Rob was tapping aluminum with a thread forming tap. Tap broke as soon as it touched the part. It was a thread forming tap 3/8/16. Rob confirmed speeds also hole size. Everything seemed to be correct.
We suggested Rob inspect the broken pieces. When a tap or any cutting tool is coated as this one was, If the tool has a crack already in it the coating leeches into the crack and can be seen on the inner parts of the tap. This was the case - a defect.
How would you have determinded what the issue was?