Exhaust flange stud drill bit?

[wolf_from_wv]

Is there a special tool for drilling out exhaust pipe studs? The catalytic convertor has two studs either pressed or welded into the flange. I need to replace the pipe that connects to this. The studs are not serviceable and need taken out. They are exceptionally hard.

Is there a special tool for drilling them out?

 

[2ndGearRubber]

Stubby cobalt bit would be my choice. If they're pressed in the air hammer is my preference. The rattling can kill oxygen sensor heaters in rare circumstances.

 

[Kev442]

Just found this out this week. Drill bit barely made a dent in ten minutes. Grabbed an air hammer and prayed nothing else would rattle loose on the rusty POS.