On Sat, 3 May 2014, Trevor Wilson wrote:

On 3/05/2014 12:01 PM, Phil Allison wrote:
"amdx"
could have saved my life.

I was in my workshed which is about 60 ft from the house drilling some
aluminum. I got a faint tingle in my hand, I touched the case of my
drill a couple times and didn't feel any thing, so I started to drill
again. I noticed the tingle again, I went through this a few times until I
decided there's a problem. The tingle was at a tiny red spot on my finger,
I later removed a small metalic sliver. If not for the sliver I probably
would not have noticed the missing ground, for I don't know how long.
The drill motor is a 3 wire system, hot, neutral and ground. I had it
plugged into a GFCI. I unplugged the drill and pushed the test button.
The GFCI didn't pop. I retrieved my DVM and tested from the drill case the
the dirt outside the door, it was about 80v. I then tested from the Hot to
the ground at the receptacle, that was about 20 v. I moved to another
Receptacle closer to the house, same thing no ground connection. I moved
up to a receptacle on the outside of the house on the same line, again no
ground connection. Inside the garage, no ground connection. I opened the
circuit breaker box and checked the ground wire, it is good.
So, in my attic between the CB box and the garage there must be a
connection box where the ground has opened up.
Followup tomorrow evening.

** FYI:

GFCIs work independently of the safety ground in a 3 wire system - so will
still trip if a few mA of current is passing to any local ground like soil,
wet concrete or metal plumbing.

However, a missing safety earth conductor is never good as the metal cases
of 3 wire appliances can become live and nothing blows.

BTW:

I have not seen a 3 wire, hand held drill in quite a while.

**You got that right. My old man gave me my first electric drill (an Hitachi,
which I still use) back in 1967. It was a double insulated type. He gave me
my second electric drill (a variable speed Bosch in 1974 - which simply
refuses to stop working). Also double insulated. He kept using his aluminium
cased Black & Decker for some reason. I have not seen an earthed portable
electric drill since at least that time, though the old man's B&D is still in
the family garage. It hasn't been used in more than 20 years. Nor should it
be. Terrifying things. Moreso for those of us in 220-240VAC countries.

That's odd. My Black & Decker from 1975 (variable speed, but only one
direction) has a three prong plug, still works fine, though about 25 years
ago I had to put in replacement brushes.

In about the past five years, I bought another B&D drill at a garage sale
for a few dollars, that one maybe has two prongs, but the B&D drill that I
found in the garbage when the students moved out (which does reverse) is
three pronged.

Even that fancy detail sander I found last year, only to realize when I
got it home that it was a 220V unit, that has three prongs, of the
non-North American kind.

Of course, now one has the option of getting a cordless drill, which is
certainly a whole lot safer, and beats getting out an extension cord or
two to bring power to that distant location that requires a drill. I
don't use mine that much, but the first time I had to drill a hole and
didn't have to lay out the extension cord paid for that cheap cordless
drill.

Michael