4th axis as a "poor man's lathe"

[JAZZCNC]

One thing I am disappointed is the noise. I find the servo is quite noisy. I don't know why, but it is not what I expected. Also, the holding torque seems to be a joke compared with the stepper I had, so maybe this servo is far too weak as a rotational axis, where high holding torque is necessary. Anyway, I will finish the project first, before I buy a more expensive and larger servo.

That doesn't sound right to me, that doesn't sound like a true servo but more like a very resonant stepper motor.
Both DC or AC brushless Servo's are very quiet even at 3000rpm. This video I did about electronic gearing shows just how quiet, jump to the 4min and 16min marks and you will see the motor spinning and hear just how quiet. The motor is a 600W AC brushless servo but DC brushless servos are just as quiet.