A "F***IT" moment!

[unfazed]

Grind the stud flat and with a good centre punch punch it as close to dead centre as possible. Buy some left hand drill bits from 3 or 4mm up and using a variable speed drill set to reverse and drill slowly into the stud, it may come out while drilling, the problem with the standard drill bits is that they are more inclined to tighten it while drilling. Take care not to break the drill bit. Go up in 1mm increments of bit as you work. A slow tedious job for a home mechanic