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Thread: Bearing spin

  1. #1
    Join Date
    Nov 2012
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    Default Bearing spin

    My mini lathe's aluminium multi step pulley has two large (47mm) bearings in its hub.
    I am replacing them right now. The bearing are a fairly neat fit but both bearing outers will spin inside the hub if I try them with my fingers.
    What's the correct procedure here ? A smear of Loctite ? I have some of the blue Loctite.


  2. #2
    Join Date
    Oct 2011
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    Norwood-ish, Adelaide
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    Default

    Loctite and others make a product called bearing locker (or similar). I think the loctite number is 684. Much better stuff to use.

    Michael

  3. #3
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    Is there any damage to the bearing surfaces?
    If the outer races are spinning on their machined surface of the housing maybe that is the way it was intended, might pay you to measure before attempting to fix them in place.

  4. #4
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    Quote Originally Posted by pipeclay View Post
    Is there any damage to the bearing surfaces?
    If the outer races are spinning on their machined surface of the housing maybe that is the way it was intended, might pay you to measure before attempting to fix them in place.

    No actual damage as such like galling or scoring, just smooth where the outer sits.
    But why would they design it that way ? Allowing it to spin would wear out the housing. I'm assuming of course that at some time in its life the bearings jammed and spun in the housing.

    These bearings are open type so I will have to grease them.
    I don't have any proper internal measuring tools by the way. Only verniers. Must get some one day, it's on the list.

    PS Come to think of it....See the photo? there's a spacer between the bearings. Well the hub with the bearings on just slides all the way in quite easily, not a press fit at all. If the place where the bearings sit inside the pulley is worn then the space between would be tight, right, but it isn't. So I think you might be right, that it's the way it's intended (prob for easy removal to grease it) and I should just go ahead and fit it like it is.

  5. #5
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    I went ahead and fitted it all together with grease. Putting a thin smear of the grease inside the pulley housing appeared to tighten up the bearing outer enough to prob prevent slippage.
    I'm quite surprised at the brand new SKF bearings I put in it. They're really noisy.

  6. #6
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    Hi Phaser,

    You might find that the bearings should be oiled rather than greased. Grease will have a tendency to cause the bearing to spin in the housing simply because its is much thicker than oil. Also belt tension and the friction it causes against the bearing outer will tend to stop it skidding.
    Best Regards:
    Baron J.

  7. #7
    Join Date
    Oct 2008
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    Cairns, Q
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    Have a look here:
    Shaft & Housing Fits | NTN Bearing
    for information on ball bearing fits, particularly paragraphs 3 and 4. It seems likely that your bearing fits were designed that way.

    Frank.

  8. #8
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    I used a general purpose grease which is not a heavy type.
    It seems to be running fairly good. I'm just keeping an eye on temps when I use it to gauge what's going on.
    The same for the headstock cos I thought it was a little tight so I backed off the bearings a little. It looks to cut ok so the bearings aren't too loose, I might have set it just right I hope.

    In the process of making a steel stand for it now.

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