Cast posts, if they actually cast successfully, would be entirely
too soft to function well.
Sterling silver posts soldered onto earrings can get annealed,
therefore they can be soft. I used to do production casting and I
have mass produced thousands of cast 2mm-6mm round 4 prong cab
settings with the post attached. I have read where people suggest
twisting the post to work harden them, but when you are doing mass
quantities this is not practical. I do use commercial thicker style
earring posts on the pieces I mold so the posts don’t get too thin
from the shrinkage of molding, casting, and finishing. These parts
were tumble finished with stainless steel shot and I believe= they
were work hardened somewhat. I supplied these to several sources and
I had no problems with returns. I also used them for my store and I
did not have customers bringing them back for repair. My wife buys a
lot of sterling from overseas sources and we have more fabricated
jewelry returned for repair due to cold solder joints on rings,
earrings, pendants, bracelets than problems I had from the cast
pieces I made that we sold to our customers.
Richard Hart G.G.