The Straight Dope

Go Back   Straight Dope Message Board > Main > Comments on Cecil's Columns/Staff Reports

Reply
 
Thread Tools Display Modes
  #1  
Old 08-28-2011, 10:40 AM
wbenzoni wbenzoni is offline
Guest
 
Join Date: Jul 2006
Why are there holes in the prongs of electrical plugs

The holes are to help with manufacturing.
Reply With Quote
Advertisements  
  #2  
Old 08-28-2011, 10:43 AM
wbenzoni wbenzoni is offline
Guest
 
Join Date: Jul 2006
see http://www.nema.org/stds/wd6.cfm
Reply With Quote
  #3  
Old 08-29-2011, 12:44 PM
jpdemers jpdemers is offline
Guest
 
Join Date: Aug 2011
The holes were used at one time to help retain the plug

The earliest use of a hole in the blade of an electric plug that I can find is in US patent 1341468 (1920) where they serve as detents to hold the plug in place. Another 1920 patent (US 1352817) shows the holes in passing, without comment, as if they were already routine by that date.

No doubt manufacturers took advantage of the holes in the blades when designing their machinery, as they provide convenient "handles" and reference points that are missing from a plain strip of metal. While the holes have lost their original utility, eliminating them would require the needless replacement of a lot of expensive equipment, so they remain in place. New equipment is probably designed to take advantage of them as well, perpetuating the mysterious holes for future generations to puzzle over.

ANSI/NEMA standard WD 6-2002, which states that the holes are "optional", nonetheless specifies exactly where they should be located and exactly what size they should be -- presumably to rule out alternative designs that might weaken the blade.
Reply With Quote
  #4  
Old 09-02-2011, 12:09 AM
Barboelsch Barboelsch is offline
Guest
 
Join Date: May 2005
Reasons for holes in plugs

Someone mentioned there are no holes in plugs in countries like Germany. Wrong. In countries with a voltage of 230 V there usually is a third contact just for security. In France, this security pin sticks out in the socked and jams right into the plug, in Germany they have two little contacts left and right instead. So plug manufacturers obviously say 'hey, why produce two different plugs, we just fit all of them with both features so we can sell them in France AND Germany.

This an intelligent thought, and - in theory - someone might have the same thing in mind in America. Not that I knew - do the Canadians have something like a third prong?

In the Philippines they use exactly the US-shaped plugs but on networks that run 230 Volts. This certainly calls for additional security!

Oh: have fun bringing your appliances over there and plugging them in...
Reply With Quote
  #5  
Old 09-02-2011, 01:09 AM
dropzone dropzone is offline
Charter Member
 
Join Date: May 2000
Location: Cloud Cuckoo Land
Posts: 22,069
And why is it? Under which electrical standard, and why, might these holes promote safety, as the sockets had already gone all standard?

EU and Friends (looking around): Standardish?

Last edited by dropzone; 09-02-2011 at 01:13 AM..
Reply With Quote
  #6  
Old 09-03-2011, 10:55 AM
signal11 signal11 is offline
Guest
 
Join Date: Apr 2009
Quote:
Originally Posted by Barboelsch View Post
Someone mentioned there are no holes in plugs in countries like Germany. Wrong. In countries with a voltage of 230 V there usually is a third contact just for security. In France, this security pin sticks out in the socked and jams right into the plug, in Germany they have two little contacts left and right instead. So plug manufacturers obviously say 'hey, why produce two different plugs, we just fit all of them with both features so we can sell them in France AND Germany.

This an intelligent thought, and - in theory - someone might have the same thing in mind in America. Not that I knew - do the Canadians have something like a third prong?

In the Philippines they use exactly the US-shaped plugs but on networks that run 230 Volts. This certainly calls for additional security!

Oh: have fun bringing your appliances over there and plugging them in...
This discussion is regarding the holes on the prongs themselves, as can be seen here:

http://en.wikipedia.org/wiki/File:NE...ower-Plugs.jpg

Here is a picture of Japanese style plug, the standards for which are almost identical to the US standard sans holes.

http://upload.wikimedia.org/wikipedi.../9a/A_plug.jpg

The third "hole" and/or contact you are referring to are for the grounding pin. This serves the same function as the third prong on the right in the first picture.
Reply With Quote
  #7  
Old 09-12-2011, 10:27 AM
Rickymouse Rickymouse is offline
Guest
 
Join Date: Sep 2011
Why do you know so much about the prongs jpdemers, it seems like something someone would know nothing about unless they are in an associated field.
Reply With Quote
Reply

Bookmarks

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is Off
HTML code is Off

Forum Jump


All times are GMT -5. The time now is 08:00 AM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2014, vBulletin Solutions, Inc.

Send questions for Cecil Adams to: cecil@chicagoreader.com

Send comments about this website to: webmaster@straightdope.com

Terms of Use / Privacy Policy

Advertise on the Straight Dope!
(Your direct line to thousands of the smartest, hippest people on the planet, plus a few total dipsticks.)

Publishers - interested in subscribing to the Straight Dope?
Write to: sdsubscriptions@chicagoreader.com.

Copyright 2013 Sun-Times Media, LLC.