OT--Rock Anchors?

Jeff Reardon

Jeff Reardon

Well-known member
Nope, not talking about boat anchors. I put up a post a couple of months back about underwater epoxy. Research to date talking to everyone I know who has used them for my application--to attach water temperature monitors to immovable objects like boulder or ledge--is (1) a huge pain in the ass; and (2) subject to lots of failures to set in cold water. Since my thermometers are going into trout streams, that's not encouraging.

So a colleague sent me a paper from a group out in the Wyoming that have been using a drill and expansion or even screw-in bolts. They drill holes in the ledge or boulder, then insert an anchor and hang the data logger off it.

Some of these need to go in deep water. So, does anybody have suggestions for what I'd need for a drill to effectively drill into hard rock? It's Maine--a lot of my anchors will be going into granite. I assume a cordless drill won't do, but how much power will I really need?

And, for the harder part, anybody got an affordable drill option that can be used underwater? I planted one of these yesterday in 6' of water with a snorkel, and while that's not the norm, it won't be only one. Assuming that an underwater capable drill will be unavailable or cost-prohibitive, how about a source for really LONG drill bits suitable for drilling hard rock?

And finally, anybody have experience with either expansion bolts or just ratcheting bolts into holes in rock? These don't need to bear much weight, so any stainless steel or other non-rusting bolt ought to do.

I've seen a contractor do this to move large rock on some our restoration projects. Instead of an excavator with a thumb, they drilled holes and used some kind of anchor inserted in the hole to place the boulders with a crane. It was pretty slick, but the contractor who did that job has been bought out and I don't know where to find him to ask what they used.

Given the talents on this site, I'm guessing at least a few of you have some kind of work with stone and may have some ideas.

Otherwise I've got to go find a rock climber's forum with a bunch of handy folks like the ones who hang out here.
 
I suspect you're gonna torque a super long drill bit, if you start trying to hammer into granite. It'll develop a wobble early on.

See if you can find a Hilti UW. Underwater nail gun. No idea if it can beat granite or not.
 
I was gonna suggest an air powered drill but I assume you won’t have a compressor and a power source?
The toggle bolts should hold very well, I’ve used them to hold non-load bearing walls in concrete and they are solid once you tighten them.
 
Eric Patterson said:
Maybe something like this?


This place rents them.

Nemo HD-18V-6Li-50 Cordless Underwater Hammer Drill (Two 6Ah Batteries) Video

Watch the Nemo HD-18V-6Li-50 Cordless Underwater Hammer Drill (Two 6Ah Batteries) Video from RTO and view related product options.
rentaltoolsonline.com rentaltoolsonline.com
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Too cool. Just seeing one makes me want one! Glad they're expensive enough to keep that from happening.
 
Any working quarries in your area? They might have the necessary expertise and knowledge to steer you in right direction.

Best
 
Paul F Boundy said:
Any working quarries in your area? They might have the necessary expertise and knowledge to steer you in right direction.

Best
Click to expand...
Used to be. Next town to mine was a granite quarrying hot spot--supplied the granite for the Brooklyn Bridge, among many other famous structures. Best bar/restaurant in town in the Quarry Tap Room. But they are at least 30 years out of business. There are some folks still using scavenged or salvage stone for landscaping stone, grave markers, etc, though, and I may find someone at one of those.
 
However, research suggests all I need is a cordless hammer drill with a long enough masonry bit, and I think I can find those at a cost I can afford. Then I have at least two options. Most work/highest cost would be to use expansion, wedge, or sleeved bolts designed for rock climbing anchors. But they look to be about $10 each--not prohibitive, but enough to make me look for a cheaper alternative. The big problem with them is they are designed for safety, to be left in place a long time, very secure, and capable of handling a heavy load in a dynamic load in case of a long fall. Total overkill to hang 4 ounces of PVC pipe holder a logger the size of my thumb, and the smallest size is 10 mm, so has me drilling a pretty substantial hole. Option two would be stainless steel threaded eye-bolts. But to mount them in stone I will need some kind of anchoring adhesive, and it will have to be something that will set in a submerged hole. Off to research anchoring adhesive, and worried I will come up against the same issues other folks have warned me about with underwater application in cold water. I don't need strength--just something that will hold the bolt so it won't fall out for up to 12 months. Maybe one of the marine JB Weld products? 5200? Something designed for a plumbing application? Needs to quick setting, so I don't walk away and come back to find my $150 thermometer has washed down river.
 
Stainless steel eyed lag bolts at 1/4"4", or 5/16", 3". $3-4 each. That gets me to a small and relatively short hole to drill. Now I need to find an underwater anchoring epoxy.

Also wondering, since I'll need a long-length drill bit, if I'd save frustration with a larger diameter bit of hardware that would let me drill with a larger bit I'd be less likely to break? OTOH, I think the holes would be slower to drill.
 
Any experience with JB water weld for bonding? Seems to be their only product that will set if submerged, and it should be easy to stuff into a hole. Maybe too thick to stuff the bolt in the hole?

Or 5200 fast seal. Not sure about cold water curing, though. And some reviews suggest bonding with stainless is not good. All my applications are in freshwater. I could probably get away with zinc-coated, no?
 
Jeff, could you just take metal zip ties and find a decent rock to zip them around and hold the them to it and then let it down into the water?
 
Jeff, a cordless hammer drill should work fine although I"m not sure about the underwater part! I have used JB weld underwater and in freezing temps before and it has worked fine, real slow set-up time though! Have you considered using galvenized eye bolts instead of stainless?
I you drilled a 3/8 hole, stuffed it with JB weld, and used a 1/4" eye bolt I suspect you would be well into overkill!
 
How long do these things have to last? Plain ol’ TapCons into a predrilled pilot hole are simple to install, doesn’t require tapping or adhesive, is more than strong enough, and should get you a year or more before they corrode to the point of failure. The TapCon bit and driver set is very convenient because it allows you to swap from bit to driver on the same tool without removing the bit (this seems like it would be nice if working on your belly in a stream). I’ve never seen a stainless TapCon though.

I’d expect the underwater hammer drill to be the most expensive part of the plan.

Nate
 
benp said:
Jeff, could you just take metal zip ties and find a decent rock to zip them around and hold the them to it and then let it down into the water?
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Too many of my sites are ledge--or very large boulder fields. On smaller streams I have cabled or chained to trees on shore or downed wood in the channel, but these are big flashy high gradient rivers and I fully expect even large boulders will move in floods.
 
Nate Hoyt said:
How long do these things have to last? Plain ol’ TapCons into a predrilled pilot hole are simple to install, doesn’t require tapping or adhesive, is more than strong enough, and should get you a year or more before they corrode to the point of failure. The TapCon bit and driver set is very convenient because it allows you to swap from bit to driver on the same tool without removing the bit (this seems like it would be nice if working on your belly in a stream). I’ve never seen a stainless TapCon though.

I’d expect the underwater hammer drill to be the most expensive part of the plan.

Nate
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Tapcons like these? Are those just galvanized steel? Can they really be screwed or hammered into solid rock? Most of my sites will be in granite. I'd love an approach that did not require epoxy or anchoring compound. I think galvanized would be fine, but my system would greatly simplified if I can find anchor hardware with an attachment loop, like a screw eye, where I can attach my loggers with a carabiner or a shackle.

Tapcon Concrete Anchors | #1 Choice of Professionals

Tapcon Concrete AnchorsTapcon is the #1 recognized screw anchor brand in the industry. The blue, corrosion-resistant coating enables them to withstand the harshest conditions.
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I’ve used tapcon anchors with pre drilled holes in concrete and they work very well. Solid once set.
 
TapCon a tabbed d-ring like below onto the rock.

1784300188091.jpeg
Seems to fit your needs.

Only thing with TapCons is that you have to clean the stone dust out of the hole really well or they’ll bind up and possibly break about 3/4 of the way in. However, working under water should actually flush the dust from the hole very well, so I’m not terribly worried about that. I am assuming a TapCon masonry bit can drill granite without dulling instantaneously; never tried on anything except concrete, so some experimentation on dry land is appropriate before you commit to this plan. You can buy TapCon products at any hardware store, so availability will not be an issue.

Nate
 
Just checked. Masonry bits will struggle with granite. Looks like you’ll need a diamond coated bit. TapCons like a hole drilled within specific tolerances; abrasive diamond bits are less precise and grind a hole “close enough”. Some trial and error will be necessary to see if you get close enough for an TapCon. Abrasive bits also need to be used in “drill” mode, not “hammer” mode. Redhead concrete anchors (among others) are a friction fit option that will tolerate a less precise hole; you just have to figure out how to drive them underwater. Some sort of slide hammer should work. On the up side, abrasive bits should be water cooled. You won’t have to worry about that.

If you can’t make anything from the hardware store work for you, I know there are some really high tech systems for attaching permanent climbing anchor points to hard rock, but I suspect those are over-engineered for your needs. However, the is probably a climbing forum on REDDIT that could give you some good ideas to extrapolate from.

Nate
 
Thanks, all. One final question on the Tapcons or other hardware. Is anyone aware of a an anchoring system that can be driven into a pre-drilled hole rather than anchored with epoxy or cement? I was already planning to use the drill bits marketed for rock climbers. I'll keep looking for any underwater epoxy solution, but calls yesterday with pool and plumbing supply vendors were not encouraging. I think I'm going to have to bite the bullet and pay a lot for sleeved or expansion bolts. In the meantime, my auto repair shop has donated a pile of used brake rotors to use as anchors, which should reduce the number of places that I really need to drill anchor points into rock.
 
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