Connect 1-1/2 inch camlock coupling to 1-1/2" NH fire hose thread (NST)

A 1-1/2 inch cam-and-groove coupling has no thread of its own, so it reaches a 1-1/2-9NH (NH fire hose) port through a same-size threaded camlock adapter: a Type A male adapter or a threaded coupler carrying the 1-1/2-9NH thread on its back. That thread is a straight (parallel), 60 degree form of 50.55 mm major diameter at 9 threads per inch and seals rubber gasket in the female swivel; the cam end then mates to its opposite 1-1/2 inch camlock half.

The 1-1/2 inch cam profile and the 1-1/2-9NH thread are two separate choices. A correct 1-1/2-9NH back thread still leaves you with the wrong front if the half you mate to is not the matching 1-1/2 inch cam type, so confirm both the size and the A-to-F type before buying.