Hi, I did a few internal threads today and found that I needed to adjust the value to pitch * 1.3 to get proper crest form.
The insert tip even with my magnifier looks to have no radius (or perhaps so small I cant see) I also checked to see if it really was a 60 degee tip. I've checked tool offset and backlash, all good.
Still I suppose when it comes down to it, if it works don't worry about it.
John