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What bore diameter will fit a 5.4mm motor shaft?

  1. Jul 8, 2009 #1
    Hi gurus,

    I was hoping you guys can help me with a little something:

    I have just purchased a 12V DC motor with a shaft diameter of 5.4mm
    (Oddly enough, the description on the ebay page says 5.5mm, but the technical drawing
    attached, says that its 5.4mm).

    In any case - i am looking for a gear that i can attach onto this motor. However, all the gears out there have their measurements in imperial.

    My question is: What bore diameter should i be looking for to attach to my motor, that has a 5.4 - 5.5mm shaft? 3/8" seems slightly too big, and 5/16" seems a little too large.

    Any suggestions?
    (Sorry if this seems like a silly question)

  2. jcsd
  3. Jul 8, 2009 #2


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    Gold Member

    5.4 mm is less than 1/4", so both of those are too big. If you can, you might get a gear with a smaller bore diameter and ream it out a bit.
  4. Jul 8, 2009 #3
    I am attaching a drill size index for metric, English, and number sizes.
    Apparently the 5.4 mm diameter is nearly exactly a #3 drill, and there is no equivalent to 5.5 mm diameter, but is used for a M6 x 0.5 Fine thread.
  5. Jul 8, 2009 #4
    Just checking:

    Are you suggesting that i get a gear with a bore diameter SMALLER than my 5.4mm,
    and then use a number 3 drill to ream out the extra bit in the inside?

    Thanks turbo and bob.
  6. Jul 8, 2009 #5
    My SDP catalog (http://www.sdp-si.com/) lists gears with 5.5mm bore. My guess is your shaft is actually 5.5mm -- but measuring is always better than guessing!
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