Originally Posted by Paulemery
Its an M8 hex bolt head that has sheared, I was only using a hand Allen key but still managed to screw myself,
- As mentioned above, welding a piece to the head of the bolt will almost certainly get it out.
- The other recommendation of peening the head back into place to grip the Allen wrench can also work in some instances. Unfortunately the comment about these being set with some form of Loctite is probably also correct which means they are definitely going to need heat. And that brings up another problem - enough heat to loosen bolt, but not so much that you cause damage to the bearings. I would suggest you either remove the bearings or be very, very cautious when applying any heat.
- Another option would be drilling a hole down the center of the bolt and then using an "easy out". Though my experience has been this is rarely easy and sometime it still won't come out. If you do go down this path drilling the hole large enough and deep enough to get enough grip is critical. But missing on the size or location will ruin the threads in the hub and you can be worse off than when you started.
- If you have a Dremel with a thin fiber cutting wheel and a steady hand you may also be able cut a slot in the top of the head large enough to get a decent sized screw driver in there. Again, simple enough to describe, a lot tougher to do.
I guess you have to assess your ability and make a call. As for the other ones that aren't stripped yet, I would suggest you invest in an inexpensive impact driver and a high-quality set of bits. Good luck and keep us posted on how you make out.