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  1. #1
    (As per the title, the bloke doing the work is Chinese, so I need to keep the instructions simple ...

    I need some sfu1204 machined & need the resulting ends to be a tight fit when inserted into a bearing with an 8mm ID / bore.

    But what would a tight fit be? 7.99mm? (because obviously 8mm machined ends will not fit into a bearing with an 8mm ID)

  2. #2
    Tippically they just request a drawing to work from so you just send them that.

    Attached is one I sent recently and the machining was spot on, modify it to match what you need if you want.

    .MeClick image for larger version. 

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    .Me

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  4. #3
    Thanks Lee...I'm just a little worried that the guy on the lathe takes any such measurement literally ...so if I tell him the ends are 8mm, then there's a possibility that they won't fit through an 8.0mm ID bearing (becuase obviously, 8mm ends wont fit into an 8mm bore...the ends need to be a miniscule shade less)

  5. #4
    If you want to specify tolerances then ask for the shaft to be machined 8mm g6 (should be within range of 7.986mm to 7.995mm) which should give you a sliding fit dependant on the bearing's dimensions...if you want a tight(er) fit then go for h7 (range of 7.991mm to 8mm) but you may have to press the shaft into the bearing (or run a bit of emery paper on the shaft till it fits...) if it's at it's upper tolerance of 8mm (range of 7.991mm to 8mm) and the bearing is also 8mm!
    Last edited by njhussey; 28-04-2016 at 05:01 PM.
    Neil...

    Build log...here

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  7. #5
    Quote Originally Posted by HankMcSpank View Post
    Thanks Lee...I'm just a little worried that the guy on the lathe takes any such measurement literally ...so if I tell him the ends are 8mm, then there's a possibility that they won't fit through an 8.0mm ID bearing (becuase obviously, 8mm ends wont fit into an 8mm bore...the ends need to be a miniscule shade less)
    Well yes unless he's got the bearings in hand for a piston fit he can only do his best, if it was me I'd ask for 8mm OD and as Neil suggests you then tweak the fit yourself with some fine wet and dry or emery paper.

    As I say I had to do this on my Z leadscrew but it was from another source, if you can spin the screws it's quite easy to do and won't take much, my other two screws fit sweet on the AC bearings and all I asked for was 12mm OD.

    Edit: Just to add, these guys do this all day long, so they know what their doing and have a good idea what the blank is going to, your gonna need to speak to them really for reassurance otherwise.

    .Me
    Last edited by Lee Roberts; 29-04-2016 at 09:19 AM.
    .Me

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  9. #6
    Thanks guys - really helpful.

  10. #7
    fifa's Avatar
    Lives in bristol, United Kingdom. Last Activity: 2 Weeks Ago Has been a member for 0-1 years. Has a total post count of 31. Received thanks 2 times, giving thanks to others 0 times.
    For fixed side shaft k6 (interference fit)

    for "sliding" side f6 or g7 (gap fit)

    Bearing hole shall be H4

    regards

  11. #8
    Quote Originally Posted by fifa View Post
    For fixed side shaft k6 (interference fit)

    for "sliding" side f6 or g7 (gap fit)

    Bearing hole shall be H4

    regards
    You keep reviving threads that are a year old or more??

    Sent from my HUAWEI VNS-L31 using Tapatalk
    Neil...

    Build log...here

  12. #9
    Fifa,

    what company do you represent?
    https://emvioeng.com
    Machine tools and 3D printing supplies. Expanding constantly.

  13. #10
    I would just tell the guy that I wanted the end machining to fit an 8mm bearing, I`m sure he will have done hundreds before so will know how tight/loose to make it.

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