Rounded hex socket

[2sharp]

So this guy I know was going to pull apart his derailleur cage this weekend to have a ruddy good clean of his jockey wheels.
But, turns out the hex socket on the screw that holds it all together has mysteriously become rounded.
If you were to advise him on how to proceed, what would you say?

[Derny Driver]

Dont proceed Leave it

There is a wealth of ideas on Youtube. "How to remove a stripped hex bolt"

[Thoglette]

Cutting wheel. Or drill.

Duck will explain.

[WyvernRH]

Drill a pilot hole in the middle of the rounded hex in the bolt and use a stud extractor.

[eeksll]

I have heard jamming a torx driver in the head can work. Got nothing to loose if you have the torx tip.

if the screw shows on the other side (like most do on those cages) hit it with a small drill bit from the other side, wont need a reverse bit or extractor. may need to be a bit careful the bit doesnt slip.

make sure they have the spare screw / replacement before removing it.