Author Topic: What throughbolt?  (Read 2855 times)

Offline aricooperdavis

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What throughbolt?
« on: November 17, 2020, 05:44:27 pm »
I'm in the market for some 8mm throughbolts. Whilst I could find some discussion of the pros and cons of throughbolts as opposed to spits/resins etc, I couldn't find much about what is expected of the throughbolt itself.

So what sort of specs should I be looking for? I get that this depends on their use case, but how should I be choosing?

For example I might use an A4 stainless bolt if I wanted a longer life, or to avoid any staining of the rock. But what sort of permissable tension/shear loads should I be looking for? Should I be looking for ICC (US) approval? How about Seismic C1 and C2 ratings?

I know that the Dachstein expedition has used Fischer FBZ II 8/10 in the past (a mixture of the stainless R variant and the non-stainless variant), but they're not easily sourced in the UK, instead they're pushing the higher spec, and higher cost, FAZs.

What is everybody else using?

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What throughbolt?
« on: November 17, 2020, 05:44:27 pm »
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Offline Fjell

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Re: What throughbolt?
« Reply #1 on: November 17, 2020, 07:20:58 pm »
The Raumer studs are not unreasonably priced, are 316/A4, and are double cone in 8 or 10mm. The shortest I would use for rigging is the 78mm 8mm one. I’m sure your friendly caving retailer would be happy with a bulk purchase as they are in stock.

They have at least made an effort to design and test something for climbing and caving for placement in rock rather than concrete, and they are heavily used for real, including being fallen on a lot by climbers (usually the 10mm).

Personally I would overdrill so they can be knocked in flush, and use thread lock for long term use with a hanger left on it (although the Raumer one has a sort of locking nut on it now).

I used to use Hilti A2, and I saw some a couple of years ago I placed nearly 30 years ago that looked like new. I am deeply unworried about the safety of these things in sound rock.

Offline Rob

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Re: What throughbolt?
« Reply #2 on: November 17, 2020, 07:33:11 pm »
For exploratory rigging I basically buy the cheapest i can on eBay.  :thumbsup:  Typically i'll buy 65mm long, or 50mm if it's specifically for a long bolt climb. If i'm getting stainless for what may become a tourist route (but yet doesn't warrant a P-Bolt quite yet) i'll get 75mm or maybe longer.

Only features i really look for (as long as not much more cost) is a top section that is not threaded. This means that the thread doesn't become broken during hammering, allowing for the hanger to be easily removed upon derigging without risking the whole bolt turning in the hole.

Also i'll try get fully threaded. This is handy if your drill battery runs out halfway down the hole but it's just about deep enough to get something in.  :thumbsup:

Both these features shown in this example:

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Re: What throughbolt?
« Reply #3 on: November 17, 2020, 10:59:44 pm »
I cut open my cordura suit and my shoulder prussicking up a tight pitch in JH that had rusty old throughbolts protruding out of the wall from the original bolt climb. Luckily I had a lump hammer on me and was able to take out my rage on the offending items, but I was bleeding for a while, a good way from home. Surely for exploratory rigging it would be better to use good-quality removeable screws and only use (stainless) throughbolts for the final anchors? Then at least it's left nice and neat for future use?

Offline nobrotson

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Re: What throughbolt?
« Reply #4 on: November 17, 2020, 11:05:33 pm »
Screwfix are my go-to for through bolts. I guess it varies slightly depending on where you are but they're usually around 20-40p per bolt for the cheapest ones. 75mm seems to be a pretty standard length. I'd agree with all of what Rob says regarding thread in best case scenario though. Also as he says depends what you want to use them for as to how fussy you get. Chunky stainless ones from inglesport are nearly 10x the cost but feel much safer to hang off especially if there will be a lot of traffic.
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Offline andrewmc

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Re: What throughbolt?
« Reply #5 on: November 17, 2020, 11:12:35 pm »
Screwfix are my go-to for through bolts. I guess it varies slightly depending on where you are but they're usually around 20-40p per bolt for the cheapest ones. 75mm seems to be a pretty standard length. I'd agree with all of what Rob says regarding thread in best case scenario though. Also as he says depends what you want to use them for as to how fussy you get. Chunky stainless ones from inglesport are nearly 10x the cost but feel much safer to hang off especially if there will be a lot of traffic.

Urgh, not Screwfix on principle :P At least with Fischer they might be crap, but they'll be _reliably_ crap :P

I think I bought a shedload of bolts from this place:
https://www.fastco.co.uk/fischer-fxa-m8-x-71mm-zinc-plated-through-bolt-article-523131-pack-of-50.html

In fact, I still have shedloads (non-stainless) so you could probably just ask me :P I've also still got some of the £2 a shot Raumer double expansion cone 316L stainless, in both 8mm and 10mm... optimism for buying bolts exceeded the opportunities to place them! (purely in Austria)

Offline Fjell

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Re: What throughbolt?
« Reply #6 on: November 18, 2020, 08:59:47 am »
I’m curious to know what you are going to do (do already) with a line of carbon steel stud bolts if you don’t over drill the holes. Knock them off with a lump hammer after? You surely can’t leave them sticking out?

There are lots of things you can just put in a blank 8mm hole these days. Screws, or the Petzl things if you are posh.

Offline MarkS

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Re: What throughbolt?
« Reply #7 on: November 18, 2020, 09:41:09 am »
Surely for exploratory rigging it would be better to use good-quality removeable screws and only use (stainless) throughbolts for the final anchors? Then at least it's left nice and neat for future use?

Couldn't agree more (other than using resin anchors for the "final" anchors in the UK). Pretty hard to justify other options in my opinion.

Offline AlexR

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Re: What throughbolt?
« Reply #8 on: November 18, 2020, 10:46:15 am »
I would not use a bolt without a European Technical Approval (ETA) or equivalent and therefore choose something like Fischer, Heco, Hilit, Petzl or Raumer. The price difference to no-name or own brand is negligible, and when I'm hanging off it I'd rather not wonder about steel quality and manufacturing tolerances.*

Personally I use Fischer FXA through bolts (8/10x71, Art. No. 523131) for bolt climbing, I also have a box of 8/30x91 (Art No. 523132) if I suspect there to be a layer of crap on top that I can't spend hours hammering away or the rock is of a generally more fragile nature. Holes are always over-drilled so I can hammer the bugger back after.
The two lengths are not based on any safety research I am aware of but purely battery life considerations and what I'm comfortable with.

I've only used self-taping concrete screws for downwards bolting in quarries (rather than caves) because opportunities to do so aren't exactly plenty full in the UK. They are certainly preferable from a conservation viewpoint; unfortunately I've found stainless steel ones to be a) difficult to come by and b) very expensive. Simon Wilson and Rolf Siegenthaler make good points for using them in their articles.
My attempts to use them for bolt climbing (Heco MMS-plus 7.5x60) have not been overly successful, even with a ratchet spanner I find it too difficult to get the screw to bite with a fully stretched out arm.
Especially for exploratory bolting I'd 100% go with self-taping concrete screws, if it ends up going somewhere the 8mm holes can easily be reused or enlarged for expansion or other anchors. This also avoids issues with badly bolted pitch heads being "ruined" by fracturing the rock with expansion bolts.


*Anecdotally, I have measured differences in OD of 0.5mm in Excalibur screwbolts. I'm no engineer, but that's way more than I'm comfortable with.

Offline Fjell

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Re: What throughbolt?
« Reply #9 on: November 18, 2020, 11:13:09 am »
Has anyone used these underground much? Not cheap, but I would think 2-3 of them would be very handy. Can they be reused indefinitely? 50mm depth.

Offline Mark Wright

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Re: What throughbolt?
« Reply #10 on: November 18, 2020, 11:48:45 am »
I’ve got 3 of the Petzl removable anchors and they are excellent for exploratory trips.

I lent them to a friend of mine a couple of weeks ago for a clandestine exploratory trip in a Derbyshire cave and they proved very effective. If it went, which it did in their case, the hole can be easily drilled out to accommodate a resin type anchor.

As to them being used indefinitely, only time will tell.

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Offline aricooperdavis

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Re: What throughbolt?
« Reply #11 on: November 18, 2020, 12:20:58 pm »
Thank you, very helpful discussion!

I'm not anti concrete screws by any means, but I don't see the division of "exploratory" vs "trade-route" as being black and white, so I think there is a middle ground use case for throughbolts between screws and resin anchors. The Dachstein is a great example - you might spend a decade exploring something only to decide it doesn't go. So whilst you could do your initial push on screws you'd want to drill them out and replace them with something sturdier before too long, and that sturdier thing could be a stainless throughbolt.

Very helpful tips re. threading; I've definitely fallen foul of throughbolts with threaded top sections that break then weld during tapping in.

Offline Badlad

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Re: What throughbolt?
« Reply #12 on: November 18, 2020, 12:34:53 pm »
I'm not much of a fan of throughbolts myself but that is a different topic.  I did notice a comment in the Mulu Caves Project equipment report earlier this year.  It stated quite firmly

Quote
Please only buy rated throughbolts from Hilti or Fischer in future

The guy who wrote it is a very experienced technical caver and a big fan of throughbolts.

Offline andrewmc

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Re: What throughbolt?
« Reply #13 on: November 18, 2020, 01:01:17 pm »
I'm not much of a fan of throughbolts myself but that is a different topic.  I did notice a comment in the Mulu Caves Project equipment report earlier this year.  It stated quite firmly

Quote
Please only buy rated throughbolts from Hilti or Fischer in future

The guy who wrote it is a very experienced technical caver and a big fan of throughbolts.

'rated' is an interesting thing... All the cheap 8mm throughbolts described so far are, as far as I know, rated for hanging things off non-cracked concrete and are not rated as caving/climbing/rope access anchors, so what does 'rated' mean here? Just has an ETA for something, regardless of what it is?

I thought the 8mm Raumers didn't either, but turns out (in combination with the Raumer ring hanger or caving maillon hanger) do pass EN959:2018 (not rated for EN959:2007; don't know if that's due to a change in standards or they just didn't certify them).

Offline Badlad

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Re: What throughbolt?
« Reply #14 on: November 18, 2020, 01:23:42 pm »
I suspect 'rated' mostly means from a known trusted supplier.  I think the issue with the Mulu equipment's stock was that some of the throughbolts were unidentifiable and of inferior quality. I'm guessing as I wasn't there for the audit but did note the comments in the report relevant to this discussion.  When you are hanging your life on an industrial fixing you do need to have some confidence in it. This is presumably one way of achieving that.

Offline MarkS

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Re: What throughbolt?
« Reply #15 on: November 18, 2020, 01:52:56 pm »
I'm not anti concrete screws by any means, but I don't see the division of "exploratory" vs "trade-route" as being black and white, so I think there is a middle ground use case for throughbolts between screws and resin anchors. The Dachstein is a great example - you might spend a decade exploring something only to decide it doesn't go. So whilst you could do your initial push on screws you'd want to drill them out and replace them with something sturdier before too long, and that sturdier thing could be a stainless throughbolt.

Fair comment. I guess I'm not a fan of throughbolts in general but as Badlad said, that's probably a different topic.

Having had issues with non-stainless throughbolts (Fischer Faz II, apparently) adhering to the nuts between trips in subsequent years, I would probably only want to use stainless ones for anything needing to last longer than concrete screws.

Offline andrewmc

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Re: What throughbolt?
« Reply #16 on: November 18, 2020, 02:08:44 pm »
Having had issues with non-stainless throughbolts (Fischer Faz II, apparently) adhering to the nuts between trips in subsequent years, I would probably only want to use stainless ones for anything needing to last longer than concrete screws.

I guess climate is an issue as well. Deep in the Dachstein, all the bolts might be damp but they are almost in a deep-freeze at a steady 2 degrees, so even decades-old bolts are not necessarily that rusty (although I'd still rather use stainless!). Whereas in the jungle, I can imagine them rusting by the end of the exped...

Offline MarkS

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Re: What throughbolt?
« Reply #17 on: November 18, 2020, 02:39:59 pm »
I guess climate is an issue as well. Deep in the Dachstein, all the bolts might be damp but they are almost in a deep-freeze at a steady 2 degrees, so even decades-old bolts are not necessarily that rusty (although I'd still rather use stainless!). Whereas in the jungle, I can imagine them rusting by the end of the exped...

I suspect you're right, but I was referring to anchors placed in cold alpine caves in Montenegro!

Offline Rob

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Re: What throughbolt?
« Reply #18 on: November 18, 2020, 07:27:06 pm »
Interesting discussion. The rating element is a poignant topic, and i think i currently sit far on one side of the scale. At risk of being eaten alive, here's my viewpoint.

An M8 bolt is a very strong item for the application we use it in, especially when generally used in shear. I don't know figures to back this up, but i'd guess a safety factor of 10 even at a low steel class, and also allowing for a reasonable dynamic loading. The axial strength of the bolt should also be exceptionally high, as a typical tightening force in normal (non-caving) operation would be far greater than that of human loading.

I can understand a risk associates with the collar which could be deemed as a mechanical part so more susceptible to material quality or design. However it is designed to fail, i.e. the collar breaks, deforms, and moulds into the cone below, so i'm not sure really how that could go wrong (in a dangerous way).

Further more, we never (if possible!) hang off one bolt, with Y-hangs to not only spread the load but also there in case of item failure. So there is safety built into the way we rig.

Yes academically unrated bolts aren't designed to hang heavy things off in a safety critical way. But neither are the handholds we rely on for every single trip, nor the robustness of the roof when moving through chokes. Caving is dangerous, especially at the pointy end, in magnitudes far far greater than using unrated M8 bolts, which incidentally i've never seen fail due to poor product quality.

However, if there was an M5 through bolt discussion....
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Offline Mr Mike

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Re: What throughbolt?
« Reply #19 on: November 19, 2020, 10:24:57 am »
I have always used Raumer SS M8 and M10 bolts - always liked the twin collars on the long ones. These have always been used in mines with solid limestone and sandstone.

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Re: What throughbolt?
« Reply #20 on: November 19, 2020, 10:46:42 am »
For me the strength of the fixings isn't the issue, but the permanence of the throughbolts. As they stress the rock when installed, that stress can never be removed again, and so that area can't realistically be used again either. Screws don't stress it, and I've even re-used a clean screwhole a year later with a different screw with no issues. Once the final route has been determined, then throughbolts are fine for installation, but it seems daft to write off whole sections of rock (and the resultant dangerous rusty stubs) just for the ease of hammering them in, especially if bolting downwards. There are probably twenty or so screws still in the shaft at Longcliffe from all the various routes we've rigged, but they're all fine, none have rusted, and they can be removed eventually with no damage to the cave. Apart from one throughbolt that I didn't install. And now it's there for ever - in the wrong place! I used stainless throughbolts to hang a water-barrel from as that's essentially a permanent feature for now, but they can be incorporated into a rope route at some point if it ever comes out.

I have done bolt-climbs with screws, and whilst the distance reached might not be quite so great as a with a throughbolt, it still works. Cleaning the holes out first is essential though, and that can also be a bit trickier going upwards, but I find a long bit of flexible 7mm hose is great for blowing it out.

Offline SamT

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Re: What throughbolt?
« Reply #21 on: November 19, 2020, 12:00:01 pm »
Re Strength...  What rob said.

Its always struck me that cavers are utterly utterly obsessed beyond belief with the strength of anchors.  Way beyond a point that's reasonable.   Its as though they're utterly convinced that on every trip, they'll be taking factor 2 falls on a single bolt that will for definite, snap in two like a crisp, sending them hurtling to their death.

If the history of caving was littered with past heroes, dead and buried from anchor failure, then I could understand this.  But it doesn't happen, it never really has.  I'm sure there are maybe some unfortunate souls out there, but I can't, off the top of my head, think of a fatality from bolt/anchor failure.

Snapped ropes, yes, hang ups, yes, etc etc.

So why the obsession.

We're pretty bloody amazing it now.  We've got incredible standards, especially compared to the climbing world, which arguably uses many many more bolts.

Back to the original topic, couple of thoughts.

All trade/tourist routes began their life as exploratory routes, so bare that in mind when exploring.

For me
- 8mm thrubolts, over drilled for bolt climbing.
-down rigging.  I've tended to use 8mm thrubolts in the past, but the screws make so much more sense.

I'm not so convinced that 8mm through bolts "stress" the rock as much as is made out, and thus I don't think great areas of rock are rendered unusable.

/2p


 

Offline Joel Corrigan

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Re: What throughbolt?
« Reply #22 on: November 20, 2020, 12:13:37 pm »
Poor Ari: he was just asking a simple question!  We kind of screwed up in the Dachstein but I guess that hindsight is a wonderful thing.  For many years, the standard routine was to find a promising cave, push it for two, three or even four years before it beat us into submission & we ran away in defeat.  Our policy was to use the cheapest thru-bolts we could afford (generally from Screwfix) as we knew with utter certainty that nobody would ever return.  With the discovery of WUG, though, this all changed & we realised that decent rock was at a premium so replacing the initial wank anchors with decent stainless wasn't always feasible.  If I could go back in time I'd insist that the project only used stainless right from the word go as we still find ourselves re-investigating abandoned sites to check for snowmelt etc...  And now we have a situation whereby one of our previous discoveries (Burnies Pot) could become the key to a higher entrance (some of our keen youngsters intercepted it from another cave & have been using the original rigging) and it fills me with dread as rescue from that place would be brutal.  If only we'd used stainless  ;) 

Few other thoughts: back in 2014 Tony Seddon & I spent a week or so in the Vercors doing the French cave rescue training course with the SSF & they disliked thru-bolts with a passion & only used Spits.  The trainers weren't too keen about going into too much detail in English as they favoured the Spanish & French speakers so we missed out on some of the detail but they certainly have plenty of reason to dislike thru-bolts.  Concrete screws weren't really popular at the time so we never had that discussion, but from my point of view I can't stand them (concrete screws, not necessarily the French!).  I find them to be time-consuming to install & remove, way too awkward to use for serious climbs, don't sit in a hanger whilst racked on your harness, holes often need boring out in hard rock, and it's quite easy to damage the flutes which means they're not necessarily that reusable.  For the UK I can certainly see their place but I don't get how deep Alpine projects like them as speed is of the essence.  And Andrew: we were only using the Fischer ones because we got a deal & not because they were necessarily better than others. 

Top of my hate list, though, are those daft anchors that require a setting tool (I think the Oxford lot use them in the Picos?).  Ian Holmes told me about a few that popped out because they hadn't been installed properly & although that can technically happen with any anchor it's less likely with others. 

Online pwhole

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Re: What throughbolt?
« Reply #23 on: November 20, 2020, 03:52:07 pm »
It seems like the Petzl push-buttons are the way forward for genuinely eco-friendly exploratory bolting combined with ease of installation (and removal), but I'm trying to guess how many you'd need for a full-on expo - and how much extra sponsorship would be required! It's a shame they're so expensive as I would love to use something like that. Maybe we could have a chat at the club about buying a set of ten, which would probably cover local bolting trips OK, but I can imagine the conversation might be fraught, considering it would be the ballpark of one of our annual services bills.

Offline andrewmc

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Re: What throughbolt?
« Reply #24 on: November 21, 2020, 12:56:25 pm »
It seems like the Petzl push-buttons are the way forward for genuinely eco-friendly exploratory bolting combined with ease of installation (and removal), but I'm trying to guess how many you'd need for a full-on expo - and how much extra sponsorship would be required! It's a shame they're so expensive as I would love to use something like that. Maybe we could have a chat at the club about buying a set of ten, which would probably cover local bolting trips OK, but I can imagine the conversation might be fraught, considering it would be the ballpark of one of our annual services bills.

I can see them being great for aid climbing, but I wouldn't want to leave them in a cave even overnight (at least not in a damp cave wall) as I'd be worried about corrosion...

 

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