Re: [PSES] External toothed star washer used in earth connection

[Doug Powell]

  As I see it, the star between the lug and the sheet metal is for for conductivity.  The star above the lug is for mechanical securement.  It is therefore possible to use additional techniques for mechanically securing the fastener; SEM screws, KEP nuts, jam nuts, etc. If you think about the path current takes you realize the metal parts located above do not actually contribute to conductivity.  A German safety engineer I know from LGA Nuremberg used to press his thumb sideways against the lug and try to loosen the connection. A proper hardware stack up would always prevent this. Have a great weekend, Doug Sent from my Android on the Verizon 4G LTE Network   From: scott...@gmail.comSent: August 11, 2018 3:13 AMTo: EMC-PSTC@LISTSERV.IEEE.ORGReply-to: scott...@gmail.comSubject: Re: [PSES] External toothed star washer used in earth connection  Scott,Thanks for your sharing experience on this matter!  What is the purpose for the second star washer?  Double protection on top of the first one.  The star washer is a very essential part for the success of good earth the metal enclosure.Regards,ScottOn Sat, 11 Aug 2018 at 02:11, Scott Douglas <sdouglas...@gmail.com> wrote:Many years ago a TUV Engineer drummed into my head "the only acceptable way" to make protective earth bonds was chassis > star > ring lug > star > nut for ground studs pressed into the chassis.On Fri, Aug 10, 2018, 9:54 AM Scott Xe <scott...@gmail.com> wrote:Hi Rich, Thanks for your advice! 😊  Regarding the flat washer, can it be the flat ring lug of the connecting wire instead? Between the screw head and the metal enclosure, do we need a flat washer?  That is to say: screw head -> flat washer -> metal enclosure -> on other side of metal enclosure with paint removed in the contact area with the flat ring lug -> flat ring lug of the earthing wire -> split ring lock washer -> plain nut to establish a good electrical earth connection. Thanks and regards, Scott Sent from Mail for Windows 10 From: Richard NuteSent: Friday, 10 August 2018 03:11 AMTo: EMC-PSTC@LISTSERV.IEEE.ORGSubject: Re: [PSES] External toothed star washer used in earth connection  "The lock washer should not interface between the bolt head and the metal, the lock washer should be between the head and a flat washer." That locks the bolt to the flat washer so they turn together.  😊 Establishes a good electrical connection between the bolt and the flat washer!  😊 Rich  -This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to <emc-p...@ieee.org>All emc-pstc postings are archived and searchable on the web at: http://www.ieee-pses.org/emc-pstc.htmlAttachments are not permitted but the IEEE PSES Online Communities site at http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used formats), large files, etc.Website: http://www.ieee-pses.org/Instructions: http://www.ieee-pses.org/list.html (including how to unsubscribe)List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators:Scott Douglas <sdoug...@ieee.org>Mike Cantwell <mcantw...@ieee.org> For policy questions, send mail to:Jim Bacher <j.bac...@ieee.org>David Heald <dhe...@gmail.com>  -

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Re: [PSES] External toothed star washer used in earth connection

[Scott Xe]

Scott,

Thanks for your sharing experience on this matter!  What is the purpose for
the second star washer?  Double protection on top of the first one.  The
star washer is a very essential part for the success of good earth the
metal enclosure.

Regards,

Scott


On Sat, 11 Aug 2018 at 02:11, Scott Douglas  wrote:

> Many years ago a TUV Engineer drummed into my head "the only acceptable
> way" to make protective earth bonds was chassis > star > ring lug > star >
> nut for ground studs pressed into the chassis.
>
>
> On Fri, Aug 10, 2018, 9:54 AM Scott Xe  wrote:
>
>> Hi Rich,
>>
>>
>>
>> Thanks for your advice! 😊  Regarding the flat washer, can it be the
>> flat ring lug of the connecting wire instead?
>>
>>
>>
>> Between the screw head and the metal enclosure, do we need a flat
>> washer?  That is to say: screw head -> flat washer -> metal enclosure -> on
>> other side of metal enclosure with paint removed in the contact area with
>> the flat ring lug -> flat ring lug of the earthing wire -> split ring lock
>> washer -> plain nut to establish a good electrical earth connection.
>>
>>
>>
>> Thanks and regards,
>>
>>
>>
>> Scott
>>
>>
>>
>> Sent from Mail <https://go.microsoft.com/fwlink/?LinkId=550986> for
>> Windows 10
>>
>>
>>
>> *From: *Richard Nute 
>> *Sent: *Friday, 10 August 2018 03:11 AM
>> *To: *EMC-PSTC@LISTSERV.IEEE.ORG
>> *Subject: *Re: [PSES] External toothed star washer used in earth
>> connection
>>
>>
>>
>>
>>
>> "The lock washer should not interface between the bolt head and the
>> metal, the lock washer should be between the head and a flat washer."
>>
>>
>>
>> That locks the bolt to the flat washer so they turn together.  😊
>>
>>
>>
>> Establishes a good electrical connection between the bolt and the flat
>> washer!  😊
>>
>>
>>
>> Rich
>>
>>
>>
>>
>>
>> -
>> 
>>
>> This message is from the IEEE Product Safety Engineering Society emc-pstc
>> discussion list. To post a message to the list, send your e-mail to <
>> emc-p...@ieee.org>
>>
>> All emc-pstc postings are archived and searchable on the web at:
>> http://www.ieee-pses.org/emc-pstc.html
>>
>> Attachments are not permitted but the IEEE PSES Online Communities site
>> at http://product-compliance.oc.ieee.org/ can be used for graphics (in
>> well-used formats), large files, etc.
>>
>> Website: http://www.ieee-pses.org/
>> Instructions: http://www.ieee-pses.org/list.html (including how to
>> unsubscribe) <http://www.ieee-pses.org/list.html>
>> List rules: http://www.ieee-pses.org/listrules.html
>>
>> For help, send mail to the list administrators:
>> Scott Douglas 
>> Mike Cantwell 
>>
>> For policy questions, send mail to:
>> Jim Bacher 
>> David Heald 
>>
>>
>> -
>> 
>>
>> This message is from the IEEE Product Safety Engineering Society emc-pstc
>> discussion list. To post a message to the list, send your e-mail to <
>> emc-p...@ieee.org>
>>
>> All emc-pstc postings are archived and searchable on the web at:
>> http://www.ieee-pses.org/emc-pstc.html
>>
>> Attachments are not permitted but the IEEE PSES Online Communities site
>> at http://product-compliance.oc.ieee.org/ can be used for graphics (in
>> well-used formats), large files, etc.
>>
>> Website: http://www.ieee-pses.org/
>> Instructions: http://www.ieee-pses.org/list.html (including how to
>> unsubscribe) <http://www.ieee-pses.org/list.html>
>> List rules: http://www.ieee-pses.org/listrules.html
>>
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>> Mike Cantwell <mcantw...@ieee.org>
>>
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>> Jim Bacher <j.bac...@ieee.org>
>> David Heald <dhe...@gmail.com>
>>
>

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Re: [PSES] External toothed star washer used in earth connection

[Scott Xe]

Dear Rich,

Deeply appreciate your detailed explanation!

Regarding gas-tight connection, it seems to have some conflicts or my
mis-interpretation.  I take an example below:-

*Using split ring lock washer to establish gas-tight connection*

Screw head -> one side of metal enclosure (it has paint on both sides) ->
on the other side of metal enclosure with paint removed in the area of the
lug -> lug ring of earth connection -> split ring lock washer -> plain nut

The metal enclosure has established a gas-tight  reliable connection with
earth connection.

*Using toothed star lock washer but fail to establish gas-tight connection*

Screw head -> one side of metal enclosure (it has paint on both sides) ->
on the other side of metal enclosure without paint removed in the area of
the washer -> toothed star lock washer (sharp edge towards the metal
enclosure) -> lug ring of earth terminal -> plain nut

The metal enclosure has established pointed contact connection with earth
connection.

Thanks and regards,

Scott



On Sat, 11 Aug 2018 at 05:45, Richard Nute  wrote:

>
>
> Hi Scott:
>
>
>
> For the sake of this discussion, a toothed star lock washer has two
> functions: (1) keep the bolt from loosening, and (2) establishing a “good”
> electrical connection.  (One characteristic of a good and reliable
> electrical connection is that the contact between the two conductors is
> gas-tight.)
>
>
>
> A flat ring lug performs two functions, (1) flat washer and (2) means for
> electrical connection to the washer via a lug. The washer cannot -- by
> itself -- form a gas-tight connection to any other conductor.
>
>
>
> If the bolt is to be a current-carrying conductor, then a star washer must
> be placed between the ring lug and the bolt head to establish a gas-tight
> connection between the two (assuming the star has points on both sides of
> the washer).
>
>
>
> If the bolt goes through a metal panel and is intended to enable an
> electrical connection to the panel (on the other side), then another star
> washer must be used (on the bolt) between the nut and the metal panel.
> This makes a gas-tight connection to the nut and another gas-tight
> connection to the panel (and locks the nut).  (The tightened nut makes a
> gas-tight connection to the bolt.)
>
>
>
> There are lots of other configurations.  The principle is to establish the
> current path, and then use star lock washers to establish gas-tight
> connections.
>
>
>
> According to the research paper in Ted Eckert’s message, the star washer
> will cut through the paint and establish a gas-tight connection.  There is
> no need to remove paint.
>
>
>
> Best regards,
>
> Rich
>
>
>
>
>
>
>
>
>
>
>
> *From:* Scott Xe 
> *Sent:* Friday, August 10, 2018 9:54 AM
> *To:* ri...@ieee.org; EMC-PSTC@LISTSERV.IEEE.ORG
> *Subject:* RE: [PSES] External toothed star washer used in earth
> connection
>
>
>
> Hi Rich,
>
>
>
> Thanks for your advice! 😊  Regarding the flat washer, can it be the flat
> ring lug of the connecting wire instead?
>
>
>
> Between the screw head and the metal enclosure, do we need a flat washer?
> That is to say: screw head -> flat washer -> metal enclosure -> on other
> side of metal enclosure with paint removed in the contact area with the
> flat ring lug -> flat ring lug of the earthing wire -> split ring lock
> washer -> plain nut to establish a good electrical earth connection.
>
>
>
> Thanks and regards,
>
>
>
> Scott
>
>
>
> Sent from Mail <https://go.microsoft.com/fwlink/?LinkId=550986> for
> Windows 10
>
>
>
> *From: *Richard Nute 
> *Sent: *Friday, 10 August 2018 03:11 AM
> *To: *EMC-PSTC@LISTSERV.IEEE.ORG
> *Subject: *Re: [PSES] External toothed star washer used in earth
> connection
>
>
>
>
>
> "The lock washer should not interface between the bolt head and the metal,
> the lock washer should be between the head and a flat washer."
>
>
>
> That locks the bolt to the flat washer so they turn together.  😊
>
>
>
> Establishes a good electrical connection between the bolt and the flat
> washer!  😊
>
>
>
> Rich
>
>
>

-

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Re: [PSES] External toothed star washer used in earth connection

[Richard Nute]

 

… a star washer was not acceptable for military grounding. The rationale was 
that the points of the star washer created the conductive grounding path. Since 
the points were fairly small, and the ground fault current was high, a fault 
current would be forced to flow across those tiny point-contacts.

 

According to the Ingalls study (referenced by Ted Eckert):

 

“After the end of testing, some team members voiced a concern about the smaller 
contact surface when grounding washers are substituted for a Class B bond. A 
current test was devised and is detailed in Attachment 12. It was demonstrated 
that the grounding washers have more than adequate current carrying capacity. 
The grounding washer contact points are able to carry more than enough current 
to trip a breaker or allow a ground to be detected.”

 

Best regards,

Rich

 

 

 

 


-

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Re: [PSES] External toothed star washer used in earth connection

[Richard Nute]

Ted's reference to the Ingalls study includes proposed changes to MIL-STD-1310. 
 
  
Furthermore: "It is recommended that the use of grounding washers in place of 
cleaning to “Bright Metal”..."

Best regards,
Rich


-Original Message-
From: Brian O'Connell  
Sent: Friday, August 10, 2018 4:09 PM
To: EMC-PSTC@LISTSERV.IEEE.ORG
Subject: Re: [PSES] External toothed star washer used in earth connection

MIL-B-5087 is superseded by MIL-STD-464, which says "Overpainting of structure 
for corrosion control prior to ensuring an electrical bond has been documented 
as the leading cause of poor or ineffective bonds." 

MIL-STD-464 points to
  MIL-STD-1541 - for space systems
  ARP187 - electrical bonding for aviation
  MIL-HDBK-419  grounding, bonding, and shielding for land systems
  MIL-STD-1310 bonding for ship systems

Brian


From: Edward Price [mailto:e...@jwjelp.com]
Sent: Friday, August 10, 2018 3:02 PM
To: EMC-PSTC@LISTSERV.IEEE.ORG
Subject: Re: [PSES] External toothed star washer used in earth connection

I seem to recall seeing an explanation in MIL-B-5087 (likely now superseded) 
that a star washer was not acceptable for military grounding. The rationale was 
that the points of the star washer created the conductive grounding path. Since 
the points were fairly small, and the ground fault current was high, a fault 
current would be forced to flow across those tiny point-contacts. This had the 
danger of causing the points to melt or arc.

The military preference was strongly in favor of removing the paint below a 
ground-point’s footprint and then using a flat washer below and above the 
ground lug, with a split-ring lockwasher followed by a nut. I have read recent 
criticism of split-ring lockwashers, with machinery people now seeming to favor 
something like the Nord-lock locking system.

Ed Price
WB6WSN
Chula Vista, CA USA

-

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Re: [PSES] External toothed star washer used in earth connection

[Richard Nute]

 

 

The rationale was that the points of the star washer created the conductive 
grounding path. Since the points were fairly small, and the ground fault 
current was high, a fault current would be forced to flow across those tiny 
point-contacts. This had the danger of causing the points to melt or arc.

 

The heat-sinking of the rest of the assembly will prevent overheating.  

 

Many years ago, I tested a #18 power cord wire, cutting each strand one at a 
time and then testing the impedance at 25 amps.  At 3 strands, the wire failed.

 

The heat-sinking provided by the cut strands kept the remaining strands from 
overheating.  

 

Conventional wisdom not backed up by testing.  

 

Best regards,

Rich

 

 

 


-

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Re: [PSES] External toothed star washer used in earth connection

[Brian O'Connell]

MIL-B-5087 is superseded by MIL-STD-464, which says 
"Overpainting of structure for corrosion control prior to ensuring an 
electrical bond has been 
documented as the leading cause of poor or ineffective bonds." 

MIL-STD-464 points to
  MIL-STD-1541 - for space systems
  ARP187 - electrical bonding for aviation
  MIL-HDBK-419  grounding, bonding, and shielding for land systems
  MIL-STD-1310 bonding for ship systems

Brian


From: Edward Price [mailto:e...@jwjelp.com] 
Sent: Friday, August 10, 2018 3:02 PM
To: EMC-PSTC@LISTSERV.IEEE.ORG
Subject: Re: [PSES] External toothed star washer used in earth connection

I seem to recall seeing an explanation in MIL-B-5087 (likely now superseded) 
that a star washer was not acceptable for military grounding. The rationale was 
that the points of the star washer created the conductive grounding path. Since 
the points were fairly small, and the ground fault current was high, a fault 
current would be forced to flow across those tiny point-contacts. This had the 
danger of causing the points to melt or arc.

The military preference was strongly in favor of removing the paint below a 
ground-point’s footprint and then using a flat washer below and above the 
ground lug, with a split-ring lockwasher followed by a nut. I have read recent 
criticism of split-ring lockwashers, with machinery people now seeming to favor 
something like the Nord-lock locking system.

Ed Price
WB6WSN
Chula Vista, CA USA

From: Richard Nute [mailto:ri...@ieee.org] 
Sent: Friday, August 10, 2018 2:46 PM
To: EMC-PSTC@LISTSERV.IEEE.ORG
Subject: Re: [PSES] External toothed star washer used in earth connection


Hi Scott:

For the sake of this discussion, a toothed star lock washer has two functions: 
(1) keep the bolt from loosening, and (2) establishing a “good” electrical 
connection.  (One characteristic of a good and reliable electrical connection 
is that the contact between the two conductors is gas-tight.)

A flat ring lug performs two functions, (1) flat washer and (2) means for 
electrical connection to the washer via a lug. The washer cannot -- by itself 
-- form a gas-tight connection to any other conductor.  

If the bolt is to be a current-carrying conductor, then a star washer must be 
placed between the ring lug and the bolt head to establish a gas-tight 
connection between the two (assuming the star has points on both sides of the 
washer).

If the bolt goes through a metal panel and is intended to enable an electrical 
connection to the panel (on the other side), then another star washer must be 
used (on the bolt) between the nut and the metal panel.  This makes a gas-tight 
connection to the nut and another gas-tight connection to the panel (and locks 
the nut).  (The tightened nut makes a gas-tight connection to the bolt.)  

There are lots of other configurations.  The principle is to establish the 
current path, and then use star lock washers to establish gas-tight connections.

According to the research paper in Ted Eckert’s message, the star washer will 
cut through the paint and establish a gas-tight connection.  There is no need 
to remove paint.  

Best regards,
Rich





From: Scott Xe  
Sent: Friday, August 10, 2018 9:54 AM
To: ri...@ieee.org; EMC-PSTC@LISTSERV.IEEE.ORG
Subject: RE: [PSES] External toothed star washer used in earth connection

Hi Rich,

Thanks for your advice! 😊  Regarding the flat washer, can it be the flat ring 
lug of the connecting wire instead?

Between the screw head and the metal enclosure, do we need a flat washer?  That 
is to say: screw head -> flat washer -> metal enclosure -> on other side of 
metal enclosure with paint removed in the contact area with the flat ring lug 
-> flat ring lug of the earthing wire -> split ring lock washer -> plain nut to 
establish a good electrical earth connection.

Thanks and regards,

Scott

Sent from Mail for Windows 10

From: Richard Nute
Sent: Friday, 10 August 2018 03:11 AM
To: EMC-PSTC@LISTSERV.IEEE.ORG
Subject: Re: [PSES] External toothed star washer used in earth connection


"The lock washer should not interface between the bolt head and the metal, the 
lock washer should be between the head and a flat washer."

That locks the bolt to the flat washer so they turn together.  😊

Establishes a good electrical connection between the bolt and the flat washer!  
😊

Rich

-

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discussion list. To post a message to the list, send your e-mail to 

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Attachments are not permitted but the IEEE PSES Online Communities site at 
http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used 
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Website: http://www.ieee-pses.org/
Instructions: http://www.ieee-pses.org/list.html (including how to un

Re: [PSES] External toothed star washer used in earth connection

[Edward Price]

I seem to recall seeing an explanation in MIL-B-5087 (likely now superseded) 
that a star washer was not acceptable for military grounding. The rationale was 
that the points of the star washer created the conductive grounding path. Since 
the points were fairly small, and the ground fault current was high, a fault 
current would be forced to flow across those tiny point-contacts. This had the 
danger of causing the points to melt or arc.

The military preference was strongly in favor of removing the paint below a 
ground-point’s footprint and then using a flat washer below and above the 
ground lug, with a split-ring lockwasher followed by a nut. I have read recent 
criticism of split-ring lockwashers, with machinery people now seeming to favor 
something like the Nord-lock locking system.

Ed Price
WB6WSN
Chula Vista, CA USA

From: Richard Nute [mailto:ri...@ieee.org]
Sent: Friday, August 10, 2018 2:46 PM
To: EMC-PSTC@LISTSERV.IEEE.ORG
Subject: Re: [PSES] External toothed star washer used in earth connection


Hi Scott:

For the sake of this discussion, a toothed star lock washer has two functions: 
(1) keep the bolt from loosening, and (2) establishing a “good” electrical 
connection.  (One characteristic of a good and reliable electrical connection 
is that the contact between the two conductors is gas-tight.)

A flat ring lug performs two functions, (1) flat washer and (2) means for 
electrical connection to the washer via a lug. The washer cannot -- by itself 
-- form a gas-tight connection to any other conductor.

If the bolt is to be a current-carrying conductor, then a star washer must be 
placed between the ring lug and the bolt head to establish a gas-tight 
connection between the two (assuming the star has points on both sides of the 
washer).

If the bolt goes through a metal panel and is intended to enable an electrical 
connection to the panel (on the other side), then another star washer must be 
used (on the bolt) between the nut and the metal panel.  This makes a gas-tight 
connection to the nut and another gas-tight connection to the panel (and locks 
the nut).  (The tightened nut makes a gas-tight connection to the bolt.)

There are lots of other configurations.  The principle is to establish the 
current path, and then use star lock washers to establish gas-tight connections.

According to the research paper in Ted Eckert’s message, the star washer will 
cut through the paint and establish a gas-tight connection.  There is no need 
to remove paint.

Best regards,
Rich





From: Scott Xe 
Sent: Friday, August 10, 2018 9:54 AM
To: ri...@ieee.org; EMC-PSTC@LISTSERV.IEEE.ORG
Subject: RE: [PSES] External toothed star washer used in earth connection

Hi Rich,

Thanks for your advice! 😊  Regarding the flat washer, can it be the flat ring 
lug of the connecting wire instead?

Between the screw head and the metal enclosure, do we need a flat washer?  That 
is to say: screw head -> flat washer -> metal enclosure -> on other side of 
metal enclosure with paint removed in the contact area with the flat ring lug 
-> flat ring lug of the earthing wire -> split ring lock washer -> plain nut to 
establish a good electrical earth connection.

Thanks and regards,

Scott

Sent from Mail<https://go.microsoft.com/fwlink/?LinkId=550986> for Windows 10

From: Richard Nute<mailto:ri...@ieee.org>
Sent: Friday, 10 August 2018 03:11 AM
To: EMC-PSTC@LISTSERV.IEEE.ORG<mailto:EMC-PSTC@LISTSERV.IEEE.ORG>
Subject: Re: [PSES] External toothed star washer used in earth connection




"The lock washer should not interface between the bolt head and the metal, the 
lock washer should be between the head and a flat washer."



That locks the bolt to the flat washer so they turn together.  😊



Establishes a good electrical connection between the bolt and the flat washer!  
😊



Rich


-


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This message is fro

Re: [PSES] External toothed star washer used in earth connection

[Richard Nute]

 

Hi Scott:

 

For the sake of this discussion, a toothed star lock washer has two functions: 
(1) keep the bolt from loosening, and (2) establishing a “good” electrical 
connection.  (One characteristic of a good and reliable electrical connection 
is that the contact between the two conductors is gas-tight.)

 

A flat ring lug performs two functions, (1) flat washer and (2) means for 
electrical connection to the washer via a lug. The washer cannot -- by itself 
-- form a gas-tight connection to any other conductor.  

 

If the bolt is to be a current-carrying conductor, then a star washer must be 
placed between the ring lug and the bolt head to establish a gas-tight 
connection between the two (assuming the star has points on both sides of the 
washer).

 

If the bolt goes through a metal panel and is intended to enable an electrical 
connection to the panel (on the other side), then another star washer must be 
used (on the bolt) between the nut and the metal panel.  This makes a gas-tight 
connection to the nut and another gas-tight connection to the panel (and locks 
the nut).  (The tightened nut makes a gas-tight connection to the bolt.)  

 

There are lots of other configurations.  The principle is to establish the 
current path, and then use star lock washers to establish gas-tight connections.

 

According to the research paper in Ted Eckert’s message, the star washer will 
cut through the paint and establish a gas-tight connection.  There is no need 
to remove paint.  

 

Best regards,

Rich

 

 

 

 

 

From: Scott Xe  
Sent: Friday, August 10, 2018 9:54 AM
To: ri...@ieee.org; EMC-PSTC@LISTSERV.IEEE.ORG
Subject: RE: [PSES] External toothed star washer used in earth connection

 

Hi Rich,

 

Thanks for your advice! 😊  Regarding the flat washer, can it be the flat ring 
lug of the connecting wire instead?

 

Between the screw head and the metal enclosure, do we need a flat washer?  That 
is to say: screw head -> flat washer -> metal enclosure -> on other side of 
metal enclosure with paint removed in the contact area with the flat ring lug 
-> flat ring lug of the earthing wire -> split ring lock washer -> plain nut to 
establish a good electrical earth connection.

 

Thanks and regards,

 

Scott

 

Sent from  <https://go.microsoft.com/fwlink/?LinkId=550986> Mail for Windows 10

 

From:  <mailto:ri...@ieee.org> Richard Nute
Sent: Friday, 10 August 2018 03:11 AM
To:  <mailto:EMC-PSTC@LISTSERV.IEEE.ORG> EMC-PSTC@LISTSERV.IEEE.ORG
Subject: Re: [PSES] External toothed star washer used in earth connection

 

 

"The lock washer should not interface between the bolt head and the metal, the 
lock washer should be between the head and a flat washer."

 

That locks the bolt to the flat washer so they turn together.  😊

 

Establishes a good electrical connection between the bolt and the flat washer!  
😊

 

Rich

 


-

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Re: [PSES] External toothed star washer used in earth connection

[Scott Douglas]

Many years ago a TUV Engineer drummed into my head "the only acceptable
way" to make protective earth bonds was chassis > star > ring lug > star >
nut for ground studs pressed into the chassis.


On Fri, Aug 10, 2018, 9:54 AM Scott Xe  wrote:

> Hi Rich,
>
>
>
> Thanks for your advice! 😊  Regarding the flat washer, can it be the flat
> ring lug of the connecting wire instead?
>
>
>
> Between the screw head and the metal enclosure, do we need a flat washer?
> That is to say: screw head -> flat washer -> metal enclosure -> on other
> side of metal enclosure with paint removed in the contact area with the
> flat ring lug -> flat ring lug of the earthing wire -> split ring lock
> washer -> plain nut to establish a good electrical earth connection.
>
>
>
> Thanks and regards,
>
>
>
> Scott
>
>
>
> Sent from Mail <https://go.microsoft.com/fwlink/?LinkId=550986> for
> Windows 10
>
>
>
> *From: *Richard Nute 
> *Sent: *Friday, 10 August 2018 03:11 AM
> *To: *EMC-PSTC@LISTSERV.IEEE.ORG
> *Subject: *Re: [PSES] External toothed star washer used in earth
> connection
>
>
>
>
>
> "The lock washer should not interface between the bolt head and the metal,
> the lock washer should be between the head and a flat washer."
>
>
>
> That locks the bolt to the flat washer so they turn together.  😊
>
>
>
> Establishes a good electrical connection between the bolt and the flat
> washer!  😊
>
>
>
> Rich
>
>
>
>
>
> -
> 
>
> This message is from the IEEE Product Safety Engineering Society emc-pstc
> discussion list. To post a message to the list, send your e-mail to <
> emc-p...@ieee.org>
>
> All emc-pstc postings are archived and searchable on the web at:
> http://www.ieee-pses.org/emc-pstc.html
>
> Attachments are not permitted but the IEEE PSES Online Communities site at
> http://product-compliance.oc.ieee.org/ can be used for graphics (in
> well-used formats), large files, etc.
>
> Website: http://www.ieee-pses.org/
> Instructions: http://www.ieee-pses.org/list.html (including how to
> unsubscribe) <http://www.ieee-pses.org/list.html>
> List rules: http://www.ieee-pses.org/listrules.html
>
> For help, send mail to the list administrators:
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> Mike Cantwell 
>
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> David Heald 
>
>
> -
> 
>
> This message is from the IEEE Product Safety Engineering Society emc-pstc
> discussion list. To post a message to the list, send your e-mail to <
> emc-p...@ieee.org>
>
> All emc-pstc postings are archived and searchable on the web at:
> http://www.ieee-pses.org/emc-pstc.html
>
> Attachments are not permitted but the IEEE PSES Online Communities site at
> http://product-compliance.oc.ieee.org/ can be used for graphics (in
> well-used formats), large files, etc.
>
> Website: http://www.ieee-pses.org/
> Instructions: http://www.ieee-pses.org/list.html (including how to
> unsubscribe) <http://www.ieee-pses.org/list.html>
> List rules: http://www.ieee-pses.org/listrules.html
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Re: [PSES] External toothed star washer used in earth connection

[Scott Xe]

Hi Rich,

Thanks for your advice! 😊  Regarding the flat washer, can it be the flat ring 
lug of the connecting wire instead?

Between the screw head and the metal enclosure, do we need a flat washer?  That 
is to say: screw head -> flat washer -> metal enclosure -> on other side of 
metal enclosure with paint removed in the contact area with the flat ring lug 
-> flat ring lug of the earthing wire -> split ring lock washer -> plain nut to 
establish a good electrical earth connection.

Thanks and regards,

Scott

Sent from Mail for Windows 10

From: Richard Nute
Sent: Friday, 10 August 2018 03:11 AM
To: EMC-PSTC@LISTSERV.IEEE.ORG
Subject: Re: [PSES] External toothed star washer used in earth connection


"The lock washer should not interface between the bolt head and the metal, the 
lock washer should be between the head and a flat washer."

That locks the bolt to the flat washer so they turn together.  😊

Establishes a good electrical connection between the bolt and the flat washer!  
😊

Rich


-

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Re: [PSES] External toothed star washer used in earth connection

[Richard Nute]

Hi Ted:

Thanks for the bonding and grounding (Ingalls) report.

To me, attachment 12, current testing of the washers, was most meaningful.  The 
report notes that (internal star washer) contact area is less than a 
traditional (shipbuilding) bond.  Nevertheless, the resistance of the system 
(two coated bars separated by the washer) was 11 milliohms at 55 amps!  And 
held steady for 5 minutes!

The conclusion is star washers can be used in place of cleaning to bright metal!

Wow!
Rich


-Original Message-
From: Ted Eckert <07cf6ebeab9d-dmarc-requ...@ieee.org> 
Sent: Wednesday, August 8, 2018 11:26 AM
To: EMC-PSTC@LISTSERV.IEEE.ORG
Subject: Re: [PSES] External toothed star washer used in earth connection

These references are in relation to ship building, but may be of interest to 
anybody who wants to look at star tooth washer bonding in detail.
http://www.public.navy.mil/navsafecen/Documents/afloat/Surface/Rsrcs/References/MIL-STD-1310H.PDF
https://nsrp.org/wp-content/uploads/2015/10/Deliverable-2011-452-Improved_Bonding_Grounding_Final_Report-Ingalls_Shipbuilding.pdf

The second link even includes a table showing the torque required to penetrate 
paint with various washers. (See table 2)

Ted Eckert
Microsoft Corporation

-

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Re: [PSES] External toothed star washer used in earth connection

[Richard Nute]

 

"The lock washer should not interface between the bolt head and the metal, the 
lock washer should be between the head and a flat washer."

 

That locks the bolt to the flat washer so they turn together.  😊

 

Establishes a good electrical connection between the bolt and the flat washer!  
😊

 

Rich

 

 


-

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Re: [PSES] External toothed star washer used in earth connection

[Scott Xe]

Hi Doug,

Very interesting about oxygen free connection for long term reliability!

Thanks and regards,

Scott

On Thu, 9 Aug 2018 at 01:03, Doug Powell  wrote:

> I have used IPC guidance in the past and while they have many good things
> to say, the primary aim is for reliability.  Product safety is considered
> but of secondary importance in my view.  Based on IPC workmanship standards
> and the requirements of  product safety standards combined, best practice
> is to not rely on the star to cut through paint. If you study such
> connections by disassembling, you will see a bit of paint or a single paint
> chip at the bottom of the holes created by the star points. This is a
> resistance point which may degrade over time.  I much prefer to have the
> metal surface spot faced or masked, conductive coatings excepted.  The
> purpose is to provide and oxygen free connection so the long term corrosion
> effects are negligible.  I believe the product liability directive in
> Europe requires 10 years from the date when the product is put into
> service.  A safety earth connection seldom carries much current during its
> life and may be called into service for full fault current at any time
> during that period.
>
> Fastener torque should be high enough to secure the fastener just short of
> deforming or crushing the star or other connective parts. This may take
> some experimentation with a few test samples. Experimental test results
> always supercede the tables and calculations found in the International
> Fastener Institute (IFI) books. I use stars only for safety grounding and
> not for conductors carrying very much current such as mains; steel makes a
> comparatively poor conductor. Although there are some steep pitch stars
> made of phosphor bronze and are suitable for high current connections.
> External tooth has not been mandatory in the safety standards I use, but
> the modern GTD tolerancing methods used by mechanical engineers often
> result in fairly large holes. An internal tooth star may not engage the
> metallic surface correctly.
>
> Best of luck,  Doug
>
> --
>
> Douglas E Powell
> doug...@gmail.com
> https://www.linkedin.com/in/dougp01
>
> Sent from my Android on the Verizon 4G LTE Network
> *From:* scott...@gmail.com
> *Sent:* August 8, 2018 7:22 AM
> *To:* EMC-PSTC@LISTSERV.IEEE.ORG
> *Reply-to:* scott...@gmail.com
> *Subject:* [PSES] External toothed star washer used in earth connection
>
> Notice that it is common to use external toothed star washer to
> cut through the paint on metal enclosure instead of removing the paint for
> earthing.  The connection effectiveness may be affected with following
> things
>
>- Sharpness of teeth on washer (some toothed washers are single sided
>instead of 2-sided)
>- Material of washer
>- Paint thickness
>- Screw torque
>
> Is there any standard to give the guidance of minimum requirement for this
> purpose?
>
> Thanks and regards,
>
> Scott
> -
> 
>
> This message is from the IEEE Product Safety Engineering Society emc-pstc
> discussion list. To post a message to the list, send your e-mail to <
> emc-p...@ieee.org>
>
> All emc-pstc postings are archived and searchable on the web at:
> http://www.ieee-pses.org/emc-pstc.html
>
> Attachments are not permitted but the IEEE PSES Online Communities site at
> http://product-compliance.oc.ieee.org/ can be used for graphics (in
> well-used formats), large files, etc.
>
> Website: http://www.ieee-pses.org/
> Instructions: http://www.ieee-pses.org/list.html (including how to
> unsubscribe) <http://www.ieee-pses.org/list.html>
> List rules: http://www.ieee-pses.org/listrules.html
>
> For help, send mail to the list administrators:
> Scott Douglas 
> Mike Cantwell 
>
> For policy questions, send mail to:
> Jim Bacher 
> David Heald 
>

-

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Re: [PSES] External toothed star washer used in earth connection

[Scott Xe]

Hi Dave,

It is new to me about this requirement.

Thanks,

Scott


On Thu, 9 Aug 2018 at 01:39, Nyffenegger, Dave 
wrote:

> Also keep in mind the NSF standards generally prohibit the use of external
> tooth star washers in food zones in food certified products.
>
> -Dave
>
>
>
> *From:* Doug Powell [mailto:doug...@gmail.com]
> *Sent:* Wednesday, August 08, 2018 1:04 PM
> *To:* EMC-PSTC@LISTSERV.IEEE.ORG
> *Subject:* Re: [PSES] External toothed star washer used in earth
> connection
>
>
>
> I have used IPC guidance in the past and while they have many good things
> to say, the primary aim is for reliability.  Product safety is considered
> but of secondary importance in my view.  Based on IPC workmanship standards
> and the requirements of  product safety standards combined, best practice
> is to not rely on the star to cut through paint. If you study such
> connections by disassembling, you will see a bit of paint or a single paint
> chip at the bottom of the holes created by the star points. This is a
> resistance point which may degrade over time.  I much prefer to have the
> metal surface spot faced or masked, conductive coatings excepted.  The
> purpose is to provide and oxygen free connection so the long term corrosion
> effects are negligible.  I believe the product liability directive in
> Europe requires 10 years from the date when the product is put into
> service.  A safety earth connection seldom carries much current during its
> life and may be called into service for full fault current at any time
> during that period.
>
>
>
> Fastener torque should be high enough to secure the fastener just short of
> deforming or crushing the star or other connective parts. This may take
> some experimentation with a few test samples. Experimental test results
> always supercede the tables and calculations found in the International
> Fastener Institute (IFI) books. I use stars only for safety grounding and
> not for conductors carrying very much current such as mains; steel makes a
> comparatively poor conductor. Although there are some steep pitch stars
> made of phosphor bronze and are suitable for high current connections.
> External tooth has not been mandatory in the safety standards I use, but
> the modern GTD tolerancing methods used by mechanical engineers often
> result in fairly large holes. An internal tooth star may not engage the
> metallic surface correctly.
>
>
>
> Best of luck,  Doug
>
>
>
> --
>
>
>
> Douglas E Powell
>
> doug...@gmail.com
>
> https://www.linkedin.com/in/dougp01
>
> Sent from my Android on the Verizon 4G LTE Network
>
> *From:* scott...@gmail.com
>
> *Sent:* August 8, 2018 7:22 AM
>
> *To:* EMC-PSTC@LISTSERV.IEEE.ORG
>
> *Reply-to:* scott...@gmail.com
>
> *Subject:* [PSES] External toothed star washer used in earth connection
>
>
>
> Notice that it is common to use external toothed star washer to
> cut through the paint on metal enclosure instead of removing the paint for
> earthing.  The connection effectiveness may be affected with following
> things
>
>- Sharpness of teeth on washer (some toothed washers are single sided
>instead of 2-sided)
>- Material of washer
>- Paint thickness
>- Screw torque
>
> Is there any standard to give the guidance of minimum requirement for this
> purpose?
>
>
>
> Thanks and regards,
>
>
>
> Scott
>
> -
> 
>
> This message is from the IEEE Product Safety Engineering Society emc-pstc
> discussion list. To post a message to the list, send your e-mail to <
> emc-p...@ieee.org>
>
> All emc-pstc postings are archived and searchable on the web at:
> http://www.ieee-pses.org/emc-pstc.html
>
> Attachments are not permitted but the IEEE PSES Online Communities site at
> http://product-compliance.oc.ieee.org/ can be used for graphics (in
> well-used formats), large files, etc.
>
> Website: http://www.ieee-pses.org/
> Instructions: http://www.ieee-pses.org/list.html (including how to
> unsubscribe) <http://www.ieee-pses.org/list.html>
> List rules: http://www.ieee-pses.org/listrules.html
>
> For help, send mail to the list administrators:
> Scott Douglas 
> Mike Cantwell 
>
> For policy questions, send mail to:
> Jim Bacher 
> David Heald 
>
> -
> 
>
> This message is from the IEEE Product Safety Engineering Society emc-pstc
> discussion list. To post a message to the list, send your e-mail to <
> emc-p...@ieee.org>
>
> All emc-pstc postings are archived and searchable on the web at:
> http:/

Re: [PSES] External toothed star washer used in earth connection

[Scott Xe]

Hi Ted,

Thanks for your reference!  I downloaded the 1st doc document successfully
but failed to reach the 2nd document.  Can you do me a favor sending a copy
to me.

Thanks and regards,

Scott

On Thu, 9 Aug 2018 at 03:00, Ted Eckert <
07cf6ebeab9d-dmarc-requ...@ieee.org> wrote:

> These references are in relation to ship building, but may be of interest
> to anybody who wants to look at star tooth washer bonding in detail.
>
> http://www.public.navy.mil/navsafecen/Documents/afloat/Surface/Rsrcs/References/MIL-STD-1310H.PDF
>
> https://nsrp.org/wp-content/uploads/2015/10/Deliverable-2011-452-Improved_Bonding_Grounding_Final_Report-Ingalls_Shipbuilding.pdf
>
> The second link even includes a table showing the torque required to
> penetrate paint with various washers. (See table 2)
>
> Ted Eckert
> Microsoft Corporation
>
> The opinions expressed are my own and do not necessarily reflect those of
> my employer, the Navy, the ship-building industry or or the American
> Association of Manufacturers of Internal and External Tooth Washers.
>
> -Original Message-
> From: Brian O'Connell 
> Sent: Wednesday, August 8, 2018 10:30 AM
> To: EMC-PSTC@LISTSERV.IEEE.ORG
> Subject: Re: [PSES] External toothed star washer used in earth connection
>
> Am not aware that  it is "common to use external toothed star washer to
> cut through the paint". It has been my experience that NRTLs, SCC members,
> NBs, and the Vulcan Science Academy look askance at such construction, and
> tend to require a paint-free zone for electrical power ground bond stuff.
>
> Agree with Doug that IPC610 does not say much about safety, other than
> that clearance (does not mention creepage) is part of the design
> considerations and shall be determined by other standards (but does
> reference the min spacing table from IPC2221). Another thing that IPC610 is
> careful to do is to not use star/toothed washers as examples of hardware
> securement - only the split lock washer is used in construction examples.
>
> The lock washer should not interface between the bolt head and the metal,
> the lock washer should be between the head and a flat washer. A decent
> example of reliable ground bond construction can be found in the CSA
> engineering manual for 60950-1. And 40A ground bond test for all, and all
> for one.
>
> Brian
>
>
>
> From: Doug Powell [mailto:doug...@gmail.com]
> Sent: Wednesday, August 08, 2018 10:04 AM
> To: EMC-PSTC@LISTSERV.IEEE.ORG
> Subject: Re: [PSES] External toothed star washer used in earth connection
>
> I have used IPC guidance in the past and while they have many good things
> to say, the primary aim is for reliability.  Product safety is considered
> but of secondary importance in my view.  Based on IPC workmanship standards
> and the requirements of  product safety standards combined, best practice
> is to not rely on the star to cut through paint. If you study such
> connections by disassembling, you will see a bit of paint or a single paint
> chip at the bottom of the holes created by the star points. This is a
> resistance point which may degrade over time.  I much prefer to have the
> metal surface spot faced or masked, conductive coatings excepted.  The
> purpose is to provide and oxygen free connection so the long term corrosion
> effects are negligible.  I believe the product liability directive in
> Europe requires 10 years from the date when the product is put into
> service.  A safety earth connection seldom carries much current during its
> life and may be called into service for full fault current at any time
> during that period.
>
> Fastener torque should be high enough to secure the fastener just short of
> deforming or crushing the star or other connective parts. This may take
> some experimentation with a few test samples. Experimental test results
> always supercede the tables and calculations found in the International
> Fastener Institute (IFI) books. I use stars only for safety grounding and
> not for conductors carrying very much current such as mains; steel makes a
> comparatively poor conductor. Although there are some steep pitch stars
> made of phosphor bronze and are suitable for high current connections.
> External tooth has not been mandatory in the safety standards I use, but
> the modern GTD tolerancing methods used by mechanical engineers often
> result in fairly large holes. An internal tooth star may not engage the
> metallic surface correctly.
>
> Best of luck,  Doug
>
> --
>
> Douglas E Powell
> doug...@gmail.com
>
> https://na01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fwww.linkedin.com%2Fin%2Fdougp01&data=02%7C01%7Cted.eckert%40microsoft.com%7Cde232d4406a343b52e2808d5fd569820%7C7

Re: [PSES] External toothed star washer used in earth connection

[Scott Xe]

It really happens in white goods.  They want to streamline the process
using toothed star washer.  I fully agree your point and will read the
reference book later to understand it in greater detail.  IPC is generally
for normal electronic assembly and did not remember any reference for
earthing connection.

What is CSA engineering manual for 60950-1?  Is it explanatory note for
60950-1 requirements?

Thanks and regards,

Scott

On Thu, 9 Aug 2018 at 01:44, Brian O'Connell 
wrote:

> Am not aware that  it is "common to use external toothed star washer to
> cut through the paint". It has been my experience that NRTLs, SCC members,
> NBs, and the Vulcan Science Academy look askance at such construction, and
> tend to require a paint-free zone for electrical power ground bond stuff.
>
> Agree with Doug that IPC610 does not say much about safety, other than
> that clearance (does not mention creepage) is part of the design
> considerations and shall be determined by other standards (but does
> reference the min spacing table from IPC2221). Another thing that IPC610 is
> careful to do is to not use star/toothed washers as examples of hardware
> securement - only the split lock washer is used in construction examples.
>
> The lock washer should not interface between the bolt head and the metal,
> the lock washer should be between the head and a flat washer. A decent
> example of reliable ground bond construction can be found in the CSA
> engineering manual for 60950-1. And 40A ground bond test for all, and all
> for one.
>
> Brian
>
>
>
> From: Doug Powell [mailto:doug...@gmail.com]
> Sent: Wednesday, August 08, 2018 10:04 AM
> To: EMC-PSTC@LISTSERV.IEEE.ORG
> Subject: Re: [PSES] External toothed star washer used in earth connection
>
> I have used IPC guidance in the past and while they have many good things
> to say, the primary aim is for reliability.  Product safety is considered
> but of secondary importance in my view.  Based on IPC workmanship standards
> and the requirements of  product safety standards combined, best practice
> is to not rely on the star to cut through paint. If you study such
> connections by disassembling, you will see a bit of paint or a single paint
> chip at the bottom of the holes created by the star points. This is a
> resistance point which may degrade over time.  I much prefer to have the
> metal surface spot faced or masked, conductive coatings excepted.  The
> purpose is to provide and oxygen free connection so the long term corrosion
> effects are negligible.  I believe the product liability directive in
> Europe requires 10 years from the date when the product is put into
> service.  A safety earth connection seldom carries much current during its
> life and may be called into service for full fault current at any time
> during that period.
>
> Fastener torque should be high enough to secure the fastener just short of
> deforming or crushing the star or other connective parts. This may take
> some experimentation with a few test samples. Experimental test results
> always supercede the tables and calculations found in the International
> Fastener Institute (IFI) books. I use stars only for safety grounding and
> not for conductors carrying very much current such as mains; steel makes a
> comparatively poor conductor. Although there are some steep pitch stars
> made of phosphor bronze and are suitable for high current connections.
> External tooth has not been mandatory in the safety standards I use, but
> the modern GTD tolerancing methods used by mechanical engineers often
> result in fairly large holes. An internal tooth star may not engage the
> metallic surface correctly.
>
> Best of luck,  Doug
>
> --
>
> Douglas E Powell
> doug...@gmail.com
> https://www.linkedin.com/in/dougp01
> Sent from my Android on the Verizon 4G LTE Network
> From: scott...@gmail.com
> Sent: August 8, 2018 7:22 AM
> To: EMC-PSTC@LISTSERV.IEEE.ORG
> Reply-to: scott...@gmail.com
> Subject: [PSES] External toothed star washer used in earth connection
>
> Notice that it is common to use external toothed star washer to
> cut through the paint on metal enclosure instead of removing the paint for
> earthing.  The connection effectiveness may be affected with following
> things
> • Sharpness of teeth on washer (some toothed washers are single sided
> instead of 2-sided)
> • Material of washer
> • Paint thickness
> • Screw torque
> Is there any standard to give the guidance of minimum requirement for this
> purpose?
>
> Thanks and regards,
>
> Scott
>
> -
> 
> This message is from the IEEE Product Safety Engineering Society emc-pstc
> discussion 

Re: [PSES] External toothed star washer used in earth connection

[Scott Xe]

John,

Appropriate torque is different to set due to various connection
mechanism.  However you point of double-sided washer is essential.  We had
a case that the production incorrectly installed the washer upside-down
causing the failure in earth continuity test.

Thanks and regards,

Scott

On Wed, 8 Aug 2018 at 23:03, John Woodgate  wrote:

> The screw torque is specified in several standards, but the acceptance
> criterion is usually the high-current resistance test. It's really up to
> the manufacturer of the product to specify the requirements of the
> washer, which must be double-sided so that it doesn't matter which way up
> it is installed.
>
> John Woodgate OOO-Own Opinions Only
> J M Woodgate and Associates www.woodjohn.uk
> Rayleigh, Essex UK
>
> On 2018-08-08 14:21, Scott Xe wrote:
>
> Notice that it is common to use external toothed star washer to
> cut through the paint on metal enclosure instead of removing the paint for
> earthing.  The connection effectiveness may be affected with following
> things
>
>- Sharpness of teeth on washer (some toothed washers are single sided
>instead of 2-sided)
>- Material of washer
>- Paint thickness
>- Screw torque
>
> Is there any standard to give the guidance of minimum requirement for this
> purpose?
>
> Thanks and regards,
>
> Scott
> -
> 
>
> This message is from the IEEE Product Safety Engineering Society emc-pstc
> discussion list. To post a message to the list, send your e-mail to <
> emc-p...@ieee.org>
>
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> http://www.ieee-pses.org/emc-pstc.html
>
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> http://product-compliance.oc.ieee.org/ can be used for graphics (in
> well-used formats), large files, etc.
>
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Re: [PSES] External toothed star washer used in earth connection

[Nyffenegger, Dave]

Also keep in mind the NSF standards generally prohibit the use of external 
tooth star washers in food zones in food certified products.
-Dave

From: Doug Powell [mailto:doug...@gmail.com]
Sent: Wednesday, August 08, 2018 1:04 PM
To: EMC-PSTC@LISTSERV.IEEE.ORG
Subject: Re: [PSES] External toothed star washer used in earth connection

I have used IPC guidance in the past and while they have many good things to 
say, the primary aim is for reliability.  Product safety is considered but of 
secondary importance in my view.  Based on IPC workmanship standards and the 
requirements of  product safety standards combined, best practice is to not 
rely on the star to cut through paint. If you study such connections by 
disassembling, you will see a bit of paint or a single paint chip at the bottom 
of the holes created by the star points. This is a resistance point which may 
degrade over time.  I much prefer to have the metal surface spot faced or 
masked, conductive coatings excepted.  The purpose is to provide and oxygen 
free connection so the long term corrosion effects are negligible.  I believe 
the product liability directive in Europe requires 10 years from the date when 
the product is put into service.  A safety earth connection seldom carries much 
current during its life and may be called into service for full fault current 
at any time during that period.

Fastener torque should be high enough to secure the fastener just short of 
deforming or crushing the star or other connective parts. This may take some 
experimentation with a few test samples. Experimental test results always 
supercede the tables and calculations found in the International Fastener 
Institute (IFI) books. I use stars only for safety grounding and not for 
conductors carrying very much current such as mains; steel makes a 
comparatively poor conductor. Although there are some steep pitch stars made of 
phosphor bronze and are suitable for high current connections. External tooth 
has not been mandatory in the safety standards I use, but the modern GTD 
tolerancing methods used by mechanical engineers often result in fairly large 
holes. An internal tooth star may not engage the metallic surface correctly.

Best of luck,  Doug

--

Douglas E Powell
doug...@gmail.com<mailto:doug...@gmail.com>
https://www.linkedin.com/in/dougp01

Sent from my Android on the Verizon 4G LTE Network
From: scott...@gmail.com
Sent: August 8, 2018 7:22 AM
To: EMC-PSTC@LISTSERV.IEEE.ORG
Reply-to: scott...@gmail.com
Subject: [PSES] External toothed star washer used in earth connection


Notice that it is common to use external toothed star washer to cut through the 
paint on metal enclosure instead of removing the paint for earthing.  The 
connection effectiveness may be affected with following things

  *   Sharpness of teeth on washer (some toothed washers are single sided 
instead of 2-sided)
  *   Material of washer
  *   Paint thickness
  *   Screw torque
Is there any standard to give the guidance of minimum requirement for this 
purpose?

Thanks and regards,

Scott
-


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For p

Re: [PSES] External toothed star washer used in earth connection

[Doug Powell]

 I have used IPC guidance in the past and while they have many good things to say, the primary aim is for reliability.  Product safety is considered but of secondary importance in my view.  Based on IPC workmanship standards and the requirements of  product safety standards combined, best practice is to not rely on the star to cut through paint. If you study such connections by disassembling, you will see a bit of paint or a single paint chip at the bottom of the holes created by the star points. This is a resistance point which may degrade over time.  I much prefer to have the metal surface spot faced or masked, conductive coatings excepted.  The purpose is to provide and oxygen free connection so the long term corrosion effects are negligible.  I believe the product liability directive in Europe requires 10 years from the date when the product is put into service.  A safety earth connection seldom carries much current during its life and may be called into service for full fault current at any time during that period. Fastener torque should be high enough to secure the fastener just short of deforming or crushing the star or other connective parts. This may take some experimentation with a few test samples. Experimental test results always supercede the tables and calculations found in the International Fastener Institute (IFI) books. I use stars only for safety grounding and not for conductors carrying very much current such as mains; steel makes a comparatively poor conductor. Although there are some steep pitch stars made of phosphor bronze and are suitable for high current connections. External tooth has not been mandatory in the safety standards I use, but the modern GTD tolerancing methods used by mechanical engineers often result in fairly large holes. An internal tooth star may not engage the metallic surface correctly. Best of luck,  Doug--Douglas E Powelldoug...@gmail.comhttps://www.linkedin.com/in/dougp01  Sent from my Android on the Verizon 4G LTE Network   From: scott...@gmail.comSent: August 8, 2018 7:22 AMTo: EMC-PSTC@LISTSERV.IEEE.ORGReply-to: scott...@gmail.comSubject: [PSES] External toothed star washer used in earth connection  Notice that it is common to use external toothed star washer to cut through the paint on metal enclosure instead of removing the paint for earthing.  The connection effectiveness may be affected with following thingsSharpness of teeth on washer (some toothed washers are single sided instead of 2-sided)Material of washerPaint thicknessScrew torqueIs there any standard to give the guidance of minimum requirement for this purpose?Thanks and regards,Scott
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Re: [PSES] External toothed star washer used in earth connection

[Schmidt, Mark]

Hi Scott,

Can’t remember for sure (since I no longer have access to a copy of the 
standard) but IPC-A-610 may provide guidance on acceptability criteria for that.

Regards,
Mark

From: Scott Xe [mailto:scott...@gmail.com]
Sent: Wednesday, August 08, 2018 9:22 AM
To: EMC-PSTC@LISTSERV.IEEE.ORG
Subject: [PSES] External toothed star washer used in earth connection

Notice that it is common to use external toothed star washer to cut through the 
paint on metal enclosure instead of removing the paint for earthing.  The 
connection effectiveness may be affected with following things

  *   Sharpness of teeth on washer (some toothed washers are single sided 
instead of 2-sided)
  *   Material of washer
  *   Paint thickness
  *   Screw torque
Is there any standard to give the guidance of minimum requirement for this 
purpose?

Thanks and regards,

Scott
-


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Re: [PSES] External toothed star washer used in earth connection

[John Woodgate]

The screw torque is specified in several standards, but the acceptance 
criterion is usually the high-current resistance test. It's really up to 
the manufacturer of the product to specify the requirements of the 
washer, which must be double-sided so that it doesn't matter which way 
up it is installed.


John Woodgate OOO-Own Opinions Only
J M Woodgate and Associates www.woodjohn.uk
Rayleigh, Essex UK

On 2018-08-08 14:21, Scott Xe wrote:
Notice that it is common to use external toothed star washer to 
cut through the paint on metal enclosure instead of removing the paint 
for earthing.  The connection effectiveness may be affected with 
following things


  * Sharpness of teeth on washer (some toothed washers are single
sided instead of 2-sided)
  * Material of washer
  * Paint thickness
  * Screw torque

Is there any standard to give the guidance of minimum requirement for 
this purpose?


Thanks and regards,

Scott
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[PSES] External toothed star washer used in earth connection

[Scott Xe]

Notice that it is common to use external toothed star washer to cut through
the paint on metal enclosure instead of removing the paint for earthing.
The connection effectiveness may be affected with following things

   - Sharpness of teeth on washer (some toothed washers are single sided
   instead of 2-sided)
   - Material of washer
   - Paint thickness
   - Screw torque

Is there any standard to give the guidance of minimum requirement for this
purpose?

Thanks and regards,

Scott

-

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discussion list. To post a message to the list, send your e-mail to 


All emc-pstc postings are archived and searchable on the web at:
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formats), large files, etc.

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