I don't mess around with silver solder for almost anything. It's too expensive and needs too much heat. I use solder clevises all the time and haven't ever had one fail. I just use electrical solder and paste flux. I use silver solder for cabanes and landing gear (sometimes, but not always).

Clean the threaded rod with fine steel wool (not too coarse or it will promote rust).
Dip the end of the clevis in paste flux
Slide the clevis over the rod
Lay the clevis so that the shoulder is resting on a tinned iron
Add solder. When the solder flows, remove the rod and let it air cool.

Don't try to accelerate cooling or disturbe the joint while it's "wet" or it will make a weak joint that will probably crack.