Fuel Petcock question

Ok,

so I am getting ready to get work done on my peanut tank and want to put in a HD style petcock.

I got the 22 mil stock length petcock bung from bungking and the 22 mil center tap petcock from Lowbrow and they will not mate up. I took out my calipers and the petcock is 21.9mm on the threads and the petcock female to female adapter ring is 20.75mm at the threads the thread count is the same at 1.0 so assuming that the depth of the threads allow for the almost 1mm difference ....


wtf is going on here do I need to get a thread chaser to clean up the petcocks thread since they have been chromed or is there something else going on? One thing that I noticed is that the adaptor ring is reverse threaded on the side that mates up to the petcock itself as is the threading on the petcock.


I was under the impression that Bung King is good as a supplier for these parts so where did I go wrong.

yes I know in hindsight I whould of gone with a pingle petcock but I was buying other stuff at the time and just added it to the cart as well.