Motor problem on sander

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208
Location
central florida
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.
 
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 :thumb:
 
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

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 :thumb:



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.
 
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?
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Charles is right on target. If you found a cent-switch, don't bother looking for brushes :eek:. 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.
 
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?
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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.
 
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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
 
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.
 
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:rofl: Your best bet would be to have it checked out by a good repair shop
 
Not to dump cold water on this one, but anyone try to find a motor repair shop lately? Rare as hen's teeth. Especially for small motors. Doesn't seem to be a career option any longer.
 
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

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.



I looked it over again with the cover off and the sparks are coming from the centrifugal switch so charles is probably right on the money. I turn it on, hit the motor and then a bright green spark comes from the contact on the cent switch but if I just turn the sanding disc to get it going then there is no spark.

I took it out and used some emery cloth on the contact and tried again. there was no improvement.
I have heard a rumor of a shop that repairs electric motors in my area. I heard about it about 6 months ago but that would be cost prohibitive.


So I will just ask one more question before I put this sander to rest. Could I add a cheep capacitor to facilitate in the starting process. they are super cheap on ebay or I could just take one of some other appliance I'm scraping
 
If you don't mind giving the motor (or the sanding disc connected to the motor) a push, it should work just fine. A single phase motor has no starting torque, like bicycle pedals where you can only push straight down. The starting capacitor tricks the motor to start turning (like pushing slightly forward on the pedals), and the centrifugal switch gets the capacitor out of the circuit as soon as the motor is turning.

My bet is the starting capacitor (wherever it is hidden) has gone bad, but you can do the same job with your finger, each time you turn the motor on.
 
I was thinking along the same lines as Charlie...as long as no flames or smoke are coming out, I'd run it until it dies completely.
 
So I will just ask one more question before I put this sander to rest. Could I add a cheep capacitor to facilitate in the starting process. they are super cheap on ebay or I could just take one of some other appliance I'm scraping[/QUOTE]

If you don't mind giving the motor (or the sanding disc connected to the motor) a push, it should work just fine. A single phase motor has no starting torque, like bicycle pedals where you can only push straight down. The starting capacitor tricks the motor to start turning (like pushing slightly forward on the pedals), and the centrifugal switch gets the capacitor out of the circuit as soon as the motor is turning.

My bet is the starting capacitor (wherever it is hidden) has gone bad, but you can do the same job with your finger, each time you turn the motor on.

I was thinking along the same lines as Charlie...as long as no flames or smoke are coming out, I'd run it until it dies completely.



I was thinking there is no capacitor. I can't believe it could escape my sight unless its very tiny.

So I wanted to ad one. Maybe I'll just give it the finger like you guys suggested but could I ad one and if yes would it just go in line where the power lead hooks up to the motor.
 
No, you can not just add a capacitor, if the motor wasn't designed to use one. probably not what you want to hear. If you don't mind giving it a spin to start it, that will work just fine. It wouldn't be hidden, The capacitor would be a housing on the outside of the motor with a couple of screws to attach it.
 
No, you can not just add a capacitor, if the motor wasn't designed to use one. probably not what you want to hear. If you don't mind giving it a spin to start it, that will work just fine. It wouldn't be hidden, The capacitor would be a housing on the outside of the motor with a couple of screws to attach it.


darn. I had a feeling that would be the answer. Its actually way quieter than the craftsman sander I already had that supposedly works correctly and seems a little better built. I'll just keep it and do the capacitor duties by hand


thanks charles
 
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