1. #1
    Hi I have a champion 20v mill from chester machine tools. Its obsolete now I think. ANyway it started making that popping sound indicating a brush problem. It tripped my house ELCB twice! I took it apart and indeed found the brushes slightly worn. Problem is I'm finding it hard to find replacements. They measure 3.35mm x 9.9mm. It seesm the standard size is 10mm x 6mm.

    I stripped down the motor and cleaned all the carbon off the commutator with 2000 grade emery. It was black with carbon. The brushes do seem to have a good bit of length left shortest is approx 10mm long. Maybe I don't even need to replace the brushes yet?

    Anyway just wondering if anyone came across a similar issue and how you dealt with it. I guess I'll put it back together tomorrow and see it cleaning the commutator solves the problem. I guess in the long term I should probably look at replacing the motor with a belt driven 3 phase motor, but thats another days expense. Too much money spent on tools of late. Wait till the wife finds out!


  2. #2
    Dave, have you looked at the WARCO, Amadeal, Grizzly and other Chinese made mills as I'm sure that they all come out of the same factory? I bet one is similar to yours and will use the same motor.

    Build log...here

  3. The Following User Says Thank You to njhussey For This Useful Post:

  4. #3
    Provided you can find brushes of a similar hardness and compound it's entirely acceptable to file or machine oversize brushes down to your required size,

  5. The Following User Says Thank You to magicniner For This Useful Post:

  6. #4
    Thanks guys. Yes I had thought of filing down a larger size, glad to hear that this is a viable option. I want to go back over the commutator with a soft brush to make sure there I'd absolutely no debris between the segments. And then I'll fire it up again.

  7. #5
    Good news to report on this. Cleaning the commutator did the trick. No more popping and tripping even at full load. I will still need new brushes shortly but at least I now have the time to research and maybe even replace the motor with something better.

    After doing the first clean up with emery paper, I read that using emery is not such a great idea since the particles can get between the segments and cause shorts. However I thoroughly cleaned between the segments with a soft brush on a dremel and in fact the gap between the segments is big enough easily see any major debris. Just mentioning this in case someone is reading this thread with the same problem.

    I actually now think the major issue was carbon build up between the segments.

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