Ah, a bolted down copper crimp is a lot better than what I was thinking. It might be an idea to use a spiky lock washer to ensure you’re getting contact.
You can also open it up and ground inside from the back of the connector
Yes, there’s a ground path through both the spindle and the machine grounding, that’s where making sure both grounds come back together soon at a ‘star earth’ point such as the three pin outlet comes in to minimise ground loop problems.
However, as Travis pointed out there’s two issues here
- Electrical safety, fat ground wire on the spindle that can’t be disconnected whilst the spindle is connected to power
- Interference suppression through appropriate grounding of bits of the machine
Number 1 is really not optional so 2 has to work around that.