BT3000 15A Motor Brushes..

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  • mmcmac
    Forum Newbie
    • Nov 2014
    • 53

    BT3000 15A Motor Brushes..

    Has anyone measured the carbon head of a new brush, presumably during replacement? The cross section measures 7mm x 17mm and the worn length of those in my restored motor is about 14mm. I believe the original length to have been somewhere in the 17~19mm ballpark. I expected I'd need to turn down the commutator to true it up however it has zero detectable wear. Even the brushes don't really need to be replaced but at $1.50 a pair that as well is an inexpensive clock to reset.
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    Last edited by mmcmac; 12-19-2014, 07:14 AM. Reason: clarity
  • mmcmac
    Forum Newbie
    • Nov 2014
    • 53

    #2
    Originally posted by I saw that!
    Having only the 13A motor, I can't be much help here, but I've been wondering about these specs as well.
    I found there is a bit more variation in commercial carbon brushes than I'd realized. The generic brush footprint used in the 15A bt3000 motor appears to be called out as any of 999044 / 99044 / 044 type brush. This dimensionally is a 7mm thick, 17mm wide, and 17 to 19mm long graphite block with a 23 to 24mm long copper braid shunt ~2.1mm in diameter (12 AWG) with a 16mm brass terminal. The generic brushes are for the most part dimensionally similar but have a 1.0mm (18AWG) shunt and the resistance of the graphite composition in one of my measurements is about 5x that of the OEM Ryobi brush. Although the effective resistance between commutator and brush in practice is complex as explained in this reference, it does indicate a significant material difference.

    Sweet deal on your brushes, btw. I haven't seen new OEM's (4540007) for less than $5 each.
    If you can find a bona fide mechanical and electrical equvalent 15A motor brush set for $10, I'd recommend doing so vs. my experimentation with random generic so called equivalents. Estimating from my bt3000s the life of the brush set exceeds that of the motor bearings by a factor of 2~3x. So I wouldn't chance having a cheap brush overheat the commutator causing it to centrifugally disintegrate.
    Last edited by mmcmac; 01-01-2015, 08:17 AM. Reason: correct typos

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    • mmcmac
      Forum Newbie
      • Nov 2014
      • 53

      #3
      Originally posted by mmcmac
      If you can find a bona fide mechanical and electrical equvalent 15A motor brush set for $10, I'd recommend doing so vs. my experimentation with random generic so called equivalents.
      Search for Hitachi 999-044 brushes, either those sold under Hitachi's name or from a named manufacturer with published product data. 999-044 brushes are used in a variety of Hitachi tools including 15A saws and electric jack hammers.

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