do not ground something using a SHEET METAL screw

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#7965 - 01/15/11 04:08 PM do not ground something using a SHEET METAL screw
Nick Sasso Post-A-Holic Member Registered: 11/08/01 Posts: 1451 Loc: West Palm Beach	WHERE is the language that states you cannot ground using a sheet metal screw? I am a bit rusty and I can't seem to find it. Or was this language removed? Which codes would you use to enforce this? _________________________
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#7966 - 01/15/11 05:01 PM Re: do not ground something using a SHEET METAL screw [Re: Nick Sasso]
Ruben Rocha Senior Member Registered: 05/24/00 Posts: 767	250.8 in the 2005. Last sentence. But it pertains to enclosures. Problem is they really don't expand on what is really approved other than sheet metal screws are not allowed. So 1/4-20 bolt is okay? Also don't tell me that a green bonding screw(listed) is okay to bond a 4/0 lug to something. It will never hold. Old school taught me that the sheet metal screws which have a coarse thread do not allow a good contact surface,where say a sae thread provided more contact area.
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#7967 - 01/15/11 06:14 PM Re: do not ground something using a SHEET METAL screw [Re: Nick Sasso]
Bryan Holland Secretary Registered: 10/05/04 Posts: 1622 Loc: City of North Port	2008 / 20011 NEC Quote: 250.8 Connection of Grounding and Bonding Equipment. (A) Permitted Methods. Equipment grounding conductors, grounding electrode conductors, and bonding jumpers shall be connected by one of the following means: (1) Listed pressure connectors (2) Terminal bars (3) Pressure connectors listed as grounding and bonding equipment (4) Exothermic welding process (5) Machine screw-type fasteners that engage not less than two threads or are secured with a nut (6) Thread-forming machine screws that engage not less than two threads in the enclosure (7) Connections that are part of a listed assembly (8) Other listed means The language specifically prohibiting "sheet metal screws" has been removed from the code. _________________________ Bryan P. Holland, MCP
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#7968 - 01/15/11 07:14 PM Re: do not ground something using a SHEET METAL screw [Re: Bryan Holland]
Ruben Rocha Senior Member Registered: 05/24/00 Posts: 767	Originally Posted By: Bryan Holland 2008 / 20011 NEC [quote] (5) Machine screw-type fasteners that engage not less than two threads or are secured with a nut (6) Thread-forming machine screws that engage not less than two threads in the enclosure . Okay that says it all i guess. So will a sheet metal screw meet"engage not less than two threads in the enclosure" If not what does? Clear as mud.
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#7969 - 01/15/11 10:12 PM Re: do not ground something using a SHEET METAL screw [Re: Nick Sasso]
Nick Sasso Post-A-Holic Member Registered: 11/08/01 Posts: 1451 Loc: West Palm Beach	Thanks all! I am trying to find something other than "permitted methods" -- I am trying to find the most specific code for NOT allowing a ground bar terminal to be installed to panel frame using sheet metal screws. Any other codes I can use? _________________________
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#7970 - 01/15/11 11:11 PM Re: do not ground something using a SHEET METAL screw [Re: Nick Sasso]
gfretwell Unregistered	I read that to say; You look at the thread pitch of the screw and the thickness of the metal. If the metal is not greater than the thread pitch (allowing the thread to engage on both sides of a groove in the screw) you either need formed threads on a boss getting 2x or a nut on the back. An example is your typical thread forming x-32 screw (pitch .0312") would need to be in metal thicker than 1/32" (20ga steel or thicker).
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#7990 - 01/19/11 11:31 AM Re: do not ground something using a SHEET METAL screw [Re: Nick Sasso]
SOwings CBO, MCP, ER, EN Registered: 01/22/10 Posts: 50 Loc: Nassau County	The key word is "machine screw". A machine screw has fine treads like a 6-32, 8-32, 10-24, 1/4-20 screw. A sheet metal screw is like a wood screw and has a coarse, winding thread. Machine screws have matching nuts to be used with them. I hope this helps...
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