Locknuts for bonding History

[fritts]

Does any one know when the bonding of metal raceways was first mentioned in the code, especially the acceptance of the locknuts in 250.96.
Having a dispute on a building unknown age (really old) with metal raceways some installed with locknut on one side metal bushing on the other side.
Thanks in advance for any input.

 

[Buck Parrish]

Here's a quote from a book called Electrical Contracting author Auerbacher, Copy right 1908
"Boxes used in concealed work in fireproof buildings are fastened to the conduit by means of a locknut and bushing, and wherever a conduit terminates the bushing must be used"

It goes on to mention the "two wires in the conduit". This leads me to belive the conduit was being utilized as a ground. My collection of NEC books only goes to 1947.

 

[480sparky]

The bulk of the language of 250.96 goes back to the 1971, where it appears in 250-75. Similar language appears as far back as 1953 as Art. 2574

 

[infinity]

A metal bushing and one locknut would still be code compliant today.

 

[R Bob]

Anybody ever seen locknuts spot welded to the enclosure?
I've seen this in older bldgs. on service equip.
I suspect that grounding bushings took the place of this method.
Any background on this?