Power tool cords

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alcon192

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On the hot and netural blades of a cord, I have notices a small round hole and was wondering what it is for. I was told recently it is a OSHA requirement.
 
They are there for wrapping the stripped end of romex so it won't fall out and you don't have to use duct tape to hold it together...hehehe:grin:

Seriously though...Have seen them and never thought twice about them...Now I wonder what the purpose is.
 
Looking around the web I found these opinions on what the holes are there for.
1. Used to hold the parts together in the molding of the cord process (Towzzer also said this)
2. Used to install a lock to prevent unautherized use (I doubt this one)
3. Use to be used to help hold the plug into the receptacle via "nubbs" inside the receptacle (never seen an receptacle with "nubbs" inside it)
4. Used to dissapate heat...(we always take surface area away to dissapate heat right?)


I vote for #1
 
I thought it had something to do with child proof outlets or maybe it was for those outlets with the ground UP.
 
Didn't take the time to research the OSHA technical sections, but found it a fascinating question. The best I found was in a wikipedia article where the author states,
"The hole, near end of the power (non-ground) conductors of NEMA plugs, is included in the design to aid in arc quenching, referring to the successful extinguishing of the electric arc, when the plug is removed under power." Please use caution visiting the page,
http://en.wikipedia.org/wiki/NEMA_connector
 
I was a factory electrician for years at a company that made these "prongs". The holes were used in the stamping process as part of the carrier strip to guide the strip of brass through the progressive stamping dies. They were used in the automated application process to hold each terminal as it was crimped on the wire. They were then used in the injection molding equipment to hold and locate the prong while the plug body was being molded. I don't know if they have another purpose or not, but they sure were indespensible during the manufacturing process.
 
mdshunk said:
I was a factory electrician for years at a company that made these "prongs".
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Well, you look like a young whelp even now, so you may have come after their inception, and they adapted the machines to the product. Maybe?

I took stuff apart when I was a whelp, and I do remember there being bumps on the springy contact inside lamp-cord-type extension-cord ends.
 
LarryFine said:
Well, you look like a young whelp even now, so you may have come after their inception, and they adapted the machines to the product. Maybe?
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Fair enough. Hard to say. The holes were very helpful during manufacturing, is all I can say for sure. The "bump" on the receptacle contact wiper is called a "latch tab" on the print for that particular piece. We made those also. Under the scope, or on an optical comparator, it actually is more of a "ramp" rather than a true bump. I'm just not sure if the latch bump feature on the contact wiper was added to take advantage of the hole that was in the prong for manufacturing, or if the latch tab and the hole to latch onto it were conceived at the same time. Not all receptacle wipers feature this latch bump to take advantage of these holes in the prongs.
 
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I'm not sure which manufacturers who are doing this, but those holes are very convienent in the ability to "lock out" a piece of equipment. The holes are designed, such that a special paddle lock can be used that goes through the holes, qualifying as a lock out (couldn't be inserted into receptacle).

It's already has a patent, here is a connection for more of the story.

I think this is the second time around on this concept. Let me do some "homework" on the issue and get back , as to the history of it.
 
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