Here is the story. My old wheel was a freewheel. Had a new wheel made up from a Uniglide hub, changed out the housing for that of a hyperglide. I have a 7 speed cassette to install but can't figure out how the dustcap fits. Dustcap seems to cover the threads for the lockring. Anyone know why these two parts are not playing nice?

I can see the logic of the dustcap but is it necessary?