Drill with a 30-35mm drill bit as mentioned earlier in this thread. Drill several holes at the same depth as the piece you want to blast. An air drill (compressor with a separate rock drill) is recommended as these drills handle stone much better than regular concrete drills. If you still want to use "regular drills" you might find that one hole drills perfectly fine while the next 5 holes barely go down 10mm and the drill is completely worn out. 10 drills can easily be used up on 2 holes 
There is an incredibly big difference in the quality of the stones... Not many rental companies rent out drills specifically for rock drilling.
There is an incredibly big difference in the quality of the stones... Not many rental companies rent out drills specifically for rock drilling.
10 drills on 2 holes? How deep should you drill? Common chisel steel easily lasts 10 drill meters without needing to be sharpened, otherwise you're doing it wrong. If you use bortstål with a drill crown, you drill faster and easier. The lengths of the steel are 40, 80 cm, 1.2 m, 1.6 m, etc., 80 cm steel is called bröstarstål and the usual one used for the initial cut.
The drills that I know people have destroyed abundantly are regular concrete drills that they've used on stone. They've bought SDS-MAX drills and hammer/drill machines. It doesn't work, they can't withstand the heat unless properly cooled! If you use regular chisel steel or similar, it goes much better.
@Henri
Just removed rocks/boulders in a house (down in the crawl space) from the early 1900s where the size varied between handballs to medicine balls.
I usually use a drill that is at least 25 mm regardless of the size of the rock and always try to drill at an angle like a V to make the expanding mortar most effective. If the rock has nowhere to go, the part you want to remove, you can drill forever and use an incredible amount of expanding mortar. The rock should be able to move a maximum of 10-15 cm at a time.
And drill about 2-3 cm deeper than the length of the splitting wedge so you don't bottom out, you can easily manage with a hand sledgehammer if you drill correctly and don't rush.
You can either use splitting wedges, which are very effective and have a low investment cost (remember to oil them a bit before use), and then drill many holes 3-4 at a time and take the rock piece by piece, or you can have a little longer distance between the holes and let the expanding mortar work for a couple of days. If it’s cold outside down towards freezing, a blanket and a heater are recommended.
PS: Use a postal scale for the expanding mortar DS:
Best regards, Niklas
Just removed rocks/boulders in a house (down in the crawl space) from the early 1900s where the size varied between handballs to medicine balls.
I usually use a drill that is at least 25 mm regardless of the size of the rock and always try to drill at an angle like a V to make the expanding mortar most effective. If the rock has nowhere to go, the part you want to remove, you can drill forever and use an incredible amount of expanding mortar. The rock should be able to move a maximum of 10-15 cm at a time.
And drill about 2-3 cm deeper than the length of the splitting wedge so you don't bottom out, you can easily manage with a hand sledgehammer if you drill correctly and don't rush.
You can either use splitting wedges, which are very effective and have a low investment cost (remember to oil them a bit before use), and then drill many holes 3-4 at a time and take the rock piece by piece, or you can have a little longer distance between the holes and let the expanding mortar work for a couple of days. If it’s cold outside down towards freezing, a blanket and a heater are recommended.
PS: Use a postal scale for the expanding mortar DS:
Best regards, Niklas
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It is perfectly possible to drill in granite with regular concrete drills if you use a low-speed rotary hammer. It cannot be done with a regular impact drill. I have probably drilled over a hundred holes with a 20 mm carbide drill from Jula and with their cheapest rotary hammer for 399:- The limitation is not the drill but the drill machine. After about 7-8 holes, the machine gets so hot that it has to cool down.
20 mm expanding wedges can be purchased here:
www.sten-spräckning.se
20 mm expanding wedges can be purchased here:
www.sten-spräckning.se
What you can do is take a measurement from a fixed point to the foundation wall and use it as a "safety measure" to ensure that it remains stable at all times or attach the longest possible level to the foundation wall.
Good luck
Good luck
I have now removed a stone with Jula's cheapest hammer drill and an 18mm concrete drill bit from Biltema I had lying around, it drilled well, harder to hammer with sledge and chisel, maybe I should look at proper splitting wedges if I need to remove another stone later.