I'll put up a couple of better pictures of the casting setup when I take a break for lunch - gotta get some real work done first! I can show better images of the setup and the cardboard collar at the bolster end, but don't have any of me actually pouring the metal.
The "moulds" were really basic. For the bolster, I took a piece of cereal box, wrapped it tightly round the antler/blade join so that it overlapped the handle by about 1", and taped it in place. Took a pair of scissors and cut a strip about 1/2" wide where the "beak" of the handle would go, and folded it down to become the "floor" of the beak. Then taped on yet another thin strip of cardboard to be the "walls" of the beak. Lots more tape to hold it all in place, then presto. I've actually got a pretty good picture showing this bit, that I'll post here at lunchtime.
The mould at the other end was even more basic. Masking tape right up to about 1/16" away from the edge of the hole, to protect the antler from over-spill. Then I cut a 3/4" wide strip of cardboard, and fitted it so that it sat just inside that tape-line. Taped it all in place, and then reinforced it with 2-3 more layers of tape ...
The moulds could be this rough because I knew that I'd shape the metal once it was cast into place - the pewter's soft enough that this part's easy. All I wanted the collars to do was contain the pewter into a blob, to refine with hacksaw and files once it was cool. Next time, I'll make my "blob" smaller ... live and learn.
Yeah, the threaded rod has a nut on it in the picture. I'd originally thought I'd connect the threaded rod to the tang with the nut, but ultimately didn't want to grind away as much antler as would be required to sink the nut far enough back into the handle. I think you can see, though, that there's a flat spot filed into the end of the rod? I filed back about 1/2" so that the tang would sit flush against the rod, then coated all with epoxy and wrapped with fiberglass. I'd have preferred to braze or weld, but don't have the equipment.
The cavity for about 1" at either end of the handle got filled with pewter. The pewter holds onto some filed-in grooves in the knife tang at the bolster end, and the threaded rod (which stops about 1/4" back from the butt end) at the other. The middle part of the handle is filled with epoxy and chopped fiberglass - put goop into the hole, then wrapped the threaded rod with goopy epoxy/glass, then set it in place ... squeezing in more goop again to fill any cavities I could see.
Was lots of fun to do!