how to remove a stripped allen screw?
A left handed drill bit a little smaller than the thread size. Be sure to run the drill the correct direction for a left handed drill bit. The idea is to drill it out with a drill turning the direction that will tend to unthread it. If it is stubborn and does not unthread during drilling, use a screw extractor on it (the straight-splined versions (a) generally seem to be a better bet than the twist versions (b).)