220 V wiring question

I recently inherited my dad's Delta/Rockwell Unisaw with a 220V motor. The saw is a dream to use compared to my old Craftsman.
Luckily my shop is wired for 220 but I have a wiring question...
The wall plug is a 4 blade and the saw has a 3 blade plug so I need a new plug for the saw. I was going to just buy a new 4 blade male plug and replace the existing 3 blade on the saw.
So do I wire the ground/common from the saw to the ground or to the common on the plug? I can't seem to figure out which is appropriate.
Or should I just buy a length of 12/3 and use all 4 lugs? Does it matter? I assume if I did that all I would need to do is screw the ground to the saw frame somewhere... right?
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You have a 120/240 receptacle. Your saw is 240 only. The best option is to add another receptacle with the right configuration. You will have 2 hots and a ground, no white.
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snipped-for-privacy@aol.com wrote:

If I understand your comment...the receptacle is a 220v only. There is no way to plug in a 120v line and it has a 40 amp breaker.
So you are saying wire the "common/grround" from the saw to the ground on the receptacle... right?
Thanks!
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LA wrote:

does not use 110v for anything. The outlet has a neutral, so it has 110 available. You should be able to change the plug to one that will fit the outlet, ignoring the neutral.
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LA wrote:

No he wrote and was right that the receptacle is both 120 and 240 supply. You saw only can use the 240 part of that. Some things like an electric range will have 240 heating elements and maybe a 120 clock so they need both.
You could replace the plug on the saw and you would not connect any wire to one of the connectors on the plug (the one that feeds the white wire, you would only connect the red black and copper-green or as he suggested and so do I, leave the plug as it is on the saw and replace the receptacle on the wall with one that will fit the existing plug designed for 220 only, you would not connect the white wire to any part of that receptacle.

The common and the ground are NOT the same thing. The only place the connect is in the breaker box any where else the white is a current carrying wire and should be treated as such, the ground is the only ground wire.

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Joseph Meehan

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Ahhhh.... I understand. Thanks Joeseph
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On Mon, 10 Jul 2006 19:34:11 GMT, "Joseph Meehan"

Sometimes they're connected together (often in 240V 3-wire cords).

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Mark Lloyd
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Backwards. The four hole socket (not a four hole plug) has 220 and 110 available.
The cord to your saw is 220 only.
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Christopher A. Young
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I'd be very surprised if there was a plug coming out of the wall. Totally unsafe. Should be a socket.
You can replace the plug on the saw if you wish. Won't hurt anything.
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Christopher A. Young
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On Mon, 10 Jul 2006 21:17:11 GMT, "Stormin Mormon"

A lot of people get their gender mixed up :)
BTW, I know someone who wanted a "double male adapter" for 120V (after having put up some holiday lights wrong). That's a socket connected to 2 plugs.

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LOL...
Yes... I have a "socket" in the wall. I had a new shop built on and it was wired for 220 by a professional. I'm just an amateur trying to figure out how to plug in my saw...
Thanks all... I think you straightened me out and I know what to do next.
I appreciate the help!
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LA wrote: ...

Well, you left me _very_ cornpuzzled... :)
A 4-hole wall outlet isn't what you want for a shop--that's for something like a range or a clothes dryer.
What you really should do to do it correctly (but you don't say what you think it is you think you know :) ) is get the proper socket for the wall to match the saw and that matches the breaker amperage of the circuit you're going to use. That is, don't use a 220V/15A rated outlet in a 20A-protected circuit. The other way 'round is fine, (20A outlet on a 15A circuit).
While it would function to put a plug on the saw to match the existing outlet, why butcher a tool to a non-standard configuration when it's just as simple to put the correct outlet in the wall? Plus, if you're making a shop, you should standardize on a particular outlet choice simply for future convenience.
IMO, YMMV, $0.02, etc., ...
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Use a four prong plug on your existing cord. Just use the two hots and the ground, no need for a neutral.

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It's probably a trifle cheaper and somewhat easier (aside from having to kill the breaker) to change around the receptacle on the wall than the plug on the cord.
Retrofit 220V plugs are clunky things. I'd prefer to leave a molded cordset alone (if that's what the saw has), and do my changes with solid copper.
Presuming of course that the thing isn't over-breakered for the receptacle that matches the saw plug.
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Chris Lewis, Una confibula non set est
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