Polarized plugs on power tools - Woodworking Talk - Woodworkers Forum
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post #1 of 19 Old 06-10-2019, 10:36 AM Thread Starter
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Polarized plugs on power tools

Disclaimer: I promise to not sue you if you offer information that does not conform with the current OSHA standards and I electrocute myself. I just want some facts. What I do with that is on me. I'm a strong proponent of personal responsibility.


Several of my newer tools have polarized two-prong plugs. Is this necessary? When researching this, the common scenario I found is someone unscrewing a light bulb and touching the metal threaded part which is now hot. Ok, I can see that, but with power tools, no part of the circuit (AFAIK) is exposed that can be touched.


My brother is a professional carpenter and grinds the keys off all his tools, but he tends to play fast and loose with safety and isn't the best resource for information on this.
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post #2 of 19 Old 06-10-2019, 11:56 AM
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Its like this... the manufacturer tries his damdest to make the tool as cheap as he possibly can. The only reason he will make something "special" is if he knows he will get his ass sued off if he doesnt.

That means if you alter what the manufacturer does, its your ass on the line, not his.
And any ensuing insurance claim lands squarely at your door, not his.
So tell me, do you feel lucky?
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post #3 of 19 Old 06-10-2019, 12:09 PM
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Quote:
Originally Posted by enchant View Post
Disclaimer: I promise to not sue you if you offer information that does not conform with the current OSHA standards and I electrocute myself. I just want some facts. What I do with that is on me. I'm a strong proponent of personal responsibility.


Several of my newer tools have polarized two-prong plugs. Is this necessary? When researching this, the common scenario I found is someone unscrewing a light bulb and touching the metal threaded part which is now hot. Ok, I can see that, but with power tools, no part of the circuit (AFAIK) is exposed that can be touched.


My brother is a professional carpenter and grinds the keys off all his tools, but he tends to play fast and loose with safety and isn't the best resource for information on this.
It's difficult to answer your question. If the tool has any kind of electronics in it then polarization is very important. For the most part the folks that designed the tool has double insulated it and arranged the wiring so the polarized plug if used correctly should be as safe as a grounded plug. It's really only the safety aspect of it. The tool itself could care less if it's polarized or not. Power tools weren't always grounded or even polarized. Back when these tools were like that they also had metal bodies on them so if anything went wrong internally you got a quick lesson if you touched a water pipe while holding one of them.

Your brother by grinding the keys off is making himself a lot more vulnerable to electric shock.
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post #4 of 19 Old 06-10-2019, 01:49 PM
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Ok, I can see that, but with power tools, no part of the circuit (AFAIK) is exposed that can be touched..
You forgot the most important part of that statement, under normal use cases. Problem is the abnormal ones, and its worth a reminder that nobody gets electrocuted under 'normal' cases.

Strictly speaking, ac circuits don't care which leg is hot, except for when they do. Flipping polarity could lead to a power switch now switching the neutral leg off instead of the hot leg, for example.
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post #5 of 19 Old 06-10-2019, 02:31 PM
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"Several of my newer tools have polarized two-prong plugs. Is this necessary?" I wonder just why you are asking this question. ??? Would you like to change out the plugs?



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post #6 of 19 Old 06-10-2019, 03:51 PM
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I depise them!

If there's one thing I can't stand about using any tool with a "polarized" plug, it's using a tool with a polarized plug. No matter which way you grab the plug and attempt to insert in into the cord or recepticle, it won't oriented correctly!


Why didn't the brainiac engineers make one prong at 90 degrees to the other or one round one or one distinctly longer or shorter than the other ......
I think I know.... it's because ALL the recepticles would need to conform.

and that's too expensive.

The answer to your question will only be as detailed and specific as the question is detailed and specific. Good questions also include a sketch or a photo that illustrates your issue. (:< D)

Last edited by woodnthings; 06-10-2019 at 03:55 PM.
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post #7 of 19 Old 06-10-2019, 04:02 PM
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Originally Posted by woodnthings View Post
If there's one thing I can't stand about using any tool with a "polarized" plug, it's using a tool with a polarized plug. No matter which way you grab the plug and attempt to insert in into the cord or recepticle, it won't oriented correctly!


Why didn't the brainiac engineers make one prong at 90 degrees to the other or one round one or one distinctly longer or shorter than the other ......
I think I know.... it's because ALL the recepticles would need to conform.

and that's too expensive.
We did,
https://www.ebay.co.uk/itm/UK-13A-BL...-/142269298678

but you americans went your own way (again)
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post #8 of 19 Old 06-10-2019, 04:38 PM
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Originally Posted by woodnthings View Post
If there's one thing I can't stand about using any tool with a "polarized" plug, it's using a tool with a polarized plug. No matter which way you grab the plug and attempt to insert in into the cord or recepticle, it won't oriented correctly!


Why didn't the brainiac engineers make one prong at 90 degrees to the other or one round one or one distinctly longer or shorter than the other ......
I think I know.... it's because ALL the recepticles would need to conform.

and that's too expensive.
I thought it was just me. You would think you would have a 50-50 chance of having the plug oriented right but I have it wrong nearly every time. I hate them too and have considered grinding the keys off too.
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post #9 of 19 Old 06-10-2019, 05:08 PM
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I find them a minor irritant compared to USB 2 plugs, at least they are big enough so the orientation is obvious if you stop to look.
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post #10 of 19 Old 06-10-2019, 05:38 PM
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That's a 3 prong you linked .....

Quote:
Originally Posted by sunnybob View Post
We did,
https://www.ebay.co.uk/itm/UK-13A-BL...-/142269298678

but you americans went your own way (again)



Don't blame me, pal.

At least with a 3 prong you will be able to see the long round pin and get it right. The 2 prongs are almost identical in width so it's more difficult.
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post #11 of 19 Old 06-11-2019, 12:03 AM
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It's simple.

Lower Left Large

When the grounding lug is in the lower position the large prong is in the left position.

The large lug is AC neutral. (Oh Lord I hate that term.) Which is really ground. We'll get to that.

Back when Craftsman made quality power hand tools, 50 or so years ago, they invented "Double Insulated". Double Insulated was a term to convince the ignorant to buy their new line of power tools rather than the three wire grounded models of the competitors. The third wire, green wire or ground wire is really, electrically, AC Neutral. If you look inside your circuit breaker panel closest to the service entrance, you will find the white wires connected to a bus bar and the AC Neutral from the power company. A big surprise is that the green wires are connected to a similar bus bar that is also connected to the AC Neutral bus bar and a ground rod driven into the ground.

The ground wire is connected to the chassis of the device. The purpose of this additional grounding is to prevent injury if the device fails and the chassis becomes electrified.

Some years ago I heard of a guy in a body shop wet sanding a vehicle. The guy dropped dead while working. He was standing in water and the sander had the grounding lug cut off the plug. The bearing in the sander had long needed to be replaced and armature swiveled enough to come in contact with the metal shell. So the safety ground removed, the user standing in water and the sander energizes the shell or case of the sander. The path to ground is now through the user to the wet floor. Goodbye user.

One caveat however. If you have sub circuit breaker panels, DO NOT connect the AC Neutral and Ground Bus bars in that panel. DO NOT connect a ground rod to the ground bus in the sub circuit breaker panel. If you do you will have problems with any analog (cable TV) device in your home. (Pixilation problems mostly) It is called a ground loop and you don't want to go there.

Should you "Skinny up the prongs of the plug"? NO! But it doesn't really matter with today's modern tools. Yes, you could be switching the neutral side of the circuit rather than the hot but with today's modern tools it doesn't matter unless you are taking the tool apart whilst plugged in.

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Last edited by NoThankyou; 06-11-2019 at 12:12 AM.
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post #12 of 19 Old 06-11-2019, 05:35 AM Thread Starter
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If the tool has any kind of electronics in it then polarization is very important.

This is news to me. When did this start? I had plenty of complex electronic gear that was manufactured without keyed plugs. How are they surviving?

Quote:
Originally Posted by woodnthings View Post
Why didn't the brainiac engineers make one prong at 90 degrees to the other or one round one or one distinctly longer or shorter than the other ......
I think I know.... it's because ALL the recepticles would need to conform.

and that's too expensive.

I'd be happy if they'd do something like make the top a specific color like white so you'd know which way to plug it in.


Quote:
Some years ago I heard of a guy in a body shop wet sanding a vehicle. The guy dropped dead while working. He was standing in water and the sander had the grounding lug cut off the plug.
I am NOT talking about 3-prong plugs. If all of my 2-prong keyed plugs were 3-prong, that would solve the problem.


Quote:
Should you "Skinny up the prongs of the plug"? NO! But it doesn't really matter with today's modern tools.
Ok, I'm a little confused here. If it doesn't really matter, why should I NOT do it?
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post #13 of 19 Old 06-11-2019, 08:44 AM
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If the tool has any kind of electronics in it then polarization is very important.

Oh, it gets better: My son has a PS2. If it loses power without going through the power-off sequence (e.g. if you unplug it or there's a power outage), it could be damaged beyond repair.
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post #14 of 19 Old 06-11-2019, 05:18 PM
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I thought it was just me. You would think you would have a 50-50 chance of having the plug oriented right but I have it wrong nearly every time. I hate them too and have considered grinding the keys off too.



Kind of like wiring up a 3 ph motor 50-50 chance of it running the right way but 95% of the time it runs backwards

There is no app for experience
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post #15 of 19 Old 06-11-2019, 06:17 PM
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Ok, I'm a little confused here. If it doesn't really matter, why should I NOT do it?
It is the "regulations" like OSHA, NEC and local. "It doesn't matter but the code says. . . . "

In a commercial setting it could easily be called revenue.

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post #16 of 19 Old 06-11-2019, 07:47 PM
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This is news to me. When did this start? I had plenty of complex electronic gear that was manufactured without keyed plugs. How are they surviving?




I'd be happy if they'd do something like make the top a specific color like white so you'd know which way to plug it in.



I am NOT talking about 3-prong plugs. If all of my 2-prong keyed plugs were 3-prong, that would solve the problem.



Ok, I'm a little confused here. If it doesn't really matter, why should I NOT do it?
Without knowing the specific schematics of a particular tool you have to assume there is electronic components that is polarized sensitive. It's better to be safe than sorry and keep the wiring polarized.

The way a tool is wired internally the hot wire is really kept isolated to prevent someone from being electrocuted. If you reverse the polarity there is a greater chance the neutral wire might come in contact with something you can end up touching. Both the hot wire and neutral wires are considered current carrying lines but the neutral is much less chance of getting hurt. With modern tools where the body is usually plastic there is a lesser chance of having that happen but the potential is there.
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post #17 of 19 Old 06-11-2019, 09:12 PM
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It takes a couple seconds to stop and look at the prongs or turn the plug over if you didn't, is saving that time worth the risk of eliminating the measure of safety it provides?
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post #18 of 19 Old 06-14-2019, 01:03 AM
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The fact is that people have been shocked, injured, and even killed by power tools and other things that use line power. This does not happen with a new item that is in proper working condition; no defects. But things do not stay perfect forever. I have seen power tools that have underwent sever abuse and people were still trying to use them. That's human nature.

So the safety guys have come up with the idea that more than one thing should have to go wrong before someone can be hurt by them. I guess the hope is that by the time that there are two or more safety related problems, the tool will have stopped working and the user will have replaced it or had it PROPERLY repaired.

The first way that was done, with tools that had metal cases was to first have the line Voltage insulated from that case and second to have the ground wire that would trip the circuit breaker if that insulation failed. So, in order to get a shock both the insulation and the ground wire would have to fail.

Adapters that had a green lug that would convert a two prong outlet to a three prong one were made available but that green lug had to be SCREWED down with the screw that held the outlet's cover in place. That provided the ground connection and the safety that it provided. Of, course no one ever did that (myself included) but it got you by the code and the safety guys.

Then tools became lighter by using plastic cases, which were non conductive. That removed one of the two things that had to go bad in order for someone to be hurt. There were still metal parts, many of which were accessible from outside of that plastic case so you could get a shock if one of them became energized by an internal failure. And it was not always ECONOMICALLY possible to connect all of them to that ground wire. Besides, the ground wire cost money - look up the price of copper. So the engineers found another way to ensure the idea of TWO failures before harm could come to the user. Yes, there was the original insulation on all the wires and other components that the current flowed through. But the outer, plastic shell was designed so that there were no metal, conductive parts that were in contact with any of the internal metal parts. Now both the original insulation AND the outer protective, insulative shell must both fail before the user can be shocked.

The math of this works through multiplication. If the original tool had a one in a thousand (0.001) chance of harming the user and the second protection method had that same level of protection, then when they are combined those two figures are multiplied to get one in a million (0.001 x 0.001 = 0.000001).

By grinding the key off his tools, I assume you mean that your brother removes the ground terminal from the plugs of the three wire tools. He is removing ONE of the two things that must fail. He has vastly increased his chances of injury as most tools will suffer some kind of failure in their life. This is not a wise thing to do. But again, many have done this. I definitely do not recommend it.

Or perhaps he is making the wider of the two prongs a bit narrower so it will fit either way. Electric devices are designed with a definite idea of which wire is hot and which one is the neutral and therefore not hot. If the device has a fuse or a switch, it will be in the hot leg, not the neutral one. If it has stray current protection, like a GFI outlet, it will disconnect the leg that is the designated hot one. There would be little protection gained from disconnecting the neutral side as the leakage current would still remain. Other protection schemes may exist within a tool. Neither you, he, nor I may know the exact way in which this protection functions, but by allowing the two wires to be reversed and possibly removing it he has made things more dangerous. Again this is not a good idea and I definitely do not recommend it.

Many thousands of deaths have been prevented by this, double failure/double protection idea, dare I say tens or even hundreds of thousands. It is an idea that actually works, that actually saves lives and injury.



Quote:
Originally Posted by enchant View Post
...<snip>...

Several of my newer tools have polarized two-prong plugs. Is this necessary? When researching this, the common scenario I found is someone unscrewing a light bulb and touching the metal threaded part which is now hot. Ok, I can see that, but with power tools, no part of the circuit (AFAIK) is exposed that can be touched.

My brother is a professional carpenter and grinds the keys off all his tools, but he tends to play fast and loose with safety and isn't the best resource for information on this.

Last edited by EPAIII; 06-14-2019 at 01:09 AM.
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post #19 of 19 Old 06-14-2019, 01:01 PM
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If you trace the wiring in a polarized plug tool you will find that the small blade of the plug is the wire that goes through the power switch. With it this way the power is removed from the tool when the trigger/switch is off. This provides a slightly higher level of safety in those certain odd situations. A non polarized plug could have the hot wire going to the tool without going through the switch, and in this case if let's say a nail somehow went into the drill through a vent hole and broke the insulated coating on a wire, the nail could become powered even with the trigger/switch in the off position. A regular table lamp with a non polarized plug could have the hot wire going to the outer screw thread of the lamp socket and not through the power switch, so it would be easier to get a shock when changing the light bulb. With a polarized plug, the hot wire would go through the switch and to the center pin of the light socket, so it would be safer when changing the light bulb. I prefer the polarized plug system to keep the power switch in the hot side of the circuit, even if the plug is a three prong that includes the ground pin.

BTW, Neutral and ground are connected together at the main electric panel, but don't think that because of this that the neutral wire can't give you a shock if touched some considerable distance from that power panel. Current flowing in the neutral wiring and the electrical resistance of that wiring can result in considerable voltage differences between neutral and ground that could be significant enough to give you a very bad shock. Don't ever think that the neutral wire has no voltage on it.

I'm a retired electrical engineer and licensed electrician.

Charley
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