Plain Bearing not taking Oil - Positive Pressure?
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  1. #1
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    Default Plain Bearing not taking Oil - Positive Pressure?

    I have been researching this topic without much luck. Probably due to not knowing the correct terminology to search for.

    I have noticed over the years several machines that seem to have oiling issues where the machine does not want to take oil. Most recently I rebuilt the spindle on my Abrasive surface grinder and noticed that it does not want to take oil.

    When the grinder is cold, looking at the spindle and cartridge face, without the hub, you can see the plain bearing and the spindle shaft. Around the shaft there is a bead of oil. As the spindle cartridge heats up, this bead of oil begins to disappear. As the spindle is running, when cold, the oiler will drip. As the spindle heats up, the oiler will stop dripping.

    Noticing this, I started playing around and experimenting. I found that once the spindle is heated up, around 90 degree's or above, the oiler will no longer drip oil. Even more startling, if I remove the oiler, and fill the passageway with oil, it does not consume any of the oil. If I turn the spindle off, as the spindle stops, the oil level will fall, draining the passage.

    Any thoughts on what is the cause of this? Any thoughts on how to remedy this issue?

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    Maybe there's nothing that needs remedying. If the rise is 90°F (assuming not °C), and there is no smoke and bad noise, then I don't see an issue. Are you making your observations under load? If not, try carefully putting on a side load in different directions (like with a thin well-oiled wooden slat), and see how the oil level responds in the fill hole. In a plain bearing, the loaded zone (oil wedge) will be self-pressurized. In the unloaded condition, the loaded zone could be anywhere around the circumference, and could align with the fill point, either preventing oil from getting in or actually pumping it out. Since yours is not pumping out apparently, the oil port is possibly on the edge of the load zone, which could be very broad in a close-fitting bearing.

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    Thank you for explaining a bit more about how the oiling works, another piece to the puzzle for me.

    My gut tells me it isn't right. At least not compared to the other machines of the same make that I have or have run in the past.

    To clarify a few details, 90 degrees F is the actual temperature of the spindle. Not the temperature rise. The temperature rise would be 20-25 degrees F. (My keyboard/computer won't let me make the degrees symbol for some reason)I have let the spindle get to 104, but the motor audibly sounded like it was starting to work harder. When I shut it off, there was a very noticeable squeak when the spindle came to a stop. I have not let it get that hot since out of fear of damaging the plain bearing. As it heats, the temperature rise seems to be a curve. This curve, seems to me is steepened by the lack of oil. But that is my uneducated guess.

    For comparison, my other grinder (same make/model) can run all day, and average 87 degrees, even when under load. Under heavy load I have seen it get to mid 90's.

    I will do some testing in regards to the oiling under load that you described.

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    The first thing I would check and compare with the other grinder is the bearing clearance. The squeak you report is concerning.

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    What would you recommend for this? How do you/would you check?

    I have a 3rd spindle apart, I will take a look at it this afternoon.

    The immediate issue I see is getting to the spindle and bearing to check clearance. When assembled, the bearing has a threaded collar that pulls the bearing forward against two tapered diameters.

    My understanding is that this allows for adjusting for wear, and also creates the oval? shape required for the wedge to form?

    As another reference, when reassembling the spindle, I tightened the nut to the same timing as when I took it apart. I may also try loosening the spindle nut to see if that has an effect on oiling.

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    I would to put a tenths indicator on the spindle as close as possible to the journal of interest, and push it up and down to see how much it moves. Is it a tapered journal? If so, you could use the tenths indicator to measure axial movement.

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    It's called a plan bearing as is a way bearing or even a ball bearing. In order to get "bearings" to last longer they need oil pockets. Your not telling us what weight oil your using. On "plain bearing the mfg. instructions are / were to have a warm up period so the heart could expand the bearing. I found this for you. Look at page 7 and 8 where it explains running it for 2 to 3 hours to warm up...ect...etc..http://vintagemachinery.org/pubs/2748/19761.pdf

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    A few points for reference.

    The rebuilt spindle that is getting hot gave me the following measurements. I used a .0005" indicator because... well a .0001" was too little!
    Cold, while running, I got .0025" when pushing up on the spindle.
    80 degrees F, I got .002" when pushing up on the spindle.
    99 degrees F, I got .001" when pushing up on the spindle.

    My other running grinder has a fair spindle, and I can get a decent grind on it with some care.
    Cold, while running, I got .0025" when pushing up on the spindle.
    86 degrees F, I got .0035" when pushing up on the spindle.

    I completely loosened the spindle box nut and while running, the spindle would consume a small amount of oil. When tightened to the mark from before disassembly, it would not take oil, with me pushing up, down, left, or right.

    Quote Originally Posted by rklopp View Post
    I would to put a tenths indicator on the spindle as close as possible to the journal of interest, and push it up and down to see how much it moves. Is it a tapered journal? If so, you could use the tenths indicator to measure axial movement.
    The bearing has two tapered diameters on the outside that mate to the cartridge, however the spindle itself will float slightly front to back. I guess it is designed this way.

    Quote Originally Posted by Richard King View Post
    It's called a plan bearing as is a way bearing or even a ball bearing. In order to get "bearings" to last longer they need oil pockets. Your not telling us what weight oil your using. On "plain bearing the mfg. instructions are / were to have a warm up period so the heart could expand the bearing. I found this for you. Look at page 7 and 8 where it explains running it for 2 to 3 hours to warm up...ect...etc..http://vintagemachinery.org/pubs/2748/19761.pdf
    I am using Velocite No 10. I have always used a similar warm up, on my grinders it says if they have sat for more than 24 hours, turn the spindle by hand, then run for 30 sec, shut off for 30 seconds several times before starting up. I usually give the spindle a few drops of oil, turn the wheel both directions a few revolutions, and then pulse on off as directed 2 or 3 times. Then it usually warms up for an hour before use and stays on all day.

    Thank you for referencing the 3B document though, I have never looked at that one, and found a nice nugget of information about the box liner, and how to grind it for adjustment.

    Richard I hope you are doing well? I am glad to hear you are still doing classes. If your ever passing through NE Ohio, feel free to look me up.

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    Quote Originally Posted by Fal Grunt View Post
    I am using Velocite No 10.
    Is that what the manufacturer recommends? My journal bearing machine (Studer cylindrical grinder) uses Velocite No 3 for the wheel spindle and Velocite No 6 for the workhead spindle. Velocite No 10 sounds heavier than I would have expected.

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    Quote Originally Posted by ballen View Post
    Is that what the manufacturer recommends? My journal bearing machine (Studer cylindrical grinder) uses Velocite No 3 for the wheel spindle and Velocite No 6 for the workhead spindle. Velocite No 10 sounds heavier than I would have expected.
    Point. At least one family of precision grinder spindles even used "white" kerosene, IIRC? No "lubricity" to it, but hydrodynamic effect still works.

    Can't get lube in, "very noticeable squeak when the spindle came to a stop", seems there is no SPACE for lube at the temp it had reached?

    And when did plain bearings start needing an "oval" shape to generate and sustain the hydrodynamic "wedge"?

    News to me. And I got one of the only two "A" and the only "A" on the final in the course that semester.
    Last edited by thermite; 03-25-2020 at 06:52 AM.

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    0.0025"
    Translated into metric that is more as 0.06mm
    You better put grease in it
    0.01mm was recommended by Aba IIRC
    And then the right oil Thinner as water
    In old documentation they indeed did recommend white kerosene mixed with a little oil

    Peter

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    Quote Originally Posted by Peter from Holland View Post
    0.0025"
    Translated into metric that is more as 0.06mm
    You better put grease in it
    0.01mm was recommended by Aba IIRC
    And then the right oil Thinner as water
    In old documentation they indeed did recommend white kerosene mixed with a little oil

    Peter
    Supposed to add a touch of two-stroke oil even if I run kerosene (AKA number one Diesel) in my Lister-Petter motored gen set. Wears-out the injector pump faster than number TWO Diesel otherwise.

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    Quote Originally Posted by ballen View Post
    Is that what the manufacturer recommends? My journal bearing machine (Studer cylindrical grinder) uses Velocite No 3 for the wheel spindle and Velocite No 6 for the workhead spindle. Velocite No 10 sounds heavier than I would have expected.
    The manufacturer recommends 100 seconds sayboldt at 100 degrees F.

    The Cincinnati and South Bend documentation I have both recommend Mobile Velocite No 10 as an acceptable oil for this rating.

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    Quote Originally Posted by Peter from Holland View Post
    0.0025"
    Translated into metric that is more as 0.06mm
    You better put grease in it
    0.01mm was recommended by Aba IIRC
    And then the right oil Thinner as water
    In old documentation they indeed did recommend white kerosene mixed with a little oil

    Peter
    Can you provide any more information on the spec provided by "Aba"?

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    I was looking for that dokumentation
    I cannot find it right now
    I have a further look

    Peter

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    Quote Originally Posted by Peter from Holland View Post
    I was looking for that dokumentation
    I cannot find it right now
    I have a further look

    Peter
    When convenient, I would appreciate it thank you.

    The information that Richard provided I found the following information which was very informative:
    "To adjust the spindle box for slight amount of wear, tighten nut "A". If ore adjustment is required remove box and grind box liner .001 thinner for each .0003" lift over .001". The lift can be determined with a dial indicator after washing box and spindle in gasoline, drying, and reassembling. After readjusting the lift should be .001 for average spindle oil and lot less than .0007 for extra light spindle oil. The ball bearings are super precision."

    To me, it sounds as though I would be testing the stripped spindle and box, not a running machine?

    I wonder if I have a high spot somewhere in the bearing that is rubbing, causing the heat. Possible that rubbing was not there before, as the old ball bearings wore and the spindle wore, it was not an issue. With new ball bearings it moved, probably with yours truly installing, enough that now it rubs?

    My next question is will be how the heck do I scrape this thing? I have a bearing scraper, in relatively good shape, but the process is what I am struggling with. I blued up my 3rd spindle, and slid it into the bearing box. I located it as close as I could front to back where it would ride, then tightened the spindle nut down. I slowly tightened the nut down until I just started to feel the spindle drag and rotated it by hand for 30 seconds or so. I then loosened the nut and removed the spindle. As you can imagine, the bluing wiped along the majority of the bearing, I can see a couple of rub spots, so possibly this would work on the spindle that is getting hot?

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    Quote Originally Posted by Fal Grunt View Post
    ..so possibly this would work on the spindle that is getting hot?
    Uhh?? "Cap'n Obvious" hat on. No one can know what is best until it is "the spindle that is getting hot" as has been blued.

    That "oval" part - tri-lobed, was it, actually? Been a while - sounds Bronze-bearing-era South-Bend lathe'ish, but I'm not a fan of it. The best examples of the SB tribe I ever had hands-on were all Iron-bearing ones.

    If you have more than one spindle, same design and nearly same size - maintenance now, plus going forward, and on the whole lot?

    It might justify fab'ing a bespoke adjustable lap with your "best efforts"?

    The late Texasturnado did that to lap a TS spindle. Overkill, it worked so well for him. But overkill is nice when you are running the machine for your own self.

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    With 0.06mm endplay one can assume the spindle needs a rebuild
    That involves grinding and lapping the spindle Then scrape the bearing
    On a Aba the OD of the plain bearing is tapered and has 3 ridges
    It can be pulled into the bore with a mecanism
    Those 3 ridges give 3 high spots when tightening it That results it 3 places where you get a pumping action of the oil
    So not oval but 3lobbed somewhat

    Peter

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    Quote Originally Posted by Peter from Holland View Post
    On a Aba the OD of the plain bearing is tapered and has 3 ridges
    It can be pulled into the bore with a mecanism
    Those 3 ridges give 3 high spots when tightening it That results it 3 places where you get a pumping action of the oil
    So not oval but 3lobbed somewhat

    Peter
    Interesting. "Sounds as if" what they are doing is two-fold:

    - Breaking-up the hydrodynamic wedge "geometry" into 3 sub-sections.

    Rationale would be that in perfectly-circular bearings, the "wedge" pushes the shaft to an offset from true center. That's fine for IC engines, but where a machine-tool is trying to HOLD to a predictable center at tighter clearances, you'd want to reduce the amount of excursion - already low for the clearances and lube used here, but still

    - Provide a limited zone of contact for "landing" as the pressure goes off and the shaft slows down and comes to rest, same again after being out of use and it is next powered-up.

    Eg: provision for a low-damage state of metal-to-metal contact, or risk-of such contact, depending on film characteristics of the lube when no longer under pressure, and on how long it has sat idle before next pressurized.

    Or "so it would seem."

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    3 high and 3 low areas is common to a professional who scrapes ID bearings. One must be a detective and note where they were from the factory. If it is now to late, you have to make the high area on the opposite side of the inward pressure of the wheel or belt pressure if the spindle is driven by belts. The leading edge of the high area's is tapered to let the oil wedge form and flow / pump into the gap or clearance after it is set. A simple example is a Cincinnati filmatic centerless grinder spindle. here is a great example on On the Abrasive grinder 3 low are'a scraped with a 1/4 spoon scraper should be fine....

    Here are some picture to look at unless you read French or Swiss.

    swiss-french-scraping-6.-t_scan_6_7_2009_21h5m26s_3_956.jpgswiss-french-scraping-7.-t_scan_6_7_2009_21h5m26s_4_213.jpgswiss-french-scraping-3.-ggrrraaa.jpg

    Page 6 -http://vintagemachinery.org/pubs/10764/19831.pdf


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