Had to machine a big roller for a taper lock bushing. Originally this was going to get a different form of mechanical shaft lock, but was changed to a taper lock after I had already machined the bore out to nearly the bolt circle of where the locking threads needed to be.
On a cnc machine I could have thread milled the half threads, but my shop is all manual.
My solution was to finish machine the bore of the roller out to the minor diameter of the taper for the bushing, and then I machined a plug that had a couple tenths of clearance so it was a nice snug but still hand fit in the bore. I was able to spot face, drill, and tap very easily and end up with nicely half threaded holes with no drama. Then I setup back in the lathe and machined the taper to size for the bushing.