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View Full Version : How much grease in a ball bearing?



gregl
04-04-2009, 09:55 PM
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?

E.T.Jr
04-04-2009, 10:26 PM
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...:confused:

Gary Reif
04-04-2009, 10:32 PM
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

agrip
04-04-2009, 10:35 PM
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

GadgetBuilder
04-04-2009, 10:40 PM
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

agrip
04-04-2009, 10:43 PM
I wish I had said that
Ag

oldtiffie
04-05-2009, 12:49 AM
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.

Tobias-B
04-05-2009, 04:05 AM
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

J Tiers
04-05-2009, 09:30 AM
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.

oldtiffie
04-05-2009, 09:54 AM
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!!

moe1942
04-05-2009, 11:49 AM
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.

pcarpenter
04-06-2009, 02:03 PM
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

lazlo
04-06-2009, 02:06 PM
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.

gregl
04-06-2009, 10:29 PM
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.

Fasttrack
04-07-2009, 12:56 AM
The problem was not with the grease pack. The problem was the fact that it was installed in a Ford. :D

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

old#7
04-07-2009, 01:31 AM
Sealed bearings are in fact sealed. You can't grease them unless you break the seal.
I'm sure your steering column doesn't have a grease zerk next to the turn signal.

tdkkart
04-07-2009, 01:56 AM
I worked for a "grease is grease" guy that owned a chain of equipment rental stores. Somewhere he apparently bought a pallet full of 5 gallon pails of generic "grease" which he insisted we use for packing wheel bearings on the rental trailers. Not sure what the stuff in the pails was but it was not wheel bearing grease by any stretch.
The trailers saw very limited use, very few miles/year and usually lightly loaded, but every year they replaced MANY bearings. Bearings that would have lasted most people 1/2 a lifetime if they used the right grease in the first place.

moe1942
04-07-2009, 08:17 AM
Sealed bearings are in fact sealed. You can't grease them unless you break the seal.
I'm sure your steering column doesn't have a grease zerk next to the turn signal.



I have re greased sealed bearings for many years. Poke a very small hole in the dust seal with a sharp scribe. Use a flush fitting tip on the grease gun and apply four small strokes turning the bearing 1/4 turn before each. The bearings in my 1960 Miller welder/gen for one, is still working like new.

lazlo
04-07-2009, 09:33 AM
Sealed bearings are in fact sealed. You can't grease them unless you break the seal.

I think you may be thinking of shielded bearings. Sealed bearing are made for the shield to be removed so you can re-pack the bearings. Shielded bearings have a thin metal foil shield that you can't remove without crumpling it. At least, I haven't found a way.

rantbot
04-07-2009, 01:32 PM
This is all correct. Over-greasing tends to cause overheating. This is true even if many people don't believe it. One third full is good, one half isn't too bad, more is too much.

Spin Doctor
04-07-2009, 06:38 PM
Back when I was doing spindle work full time we primarily used Kluber NBU-15 and NCA-15. We normally bought grease in 30cc syringes that were graduated. Each syringe was packaged with a chart that called out the proper amount of grease for each bearing (angular contact 15 and 25D primarily) in that bore range. Now the grease was actually sold under a Barden part number (G46 for the NBU-15) as it was bought in bulk and repackaged by Barden. The syringes took a lot of the guess work out of packing bearings during spindle rebuilds. Also one thing with grease is not all greases are compatable with other greaes and oils. Normally I would use denatured alcohol in a spray bottle to flush the shipping oil out of the new bearings imediately before packing (let the alcohol evaporate off). The Barden rep assured me that while the packing oil probably wouldn't hurt the grease what I was doing was not going to hurt either. I can't think of a single spindle failure we had that was related to lubrication failure. We did have failures due to seal faults and over tightening of drive belts but those weren't my fault at least.

Robo
04-07-2009, 09:23 PM
I work for a local municipality and worked for about 3 years at their water plant doing maintenance work. During that time I went to a class on pump rebuilding etc. One section of the course was about bearings and grease.....how much? The instructor who IMO was a very sharp fellow worked for sunstrander and joy throughout his career (he explained about building an oiless air compressor he helped design that ran at 70,000 rpm for NASA). The method he uses to adequately grease bearing requires a stethascope. Listen to the bearing add grease, listen again if bearing is quieter add more grease, listen, if quieter add more grease etc. Until you add grease and the bearing doesn't change sound then the bearing has enough.

lazlo
04-07-2009, 09:54 PM
Each syringe was packaged with a chart that called out the proper amount of grease for each bearing (angular contact 15 and 25D primarily) in that bore range. Now the grease was actually sold under a Barden part number (G46 for the NBU-15) as it was bought in bulk and repackaged by Barden. The syringes took a lot of the guess work out of packing bearings during spindle rebuilds.

Barden's precision bearing catalog tells you how many CC's of bearing grease for each bearing. I don't think I've seen that in any other bearing catalog.