dusty wroteActually, you are absolutely correct and my assumptions may not apply at all to the ER. To rely on mechanical interconnections (without verifying their effectiveness) for electrical shock protection would not be wise.
However, I still doubt that extra grounding is required for the ER to be safe.
I agree from a 'practical' viewpoint, but, this is about safety(prevent shock) and a method(grounding) to provide protection against it.
The measurements though informative, are not sufficient to provide protection against any faults(electrical) no matter how remote their possible occurence may be. Multiple 'possible' conductive paths are better than 'one' since the multiple paths must all be compromised to create a 'hazard'. However, we are discussing a safety 'issue' and therefore probability is only relevant if not Zero.
The mounting of any device in which a fault can occur on a conductive surface should be included in any attempt to preclude electrical shock by 'grounding' all exposed areas of those conductive surfaces.
All this rambling is relative to as we understand the issue today. When the 10 e/r was produced NONE of this was a concern(not universally accepted anyway).
Since the linecord terminates on the switch(recommend both white(neutral) and black(hot) wires be terminated one on each pole of a two pole switch). The wiring to the motor then is run from the switch to the motor. A common attachment point (through hole with nut(s) and lockwashers) on the headstock of the linecord and the motor 'jumper' becomes adequate. By using two nuts, the linecord may be secured to the headstock first(with nut and two external tooth lock washers) and the jumper secured with two more lockwashers and nut. This allows removal of the motor jumper without disturbing the linecord grounding conductor.
A more practical(and still effective) set of 'hardware' is a tapped hole with a screw tightly inserted, an external tooth lockwasher the closed ring terminal of the grounding conductor(linecord) followed by either another lockwasher and nut or a nut with a captive external tooth lockwasher. On top of that, repeat for the motor jumper.
