Drilling rocks

[Anonymous]

OK, I know rocks aren't wood, but they are being used in my latest work. How do you drill them?

There are several different types of rocks, and the only ones I've been able to drill successfully are sedimentary, and really only some of those. I used a high quality carbide bit and a decent hammer drill. Took about 30 minutes to drill 3/4 inches in (deep enough). That included time to allow the bit to cool between drilling sessions. One bit lost its tip within 5 minutes due to over heat. Looks nice stuck in the rock!

I haven't been able to drill into harder raocks, nothing more than a small indentation on the suface after 30 minutes plus of trying.

Sandstone is easy, but the rest are really hard (pun intended!).

Any suggestions?

PS; the rocks are essentially beach pebbles from 2" diameter and large pieces up to 8" along one axis. Not stolen off the beach - purchased from the garden centre...but where did they get them anyway???

 

[jasonB]

You may have better luck with the "Armeg" drills that are made for hard porcelain tiles but I find the small diameter diamond cores work best and they will cope with granite. I got mine off e-bay, £20 for a set of 13 from 10-50mm, treat them as disposable as they will only do about 25mm of porc' tiles before they are blunt.

Jason

 

[jonny boy]

Hello WHW,

Have you tried using a really small bit first? I can't understand why they won't drill. A good quality masonry bit should cope with most types of stone or rock but having said that, I haven't ever tried drilling pebbles so they must be real tough nuts to crack. I'd be interested to find out how you eventually drill them though.

cheers,
jonny.

 

[Alf]

Aren't pebbles the bits of rock left after wear from water, other rock etc? Thus likely to be the hardest stuff... :-k Having said which, we have to drill through granite quite a bit round here and so far our SDS drill has yet to fail.

Cheers, Alf

P.S. I'll just move this over to Off Topic :wink:

 

[Steve Maskery]

Hi WHW
I have an Atlas Copco SDS drill. It's big, it's manly, and I've yet to find anythng that it won't cope with with ease, including reinforced concrete and granite.

I bought it years ago, it cost £350 at the time, but similar machines are available now for a lot less.

Mine also has a special meaning - when my ex-business partner and I split up, it was the only truly joint asset that we had, and we never agreed who should have it. So we share custody. It keeps us in touch with each other, and friends. "Hi Bob, it's Steve, can I have the Big Drill for a while, please?" and vice versa.

I recommend it (the drill, that is, not my ex-business partner!)
Cheers
Steve

 

[Jaco]

Try very slow speed with water to cool the bit off.
Start from small to big.
Good tile/masonary bit.

 

[OLD]

On 'this old house' there rock expert continually removed all drilling dust and his large compressed air drill had a jet of air built in to do this for him automatically so it may be worth a try.

 

[soapy]

I think JasonB is on the right track with diamond cores if you can get one in the right size. There used on site for concrete and cut through the steel reinforcing as well, but must be lubricated with water.

 

[mudman]

I've hung from cave walls a fair bit drilling 10mm holes into limestone to take spit-anchors. Couldn't afford a big 24V jobby at the time so made do with my DeWalt 18V drill. The full 10mm at a time was a bit too much so I always started out small and worked up. Usually a 4mm to start then open it up with a 6mm and finally the 10mm. Always worked well and quite fast.
I haven't tried the same in non-limestone but around here a lot of the houses are made of Beaufort Brick which is hard as granite and will blunt a drill bit just by looking at it. I use the same technique and it works well there too.
It depends where your pebbles have come from but it sounds like you have some particulary hard ones, are you sure it's not flint? Although they should succumb to a decent drill bit and starting off small.

 

[tim]

I have an Atlas Copco SDS drill. It's big, it's manly, and I've yet to find anythng that it won't cope with with ease, including reinforced concrete and granite.

Mine died about a year ago. I still miss it. I'm looking for a decent replacemnet - can anyone recommend one?

WHW - you say decent 'hammer' drill. Do you mean hammer or SDS? I have used (as Alf also says) SDS drills without any probs. And before anyone suggests, it wasn't that that killed my Atlas. That was actually me using it as a breaker for an old greenhouse concrete base slab

If they are super hard then Jason's suggestion is the best one IMO.

Cheers

Tim

 

[Jake]

Tim, I bought this about four years ago, and have abused it to what should have been its death. Including using it as a breaker for about 10m2 of 12 inch thick concrete and it is still going happily.

http://www.lawson-his.co.uk/scripts/det ... roduct=628

 

[Alf]

As it happens ours is a Bosch too, albeit a more drilly-looking one than breaker-a-like, and it's been going for about 8 years without a hitch (everything crossed). Mainly granite, and mainly in the less-than-tool-caring hands of the old man. Maybe SDA drills are the one thing Bosch haven't fouled up?

Cheers, Alf

 

[Anonymous]

Thanks for all the suggestions.

I'm not having a problem with the drill, just the bits. My drill is a Makita pro 1/2" hammer drill, bought 15 years ago for $325 :shock: -- that was a LOT in those days, but it's still going as strong as ever.

I tried an igneous rock at the weekend and a 5mm bit - joke! Didn't even scratch the surface. Pity, as the rock is beautiful. I'll have to stick to sedimentary rocks and just bide my time at the bench - 3-4 mm at a time then a rest. I can't take more hammering at a time than that

I found a DeWalt bit on the 'net which was designed for drilling into granite ledge in New England. Only $10, but 1/2" dia and I use 1/4" maximum. That precludes the diamond drills - don't go that small or smaller. The 1/2" drill is designed to accept re-bar. I'll get one anyway and use epoxy. Worth a try at least, especially for only ten bucks. I also found that those rotary tool things have diamond burr attachments. Might work.

In case you';re wondering, or even if you're not, I'm making sculptures incorporating rocks that look like a bunch of flowers - deep and large wood base (earth) steel rods (stems) rocks (flowers). Gorgeous, and I have 3 commissions already... Experimenting with smaller rocks and patina'd copper rods - not easy as the rocks bend the copper too easily.

 

[Gill]

Here's are some silly suggestions, Brian - how about using a diamond engraving bit such as are made for Dremels? Or having a word with your dentist to see if you can snaffle a used dental bit?

Gill

 

[Alf]

I'm not having a problem with the drill, just the bits.

Brian, an SDS drill is streets ahead of even the best hammer drill for this sort of task, honest. See here.

Cheers, Alf

 

[Chris Knight]

Brian,
You could try a metal (eg copper) rod and diamond paste. The diamonds tend to stick in the soft metal and cut the harder rock. I have used this method in the dim and distant past for drilling glass.

 

[mudman]

I find it amazing that you can't even dent the surface!
Just had a thought though. What are you supporting the pebble on? If you don't place it on a really hard surface such as concrete, a huge boulder or similar, then the underlying support will absorb all the energy and you won't get any penetration at all into the rock.

 

[Jake]

Back to the original question, I think someone mentioned porcelain tile drills, and I thought that was the solution, that or Chris's old school suggestion. Never tried it on rock, but these go through glass and porcelain with ease if watercooled enough. I used a bath of water in a plastic tub for several dozen holes in porcelain and it was just beginning to lose its edge. I can't imagine it would struggle too much even with a very hard rock.

Depending on what size hole, either the arrow type or the core type. The latter gets expensive as you need an arrow type to start the hole, and the arbor and the core drill.

http://www.screwfix.com/app/sfd/cat/cat ... 0&ts=23357

 

[jasonB]

Don't be tempted to use the ones that come up first on Jake's link, scroll down to the armeg ones. BTW the core dits are available down to 1/8" with a bit of googling.

Jason

 

[Anonymous]

The solution was found on Amazon.com -- don't discount them for your tool needs! Two serrated tip titanium bits especially designed for drilling rocks in both SDS and regular hammer drills (specially designed shank). Made by DeWalt, these bits are on Amazon for under $9 (thats about £5 to you and me) yet the same bits on sale in the UK are over £40 each. Go figure, as the Americans would say...