(1) What can I do to increase the chances that I'll be able to get the nuts and bolts together? When I have everything apart, how can I best clean the filthy, worn bolts without [further?] damaging the threads? Do I use WD-40? PJ1 contact cleaner?
(2) When I say the bolts are non-standard, what I mean is that they have very, very thin heads. They need to be very, very thin in order not to catch on the axle fork while the sprocket is rotating. The heads have hex-shaped edges (in a standard size), but because they are so thin you can't really force them very hard without bending or stripping them. What is the proper way to screw something like this into a nut?
(3) Is there a name for bolts like those with very, very thin heads? Where does a person go when he needs an unusual fastener?