On Tue, 11 Jun 2019 06:53:44 -0700 (PDT), Mark
wrote:

On Sunday, June 9, 2019 at 8:00:52 PM UTC-5, Terry Coombs wrote:
* When is it necessary ? I've just replaced the panel out in the shop
(aluminum buss bars on the old one were giving problems) and I have a 3
wire service run out there . At this time the only place the neutral is
bonded to ground is in the meter box . It has been suggested to me to
bond them in the main panel too ... but that seems redundant to me ,
they're only the thickness of a piece of plywood apart . I have
considered installing a ground rod at the new panel but am concerned
about the potential for ground loop currents .

--
Snag
Yes , I'm old
and crochety - and armed .
Get outta my woods !

And all this assumes that the three wires are NOT in a metal pipe.
In which case the "metal pipe" - aka conduit - IS the ground - both
contiguous to the panel (hopefully) and "real ground"