Jammer - I had a similar issue, ordered an adaptor for Paashe air hose to fit a Badger AB, it was aftermarket. The thread pitch was very inaccurate, it did not want fit on the airbrush, but screwed onto the airhose just fine.
Friend Don Wheeler sent me an adaptor that he picked up from Coast Airbrush, same thing, bad fit. He went back for another and had counter guy check for good fit. Same thing, won't fit Badger AB. Guy took off for a minute, came back with a re-tapped fitting, worked OK.
After market Asian stuff is often poorly made, now I just order from manufacturers on this side of the pond.
Patrick