Wiring PM lathe 220v ?

[Roy Fek]

Hello,

I just received today a Powermatic 3520b lathe. It came wired with a pigtail but no plug. The pigtail has three wires - black, white and green. The lathe operates on 220v and I have a 220v outlet in the garage. The outlet has three "openings", sorry, I don't know the right term. Two of the openings are slanted and the third is "L" shaped. I've seen this kind of outlet/plug on clothes dryers.

I want to power the lathe via this outlet and so I bought a plug to match from Home Depot. The instructions for the plug say "Caution: this device is not for grounding use. Connect to non-grounding circuits only, unless it is to be used for a range or clothes dryer." It also states that the white lead should be attach/screwed to the "L" shaped blade and the other two remaining wires, I'm left with black and green, should be attached to the two slanted blades.

Is this going to work? I thought the two slanted blades were hot and the "L" neutral. So, attaching my green wire to one of the slanted blades doesn't sound right. Where's my ground? Do I need a Different kind of outlet/plug?

Any help would be MUCH appreciated!!! Thanks, Roy Fek

[Toller]

should be using a 6-20. (How many amps is the lathe?) You are probably using 10-30, you are reusing an old dry outlet and there is a 30a 240v breaker on it, right?

I would replace the breaker and outlet, and get the right plug. Other people would say that was a waste of money. They would just connect the ground of the lathe to the neutral on the plug and use it that way. But you are right, the green is ground and would go where the neutral is supposed to go, the two hots going to the blades. The 10-30 is made for two hots and a neutral, hence the non-grounded circuit. Since your lathe does not have a neutral (or so I am assuming; best check that....) you can use the neutral for your ground. I am also assuming this it going to a panel, rather than a subpanel. The neutral and ground go to the same place on the panel, but not on the subpanel.

[Josh]

If possible, you should replace the recepticle, like Roy said. Hopefully the original installer ran something like 10/3 wire to it. That means that it should have black, white, red, and bare (or green) wires. Then, it's a simple switch-over to put in a four-prong recepticle like a NEMA 6-20; just wire as the directions show. Then connect green from your pigtail to the ground terminal on the four-prong plug, and connect white and black where the directions say to put red and black. The neutral terminal on the plug will have no connection (even though the directions will probably say to connect the white wire there).

However, given that there's only a 3-prong outlet now, there's a reasonable chance that the installer only ran 10/2 (white, black, and bare) to it. In that case, the RIGHT thing to do is to rerun 10/3 or

12/3 wire from the box, but that's a huge pain. It's very unlikely that your lathe requires a neutral connection (and if it did, one would hope that their supplied pigtail would have black, red, white, and green). So if you're one to take shortcuts, keep your three-prong plug and connect the green wire to the L-shaped prong, and the white and black to the slanted prongs. The neutral should technically be grounded back at your main panel.

If you really want to be sure, using a multimeter (sometimes called a VOM), you should be able to measure a short circuit between the green wire and any exposed metal on your lathe (thus verifying that the green is, indeed, ground), and some relatively low resistance (maybe somewhere between 0.5 and 5 ohms) between the white and black wires. There should be an open circuit (very high resistance) between the green and either of the other two.

Josh