> My question to everyone is this:  Do you have the motor rewired
> (and rewire the electrical connections on the piano) to accept
> a three-prong grounded plug from the Holtzer-Cabot Motor, or do
> you leave the wiring the way it is with the original ungrounded
> two wire connection?

This may be a question of authenticity vs. getting sued by the piano's
owner.

The restored instrument is, legally, an electric appliance.  Laws
probably vary, but I believe that if the electrical parts of an antique
are repaired, modern safety standards must be applied.  In the USA,
this would involve a dead-front three-pronged plug whose third prong is
connected through a green wire in the power cord to the frame of the
motor.

I'm sure that everyone here understands the concept: the idea is that
the insulation between motor windings and frame can fail.  This
energizes the motor frame.  If there's a path to ground from the motor
frame through the plugs third prong, the house fuse will blow.  In the
absence of that third wire, a person's body could provide that path.

The exception is for 'double-insulated' appliances, in which the case
or other touchable surfaces are made of non-conductive materials like
approved plastics.

Now, I cannot conceive of a means by which someone could shock himself
on a piano: you'd have to lie on the floor, reach up and touch the
defective motor and a water pipe simultaneously.  (Though now that
I think of it, that's the sort of thing I would have done as a boy.)

But the wood of a piano is probably not an approved insulating
material, so the court could rule that the fatal piano could not be
considered a double-insulated appliance, so the three-prong plug would
have had to have been used.

That's the story as I understand it.  For the USA, the rules are in
the National Electrical Code, which is published by the National Fire
Protection Association.  If I was going to give legal advice, which
I'm not permitted to do because I'm neither a lawyer nor a professional
engineer in the legal sense, I'd suggest that you put the three-prong
plug on the thing and tell the owner of the instrument that your
responsibility for authenticity ends at the electric power input.

Mark Kinsler