Basically, Double insulated is a little misleading, but
in UL/CSA parlance, it means that the internal wiring
is such that it would take TWO faults to occur, either
of which would stop the product from working, before
anything could become electrically dangerous to the
user. Usage conditions are also taken into account.
Among other things it also means that there cannot
be any exposed metal on the product. ALL exposed metal
must be grounded, which become a non-essential in
double insulated products.
It also means it doesn't need a third "prong", and the
blades do not have to be polarized on the two-blade
plug, and it does not need a 3-hole outlet.
Not entirely true. The classic example is a double-insulated inexpensive
power drill. The chuck that holds the bit is metal, and is not grounded.
The tool does not have a third prong grounding conductor. But it meets the
definition of double-insulated because the chuck is insulated from the motor
by nylon gear-drive. And the windings on the motor are, of course,
insulated from the motor frame. So it would take two faults, just as you
said. It has no third prong, also as you said. But the exposed metal parts
are *not* necessarily grounded.
So they put in nylon gears, which we all know have a very limited life
span, instead of using reliable gears and adding a grounded cord.
That's just plain stupidity at it's worse. Also the reason I am
always looking for the old solid metal drills at garage sales. Not to
mention that most new drills have those keyless chucks, and I
absolutely despise those useless pieces of shit.
I'd much rather spend the extra dollar or two for the steel gears and
I bought a portable jig saw (saber saw) 2 years ago. It had plastic
or nylon gears. I used it maybe 2 hours at most cutting plywood and
such. Then I inserted a metal cutting blade and started to cut a
piece of steel barn siding. I was cutting the length of the steel or
about 8 feet. That stuff is only 22 gauge or thereabouts. I cut
about 2 feet when the saw stopped cutting, but the motor was still
running. I opened the saw to find the nylon gears completely
stripped. After a big hassle, I was able to get the thing replaced
thru the warranty, but as far as I am concerned, it's pretty much a
useless tool, since I know as soon as I use it for anything more than
cutting some balsa wood, the new one will strip too. Just more
inferior crap sold by Black & Decker.
Nylon gears can last for decades of use when not abused. Jigsaws are not the
best choice for cutting 22 gauge steel. Tin snips or nibblers are a much
better choices. For a saw blade to work most efficiently, the material must
be significantly thicker than the pitch of the blade. When cutting thicker
material the teeth lower on the blade hold the saw away from the material
being cut. Without these lower teeth in contact, every time a tooth of your
saw hit caught on the bottom of the sheet-metal, it sent a major shock
straight up the transmission.
Maybe you have to buy the stuff not in the bargain bin. I like my old Black
and Decker drill, but if I ever start doing serious work, I would buy a new
one that is lighter more efficient and more powerful.
Double insulated means they wrapped TWO layers of electrical tape
around all bare wires, not just one. That also means the item cost $5
more than if they has only wrapped the wires once.
As to the OP, you mean you still didn't fix that lamp. You posted
about it about 2 or 3 months ago. Apparently you have not used the
lamp or we would have heard about your funeral by now.
It always amazes me that people will risk their life for a lousy
dollars worth of wire and 20 minutes of time, and probably spent an
hour posting a message about it.
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