Originally Posted by Biker Pete

I don’t have one. But I’ll ask a friend who’s a tool hound. Possibly using an impact wrench with an allen wrench that has had the end ground completely flat (my two 6mm allen wrenches have the edges ever so slightly rounded right at the tip) as suggested by oneclick will do the trick. At worst, the bolt head aperture will be buggered beyond use and other more destructive methods like drilling will be the end result. Either way, once the stem can be removed, I’ll need a new draw bolt and wedge (or a completely new stem).