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A friend has a frame that they've always had built as a singlespeed, but would now like to run geared. When they tried to bolt the mech hanger to the dropouts, they found that overspray of paint and lacquer had fouled the threads. They then tried to clean up with a tap, but unfortunately this has snapped off in one of the bolt holes. Where does my friend go from here?
Two bolts out of three. It’s clamped in in use.
Wondered about that. How does my friend go about successfully cleaning the threads of the remaining wo holes considering the cock up he made of the first one?
You your friend could do a lot worse than getting down to a decent workshop and paying someone to sort out your mess!
If you run a drill from the opposite side, the broken tap will probably unscrew. Even if the thread is damaged, it'll probably be ok if you run a tap through it, it's not under much stress. Worst case would be a Helicoil.
I don't know you could helicoil such a small/shallow hole.
A larger hole with a new thread cut in it would be an option, if the dropout can be modified to suit.
edit - not too much larger, that would weaken the dropout. M4, (at a guess) to M5.
Drill would be the last option for me. Highly likely to wonder off in to the frame. If there's plenty left on it I'd attempt to unwind it with pliers. Grasp it just enough enough to get a good grip but not too much or you might crush it leaving you with less to work with.
As the others have said though it won't be the end of the world as it'll be well fixed with the other 2 and the q/r and axle. Would suggest using a taper tap to start with on the others, plenty of oil, and go very steady, winding the tap in half a turn at most and back out at least 1/4.
Taps are made of hardened steel so they cannot be drilled. Fortunately as the are brittle this is not a rare occurrence to break them and there is a tool to remove them please dont buy from amazon but its this sort of thing
Taps are made of hardened steel so they cannot be drilled. Fortunately as the are brittle this is not a rare occurrence to break them and there is a tool to remove them please dont buy from amazon but its this sort of thing. Second attempt at a link
Ffs. Those are supposed to be links.
Search for broken tap extractor.
Search for broken tap extractor link. FTFY 🙂
If it's a tapered tap it should reverse out fairly easily once it's moving
when your friend was putting it in, did they remember to reverse it out from time to time to help avoid it getting blocked up?
Given the failure with a tap, where I would personally go is Vernon Barker cycles in Sheffield (but other LBS's are available).
It won't be much to sort out.
my friend used a tap chasing tool, similar to this. Presumably not the correct tool fro the job then?
Is your friend the Hulk or do they buy terrible tools?
Only time I've snapped a tap like that was bulk tapping sheet steel with an electric tap.
If I were them I'd pay someone with better tools or fists that are a little less ham 😀.
I’d probably just drift it round with a little punch and a hammer. Won’t take much to get it on the move
Vinny - probably would be fine but you need to be careful with all these tools. If they get galled up, well, you've seen the results.