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#105900 - 09/17/05 09:41 AM Sheet Metal Screws Not Allowed  
Joe Tedesco  Offline
Member
Joined: Oct 2000
Posts: 2,749
Boston, Massachusetts USA
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Joe Tedesco, NEC Consultant

2017 / 2014 NEC & Related Books and Study Guides

#105901 - 09/17/05 10:25 AM Re: Sheet Metal Screws Not Allowed  
Dave T  Offline
Member
Joined: Jan 2005
Posts: 155
Waukesha, WI, USA
That's precious.
I can't make it out but is ths an SE or sub panel? For some reason the installer chose to avoid using a possibly grounded neutral bar or it was isolated because it was a subpanel so he couldn't use it and didn't have a ground bar or lug to terminate to.
But is that a neutral bar bonding screw just to the right of the lug where the reidentified neutral is terminated, between that grayish wire on the far right and the white wire just to its left? If wo why would one terminal that bar copper ground wire where it is?
This looks as if this is a replacement panel from the wire splices on the left.


#105902 - 09/17/05 12:52 PM Re: Sheet Metal Screws Not Allowed  
ShockMe77  Offline
Member
Joined: Jun 2005
Posts: 821
Rahway, New Jersey
My guess would be that its a main panel with all AC cables and the installer just "forgot" to put in a ground bar and bonding screw.

As far as the sheet metal screw being used for that bonding ground wire lug, I use my "threader" tool and drive in an 8/32 bolt to attach a ground bar. What are some other methods that can be used?


#105903 - 09/17/05 12:53 PM Re: Sheet Metal Screws Not Allowed  
iwire  Offline
Moderator
Joined: Jan 2003
Posts: 4,391
North Attleboro, MA USA
A nut and bolt can be used.


Bob Badger
Construction & Maintenance Electrician
Massachusetts

#105904 - 09/18/05 06:31 PM Re: Sheet Metal Screws Not Allowed  
macmikeman  Offline
Member
Joined: Jul 2002
Posts: 717
Honolulu, Hawaii
Good call Bob. So can a machined hole with a 10-32 screw. I do not think the code book prohibits using a washer with a machine screw, or a nut and bolt. Bet you though from looking at this mess that Joe is right on the money with this picture and it is a sheet metal screw.


#105905 - 09/18/05 08:38 PM Re: Sheet Metal Screws Not Allowed  
renosteinke  Offline
Cat Servant
Member
Joined: Jan 2005
Posts: 5,316
Blue Collar Country
May I draw everyone's attention to 110.14 (A)?

As I read this, machine screws, even with a washer, would not be equivalent to the permitted "wire binding" head. Oddly enough, a "washer head," such as found on many teks screws, would.


110.14 already requires a "thoroughly good connection." I suggest the more specific ban on "sheet metal screws" serves only to muddy the issue, and should be dropped.


#105906 - 09/19/05 12:19 AM Re: Sheet Metal Screws Not Allowed  
yaktx  Offline
Member
Joined: Feb 2003
Posts: 288
Austin, Texas, USA
Ya'know, ever since Greenlee came out with those 3-in-1 tap tools, it's easier than ever to put a machine screw into an existing cabinet. That's what I always do. I bought a wire brush drill attachment, because there is one inspector here who insists on removing paint. That's about it. I try to carry a ground bar or two on my truck. If I wreck out a panel, I save the ground and neutral bars-- no shame in reusing them for equipment ground. If you have the right size tap, and you can use it with a 3" extension and battery drill, there is no situation where you cannot use a machine screw, except possibly with masonry behind, and even then, 3-in-1 taps are cheap (go ahead and ruin one).


#105907 - 09/19/05 12:22 AM Re: Sheet Metal Screws Not Allowed  
yaktx  Offline
Member
Joined: Feb 2003
Posts: 288
Austin, Texas, USA
I suspect the ban on sheet metal screws has less to do with any suspicion of an inherently bad connection than with the suspicion that some installers do not take full advantage of the torque clutch feature. That can be a problem with machine screws, too.


#105908 - 09/19/05 08:51 AM Re: Sheet Metal Screws Not Allowed  
Larry Fine  Offline
Member
Joined: Feb 2005
Posts: 693
Richmond, VA
Those "3-in-1 taps" are thread chasers, not taps, andthey're not designed for fresh-threading holes, so don't be suprised if you snap one.

The best way to use one as a tap is to back it off several times per rotation. I'm a pro, and I know how do do something wrong the right way.


Larry Fine
Fine Electric Co.
fineelectricco.com

#105909 - 09/19/05 08:55 PM Re: Sheet Metal Screws Not Allowed  
renosteinke  Offline
Cat Servant
Member
Joined: Jan 2005
Posts: 5,316
Blue Collar Country
One reason I am a little strident over the "ban" is that I feel a little bait & switch occurred here.

Prior to the ban, everywhere you looked there were pics of ordinary sheet metal screws- the ones with points, not drill tips- dangling from oversized holes. The sort of application where NO fastener would ever work.

Once the ban was printed, all the seminar wonks went on a crusade against the "teks" screw- or even ANY screw that was not green, with a hex head.

I don't believe the ban would have passed had there been an open discussion of the "teks" screws.

As it stands, the ban only gets us sidetracked into side issues, and possible conflicts with 110.14. We already have torque specs in the code- that ought to ensure good enough holding power.
Moreover, many panels have their covers secured with screws that grab little stamped pieces of sheet metal- wit a thickness far less than a single thread. These variations on the "speed nut" seem to hold quite well- another set-back for the machine screw crowd.



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