Try taking a bigger size allen key and tapping it in with a hammer. If that still doesn't bite drill it out. Or get yourself an extraction tool (fairly cheap and always a handy tool to have)
Theres this tool that has a flat head like a screwdriver on one side and a bolt looking thing on the other side. So you can bang it in so that the flat side bites and unscrew it by fitting a wrench over the other side.
USe this style extractor http://www.toolprice.com/c=b0qPqdQQNkEs3lH4TGndY8U38/product/2896W/12-Pc-Rigid-Screw-Extractor-Set---2896W.html . Half the time when you drill into it with the included left hand drill bit it will pull your bolt out
There's also the ghetto method if the screw head is not recessed. Carefully cut a slot in the screw head with a hacksaw, then use a large flat bladed screwdriver to unscrew it.
But using extractors is the better method, as people have already stated.
how would i drill it out? and whats an extraction tool?
thanks
You drill into the center but you don't want to drill any bigger than the thread size. Most of the time the head will pop off and you can just grab the threads with pliers. An Easy out or Screw Extractor would probably be what you want to try first though.
just take out the starnut by taking off the forks and then putting a length of tube that's just smaller than the inside of the steerer tube (a pipe or a but of old climbing frame or something) in the steerer tube and hitting it with a hammer. Then get a new starnut and allen head screw from your LBS
Just to make sure we are all understanding you here: It is your top-cap bolt and the head is stripped not the threads, correct?
If this is all correct, then the bolt head sits in a recessed hole therefore the head cutting method will not work. The easiest and cheapest way to do this is with an Easy out kit, like the one I and another guy posted a link to. If your really lucky one of the easy outs may wedge in the existing hex hole with no drilling. Or you can take it to your LBS, If it was my shop I'd charge ya about $10 for 10 minutes of work.
Torx bit. Get one big enough to fit into the corners of the old Allen socket. Hammer it in straight and gently torque until it loosens.
If that doesn't work and the Torx bit just chews-up the bolt head even more... get the drill out. If you're careful you can drill just the head of the bolt off leaving only the threaded portion, at that point everything should come a part, then clamp the threaded bit with Vice Grips and undo.
I always wonder about people... if you are the one who got it that stripped in the first place and THEN had to ask how to fix it... well then I wouldn't recommend drilling or using hacksaws on your stuff. (There are always exceptions to this, so don't take it personally)
It would probably be better to get someone who knows what they're doing to remove it. Ask to watch though so you can see how they do it.
i went to my LBS and they couldnt help me out, they were going to do the torx screw thing, but didnt want too incase they cause more damage. im going to give the Extractor tool a go, im pretty sure thatll work. and yes its the top the screw head no the threads. i got the bolt/cap for the headset from a friend and he stripped the hell out of it, i was going to cut into and make it a flat head screw but my dremel broke.