The problem with chasing threads with a thread-cutting tool is the possibility of removing too much metal. Real thread chasers have blunt tips on the cutting edges so they simply iron the flattened or rusty areas back into shape instead of cutting.
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!