Quote Originally Posted by dsc View Post
Does it matter that the 9Nm torque requirement is only momentary ie. it's static torque needed to get the grinder moving sometimes. Once past that point the thing can be driven with anything as low as 1Nm
Yes, that helps a lot since you just need a motor with high starting torque, so again the motor with planetry gearbox is probably a good bet. The average power whilst switched on is now 1/9th, so about 32W which is more realistic for a stepper motor. The problem with stepper motors is in addition to the motor you'll need a driver which is probably quite expensive.