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Dry spindle bearings

MikeJB

Aluminum
Joined
Mar 5, 2007
Location
Aylesbury, U.K.
My Elliott 921 surface grinder still does a very reasonable job; not perfect but plenty good enough for the majority of work.

Trouble is the spindle bearings sound 'dry'; the manual says regrease every 18 months but don't tell you how. Looks like you would have to tear down the whole spindle to do it.
Machine is probably 30+ years old and my guess is the bearings have probably never been regreased.

I cannot detect any amount of play in any direction either axial or radial and the spindle runs freely and smoothly except for the dry noise.

It has a pair of angular contact bearings at either end of the spindle.

Would regreasing prolong the life of the spindle and would dismantling be in danger of damaging the bearings?

Shall I just leave well enough alone?

Regards,

Mike.
 
Would regreasing prolong the life of the spindle and would dismantling be in danger of damaging the bearings?

Not being familiar with your grinder I can only speculate. Since the manual says to regrease, it would be prudent to do so before the spindle starts to display measureable wear. Since they are angular contacts, they may actually be unshielded under some auxilary dust covers. The bearings I removed from my grinder had tiny snap rings on top of metal shields that could be removed for regreasing. The bearings I replaced them with were permanently sealed. -Mike
 
The "danger" of angular contact bearings, is if you press them off the shaft by only gripping the outer bearing race, depending on which way they are mounted, you can press the outer race right off the bearing. If you can't grip the inner race, you risk messing up the bearings. This is dependent on which way the thrust side of the bearing is oriented.

Thirty year old grease is NASTY stuff. Your bearings would LOVE some attention! Most of the grinder heads I rebuild that are thirty years old, the grease isn't grease any more, but some nasty coagulated goo.
 
Any chance that you can find some plugs which you could remove, and install a grease zerk into? Electric motors often have the grease passages plugged with pipe plugs, but regreasing is possible with them. If you can find a 'drain plug', then perhaps you can regrease the heck out of the bearings, in hopes of purging the excess out of the drain hole. I imagine it would be important to let the spindle run for a considerable length of time with the drain plug out in order to allow the excess grease to expel completely.

Having suggested that, I don't suppose you would want to run an ultra-expensive grease through and waste it that way.
 
Usually the reason to dismantle a spindle is to replace the bearings so it doesn't matter if you damage the old ones. In my case I would want to put the old bearings back if they are in good condition and only needed a regrease.

Removing bearings will quite often damage them because sometimes the only way to get them out is to press on the inner race to get the outer race out; will ruin a precision bearing for sure. I often use small instrument bearings and I learnt long ago to never press them in with the inner race. I usually make up a special mandrel to do the job.

I'll have to see if I can clean out and regrease without stripping the whole thing.

BTW the reference to expensive grease; my manual recommends Shell Alvania for the spindle bearings; this is probably about the cheapest grease you can buy. Should I go for something better or just go with the manufacturer's recommendation?

Regards,

Mike.
 
Having suggested that, I don't suppose you would want to run an ultra-expensive grease through and waste it that way.
Well, now you mention this topic, I would like to have a opinion on this.

My case is an Hembrug U2 universal grinder, from the sixties. I heard a sqeeking noise in the main spindle when it was first started up by me.
I thought some extra grease would be the solution.

Advised grease in the manual :
Shell - Alvania 2 EP
Esso - nebula EP 1
My local suplier converted this to :
Kroon oil - Lithep Grease 2
kroonoil website (no connections with this firm, just their HQ is 20 km from my place)

Description of the lithep grease 2

> Lithep Grease 2 is a multipurpose lubricating grease, manufactured from
> well-refined high-viscosity base oils and lithium soap thickener with
> selected EP- and other additives to obtain the following properties:
> Great adhesion to metals
> Excellent water-displacing capacity
> Very good stability
> Very effective against wear and corrosion
> Very good pumping qualities
> Excellent Extreme Pressure (EP) properties
>
> Application :
> Lithep Grease 2 may be used for the lubrication of all types of bearings of vehicles and earth-moving
> equipment working under heavy duty and shock load conditions.
> It also applies for heavy duty pivots in moist and dusty areas.

I added a few strokes of this grease and tried to run the spindle. It rotated very slow taking a lot of time to reach its working 3000 rpm. In the high speed 6000 rpm it didn't reach its topspeed at all and the motor blew the thermal overload.
Time to remove the spindle. There are some very interesting issues about this which everyone considering this operation should read in ADVANCE !! of dismounting the spindle. bearing-replacement-thread

I made a complete set of spindle dismounting tools as described in the manual of the Hembrug tool pictures here

Now raises the question do I grease the spindle according to the old (maybe outdated) instructions or do I use one of the newer greases.
I asked another dealer for another millingspindle (about 3000 rpm tapered rollerbearings) ad got this advice:
Klueber isoflex NBU15
the klueber website does not supply a lot of information about it
I do know that NBU15 is pretty expensive compared to the "lithep grease 2" but it's available in small quantities starting at 50 gram.

Can anybody tell what he is using (and why) or have an advice?
 
I'll have to see if I can clean out and regrease without stripping the whole thing.
I doubt if that will work. I soaked my dismounted bearings for a day in dry-cleaning naphta (translated "wasbenzine") and still are the globs of dry fat coming out.
I have a ultrasonic cleaner with bio-degreaser but I think it will harm the bearings is that true ?

BTW the reference to expensive grease; my manual recommends Shell Alvania for the spindle bearings; this is probably about the cheapest grease you can buy. Should I go for something better or just go with the manufacturer's recommendation?

I think we were asking the same question at the same time but you can type faster. ;)
 
Yoyo,

It looks like the Kroonoil grease is for heavy duty pivots, highly loaded bearings working at slow speeds- the sort of sticky grease a backhoe operator has in a bucket with no lid in the cab and a dirty stick of wood to apply it with.

At least the description for Shell Alvania makes a mention of high speed ball bearings in its application notes.

How much actual knowledge has your 'local supplier' in the field of grease and its applications, or did he just look in a book. Are his usual customers farmers or building contractors?

You may have been misinformed.

Regards,

Mike.
 
Its been my experience that ordinary varsol or mineral spirits won't dissolve old wax from old grease, in fact, it seems to turn the wax into a sand-like grit.

A very hot-oil flush might work, but you'd need an inlet and an outlet to the bearing to do the job.
 
It looks like the Kroonoil grease is for heavy duty pivots, highly loaded bearings working at slow speeds
That was my feeling too. I think the telephone operator at Kroon has a list with conversions and this was the answer on his list. The grease seems just to thick for highspeed operations.
That's why I asked others to give their view on the subject.
 
While on the subject of grease, some people will recommend grease with Molybdenum Disulphide because they perceive it as 'better' than ordinary grease.

I was told many moons ago that MoS2 is a low friction additive for applications that have a sliding motion such as car CV joints, ball joints, plain bushed shafts etc., but definitely NOT for ball or roller bearings because the low friction will encourage the balls/rollers to skid when they should be rolling.

Anybody got any views on this?

Regards,

Mike.
 
Some of the spindle bearing greases are very thick, called channeling grease. This type of grease requires a very small amount carefully applied to instructions.
This one is fitted with a normal grease nipple and grease channels. I don't think it leads to a sophisticated method of lubricating the bearings. Also there are no special instructions in the manual.
I think I take my chances with the Klueber Isoflex.
 
Pumping a few shots of grease into a bearing, is NOT the way to grease a bearing. Most angular contact bearings don't work well STUFFED with grease- in fact they are supposed to only have a 25 to 50 % fill ratio. The difference in temperature a spindle runs at when FILLED with grease, to only having a 25% fill, is huge. I know this because I've built and run spindles just to find out.

HIGH precision bearings DO NOT get pressed into housings with much if any interference fit. The ideal fit is the bore being exactly the same size as the OD of the bearing. The fit on the spindle in a perfect world is almost the same. PRESS fits are for lesser precision machines, like CARS and wheel barrows. Having even a couple of tenths press fit CHANGES the preload of the bearing!

I use Kluber in my spindles, inserting it into the bearing with a syringe. This allows me to exactly know how much I'm installing, it gets it right in where it should be, and I don't have to wipe any of this incredibly expensive grease off my hands onto a rag!!! When you pay a hundred bucks a tube for grease, you want to use EVERY BIT of it!
 
Thats right on Brian.
I hate to be the voice of doom, but, in my experience, if the the bearings make any noise at all ,they are done.
For some it has, but for me it has never worked out relubing that type of bearing. If the spindle has to come out, it gets new bearings.
 
Grease, Syringe, etc.

(All of this makes the Lithium greased autolube on my mill seem really nice. The grinder has no such feature, so...)

OK folks, following up on Brian's very sensible advice, I will ask the following ignorant new guy questions:

1. Do you inject grease into each little space between the balls? Do you inject a little grease in the top or bottom and turn the shaft by hand?

2. What happens to the old grease? One assumes it wears out, wears or burns away, or becomes contaminated (which is why you are regreasing, no?) For engine oil one drains the old oil. Does one somehow drain the old grease? We surely don't want any grease solvents left in the bearings do we? Just adding new grease won't remove contaminates from the old grease will it?
 
I don't ever inject grease in bearings unless they are clean. So if you're thinking of just sticking some grease in an already greased bearing, we're on another page. I never figured if after removing a spindle from a machine, that you WOULDN'T clean out the old grease. If you're thinking that you don't have anything to lose by trying to clean out the bearing while it's still on the spindle, and then greasing it, why not?

When I do clean bearings, I use lacquer thinner and an acid brush. Of course I prefer to have them OFF the spindle and then they can soak in a pan. On the spindle gets a little messy. Watch the hairs falling off of acid brushes. I may use three different soaks of thinner, and then follow with a rinse using new lacquer thinner in a paint pot. Of course the paint pot has to be spottlessly clean- no remnants from the last paint job! I have a paint pot I use, that's never sprayed paint. I use it to clean all of my castings before they get painted. So it's already perfect for cleaning the occasional bearing. Of course for cleaning bearings, you want to be sure your shop air is CLEAN- run through a water seperator- filter. I apply grease in between every ball. Doesn't take long at all. Fortunately it's a rare day I'm not using NEW bearings. What happens to the old grease? Well if its like a lot of the DUMORE grinder heads that I've gotten in after sitting unused for thirty years, the grease turns into CONCRETE. It's all there but magically has changed from from a lubricant to a glue.
 
OK.

I was asking in the context of maintence. Original poster says their manual says to 'regrease every 18months' - would they be expecting you take the spindle apart that often ?!?!

Perhaps what you do when there's a fitting designed to add grease, and what you do when doing a rebuild, are different?

Brian - after you grease and reassemble a grinder spindle, how many hours use/calendar time does it go before you have to take apart again?

(I'm kind of used to cars where we change out oil or change out transmission fluid, and don't normally disassemble the engine or transmission to do it. Modern wheel bearings seem to run a very long time and then replaced in toto.)
 
I don't have ANY grinders with zerk fittings, so I'm never tempted to just "give it a couple of pumps". In a perfect world, I guess we'd all do regular maintenance on our spindles, but the reality is we don't until there's a problem with finish, or it starts making obnoxious noises. I think any GRINDER manufacturer who puts a zerk fitting on their spindles, either uses electric grade open ball bearings or has an idiot as an engineer. The majority of medium speed spindles seem to have the old "LIFETIME LUBRICATED" label somewhere. What's lifetime? When they're noisy, they're history .

95 % of the spindles I build, I never see again, they get shipped out and I move on to the next project. The only spindle in my shop that I've done more than once, is an ID grinder spindle. These tend to have a pretty tough life, with coolant blasting on them, spinning at pretty high RPM. The higher rpm spindles get fed with a mist lubricator, and seemed to have lasted quite a whiile.

Regreasing all the spindles in my shop every 18 months would be a full time job!
 








 
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