I have an old Craftsman table saw that has an external motor. It runs the blade via two belts. it only has a 2 wire non-polarized plug. If I remember right its circa 1942. Anyway, frequently when we lean against it with a sensitive part of the body, ( face, belly, leg ) we'll get a slight zap. Can a ground wire be added to this to stop it? Where would one place it?
signature Troy & Michelle Hall Cogy Farm Clay Center, Kansas 67432
Adding a ground would be illegal and dangerous. A ground is to protect you when you don't know there is a problem, not to let you use a defective tool. Don't do it. (It won't work anyhow if the short is from the hot; it would just trip the breaker.)
The short answer, combined with your question about the fence below, is to toss the saw; it just isn't worth it.
However,
1) Does the shock come when the saw is on or off? 2) Does reversing the plug change anything.I think its only when it is on and not always. It is VERY mild. Not a 110 shock. Which is whats weird. Not that I have noticed, but I haven't paid close attention to it. "Tossing" the saw is not at option at this time. I don't have $300+ to purchase a new one. This is a very sturdy tablesaw with a 9½" blade.
Yes. Go out and buy a length of 16ga cord with three conductors - usually Black, White and Green. Wire the black and white wires into your motor the way that it is currently wired and secure the green to the metal chassis of the motor. You can usually find a screw to slip the ground wire under and then tighten the screw back down. Wire a three prong plug to the other end and you're off. Maybe cheaper and easier is to buy a 25 foot extension cord and cut it down to the length you want. Wire the cut end to your saw and your plug end will be already wired in a nice factory molded plug.
You can also run a separate ground from the motor to a ground in the building, but that tends to get pulled loose or otherwise damaged. I like the first way better.
You have a problem that a ground will just cover up. If you want to keep the saw I would find where the current draw is, and correct the problem. If nothing else replace the motor, rewire the switch and inconnecting wires, then add a three wire cord. Many of those older saws were pretty good units, so it may be worth repairing properly. Greg
Nonsense, twice.
Electrical code applies only to premises wiring, not to cord-and-plug connected devices, so there's clearly nothing illegal about it.
And it obviously is less dangerous to properly ground the frame of the equipment than to leave it ungrounded.
Nonsense, a third time.
Chances are that there is nothing wrong with the tool. Did you notice the part where he said it's an unpolarized 2-prong plug? And if the tool *is* defective, adding a ground will *prevent* him from using it. Had you noticed that he *is* able to use it now???
Nonsense, times 4.
If the short is from the hot, he now has a table saw with an energized, ungrounded frame. If he adds a ground to it (e.g. by replacing the 2-conductor power cord with a properly grounded 3-conductor cord), _of_course_ it will trip the breaker -- which is obviously exactly the desired behavior if the hot is indeed shorted to the frame. In what sense is this "not working"?
Nonsense x 5...
Perhaps you should have ascertained the answers to those questions _before_ posting all that tripe.
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|> signature Troy & Michelle Hall Cogy Farm Clay Center, Kansas 67432 |>
| |Yes. Go out and buy a length of 16ga cord with three conductors - usually |Black, White and Green. Wire the black and white wires into your motor the |way that it is currently wired and secure the green to the metal chassis of |the motor. You can usually find a screw to slip the ground wire under and |then tighten the screw back down. Wire a three prong plug to the other end |and you're off. Maybe cheaper and easier is to buy a 25 foot extension cord |and cut it down to the length you want. Wire the cut end to your saw and |your plug end will be already wired in a nice factory molded plug. | |You can also run a separate ground from the motor to a ground in the |building, but that tends to get pulled loose or otherwise damaged. I like |the first way better.
Mike is right on, especially about buying an extension cord and cutting it to length. You buy a "pigtail" and it costs big bucks. Buy a 10' extension cord on sale for a few bucks.
As to the others bunching up their panties about *danger*, it's very possible the shock is from nothing more than static build up. If it's actually leakage in the motor, then the ground will at best make it safe and at worst will pop a breaker, in which case the OP can take the motor to a shop for troubleshooting.
Finally someone with the right approach.
The ground is most likely caused by the insulation in the motor getting old and starting to break down or a loose wire in the on/off button. With the unit unplugged open the on/off switch and see if the wires are in good shape or loose or if some bear wire is exposed. If all looks good in that department then its time to have a good look at the motor. What you will need to do a quick check on the motor is a meter called a megger. This meter will test the motor windings and indicate their condition. Since most people don't have a megger at home you just have to remove the motor from the saw and take in to a local motor repair shop. They can test it in two minutes and tell you if the winding insulation is the cause of the problem. And yes it would be a good idea also to install a three pronged plug on the unit after you get it up and running. If there is a slight ground on the unit in the future the ground wire will protect the operator from getting in the ground loop circuit and getting small ZAPS like you are experiencing now. If there is a bad ground the ground wire you installed will cause the breaker to trip which in turn lets you know that you have a bad electrical problem with you machine. Sorry for the long story but I think this pretty much covers everything. In any event don't through the saw out because of a grounding problem. Resolve the proble and you will most likely get another
30 years out of the little darling.Bill
Next to listening to Dan Rather, this is just about the stupidest thing I've heard all week. I'm guessing the OP has been shocked by static electricity in the past, so I think he knows the difference between that and an AC current. The only reason it's not that bad right now is that the hot isn't making a very good connection to the frame of the saw. Maybe one of these days, it will make a good connection. At that point, I don't want to have to rely on ground or a circuit breaker to protect me. If you think I'm getting my undies in a bunch, let's do a test. I'll hand you a steel bar connected to ground. You hold onto it and I'll connect it to 120. Sound like a good idea, genius? Here's a better idea. Find what's wrong with the motor now instead of trying to half-assed work around the symptoms.
todd
Illegal? Since when? I agree that it is appropriate to find the problem but since when is it illegal to add a ground to a device?
That is just plane bad advice.
electricity
For the record, let me say that I agree that if the motor is defective internally then it should be repaired or replaced. I jumped past that in my original reply. However, adding a ground in no way presents a danger or a stupid move to the OP. What do you suppose we use grounds for if not for the type of situation being discussed here? If you don't want to rely on a ground or a circuit breaker to help protect you from leakage from hot, then perhaps you should stay away from electrical appliances since that is the very reason for grounds.
To provide a margin of safety when accidents occur. If it's intentional, it's not an accident, it's stupidity.
Grounds protect you from accidental leaks, not intentional ones.
Plus, if your saw is in a basement or garage, it should have a GFI anyway, and using a ground that way would trip the GFI.
No, a ground is not appropriate for bypassing a KNOWN wiring fault to obviate the need for repairs. Grounds are a safety net, not a band aid.
Your points are well taken and I posted a different reply in which I indicated that I had jumped right past the matter of having the motor looked at. It remains however that the comments I replied to were flat out wrong in that they completely ignored the purpose of ground. Ground, according to the comments I replied to, has no real purpose.
It is illegal to establish wiring so that current is sent to ground rather than to the neutral. If the machine had been made that way, it would be simply unsafe rather than illegal.
I can't comment on that, but it is plain good advice. Bear in mind he also said his fence was unusable. How much money do you want to put into a 62 year old 9.5" table saw?
>
Utter nonsense. What on earth do you think an equipment ground is *for*, anyway?
So you think that *adding* an equipment ground to it makes it *less* safe than it is now?!
Amazing.
-- Regards, Doug Miller (alphageek-at-milmac-dot-com)
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I would love to test the voltage from the tablesaw, while running, to ground with a voltmeter. How much potential is actually present? The saw frame and construction may be dropping a bit of that voltage from load alone or maybe some complex impedance. And remembering back to some of the old radio days, we used to be able to polarize the radio by turning the plug around going to the outlet. But the old radios still had a voltage present (floating) and would arc badly if they came in contact with a grounded chassis.
Philski
Thats absolutely correct. Not only that, this is a BELT driven device. 2 belts actually. This creates a known energy field. Is it interacting? Lets face it not too many things were UL rated in the early 40's LOL I will be doing some measurements tomorrow to see what I can see. I should be interesting.
Whaaaaat?
In all this discussion of ground & neutral, may I comment that, at least here in USA, most places the code calls for the ground & neutral to be bonded together @ the building load center or entry panel?
Considering the age of this saw, I would hazard a guess that the power cord & plug are not original, and who knows what kind of a botch job was done by whoever replaced/wired it?
I believe the best idea is to do as someone else suggested; buy a new 25' extension cord, but in 14ga. not 16, and rewire. Chances are the on/off switch only switches one side of the circuit, in which case you wire the
*hot*, or black wire to the switch, the *neutral*, or white wire to the unswitched side, and the green to the frame. Now, if it pops the CB when you turn it on or plug it in, take the motor out & have it checked.The amount of money the OP wishes to spend is purely up to him, given how useable the saw is if fixed.
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