A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: David Pike
Date: 2016 Nov 29, 02:33 -0800
Robert Swartz you wrote: I may be wrong but I thought the mount was rivieted to the hull of the aircraft.
The holes are definitely threaded. A 4BA tap is probably a bit loose and unlikely. An M4 tap is too stiff. I have a screw in my toolbox which looks like 40tpi and has an OD of 0.136”dia which gives a slightly wobbly fit. I suspect it’s No6 UNF, except the tips of the threads appear more rounded than flat. I've been informed some mounting manuals talk of fifteen 6x40 holes, so I’m going to buy some No6 UNF screws and try them. I don’t really need 24 for a non-flying situation, around six will do. DaveP