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#12824 - 08/18/02 07:19 AM Male attachment plug prongs  
jes  Offline
Member
Joined: Jul 2002
Posts: 103
CT
OK, here's a trivia question.
Why do male attachment plug prongs (some, not all) have round holes through them near the ends??? I DON'T know the answer!!


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#12825 - 08/18/02 08:04 AM Re: Male attachment plug prongs  
walrus  Offline
Member
Joined: Jul 2002
Posts: 680
Bangor Me. USA
Lockout, tagout?


#12826 - 08/18/02 11:34 AM Re: Male attachment plug prongs  
NJwirenut  Offline
Member
Joined: Sep 2001
Posts: 806
Bergen County, NJ
Helps hold the plug into the receptacle. There is a corresponding "dimple" in the contact spring, which "locks" into the hole in the plug blade.


#12827 - 08/18/02 11:54 AM Re: Male attachment plug prongs  
sparky66wv  Offline
Member
Joined: Nov 2000
Posts: 2,236
West Virginia
And here I thought they were to clean the contacts...?

Makes sense though...


-Virgil
Residential/Commercial Inspector
5 Star Inspections
Member IAEI

#12828 - 08/18/02 04:33 PM Re: Male attachment plug prongs  
pauluk  Offline
Member
Joined: Aug 2001
Posts: 7,520
Norfolk, England
Don't forget that the holes also make it easy to wrap bare wires for Mexican-style extension cords.... [Linked Image]


#12829 - 08/18/02 07:45 PM Re: Male attachment plug prongs  
jes  Offline
Member
Joined: Jul 2002
Posts: 103
CT
Interesting comments but:
The holes have been there a LONG time... long before lockout/tagout came on the scene, however I have seen some loto devices that use the holes.
The contact idea is interesting but I've never seen a receptacle with contact strips having dimples...
A cleaning function is interesting...could be!
Still searching!


#12830 - 08/18/02 09:53 PM Re: Male attachment plug prongs  
Anonymous
Unregistered

I was told back in school that a long time ago receptacles had little spring loaded balls that would engage those holes.


#12831 - 08/19/02 07:48 AM Re: Male attachment plug prongs  
Trainwire  Offline
Member
Joined: Mar 2002
Posts: 360
Strasburg,PA,USA
My bet is that they are part of the manufacturing process, like maybe how they are hung onto when they mold the plug around them.
Trainwire


#12832 - 08/19/02 08:05 AM Re: Male attachment plug prongs  
Texas_Ranger  Offline
Member
Joined: Dec 2001
Posts: 2,396
Vienna, Austria
I've got a 1970ies Sony stereo with NEMA plug and an unswitched outlet. When I push in a plug I can feel that the prongs get locked when fully inserted.
BTW, I was close to using the mexican style cord. I replaced a light switch in a room without a window, so I needed some temporary lighting. The only thing I could find was an imported US table lamp with an adaptor which has been hooked up forever in our living room. When I tried to hook it up I nearly got a fit. The adaptor was as stone aged as the lamp and it wouldn't fit Schuko receptacles! Finally I pulled two (illegal) ungrounded extension cords through the appartment and hooked my lamp up. SO much about being able to stick to codes...


#12833 - 12/04/06 06:13 AM Re: Male attachment plug prongs  
Luketrician  Offline
Member
Joined: Jul 2006
Posts: 272
Sale Creek, TN USA
Quote
Don't forget that the holes also make it easy to wrap bare wires for Mexican-style extension cords....


I'm not an old timer on this site but I bet there are some pics of this in the violation photo forum. I've seen that practice done plenty of times, unfortunately. [Linked Image]

Luke


Luke Clarke
Electrical Planner for TVA.


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