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Thread: Setting up 6202 bearings

  1. #1
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    Question Setting up 6202 bearings

    Trying to rebuild a spindle for an old toolpost grinder and I don’t know how to set up the preload on the bearings. They are SKF 6202 2ZJEM shielded ball bearings for a 15mm shaft and a 35 mm bore. The bearings fit in each end of a tube about 8 inches long. I will turn shoulders on the new shaft for the inner races to stop against. For simplicity I’d like to use Belleville disk springs to take out the end play. McMaster’s sells them specifically for this bearing. Any information would be appreciated.

  2. #2
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    Don't know what kind of TPG it is but the 62xx series is probably the wrong bearing. These aren't meant to have an axial preload. If you do they'll probably self destruct in short order. You should use angular contact bearings. Off hand, I think they're the 72xx series but I'd have to check to be sure. Besides that, the spring washers are not for preload they're used to fill space. If you try to grind with an axial load, the spring will most likely move and cause grinding chatter--Just before the bearing blows apart.

  3. #3
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    Belleville springs are OFTEN used for preload. I have done it with perfect success. Logan 10" (later types) use them for preload, and that has been working for 50 years now.........

    I don't think there is any problem with them chattering. The usual procedure is to preload with a significant pressure.

    While angular contact are most common, it is also possible to use deep groove type with some anti-chatter preload. My Dumore 2" TPG uses a coil spring inside one pulley to provide preload on a pair of deep groove bearings to avoid chatter. The Dumore is not exactly a "farm-built" device.......

  4. #4
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    Who was the tool post grinder made by? I have an old Tom Thumb #11, made by Dumore, it looks like new, and I believe a parts break down for it. Let me know if you want a copy and I will dig it out. Jay
    "Just build it and be done"

  5. #5
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    I also doubt those are the correct bearings... Someone has put them in as replacements because they "fit".

    If you want to continne down that path (with non-precision bearings), you can axially load them like you suggest, but... you would be better off with 2MM202WI DUL pairs (or something similar..) These are preground for the correct preload at flush mounting - just clamp them togther at each end of a precision ground shaft with equally precise spacer or shoulders.
    Last edited by lakeside53; 07-10-2008 at 09:09 PM.

  6. #6
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    Since when does a Logan spin at 36,000rpm?

  7. #7
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    Here is what you need to calculate your preload.From the SKF website-

    Specs for the bearing you have selected inculding static and dynamic loads in both axial and radial.

    http://www.skf.com/skf/productcatalo...did=1050070202

    Now the page with the formula and recomended factors from SKF-

    http://www.skf.com/portal/skf/home/p...newlink=1_1_13


    You should be able to figure your preload from that.
    I just need one more tool,just one!

  8. #8
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    Ops. Sorry. I thought you were talking about 62xx bearings in a Logan. Belleville "washers" are too stiff to use as preload on something like this. How do you set them? I guess I'm on a different page tonight. There's usually a spring spacer washer in grinders but it's used to indicate when preload is set by it's near full compression.

    The tri-flanged piece in the photo below is a spring washer. (Lower left center) The threaded bushing to the right of it is the preload adjuster.


  9. #9
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    CCW, that looks like a Dumore grinder, but if so it is an interesting hybrid...... The oil cup is like mine (which has the "tube sock" oiler wick), but the rest looks like a MUCH newer one.

    Oh, and Belleville springs have pressures depending on the thickness and angle..... They are available down into the low "pounds" of pressure. For VERY weak pressures, the cutaway as you show is used.

  10. #10
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    Newer? LOL...Could be. It's a Model 44. An OLD Model 44. It's just been "dolled up" a little.


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