Author Topic: How to change grease on sealed bearings?  (Read 1181 times)

Offline PekkaNF

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How to change grease on sealed bearings?
« on: June 29, 2017, 06:47:21 AM »
Situation is like this: I can buy just the right bearing, but it has wrong lubricant and wrong amount of it. I.E. I want low friction sealed bearing with very little high rpm grease.

Industry would just spesify the bearing, seal and grease and order a pallet load of them.

In priciple it is easy: Pop out the seal, wash and a dab of correct lubricant. Wrong. All has to be very clean and I have tried some mildly high speed (like hand routers) stuff and the rubber seal never goes back as good as original. It might look fine, but the lip rubs and generates heat.

This how-to-not:
https://youtu.be/Np5dcns64Fs

Although this is interesting:
https://youtu.be/tO3BbwkMdFI

Starting from new design I could use one sided seal and arrange sealing othervise or put two back to back.

Offline russ57

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Re: How to change grease on sealed bearings?
« Reply #1 on: June 29, 2017, 08:45:59 AM »
 Could you use a hypodermic needle with some solvent to flush the old grease out? Through the rubber seal. Id think it would self-heal sufficiently. Then either inject the new lubricant, or maybe try that vacuum approach.. Hard to control the amount that way though.
Russ

-russ


Offline David Jupp

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Re: How to change grease on sealed bearings?
« Reply #2 on: June 30, 2017, 09:19:12 AM »

Offline PekkaNF

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Re: How to change grease on sealed bearings?
« Reply #3 on: June 30, 2017, 04:14:15 PM »
Actually I have heard of that sort of services, that looks pretty specialized. I have heard some cases of a pallet of bearings nearing self life filled with fresh grease and sold. Don't knew if they went on agricultural or consumer stuff or just sold wheere ever.

Anyways, have been working with Ford focus 2006 pissing off cooloant from core plugs - at cylinder head between sparkplugs.

I might need to test this one soon or maybe I get lucky and find the appropriate bearing from the self.

Pekka

Offline awemawson

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Re: How to change grease on sealed bearings?
« Reply #4 on: June 30, 2017, 04:19:28 PM »
I've never tried, but is it not possible to ease the rubber seals out of a bearing and then re-fit them? I would have thought that is was  :scratch:

In which case just flush the bearing with the solvent of your choice (I'd use a WD40  or brake cleaner spray) then re-lube as needed
Andrew Mawson
East Sussex

Offline awemawson

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Re: How to change grease on sealed bearings?
« Reply #5 on: June 30, 2017, 04:24:44 PM »
Here you go, looks easy enough:

<a href="http://www.youtube.com/watch?v=gCXMICrjKd4" target="_blank">http://www.youtube.com/watch?v=gCXMICrjKd4</a>

Andrew Mawson
East Sussex

Offline mattinker

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Re: How to change grease on sealed bearings?
« Reply #6 on: June 30, 2017, 04:34:22 PM »
I have done this very frequently over the last thirty years. I discover how little grease there were in bearings with seals when I worked with an auto electrician in Toulouse. My colleague systematically took the seal of alternator bearings and repacked them.

Never had any trouble doing this!

Regards, Matthew

Offline PekkaNF

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Re: How to change grease on sealed bearings?
« Reply #7 on: June 30, 2017, 07:35:06 PM »
RS sealings come out and are easily pressed back easy too. However I only had good degree of success on low rpm application. Whenever I tried this to low friction type seal it did not work that well. They look the same than RS seal, but often are harder material and they should nor rub. Bit like plastic version of Z (dust seal). Got some one sided RS and Z bearing on last batch, have some time to experiment.

Pekka

Offline edward

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Re: How to change grease on sealed bearings?
« Reply #8 on: July 03, 2017, 09:30:53 AM »
The 2RS seals on my bike bearings come out no probs for a quick flush and a squirt of new grease. I use a scalpel to pop them out but they are only small-ish ones like 6000, 6001.

Offline sparky961

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Re: How to change grease on sealed bearings?
« Reply #9 on: July 03, 2017, 10:10:42 AM »
Have you checked if you can get brand new replacement seals? You might have better luck getting a new one back into place.

Offline Groundhog

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Re: How to change grease on sealed bearings?
« Reply #10 on: August 03, 2017, 11:18:21 PM »
A common mistake is to over pack bearings with grease. The manufacturer will usually publish the proper amount of grease for a particular bearing.

For a general rule of thumb (from a SKF web site);

"Super-precision bearings operating at high speeds should have less than 30% of the free space in the bearings filled with grease...
Open angular contact thrust ball bearings for screw drives should be lubricated with a grease quantity that fills ~ 25 to 35% of the free space in the bearing...
Sealed bearings are filled with a high grade, low viscosity grease that fills ~ 15% of the free space in the bearing. They are considered to be relubrication-free under normal operating conditions..."

If packed with too much grease they will run hot (not enough room for the balls to rotate freely).
Racers say that horsepower is how fast you hit the wall and torque is how big of a hole you make.

Offline hermetic

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Re: How to change grease on sealed bearings?
« Reply #11 on: August 05, 2017, 11:36:38 AM »
 Yes, you can easily remove the seals with a sharp point like a compass or jewellers screwdriver.. Sorry, but regardless of what the manufacturers say, I don't go for underfilling bearings. On electric motors, in the day when  they had grease nipples, we would clean the nipple, remove a plug from the lower part of the bearing housing, and pump with grease to force out all the old grease, and keep poumping till new grease appeared at the plug hole. This meant that due to the design of the bearing housing, the bearing was 100% full. . Brook motors used SKF bearings, and these were fitted as new equipment. We never had a bearing failure unless the grease was the wrong grade, or contaminated. Some of the motors I rebuilt had done 35 years operating in the clean conditions of a powdered milk plant, and even after this extended life, which included daily maintenance, the bearings were still servicable. Less grease = more sales!! The sealed for life bearing usually has a life of 5 years or less!

Offline Doc

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Re: How to change grease on sealed bearings?
« Reply #12 on: August 05, 2017, 12:12:00 PM »
  I totally agree. I have a side business rebuilding electric motors,alternators and starters . And I never let a job go out of the shop without filling the bearings. Just remove seal and fill with a good quality grease and replace seal. I have never had a job come back where any f my bearings have failed. (just saying) My father-in-law owned the business before me and I bought it from him as a little side line cash generator and he will say the same and he was in the line of work for 60+ years! So I'll trust him and continue to do the same.
George

Offline petertheterrible

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Re: How to change grease on sealed bearings?
« Reply #13 on: August 09, 2017, 01:55:07 PM »
Probably not pertaining to your problem.  Had obsolete water-cooled engine with cooling fan on a stub-axle, identified a whine one morning when checking oil.  The whine turned out being a double roller with shaft, that had metal seals.  Being in a hurry to get the machine up and running (grader), I took the bearing (still in casting and being imperial) and boiled it in some grease, not the synthetic grade after I cleaned it with a cloth.  The bearing saturated with grease and lasted until the replacement arrived.
Terrible by name, worse by profession.

Offline chipenter

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Re: How to change grease on sealed bearings?
« Reply #14 on: August 09, 2017, 05:48:13 PM »
Had the repair a 1/2" Router today bottom bearing screeming , took it apart to get the size of the bearing , poped the seal no grease but some sticky dust , cleaned and filled with grease jobs a good un , I was going to buy a new bearing .
Jeff