Electric Motor Help please.

[Patbretagne]

Not at all a Farmall subject but a general call to help about an electric motor I have on a fairly recent, square-cut-off saw for carpentry.

For about 4 years it has worked very very well, not used very much.

A few weeks ago, all of a sudden, rotary sparks started chasing each other around the commutator, so I stopped using it, partly dismantled the motor to remove the brushes.

Brushes as good as new, not lodging up and touching the commutator, the latter like new, cleaned with a little very fine paper, put together and the same situation exists.

Can anyone help me to diagnose the problem please?

Pat

[John *.?-!.* cub owner]

Pat, I am not a motor expert, but it sounds to me as if the armature in the motor has failed. Depending on the cost of the unit you have, it may be more reasonable to buy another saw than to fix that one. If the one you have is a discount unit of the type we see a lot of in the U.S., 2 to 4 years is about all the life you can expect.

[Charles (49) Mo]

If the brushes do not freely move in the holder it may cause arcing. Also, if the insulating mica between the armature copper segments are a bit too high, it causes the brushes to bounce and create arcs. Are the springs on the brushes ok?

[Bigdog]

If you have cleaned the commutator and it is not grooved or bridged then I agree with John - you probably have some windings that are shorted or starting to short out.

[Eugene]

Since this motor is on a saw. Try blowing the motor out with compressed air.

My opinion is the same as John's. It's sad that repair parts for many appliances cost as much as the appliance. It's also sad that a 4 or 5 year old appliance needs a $2.00 part and parts are no longer available. Or if the appliance is still under warranty, you have to ship the item to (pick a distant location) at your expense for service.

Eugene

[Rudi]

Pat:

This is not an electrical fix solution by anymeans. I have a Delta 10" Mitre or Chop Saw in my shop. I have had this saw since 1988. Always worked like a charm. A few of those rubber drive belts is all I have ever had to replace in it aside from one set of brushes a few years ago.

A few weeks ago, I was in the shop doing a few things. Needed to cut up some scrap that was hanging around, so I usually chop it up for kindling for the house furnace.

Anyways, sparks, racket like all get out..

1. I checked the drive belt
2. I checked the brushes
3. I checked the armature
4. I checked the arbor
5. I checked the blade
6. I checked the guard and everything.

I almost took it apart. Then it dawned on me... the arbor shaft was sliding. Quick check the lock nut by the drive belt. Hmm looks good. Take the drive belt off... ohoh.. how did that nut work itself loose

Give it a shot and see if that is the problem. If all the electrics are good, clean and not scored, burned or chaffed.. then it has to be the arbor. Check the nuts, and check the pillow blocks or bearing races.. it will be a small problem most likely that will be hard to spot.. but diligence will pay off in the end.

Let us know what you find out in any event....... hope it is something minor...