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:
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