Originally Posted by FBinNY

Here are WORST case methods, if any of a number of easier methods fail.

1- use a Dremel disc grinder to cut a slot across the bolt, then use a screwdriver.
2- use a dull LH drill which is a close fit to the socket head, to drill into the bolt, if you're lucky it'll seize and turn the bolt out, otherwise, once you've dtilled through the thickness of the head you can chisel it off easily.
3- (should be #1) clean the bolt and a new hex key with acetone (no subs for this, unless you know what you're doing), allow to dry completely. Then superglue the key to o the bolt, wait for a full cure, and turn the bolt out.

It shouldn't come to these, but I offer then to show you that you're a long, long way from a serious problem.