^^Listen to this guy^^ Some of the AN /JIC and SAE (brass 45*) will screw together, but the flare angle is different, IE 37* for JIC/ AN and 45* for SAE, usually brass 3/8--no.6 are different thread sizes and will not even screw together between SAE and AN/ JIC.
If I remember right, no12/ 3/4 are same thread diameter but different pitch, and they will not mate, either. In any case, neither series is intended to interchange.
