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Thread: 20 mm ID bearing on a 3/4" shaft

  1. #1
    Join Date
    May 2005
    Location
    Northern MN
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    389

    20 mm ID bearing on a 3/4" shaft

    Not sure how far off topic I'm allowed to go -- this isn't technically woodworking, but it seemed like the right crowd for the question, and it could apply to DIY WW machinery. Admin's please delete if I'm straying too far.

    I have a 1940's vintage hay bale elevator that uses bearings that have a curved outer race, held trapped between two sheet metal flanges. The shaft is 3/4", OD is 1.850". Sam Mulkey Co was the manufacturer, long gone. Just had a bearing go bad and found a replacement of the same size (John Deere part JD9217), but was a lot easier to find a 20 mm ID by 47 mm OD replacement. Since imperial bearings are getting harder to find (seems to me), wondering if there was a way to shim a 0.750" shaft out to 20 mm (0.7874"). I did some searching on the net and couldn't turn up anything. This is not a high speed application, this shaft is reduced twice from a 1725 rpm motor, probably turning around 150-200 rpm.

    Thanks for any pointers.

    Best,

    Dave in northern MN

  2. #2
    Join Date
    Apr 2017
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    Tucson, Arizona
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    Hi Dave,

    Here is the exact bearing that you have specified below. I have not experienced any shortage of SAE ("Imperial") bearings. I would personally use the correct fit bearing for the application before I resorted to trying to shim a metric bearing to fit your 3/4" shaft.

    David


    https://www.amazon.com/John-Deere-Or.../dp/B079Z957BX


    John Deere JD9217.jpg

  3. #3
    Visit "The Big Bearing Store's" web site. They will almost surely have what you are looking for. Fastnal may also have your bearing. VBX is another source.

  4. #4
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    Quote Originally Posted by Bruce Wrenn View Post
    Visit "The Big Bearing Store's" web site. They will almost surely have what you are looking for. Fastnal may also have your bearing. VBX is another source.
    Yes - Google is your friend!!

  5. #5
    Join Date
    Oct 2006
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    Manistique, Michigan
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    Normally, the race of the bearing that is spinning should be a tight fit and the race of the bearing that is stationary should be a loose fit. We are talking in the 0.0001” to 0.001” range. So, 20 mm is way too loose on a 3/4” shaft. I agree that you have to stay with a 3/4 bore bearing or get a shaft made for a 20 mm bearing.

  6. #6
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    Quote Originally Posted by Rich Aldrich View Post
    Normally, the race of the bearing that is spinning should be a tight fit and the race of the bearing that is stationary should be a loose fit. We are talking in the 0.0001” to 0.001” range. So, 20 mm is way too loose on a 3/4” shaft. I agree that you have to stay with a 3/4 bore bearing or get a shaft made for a 20 mm bearing.
    Your are exactly correct Rich. A shim would be a bad idea for this application The correct bearing is readily available for a nominal cost.
    David

  7. #7
    Join Date
    May 2005
    Location
    Northern MN
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    389
    Thanks all. I had already found the bearing at Shoup. My question was more thinking ahead, as imperial sizes become harder to find, but legacy equipment persists. And to be clear, I wasn't proposing that I just put a 20 mm bearing on a 3/4" shaft as is, I was wondering if there are bushings that can be slipped over a 3/4" shaft to bring it to 20 mm.

    Best,

    Dave

  8. #8
    Join Date
    Mar 2019
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    Greeley, CO
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    I doubt imperial sized bearings will go away but if you're convinced it's a issue it'll be much cheaper and better to buy a small stash now a save them for future use. Making a thin shim is a fool's errand.

  9. #9
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    Quote Originally Posted by Eric Danstrom View Post
    I doubt imperial sized bearings will go away but if you're convinced it's a issue it'll be much cheaper and better to buy a small stash now a save them for future use. Making a thin shim is a fool's errand.
    Very Well Said!!!

  10. #10
    Join Date
    Sep 2016
    Location
    Modesto, CA, USA
    Posts
    9,885
    You can buy shim stock in many thicknesses. They make sleeves to repair a shaft that got grooved by a lip seal. But you have to turn down the shaft a to fit the inner bore. My 1973 Volvo had provisson on the front shaft seal to mount the lip seal in three different depths at each engine rebuild. so it went in deeper each time to slip over the old grooves.
    Bill D

    https://www.skf.com/us/products/seal...eve/index.html

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