What is the diameter of the hole in the end of the camshaft that holds the roller, flapper, or brush?
What is the proper diameter of the pin that holds it in alignment?
A new Anco type timer has a smaller hole and pin than the hole in my camshaft. It looks like there is 20 degrees of play! I would feel much better in the pin held it more accurately than relying of the friction of the nut!
A 1/8" drill bit fits the hole in the cam shaft I just checked, so a 1/8" pin should work. I've used a small nail cut short to fit. If you drill the hole in the rotor to 1/8" it should be a good fit with no slack.