Drill leaks electricity to case

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I have this Black and Decker 450 RPM drill:
http://igor.chudov.com/tmp/450-rpm-drill.jpg
When plugged into a GFCI outlet, it leaks electricity to ground and pops the GFCI breaker. The leak is substantial, I believe, however when plugged into a regular breaker (and handled with caution appropriate for leaks to case), it actually works and does not blow the breaker. So, I think, the leak is limited in extent.
My question is, what is the most likely culprit and how to approach repair of it.
My another question is, what would be a typical application of this drill. I am trying to decide if I need it for anything.
i
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You need to fix that leak. There's only so much electricity in those drills, and if it all leaks out, it won't run any more.
LLoyd
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That's really a common misconception. Electronics, and anything else electrical actually work on smoke. We know this to be true, cause once you let all the smoke out, they stop working.
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I agree! I can't think of even one time when the smoke got out that the tool in question still worked.
Harold
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Ignoramus3408 wrote:

Let's just say I would not want to be handling that drill nor would I allow an employee or family member to handle it. It is time to have it repaired or replaced.

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Joseph Meehan

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wrote:

I gotta agree with that!
So... any idea of how to approach repairing it? I suspect that something very simple is wrong, like related to brushes or some such.
i

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Ignoramus3408 wrote:

First, get an Ohmmeter and see if you can detect continuity from the case (or ground prong) to either of the flat plug terminals. If so, then you want to work on the drill until the ohmmeter reads infinity to the same terminal. Open up the drill, and inspect the brush holders for greasy black deposits. Cleant that off, and clean around the commutator (carefully) for similar gunk. Check the plug for conductance again. If that fixed it, you got off easy. If not, check the cord, switch/speed control and anywhere else in the drill where wires run for bare contacts and something like dirt, chips, greasy goo that could conduct electricity. If there is nothing more to be found, then you either have a short in the armature or field windings. You can disconnect things to isolate the faulty part, but other than getting a replacement part from B&D, it is not easy to fix, unless you want to learn the intricate art of motor rewinding.
Jon
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Thanks Jon. It is either a quick fix or toss to garbage. I suspect that the cause is crud accumulated in various places.
i
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Ignoramus15109 wrote:

Very possible.
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Joseph Meehan

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"Ignoramus15109" wrote:

There should be a law forbiding people from throwing away old metal-bodied power tools.
Jon
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On Wed, 22 Feb 2006 12:04:35 -0800, Jon Danniken

OK, if I cannot fix it, I will let you know, maybe you can pick it up and do whatever you want with it. I think that you live nearby, IIRC.
i
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"Ignoramus15109" wrote:

metal-bodied
Thanks for the thought Iggy, but I live in Oregon.
Jon
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On Wed, 22 Feb 2006 14:31:39 GMT, Ignoramus3408

First step is to dissassemble and clean the drill - and with a good ohm-meter check for shorts to ground from the field winding (quite common) or the brush holders. It is POSSIBLE the brush holders are just dirty - conductive brush dust etc on the surface. *** Free account sponsored by SecureIX.com *** *** Encrypt your Internet usage with a free VPN account from http://www.SecureIX.com ***
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wrote: | > Ignoramus3408 wrote: | >>I have this Black and Decker 450 RPM drill: | >> | >>
http://igor.chudov.com/tmp/450-rpm-drill.jpg
| >> | >> When plugged into a GFCI outlet, it leaks electricity to ground and | >> pops the GFCI breaker. The leak is substantial, I believe, however | >> when plugged into a regular breaker (and handled with caution | >> appropriate for leaks to case), it actually works and does not blow | >> the breaker. So, I think, the leak is limited in extent. | > | > Let's just say I would not want to be handling that drill nor would I | > allow an employee or family member to handle it. It is time to have it | > repaired or replaced. | | I gotta agree with that! | | So... any idea of how to approach repairing it? I suspect that | something very simple is wrong, like related to brushes or some such.
If you can see into the drill and there's gobs of carbon all over the inside of the case from the brushes, rinse it all out with brake cleaner and replace the brushes. You might be able to make the GFCI quit tripping if you just were to rinse it out; might be worth a shot.
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depending on how long you've been married, you might want to let you wife try it.
Ignoramus3408 wrote:

Let's just say I would not want to be handling that drill nor would I allow an employee or family member to handle it. It is time to have it repaired or replaced.

--
Joseph Meehan

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Ignoramus3408 wrote:

To trip a regular breaker, it'd have to be "leaking" 15Amps worth of electricity.
If you're leaking 15Amps worth of electricity, then the stuff it's leaking into is being cooked with a couple thousand watts (think several horsepower worth of power).
GFCI's trip at the few milliamp level (I forget the official number).
Currents as small as 100 microamps can cause heart fibrilation. Although typically only a fraction of the current flowing through your hands or feet will go to your heart (I've read a couple of medical papers where they take fresh cadavers and run electricity through them sideways, upways, downways, etc, measuring heart current so there must be some interest in this number.)

Looking at the picture, grunge grease or dirt in the plug, cable, or drill body or motor can be enough to trip the GFCI. Looks like somebody already changed the plug, check it out and make sure they don't cross-connect neutral with ground (this is guaranteed to trip a GFCI, unless you've got an open ground connection... the myriad problems with multiple failure diagnosis!)

I hear that California has been having some technical problems with their method of execution :-).
Timi
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Exactly.

Yep.
Exactly my own thinking. It is leaking a little bit, there is no "short to ground", there is some high resistance path for electricity to leak.

I like this. I will take the drill apart.
A question: can it be related to brushes in some way?
i
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Ignoramus3408 wrote:

Truly excessive dirt/dust/grunge on the brushes could do this, but if it were that bad then probably the drill wouldn't run. On very heavily used and abused motors you can find metallic dust from the brushes etc. distributed over everything and this can certainly cause leakage. That drill looks used enough that it could fall in this category.
Do check where the brushes attach for grunge as well as the insulators, and also look over the motor windings.
Does it trip the breaker even when the drill isn't on? If so, look on everything on the upstream side of the switch all the way to the plug (including the switch.)
Does it only trip the breaker with the drill is on? Then you should be looking at the windings and grunge that would cause leakage from the brushes to the body.
Tim.
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Yes. I think that I will take it apart and blow with a compressor. (outdoors, wearing eye protection etc)

Will do.

Absolutely not.

Yes. I have some vague recollections about suspecting the switch in this case.

Will do. I will report my findings.
Thanks Tim.
i
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These old drills with low speeds are really nice for drilling large holes. I have a slightly newer B&D (60's?)that runs at 200 rpm. Perfect for 1/2" holes in 3/4" bar stock (or as perfect as ANY hand drill is for that miserable job!) That one got a new cord strain relief last fall.
You can do a quick check on the GFI issue by run an ohmmeter on the plug: Either of the two blades to the ground pin should be up in the 100k range or better. If not, chase it down. If it consistently blows a GFI, it probably reads in the low 000's ohms.
As for repair, this one looks like it needs a full teardown, inspect, clean, repair as necessary. My guess would be the plug, the switch, or the brushes. The grease in the gearbox will be grey slime. Check the brushes to make sure they still have wear length to them. Check the wiring, looking for thin spots in the insulation.
I bought a similar one a while back for $2. It wound up as scrap metal, saved the chuck. Some you win, some not.
Ignoramus3408 wrote:

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