Any suggestions for removing a rounded 8mm allen bolt?

Head is recessed into crank arm so can’t grip it with anything

You could try something like THIS. I failed to remove a bolt from a set of middleburn’s,see picture, the other week and had to hacksaw through them.

1.Hammer a star drive into it.
2.Easy out.
3.Hardened drill bit.

Drill it out?

lipseal hopefully it won’t come to that!

I’ve resorted to tack-welding a cheap allen key in the bolt head using a mig welder when all else has failed, any decent garage could do it in a matter of minutes if they’re not busy.

Fail.

Tried drilling bolt out but unfortunately my drill only goes up to 13mm which is not sufficient, so i’ve went straight through and no joy.

Other than getting a bigger drill are there any other suggestions?