Advice sought from the Electric Tool Experts?

[Nicholas Scheuer]

All of my power tools have grounded plugs, save three. The newest of the three is a Porter Cable "sawzall" (I know, "Sawzall" is a Milwaukee trademark), The other two are probably pre-1940's equipment; a Delta, floor-standing Drill Press, and a McGraw-Edison 1/2', 6amp, 550 rpm, hand-held drill.

I'll assume the Porter Cable folks knew what they were doing, so my question really concerns the pair of old tools having all-metal cases. Would it be a good idea to replace their two-wire power cords and plugs with three-wire stuff grounded to the housings?

Moby Nick

[merlinron]

essentially. the neutral(white) wire in 120 volt systems and the actual "ground" wire end up in the same place at your service box.... on the ground bar....which does raise the question you ask. two wire chords on hand held tools didn't show up until plastics were produced that were strong enough to serve as the tools' housing. being plastic, a non-conductor, grounding to the housing became a moot point... no electrical shock from holding the tool because you're insulated by the tools' plastic body, but your metal bodied tools will definately shock you, the neutral circuit is not connected to the body on those tools and i would not chance relying on the neutral circuit for the same protection on those tools.

[Nicholas Scheuer]

BEFORE grounded three-wire plugs and sockets even existed.

So you're suggesting it would be a good idea to refit them with three-prong plugs?

Moby Nick

[Frank Wentzel]

Absolutely! Grounding the tool will aviod YOU becoming the grounding conductor in the event of an insulation failure. Also note that, because of other devices operating on the same circuit, the neutral wire can be operating well above ground potential and not be able to provide full protection from insulation failure. Another suggestion is to put your whole shop on ground fault protectors. An electrocution can wreck your whole day!

/// Frank ///

[Nicholas Scheuer]

the table saw won't trip a circuit breaker when I'm sawing thick hardwood. It would certainly make sense to incorporate Ground Fault protection then.

Moby Nick

[Bob Cleek]

Definitely! Install a GFI on each outlet circuit in the shop and anywhere else water and power might come together. A lot cheaper and easier than rewiring all your tools and you'll save trips to the panel box to reset circuit breakers, if that's a problem.

[Hughman]

I have '50's King Seely jointer and tablesaw with 2-wire plugs in two separate circuits. One circuit is GFI protected. These tools are placed near each other, such that I once placed a hand on each and received a stout shock. GFI didn't trip.

I then connected these two machines with a metal bar, and tripped the GFI.

Should I add ground wire to these, or just replace motors?

[Andrew]

Definitely! Install a GFI on each outlet circuit in the shop and anywhere else water and power might come together. A lot cheaper and easier than rewiring all your tools and you'll save trips to the panel box to reset circuit breakers, if that's a problem.

I thought that a GFI on the first outlet off the panel would provide protection for all outlets on that leg. Is there any advantage to replacing all outlets with GFIs?

[Bob Cleek]

No, there is no point in putting a GFI in every recepticle. As I said, a GFI on each "circuit" coming off the panel. Follow the instructions that come with the GFI recepticle.

Hughman, I also have a lot of old "Amuricun Arn" that seems to have been built before the invention of the ground. The shocks you were getting from your power tools may very well have been the result of static electricity. I discovered this when I put rubber wheels on my old table saw stand, which used to have metal legs sitting on the concrete floor. The shock could not come from the motor, which was isolated from the saw body. Those belts, particularly the older rubber composite ones, can generate a lot of static electricity if they are rubbing against metal, or so it appears. I solved the problem by bolting a piece of chain to the metal leg and letting it drag on the ground. Grounding the metal body of older stationary power tools was standard practice back when, I later learned.

[Canoeyawl]

Hugh,
I would be alarmed at what you describe. Use your handy little voltmeter and measure the potential between those two machines. I have seen older circuits wired incorrectly giving a full 220V between a neutral line and a different circuit’s hot line. Dam scary it was… it only showed sparks on rainy days.
And back on subject Nick, I would ground the older hand held tools and use a new style three-wire cable and three-prong plug.

[Nicholas Carey]

I thought that a GFI on the first outlet off the panel would provide protection for all outlets on that leg. Is there any advantage to replacing all outlets with GFIs?The one advantage is that when it trips, you know exactly which GFI needs to be reset. After the GFI trips, depending on how you wired it, you'd either lose power to just that outlet, or to all downstream outlets.

You can also install GFI breakers in the load center, thus protecting an entire circuit. The downside to that is that after the GFI breaker trips, you (1) lose power to the entire circuit, and (2) you have to go to the load center to reset it.

[htom]

I prefer that each outlet have its own GFI, so that the trip only takes that outlet. I've seen too many places where the outlets and lights were on the same circuit, and the tool took the lights, leaving you in the dark with a tool winding down!

[Nicholas Carey]

One other thing about GFI circuit breakers in the load center: they're much more sensitive than GFI outlets, and thus much more likely to trip unnecessarily.

Whether that constitutes a safety feature or a defect is left as an exercise for the reader :p