A couple weeks ago I had to tap 50 parts with a 2-56 roll form tap. The material was 303, which is easy to form tap. But taps started breaking right away. I use good taps, in this case Balax taps were used with the proper coating for SS. I have tapped thousands of 2-56 holes in all sorts of materials and I hardly ever break a tap. After breaking 3 taps I knew something was really wrong. So I tapped the next part by hand and could feel the torque required was way too high. Upon inspecting the tap under magnification it was obvious that the coating was failing and the tap was galled. I was using a high sulfur cutting oil because the high sulfur content is good for high pressure. Changing the cutting oil solved the problem. I have NEVER had this kind of problem. I don't know why the first oil I used was causing such a problem. Maybe because 303 also has sulfur added? I have been tapping with form taps for over 40 years. I use all sorts of different taps, both cutting and forming, and have tapped many very difficult to tap materials. The smallest taps I have used were 00-96. I didn't break any of them. Anyway, I just though I would pass this along. Eric
- posted
5 years ago