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I have inherited a chop saw, hooray, but it only has 2 prongs on it’s power cord. Is it safe to use? Is there a way to ground it? Thanks!

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    Does it have a "square-within-a-square" symbol on its manufacturer's label/nameplate? – ThreePhaseEel Aug 1 '18 at 3:47
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    Two protection schemes are better than grounding it: #1 the tool being double-insulated, and #2 GFCI protection on the circuit you plug it into. GFCI isn't just a funny receptacle, it can be a breaker or inline module, or a receptacle that also protects downline plain outlets. – Harper Aug 1 '18 at 5:18
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    Are you saying it only had two prongs when new, or that the ground prong is broken off? – isherwood Aug 1 '18 at 15:13
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In a two-prong device, if there is a short from the hot wire coming in from the wall to the metal housing of the device, the metal housing becomes hot too, which is a shock hazard.

The third (earth ground) prong simply returns current to earth in case of a such a short so the housing doesn't become hot. If this kind of short happens and you have a third prong, you'll pull lots of current momentarily from the wall through the housing down to earth ground at the moment the short occurs and trip the breaker. If you don't have a third prong, you become the conduit between the hot housing and earth ground when you touch the device, which could be long after the short mechanically has occurred, since the short is "waiting" for a return path -- i.e. someone touching the housing.

Anyway, if the saw has a metal housing, definitely replace the cord. If the saw has a plastic housing, the risk is lower. You can add an earth ground by replacing the power chord and tying the earth ground prong to the metal inside the unit. I usually do this with a ring lug if I can find something threaded inside the chassis. You could also clip the metal housing to something else nearby that is earth grounded (three-pronged), since earth grounds should, by definition, all sit at the same voltage.

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    No need to replace the cord, though, unless OSHA is involved. Just the plug. – isherwood Aug 1 '18 at 15:14
  • True, if it's a three-conductor cord. If it's a two-conductor cord, you would replace the whole thing. – schadjo Aug 1 '18 at 15:19
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    A double insulated motor or any device only needs 2 conductors. A plant I worked at for many years had all there coffee machines that were 2 wire changed to 3 wire and a ground lug added to the hot plate. The funny thing during our Factory mutual insurance review that inspector pointed out that now they all had to be replaced because the modification invalidated the UL listing. Since the listing was no longer valid they couldn't give them to employees and tossed them in the trash there were over a hundred just tossed FWIW. – Ed Beal Aug 1 '18 at 17:03
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Look for a symbol like this, the "box within a box" as described earlier. It means it is "Double Insulated" and the grounding pin is not necessary.

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