For servos, can it be implied that `Holding Torque = Operating Torque * 2` like with steppers?

Question

I am following a guide that recommends using stepper motors and it has an approximate holding and operating torque. It says that if you don't know the operating torque, it is often half of the holding torque. I am adapting this to use with a servo and I was wondering can this same formula be used with a servo. My servo has approximately 1.98 kg/cm of torque so does that mean that I can estimate the operating torque would be ~1 kg/cm?

A couple of things:

• I know operating torque and holding torque are different. This is just a estimate-it isn't an exact science.
• I know servos are harder to find their location (75 degrees, etc.) than to use a stepper and assume that it worked. I have external means of finding the location.

Answer 1

Holding torque, by the stepper motor definition, is not a valid way to quantify servo performance. Stepper motor torque drops off with speed whereas in a servo it remains relatively constant. (Operating torque is never half of holding torque and is RPM dependent, your guide lied to you).

A real servo will always have a torque (continuous/operating) rating under which it will remain controlled, and a maximum torque rating where it is just running full power.

I cannot imagine ever buying a servo that does not list those two values, (especially considering that most servos will have a fairly substantial datasheet) but a quick survey shows that continuous torque is generally not half of the maximum torque.

Note that hobby servo specifications are so inaccurate they might as well be made up so this question would not apply to them either.