Bought these as a test while waiting for other diamond core bits. Set a container of water on the drill press platform to keep my part submerged and cool the bit. First used 1/8 base bit. It moved slowly and dug well into the granite, about an inch deep. (Be sure to massage lightly and apply light pressure.) Then I moved on to opalite. Not good. Upon closer inspection, I notice that the shaft isn't quite straight. It wobbles and I believe that wobble is why the opalite breaks right in the middle next to the hole. See fig. Opalite is translucent, an oblique hole is visible. The nickel plating on the 1.25-inch bit from the kit was already peeling off. He again perfectly cut two holes in the granite while being submerged in water. I didn't wipe the inside of the racket and the surface rusted right away lol. For sedimentary rock like river rock or granite I would say they will. Not so much with precious or semi-precious stones. I expect to get more than four holes out of the drill. I also expect to be disappointed when I spend so little on industrial tools. So I'm neutral here. 1/8 bit wasted - garbage. The rest are in various sizes that I will use for future random projects but not on hard rock.
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