On the subject of miniature nuts and bolts. I have a friend who
molded a size 1-72 (male thread about 1.8 mm. outside diameter)
nut and bolt which he would then cast in sterling silver and use
as a design and structural element in jewelery. I saw these about
8 years ago but I remember being impressed by the fit and
strength of the threads although I don't believe we tightened
any past the stripping point.
If you find the pieces you want in brass or steel and want them
in a precious metal try molding and casting them.