ECN Forum Forums Photo Discussion Forums Electrical Nostalgia 1957 Power Tools

I wonder how many people actually bothered connecting the earth lead on the 2 to 3 pin adaptors supplied with these. In 1957 I imagine there would be a good proportion of 2 pin sockets in use. Of course if the 2 - 3 pin adaptor is lost, one reaches for the pliers, and miraculously the plug now fits.
Hands wrapped tightly around metal cased power tools gives me the creeps.
Does double insulated construction apply in the U.S these days? While obviously modern power tools sold in the U.S are plastic cased like the rest of the world, do they have the 'square within a square' symbol on them to indicate this, or is it only in the 220-240V countries?

I have a Sears Craftsman drill which I purchased about 15 years ago (well past the point when three-wire cords were common). This drill has a two-wire cord, and the drill states that it is "double insulated". I have yet to really understand this concept. Can anyone explain what is double insulated...the cord, the internals of the drill itself...?

Mike (mamills)

The Skill model 6355 I just saw on a lab bench does have the double insulated (class II) symbol.

I don't like the idea of metal cased cordless tools where the bit or blade could have continuity to the metal case. I am not certain the following is of this construction, as the company did not answer the question I submitted online (which was over yr ago I think - I took no answer as the answer you wouldn't want to hear):

http://www.amazon.com/Black-Decker-RD1440K-Anniversary-Cordless/dp/B00006FX9U

I can not think of a product safety (compliance) reason why a product could not have double insulation from primary parts to the enclosure, and also have a grounded metal enclosure. Though I'd think your odds of being saved from the (hopefully) rare event of a double insulation fault to the chassis might be outweighed by the odds of you getting shocked from ground potential rise.

Basically, anything and everything which could result in a short causing a metal casing to become energized. For example, where the wiring connects to the motor terminals a broken conductor moving around enough could contact the case. So the whole lot gets put under another insulating cover, hence the double insulation. It's then considered unnecessary to ground the casing since the chances of any internal short causing it to become are energized are extremely small.



A good point. If I'm going to accidentally hit an energized conductor with a drill bit, I'd much prefer the whole case to be grounded in the old style than to be "double insulated" but with continuity to the chuck.

Thanks, Paul!!

Mike (mamills)

wow, my dads got one of those 1/2 drills.
damn thing doesnt stop for anything.
weighed a million pounds too.
used to have to use it when i was like 15/16 yo.made ya appreciate it, thats for sure.

Actually,
I'd never thought of the metal bit hitting a live cable with one of these drills, although metal appliances have always required an earth (ground) wire in them here.
I owned a Wolf drill that had a metal case on it for a few years, and as KJ said above, these drills don't stop for anything, thankfully my drill never had one of them trigger lock things that most drills seem to have on them these days. I think if it got out of control on you, all you could do is run away from the thing and possibly turn it's power off somewhere.

Don't laugh guys. My old boss had one of those drills that I had to use when I was a young apprentice just starting out. As for the 3rd wire, well it didn't exist. Somewhere I beileve it was missing and never used. I remember drilling holes in a damp and wet basement. The water had seeped into my shoes and the drill had a small voltage leak. I pulled the trigger and got wacked. So what did my boss do, he gave me a cement cinder block to stand on in order to finish drilling the holes. No more shock! I can't believe how stupid, but lucky I was. It wouldn't happen like that these days.

My Dad has a whole bunch of metal power tools from the 50s and 60s, although they're all Black & Decker. He's got 3 of the "classic" drill design, plus a skilsaw, heavy-duty drill, right-angle drill, and some other things that escape me at the moment. IIRC, the "classic" designs have a grounded plug; not sure if it actually came with one, or if it's a replacement. Pretty cool collection, and they all still work just fine.