Grounding Both sides of a metal nipple between panel and disconnect

[Carultch]

I'll chime in here and say that post 5 and post 8 apply

Did you ask why they have those "teeth" that dig in to the surface of the enclosure, even enough to scratch through painted surfaces so that they make good contact?

Those "teeth" could be there for a mechanical reason. Such as keeping the nut from vibrating loose, like a flat faced non-locking nut would.

Much as you do expect, usually teeth biting through a coating does allow electrical continuity. It probably requires a specific amount of area and/or contact conductance, to meet the listing standard for an electrical bonding application.

Maybe show him some white page listing information on them? (don't know what you will find, but would bet they are listed for bonding.)

Probably what you'd have to do, to convince him. And I'd expect that most locknuts are listed for this application.

 

[Carultch]

Semi-unrelated:

I would like to ask, if anyone knows of any sealing locknuts that are built to withstand outdoor corrosion. Most locknuts I see, are zinc-plated steel, which quickly rusts.

I would think that sealing locknuts would be the one application, where you would want a more corrosion-resistant metal by default. Such as solid die-cast zinc, hot dip galvanized, or stainless. The reason you are sealing it, is to block water and moisture, which also contribute to corrosion issues.