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HELP!!! Lathe motor problem

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  • HELP!!! Lathe motor problem

    Help!
    My lathe motor stopped running again today. The first time it quit, I thought it was the breaker.
    Today it will "HUMM" when I throw the switch, but it won't spin.
    The bearings, belts, and chuck all spin easily by hand.
    What could be the problem?
    110v , 1 phase

  • #2
    Centrifugal start switch.

    --Doozer
    DZER

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    • #3
      Most likely a start capacitor. If it has a centrifugal switch that could be it also. Do you know what kind of motor it is?
      Last edited by Boucher; 02-09-2010, 09:41 PM.
      Byron Boucher
      Burnet, TX

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      • #4
        What brand of lathe and motor. Could be as simple as starting capacitor..You just down the road from me . Other side of Longview.
        Every Mans Work Is A Portrait of Him Self
        http://sites.google.com/site/machinistsite/TWO-BUDDIES
        http://s178.photobucket.com/user/lan...?sort=3&page=1

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        • #5
          Tiawan motor on a Jet 1236P lathe.
          Single Phase - induction motor
          Capacitor starting
          2Hp - 115v - 28A - 60Hz - 1720 RPM

          There are two starting capacitors mounted on the backside of the lathe bed, near the motor.
          Could these be the culprits?
          If so, where can I find replacement capacitors on the quick?

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          • #6
            Originally posted by KiddZimaHater
            What could be the problem?
            110v , 1 phase
            It's trying to tell you that you'd be better off with a 3ph and VFD.

            Comment


            • #7
              Originally posted by MTNGUN
              It's trying to tell you that you'd be better off with a 3ph and VFD.
              Indeed. Replacing the motor with a 3 phase and adding a VFD will be the best thing you ever did for that lathe....and for you.

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              • #8
                2 capacitors? one starting one running.
                my guess is start switch contacts are burnt. temp fix- open case and sand contacts with fine grit flint sand paper (power off of course) and buy new ones...
                could be capacitor - usually there is a opening near the terminals - if bulged out replace.

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                • #9
                  Pics:

                  .

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                  • #10
                    (power off of course)
                    You need to do more than just power off with capacitors - you need to discharge them before touching them of you could get a shock. jump the two terminals together with something like a screwdriver with a nice insulated handle.

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                    • #11
                      Spin the motor by hand and apply power as it spins. It should start or attempt to start.

                      The last time I had this problem the start cap. was an open circuit. The local elec.supply house had one and all is well.

                      Good luck
                      Jim

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                      • #12
                        It's a good idea to know if there's voltage stored on a cap before playing around with wires and connections. Discharging with a screwdriver might be fun, in fact it is at times. And you could learn a bit about EDM. Sometimes a single shot from a charged capacitor is enough to blow a little gouge right out of the blade- I've seen it done and done it myself. Might I recommend two things- one is get a simple voltmeter and learn how to made some simple voltage and resistance checks, and the other is to make yourself a 'shorting stick'. This could be as simple as two insulated probes connected through a bit of resistance.

                        I think as time goes on we're going to be seeing more and more electronic devices where the ac input voltage is rectified and filtered, and the capacitor involved has a likelyhood of remaining charged for some period of time. It just seems like a good idea to have a sort of 'safe' shorting method, then be able to measure whether the voltage is actually discharged.
                        I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-

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                        • #13
                          I've seen starting capacitors with resistors across the terminals.


                          They keep the capacitor from holding a charge for long after the equipment is turned off, and they reduce arcing on the contacts of the start switch. The resistance is high enough that the starting function of the capacitor isn't impaired.
                          Last edited by winchman; 02-10-2010, 04:01 AM.
                          Any products mentioned in my posts have been endorsed by their manufacturer.

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                          • #14
                            2 starting caps indeed- new to me.
                            discharging - missed that one - thanks
                            My Fluke((TM) meter will test caps- know anyone with one?
                            A motor shop could help here.

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                            • #15
                              Originally posted by KiddZimaHater
                              Help!
                              My lathe motor stopped running again today. The first time it quit, I thought it was the breaker.
                              Today it will "HUMM" when I throw the switch, but it won't spin.
                              The bearings, belts, and chuck all spin easily by hand.
                              What could be the problem?
                              110v , 1 phase
                              If you have not yet determined the problem, may I suggest that you check for loose wiring where wires enter the motor. I recently experienced a very similar problem and similar symptoms with my PM12X36 Chinese lathe. At first I thought it to be caps. It was not. Wiring at the motor had worked loose causing the wires and insulation to heat and melt! Fortunately the motor was not damaged.

                              While the lathe was away from the wall and the motor at the electric shop for examination, I replaced the Chinese motor with a new Baldor premium 3 phase motor and a VFD. I have absolutely no regrets. Runs quieter, much smoother, and I have the latitude for a wide range of speed control with full use of the gears. A great upgrade to consider.

                              Harold
                              For those having fought for it, Freedom has a flavor the protected will never know.
                              Freedom is only one generation away from extinction.

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