Arghhh!!!

I have an EAI Delux cog that says ISO on it.

I got a Dura Ace 7600 Track hub that Shimano claims is 1.370 x 24tpi.

You would think that the former would thread easily onto the latter.... But nooooo.... It goes on about a 3/4 of a turn and tightens up like it's not the right size.

Should I encourage it with a bit of force or is something wrong here? It is not cross threaded. It turns on easily and squarely.