weird grinding spindle
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  1. #1
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    Default weird grinding spindle

    im getting this small grinder operational and i wonder about the spindle. er16, around 15'000 rpm. its quiet, has no vibrations and is pretty stiff for its size, 0.01 mm up and down by hand pressure (0.0004"). however there is axial play of 1 mm (0.04"). when under power it gets pushed forward and doesnt seem to be rubbing, no idea if the belt/pulley does it or what. thre is no problem gringing with small stones (13 mm).

    so i have been thinking, maybe thats how its supposed to be? kind of insurance against breaking the stone in a hole? i cant think of a configuration that would still run well with that much wear. could it be designed that way?

    thoughts?
    Attached Thumbnails Attached Thumbnails 0-260.jpg   0-259.jpg  
    Last edited by dian; 03-20-2021 at 03:21 AM.

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    I don't think so. Perhaps something came loose or there is some wear somewhere. It shouldn't be flopping around like that.

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    Quote Originally Posted by dian View Post
    im getting this small grinder operational and i wonder about the spindle. er16, around 15'000 rpm. its quiet, has no vibrations and is pretty stiff for its size, 0.01 mm up and down by hand pressure (0.0004"). however there is axial play of 1 mm (0.04").
    That's not right. This looks like a Fischer or SFJ spindle. Are you sure that there are no (faded) markings on the body?

    A lot of spindle like this have a set of springs inside that preload the bearings. The bearings are intended to slide inside the body so that with thermal expansion they can move. If your spindle is designed that way, then the bearings are sticking in the body. So I would carefully open up the spindle and clean/lubricate it, checking that the bearings can move freely.

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    It sounds like the spindle was disassembled, and the spring washer not installed, or installed incorrectly. For sure not a normal thing to have, given the application.

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    so you figure this is an angular bearing spindle? there is no force needed to slide it back and forth. i cant measure any runout (<5µ). i was thinking mybe plain bearings with a thrust bearing missing? as i say, i runns well and sound good.


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