Quote Originally Posted by nova_robotics View Post
Do they rely on the spindles discharging static through the workpiece? So for example the bearings in a mill used to machine aluminum will last longer than a similar mill used to machine UHMW?

My router table produces an ungodly amount of static when running. It's basically a Van de Graaff generator. The spindle is 3 phase VFD driven. I'm now questioning whether I should try grounding it or not. I really want to take that spindle apart. Perhaps it could use some conductive grease and a ground strap.
If you are running CNC, the static must not be getting into it or you would crash. I'm sure your machine body is grounded so you should not get shocks from static discharge by touching it.

Static discharge current could be flowing through the motor's shaft, bearings, and into ground. My guess is that if there are sparks, they occur millions of times a minute. If the motor hasn't failed yet, it is probably fine.

Rick