Quote Originally Posted by lakeroadster View Post
Interesting discussion... I've always just used cutting taps for chasing threads too

Anybody ever taken the time to look and measure a "chasing" tap vs. a "cutting" tap? I'd assume the chasing taps are merely a bit undersize?
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Actually John, tools marketed and sold as "thread chasers" ARE JUST REGULAR TAPS. Most, if not all, are cheap, normal carbon steel and most with only 2 flutes. In fact, the only advantage to using a carbon steel tap is if it does break it is much easier to drill out.

Nobody makes an "undersized" tap to use as a thread chaser. This machinist friend of mine actually had a tool that he made to chase threads in a project that he worked on. It was no more than a hardened steel bolt that had a sharp troth cut into the length of the threads.

If you want to clean up your threads, lube your tap well and slowly run it in. A 3/8 tap WON'T cut new threads unless you cross thread it in. It will cut 3/8" threads just like new.