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#141280 - 07/12/04 03:41 PM Little hole on British plugs
Hutch Offline
Member

Registered: 05/27/02
Posts: 383
Loc: South Oxfordshire, UK
On the Russian 220V thread, Paul said ...
 Quote:
The little hole on British plugs for the earth pin is a curious feature though (or I should say "was" I suppose, as you don't find it on current plugs.

It seems more likely to me that it was provided simply as a convenient means for grounding to the house electrical system, e.g. to provide a signal earth for a radio.


I only vaguely recall this feature Paul. Do you have any pictures of that you could post? Was it new to the older 13A type? - I don't recall seeing anything like described on the older 15A standard.

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#141281 - 07/12/04 05:39 PM Re: Little hole on British plugs
32VAC Offline
Member

Registered: 06/28/04
Posts: 203
Loc: Alice Springs, NT, Australia
I can remember some Australian plugs had this too. I'll have a scout through my boxes of fitting s& see what I come up with also.

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#141282 - 07/12/04 10:33 PM Re: Little hole on British plugs
Trumpy Offline

Member

Registered: 07/05/02
Posts: 8540
Loc: SI,New Zealand
32VAC,
Welcome to ECN mate!.
Great to have another Member from down this way on the BB.
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#141283 - 07/12/04 11:56 PM Re: Little hole on British plugs
32VAC Offline
Member

Registered: 06/28/04
Posts: 203
Loc: Alice Springs, NT, Australia
Thanks, Trumpy. Cold where you are? Its about 17 degrees here. Another thing that I have noticed on older Clipsal plugs (end of bakelite/beginning of PVC plugtops such as the old part numbers 401s, 417s 423s & early 439s)was the way the pins were made with a 'notch' in the end. was this done to save material or just a manufacturing or design 'feature'?

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#141284 - 07/13/04 05:12 AM Re: Little hole on British plugs
pauluk Offline
Member

Registered: 08/11/01
Posts: 7693
Loc: Norfolk, England
Welcome 32VAC.

Here's the feature on a typical 1960's vintage BS1363 MK plug:




Ian,
Yes, this was found on BS546 as well. Here's a 15A BS546 plug of similar vintage:



And an older 5-amp BS546 plug:


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#141285 - 07/14/04 10:16 AM Re: Little hole on British plugs
uksparky Offline
Member

Registered: 07/06/04
Posts: 199
Loc: UK
You beat me to it Paul.. Is there anything you haven't got in your collection??

Digicam software is playing up again ..it will teach me not to instal any 'patch' from Microsoft everagain
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#141286 - 07/20/04 08:09 PM Re: Little hole on British plugs
chipmunk Offline
Member

Registered: 07/20/04
Posts: 142
Loc: Southampton, UK
I always assumed that this feature was to provide a signal earth/ground for a radio, I have used it more recently in the UK, (with an olde plugge LOL) to obtain an ESD earth for working on PC parts.. yes, I know, could be nasty if the earth isn't connected on that socket, I used to carry a 13A socket tester too. I don't think it was to save material though, some method of connecting to the earthing system would be the obvious reason, and old radios dating from this period often used 2 wire cords with a requirement for a signal ground... I guess they allowed you to connect to it for this purpose without the earth wire coming near the live wires in the plug?

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#141287 - 07/21/04 02:25 AM Re: Little hole on British plugs
pauluk Offline
Member

Registered: 08/11/01
Posts: 7693
Loc: Norfolk, England
Yes, that's the sort of use I always imagined for it. Most old valve/tube radios of the 1940s/50s had aerial and earth terminals on the back, and being AC/DC live-chassis models had a 2-wire cord.

The earth terminal was generally wired to the chassis via a suitable capacitor to provide a low-impedance path for RF but block 50Hz mains.

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#141288 - 08/18/04 02:31 AM Re: Little hole on British plugs
pauluk Offline
Member

Registered: 08/11/01
Posts: 7693
Loc: Norfolk, England
Received by e-mail:
 Quote:
Have been interested to read your postings re. above on ECN.

I believe that the hole was provided to enable visual inspection of the earth wire/terminal without removing the cover of the plug.

Many amateurs wired plugs with all 3 wires cut to the same length. this resulted in a real risk of the earth wire pulling out of the terminal.

The small hole enabled the user to verify that that the earth was still attached.

Please feel free to post this on the forum. I can not post as am not a member.

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