how to convert a mill to cnc?

[Gary]

Dont forget a 3Nm motor will not give you 3Nm, unless it is at zero speed.
The 3Nm is holding torque and the actual torque you will get is dependant on the driver, RPM and Voltage.
You need to look at the torque curve of the motor to determine the torque.
as an example a 3nm holding torque motor will give you between 0.4Nm to 1.8Nm depending on the voltage and speed.