The apex I worked on yesterday, had the clutch side flex pipe broken, and the guy broke the m8 x 1.25 flange bolt. Had to use an angle drill, but could not get what was left of the original bolt out, using ez outs and those left hand threaded screw extractors...had so much torque I broke off the drive but not the extractor.
Possibly was cross threaded when the previous owner had it. In any case, the original m8 has a major diameter around .306 and a minor diameter around .260 (from memory, may not be exact). Anyway, drilled and tapped it for 1/4-20 and torqued the flange up tight. Used a grade 8 bolt. Logic was, if the threads were crossed, we couldnt use them anyway, so would have to go bigger, either an insert or helicoil, or 5/16 - 18. Not sure how much stock is there so went with the 1/4-20..can always go bigger if theres a problem, but I doubt it...its in there tight! In a way, the m8 bolt is acting like a helicoil.
But what a pain in the arse!!
