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Another 240 vac question

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  • Another 240 vac question

    I have machinery that can be wired 120 or 240, and went with 120 (so far) just because I was putting stuff back together the way it was taken apart.

    I have a Sheldon 10" lathe with a 1/2 hp motor, wired presently for 120 but can be wired for 240. Making a few test cuts, it is just a little lightweight, but not if you shift to a lower gear- still the higher speed is desirable if I can get it.

    I know that 1/2 horse is 1/2 horse whether voltage is 120 or 240, but I am wondering since 240 has two legs (instead of 1 leg and neutral for 120) if that would be a benefit. I know it would not use more power, actually less, but I am thinking that what power (two 120 legs out of phase) it uses would be used more efficiently.

    Is my thinking correct on this?

  • #2
    The only benefit you will get is less voltage drop in the wiring from the panel to the lathe because at 240V you will draw half the current.

    At 1/2 horsepower(~350W) or 3.xA you wouldn't get much voltage drop anyway.

    My Dad always said, "If you want people to do things for you on the farm, you have to buy a machine they can sit on that does most of the work."


    • #3
      The only efficiency gained is if you have a power cord or outlet wiring that is too small. At 1/2 HP, it's hardly a concern.


      • #4
        It makes no difference if you use 240v or 120 as far as any neutral is concerned, BTW it uses the same power (watts) it is the current and voltage change at same ratio, higher voltage, less current but same wattage (power).
        The phase difference between the 240v conductors is the same as the phase difference between one leg and neutral, 180deg.


        • #5
          Agreed, No diffrence unless you have a 100'+ 16awg crappy extention cord running the lathe
          Play Brutal Nature, Black Moons free to play highly realistic voxel sandbox game.


          • #6
            I have been told (but haven't personally seen) that many single-phase motors start more quickly when wired for 220.


            • #7
              If you've got an existing 240v receptacle near the lathe and wanna spend a few minutes to switch the wires around in the motor, then just do it to sorta satisfy yourself -- if you gotta run a new drop for a receptacle, its a waste of time.
              If everything seems to be going well, you have obviously overlooked something........


              • #8
                Lights blink less when heavy loads are on 240..... not much effect on a half horse lathe.

                Can be a bigger deal with a 1 HP table saw...... they can suck down teh line spinning up on 120V.


                I've never seen a "lightweight" Sheldon, even a 10"...... I HAVE seen a 10" Sheldon that must have weighed over 1200 lb.... They made 'em solid.

                I bet you could easily put a 1 HP on that machine, unless it is unlike any other Sheldon I ever saw.

                Keep eye on ball.
                Hashim Khan


                • #9
                  I don't think 1/2HP on a lathe that size is going to do a lot of heavy cutting at high speed. The material and tool will make a lot of difference and good sharp HSS tools with a positive rake will cut a lot better than most carbide zero rake tools. The voltage connection does not make any detectable difference. By the same token, 1/2HP may keep you from breaking or otherwise damaging the lathe.
                  Don Young


                  • #10
                    Originally posted by metalmagpie
                    I have been told (but haven't personally seen) that many single-phase motors start more quickly when wired for 220.

                    Ill vouch for that. My table saw starts up much faster on 240. Simple reason really, there is a high current on start up. A 240 its half the instant draw of 120v so there is less drop in the wiring.


                    • #11
                      By the same token, 1/2HP may keep you from breaking or otherwise damaging the lathe.
                      I had thought about that- if I understand my research right there were some of them that came with a 3/4 horse motor. My little 9 x 20 has a 3/4 horse, but then again its fully belt driven. I had considered upping the motor size, but probably won't. If I could gain some out of it by going to 240 volts, it might be worthwhile, but it would be a PITA to run the wiring to do so.

                      To be honest, checking it out I was taking an 0.080" pass on a diameter of approximately 2 1/2", and it wanted to stall the motor. This was in high speed, but if I switched to the back gear it would take the cut, albeit slowly (300 rpm). I realize that is an ambitious cut, kind of lets see what this baby can do!

                      Someone said Sheldon made a solid lathe, and I have to agree.