I'm sorry Time-ex if you smell a rat, as a time served mechanical fitter I was genuinely curious about non standard threads used in the aviation industry (at least non standard as far as my profession goes). It may well be basic aircraft engineering knowledge, but to someone of my background it is fairly interesting. I've spent many an unhappy hour either grinding tools or stood at a lathe machining threads of all descriptions most of which don't in the Zeus book. So fear not, a BA TMG rep is not on to you.
If this thread is so fragile that is not able to withstand the odd discussion going off on a tangent I sincerely apologise I will refrain from posting on this thread again.