thanks. i should have been more specific to the 5/8" - it is not the threaded fittings (mic stands), but what is found on lighting stands. I've poured over the b&h listings a couple times, manfrotto's page, and a few other suppliers. what i'm looking for is essentially a double ended 'rapid adaptor'. i may just use 2 of them with a 3/8" barrel nut to combine them and trust there isn't too much stress on the threaded fittings. obviously i should get off the 'puter and make one..... but materials aren't always as available as the order button.
like i said, i'm looking to combine shorter poles for added reach. the short pieces i have terminate both ends in the 5/8" stud (lighting fixture).