Last week I sent a desperate email missive requesting information on why a NOS Gipiemme track hub I'd had built up that was stamped "Special ISO" permitted a standard Suntour cog to be threaded on by hand, but allowed that cog to spin impotently across the threads the moment leg power was applied.
Thanks to those who replied, but the correct answer actually came from my local mechanic, framebuilder Bill Stevenson, who is a great source of wisdom, a good friend, and the anchor for our local road riding scene. Like me, he found nothing online, but an old Sutherland's manual revealed that the ISO standard did actually differ from longstanding cog threading conventions. In this case, ISO adopted the same pitch and diameter as that used for French bottom bracket cups. Longtime shadetree mechanics will recall that English cups will thread into French BB shells pretty nicely (the cog went onto my hub like it was buttered), but that they won't stay put in use.
I'm a 195-pound roleur/sprinter and so threadlock isn't advisable, to say the least. We're going to consult with Bill's resident machinist when he returns from vacation, but unless someone volunteers an example from their stash of 18-tooth ISO track cogs (I'm using a 48t chainring on my Masi), I anticipate having to rebuild the wheel with a new hub. Many years in gestation, ISO standards were basically stillborn, so I expect that new build is in the cards. At least I didn't order the tie-and-solder job on this one.
Thanks again for all input.