So I had a broken stud in my aluminum head, roughly m8 in size, flush to the head... I tried welding a washer and nut to it to extract it out but it kept breaking off. after 8 tries of this, I decided to drill it out, and I got an extractor to grab on it but it immediately broke off into the hole.
I then tried to weld it again, same story, nut and washed broke off.... Now, the bolt is some unholy mixture of hardened tool steel and now I simply cannot get my cobalt drill bits to even put a divot in it.
What's the next step? I really don't want to pull the head off, my entire build has grinded to a halt because of this one damn bolt. I'm at a loss. I've been looking at getting a carbide bit, or better welding wire? I was using a harbor freight mig170 and some cheapo flux core.

I then tried to weld it again, same story, nut and washed broke off.... Now, the bolt is some unholy mixture of hardened tool steel and now I simply cannot get my cobalt drill bits to even put a divot in it.
What's the next step? I really don't want to pull the head off, my entire build has grinded to a halt because of this one damn bolt. I'm at a loss. I've been looking at getting a carbide bit, or better welding wire? I was using a harbor freight mig170 and some cheapo flux core.

