Quote Originally Posted by pepi View Post
It take a different bit to clean up threads, taps are for cutting not cleaning. Here is the bit for chasing the threads. I know it is to late for future reference it is a good thing to know.

ARP 911-0002, ARP Thread Cleaning Chasers | ARP
"Note: These are strictly cleaning taps and are NOT designed to cut thread."

Glad all turned out well and lucky it broke off close to the surface...
OK--I got hammered on another site about using a TAP as opposed to a THREAD CHASER. I have heard the term THREAD CHASER" but never seen a tap labeled as such. Therefore, I consulted with a friend of mine that is a retired machinist for NASA (now is a consultant/trainer for large industrial machine Co.) and over the course of an afternoon got a, hands on, education on taps and dies.

In the world of machinist, where taps and dies are a daily tool, THREAD CHASERS are a joke. What I mean is this. There are no "quality manufactures", Morse, Greenfield, Yamawa, Emuge or OSG that make anything called a thread chaser or cleaner. The ones from APR are cheap taps, not HSS, same as you would buy from HF. The ONLY advantage in using a tap such as this is if it does break you can drill it out as they are NOT HSS (high speed steel) These are the taps that I, normally, use to clean up threads because they are CHEAP, meaning they are not as aggressive as quality HSS taps.

There are other types of taps called roll taps or forming taps. These taps, which can't be used in every metal type, actually FORMS the threads in the metal as opposed to cutting them.

So, don't be fooled by deceptive advertising. If you want taps to CLEAN up a thread, buy a set of HF.