Help needed - Rounded allen/hex crank bolt

[mattbrown]

any ideas how to get one out when it rounded??

 

[kaiser]

Can you get access to the bolt head i.e. can you use pliers or mole grips?

Do you have any imperial allen keys? Sometimes a size up can 'fit' and grip whats left of the hex.

What type of material is the female part?

Since your asking I take it you don't have easy outs or screw extractors?

Can you get access to drill?

 

[mattbrown]

no, but i should be able to grip the bolt from the outer edges, its one of those shimano ones, with the plastic black ring around it, so should be able to prise it out

 

[stew-b]

how the hell did you manage to round it!!

 

[monsterfatuk]

I had the same problem with my xt levers,,smaller scale i know,, but it was as if the 5mm allen head was 5.1/4 and not deep enough even though it has not been undone much.So got an old screwdrivers and tapped the bolt around half a turn until i could undu it with the key,you can do it with your crank bolt as long as you dont want to re-use it
Far quicker than using an easy out

 

[one-eyed_jim]

If it comes to it you can always just drill the head off. That'll relieve the tension on the bolt, and you should be able to extract the stub with pliers. Go in carefully with an 8mm drill bit. There's enough clearance between the various components that there's not much risk of damage.

 

[dyna-ti]

Drilling it out is ok ,if you can do it accurately,i wouldnt attempt it unless it was the VERY last option,and even then i'd only use a pillar drill
the option i would first take is to try to create a slot [using a dremel or such]
just a couple of nicks is the edges opposite each other,to get a slot screwdriver into
apply the most pressure downwards as you try to turn it
if you suspect it is binding in any way, try tightening it a little first before trying to unscrew it
Are you absolutely sure its the bolt recess thats rounded and not the Allen key?
grind a little off the length of the key

 

[spudgun]

Bash a flat screwdriver into it ,stick out your tongue and grunt as you twist it.with mole grips

 

[dyna-ti]

support the other end of the b/b with a block of wood ,if ur hammering or the frame will bounce all over [may get scratched ]

 

[Err]

Hammer in a torx head of the size up.