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Need a new motor for South Bend

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  • Need a new motor for South Bend

    Since I’m not a trained machinist, just a guy with enough tools and interest to be dangerous, I need a new motor for my lathe. I have a South Bend 9C and the motor (not original) is giving up the ghost. The original reversing switch burned out a couple years ago. At this point, I have a new switch ready to go, but I’m looking for input on a motor. While I can accomplish basic wiring stuff and can likely hook up the switch when the time comes, I’m not a guru on electric motors.

    Suggestions on what would be best for this lathe?

  • #2
    Without question, a 3 phase motor and a VFD, will give you variable speed, and smoother running. It doesn't have to be complicated. A TD200 drive from FactoryMation, and a cheap 3 phase motor, 1 HP or less.
    Don't be intimidated by the VFD, TD series VFD's have plenty of documentation. Watch some Youtube.

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    • #3
      How about a motor of at least 1/3 HP, and 1725 rpm ? ..... A 3/4HP would be as much as the machine can use, possibly more than it can use. A motor of 3450 rpm is probably too fast, the speeds will have been set up for a 1725/1750 rpm type motor.

      The idea of 3 phase is good, but adds cost and complication, when a $10 yard sale motor will do the job just fine.

      I do like 3 phase, and have it in my shop, via an "RPC", so that I can use t with any 3 phase machine I have. It works very well indeed with a flat-belt drive, with a lot less trouble from chatter and belt slipping than single phase. I had the same lathe originally using single phase, and the difference was huge when I changed to 3 phase..

      Single phase works, and is much cheaper, though.
      CNC machines only go through the motions

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      • #4
        Without a doubt a three phase motor and vfd would be awesome. The ability to tweak the does on the fly can be invaluable, particularly for parting and facing. 1/2hp would be a good size

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        • #5
          How do you know the motor is giving up the ghost? Is it possible it just needs a new capacitor or new bearings? That may be easier than adapting a new motor, although a VFD would certainly be handy. It used to be that you could find small 3-phase motors pretty cheap because the hobby guys didn't want them (not having 3 phase power in their shops) but I suppose, with the availability of low cost VFDs, that might be different now.

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          • #6
            I have a SB 9A and I replaced the motor with 1/3HP, 3ph 1725RPM and a TACO VFD, I think I got it all from Automation Direct. Definitely more $ than a yard sale motor, but I like the easy speed control. One downside is that this VFD will trip a GFCI due to the input line filter, so I am running off a non-GFCI outlet.
            Chris

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            • #7
              I know I can’t get 3 phase at my house so Im guessing a phase converter would also be necessary. Setting all that up would be pricey, but I like the idea of variable speed. Would any 1725 rpm motor of 3/4 hp be able to run backward with the reversing switch? I was warned about that issue in the past by a guy who repaired electric motors.

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              • #8
                Originally posted by Fasttrack View Post
                How do you know the motor is giving up the ghost? Is it possible it just needs a new capacitor or new bearings? That may be easier than adapting a new motor, although a VFD would certainly be handy. It used to be that you could find small 3-phase motors pretty cheap because the hobby guys didn't want them (not having 3 phase power in their shops) but I suppose, with the availability of low cost VFDs, that might be different now.
                It’s doing the same thing the old one did, starting to hum, and every so often I can smell it. Haven’t noticed any smoke yet, but the last one went just like the switch, in a puff of smoke. Bearing seem ok.

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                • #9
                  Originally posted by Tincamp01 View Post
                  It’s doing the same thing the old one did, starting to hum, and every so often I can smell it. Haven’t noticed any smoke yet, but the last one went just like the switch, in a puff of smoke. Bearing seem ok.
                  Start cap? Coil? Either way, VFD and 3 phase would be a very good upgrade if not just a fix.

                  Comment


                  • #10
                    Originally posted by Tincamp01 View Post
                    I know I can’t get 3 phase at my house so Im guessing a phase converter would also be necessary. .
                    Good news, you don't need 3 phase input.

                    example

                    https://www.automationdirect.com/adc...micro/gs1-10p5

                    Comment


                    • #11
                      Originally posted by Michael Edwards View Post

                      Good news, you don't need 3 phase input.

                      example

                      https://www.automationdirect.com/adc...micro/gs1-10p5
                      Yes, and you are in the size range that you can get one with 120v single phase input voltage.

                      Stated already, it is more of a cost but now might be the time to do it especially if you were going to buy a new motor rather than looking for a used one.

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                      • #12
                        Start switch internal to the motor, near end bell is going bad. Often a weak spring, simple replacement, cheaper than a new motor.

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                        • #13
                          Originally posted by Tincamp01 View Post
                          It’s doing the same thing the old one did, starting to hum, and every so often I can smell it. Haven’t noticed any smoke yet, but the last one went just like the switch, in a puff of smoke. Bearing seem ok.
                          That's a classic symptom of a failing capacitor or bad start switch inside the motor. Personally, if you've been happy with the performance up until now, I'd just replace the cap and see how it goes. You can pickup cheap run or start capacitors from places like McMaster, Grainger, even Burden's Surplus Center for ~$5.

                          I don't know anything about the motor that would be on your Southbend but you should be able to get all the help you need to troubleshoot it here. Could be as simple as popping off the cover of the cylindrical appendage where the capacitor lives and reading what it says on the capacitor. It will give a voltage rating and capacitance rating either in "uF" or "MFD", both meaning "microfarad". You just need an approximate match of these values and the overall physical size to replace it.

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                          • #14
                            I would like to have the revers option back and I don’t think this motor can be set up that way from what I remember. I’ll spend some time pricing the 3phase set up and see what it looks like. Appreciate the input.

                            Comment


                            • #15
                              Originally posted by Tincamp01 View Post
                              I would like to have the revers option back and I don’t think this motor can be set up that way from what I remember. I’ll spend some time pricing the 3phase set up and see what it looks like. Appreciate the input.
                              You can wire your new drum switch to control the VFD as well.

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