best grounding washers?

[coppercone2]

If you search for grounding washer, you get a whole variety of washers.

There are the star ones (internal external) and then some washers that get weird looking, kind of like nordlock.

What are the best grounding washers?

[Zeyneb]

I'm also interested in this topic. But I think know as little as you do about it. Is there a definition of what a grounding washer actually is? You want to connect a wire with an eye or fork terminal to a body of metal I assume?

[coppercone2]

no just for joining two things electrically. You can have a tabbed grounding washer that you solder or crimp to a wire

[Hawaka]

I think surface preparation is way more important than the washer you gonna use. If both surface are properly cleaned and all coating/paint/oxide removed, then you can use a regular washer.

If not, you probably have to think about how thick is the layer you need to pierce through before making contact. Also if you have a thick layer of paint, the connection might loosen up after some time as the paint get compressed.

[themadhippy]

pity they dont make piranha nuts smaller than 20mm

[coppercone2]

Is the whole thing that the grounding washer is only necessary with paint like proven? I see people leaning in that direction.

Has anyone seen a serrated washer be necessary on a bare metal bond before? Because some people call them paint penetrating washers, but other people call them bonding washers. Official documents seem to say that if you want to use a serrated tooth washer instead of paint stripping, you need to use a miliohm meter to verify it. It does not seem to be the case with stripped metal, which is just trusted. Is the serrated washer just a catch all for improper prep?

[helius]

"Bare metal" generally isn't. All active metals grow an oxide layer that is usually quite insulative (silver is an exception). To break through such surface layers, you need either chemical or mechanical means.

[coppercone2]

yeah I mean if you sand it and grease it, the star washer seems redundant/counter productive, right? Or is that only on steel and you still want it on Al?

[helius]

Just based on observations, I see star washers used almost universally, both on steel, aluminum, and copper PCB mounting holes. Grease on chassis connections isn't that common.
If copper is protected with an inactive metal (nickel, gold) you don't need star washers.

[coppercone2]

https://www.nsrp.org/wp-content/uploads/2015/10/Deliverable-2011-452-Improved_Bonding_Grounding_Final_Report-Ingalls_Shipbuilding.pdf

But these guys seem to say that just bare metal and grease is fine, for ships no less.

That would imply with paint stripped and cleaned steel and brass you are OK without the serrated washers, and they only reccomend them for painted surfaces to save dough (read it carefully, I got lost several times in that snore piece).

They have case #1 for stripped/unpainted/clean metal, and case #2 (serrated washer) for painted metal. There is no mention of using a serrated washer with clean metal, only grease. To me that says that the serrated washer is just adding problems unless there is paint there. I heard this opinion on forums before.

But the thing is, aluminum might be a wild card.

So, if bare aluminum is stripped and greased, does it need a star washer?

[thm_w]

What problems is the serrated washer adding exactly?

If you are just doing this for yourself, then measure the resistance, most likely its fine if the surfaces are un-painted and un-anodized as mentioned.
If this is for a proper job related to earth bonding, with any sort of regulations, then don't screw around and spend the 5c on a washer.

[coppercone2]

But read the document, they build stuff for the navy and they don't seem to recommend using a washer unless there is paint. I don't think this has anything to do with money. What it looks like is that it might be counter productive.

I think the idea is that
1) washer reduces bond area
2) washer allows for ingress of corrosive materials
3) grease is less secure

and they even seem to say that the washer is like a cheap-ass solution compared to stripping the paint and just bolting it.


And that document says that the washers are NOT approved by the ship yard, its a suggestion to use the washers to save man hour cost on paint stripping and masking planning! The entire point seems to be to convince the navy to use the washers to reduce costs.

[thm_w]

Are you building marine equipment where ingress is relevant?
Does bond area matter, given the currents you are dealing with?

[coppercone2]

but my man hours don't count and I paint the metal myself so I would rather put masking tape and sand it then have star washers if its all the same

like why bother having metric and imperial serrated washer kits if their not necessary unless your trying to save dollars on like big stuff, I am not the government.

Masking tape + hole punch set, I already have that. I don't want to put together a unnecessary kit of weird hardware.

[thm_w]

They are necessary for certain applications and industries as we've discussed.

If masking, sanding is what you prefer, then do that.

[coppercone2]

why would you add it unless you had to? What does it bring to the table other then a useless component if its not being used to penetrate paint?

[Stray Electron]

But read the document, they build stuff for the navy and they don't seem to recommend using a washer unless there is paint. I don't think this has anything to do with money. What it looks like is that it might be counter productive.

I think the idea is that
1) washer reduces bond area
2) washer allows for ingress of corrosive materials
3) grease is less secure

and they even seem to say that the washer is like a cheap-ass solution compared to stripping the paint and just bolting it.


And that document says that the washers are NOT approved by the ship yard, its a suggestion to use the washers to save man hour cost on paint stripping and masking planning! The entire point seems to be to convince the navy to use the washers to reduce costs.

   I worked for a company that made MIL equipment for the US Navy, the US Army, the US Army Missile Command, Canadian Forces and US Space Command. Those are just the End Users of programs that I personally worked on, but we also built items for the USMC, USAF and for the British military.  That said, I've never seen any kind of directive to use grounding washers over paint! In electrical devices we always used external tooth star washers on top of a flat washer and on a bare metal surface. Even on circuit boards that were conformal coated an area is left bare for each bolt and washer.  The idea of not using washers in any kind of military system in order to save money is simply ludicrous!  In many applications all nuts, bolts and washers were required to be replaced every time that they were removed. And further, NOTHING is grounded via screws and the like, EVERY electrical circuit has wired connections. Even the shield braid of coaxial cables have special crimped and soldered on connections to small wires and each of those wires is connected back to it's signal source (not a chassis ground!) Even the engine starters and the like in military aircraft and vehicles has WIRED power and power return (aka "ground") connections.  I also personally own two former US military vehicles both built in the 1950s and both of them are also built that way.  One is a x-Korean War USMC Forward Air Controller's jeep and packed full of both ground and aircraft radios so I have a LOT of experience with MIL electrical systems.

  I would REALLY like to see an kind of official directive to use washers as part of any kind of electrical circuit on top of a painted surface.

[coppercone2]

well I will take that over a document that references cost 5000 times

[thm_w]

  I would REALLY like to see an kind of official directive to use washers as part of any kind of electrical circuit on top of a painted surface.

Yes mil-spec is going to be stringent and not allow painted surfaces at all (below).
No directive would explicitly call out a painted surface that I can think of, but they could allow compliance by passing a high current earth test (10A+) within some resistance range.

Also for any sort of low voltage or RF application, where you've proven the device as built passes EMI testing, would be acceptable.

3.2.6 Grounding requirements. A ground stud shall be provided on equipment. The ground stud shall provide the electrical ground connection to the chassis or frame and shall be mechanically secured to insure low resistance joints by soldering to a spot welded terminal lug or to a portion of the chassis or frame that has been formed into a soldering lug, or by use of a terminal by a screw, nut and lock washer. The ground stud shall be of a size to allow electrical connection of size AWG 10 wire. All hardware used for grounding or other
electrical connections shall be made from copper or copper alloys. Terminal luge shall be tin plated or hot tin dipped. Paint, varnish, lacquer, etc., shall be removed from the vicinity of the fastening point to insure metallic contact of the two surfaces. Corrosion protection shall be provided for all ground connections.

https://www.reddit.com/r/ECE/comments/468cx0/comment/d03uxo6/?utm_source=share&utm_medium=web2x&context=3
https://www.electricneutron.com/earthing-system/grounding-requirement-for-installation/
https://www.unit3compliance.co.uk/spring-or-star-washers-for-earthing-stud/

[TimFox]

For assembling anodized aluminum T-slotted frameworks, there is special anodizing-breaking hardware to cut through the thick oxide surface to ensure electrical connection.
https://www.mcmaster.com/6812N216/

[coppercone2]

But read the document, they build stuff for the navy and they don't seem to recommend using a washer unless there is paint. I don't think this has anything to do with money. What it looks like is that it might be counter productive.

I think the idea is that
1) washer reduces bond area
2) washer allows for ingress of corrosive materials
3) grease is less secure

and they even seem to say that the washer is like a cheap-ass solution compared to stripping the paint and just bolting it.


And that document says that the washers are NOT approved by the ship yard, its a suggestion to use the washers to save man hour cost on paint stripping and masking planning! The entire point seems to be to convince the navy to use the washers to reduce costs.

   I worked for a company that made MIL equipment for the US Navy, the US Army, the US Army Missile Command, Canadian Forces and US Space Command. Those are just the End Users of programs that I personally worked on, but we also built items for the USMC, USAF and for the British military.  That said, I've never seen any kind of directive to use grounding washers over paint! In electrical devices we always used external tooth star washers on top of a flat washer and on a bare metal surface. Even on circuit boards that were conformal coated an area is left bare for each bolt and washer.  The idea of not using washers in any kind of military system in order to save money is simply ludicrous!  In many applications all nuts, bolts and washers were required to be replaced every time that they were removed. And further, NOTHING is grounded via screws and the like, EVERY electrical circuit has wired connections. Even the shield braid of coaxial cables have special crimped and soldered on connections to small wires and each of those wires is connected back to it's signal source (not a chassis ground!) Even the engine starters and the like in military aircraft and vehicles has WIRED power and power return (aka "ground") connections.  I also personally own two former US military vehicles both built in the 1950s and both of them are also built that way.  One is a x-Korean War USMC Forward Air Controller's jeep and packed full of both ground and aircraft radios so I have a LOT of experience with MIL electrical systems.

  I would REALLY like to see an kind of official directive to use washers as part of any kind of electrical circuit on top of a painted surface.

Ok to revisit this, based on what you said, the junction is washer starwasher bolt head. This means that the metal surface is being contacted by the regular washer.

I am thinking that if these were lockwire bolts, then you would not need the serrated washer (just mechanical). You don't think it has anything to do with the bottom of the screw electrically do you?

Why do you have the serrated washer between the bolt head and the regular washer? Is that just anti rotation ?

And from a non safety perspective, it still seems that there is a better EMI path through a bolt sitting on a washer rather then a bolt on a star washer on a washer. Less impedance.

So it sounds like you are saying that you only ever seen the star washer used for mechanical reasons in mil spec equipment.

If you got a bolt with a wider head, would you still desire the regular washer underneath?

I am also curious about penetrating thread locker (wicking) vs star washers for anti rotation. It seems that if its tightened already and it just wicks past the interfaces, then its a sealed thread, and the nut is better secured (electrically anti corrosion) to the nut.

But if course if you use a star washer, you can have grease on the thread. The bolt needs to be clean to mate with the nut for threadlocker. Then its a question of it is better to have a greasy thread interface and star washer for anti rotation or a clean thread interface with loc-tite with no star washer.

I wonder how to setup a experiment. Maybe a welded box with a antenna inside, secured in different ways, with a reciever outside. I bet its hard to measure though.

For instance this web page circles out the round washer for a lug.
https://www.unit3compliance.co.uk/spring-or-star-washers-for-earthing-stud/

But I bought some very reputable high current hardware from a professional manufacturer (german). They have a star washers, instead of the split ring, but do include a washer to protect the copper lug from the serrated washer. These guys seem to want a spring washer to cut into the lug.  NASA also does not like the split ring washer. It seems that there is a school of thought that says you don't want any penetration of lug connectors.