Babbitt or solder for permanent fillets in steel molds?
So I'd like to make reuseable steel molds for casting glass terrazzo concrete counters. I usually use a melamine deck and 1- 5/8" melamine rails hot glued down to form a one piece mold to cast the concrete upside down. Where the mold walls and deck meet I've been using plasticine clay and a 3/8" ball bearing to form a nice round over on my edges.
I'd like to move away from the melamine and use 14 gauge steel for my deck and rails. As for the clay I'd like to switch that material to Babbitt or solder so I don't have to reclay after every casting. My thought to form the material is to silicone a piece of round stock steel on the outside of the deck and rail to hold it in place. Then, pour the molten Solder/Babbitt into the void. Once the metal solidifies, pull the round stock away to reveal the fillet. The question is what sort of release would be appropriate to prevent the solder from adhering to the round over as it needs to be removed? Or would it be better to just globb the metal into the corners and use some sort of spherical rotary bit to machine the final shape? It seems like this should be a doable process but perhaps this is a job for a machine shop?