Grounding screw requirement [RE-wrenches]

[Aaron Wellendorf]

Joe,

The 2005 NEC 250.8 does not mention thread engagement standards, machine
screws, or thread-forming screws. It requires use of a "listed means" of
connection, no solder only connections, and forbids sheet metal screws.
"Sheet metal screws shall not be used to connect grounding conductors or
connection devices to enclosures."

The "listed means" of connection most likely incorporates thread
engagement standards in the listing testing process, but they are not
spelled out. Probably because if you install the component in the listed
manner you would meet the unstated standard. I would still like to know
where an electrical thread engagement standard is found. I want to
incorporate the standard into our training program. The NRTL's test to
written standards and approve grounding connections and grounding kits
(like Sq D's). Like Brian Wiley said, the standard may be mechanical and
does not appear to be in the NEC.

Thank you for pointing out the non-sheet metal screw requirement. 

Aaron Wellendorf

Joe Felker wrote:
<Look in 250.8 Connection of Grounding & Bonding Equipment
<It permits the use of machine screws or thread-forming screws that 
<engage not less than two threads


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