Try an 'easi-out' first - drill a hole into the snapped bolt then screw in the easi-out anti clockwise (its got a LH thread) the easi out then grips into the bolt and hopefully starts to wind it out - some heat will help as well.Chaps I've been researching this, and to be honest still quite confused.
The situation is that I have 3 out 4 of mount bolts sheared off in the bolt holes.
The repair options that my research has made me aware of are as follows.
1. Left handed drill bits (reverse threaded) to remove the remnant. If successful and bolt hole thread is not damaged, then I would only have to replace the bolts with new ones.
2. If 1 above removes remnant but also strips bolt hole thread, then I would have to Tap and Die a new thread into the bolt hole. Would this achieve sufficient support and allow me to torque to the specified nm?
3. Hellicoil steel insert - similiar to 2 but probably stronger and would achieve required torque.
I have had no practice in any of the above so please any thoughts or suggestions would be most appreciated especially from those that have been through this before.
I bet CJJ could repair this sort of stuff in his sleep.