[Heathkit] HDP 21/Shure 638 Microphone disassembly

[jack m]

I currently  use a Heath HDP-21/Shure Model 638 mics on both Collins and Heath SB equipment.  I want to restore and clean up the mic element screen on one of these, but have not been successful in getting the head cap loose.  So far, I have only attempted this using brute hand strength and without tools.  I assume it "simply" screws off?  Perhaps it is a press fit?  I do have a Sears adjustable rubber belt tool at hand, but have not tried it.  (I also have pipe wrenches and a large vise!)
 
Has anyone ever taken one of these apart?  Any other tips?
 
Thanks
 
Jack  W3RU