Thoughts on 5/16" (8mm) wedge anchors

hey there mad bolters...

Heard about a hand-drilled new route project...

How do you all feel about 8mm SS wedge anchors (tested to 22-24kn) for lead bolt and anchors? In quality granite.

Asking for a friend. :)

I'd whip 

an 8mm bolt seems to be the sweet spot for hand drilling.   Significantly faster than both 1/4" and 3/8", I can't explain it, I believe its been attributed to flexing in a 1/4" drill bit.    Raumer 8mm bolts are weird and don't want to tighten up in granite, the Lappas from HowNot2 seem much better.   BITD there was 5/16 5-piece bolt but they stopped making them along with 5/16 buttionheads which apparently are near impossible to remove?   IMO plenty good for adventure climbing.

Darin, I’m curious about testing out those 8 mm bolts. What length do you normally buy for hand drilling? I’m mostly putting bolts in compact gneiss.   I’m guessing 3”? If so, does a 3” 8mm drill faster than an 3/8” 2.25”? Also want to confirm that I should be using an 8 mm bit rather than the slightly more easily accessible 5/16”. 

I would drill the 2 1/4" (60mm) versions for my friend's *cough cough* purposes. I haven't seen testing that they are anything less strong in shear or tension if the rock is of sufficient quality. As I understand it, the depth is considered sufficient to withstand crushing of the rock around the hole.

Happy to be educated by anyone that knows better.   

C'mon, it's not that much more effort to hand drill 3/8".  If stances are thin, drill 1/4" x 1.25" deep for temp bolt and go back after the FA and replace with SS.  Yes, 8mm SS is adequate, but why not have a little extra metal for peace of mind or to compensate for the occasional bolts that might have a material quality issue?

bob steedwrote:

C'mon, it's not that much more effort to hand drill 3/8".  If stances are thin, drill 1/4" x 1.25" deep for temp bolt and go back after the FA and replace with SS.  Yes, 8mm SS is adequate, but why not have a little extra metal for peace of mind or to compensate for the occasional bolts that might have a material quality issue?

Have you tried it, Bob?

5/16" are literally half the time of a 3/8". Maybe you just need to come drill with me and Clint. 

I'm sure we'll let you drill as much as you want. :)

John, you seem like the type who wants a real answer. I agree with Bob completely.

One other factor that I think matters: how the bolts LOOK. As an example, I have a friend who was using an extremely strong specialty chain on anchors. But it looked tiny (even though it was rated  to something like 6,000 pounds). Other climbers couldn't know if something was adequate (his was more than adequate) because it looked inadequate.

One of these days, I'll make it out there with you guys.  My main point is not about the speed, but about leaving a little bit more metal in that hole for long term peace of mind.  And I do think you could drill a 1/4" x1.25" hole faster than a 8mm x 2.25" hole.  On the rare occasions when I drill 1/4" I use a shorty 1/4" bit, so maybe that helps reduce the flex issue?  Tell you what, let's set up a real world experiment while bolting on lead at good stances with the same person person swinging the hammer and determine minutes per inch of depth drilled or some such thing.  I do think that 8mm would be good for deep backcountry exploring since the lighter bolts + hangers (vs. 3/8) would need to be humped many miles and many thousands of feet of vert.

John- I'll hand drill your front country bolts for you at 3/8"  But I charge one beer per bolt.  Payable at time of installation, so I'll bring a tag like with me to collect payment.  

Bryan Law would get 1/4" x 1.5" bolts drilled in sub-90 seconds with a 17/64" HSS bit (can't use 1/4" HSS since the hole is too tight). And he wouldn't use the 1/4" x 1.25" length buttonhead which would have been even faster!

Think my best time with an HSS bit was over 2 minutes, and I always drilled 1.25". But I didn't get as much practice since I'd use 3/8" when the stance was good, and I went for good stances. And I usually used SDS, only got introduced to HSS bits pretty late.

Never had any flexing with a 1/4" bit, but never tried any 1/4" bit longer than 2" (4" total).

John Tuttlewrote:

I would drill the 2 1/4" (60mm) versions for my friend's *cough cough* purposes. I haven't seen testing that they are anything less strong in shear or tension if the rock is of sufficient quality. As I understand it, the depth is considered sufficient to withstand crushing of the rock around the hole.

Happy to be educated by anyone that knows better.   

I don't really know better as far as numbers or testing go, but do have relevant anecdotal experience.  I took a 60' fall when an SS wedge bolt of roughly exactly those dimensions pulled out in what should've been a 15-20' lead fall.  Thankfully it was into clean space and the rusty old pin above the belay picked up the slack.  The rock was bullet Yosemite granite.  To be clear, it didn't break, but entirely pulled out of the hole and was dangling from the hanger when I came to a stop well below the belay.

Buy a few petzl 8mm removable bolts. Hand drill to 2.25 in depth.  You only need 1 3/4' for the petzl but it would make drilling the 3/8 easier. Send. Then upgrade to 3/8 stainless on the way down. 

You will feel better about yourself equiping your climb with bomber long lasting hardware. It has been a pain for me to go back and upgrade my hand-drilled stuff but i am glad i did.

If Hilti made a 316 KB3 in 8mm i think this would be a different discussion but alas...

timothy fisherwrote:

Buy a few petzl 8mm removable bolts. Hand drill to 2.25 in depth.  You only need 1 3/4' for the petzl but it would make drilling the 3/8 easier. Send. Then upgrade to 3/8 stainless on the way down. 

You will feel better about yourself equiping your climb with bomber long lasting hardware. It has been a pain for me to go back and upgrade my hand-drilled stuff but i am glad i did.

If Hilti made a 316 KB3 in 8mm i think this would be a different discussion but alas...

I'd be using the Lappas 8mm double wedge. I don't have concerns about quality there. Saving half the time hand drilling on multiple pitch routes is a major factor.

bob steedwrote:

John- I'll hand drill your front country bolts for you at 3/8"  But I charge one beer per bolt.  Payable at time of installation, so I'll bring a tag like with me to collect payment.  

We'll work it out, Bob. I got a couple of multipitch projects in mind.

bob steedwrote:

C'mon, it's not that much more effort to hand drill 3/8".  If stances are thin, drill 1/4" x 1.25" deep for temp bolt and go back after the FA and replace with SS.  Yes, 8mm SS is adequate, but why not have a little extra metal for peace of mind or to compensate for the occasional bolts that might have a material quality issue?

From personal experience I’m gonna say a 3/8 is significantly more effort.  Like at least double maybe triple.  An 8mm seems to be about 30-50% quicker than 1/4.  8mm x 60mm is plenty strong in hard rock.   Have only used in very remote locations.

Max Tepferwrote:

I don't really know better as far as numbers or testing go, but do have relevant anecdotal experience.  I took a 60' fall when an SS wedge bolt of roughly exactly those dimensions pulled out in what should've been a 15-20' lead fall.  Thankfully it was into clean space and the rusty old pin above the belay picked up the slack.  The rock was bullet Yosemite granite.  To be clear, it didn't break, but entirely pulled out of the hole and was dangling from the hanger when I came to a stop well below the belay.

HowNot2 needs to do some testing, particularly considering they're the easiest source for this.   I had purchased some raumer bolts initially but threw them all away when I concluded that they struggled to tighten in a hand drilled 8mm hole.   The lappas seem much better.

8mm stainless bolts don't make the standard, it's simple.

Jim Tittwrote:

8mm stainless bolts don't make the standard, it's simple.

Understood, Jim. And I give great weight to your input.

Thank you.

Jim Tittwrote:

8mm stainless bolts don't make the standard, it's simple.

Hi Jim.

I came across the UIAA specifications for Rock Anchors (UIAA Safety Standard– 123– Version 5.0) section 4.3.1(b) which stated the following:

"(b) Axial load-bearing capacity: When tested in accordance with 5.2, all types of rock-anchors shall withstand an axial load of at least 20kN without breaking."

If 8mm wedge anchors are tested in shear and tension and fail at 22-24kn would they be in compliance with the standard? Is there some "margin" in excess of the standard that is considered ideal/common practice? While I am in complete agreement that 3/8" or even better, 10mm, wedge anchors are preferable long term, is 8mm entirely inadequate for large hand drilled projects?

This is leaving aside of course that the 8mm anchors (Lappas) may have never been submitted for EN 959: 2018 certification afaik.

It's the radial test at 25kN they don't make, an 8mm M8 316 bolt won't. There's no tolerance (apart from the testing gear), it's a minimum value.