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Proper FFS moment last night:
I was about to replace a middle chainring on my SLX M672 crankset. The external bolts (holding the big and middle ring together) came out without the slightest problem, but then I realised I also needed to undo the ones holding the granny ring (as the middle ring and the nuts were getting trapped in the tight space).
Two were easy to do, but then another two... The allen key went around almost with no resistance from the bolt! Swapped it for a hex key... The same!
I know that it is 100% my fault and big sin - as I still use the triple crankset, but is there a way of removing these bas***ds without drilling them out? Would hammering in a larger hex work? I'm looking for kitchen-friendly tips, otherwise I'll need to employ someone with a vice and good drill! 😉
Cheers!
EDIT: The tools are good quality, with no wear on them.
I doubt you'll be able to hammer in a larger allen key in but if this happens to me i usually hammer in a torx bit and stick a ratchet on.
Inner chainring bolts are almost always steel so it's pretty unusual to round them so easily. Is it possible that theres some accumulated dirt in the bolt hole that has prevented the allen key from being inserted to the correct depth? Can you try cleaning them out then trying the allen key again?
by the way - as far as I know hex key and allen key are the same things...
the inner chainring bolts are a torx .... so using hex or allen keys in isnt going to work very well .
put other two bolts back in and try again on the other side. failing that grind off the top of the bolt get the ring off ... with no tension youll be able to remove remains with molgrips.
An oversize torx bit on a ratchet might do the job, or an impact driver if you've got one. Heat'll help free them off as well. If you're near SR8 you're welcome to pop round for a cuppa and a borrow of the mahoosive vice (think ex-pit works) and selection of hammers we've got if you're really stuck.
Is there a friendly garage near you that does welding?
Clean it right up, find a small (10mm or so) nut, take it to them, ask them to weld through the center onto the rounded off bit, then use a spanner to extract it, throw it in the bin, clean it all up and fit new ones.
I'm lucky enough to have a workshop and a mig where I keep a couple of classic cars and dick around with them at weekends and evenings when it's not utterly freezing out, and I've had to do this a couple of times. This assumes they're steel bolts holding it in. Sometimes you need to scuff/grind the chrome plate off them to get a good weld (I use a dremel for this).
Probably not useful in your situation, but it's never failed me yet.
I’d think that a screw extractor would do it.
I’d think that a screw extractor would do it.
Just remember that these extractors are hardened, and if they get stuck or break, drilling out is a LOT harder.
If the welding scares you, and you have access to a good drill press (I'd not do this with a hand drill), then you can try to drill the head off and extract using grips and some heat.
if that fails you'll need to drill the lot out and re-tap, probably. Or put a nutsert/helicoil of some sort in. That's why I tend to weld stuff to stuf and try and get it out that way.
Thanks guys! Of course I meant "torx" while typing "hex" 😉
<span style="color: #444444; font-size: 12px;"> If you’re near SR8 you’re welcome to pop round for a cuppa - thanks! But that's about 6-7 hours drive from South Devon I suppose?</span>
I'll try an over-sized torx and see where is that going...