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What I'm doing: taking rounded granite stones and cutting the bottoms flat with an angle grinder and drilling 2-3" the other side for a flower, pen, etc. (3/8")

What I'm using: Bosch multi purpose drill bit (3/8") and a Makita 6A 5/8" hammer drill

Question: It seems like it's taking forever to drill the hole. Is the hammer drill or bit not suitable for the task? I've been at it for about 10 minutes and I'm about 1/2" into the rock: is this normal?

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Definitely using the wrong drill bit. You should be using a masonry bit, which is designed for drilling into concrete, masonry, and stone. It has a different tip than a regular wood/metal bit.

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  • Should not use a masonry bit for granite. Most granite pieces have rather delicate fissure lines and the heavy vibrations will crack it. Should be using some sort of hole bit for doing this. If using a masonry bit it should be extremely thin.
    – DMoore
    Commented Dec 4, 2018 at 15:55
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I have been drilling 1" diameter holes to a depth of 6" in solid granite. I have been using carbide tipped SDS MAX masonry bits in a Makita HR4013c SDS drill. These holes are drilled in 50 seconds. I am drilling the holes to prepare for splitting the rocks, using feathers and wedges. I have not tried diamond tipped bits yet, because the carbide drills are cost effective for my use.

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You should be using a diamond wet hole bit. There are expensive ones which you do not need this unless you are doing this daily. You can get one for much less at the big box or cheap hardware store.

You don't need to have a wet drill but someone spraying water will help - my son uses a spray bottle and keeps squirting while I cut.

Also you do not use a hammer drill. You are lucky your pieces haven't cracked.

Only other tip I can give is you need to go in a a slight angle and straighten it out once you get a solid footing on one side. Practice makes perfect.

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    Note that there are masonry type bits with a diamond head on them. They can do rough cuts in granite if you don't care about a little splintering.
    – DMoore
    Commented Aug 23, 2013 at 21:22
  • Alright, different drill bits. For a 3/8" hole, about 3" deep, how long should I expect to be drilling?
    – David L. Hakim
    Commented Aug 23, 2013 at 22:57
  • A very long time. At least many minutes. Drilling through rock is slow and tedious. You are basically grinding the rock into dust. Water helps prevent burnout, but patience is the most important ingredient.
    – bib
    Commented Aug 23, 2013 at 23:37
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    If you have a really really good bit a countertop slab at 3cm - about half of yours takes about a minute. So maybe 2 mins given a good bit. Non-diamond bit - 10 mins at least.
    – DMoore
    Commented Aug 24, 2013 at 3:24

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