Question about Bosch 12" Dual - Bevel Compound Miter Saw with Upfront Controls and Laser Tracking 4212L

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Miter saw motor slowing down

Brushes are about 5/8 long, however the motor will not go to full speed, it seems like 1/2 speed. there is a pretty good arc coming from the brushes. The brushes do not seem to be wearing any, and there is no burn or hot smell coming from the motor even after continued use.

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  • Anonymous Mar 22, 2014

    New brushes still arcing


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Motor comm might be a problem.see if tha armature comm are fine.if their is gap with comm bar & discolorization with mains needs aramture etc.

Posted on Jun 01, 2008

  •  David Rogers
    David Rogers Jun 09, 2012

    All mains powered tools will tend to spark a little, even when new, it's a feature of the power passing between the brushes and commutator. However, if the sparking is significantly increased then it's likely that it's a sign of wear in the brushes, or worse, burning of the commutator. It'll need to be taken apart and inspected. New brushes might restore it a bit, or it might need a new armature as well. Often it's as cheap to replace the unit as to attempt to overhaul it! Good luck!


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Blade for sure are very dull

Posted on May 29, 2008

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