Tap and die sets are a must have when working on anything. I chase the threads on just about every rusty / and greasy nut and bolt for every project whether it be a water pump or a lawnmower.

They can save your ass and money too. On my dads 96 Cirrus, a ham fisted mechanic had done some work to the motor. He ran several bolts in crooked on the EGR valve piping. The thing wasn't even sealed. I patiently took the EGR off re-tapped the threads and chased the bolts and got the thing back together right.

I hate fixing other mechanics shoddy jobs. When you paid them for the work..