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Single phase small electric motor from graduate wood lathe ?

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  • Single phase small electric motor from graduate wood lathe ?

    Ok my son has a small short bed Harrison graduate lathe . When we fire it up it hums does not seem to respond to spinning the spindle by hand. Then it starts and runs fine. When you switch it off it starts again to hum ,you must try on and off a number of times to get it to fire up when it does start it runs beautifully. Here is the crunch when you get it to run and leave it running for a few minutes under five minutes, after that it seems to warm up or acclimatize itself to the situation and as long it has gone through this first stage of switching on and off till it gets the message it can be run all night like this, switching on and off perfectly fine. It seems to be when it is off for a short while you have to go through the whole rigmarole again. I suspect the 100miro farad capacitor. I cant see how it could be the internal switch centrifugal as surely it would not run normally on and off after the initial warming up (as I call it)period any ideas. as said 220-240volts single phase motor. Usually Harrison will have fitted a high quality European motor not Asian. Any tips or help let me know.
    Also can someone tell me about the situation with Evan?
    Please excuse my typing as I have a form of parkinsons disease

  • #2
    It may BE the switch.... if it has crummy contact pressure, and needs to break through the oxidation.

    Could also be the capacitor, if the capacitor warms up so things expand and make good contact inside where there is a bad connection when cold.

    Could even be something bad with the wires to the capacitor or the winding.

    If you want to try fixing it, you can see if there are any unusual flashes from inside at the beginning of the evening of work, that might signal a bad connection. Or you can just replace the cap and see if that fixes it. The switch itself is too much like work to replace on spec.
    Last edited by J Tiers; 11-01-2017, 07:08 PM.
    CNC machines only go through the motions


    • #3
      Ensure it is a motor start capacitor rated, a regular 100µf electrolytic will not be suitable.
      Any local motor rewinder's are a source.
      Stay away from Chinese origin caps.


      • #4
        Anyone else want to chip in with their ideas? Al
        Please excuse my typing as I have a form of parkinsons disease


        • #5
          when the motor is running when you switch it off you should be able to hear the centrifugal switch closing about a couple of seconds after removing power
          Try this with the belt disconnected and the door to the motor open and the switch defeated.
          Your motor may not have a centrifugal switch though
          if you take the belt off and spin the spindle when machine is cold does it spin freely? could be spindlle bearings got old congealed grease in you have the manual screw cups or zerk fittings?
          when spindle warms grease runs and then motor can start

          if after all this you may have to remove motor...its difficult sometimes depends on how big a motor someone has fitted
          I have 2 graduates one long bed one short



          • #6
            Any follow up Al?


            • #7
              any result yet?