Author Topic: concrete bolts  (Read 4353 times)

Offline Gareth Davies

  • regular
  • *
  • Posts: 63
  • SWCC & CDG
concrete bolts
« on: April 27, 2012, 11:17:39 am »
Has anyone here tried using concrete bolts for aid climbing instead of thru bolts. I'm not suggesting for pitch heads, rather using 1/4" dia screws to speed up climbing. It would have the benefit of being reusable and leaving nothing behind.

If you wanted to reuse the holes or enlarge for thru bolts / glue in's this could be easily done.

If anyone has tried these, are their differences with the various tensile strengths of the different manufacturers.

Thanks
Gareth

Offline SamT

  • Global Moderator
  • forum hero
  • *****
  • Posts: 6259
    • The Eldon Pothole Club
Re: concrete bolts
« Reply #1 on: April 27, 2012, 12:23:06 pm »

Some discussion here : -http://ukcaving.com/board/index.php?topic=6897.0 though more for anchors than aiding.

I've used 12mm ones for anchors before and think they are great. As you say, I think best for temporary anchors (pushing/exploring) that can be removed for either re-use, or for replacement with more permenant anchors in the same place, as they haven't stressed the rock like thru bolts

Offline Gareth Davies

  • regular
  • *
  • Posts: 63
  • SWCC & CDG
Re: concrete bolts
« Reply #2 on: April 27, 2012, 01:27:40 pm »

I've used 12mm ones for anchors before and think they are great. As you say, I think best for temporary anchors (pushing/exploring) that can be removed for either re-use, or for replacement with more permenant anchors in the same place, as they haven't stressed the rock like thru bolts

I was thinking more 6 or 8mm used in conjunction other aid methods to speed up the bolting of a route and increase the no of settings per battery.

Offline jarvist

  • obsessive maniac
  • ***
  • Posts: 424
  • Imperial College CC / Northern Pennine Club
    • Imperial College Caving Club
Re: concrete bolts
« Reply #3 on: April 28, 2012, 10:46:38 am »
I've used 8mm (so compatible with standard hangers), but never dared actually hang on them (just drag boulders). An issue is that you have to fully seat them, whereas with 8mm through bolts you can choose how deep a hole you want (once you're passed the sleeve / collar bit), so I'm not sure whether they offer the same battery potential as through bolts.

An alternative but not as cave conserving is to get some cheap zinc passivated ('yellow') short through bolts for the temporary fixings, then using 'full length' / 80mm stainless throughbolts for the permanent rigging.

Offline Rob

  • forum hero
  • *****
  • Posts: 2314
  • The Eldon
    • Eldon PC
Re: concrete bolts
« Reply #4 on: April 28, 2012, 12:10:49 pm »
On our Crete 2009 expedition we used 6mm multi monti screws to explore down to 560m deep, as per these.....
http://www.herrmannframes.com/pdf/HECO%20Multi-Monti.pdf
The main reason was to reduce drill hole size, to try to improve battery length due to no charging facilities.

Pros
  • Fast drilling
  • Removable - good for conservation (both of pocket and cave)
  • Cheap
  • We never had any pull out  :thumbsup:

Cons
  • 6mm drill bits don't clear wet limestone well, meaning similar battery consumption as 8mm holes
  • When derigging have to remove the bolt to get your hanger back, which takes a lot of time when there is over 100 bolts
  • Need to drill full length (as per SamT's comment)

The end is where we start....

Offline jarvist

  • obsessive maniac
  • ***
  • Posts: 424
  • Imperial College CC / Northern Pennine Club
    • Imperial College Caving Club
Re: concrete bolts
« Reply #5 on: April 29, 2012, 06:52:18 pm »
Just to comment on battery consumption, my current hypothesis is that drills will have an optimal power efficient diameter that they drill. If you're trying to drill too large with an underpowered drill, you waste too much due to frictional loses. Too powerful a drill for the diameter, and you're squandering most of the power trying to pulverise already pulverised rock (and risk over heating your drill bits).

Certainly our experience from last summer's expedition was that the tiny Bosch Uneo (max 10mm concrete, 0.9 J per impact) was more ~20% efficient than a middle sized Makita BHR162 (max 16mm, 1.2J / impact) at drilling 8mm.

Bolt holes / shot holes per battery is probably the single most important specification that a caver has for a drill, it'd be really nice if someone could do a side by side test on a lump of limestone at some point...

Offline potholer

  • forum hero
  • *****
  • Posts: 1157
    • http://www.potholer.com
Re: concrete bolts
« Reply #6 on: April 30, 2012, 09:29:22 pm »
Bolt holes / shot holes per battery is probably the single most important specification that a caver has for a drill, it'd be really nice if someone could do a side by side test on a lump of limestone at some point...
A test would certainly be interesting, though I guess drill bit quality can have a fair effect - do the drills for the Uneo have a direct equivalent in proper SDS bits?

Pressure applied might also come into it. I guess someone pressing a drill harder than necessary into the rock might have a significant effect on drilling efficiency. People might be rather lighter with a 'baby' drill.

Playing on the surface with a (very nice) new 36V Hilti a few weeks ago, some people seemed to try and push it down into the test boulder. I found just holding it upright and basically letting its own weight do the pushing seemed to end up with rather swifter drilling.

Offline bograt

  • forum hero
  • *****
  • Posts: 3549
  • Speliodecrepit
Re: concrete bolts
« Reply #7 on: April 30, 2012, 10:34:13 pm »
Having some experience of drilling, I agree with Pitlamp that if any fair comparison of drills is to be undertaken, drill bit quality is the governing factor, bits used in all test drills need to be of identical make and identical use. This suggests that new bits of identical make be put in each test drill at commencement and if replacement is needed all are replaced together, once a superior drill is identified, then a similar test can be carried out to identify a superior bit, I think this would be a series of very useful tests for our specialised field, if someone could sell this idea to the commercial market, maybe Which magazine would be interested?
 Re; pressure used, in my experience the operator gets a feel for the right pressure after a short time, its a balance between power of drill, sharpness of bit and hardness of rock.
Aim low, achieve your goals, avoid disappointment

Offline jarvist

  • obsessive maniac
  • ***
  • Posts: 424
  • Imperial College CC / Northern Pennine Club
    • Imperial College Caving Club
Re: concrete bolts
« Reply #8 on: April 30, 2012, 11:35:51 pm »
Unfortunately for the reasons of comparison the Uneo takes SDS-Quick, however they do seem to have very similar tips to other middle-priced Bosch drill bits.

I'd imagine that if you were doing a side-by-side comparison of SDS+ drills, you could actually pass the same drill bit between drills for successive holes (possibly via a quick chill in a bucket of water), rotating between drills. This way the batteries get a few minutes rest between uses, which is a slightly more realistic model for bolting use.

I know one gets a 'feel' for the correct pressure, but that doesn't make it right! I'm certainly tempted to push on a drill, even though I know rationally that you want no more pressure than the weight of the drill resting on its nose.

Unfortunately given our rather specialist requirements (8mm holes in damp limestone, a long way from a charging outlet, with chilled batteries, etc.), I suspect we'd have to do our own tests.

Offline Jopo

  • obsessive maniac
  • ***
  • Posts: 397
Re: concrete bolts
« Reply #9 on: April 30, 2012, 11:58:05 pm »
(possibly via a quick chill in a bucket of water), rotating between drills. This way the batteries get a few minutes rest between uses, which is a slightly more realistic model for bolting use.

Not to be recommended. Carbide cracks very easily when quenched.

Jopo

Offline Speleokitty

  • menacing presence
  • **
  • Posts: 210
Re: concrete bolts
« Reply #10 on: May 19, 2012, 12:41:34 pm »
I have used the 8x55mm Excalibur Eyebolts for aid climbing and larger ones for anchors. They are cheap, reusable and you don't need to mess about with hangers.

Offline pwhole

  • forum hero
  • *****
  • Posts: 1614
  • TSG, DCA, PDMHS
    • Phil Wolstenholme website
Re: concrete bolts
« Reply #11 on: May 19, 2012, 01:00:20 pm »
Anyone have experience of pre-drilling smaller-diameter holes first - in terms of battery life? As in, you want to place a 14mm diameter sleeve anchor bolt (10mm bolt diameter), but drill out with, say, a 6mm first, and then the 14mm? Is this likely to conserve more juice than just drilling the 14mm straight in?

Offline jarvist

  • obsessive maniac
  • ***
  • Posts: 424
  • Imperial College CC / Northern Pennine Club
    • Imperial College Caving Club
Re: concrete bolts
« Reply #12 on: May 19, 2012, 03:16:36 pm »
Anyone have experience of pre-drilling smaller-diameter holes first - in terms of battery life? As in, you want to place a 14mm diameter sleeve anchor bolt (10mm bolt diameter), but drill out with, say, a 6mm first, and then the 14mm? Is this likely to conserve more juice than just drilling the 14mm straight in?

No - it probably wouldn't work (at all?), and it wouldn't save any energy. You do this with cutting drill bits in metal, not rock / masonry (percussion) bits.

Offline mmilner

  • Experienced digging / conservation juggling
  • forum hero
  • *****
  • Posts: 1169
  • Outside Handshake Cave, Manifold Valley.
    • Darfar P.C. web site
Re: concrete bolts
« Reply #13 on: May 19, 2012, 03:28:42 pm »
Anyone have experience of pre-drilling smaller-diameter holes first - in terms of battery life? As in, you want to place a 14mm diameter sleeve anchor bolt (10mm bolt diameter), but drill out with, say, a 6mm first, and then the 14mm? Is this likely to conserve more juice than just drilling the 14mm straight in?

No - it probably wouldn't work (at all?), and it wouldn't save any energy. You do this with cutting drill bits in metal, not rock / masonry (percussion) bits.

It does work, I have done it on many occasions when drilling shotholes. The smaller drill bit goes in really quickly, then you can ream it out with a larger drill bit. You have to take care not to press too hard though as you use the larger bit, else it will jam and take more power out of the battery than you may have saved. Press very lightly until you can just feel the bit cutting, it will then go in very quickly...

I have felt that I have got more drilling capacity out of the battery doing this, but couldn't  definitely say I had. Best thing is to try it yourself...

Mel.
Norbert Casteret (Ten Years Under the Earth) and Pierre Chevalier (Subterranean Climbers) were my inspiration to start caving. (And I'm still doing it.) Secretary, Darfar Potholing Club, the Peak District.

Offline jarvist

  • obsessive maniac
  • ***
  • Posts: 424
  • Imperial College CC / Northern Pennine Club
    • Imperial College Caving Club
Re: concrete bolts
« Reply #14 on: May 19, 2012, 05:32:45 pm »
then you can ream it out with a larger drill bit. You have to take care not to press too hard though as you use the larger bit, else it will jam

But you shouldn't be reaming the hole, percussion bits don't have a cutting edge (look at the carbide tips - they're more or less symmetric), the flutes are there just to clear the dust out. In metal work you use successively sized bits to minimise the torque on the bit and work piece and avoid the risk of jamming / get a cleaner cut. And then you use your precision sized reamer to get the exact hole diameter (cutting a tiny amount).

In masonry I'd be worried by the extra torque you were putting on the larger drill bit as it sunk itself into the edges of the pilot hole. I'd also be worried about over heating and wear of the edges of the carbide tip.

Unless drilling holes beyond the capacity of your drill, I can't see how this would help.

Quote
I have felt that I have got more drilling capacity out of the battery doing this, but couldn't  definitely say I had. Best thing is to try it yourself...

I'd suspect like a lot of things this is an area where it's easy to trick oneself. The only way to know for certain would be to do a few side-by-side comparisons.

Offline mmilner

  • Experienced digging / conservation juggling
  • forum hero
  • *****
  • Posts: 1169
  • Outside Handshake Cave, Manifold Valley.
    • Darfar P.C. web site
Re: concrete bolts
« Reply #15 on: May 19, 2012, 09:08:31 pm »
But you shouldn't be reaming the hole, percussion bits don't have a cutting edge (look at the carbide tips - they're more or less symmetric), the flutes are there just to clear the dust out. In metal work you use successively sized bits to minimise the torque on the bit and work piece and avoid the risk of jamming / get a cleaner cut. And then you use your precision sized reamer to get the exact hole diameter (cutting a tiny amount).

In masonry I'd be worried by the extra torque you were putting on the larger drill bit as it sunk itself into the edges of the pilot hole. I'd also be worried about over heating and wear of the edges of the carbide tip.
I'd suspect like a lot of things this is an area where it's easy to trick oneself. The only way to know for certain would be to do a few side-by-side comparisons.

Fair comments, (though if the bits don't have any cutting edges, how can they drill a hole), and the fact remains that as long as you only press lightly on the drill the bits will ream the hole out  to a bigger diameter easily. You can feel when the bit bites into the edges of the existing hole. I don't know anything about the techy stuff. All I know is I have been doing it on odd occasions for 20 years with no problems. And I don't really care about the effect on the drill bits, they are expendable items anyway.... when I feel they are not drilling as well as previously, I'll just get a new one...

Norbert Casteret (Ten Years Under the Earth) and Pierre Chevalier (Subterranean Climbers) were my inspiration to start caving. (And I'm still doing it.) Secretary, Darfar Potholing Club, the Peak District.

Offline SamT

  • Global Moderator
  • forum hero
  • *****
  • Posts: 6259
    • The Eldon Pothole Club
Re: concrete bolts
« Reply #16 on: May 19, 2012, 10:36:10 pm »

Not an expert or owt - but the two types of bit do work very differently..

I metal bit has a cutting edge - like a veg peeler - that slices through the metal to cut a hole.
An sds masonry bit works more like the end of a chisel, and is just a very fast way of drilling a hole the 'old' way with a chisel. i.e. hit turn a bit, hit turn a bit, hit turn a bit. 

Pilot holes in metal work well as the larger drill just has to 'peel' much less metal from the edge of the hole. 
A larger SDS bit, following a smaller hole is just going to be using the edge of its 'chisel'

My guess is that drilling a pilot hole for an SDS bit is going to knacker up your drill bit and not really save you time/power.

empirical evidence (i.e. side by side comparison) is needed to say for certain though.



Offline bograt

  • forum hero
  • *****
  • Posts: 3549
  • Speliodecrepit
Re: concrete bolts
« Reply #17 on: May 19, 2012, 11:16:12 pm »
I am with Sam on this one, I have put more yardage into rock than most of you,(I used to do it for a living), putting pilot holes into rock will bugger up two drill bits, the pilot drill and your full sized drill, go for a tungsten carbide chisel bit (SDS or similar) and go straight in. Rock drilling is totally different to metal drilling. To understand the difference, just try using a star bit and lump hammer to put a hole in metal.
 Nobody is an expert, but I am experienced.
Aim low, achieve your goals, avoid disappointment

Offline TheBitterEnd

  • forum hero
  • *****
  • Posts: 1477
  • KCC
    • KCC - Join an active club
Re: concrete bolts
« Reply #18 on: May 20, 2012, 02:45:08 pm »
Also drill bits don't come to a point, if you look at the end of one there is a chisel like edge in the middle. When cutting metal it is necessary to push this edge into the metal, so a pilot hole means a smaller edge and therefore less force. Ideally the pilot hole is larger than the length of the flat edge on the next size bit you intend to use.

When using a hammer action drill the whole edge chisels away the rock, in fact I would guess that the only reason a masonry drill but is conical is so that you can start a hole without the bit skating around, otherwise it might as well be flat.
'Never argue with a fool, onlookers may not be able to tell the difference.' — Mark Twain

Offline SamT

  • Global Moderator
  • forum hero
  • *****
  • Posts: 6259
    • The Eldon Pothole Club
Re: concrete bolts
« Reply #19 on: May 20, 2012, 08:54:06 pm »

Quote
in fact I would guess that the only reasonin fact I would guess that the only reason a masonry drill but is conical is so that you can start a hole without the bit skating around, otherwise it might as well be flat.

never thought about that - but your most probably right.