did not see any. I added another bolt so that the anchor has 2 bolts with chain. Any theories as to what might have happened. I speculate either rock fall or defective bolt.

I hate to ream on yea, but I have never heard of 2.5 in bolts for anchors. Most that I have seen are 1/2 by 3.75-4.75 inches deep. How about you beef up those wimpy bolts.
In AZ you might be bolting up sand stone as well 150 mm glue-ins are a good choice too.

Jeff J wrote: I hate to ream on yea, but I have never heard of 2.5 in bolts for anchors. Most that I have seen are 1/2 by 3.75-4.75 inches deep. How about you beef up those wimpy bolts. In AZ you might be bolting up sand stone as well 150 mm glue-ins are a good choice too.

In good granite, a properly placed 3/8" x 2.25" is going to be bomber, especially for an anchor, for many years to come. There is no need to use 1/2" bolts and in lengths such as 3.75-4.75" in granite. That is total overkill.

ClimbBaja wrote:The bolt snapped, probably somewhere between 25 and 35 ft-lbs.

Absolutely not. I have replaced hundreds of 3/8" SS Power-Bolts at my local crag. Overtime the cone becomes so rusted from marine corrosion that the bolt will often shear off at the threads while I attempt to remove it. Well I have to use a 1/2" x 18" breaker bar to get the bolts to even turn, it often takes over 100 in. /lbs of torque to even get them turning. They don’t generally snap until over 120 in./ lbs. It takes more effort for me to turn the breaker bar on the bolts then it does to turn the exact same breaker bar to loosen my lug nuts on my car (which are tightened with a 1/2" pneumatic impact).