Just wondering what tool exactly I need to chase / clean my bb threads.

I had an issue where I was swapping BBs between two bikes. One of hte cups threaded completely in no problem, one went half way then got tough to turn, and none of the cups will thread at all on the other bike without being forced, which leads me to believe perhaps I just need to chase the threads.

If anyone knows the tool name and size needed.

84-85 raleigh olympian is the problem bb.