What throughbolt?

[Subpopulus Hibernia]

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. 

I've used concrete screws quite a lot, especially since they're very suited to the terrible cherty friable rock we have in much of Ireland as they don't stress the rock all that much. I just use a small scrap of of inner tube with a hole in the middle on the screw like a washer so it holds the screw in the hangar. And sure, the odd one will get the teeth fouled up, but when you can re-use the other ones four or five times then that's not really an issue. The best thing is how eco-friendly they are, you don't don't have to go through the faff of over-drilling an 8mm hole and then banging them in and mudding over the hole.

Never really noticed that they were particularly slow to place - though I know some Aussie cavers who use a mini-impact drill to drive them home when bolt-climbing. A ratchet spanner will do more or less the same thing though.

I know they're pretty much all that's used in Australia - all exploration (in Tassie at least) is done with concrete screws which can be drilled out and replaced with resin bolts if needed. Australian cave rescue use them as well for rescue practices.

For Alpine projects I can imagine that a big saving would be the extended battery life they give - you can drill a lot more 6mm holes vs overdrilled 8mm holes.

[Fjell]

In a spirit of idle curiosity, the rugby being over, I had a look at what Hilti have to offer these days for the truly paranoid.

They sell the 8mm HST-HCR in 1.4529 material, which is class V. So pretty swish and likely not going rusty that easily. They will sell you a box of 50 for about a grand incl VAT. A snip.

It must be a bugger to machine with all that unobtanium in it, so worth every penny no doubt.

https://www.hilti.co.uk/c/CLS_FASTENER_7135/CLS_WEDGE_ANCHORS_7135/r1117?CHA_GLOBAL_ANC_SIZE=M8&CHD_ANCHOR_LENGTH=115%20mm&combo_content=6c085b69675be789f65f8dd20e8a0a77&salespackquantity=50%20pc&itemCode=387258

[pwhole]

Hahahah. Good grief. But no doubt it's a lovely abseil

[Steve Clark]

The Hilti pricing will vary greatly depending on account status and how things are bundled.

The 8mm HST-HCR-75mm lists at £650+VAT / 50pc on our account. I've never (obviously!) bought some, but I expect it would be considerably cheaper if we spoke to the rep.

We buy a lot of their HUS-6 6mm self-cutting concrete screws for work. If we are not logged-in, 100pc of of 160mm HUS-6 is 146+VAT. Our account lists them at 30+VAT.

On the bundling, the smaller HUS-6 anchors can be bought bundled with 'free' 6mm TE-CX bits (the good ones), and are 10+VAT a box. That's cheaper than the bit by itself.

Edit : The A4 stainless version of the 'ultimate' HST3 is the HST3-R. They are about 3.50 each with no discount. The 'premium' HST2 in A4 is 2.00+VAT and carbon steel 70p.

[PeteHall]

I've always been amused by the pricing at Hilti.

Even as a very occasional customer I always manage to negotiate a considerable discount on the list prices. Makes you wonder why they bother with the overinflated price in the first place.

Either wat the products are second to none and I never buy anything else for drill bits. As for through bolts, I was fortunate enough to inherit a large box of M8 galvanised and a handful of M8, M10 and M12 stainless Hilti anchors from a former employer (they actually owed me a lot more than that, but such is life), which I am still working my wat through 

[Fjell]

I did once pay about a million quid a pop for lumps of inconel-sheathed carbon steel.

We were offered something very close to 1.4529 in the solid, but I rejected it as insufficiently corrosion resistant in the environment and temp. I would likely be standing near it when it was put under load, and I’m worth it.....

[pwhole]

I used the same 8mm Hilti bit for over a year and drilled many, many holes - I lost count, but probably a couple of hundred, and I only retired it as I thought I probably should - I had several new ones! I think it was about double the cost of a normal bit, but probably about ten times the lifespan

[David Rose]

I was with a team that started using concrete screws in Huautla in 2018, re-rigging the early pitches of Agua de Carrizo which, back in the day, ie in 1978, was rigged the old-fashioned American way, that is, by tying a length of Bluewater or PMI to a natural belay, then abseiling down. After a couple of trips we started to notice that several screws on the first two pitches - 35 and 110 metres, with multiple rebelays - were just pulling out. The rock, it seemed, was too soft, or in some places, too brittle. Bloody terrifying. We binned the lot.

[andrewmc]

I was with a team that started using concrete screws in Huautla in 2018, re-rigging the early pitches of Agua de Carrizo which, back in the day, ie in 1978, was rigged the old-fashioned American way, that is, by tying a length of Bluewater or PMI to a natural belay, then abseiling down. After a couple of trips we started to notice that several screws on the first two pitches - 35 and 110 metres, with multiple rebelays - were just pulling out. The rock, it seemed, was too soft, or in some places, too brittle. Bloody terrifying. We binned the lot.

Did you have more success with through-bolts? Generally screws are supposed to be _better_ in weak rock, as the load is more distributed, but I can also imagine that (like so many things in life) 'it depends'.

[Joel Corrigan]

Years ago in the state of Guerrero in Mexico we were searching for & exploring caves but a lot of these places had previously been discovered by a lone American who spent years in the area.  We kept seeing old Spits in the walls but chose to install our own anchors (can't remember what we were using but could have been Spits too).  If I remember correctly, someone met this guy at a congress & during a discussion he apparently exclaimed: "oh, so that's what those cones are for: I just threw them away as I never thought they had a purpose".  So the dude had been self-drilling Spits for years in some fairly remote locations & had just tapped the bare Spit into the hole without using the cone.  For those that haven't done any bolting using these gizmos before, it's kind of like using a condom with a hole in the end: from a distance it looks the same but it hugely increases the adventure whilst drastically reducing the safety!!     

[Fjell]

The preload in stud bolts exceeds any likely shock load (even in 8mm) and you can happily keep using a spanner to check it as often as you like. If you used 10mm bolts, I would think the preload exceeds the nominal 22kn used for climbing standards.

What are you going to do with screws - keep rotating it in the rock until you break something? Wait.....

[Steve Clark]

I used the same 8mm Hilti bit for over a year and drilled many, many holes - I lost count, but probably a couple of hundred, and I only retired it as I thought I probably should - I had several new ones! I think it was about double the cost of a normal bit, but probably about ten times the lifespan

TE-CX are by far the best drill bits available.

For the gear nerds - They have a tiny wear indicator depression on the side of one the flutes near the tip. This is quite easy to see when they are new. The idea is that if this depression is still visible, the bit will be drilling a large enough hole to accept anchors ok. It also serves as evidence for their guarantee. If the tip wears out or fails whilst the indicator is still visible, then there is a problem with the bit and they will replace it.

https://images.homedepot-static.com/productImages/027c42c7-415a-4c5a-bc08-8d215b51885d/svn/hilti-masonry-drill-bits-2206616-c3_600.jpg

[Pitlamp]

Apart from one throughbolt that I didn't install. And now it's there for ever - in the wrong place!

pwhole's remark above interested me - and prompted me to ask a question which may be viewed as a slight digression (for which I apologise in advance).

I have a need to remove a particular Throughbolt, so I've been wondering on how this might be done. I know that overtightening the nut causes the a Throughhbolt to start creeping out of the hole but removal in this way is not possible because the thread is not continuous to the bottom of the bolt. I'm wondering about using a few larger nuts to act as spacers so that the unwanted Throughbolt can be extracted fully using its own thread.

Do folks reckon this will work? Also, would this compromise the safe re-use of the same hole with a future replacement Throughbolt (if it results in wear to the sides of the hole during extraction)?

(The consensus might also help pwhole solve the problem he mentioned above.)

[Fishes]

I've managed to remove and replace spits on a number of occasions but for a throughbolt I would use a diamond core drill and replace it with a resin fix anchor.

[Fjell]

Apart from one throughbolt that I didn't install. And now it's there for ever - in the wrong place!

pwhole's remark above interested me - and prompted me to ask a question which may be viewed as a slight digression (for which I apologise in advance).

I have a need to remove a particular Throughbolt, so I've been wondering on how this might be done. I know that overtightening the nut causes the a Throughhbolt to start creeping out of the hole but removal in this way is not possible because the thread is not continuous to the bottom of the bolt. I'm wondering about using a few larger nuts to act as spacers so that the unwanted Throughbolt can be extracted fully using its own thread.

Do folks reckon this will work? Also, would this compromise the safe re-use of the same hole with a future replacement Throughbolt (if it results in wear to the sides of the hole during extraction)?

(The consensus might also help pwhole solve the problem he mentioned above.)

With a decent sized spanner or breaker bar and socket (more doable in 13mm) it will either come out or snap. If it snaps, hammer it back in until it is flush. Maybe leave it alone after that either way unless you are desperate, otherwise maybe drill it out to the next size up?

[Rob]

...With a decent sized spanner or breaker bar and socket (more doable in 13mm) it will either come out or snap. If it snaps, hammer it back in until it is flush. Maybe leave it alone after that either way unless you are desperate, otherwise maybe drill it out to the next size up?

I think the other (quite likely) possibility is that the bolt will start to rotate with the nut. This is very annoying when you want your hanger back! 

[Pitlamp]

Um - I think I'll just have to try this and see what happens.

It was me that placed this particular bolt (not in one of our popular caves) and I always over-drill the holes, for reasons which other folk have given above. So the default option is to hammer in flush with the rock. But I'd prefer to extract the bolt so the hole may be used again. (I guess part of this is that I was wanting to show it can be done, providing an example which I hoped others might then follow. I'm trying to factor in conservation here.)

Another option might be to pull the bolt out using the curved end of a bog horse's head bar, with a packing piece under the curved bit to position it to maximum advantage. (a bit like removing a nail with a claw hammer.)

[SamT]

pwhole's remark above interested me - and prompted me to ask a question which may be viewed as a slight digression (for which I apologise in advance).

I have a need to remove a particular Throughbolt, so I've been wondering on how this might be done. I know that overtightening the nut causes the a Throughhbolt to start creeping out of the hole but removal in this way is not possible because the thread is not continuous to the bottom of the bolt. I'm wondering about using a few larger nuts to act as spacers so that the unwanted Throughbolt can be extracted fully using its own thread.
Do folks reckon this will work? Also, would this compromise the safe re-use of the same hole with a future replacement Throughbolt (if it results in wear to the sides of the hole during extraction)?

(The consensus might also help pwhole solve the problem he mentioned above.)

Pitlamp - this video!!



same thing..

[SamT]

Only thought is that re-using the hole with another identical diameter through bolt might not be as secure, since as you say, the hole may have been enlarged at the bottom.  Would be interesting to experiment though.

[MarkS]

I think Simon Wilson tried the above technique with little success. I think that if you want an anchor to be removable, don't place a throughbolt.

[Pitlamp]

Thanks for the video links Sam - interesting. The key thing seems to be to wear down a lip on the cone shaped end so the sleeve doesn't travel / tighten whilst the anchor is being extracted. Might have a play some time using an old car jack which sometimes gets used for shifting boulders.

Or - maybe Simon Wilson will see this and hopefully share his experiences? (Thanks for mentioning this MarkS.)

[Ian Ball]

Simon shares pretty much everything he does!

http://www.resinanchor.co.uk/5.html

[SamT]

I think Simon Wilson tried the above technique with little success. I think that if you want an anchor to be removable, don't place a through-bolt.

I agree, but Pitlamp was asking for a technique for one particular placement, already installed.

No evidence of Simon having removed one of those type of sleeved through bolts on his page.  Lots of very similar videos online from the states using the same technique, generally looks pretty straight forward and successful.  I think the key is probably the hydraulic puller they are using and also using something that you can 'pull' up on, whilst spinning the bolt.  i.e. just a socket spinning the bolt isn't going to allow you to pull up on the bolt which is what causes the requisite groove to be cut in the cone.

[Pitlamp]

The difficulty of extracting these things will give me more confidence in using them next time I encounter a roof when aid climbing an aven.   

[Fishes]

I think Simon Wilson tried the above technique with little success. I think that if you want an anchor to be removable, don't place a through-bolt.

I agree, but Pitlamp was asking for a technique for one particular placement, already installed.

No evidence of Simon having removed one of those type of sleeved through bolts on his page.  Lots of very similar videos online from the states using the same technique, generally looks pretty straight forward and successful.  I think the key is probably the hydraulic puller they are using and also using something that you can 'pull' up on, whilst spinning the bolt.  i.e. just a socket spinning the bolt isn't going to allow you to pull up on the bolt which is what causes the requisite groove to be cut in the cone.

For spits we made up something like a bearing puller. The centre bolt had a hole drilled trough it so we could tap the cone while giving it a gentle pull. You wouldn't need the centre hole for a throughbolt but the simple puller design should work without taking some fancy hydraulic thing into a world of mud and grit.