Originally Posted by
Road Fan
I'm not a machinist, but I see chasing as a way to clean threads that is not intended to cut new ones. Tapping is a way of cutting new threads. Some people use a tap to try to chase a thread. If the tap does not fit and you "chase" the thread with it, you will have cut new threads.
A tap is the proper tool for chasing threads... but the tap has to fit.
This comes from a guy who has drilled, tapped and chased threads for a living outside of doing the same on bicycles for a very long time.