Ballscrew - Increasing Ball Size


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Thread: Ballscrew - Increasing Ball Size

  1. #1
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    Default Ballscrew - Increasing Ball Size

    I have a THK 3210B ballscrew off a turret mill X-axis in pieces for cleaning.
    The balls are 6.365 mm (as measured with a precision DTI on a test stand calibrated against precision blocks) and pitted, so need replacing.

    After cleaning, with the screw vertical and lubricated with ISO 68, the nut will rotate by gravity end-to-end.
    This amount of free running seems excessive.
    I have seen videos that demonstrate the nut stopping in a couple of revolutions after a manual spin initiation.

    I did a trial load of 6.35 mm balls (1/4"), the nut drops under gravity when dry.

    What size then should I purchase ?
    I am in Sydney and 110 balls of 6.370 mm from a reputable supplier in the US will be about AUD 200, a significant amount.

    Can anyone comment on the effect of increasing ball diameter by 5 micron ?
    Should the increase be less ? or more ?

    John

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  2. #2
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    Default Re: Ballscrew - Increasing Ball Size

    Did a test with the nut clamped horizontally in the vise with approx 500 mm of the screw on either side.
    A DTI shows the screw has +/- 50 micron vertical looseness at the ends.

    This possibly indicates that an additional 5 micron in ball diameter would reduce the vertical looseness to zero.

    Still looking for comments from others as to the effect of changing ball size.
    John.



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