Really? cut the shaft?! Did you try to drill out the broken part of the set screw? Perhaps it's harder than the surrounding metal? (I think I successfully did this once, that's why I ask)

Didn't we just talk about saving most original parts in another thread?

Lots of coil stops in that pile. They are getting expensive. I try to reuse old ones when I can these days if they are in good shape (though always put new in flippers when rebuilding).