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Thread: Motor problem on sander

  1. #1
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    Motor problem on sander

    I have a 6" disc 4" belt sander I am trying to fix. its from the 80's and probably not worth much time. I don't even recognize the name or remember it for that matter

    when I turn it on it hums until give the disc a tiny turn and then it runs very smooth. I have turned it on and off a bunch of times hoping it was just sticky or something from not being used in over a decade but it didn't help.

    once in a while it will turn without help but its like 1 in 20.

    Any ideas on what it could be.

  2. #2
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    Check the centrifugal switch on the back end of the motor, it might just need to be blown out with your air hose, sometimes sawdust messes with the contacts in there.

  3. #3
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    A sander that size probably has a universal motor. Depending on the machine, it may or may not allow access to the brushes. If so I would remove the brushes and blow out that area to be sure it is fairly clean. If it is of the heavier breed of these handy small sanders (cast iron body, replaceable platten and so forth) I would forge ahead trying for a manual, parts list or even a repair shop. If it is of the stamped steel, 20 pound, no-name family of these machines I would probably scan garage sales for a used one to replace it and move on. You may be surprised how easy access to manuals and parts are for some of the darndest things. I have gotten help with things I thought were definite throw-aways so, punch in the model and make if you get a chance. It may live to fight again
    Any sufficiently advanced technology is indistinguishable from magic.
    - Arthur C. Clarke

  4. #4
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    Quote Originally Posted by Charles Hans View Post
    Check the centrifugal switch on the back end of the motor, it might just need to be blown out with your air hose, sometimes sawdust messes with the contacts in there.

    I found that mechanism your speaking of and it seems very clean so I can rule that one out. thanks

    Quote Originally Posted by glenn bradley View Post
    A sander that size probably has a universal motor. Depending on the machine, it may or may not allow access to the brushes. If so I would remove the brushes and blow out that area to be sure it is fairly clean. If it is of the heavier breed of these handy small sanders (cast iron body, replaceable platten and so forth) I would forge ahead trying for a manual, parts list or even a repair shop. If it is of the stamped steel, 20 pound, no-name family of these machines I would probably scan garage sales for a used one to replace it and move on. You may be surprised how easy access to manuals and parts are for some of the darndest things. I have gotten help with things I thought were definite throw-aways so, punch in the model and make if you get a chance. It may live to fight again


    I will have to take a closer look to see what kind of motor it is. so far I see no way of easily getting to the brushes.

    It really runs very smooth with little noise when its going and it take little to get it to spin.

    I did notice a heavy green spark flashes if I get it spinning with a light tap on the motor housing but that doesn't happen if I give the disc a push.

  5. #5
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    If there is a centrifugal switch there are no brushes in the motor, What disc are you referring to? The sanding disc? Does the motor have a capacitor on the outside of it?
    .
    Last edited by Charles Hans; 05-29-2013 at 02:12 AM.

  6. #6
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    Charles is right on target. If you found a cent-switch, don't bother looking for brushes . The good news is that starter caps are inexpensive and easy to source if that turns out to be your issue. You may be able to source them locally but, if not, the folks at TEMCo have always been very helpful over the phone.
    Any sufficiently advanced technology is indistinguishable from magic.
    - Arthur C. Clarke

  7. #7
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    Quote Originally Posted by Charles Hans View Post
    If there is a centrifugal switch there are no brushes in the motor, What disc are you referring to? The sanding disc? Does the motor have a capacitor on the outside of it?
    .


    Yes. the sanding disc. I barely have to turn it in order to get it working. Not sure about the capacitor. there is a plate on the side I am going to look into today



    No capacitor that I can see any where in the motor. I thought they would have been in the little humped panel where the power lead goes in but they are not there.
    its a 1/4hp toyang motor from 1986.
    the sander is a rtc and does have a cast iron base and I'd like to fix it but I don't know what to do. maybe i'll just use it the way it is because its on a stand and my old craftsman 6"/4" sander is lighter with no stand.
    Last edited by keith Boutselis; 05-29-2013 at 02:17 PM.

  8. #8
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    Keith, if there is no Cap. you definitely have a problem with the centrifugal switch. you will either have to look at it closely to find the problem and repair it, or replace it to solve your problem. If you are getting sparks from it when you tap on the end while it is running the contacts are not closing as they should. Hope this helps

  9. #9
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    In a brazen attempt to make up for sending you down the wrong path earlier, I will report a recent motor repair of my own. It should be obvious that this is not my area of expertise but, I still managed to stumble through so I'll bet you can too. In my case the motor did have a starter capacitor and a run capacitor but, disregarding that I also had to deal with the centrifugal switch assembly. This was a larger motor and therefore probably had a larger physical centrifugal switch assembly than yours but, the principal is the same. In my case the starter cap gives the motor a kick to get started. At a given speed the centrifugal force causes the centrifugal switch to "switch" taking the start capacitor out of play. Failure of the cent-switch contacts/function was blowing starter caps.

    I had cleaned the contacts and gone through the various steps to recover the switch. Everything "looked" good and moved correctly but, replacement of the switch contact assembly turned out to be the fix. The reason I am blathering on is to add credence to the idea of repair or replacement of the cent-switch. I wasn't able to track down anything on RTC or the motor company that would be any help but, an electric motor repair shop would be my next try. All the motor repair shops in my area closed up during the recent hard times so I had to take my next guess and have parts shipped to me. Hopefully you still have a local shop that could take a look. Best of luck.
    Any sufficiently advanced technology is indistinguishable from magic.
    - Arthur C. Clarke

  10. #10
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    Glen is correct, sometimes you can't see what is the problem with those switches, the parts wear so slightly that they just don;t work as they should. I did this type of work for 42 years and believe me i have been down this road Your best bet would be to have it checked out by a good repair shop

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