Stormin Mormon wrote:
We'd really like some more details. What kind of a device are you repairing?
How big a bolt, how big a nut, and what kind of bolt? Much, much, more
detail.

The answer is likely to be carbide with diamond grit embedded in the tip.

Hi,
It's so called spline type lug nut on a small Japanese car after market
rim. The nut spline cap broke off(it was hollow tubing kinda thing, not
solid metal) Now the tapered nut is in a recessed hole making it almost
impossible to do anything. Time to put on winter tire/rim and I am
stuck. Out of 5 lugs this one is giving me a big headache. Having almost
no room to do anything, drilling was my idea. Think the El Cheapo lug
was the cause. I was using air impact wrench. I suspect the cap was
partially cracked on the side by road debris or something. It shouldn't
break(shear) off like that. I was even thinking about using welding
torch sacrificing the rim and/or stud. So far no snow yet, so I still
have some time on my side.