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How much grease in a ball bearing?

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  • How much grease in a ball bearing?

    If you carefully pick off the seal on a ball bearing, you'll be surprised at how little grease there is in there. A friend says this is not enough, and the makers are just trying to save money. But at some point, you can have too much grease in a bearing. It would seem to me that all you need is enough to flow between the balls and the races. So the question is: is the small amount put in there at the factory enough? If not, how much more should there be?

  • #2
    Sometimes it's quality, not quantity...

    Are you experiencing any problems with the bearings?
    Are they made in the U.S. or Asia?
    Granted, Manufacturers will usually do what they can to trim costs, but mostly they would rather use exactly enough of the proper lubricant instead of gaining a bad rap in the marketplace for poor quality or service life...
    It would also depend on what the bearing is designed for, High Speed operation, Heavy loads, and Harsh environments all fator in to the amount and type of lube used in the bearing...

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    • #3
      Grease In A Bearing

      Greg, I attended a training session on bearings a couple of years ago and they told us even though it looks like they don't have very much grease in them, it is sufficient under normal conditions. He also told us that adding very much more grease will cause more resistance and heat, which will shorten the life of the bearing. Just my .02.
      Gary

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      • #4
        Rules of thumb for fresh grease pack in precision ball bearing.

        #1 Carefully filtered intended for ball bearing service.
        #2 Pack no more than 1/3 the volume between races.
        #3 Evenly distributed before bearing goes into real service.

        The object is to get the grease spread all round and formed into a channel before you get it all hot and bothered.

        For farm duty - - grease is the way crud is kept out.
        Those bearings are often fully filled to flush dust out, as too much grease is preferable to too much dust.

        Hth Ag

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        • #5
          I recently read about how grease is supposed to work in sealed ball bearings and it doesn't work the way I expected.

          Apparently, relatively little grease is needed - the grease should be pushed off the ball tracks in the first couple of revolutions. Thereafter, oil slowly oozes out of the grease and this miniscule amount of oil is sufficient to lubricate the bearings for life in a sealed bearing. If too much grease is used there isn't enough room for it to get pushed out of the way so the bearing churns the grease and generates heat; excess grease is a problem rather than a help.

          John
          Location: Newtown, CT USA

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          • #6
            I wish I had said that
            Ag

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            • #7
              Manuals

              Why not use the manufacturers manuals for design, installation and maintenance?

              We are not talking about grease for horse-drawn (covered and other) wagons here.

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              • #8
                Unless the bearing's overloaded, yeah, it's only slightly more than dry.

                In an overload situation, you 'can' use grease as a coolant, but
                that's a real bandaid. Better is to then switch to oil, as the stock car
                guys are starting to do.

                t
                rusting in Seattle

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                • #9
                  Gadget's right.

                  What needs lubed?

                  Not the rolling balls, they roll, they don't want to skid or slide.

                  It's the balls against the cage that need the lube, primarily, and there is really no substantial pressure there, at least theoretically. So there needs to be only enough lube in a sealed bearing to lubricate the light pressure of the balls against their cage, and keep doing it for the expected number of revolutions.

                  The total revolutions depends on load, since failure is when the race or balls start to spall off pieces due to metal fatigue. They have to figure that some applications will be lighter loads and last longer, demanding a longer lasting grease.
                  1601

                  Keep eye on ball.
                  Hashim Khan

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                  • #10
                    Getcha bearings

                    Again JT, I agree with you entirely.

                    You obviously have read and digested the very good information in manufacturers manuals and catalogues etc.

                    This paragraph of yours:
                    The total revolutions depends on load, since failure is when the race or balls start to spall off pieces due to metal fatigue. They have to figure that some applications will be lighter loads and last longer, demanding a longer lasting grease.
                    cannot be over-stated.

                    The bearings in original equipment were or perhaps should have been selected for a "full-on" industrial loading and environment where long life is a very cost-effective justification for what some HSM-ers may regard as very expensive bearings.

                    If the HSM-er really has close look at his real requirements and expectations and uses the bearing manufacturers selection criteria to advantage, he will quite probably get a very serviceable bearing for his expected loads and times at a very much cheaper cost but just as effective as the more expensive "replace old for new" bearing/s.

                    As a matter of practice, I replace old bearings with new - always on important stuff and only very occasionally otherwise. Bearings are pretty cheap mostly.

                    To get the very best out of a bearing, it is MOST important that it be installed - and where, when and if necessary, lubricated - strictly in accordance with the manufacturers instructions.

                    There is only one thing worse than having to change or remove/replace bearings once and that is having to do it again!!

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                    • #11
                      Bearing application dictates bearing lube. My lawn tractor will go forever with Lithium in the wheel bearings. I greased many aircraft wheel bearings and there are specifics on type and amount of grease. The saying one size fits all doesn't apply to bearings.

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                      • #12
                        Indeed, grease is a base oil plus a thickner...these can be synthetic (both the oil and the thickener) or a petroleum oil with a lithium soap or clay thickener (plus some others). The base oil has some viscosity that is appropriate as the job is done and the thickeners also are available in varius NLGI "thicknesses". We tend to think of using an NLGI grade 2 grease (common thickness for automotive chassis grease) as defining the grease, but really the thickness of the base oil is also important. The notion that "grease is grease" is nonsense. For many applications (automotive chassis fittings comes to mind), its somewhat less critical.

                        Motor or spindle bearings are much more critical because you are trying to use a lubricant in a thick base to lubricate something that moves much faster and repetitively than say a ball joint. As such, its important to use a lubricant with the appropriate viscosity of the base oil as well as the soap thickener.

                        Since grease does work by releasing its base oil for lubrication, as its worked, its important to use the right stuff for the job and not treat the thickness of the compound as a measure of the thickness of the lubricating oil it contains. Often the operating environment effects the needed thickness for the thickener so that heat does not allow the oil to separate too easily. Likewise, if its too thick in a cold environment, it will not move as it should and creates inefficiency. One of the up-sides to synthetics is that their base oils and thickeners are not as badly effected by cold temps and they are less apt to go from the right viscosity to "molasses in January" consistency.

                        As was already stated, too much grease in a medium or high speed bearing creates heat. Heat means expansion of the componenets, a change in their fit and eventually brinnelling of the balls and races etc. In a machine spindle, for example, there may not be a good way to radiate this heat as with say an automotive spindle with air flow and a brake drum or rotor. In short, if some is good, more is not necessarily better.

                        Paul
                        Paul Carpenter
                        Mapleton, IL

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                        • #13
                          Originally posted by agrip
                          Rules of thumb for fresh grease pack in precision ball bearing.

                          #2 Pack no more than 1/3 the volume between races.
                          That's what all the bearing manuals say: grease no more than 1/3 of the total volume of the race.

                          The Barden manual actually suggests injecting the grease from 12 to 4 O'Clock on the bearing race (i.e., 1/3rd) and spinning the races to distribute the grease.
                          "Twenty years from now you will be more disappointed by the things that you didn't do than by the ones you did."

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                          • #14
                            Thanks for all the good info. The incident that raised the question was the failure of the upper steering col. bearing in my F250. It would seem to me that said bearing has little stress on it, certainly not from high speed use (I don't spin donuts in the truck!). The replacement bearings look like they were held over the grease pot for a few seconds before being packaged. I figured that Ford knows how much and what kind of grease should be in there (perhaps not -- this is the only time I've ever had such a failure in over 40 years of driving). I resisted the temptation to add more grease.

                            An aside, these bearings look really cheezy and under-designed with sheet metal inner and outer races. I thought about replacing them with something better from the bearing house, but of course, they're not a standard size.

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                            • #15
                              The problem was not with the grease pack. The problem was the fact that it was installed in a Ford.

                              Good thread - I never really considered how much or little grease there should be in a bearing.

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