Sparking comutator

[oliver09]

Ive got two quite old but decent quality small angle grinders here(one Metabo, one Bosch)that I have put new brushes in but are both sparking quite violently at the comutator. Its actually several years ago that I put the brushes in so I can't exactly remember the history but I think the Metabo stopped because the wear springs popped out and I replaced those with correct brushes I had in stock. I think I then checked the Bosch to find that they too were worn and put some in that had come as spares with a "far eastern" grinder, they fit well in the carrier and the joining wires are soldered. I have susequently turned the Bosch comutator on a lathe which has made no difference. Any advice on action or things to check would much appreciated as it would be a shame to throw them away if its something simple. Thanks.

 

[Skogsgurra]

Those motors are so-called universal motors. They always spark. If violently or not is a matter of opinion.

Turning them on a lathe is not always commendable if you do not have the right tool (small angle) and run at a very high speed.

After turning, you have to remove the mica (could also be plastic) between the commutator bars. And grade the bar edges. But that is not something one does with these small machines. They are use and scrap items.

Gunnar Englund

http://www.gke.org

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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

 

[edison123]

In all probability, the armature winding is shot. Best to buy a new armature. That's what I do in my own "rewinding" shop.

Muthu

http://www.edison.co.in

 

[waross]

Agree with Muthu. A damaged armature usually causes excess sparking. Badly worn brushes often lead to armature damage.
Very often worn out brushes and a damaged commutator go hand in hand.
I agree with Gunnars advice also.
How to tell if the sparking is excessive? Poor performance is one indicator. Use the tool, if the sparking is really excessive, the armature will soon fail completely and remove all doubt.

Bill
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"Why not the best?"
Jimmy Carter

 

[ozsalty]

green spark may indicate an open circuit in the armature windings...a blue spark usually indicates a short circuit.