ah - now I get it
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  1. #1
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    Default ah - now I get it

    I have seen michiganbuck post several times that you should start a spindle by turning it on and then right back off a few times before you let it come fully up to speed. That didn't quite resonate with me until I saw this:



    Now I understand he must have come up in the plain bearing era. Makes sense to me now.

    metalmagpie

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    Quote Originally Posted by metalmagpie View Post
    I have seen michiganbuck post several times that you should start a spindle by turning it on and then right back off a few times before you let it come fully up to speed. That didn't quite resonate with me until I saw this:



    Now I understand he must have come up in the plain bearing era. Makes sense to me now.

    metalmagpie
    likely this thread to get busted for poor title..

    No. it is not just plain bearings, all bearings live better with a roll that comes from slower RPM , not a slide start..

  3. #3
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    When the grinder is at rest any coolant that is absorbed by the wheel tends to collect at the bottom of the wheel resulting in imbalance. Jogging the spindle a couple time throws the absorbed coolant out of the wheel. I suppose the need could be eliminated by turning off the coolant a while before the spindle was stopped.

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  5. #4
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    The main reason for jogging (or, in the case of VFD, to ramp slowly up to speed) is lubrication. Plain bearings need to have a proper film of oil to operate. If you spin the shaft too fast without re-establishing first such film, you get wear and damage.

    Ball and roller bearings are much more tolerant since each ball/cylinder traps some oil by capillarity and they have mostly rolling motion against the surface that has most friction.

    Paolo


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