yeah, vice method makes sense. haven’t got a vice though.
charlie, been down that road with a rounded isis crank bolt. bike shops wouldn’t touch it. I couldn’t do it / didn’t want to make it worst. However I then found one that would and they drilled/ punched it out turning it bit by bit.Thought it could have been the end for my lovely retro sunn. Success! Then I ordered some new Raceface ISIS bolts for the old raceface crank and signature bb and guess what they didn’t fit. The pitch of the thread was different, although the diameter was right. Eventually ordered a pair of FSA ones out of desperation and guess what they fitted perfectly. Turns out new RF ones had a strange thread to std….bikes you gotta love them 😉