Drill it out
You can try welding, but if you broke the lock nut, you probably break the weld... although welding will heat up the lock nut.
Otherwise, buy a good set of drills and a corded drill (you'll be re-charging a cordless every half hour).
There is no easy way.... sorry.
__________________
My Porsche mechanic drives a Saturn.
'98 Artic Silver w/ Tip
|