We buy motors from a second hand market. Almost all of the motor's rotors are cylindrical. When i went to manufacture a coupling for transmission of motion from this motor to a shaft. The worker said to transfer power successfully you need a D cut. Other wise slipping will occur. I don't understand then why are the rotors cylindrical in the first place is they cant efficiently transfer motion.
Second option is to do a fix it with a bolt by making a through home, through both coupling and shaft.
Can someone shed some light on this topic.
Thanks.