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.
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.
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 :-).
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.
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.
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 > I have this Black and Decker 450 RPM drill:
They're also wonderful for large diameter/long wood bits (eg: drilling for 3/4" hardware thru fence posts), driving lag screws, large hole saws (esp. thru steel), and sometimes large carbide bits thru masonry.
I have a similar vintage one. I don't use it often, but there are things it does that none of my others can. Yours is similar to more standard 1/4" and 3/8" drills, with a D-shaped push handle. Mine is somewhat beefier - the D handle is rotated 90 degrees, and there's yet a third handle that can either be attached opposite the handle with the trigger (like a jackhammer) or come out the side (like a bolt action on the side of a rifle).
Put the ohmmeter on the plug in various combinations (_not_ plugged into the wall) and pull the trigger. If you see conductivity, it's probably a dirt/wiring problem on the motor side of the switch. If you don't, it's probably something to do with the motor windings - eg: a worn spot that peridiodically contacts some rust or grit on the armature or something like that.
A very thorough cleaning will likely solve it. If the windings are shot, it's not worth repairing. Cannibalize it - looks like a good chuck.
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.
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.
That's a nice rugged drill, to replace it with an equivalent new model of the same durability would be expensive.
As has been recommended, a thorough cleaning may completely solve the current leakage problem. Conductive dust (from the brushes or other external sources) can create a leakage path for 120VAC. After normal cleaning, a flush with an appropriate solvent should remove all traces of any conductive contamination.
An ohm meter may not indicate the leakage path, since the applied voltage from the meter is much lower than the breakdown path voltage. The most commonly known tester for insulation breakdown is the Megger.. it applies a high voltage to various components to allow the user to locate the insulation leakage, by indicating the leakage reading in megohms, or mA, or uA. There are many other ways to perform the same tests with other equipment. Leakage testing on live equipment should only be done when the equipment being tested is powered thru an islolation transformer.
The actual fault could be something as simple as a pinched, but not shorted, wire (lowering the voltage breakdown level of the wire's insulation) or oily dust accumulation on the field or armature windings, or around the normally-isolated brush holders previously discussed. Moist dirt is more conductive than dry dirt (sawdust, for example).
As you already know, the fault is a high resistance path to the metal case. It would be wise to make certain that the ground lead is undamaged, and securely attached to the drill case, and at the plug end.
GFCI protectors basically react to an imbalance between the line and neutral conductors, and will protect the user even when the appliance cord is only a 2-wire cord (hair dryers, for example). Most appliances with metal housings definitely need to have a 3rd lead to be earth grounded. In other metal-cased appliances, the design and insulation meet requirements for safe operation, but the insulative characteristics can be compromised by infiltration of contaminants, abuse or damage. Maybe the most common contaminant would be water or moisture. Even very humid air can cause insulation leakage, excessively in high voltage circuits.
HomeOwnersHub website is not affiliated with any of the manufacturers or service providers discussed here.
All logos and trade names are the property of their respective owners.