Stepper Motor Wiring

I'm getting close to hooking up some NEMA 42 steppers, about 6 amps, and wondering what wire to use and if it should be shielded. Also should I have an extra conductor for motor case to ground as was discussed earlier about servo motors.
I've found some rubber jacket 16-4 and some 16-5 locally as well as some 18-4 shielded with a PVC jacket...not as flexible.
Thanks in advance for your thoughts.
Brad


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