Try Hard Die Hard
If you were to replace a rod and you cut one down to the right size to fit what is the best way to cut a new screw driver slot, a nice techy question for you here ....John
A fine saw.
Here's my nice "techy" answer:
For years I did it by cutting the slot with a jeweler's saw and eyeballing the location. It helped to cut a small notch with a Swiss file to start the saw blade. A few weeks ago someone on a repair website turned me onto this Screw Slotter. I bought one and they work great. It's a tool well worth the price if you make a lot of hinge rods. Of course you need the correct size die to cut the threads and the knowledge of how to cut the "shoulder" just above the threads if you are going to make your own.
A bit expensive for a one off. It's probably not that hard to make one out of wood. I have some thin, fine saws that fit the dremmel. I still have a steady hand but two pairs of glasses helps these days.