Are we talking about the bit that screws into the head or the two flanges that bolt together, or have you got the fancy one that tightens up with that big locking ring thingy?

For the usual Hatori type, I make sure the flange tightens up on the copper washer rather than binding up in the threads and bolt the two bits together with the supplied screws and graphite gasket. I've never used the fancy one??