Removing stuck rear mech
Discussion
Have an old steel frame I’m thinking of converting to a single speed hack. Problem is the bolt to remove the rear mech is rounded off, and so can’t remove it. Not bothered about trashing the mech, but what would be the easiest way to remove it? My thoughts would be either drilling out from the back of the hanger, or just trying to smash the mech up (well, the screw stop bit that stops it turning) and trying to wind it off that way. Any other thoughts?
Has the hex rounded off? If so, I’ve previously undone rounded hex bolts by hammering a slightly oversized torx in and then undoing as normal. Alternative would be to cut a slot in the face (hacksaw saw or angle grinder) and undo it using something to act as a big flat head screwdriver. Or use e-z-outs, but I’ve only used them at smaller sizes, not sure how big they go?
Whatever you do, worth soaking some oil into the thread from the back side to try and free it off I would think.
Whatever you do, worth soaking some oil into the thread from the back side to try and free it off I would think.
If you really do not care about the mech. I would...
- Soak from the back with penetrative fluid for a few days
- Cut a shallow slot in the Allen bolt and mech with a disk cutter
- Use a big screw driver to unscrew the bolt
If it turns into a The Old Man and the Sea type affair as these things often do, I would try then heating it and also hitting it with a hammer.
Edited to add, damn you John P Sanderson!
- Soak from the back with penetrative fluid for a few days
- Cut a shallow slot in the Allen bolt and mech with a disk cutter
- Use a big screw driver to unscrew the bolt
If it turns into a The Old Man and the Sea type affair as these things often do, I would try then heating it and also hitting it with a hammer.
Edited to add, damn you John P Sanderson!
Edited by Moulder on Monday 27th September 22:06
Soak the hell out the bolt area in a good penetrating fluid then you've got a few options most of which (all tbh) will write off the bolt. A bit of heat on the frame bit would help in expanding the hole if you've got a torch of some description.
I'd start with a slightly oversized torx bit and hammer it in then try undoing it, if you have one an impact wrench would be good. You need to break the corrosion holding the two bits together. I have seen people add a bit of rubber between tool and bolt hole to give a bit more purchase.
If that failed a lh drill bit and start drilling the bolt out, this could be difficult but a vice would help here.
The final thing I'd go for, and least preferable, would be hacking the hanger off.
I'd start with a slightly oversized torx bit and hammer it in then try undoing it, if you have one an impact wrench would be good. You need to break the corrosion holding the two bits together. I have seen people add a bit of rubber between tool and bolt hole to give a bit more purchase.
If that failed a lh drill bit and start drilling the bolt out, this could be difficult but a vice would help here.
The final thing I'd go for, and least preferable, would be hacking the hanger off.
Tom _M said:
Thanks folks, some helpful ideas. Thankfully the bolt in the frame is not seized, as moves when you rotate the mech around. Not got an angle grinder, but can try the torx bit or cutting a slot or similar.
I would also think about how you are planning on tensioning the chain if converting to single speed. Many of the tensioners use the rear hanger mount to attach so hacking off would prevent this.To add to the Heat + Pen oil...
You'll also want to use liberal amounts of f and c bombs, then throw the thing halfway across the garden, then hang it back in the shed thinking I'll give the pen oil a bit longer to work.
Once this is done, idly peruse the Internet and within 48hours a new frame will have been mysteriously ordered.
Look at the frame occasionally and think, I really must finish off my single speed project...then smile and pat the saddle on your shiny new frame... Pondering how much nicer it would look with a functionally identical but 5 gram lighter alloy or carbon trinket.
You'll also want to use liberal amounts of f and c bombs, then throw the thing halfway across the garden, then hang it back in the shed thinking I'll give the pen oil a bit longer to work.
Once this is done, idly peruse the Internet and within 48hours a new frame will have been mysteriously ordered.
Look at the frame occasionally and think, I really must finish off my single speed project...then smile and pat the saddle on your shiny new frame... Pondering how much nicer it would look with a functionally identical but 5 gram lighter alloy or carbon trinket.
If the bolt is already loose enough to turn with the Mech, then just get a small chisel. Use it on one of the internal corners of the Allen head and tap it around.
Only if that fails do you have to think about grinders, heat, drills and extractors.
Don't overcomplicate things too early, there's hours of fun you can have before that.
Only if that fails do you have to think about grinders, heat, drills and extractors.
Don't overcomplicate things too early, there's hours of fun you can have before that.
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