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  1. #1
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    Mar 2015
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    83

    TBI ballscrews

    ive been trying research this but i cannot find anything but could someone please tell me what the difference is between different TBI series ballscrews?

    there is

    SFA
    SFU
    SFNU

    bst at aliexpress says they sell close to sfnu but also sell sfu. just making sure there is no measurement difference for my cad drawing.

    thank you

  2. #2
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    Nov 2013
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    1343

    Re: TBI ballscrews

    Hi,
    there should be an accuracy grade mentioned in the advertising material.

    C7- is the most common rolled ballscrew grade, 50um over 300mm and 35um cyclic error.
    There are T grades, T for transport and are not good enough for CNC, likewise there are P grades, P for positioning, but again not really good enough for CNC.

    Then there are C5, C3...through C0 grades. C5 is the entry level ground screw grade, 18um per 300mm, 7 um cyclic error. A big improvement over C7, but a HUGE price
    increase.

    If you paid $150 for a 20mm C7 rolled screw with bearing blocks , expect to pay $1500 for the same size C5 ground grade....yes that's right about TEN times the price.
    C3 grade is for top end CNC machines and more expensive than C5s. C1 and C0 are for CMM's and semiconductor equipment. C1 and C0 are special order from the factory
    and I have no idea how much they cost, tens of thousands would be my guess.

    I bought three 32mm BNFN (double nut) THK C5 ballscrews second hand for my new mill. I can't afford new C5s but good second hand C5s are about the same price as new C7s.

    Craig

  3. #3
    Registered
    Join Date
    Jan 2016
    Posts
    76

    Re: TBI ballscrews

    Quote Originally Posted by reefy86 View Post
    ive been trying research this but i cannot find anything but could someone please tell me what the difference is between different TBI series ballscrews?

    there is

    SFA
    SFU
    SFNU

    bst at aliexpress says they sell close to sfnu but also sell sfu. just making sure there is no measurement difference for my cad drawing.

    thank you

    From my recollection the differences are only in the ball nuts, not the screws themselves. SFA = end cap recirculation type. SFU and SFNU are internal recirculating type. SFA would be used in high speed motion applications. SFU and SFNU are more suited to typical machine applications for most CNCZone uses. Any reason you're avoiding the double nuts (DFU, DFI, DFM for example)? Also TBI has a 98 page PDF on their site that details all you need about the various screw and nut types, see link below. Overall, TBI makes good screws. You'll most likely be fine with what you spec. I use ground C5 rated DFU screws and they are great. Zero regrets in spending the money on them.

    See page C36 in the link below for a breakdown what each letter means. Again, SFU or SFNU are what you want, unless you choose to pivot to a double nut.

    https://www.tbimotion.com.tw/Templat...EN).pdf?lng=en

  4. #4
    Registered
    Join Date
    Mar 2015
    Posts
    83

    Re: TBI ballscrews

    thanks for the reply

    i understand the difference between grades but i wanted to know if there was any difference between sfa sfu and sfnu other then just the name?

    for example i don't want to have the sfa model in my cad drawing and have all my plates milled for the ballnut housing and then i buy the sfu or sfnu ballscrew and the ballnut bracket doesnt align up with my milled plates if this makes sense?

    basically regardless of the tbi range if i get 1605 ball screw will they all have the exact same dimensions?

    Thanks

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