, that advice is something I didn't know, and is the type of stuff that makes this site great. The experience of others for those of us that have not experienced it, or did not UNDERSTAND the problem when we did experience it. thanksOften if the back side of a through hole is at an angle instead of perpendicular, the drill or tap will break when they break through.
Er, I don't know this personally, you understand. A little bird told me. That's my story and I'm sticking to it. And it's worse with carbide than with HSS. [drops a shop rag casually over a small box on the bench]
You can often avoid broken taps or drills by making a small cut or spotface on the back where the tool will break through, so it come out on a perpendicular surface. Then there aren't any asymmetrical loads on the tool.