Welcome to the Board!
My initial reaction is that it is beyond repair. The broken piece is part of the cast metal base of the machine itself. I recently broke a part made of cast metal and an experienced welder told me there was no way to weld it because the cast metal would basically evaporate.
But I tried fixing it anyway, and I would try on yours. I used a two part epoxy, a single use Loc-Tite product, and used thin wire as rebar wherever I put the epoxy. The part I fixed doesn't have a lot of pressure on it, and doesn't move much in the machine either, and the machine works (at least for now). The problem with your part is that you can't get any epoxy in the threaded area nor on the "front" where the bobbin carrier fits in, which leaves limited areas for the bonding agent and "rebar".