theres an M8x30 hex head bolt which I broke the head off of stuck in my transmission case mount. there is about one hex nut’s worth of thread exposed on the broken head side. the opposite end of the bolt is flush with the piece it is screwed into, however, it could in principle go all the way out either end. I can drill from the broken end, but not the opposite end.
I have broken off a screw extractor tool inside the bolt already. I (think) I used a 7/64" black and decker removal screw (#3). so it is not like I drilled the bolt right down to the threads. there’s some meat there. I tried heating the bolt by using a soldering iron inserted in the drill hole.
before I destroy the threads with vise grips, I wanted to post here. I am wondering if I can get two thin nuts on the threads, tighten them together, then use that as a head. or some other way to install something to grab onto on the threads. another thought is to epoxy something onto the broken end. meanwhile, the bolt is soaking in penetrating oil.
I am not enthusiastic continuing with more screw extractors because drilling will be more difficult now - though of course I might have to do it.
if I ought to take a pic, if my description isn’t good enough, let me know.