With USAS B2.1 I assume you mean ANSI B2.1, which is superseded by ANSI B1.20.1, which at its turn was superseded by ASME B1.20.1. Do you own a copy of B1.20.1? If so, have you looked in the code? If not, I suggest you purchase a copy, and look for the relevant section. This forum is not intended to do that work for you.