# Screws for a ground bar



## wildleg (Apr 12, 2009)

ElectricalArtist said:


> I can't remember what code it is, but today I used a number 10 hex head screw to mount a ground bar. It was one of those self Tapper screws but it doesn't have threads that you can put a bolt on I guess it's more of a sheet metal Screw. Is that allowed


no .


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## Service Call (Jul 9, 2011)

No it’s not. I seem to remember at one time it was required to be a 32 thread then I heard it is supposed to have 2 threads in contact with the metal. 

I’ve been wanting to research this and clarify it. I have no problem with either one but a sheet metal type thread really doesn’t have the contact ability, IMO. 


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## Bird dog (Oct 27, 2015)

Not quite. It's usually a 10-32 that is provided with a listed ground bar. IIRC code requires at least three threads to be engaged. A sheet metal screw is not allowed by code.


Two threads or a nut...250.8A5&6


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## Lone Crapshooter (Nov 8, 2008)

I have been told by someone who claims to be a expert on grounding that it is OK to use a selfdrilling screw provided that it has fine threads . 
10/32 is the proper size if you are going to drill and tap

LC


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## MechanicalDVR (Dec 29, 2007)

It has to be a fine thread.


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## Mouser (May 4, 2011)

Code reference.

*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 or more of the following means:

(1) 
(2) 
(3) 
(4) 
(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) 
(8)


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## matt1124 (Aug 23, 2011)

Don’t forget your grounding sharpie!


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## 99cents (Aug 20, 2012)

When you do a panel swap, rob the parts off the old one. And make sure you have a tri-tap in your bag.


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## JoeSparky (Mar 25, 2010)

You have all the parts you need in your truck to do this and comply with code.

1. Attach ground bar with #10 tek screws
2. Back them out and take the ground bar back out
3. Drive thread cutting ground screws in the holes you just made
4. Back the ground screws out
5. Reinstall ground bar using 10/32 x 1" screws. If you don't carry those in the truck, steal them from the clamps of metal old work boxes
6. ?????
7. Profit


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## trentonmakes (Mar 21, 2017)

Do thwy actually look at that???

Ive used self tapers many times

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## trentonmakes (Mar 21, 2017)

Tapers....tappers...
Leave me alone you spelling nazis

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## matt1124 (Aug 23, 2011)

trentonmakes said:


> Do thwy actually look at that???
> 
> Ive used self tapers many times
> 
> Sent from my LG-K550 using Tapatalk


They’re too busy making sure the bonding jumper from the furthest ground rod is the same continuous wire from the first ground rod to the meter box to worry about the part of the grounding system that matters.


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## active1 (Dec 29, 2009)

Just drilling a 10-32 in metal can be questionable if the box / can / etc is a thinner gauge. Never seen it called. But I have stripped or found stripped 10-32 tapped this way.

Do the math. 32 threads per inch. That means 2 threads per 1/16 metal.
Convert to decimal 1/16 = 0.0625" which is about 15 gauge (0.673)
314.40 requires metal boxes at least 0.053" which is 17 gauge 0.0538"

But how does the factory get it approved?
Look closely at many factory 10-32 holes.
They were made in a way that stretched the metal thicker around the 10-32 hole.
Especially with panels. 4x4 boxes that have the recessed ground screw spot.

They make self-taping screws that do this.
Used on car sheet metal for decades.
The screw tip is a threaded cone shape.
Drilled in a smaller than standard hole for that tap size.
It stretches the metal on the backside providing more area for threads.
The pic below is not a 10-32 but it's the same idea.
There is no 10-32 rule, only needs to be a machine screw.
Sometimes it's easier to just drill a hole put a nut on the back.


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## Bird dog (Oct 27, 2015)

In a parts tray/box, also keep extra grounding/bonding hardware. Also called a save my rearend box.


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## oliquir (Jan 13, 2011)

csa inspectors guys ask me to remove paint under the grounding bar when i make control panels, but they don't care about the screw at all.


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## MechanicalDVR (Dec 29, 2007)

trentonmakes said:


> Tapers....tappers...
> Leave me alone you spelling nazis


You know the first one follows a sheetrocker?


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## MechanicalDVR (Dec 29, 2007)

active1 said:


> Just drilling a 10-32 in metal can be questionable if the box / can / etc is a thinner gauge. Never seen it called. But I have stripped or found stripped 10-32 tapped this way.
> 
> Do the math. 32 threads per inch. That means 2 threads per 1/16 metal.
> Convert to decimal 1/16 = 0.0625" which is about 15 gauge (0.673)
> ...


I think most metal boxes are 14ga, then some sub panels are much lighter.


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## active1 (Dec 29, 2009)

"I think most metal boxes are 14ga"

Wireways and cans are available in multiple gauges including 16 gauge
.


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## Gnome (Dec 25, 2013)

99cents said:


> When you do a panel swap, rob the parts off the old one. And make sure you have a tri-tap in your bag.


Also the drill taps that Greenlee and others make. They are wizard when you have to thread a hole in a box mounted on wood/drywall. 

Switched a whole house over to decora devices once where the wall surface was solid wood and the guy who did it got the paneling tight to the box. Hence no space for the decora wallplate screw. Zip-zip with the drill tap and good to go.


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## MDShunk (Jan 7, 2007)

The punched holes in a panel for the ground bar spot are swaged to put more sheet metal in contact with the screw. 

The screws that come with ground bars are normally tri-lobal to form threads. (spin it between your fingers and you'll feel it's triangular). Required to be tri-lobal? Not that I can tell. 

Can/should you tap a hole for a regular 10-32, and can you get three threads in contact with the sheet metal? Mathematically, no. I do it with certain regularity, however. There's two or three screws in contact on a typical ground bar, so I don't sweat it for a second.


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## MechanicalDVR (Dec 29, 2007)

Gnome said:


> Also the drill taps that Greenlee and others make. They are wizard when you have to thread a hole in a box mounted on wood/drywall.
> 
> Switched a whole house over to decora devices once where the wall surface was solid wood and the guy who did it got the paneling tight to the box. *Hence no space for the decora wallplate screw. Zip-zip with the drill tap and good to go*.


Done that many times.


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## MDShunk (Jan 7, 2007)

MechanicalDVR said:


> Done that many times.


It sucks when it's ceramic/porcelain tile or a granite splash. I have managed to use my T strippers to leave about 2 threads on a decora plate screw and get a reasonable plate fit. Ug.


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## matt1124 (Aug 23, 2011)

MDShunk said:


> It sucks when it's ceramic/porcelain tile or a granite splash. I have managed to use my T strippers to leave about 2 threads on a decora plate screw and get a reasonable plate fit. Ug.


They have these at Home Depot. They are great for removing bits of ceramic material. Start at an angle to keep it from walking, then straighten out and you’ve got yourself a hole. 

I use them to hang vent hoods. We put plywood up, tile guy goes over it, then use this bit to gently make the bolt holes without damage.


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## Bird dog (Oct 27, 2015)

matt1124 said:


> They have these at Home Depot. They are great for removing bits of ceramic material. Start at an angle to keep it from walking, then straighten out and you’ve got yourself a hole.
> 
> I use them to hang vent hoods. We put plywood up, tile guy goes over it, then use this bit to gently make the bolt holes without damage.


https://www.homedepot.com/p/Milwaukee-1-4-in-Diamond-Plus-Mini-Hole-Saw-49-56-0505/204994400


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## splatz (May 23, 2015)

matt1124 said:


> They have these at Home Depot. They are great for removing bits of ceramic material. Start at an angle to keep it from walking, then straighten out and you’ve got yourself a hole.
> 
> I use them to hang vent hoods. We put plywood up, tile guy goes over it, then use this bit to gently make the bolt holes without damage.





Bird dog said:


> https://www.homedepot.com/p/Milwaukee-1-4-in-Diamond-Plus-Mini-Hole-Saw-49-56-0505/204994400


These are not as good for tile as that bit, but easier to start and good for concrete other materials as well.


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## MechanicalDVR (Dec 29, 2007)

MDShunk said:


> It sucks when it's ceramic/porcelain tile or a granite splash. I have managed to use my T strippers to leave about 2 threads on a decora plate screw and get a reasonable plate fit. Ug.


That's when I pull out the dremel and cut a small piece out.


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## active1 (Dec 29, 2009)

MDShunk said:


> It sucks when it's ceramic/porcelain tile or a granite splash. I have managed to use my T strippers to leave about 2 threads on a decora plate screw and get a reasonable plate fit. Ug.


I'll cut the trim screws also.
If I mess up a trim screw, grab another & try again.
Mess up a tile, not a good day.


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## lighterup (Jun 14, 2013)

trentonmakes said:


> Do thwy actually look at that???
> 
> Ive used self tapers many times
> 
> Sent from my LG-K550 using Tapatalk


they do here:vs_mad:


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## B-Nabs (Jun 4, 2014)

Hey Canadians, do we have a rule like this one? If so, I can't find it. 

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## active1 (Dec 29, 2009)

Here is an non compliant self drilling, sold as ground screw.
But it's green, which so many think is a requirement on every EG screw.

https://www.amazon.com/Skywalker-Signature-Self-tapping-Ground-Qty100/dp/B009ONED0C


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## MDShunk (Jan 7, 2007)

active1 said:


> Here is an non compliant self drilling, sold as ground screw.
> But it's green, which so many think is a requirement on every EG screw.
> 
> https://www.amazon.com/Skywalker-Signature-Self-tapping-Ground-Qty100/dp/B009ONED0C


That can be a compliant ground screw if it was used, for instance, on equipotential bonding of thicker metal materials. It's would probably also work compliantly to replace a missing ground screw in an FS body where the cast boss for the ground screw is quite thick and deep. Day-to-day in a stamped steel box? Unlikely to be compliant.


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