How do you drill REALLY hard rock. Diamonnd drills?

Just got home from a long trip to Cayman Brac where I put up some new routes on a new wall.   In this wall there is a vein of purple stone that is like marble.  The surface is smooth, like metal, and at the top is this rare, cream-colored flowstone that is super hard, super textured and somewhat translucent.  (sorry, no photo.)   I was trying to put in some temporary 3/8" expansion bolts at the top, and got spanked.  The drill would go in normally about an inch, and then just stop.  Here's the two Hilti drill bits I used.  

Combined I got three, count 'em, three 1.5" deep holes out of these two bits before they were destroyed.   The holes weren't really deep enough for the bolts to go in all the way (3"), so this turned into a real cluster since I had to aid back to where I just came from.  I want to bolt this route next year and need to bring the right tools.

I've heard that I need a diamond core style drill but when I search for them, I don't find SDS+ versions, and they seem to need water cooling.  Does anyone here have experience with them?  Not sure how to proceed.

Hand drill? Prevent the bits from overheating. Problem is drilling super hard quartzite can take 1 hour plus for a shorty 3/8" bolt even when experienced Yosemite hand drillers are at work...and since you probably want to end up with titanium then the short 3/8" hole is just the beginning for you! And 14mm holes that are long enough for Eterna bolts would be out of the question for hand drilling in super hard rock.

Seems unlikely that any non-hammer-drill bit would be made in SDS, and diamond coated stuff is definitely not for hammer drilling.

No, Bosch power drill.   I was trying to put in steel expansion bolts as temporary working anchors so I can clean and drill for the Ti glue-ins.   There's a 10' horizontal roof over this wall, so it's hard to get a rope over the prospective route.    (For the first route, I dangled in the wind for an hour swinging a hook at the end of a triple sling until I could hook a pocket and pull myself in.)

I could skip putting in the steel bolts by aiding in, drilling the Ti anchors, and then aiding out again while the glue cures, but I need a method of drilling this stuff.   I can set my drill to not hammer, but would want an SDS end on the drill bit.  

From other routes that I've bolted I know I can drill the lower purple rock with a regular rock drill.   It's only the top 15' or so that seems to have the cream-colored devil rock, so we're talking the last bolt and anchors.

 I used to drill lots of holes in concrete. A core drill would have to bolted to the wall. I’m not sure why someone would recommend that. You said you’re using Hilti bits so I would call Hilti and explain your situation. Hilti will have an answer and will warranty those bits.

I would try a bit that has a more concentric tip.  If you go to Home Depot or Lowe's you will find them.  

If you decide to use a core bit this is who I use.  I use this setup for bolt removal.
http://www.ukam.com/
I have used their sintered and electroplated diamond bits and they are great.  The sintered bits are more fragile but they last longer.  You need to use it with a swivel adapter for water cooling.  I attach the swivel adapter to my hammer drill with a chuck adapter.  It's expensive and the drilling is slow.

Bill Kirby wrote:  I used to drill lots of holes in concrete. A core drill would have to bolted to the wall. I’m not sure why someone would recommend that. You said you’re using Hilti bits so I would call Hilti and explain your situation. Hilti will have an answer and will warranty those bits.

Yup, I'm planning on calling Hilti, but I'm also trying to gather as much information as I can before I do.  

Why do you think Hilti will warranty (replace?) those bits?  As far as I can tell, I tried to drill something they are not intended to drill.

need water cooling.

That.

It's gun suck major ass.

dameeser wrote: I would try a bit that has a more concentric tip.  If you go to Home Depot or Lowe's you will find them.  

I'm confused by this comment.  The tips on the drills pictured above are GONE.   And, IMHO, Hilti makes the finest equipment available.

If you decide to use a core bit this is who I use.  I use this setup for bolt removal.
http://www.ukam.com/
I have used their sintered and electroplated diamond bits and they are great.  The sintered bits are more fragile but they last longer.  You need to use it with a swivel adapter for water cooling.  I attach the swivel adapter to my hammer drill with a chuck adapter.  It's expensive and the drilling is slow.

Got a photo or a link to a swivel adapter for water cooling that is useable for what I'm doing?  You know, hanging from a rope.

Using water to cool the core bit is not as bad as it sounds.  Here is a picture of my setup.  The swivel adapter is from the ukam website.  Everything else I pieced together from the hardware store.  I used an MSR dromedary.

THIS:VS THIS:

dameeser wrote: Using water to cool the core bit is not as bad as it sounds.  Here is a picture of my setup.  The swivel adapter is from the ukam website.  Everything else I pieced together from the hardware store.  I used an MSR dromedary.

Hmmm... looks doable.  Is the water sleeve available in SDS so I can skip the chuck that converts SDS to smooth shaft?  How many holes do you get out of one dromedary?  Which is what, 1.5 litres?  EDIT: you added a photo, looks like 4 litres?

THIS:

VS THIS:

The Hilti bits are, well they were, four bladed bits!

They don't have an sds-plus version that I am aware of.  They seem to be a helpful company, email them and ask them if they could do that for you.  The last time I went out and used this setup I think I got 5 bolts removed and I still had a little water leftover.  The first time I was only able to remove 2 bolts before I ran out of water.  There was a learning curve.  I'm not sure how helpful this information will be for your situation though.  I am using a 3\4" OD bit and i'm only going about 1" deep.  Not super hard rock, Eldorado Canyon sandstone.  Are you able to get a sample?  If so, bring it down to Eldo and you can test it out with this setup.

We've run into this problem drilling in the quartzite of Big Cottonwood while doing bolt replacement. The carbide tip of the Hilti CX bits we were using sometimes broke off when overheated leaving a chunk of metal in the hole. One of our more persistent volunteers proceeded to destroy more bits in the ensuing carbide mine while thinking, "damn, this rock is hard!". It was a 1/2" hole, so we used a worn out 3/8" bit and were able to get through to fish out the metal.

The CX bits are nice, but we've stopped using them in our local quartzite. There's too much leverage on the wings which don't look to be completely welded onto the shaft. We just use 2-3 bits per hole to avoid overheating while having plenty of fresh bits on hand. I think we were averaging around 4-5 holes per bit placing 1/2" Wave bolts.

jonathan knight wrote: We've run into this problem drilling in the quartzite of Big Cottonwood while doing bolt replacement. The carbide tip of the Hilti CX bits we were using sometimes broke off when overheated leaving a chunk of metal in the hole. One of our more persistent volunteers proceeded to destroy more bits in the ensuing carbide mine while thinking, "damn, this rock is hard!". It was a 1/2" hole, so we used a worn out 3/8" bit and were able to get through to fish out the metal.

The CX bits are nice, but we've stopped using them in our local quartzite. There's too much leverage on the wings which don't look to be completely welded onto the shaft. We just use 2-3 bits per hole to avoid overheating while having plenty of fresh bits on hand. I think we were averaging around 4-5 holes per bit placing 1/2" Wave bolts.

For what it's worth, in the quartzite in Ogden (basically the same rock as BCC), I've had similar problems and might chew through one bit per hole when drilling. Definitely going slow and avoiding overheating is crucial. Using the bits pictured above has been helpful, too. Also clutch has been using 3/8" bits initially to do most of the hole, then clean up with a 1/2" bit. You still burn through a bunch of bits, but it saves the nice expensive 1/2" bits and gets many more holes per bit that way. 

Does it help to first drill a smaller-diameter hole? For example, start with 1/4", then 5/16", and finally 3/8"?

Also, to avoid dealing with complicated water-cooling systems, could one just remove the bit regularly and squirt some water in?

dameeser wrote: They don't have an sds-plus version that I am aware of.  They seem to be a helpful company, email them and ask them if they could do that for you.  The last time I went out and used this setup I think I got 5 bolts removed and I still had a little water leftover.  The first time I was only able to remove 2 bolts before I ran out of water.  There was a learning curve.  I'm not sure how helpful this information will be for your situation though.  I am using a 3\4" OD bit and i'm only going about 1" deep.  Not super hard rock, Eldorado Canyon sandstone.  Are you able to get a sample?  If so, bring it down to Eldo and you can test it out with this setup.

I'll have to see if an SDS version is available.   No, I don't have a sample here.

So please clarify this for me...   The usual masonry bit drills a hole you can put a bolt in.  Does a "core" bit leave a core in the hole?   You said you're using it to remove old bolts, so I imagine it does. So how do I get the core out?   I need 9/16" (14mm) x 2.5" (60mm) holes for glue-in bolts, so I need to have a "normal" hole.

Jon Nelson wrote: Does it help to first drill a smaller-diameter hole? For example, start with 1/4", then 5/16", and finally 3/8"?

Maybe.  After the first bit was wrecked I paid close attention to what was happening the second time.   Both times the bit went in normally about 1" and then, bam, it just stopped progressing.  The second time I took the bit out almost immediately and the tip was already gone.    You can see this in the photo: the first bit, on the left, I kept drilling; the second, the tip was broken off.

Also, to avoid dealing with complicated water-cooling systems, could one just remove the bit regularly and squirt some water in?

So considering what I wrote above, it's not clear that overheating is the root cause.   Something to ask Hilti about.

Jon Nelson wrote: Does it help to first drill a smaller-diameter hole? For example, start with 1/4", then 5/16", and finally 3/8"?

Also, to avoid dealing with complicated water-cooling systems, could one just remove the bit regularly and squirt some water in?

"remove the bit regularly"... you'd have to remove it like every 10 seconds if you wanted the water to actually have a chance of counteracting the heating involved..

or you could always go for a more simple "water cooling system" ;)

Oh, by the way, I've drilled many hundreds of holes in the rock down there (700? More?).  I've had drill bits get dull but I've never had a drill bit break or be ruined like this before.  There's something evil under there!   

John Byrnes wrote:

Yup, I'm planning on calling Hilti, but I'm also trying to gather as much information as I can before I do.  

Why do you think Hilti will warranty (replace?) those bits?  As far as I can tell, I tried to drill something they are not intended to drill.

Sorry I’m late. I’m moving to San Francisco and it’s kinda taken over my life lately.

 In my experience Hilti will warranty anything broken. You tired to drill into hard rock and the drill bit broke. Hilti has warrantied bits I drilled into rock. I will explain to them what you tried to do and see what they can do for you.

 Have you checked out air powered rock drills? It’s dangerous to drill horizontally with them but I’ve done it. 

  

I've never drilled anything close to this hard but find the topic very interesting.

I have drilled some rather soft limestone and I go really fast. Could it be that you are accustomed to moving too fast?

Another thought. It's a 15' band at the top of the cliff. How tall is the cliff? Seems almost like a section for a nice run out. If it's typical overhanging seaside limestone, that's perfectly safe. If it's tall enough that is.

Bill Kirby wrote:

Sorry I’m late. I’m moving to San Francisco and it’s kinda taken over my life lately.

 In my experience Hilti will warranty anything broken. You tired to drill into hard rock and the drill bit broke. Hilti has warrantied bits I drilled into rock. I will explain to them what you tried to do and see what they can do for you.

 Have you checked out air powered rock drills? It’s dangerous to drill horizontally with them but I’ve done it. 

  

Sounds good.  I'll ask Hilti when I talk to them.  I'll also post what I find out afterwards.