Drilling Granite Boulder

[Larry Fox]

The area where I live is riddled with large granite boulders and my yard is no exception. Most of them you can just see the top of them in the yard and given the curvature you can just see that it is the top of something the size of the Rock of Gibraltar. Those I am leaving alone. However, there are some which I have dug around which are of manageable size - largest about 1/2 the size of a good sized mid-70's Buick. They are all solid granite and I want to make big rocks into smaller rocks so I can get rid of them. My plan is to drill them and use wedges and feathers to split them. I did a test last weekend and it works famously - with one caveat. Splitting is not the problem, drilling the holes is. I was using a BIG roto-hammer with a carbide bit and after about 20 holes the carbide smoked off the end of the bit and I was sacked.

Does anyone know of a good way to drill holes in granite? The holes only need to be 3/4" x 5" deep. I can buy the bits for $26 each online and have ordered 7 of them but I would like to avoid having to smoke the bits if I can avoid it.

I talked to Hilti about it and they recommend a diamond core bit. The bit is $180 and they estimate it will last 100 holes. Well, the bits I have been using last 20 holes and cost $26 so smoking carbide bits is a more cost-effective way to go but it seems there has to be a better way. I can't be the first person who needed to drill a bunch of shallow 3/4" holes into granite.

In case you are wondering, I am not looking at blasting them because it would be REALLY expensive and I don't think it would go over well with the neighbors.

There is also expanding concrete (Dexpan for example) but I am concerned about some of the ingredients and my well. Also, you still need to drill holes.

Thanks in advance for your time.

[Todd Burch]

Did you use water to cool the bit as you drilled?

[David Weaver]

People probably all use diamond bits now, i would just bite the bullet and go that way.

I would assume that the drills they used in the past may have been a consumable bit of moderatley hardened steel with injected loose grit. I grew up on a hill that was mined for granite and all of the rock there had very neatly drilled holes in it, and i doubt they did it with diamond or carbide.

People have cut very hard things practically since the beginning of time by using abrasive slurries. Bet the only thing you can find now is diamond.

[Greg Portland]

Would a large excavator-mounted jackhammer work (to split the rocks)? I'm wondering if the total cost of the project (time to split, remove, cart away) would make renting a big excavator for 1/2 a day worthwhile? This is assuming it could split the rocks in 1/2...

[Rich Engelhardt]

You could always use a star drill and a 4# sledge.
I used one once to make a drain hole in the concrete loading dock at work.
It took me a whole Summer to make a 3/4" hole through the 12" concrete pad, working an hour here and an hour there, all day long.

Hey, it was a part time Summer job & being outside beating on a star drill beat being inside (no A/C) stocking shelves...

Seriously though, Greg's suggestion make the most sense.

[ray hampton]

too bad that you can not heat the rock and pour water on it, I never try this but someone publish the information

[Larry Fox]

Thanks for the replies guys.

Todd: No but I plan to give that a whirl when the new bits come in. That thought did dawn on me as the second bit emerged with it's tip burnt off. Not sure how effective I can be in keeping the very tip in water though.

David: I would definitely go the water-cooled diamond core bit route if they could give me either a better service life or cheaper price. As much as I hate to cook the first inch of otherwise perfectly good bits the math works out in favor of doing that.

Greg: The same thought has occurred to me and it might be my next option. There is a guy down the road with a backhoe that I might pay a visit to and see if he would hire himself and his machine out for a couple hundred bucks and a case of good beer if I would rent the hammer. Might just be worth it.

Rich: Aint happening. Given the amount of holes I need to do I would either move or learn to stop worrying and love the rock.

Ray: I have read about that and I have to confess that the little kid in me REALLY wants to try that. However, I don't want to burden my kids with having to offer that as the way their old-man met his end for the rest of their lives.

[Kevin Bourque]

Larry,

When I read your description of the boulders in your yard I thought to myself, "that sounds a lot like my yard" Then I saw that you live in Glenmoore. I live in Glenmoore too!!!

Take Creek Rd. and turn onto Devereux rd. After you pass the school you will see farm fields on the left hand side with boulders the size of trucks. This is my obstacle course. Most of them were moved into those piles by Amish farmers 150 years ago.

PS. Are you lubricating the drill bits with water when you are drilling the granite?

[Jason Roehl]

I, too, have heard of the heat-and-water method. I would think that an oxy-acetylene torch would do the trick nicely--as I recall, all you have to do is heat a narrow band around the rock then dump water on that spot--it will split in two. I've always wanted to try it...

[Greg R Bradley]

Specifically, what Rotary Hammer and what bits?

Diamond core bits are used on completely different tools AND for what you are doing, you don't need a core inside the hole. Yes, a diamond core bit on a mounted drill press is probably the only way that granite counters are drilled on site. That is completely different than what you describe.

BTW, a bobcat mounted breaker would be pretty useless against boulders that size. I wouldn't even try that and we have one in the yard.

I'm more familiar with concrete but we have found that the really large Rotary Hammers don't work as well with smaller bits. One of the reasons that we have 5 different models on hand. Is this a 2+ inch model?

If you need 3/4" holes and the RH is too large to be optimal, we have found the Bosch HC5030 type bits to work well.

[ray hampton]

I, too, have heard of the heat-and-water method. I would think that an oxy-acetylene torch would do the trick nicely--as I recall, all you have to do is heat a narrow band around the rock then dump water on that spot--it will split in two. I've always wanted to try it...

I help to clean land of its brush when I were preteen and the sound that rocks make when they explode from the HEAT speak volumes of the speed of flying rocks

[Sam Murdoch]

I did just what you are doing a few years ago. Took out a chunk of granite ledge in my driveway. Use carbide tipped bits with a Makita hammer/drill - borrowed - it was a big beast about the size of a small jack hammer. Bored a dozen 3/4" holes over 2 weekends and filled them with the Dexpan. Split the thing apart pretty nicely but was lots of work. I had some issues with buying the Dexpan - some web site was selling something that was a copy cat . came with instructions that read like Chinese and required much more care in handling. I never used it. Found the correct stuff and used that. Wish I had the info to pass on but it is all long gone - so this is just a cautionary tale. The Dexpan worked great but there was lots of work before and after.

Here are a few shots: 241538 241539 241540

[Myk Rian]

Would a circular cement saw work? Get a kerf sawn, then wedge it open.

[Larry Edgerton]

I had a house with the same problem. I bought 6" of topsoil after wresseling a few out of the ground.

Larry

[Jason Roehl]

I had a house with the same problem. I bought 6" of topsoil after wresseling a few out of the ground.

Larry

Now if you were in this corner of the world, Larry, you could have "WRASTLED" them out of the ground! ;)

[ray hampton]

Would a circular cement saw work? Get a kerf sawn, then wedge it open.

the rock quarry use a circular saw when they mined granite or marble if I not mistaken

[David G Baker]

When I was a kid on the farm we would dig under a large rock, build a fire and let it burn for hours keeping it supplied with wood to keep the flame high. We would then add water to the rock and it would split into a manageable size. I remember that it took over eight hours to reach the right temperature for cracking. The neighbor used dynamite on his rocks but this was back in the day when dynamite was available to the public.

[Larry Fox]

Guys, thanks for the replies. I looked into the Dexpan and it is certainly interesting but I read the MSDS and it had some stuff in it that caused me some concern for my water well. Also, you still need to drill holes. Sam, unless I am looking at it wrong or your feet are really small those holes look to be bigger than 3/4". When I was reading about Dexpan I thought they recommended a 1.25" hole and a pretty deep one.

The fire approach is probably a non-starter. Around where I am, if there is a fire burning for 8 hours there had better be a pig in the pit, beer on ice and invitations out to the neighbors stating an approximate time for dinner. Otherwise, they get a little cranky.

Greg asked about the hammer I am using. It's a Bosch 11245-Evs. The bits I am using/abusing are the ones you mention - hc5030. They are good for about 20 holes as I mentioned. I talked to the guy at Hilti about the core drill / bit and he said that the core is pretty easy to get out - you just lever it sideways. I can rent a hand-held, liquid-cooled Hilti core drill but the daily rental is way higher than the roto-hammer. That combined with the cost of the bit drives my per-hole cost much higher than just smoking the hc5030 bits.

I think I am probably stuck just using the carbide bits and trying to extend their life by running some water over them.

If anyone has a use for hc5030 bits with the first inch cooked let me know as I will have some on hand for you. :)

[Sam Murdoch]

Guys, thanks for the replies. I looked into the Dexpan and it is certainly interesting but I read the MSDS and it had some stuff in it that caused me some concern for my water well. Also, you still need to drill holes. Sam, unless I am looking at it wrong or your feet are really small those holes look to be bigger than 3/4". When I was reading about Dexpan I thought they recommended a 1.25" hole and a pretty deep one.


Yeah, you are right - actually on both observations :) - but the holes were 1-1/4" and as deep as 12". They were a lots of work!! Don't know your proximity to your well but my experience with the Dexpan was that there was no runoff at all. I poured it in the holes and that is where it stayed. NO MATTER - my project was one piece of ledge and it took me many days of concentrated effort. A real project. You obviously know that the more ground you can pull away from your boulders the easier they will crack - however you do it. Good luck.

[Peter Kelly]

http://www.hilti.ca/fstore/holca/editorials/generic/Block1/L1/DSHlarge.jpg

Will make short work of demo-ing those boulders.

[ray hampton]

why not use the weather help with breaking the rocks , drill the holes and keep water in all of them , wait for freezing weather to expand the ice

[charlie knighton]

some of the skills that they used in the mountains of Peru in 2000 BC would be helpful, see history channel

[Greg R Bradley]

Rotary Hammer is almost certainly too large for your job.

We limit use of a 11245EVS to bits 1.25" and larger. The drilling face of a 1.25" hole is almost 3 times the size of a .75" hole. I'm also thinking granite may be harder to "hammer" than concrete that makes this problem larger.

A Rotary Hammer drills with the "hammer" part. It rotates to find the next spot to hammer and so the flutes can pull the waste from the hole. Pulling the waste from the hole is why you don't run water into a hole you are drilling. Even though it puts more energy into "hammering" than "rotating", binding a 25 pound drill motor in the hole can still damage your body pretty well. A 5" deep hole would help to minimize that but I don't think overheating is the problem. I think it overheats after the carbide is broken by too much "hammer". If you flush the hole with water, make sure you flow enough to not make mud to bind the bit.

Most 3/4" Rotary Hammer bits have two carbide cutting faces. The Bosch "wild bore" 3/4" has four carbide faces, which helps the bits to live when used in a typical SDS Max Rotary Hammer like my 11241EVS, which has less than half the impact energy of the 11245.

The Makita 711505A seems to drill some items really well but they are hard to find at a reasonable price. I paid less than $20 for the ones I have but most vendors are trying to get $45-60 for them. Dewalt makes garbage for regular drill bits but their SDS-Max bits work really well for some uses. They have a very flat heavy piece of carbide the full width with just a small center tip to keep the hole centered. Those three brands are ALL made in Germany. You may want to experiment with different bits and different drills to find out what works well for your specific use. That is why we keep several different sizes of Rotary Hammers and a half dozen different brands and models of bits on hand.

Try a new bit and drill just a little bit and then look at the bit to see if it is chipping or wearing. If it is chipping, that is too much impact power or too small a hole.

I would try a smaller rotary hammer, several different bits, or drill larger holes.

Caveat: virtually all my experience is concrete, which has granite rocks in it, but may be a bit different. I've heard rumors that pink granite can be really hard to drill, black is easy, and grey is somewhere in the middle.

[Belinda Barfield]

You can get core bits in the 70 to 80 dollar range from companies like Braxton Bragg or Gran Quartz. Cutting wet and keeping the hole flooded will greatly extend your bit life.

[Rich Fennessey]

I don't normally look beyond the CNC/Sign making threads but noticed your post as recent activity on the main page. This topic is near and dear to my heart. I've removed a lot of granite in my back yard and have split boulders. No matter how you do it, it is laborious and/or expensive. I have a 1970's Atlas Copco Supra Cobra drill/jack hammer, it is a predecessor of the Pionjar 120. It uses a standard 1 3/8" diameter bit and it blows air through it to keep the hole clear (probably enhances cooling too). You definitely want a mask when using this for drilling. With a switch of a lever, it becomes a jack hammer. It is also powered by a 2 cycle engine. I had bought mine used for $1400 back in 2000. It doesn't run great now but makes it through 4 holes before quitting. Here is an advertisement for the Pionjar which is a newer version from what I have: http://www.maystrailequipment.com/pages/pionjar.html Last I was looking at them, they were $3600 minimum new. Later I bought a used SDS Max Bosch hammer drill. That was handy for smaller and/or horizontal work. I have wedge and feathers all the way from 1/2" to 1 3/8" and have in excess of $2K invested in rock breaking. I joked with my friends that I was practicing for prison.

Here are some pictures of knocking some granite out. The key is to start a hole so you don't have the ground compressing the rock. You also try to read the grain so you split down the most optimal line. Concrete is very soft compared to granite.

241645241646241647241648

[Bill Cunningham]

If you can't buy dynamite in the U.S anymore, then black powder in the hole will work. Start small and work up til it splits..

[Mark P. Miller]

I don't post often, but I thought this was an interesting and informative thread. It made me go check out the MSDS for Dexpan, and I don't necessarily see anything that's terribly alarming. Any MSDS experts able to chime in?

http://www.dexpan.com/Dexpan_Non_Explosive_Controlled_Demolition_Agent_A lternative_Blasting_Jackhammer_Hydraulic_Breaker_S ilent_Cracking/dexpan_msds_english.pdf