How much tolerance for wheel bearing press fit?

Discussion in 'The Garage' started by TheRadBaron, Nov 19, 2012.

  1. TheRadBaron

    TheRadBaron Been here awhile

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    I have a rear hub from a Yamaha XT500 that I'm preparing to have some machining done. I need to machine the 40mm wheel bearing bores out to 42mm. What is the recommended interference fit for a wheel bearing? I'd like to have a definite diameter to tell the machinist.
    I know that I could get an idea by measuring the the hub that I have, but I'd rather hear the official number. I tried looking it up using machinist literature, but not being a machinist myself, it was like a foreign language.
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  2. anotherguy

    anotherguy Long timer

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    .001". Fit bearing with anti-seize.
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  3. LuciferMutt

    LuciferMutt Rides slow bike slow

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    That's way too heavy for a bearing and will likely to damage it. Try .0003-.0005" smaller than the bearing OD on the bore.
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  4. OldPete

    OldPete Be aware

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    .0005" to .0008" per inch of bearing diameter.

    Make sure the bore is clean before pre-heating it. Chill bearing in freezer.
    Install w/o hitting the inner race as this is a prime cause of short bearing life.
    I like drawing bearings in with a bit of all-thread.

    SKF and New Departure have specs.
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  5. machinebuilder

    machinebuilder Long timer

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  6. TheRadBaron

    TheRadBaron Been here awhile

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    Man, I opened that document and it's pretty esoteric stuff (to a non-machinist). I know that I could spend the time and get sufficient reference data that I could understand it, but I'd really rather not :norton.
    As far as the measurement that you gave me, am I correct in taking that as meaning that I should have 0.012" (12 thousandths) of interference? This seems excessive to me. Did you mean 0.0012"?
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  7. Tosh Togo

    Tosh Togo Long timer

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    Your "machinist" should already know about things like interference fits.... mine does. :D

    You might want to look until you find one (or a shop) that does. Whoever does machining work for your area's racers would be a good place to start. :1drink

    If that's not an option, call your local bearing supplier.
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  8. TheRadBaron

    TheRadBaron Been here awhile

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    I agree, but I'm not really taking the hub to a machinist in the conventional sense. My dad works in a machine shop that manufactures high-tech parts for the steel industry and he's going to have one of the machinists there turn it for me. I'm sure that the machinist that will do it is a skilled guy, but steel mill components and motorcycle wheels probably have enough differences in machining tolerances that I'd like to be able to ask for a specific clearance rather than leave it up to the machinist's judgement.
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  9. machinebuilder

    machinebuilder Long timer

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    Dimensions are in millimeters, 0.012mm = 0.00047"

    I work in mm all the time, and REALLY dislike mixed measuring systems

    There's a couple charts in the midst off all that info that give the tolerances
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  10. _cy_

    _cy_ Long timer

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    let the machine shop determine clearance. take actual bearing in along with hub. any reputable machine shop has done this before.
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  11. TheRadBaron

    TheRadBaron Been here awhile

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    Duh, I should have been able to figure that out. I was fixated on the "inch" system of measurement since that's the way it usually gets discussed. Thanks for the good info.
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  12. machinebuilder

    machinebuilder Long timer

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    Any time, I deal with similar stuff on machine tools daily, so to me what is common sense is more like rocket science to many.

    Besides the only really stupid question is the one not asked.:evil
    #12