The first motor I ever put rings and bearings in, the owner bought me "all" the motor overhaul tools...A ring expandor (like the one pictured) a ring compressor, a ridge reamer, and a click style torque wrench.
I probably used the expandor on the first 3 or 4 motors and then just started putting the rings on by hand. Its probably sitting in one of the seldom opened drawers in my tool box, I haven't done motors for years. I could probably be persuaded to separate with it, should anyone feel a need to own one. Gene