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.

WB
..............

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.

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

"Wild Bill" wrote in message
oups.com...
snip-----

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)

I found just such a problem in a 1/2 horse motor I use for my tool bit
grinder. It ran fine, but showed voltage from the housing to ground.
Grounding the housing eliminated the problem, but when I dismantled the
motor to replace bearings, I found the source a wire that had been crushed
between two members. Insulation was intact, but there was a high resistance
leak. Taped the crushed portion and the problem went away.

Harold







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.

WB
.............

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.

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

On Wed, 22 Feb 2006 21:13:39 -0800, "Harold and Susan Vordos"
wrote:


"Wild Bill" wrote in message
roups.com...
snip-----

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)

I found just such a problem in a 1/2 horse motor I use for my tool bit
grinder. It ran fine, but showed voltage from the housing to ground.
Grounding the housing eliminated the problem, but when I dismantled the
motor to replace bearings, I found the source a wire that had been crushed
between two members. Insulation was intact, but there was a high resistance
leak. Taped the crushed portion and the problem went away.

Harold



snip

Harold, I had one like that last year, only it was the power wiring to
a 460 V. 15 Hp. motor crushed in the motor junction box cover.
Luckily, the AB Powerflex 700 VFD was smart enough to instantly trip,
so no light show. This was on a new installation.

Pete Keillor