Stripped chainring bolt took me 4 hours last Tuesday

I was swapping a worn 50t ring on a customer's bike and the last bolt stripped at the head, not the threads, so my usual extractor set just spun uselessly against the recessed hole. Tried drilling it out, then heat, then a left-hand bit, and finally got it free by hammering a torx bit into the hole, but only after I'd already wasted an hour hunting for my angle grinder. Has anyone else had better luck with a specific trick for these flush stripped bolts, or am I the only one who forgets the torx punch move until the whole day's shot?

1 comments

1 Comment

clark.joel23d ago

The torx hammer trick usually works, but next time try a sharp center punch first. Not to drill, but to dimple the bolt head right at the edge, like where the head meets the crank arm. That gives you a bite for a punch angled sideways, so you can actually spin the bolt out counterclockwise without any drilling at all. On stubborn ones I’ve also had luck using a small chisel to tap the outer rim of the head, which breaks the rust seal without touching the threads. The real trick is going straight to that punch move before you wreck the head with extractors, because once those slip, the hole gets wider and your job gets way harder.