[GreenCameleon]

Yeah, the pulsated DC is causing the meter to get goofy. OK, let check something else. Set your meter back to ohms with everything turned off and unplugged from the wall. Now measure from the Motor common - negative lead and see if it is connected to the motor case. The Plus side should be going to the brushes inside the motor and the negative side should be going to the windings inside the motor. We are just checking to see if the winding a tied to the case. My guess is you will find them at infinite again.

You are correct. The meter showed infinite resistance. The body of the spindle appears to be wrapped in plastic (the meter didn't beep and showed infinite resistance when both leads were attached to it) so I made the measurements from its top, where the conductive material is exposed (its also exposed at the bottom of the spindle). I am attaching a picture which shows the place.

Then check to see if the motor case and your CNC frame are actually tied to ground by measuring between them to the ground lead. You can do all these tests with the power unplugged from the wall. See if you get a reading from your ground terminal to the cnc frame and the spindle motor.

Ok, so the body is wrapped in plastics. I used the same spot as in the previous case, to test with ground and the meter showed infinite resitance. The frame consists of plastic parts and some steel tubes, which are not connected between themselves. Measuring each tube and ground earth terminal of the spindle controller (the screw) also showed infinite resistance.

One more thing lets check the CNC controller side with a measurement. Check between the common - negative side to ground for power going to the CNC controller. Is that 12V common connected to ground?

Russ

Ok. I'll go check this now.