Accurately Measuring Balls (ahem.. for a bearing block)


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Thread: Accurately Measuring Balls (ahem.. for a bearing block)

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    Default Accurately Measuring Balls (ahem.. for a bearing block)

    Evening gents,

    I've got some THK HSR15's that I'm using for a build.. Only trouble is they're 0 preload blocks. I'm looking to repack the blocks with larger balls but can't figure out a good way to accurately measure the diameter of the current balls. Seems like I'd need to get down to the micron level (0.000039 inch) or at least one tenth. Also, my micrometer is only good to about 5 tenths best case and while I'd love to grab a Mitutoyo digital mic (which are accurate to a micron -0.001mm) I don't really have the funds.

    I've looked at setting up a LVDT system but I fear it may be the start of another really long project (which I am admittedly famous for) that gets me further from my initial goal.

    So question time: 1. Are there any documentation that specify the diameter of the balls in a THK HSR15 block (I've heard it was a trade secret but ya never know!)
    2. Assuming the response to question 1 is a no, is there a place ya'll are aware of where I could get a ball accurately measured so I can go about experimenting with . larger sizes and preload etc.

    And for anyone considering this here are a couple interesting reads regarding this exact problem: http://www.cnczone.com/forums/vertic...tormach-7.html
    http://www.cnczone.com/forums/vertic...05-cnc-20.html

    Will keep posting info as I discover it

    Cheers! Devin

    Similar Threads:
    Last edited by crazydiamond; 02-21-2016 at 10:07 PM. Reason: incorrect terminology


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    Default Re: Accurately Measuring Balls (ahem.. for a bearing block)

    I have done that ball replacing before. But instead of going through the expense of measuring the balls super-accurately, I just measured them with a caliper and then bought replacement balls one or two sizes larger. In my case they just seemed 0.125 balls, so I bought 0.1255 and 0.1260 balls. 0.1255 gave good preload. 0.1260 was to tight for my taste.

    I think you are overthinking it....

    P.s. I got the balls from this guy:
    toolsupply on eBay





    Quote Originally Posted by crazydiamond View Post
    Evening gents,

    I've got some THK HSR15's that I'm using for a build.. Only trouble is they're 0 preload blocks. I'm looking to repack the blocks with larger balls but can't figure out a good way to accurately measure the diameter of the current balls. Seems like I'd need to get down to the micron level (0.000039 inch) or at least one tenth. Also, my micrometer is only good to about 5 tenths best case and while I'd love to grab a Mitutoyo digital mic (which are accurate to a micron -0.001mm) I don't really have the funds.

    I've looked at setting up a LVDT system but I fear it may be the start of another really long project (which I am admittedly famous for) that gets me further from my initial goal.

    So question time: 1. Are there any documentation that specify the diameter of the balls in a THK HSR15 block (I've heard it was a trade secret but ya never know!)
    2. Assuming the response to question 1 is a no, is there a place ya'll are aware of where I could get a ball accurately measured so I can go about experimenting with . larger sizes and preload etc.

    And for anyone considering this here are a couple interesting reads regarding this exact problem: http://www.cnczone.com/forums/vertic...tormach-7.html
    http://www.cnczone.com/forums/vertic...05-cnc-20.html

    Will keep posting info as I discover it

    Cheers! Devin




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    Default Re: Accurately Measuring Balls (ahem.. for a bearing block)

    Std micrometers ARE NOT accurate to 1 um or one micron.

    The normal Mitutoyo specs is plus or minus 2 um, for up to 4 microns variation.

    But the nominal trending results are typically to approx 0 micron error, with +1 um occasionally.
    All this on normal smallish bits in steel under say 50 mm or 2", and in normal room temperatures.

    Measuring gage pins (3 sizes, 2 micron size differences) with my good-quality digital micrometers, errors tend towards zero, and all pins measure correctly.

    The cheapest digital ones, I tried 5, were all crap.
    The 35€ ones. The 60€ ones are good, at least some of them.



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    Default Re: Accurately Measuring Balls (ahem.. for a bearing block)

    Baltec - Home is another source for balls. They have the measuring equipment also.



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