It seems that Boeing's SRM 51 FASTENER SUBSTITUTION TABLES do not allow *bolts* to replace *rivets* -- and vice-versa. (1) Why is that?
Now, looking at a drawer with several "look-alike" fasteners, it makes me wonder: (2) what features or characteristics allow MS21140/21141 hardware, for example, to be called "bolts" and NAS1919/1921, "rivets"?
And, finally, please notice that there are FAA-aproved repairs within specific ATA-chapters of that same SRM which call for hi-lok bolt/collars to be installed where solid rivets were originally installed (usually for thick double-doublers). So, (3) where do we find substantiation for said substitution when desired for an eventual beyond-SRM repair approval?