Why Do U.S. Electrical Plugs Have Holes in the Blades?(youtube.com)
youtube.com
Why Do U.S. Electrical Plugs Have Holes in the Blades?
https://www.youtube.com/watch?v=udNXMAflbU8
4 comments
I'm not sure if you watched the video, but if I understood your first point, he debunked that by testing it on a wide range of plugs (sure it's anecdotal but I doubt he has such different plugs from other people in the US). Apparently the plugs that actually do have the bumps don't fit in a way that is safe (either they fit accidentally and/or fit too far forward, meaning the plug, with the holes engaged, is partially exposed). The reason plugs don't slip out is because of friction, not because of the holes.
My suspicion was the third one, and I suspect that was the original reason manufacturers did it. It's likely done now because of the machines that make plugs expecting those holes.
My suspicion was the third one, and I suspect that was the original reason manufacturers did it. It's likely done now because of the machines that make plugs expecting those holes.
I have a number of locking cord ends (outlets) for extension cords that do use the holes to retain the male plug via ball detents. They require you to push a button to release the plug.
https://www.homedepot.com/p/15-Amp-Stay-Plugged-Cord-Replace...
I've never seen anything else similar.
I'm curious on the design of "hospital grade" plugs as that wasn't in his survey and I know that they are designed for higher retention force than commercial or residential applications.
https://www.homedepot.com/p/15-Amp-Stay-Plugged-Cord-Replace...
I've never seen anything else similar.
I'm curious on the design of "hospital grade" plugs as that wasn't in his survey and I know that they are designed for higher retention force than commercial or residential applications.
None of the above.
#1 is ruled out as he takes apart a number of plug receptacles, from “cheap” to “heavy duty” and “commercial grade”, none of them sport the bumps you’re describing. He also points out that not all plugs have holes (using an ikea timer as an example), and observes that most plug-in receptacles don’t offer the kind of resistance one might expect if such bumps existed.
#2 and #3 are closer to the mark.
Apparently the holes are optional according to a standards body called NEMA (https://archive.org/details/NEMA-WD-6-2016/page/n24/mode/1up) and are generally intended for use in the manufacturing process.
“Hole in flat blade is optional, and is intended for manufacturing purposes only.”
See 13:30 in the video for an example.
#1 is ruled out as he takes apart a number of plug receptacles, from “cheap” to “heavy duty” and “commercial grade”, none of them sport the bumps you’re describing. He also points out that not all plugs have holes (using an ikea timer as an example), and observes that most plug-in receptacles don’t offer the kind of resistance one might expect if such bumps existed.
#2 and #3 are closer to the mark.
Apparently the holes are optional according to a standards body called NEMA (https://archive.org/details/NEMA-WD-6-2016/page/n24/mode/1up) and are generally intended for use in the manufacturing process.
“Hole in flat blade is optional, and is intended for manufacturing purposes only.”
See 13:30 in the video for an example.
page 4 already so this comment is wasted.
But, this is the third time in as many months that a youtube video suggested to me has appeared on HN. It's clear that my interests (and YT suggestion algorithm) aligns with that of many HN readers.
It's _more_ interesting that HN is, in very small doses, infiltrated by megacorp algorithms. Promoted content subsuming independent discovery. Of course, 'subsuming' is too strong a word, so don't take it literally.
But, this is the third time in as many months that a youtube video suggested to me has appeared on HN. It's clear that my interests (and YT suggestion algorithm) aligns with that of many HN readers.
It's _more_ interesting that HN is, in very small doses, infiltrated by megacorp algorithms. Promoted content subsuming independent discovery. Of course, 'subsuming' is too strong a word, so don't take it literally.
So you can stick a pair of bare wires through them, of course.
The holes exist to provide an edge capable of scraping off oxides on the contact, thus providing a (more) reliable low resistance connection.
That’s not what the video says. It says (and quotes the relevant standard) that they’re optional, and used for manufacturing purposes.
Yes, this video is the undeniable truth. Anything this tuber doesn't know isn't real.
The video isn't, but the standard is.
The standard states they are optional, but provides no logic as to why a manufacturer would go to the trouble of punching these holes at great expense that are apparently unnecessary.
Look around at your high power appliances, exactly all of them will have holes in the prongs. There must be a reason don't you think?
Look around at your high power appliances, exactly all of them will have holes in the prongs. There must be a reason don't you think?
Just in case you missed it - high resistance connections particularly harm high power applications where the total power loss at the connection is proportional to the resistance multiplied by the current squared.
When you are operating near the threshold for the maximum allowable current draw on a single circuit (nominally 15A in USA), this additional power loss can make your device or product fail certification.
This feature is called self cleaning contacts. It is a well known technique in the connector world. Which this tuber is not a part of.
When you are operating near the threshold for the maximum allowable current draw on a single circuit (nominally 15A in USA), this additional power loss can make your device or product fail certification.
This feature is called self cleaning contacts. It is a well known technique in the connector world. Which this tuber is not a part of.
The video contains a video showing exactly how the holes are used in manufacturing.
You seem to dislike people who create content on YouTube but this video seems well sourced.
You seem to dislike people who create content on YouTube but this video seems well sourced.
You are missing the point - people can make content on youtube all they want, but that doesn't make it correct.
2. Electrical devices can be "factory-sealed" or "locked-out" by the manufacturer or owner using a plastic tie or a small padlock that runs through one or both of the prong holes. Construction projects or industrial safety requirements may require this type of sealing. For example, a manufacturer might apply a plastic band through the hole and attach it to a tag that says, "You must do blah blah blah before plugging in this device." The user cannot plug in the device without removing the tag, so the user is sure to see the instructions.
3. There also is a small savings in raw materials (metal) for the manufacturer of the actual plug prong. Every little bit helps!
It has been reported that really old outlets used captive ball bearings and coil springs for the detent, but today it is done with a bump and springy copper contacts.
https://home.howstuffworks.com/two-flat-prong-plug-holes.htm