Drilling Flagstone
 

I need to drill about fifty 3/4" holes (~2"deep) in my flagstone paver deck. These are the anchor points for my pool cover, they all need to be re-drilled because I had my deck surface redone.

This material is hard, extremely hard. Normal carbide bits barely touch this stuff. Even a 1/4" hole is slow going with my HF 'regular' 1/2" hammer drill. It cuts easily with my diamond saw, but I need to drill, not cut.

I need some way to drill faster, and ideally a bit that can drill all fifty holes. I've looked at diamond coring bits, they get good reviews, but they have a short life. I don't want to burn through twenty drill bits at $30 each.

Soooo, bigger/better drill (e.g. Hilti) and Milwaukee SDS drill bits?

Any other ideas/suggestions?

A couple of good quality Hammer drill bit will do the trick. Bosch or Milwaukee should do. For me, rent a rotary hammer and one bit will blast through 50 holes in no time. Again Bosch or Makita bit that will fit that hammer. I don't have the patient for a hammer drill with that amount or size hole.

I bought a Ryobi 1500 watt rotary hammer drill (inexpensive!) and use good Sutton brand SDS Plus drill bits. This may work for you.

Will a rotary hammer drill crack the flagstone? I think my large Hilti rotary hammer will break the stone. Diamond core will work, keep water flood on it should be able to do possibly all the holes.

I use a variable speed polisher that has a 5/8-11 spindle, works well with core bits, can use a piece of 3/4 ply with a 3/4 dia guide hole in it to help with starting the hole.

It wouldn't crack a 2" thick flagstone. Use the smaller roto-hammer it should be fine. flagstones are soft. Hole saw takes too long.

I've done some trials on leftover pieces, they do not seem to be prone to cracking. On the deck they are 1" thick on a 1" mortar bed, they are well supported, so I think they will be fine.

I have a garden hose ready to go.

Normal flagstone is easy to drill, somewhere between a soft brick and cured cement. These stones are from China, so they aren't the flagstone I'm used to. They are extremely hard. Harder than any stone/concrete I've ever had top drill.

I am going to start by finding a Bosch SDS drill, then buying a high quality SDS bit.

This looks like a very good deal. I've seen a bunch of tools from this place that were 'reconditioned'. They all looked and worked like a new tool.

https://www.cpooutlets.com/factory-reconditioned-bosch-gbh2-28l-rt-8.5-amp-1-1-8-in.-sds-plus-bulldog-xtreme-max-rotary-hammer/bshrgbh2-28l-rt.html

https://www.cpooutlets.com/dewalt-dw5810-elite-series-3-4-in.-x-13-1-2-in.-sds-max-masonry-drill-bits/dewndw5810.html

That size drill should be better at not cracking the stone than mine, the one I have drills through concrete like soft wood but it exerts a lot of impact force and weighs about 22lbs.

We have a one just like it. That will drill thought it like a hot knife through butter. Lots more quarts in that flag stone I assume making it harder to drill.

I bought one of these for a project not expecting much from it. I was pleasantly surprised. I got to use it to chisel up some ceramic tile and drill a hole. For $94 hard to beat if you're not gonna use it every day.

https://www.harborfreight.com/10-amp-1-18-in-sds-type-variable-speed-rotary-hammer-64288.html

This one seems to be closer in RPM to the Bosch but it's also closer in price
https://www.harborfreight.com/85-amp-1-in-sds-plus-type-variable-speed-rotary-hammer-58214.html

I looked at HF, but for me that's a trip across the border, taxes, exchange, etc. Not worth the trouble unless I'm also travelling for work, which I am not. Bu that's what I would buy if it were easier for me.

And despite CPO being a good deal they don't ship across the border.

Plan C is a used Dewalt from Marketplace.

I drilled about 20 1/2" holes in my porcelain tile to mount my car lift with a diamond hole saw.
Using water and not much pressure I had them done in no time and the bit still looked new.

I once made the mistake of buying canadian flagstone for a walk because it looked nice deep grey when wet. What a mistake. Super hard. Sharpe edges. It splits into thin shale layers if just tapped.

Solid plan. That was my plan A until I found the one at HF.

If you don't need it around, rent one for 35-45 bucks a day. Buying one will run what, 150-200 plus unless you need a tool hanging around taking up space on your shelf.

If you do rent one try to find one with lower impact power, less likely to crack your stone. HD does rent a Bosch RH850vc for $87 a day, ouch! That one has 9.3 FT/LBS EPTA likely too much force, the one you listed above has 2.4 FT/LBS. Sometimes the bigger hammer is not the correct tool.

I don't remember what those little bosch is called? I think Bosch Bulldog roto - hammer. They are small and you are correct, large impact hammers will cause a lot of cuss words for that day

I'm the neighborhood tool supply. I will buy one.

What's one more tool, versus stressing over drilling all the holes in four hours?

We need someone like you in my parents neighborhood. Now, I am the tool guy, but only loan to the nice neighbors, and of course, the hot long legged skinny house wife too

What tool does she get?

Most times I don't trust them to a job safely, I just go over and do it. No one gets hurt and I get my tools back.

[QUOTE=1990C4S

Most times I don't trust them to a job safely, I just go over and do it. No one gets hurt and I get my tools back.[/QUOTE]

Lol, yup. Years ago I lent my small Hilti TE17 to friend of mine to drill a hole through a basement block wall for a garden hose outlet, I warned him to really hold on to it, he was drilling overhead and the bit jammed, well his arm got twisted and he could hardly use it for about a year. I don't lend my TE70 ATC/AVR I will go and drill concrete for my friends, that one will turn off if it senses rotary movement.

That TE17 is a excellent little drill but parts NLA, mine still works well after 40 years.