I've also used a thread-chasing file, a square tool with 8 different sets of teeth that follow the existing threads and recut the damaged ones. Just find the right number of threads per inch on the file, and use that set of teeth to follow the good threads and recut the damaged or flattened ones. Filing the obviously bulged part of the thread down beforehand makes it a lot more likely that you'll be successful with the repair.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!