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BadDog
06-28-2007, 12:51 AM
It's late and I hoped to get some feedback before putting this back together tomorrow, so I cross posted from PM. Sorry for any inconvenience...

Post
I have a cheap project BS 6x12 that I am cleaning up and assembling. During disassembly, the aluminum seal in the back of the spindle was oxidized and shed some crap into the rear spindle bearing (which is not sealed or shielded). The grease in there looked beyond terrible, somewhat like brown wax. When I removed the rear bearing, I found out that coolant had intruded and there was some corrosion inside the spindle housing, so I disassembled the whole thing to clean well. Front bearing seemed dry and also showed signs of waxy grease extrusion past the inner shield.

So, with no idea how much rust, aluminum flakes, or anything else that remained, I decided there was nothing to loose and took off the shields on the front bearing before flushing out all the old crap. Surprisingly the bearings seem unhurt and I figured it would be worth it to try them out to see how they work. But I have 2 questions.

1) What grease to pack them with? I figure the best thing I've got is Mobile Lith SHC 220 Synthetic. Very tacky without being terribly heavy, supposed to handle high rpm and "extreme duty". It's also listed as resisting flush out and such for coolant use.

2) I saw in the BS literature that there are supposed to be marks on the bearing races to indicate "highest points" and that the marks are to be aligned on the same side when assembling. These bearings have no such marks.

For reference, they are labeled as follows.

Front: Barden 205SS
Rear: Barden 204H

Perhaps these bearings are not original?

If they fail, I've lost nothing but a little time which does not worry me. For my HSM needs I don't require perfection, so we will see. I should be putting the spindle back together tomorrow so any thoughts at all and ASAP will be much appreciated...

lazlo
06-28-2007, 01:39 AM
Baddog,

Those Bardens are precision 15 angular contact (non-duplex) bearings. The 204H is a 47 x 20mm open bearing.
The 205HSS is a 52 x 25mm shielded (probably on the business end of the spindle).

Barden marks the TIR high point differently than other vendors: it's either a polished circle on the older bearings, or a stamped hash mark on the newer bearings.

Those are very nice bearings if you can re-pack them.

The down-side is that shielded bearings typically can't be opened without destroying the shield, so they're not really meant to be serviced. On a sealed bearing you can pop the seal and re-pack them, but they have higher friction than shielded bearings...

Good luck!

Robert

BadDog
06-28-2007, 02:21 AM
These are steel shielded, not sealed. And they are held in by a very thin snap ring. I simply popped the springs and used air to eject the shields.

I'll look for the hashmarks or polished circles. Where would the mark be? On the face with the other information? The "back" side?

And what do you think about the choice of lube? If they are that nice, and they aren't already junk, then I would hate to ruin them by using the wrong stuff...

Much thanks for the info!

BadDog
06-28-2007, 04:28 AM
I went out and looked at it very carefully under my Luxo, not hash or specially polished area that I could find.

lazlo
06-28-2007, 11:31 AM
Where would the mark be? On the face with the other information? The "back" side?

On the Barden's I have, the TIR is marked on the same side with the Barden Logo. Barden mentions in the tech notes that
some bearings are not marked. I don't know if they only mark the duplex pairs (which is all I have).


And what do you think about the choice of lube?

Bearing greases are a religious issue :rolleyes: I use Mobilith SHC, which is Mobil's high-quality bearing grease: synthetic oil base with a lithium thickener. Works great. MSC carries it:

http://www1.mscdirect.com/CGI/NNPDFF?PMPAGE=2612

pcarpenter
06-28-2007, 12:01 PM
Back when I did a bunch of research on what to re-pack my sealed Bridgeport spindle bearings with, I ended up with a couple of choices recommended by bearing manufacturers for sealed bearings. I ordered a tube of Moblilgrease 28 which is a synthetic that is commonly used in aircraft applications. In fact, I orderd it from an Aircraft maintanence supply place in Florida.

In this environment, you do not want too much lubricant induced friction, so an NLGI 1 rather than the standard NLGI 2 is recommended. This is also a synthetic that works well in environments (like sealed bearings) that will not allow for regular replacement of the grease.

In the case of spindle bearings, the term "packed" is really a misnomer. I have heard that somewhere around 40% is the correct amount of fill. Going beyond that can result in too much frictional heating from the grease having to be constantly moved around as the balls and retainer rotate. In short, more is not necessarily better. When greases are viewed properly...that is as a carrier for the base oils they contain....its easier to understand what to expect from them.

Paul

lazlo
06-28-2007, 12:15 PM
Mobilgrease 28 uses a clay-based thickener, which a lot of bearing manufacturers, including Barden, recommend against for angular
contact bearings.

40% grease fill is a little high. The Barden bearings come with a nice installation guide, and they recommend a 25% grease fill. A
couple of Old-Timers have recommended one-third fill.

Agree on the thickness -- the Mobilith SHC I suggested is NGLI 1.5. Any thinner consistency than that and it's almost like a gel.

The Kluber Isoflex NBU-15 that folks on CNCZone sing songs about is NGLI 2 (roughly the consistency of creamy peanut butter).

BadDog
06-28-2007, 01:20 PM
Lazlo: That's the same SHC 220 I was considering in my first post. And I'm aware of the overpacking issue, though I didn't know the percentage recommended by Bardon. Good to know, and much thanks...

PCarpenter: Thanks for the recommendation on packing amount and grease. The NLG1 info has me thinking, might be better to have the thinner grease. Then again, the previous grease was VERY firm, pretty much like soft seal wax. Since Lazlo has experience with the Bardons specifically, and I have the SHC 220 on hand, I guess I will try that if nothing else comes up to change my mind. At least it should be far less likely to heat up (my shop is often over 100* ambient to start with) and run out.

lazlo
06-28-2007, 01:53 PM
BadDog, if I just noticed that JRIowa (lubrication engineer) replied to your question on PM, and recommended against Mobil SHC.
Mobil does make a polyurea-based grease that he's recommending -- Mobil Polyrex, but MSC doesn't carry it. It's a pretty rare, and expensive grease.

If you read that Barden (spindle-bearing) grease guide he posted, they're all 40 micron filtered, NLGI 2 greases. Major bucks for a 30cc syringe, and you need to special order it from a Barden distributor.

The upside is if you're willing to pay $100 for a little syringe of grease, they tell you exactly how many cc's to inject for a particular bearing :)

BadDog
06-28-2007, 02:55 PM
Yeah, I saw that. Wow! Took me a while to digest all that great info. Not sure what to do now. In fact, I may just assemble what I can without the spindle, then box it up and wait a bit to order some better grease. I don't want to put much into what may already be junk from wear or my error (after reading that, I'm thinking I may have been too rough taking it apart?), and I don't need perfection, so hopefully I can find a reasonable path if I don't rush...

lazlo
06-28-2007, 03:48 PM
Like I said, it's a religious issue :D

Since you're just trying to get an old surface grinder up and running, I think any modern non clay-based NLGI 1.5 grease will be fine.

Make sure you completely clean out the old grease though -- there's a lot of compatibility issues when mixing the various kinds of grease.

BadDog
06-28-2007, 04:01 PM
It's already completely (and repeatedly) flushed out.

So, since a lot of grease adds don't say anything about "clay", are there any specific keywords to look for to make sure I get the right stuff? It's hard enough to even find NLGI 1.5...

BadDog
06-28-2007, 04:06 PM
There is a wealth of info appearing on the other thread, so rather than try to transfer, here is the link for future reference.

PM Cross Post Thread (http://www.practicalmachinist.com/cgi-bin/ubbcgi/ultimatebb.cgi/topic/30/5656.html?)

Willy
06-28-2007, 04:15 PM
BadDog, not to muddy the waters but here's a little more info on the care and feeding of bearings.

http://www.enerchecksystems.com/articl04.html

BadDog
06-28-2007, 04:28 PM
Thanks, I love information overload. :D

Seriously though, thanks for the info. Lubrication (and precision bearings) is one of those areas where I could use a good boost in my knowledge, and nothing should be taken for granted that I already know. We can talk all day about automotive bearings and lubes, but I'm a newbie with machine tools...

Willy
06-28-2007, 04:34 PM
If you really want a quality textbook on bearings, go to the FAG website and order their master catalog. A beautiful harcover textbook on bearing design and care is incuded. It has now become my bearing bible. Best of all it's free.

lazlo
06-28-2007, 04:36 PM
So, since a lot of grease adds don't say anything about "clay", are there any specific keywords to look for to make sure I get the right stuff?

All grease is basically some kind of oil with a thickener added. So any quality grease will specify the oil base (conventional refined oil, mineral oil, synthetic oil, ...) and the thickener agent.

Here's a table of the most common bearing greases, and their thickening agent. A better table would show the oil base as well:

http://www.abtbearing.com/greasetypes.html

Willy
06-28-2007, 05:10 PM
It took me a while to find again, but here is a link to the catalog to which I reffered to in my earlier post.

http://www.fag.com/content.fag.de/en/services/library/shoppingcart.jsp

pcarpenter
06-28-2007, 05:17 PM
I don't think you can conclude anything about the NLGI grading of the old grease.... the base oils tend to separate out over years leaving nothing but a thickener-dense (minimal oil) hard goop.

I don't know what to make of the clay base vs. poly base, vs. lithium base discussion. I have heard arguments all over the place. I think the big issue is that it have a thickener that will give up the base oil (of appropriate viscosity) under whatever the normal operating conditions are for the bearing involved and hold on to it up to that point so you don't have bearings with a blob of thick left over thickener goop on top of a puddle of oil that wicks its way out from under the grease seals. This is especially true in a vertically oriented mill spindle where the oil will just run out around the center race wiper.

One caution I will give is that people get all cought up in special greases designed for spindle bearings that are rated for high speeds....when their spindle is not even close. High speed spindles are (today) running in the tens of thousands of RPM's....not a few thousand or less.

That having been said, I am all for the better synthetics for those of us who will not wear out a set of bearings due to limited use, before ordinary greases will turn back to dinosaur paste. Longevity in our case is measured in time sitting (and the lubricant separating or leaking) and not so much in total hours of use. The synthetics are also superior in environments that are not so carefully temperature controlled. I re-packed a knee lift bearing for my mill last year in an NLGI 2 petroleum grease and ended up doing it all over.....January rolled around and the shop was around 50F prior to warm up and it was like I had packed it with roofing tar.

Paul

BadDog
06-28-2007, 06:49 PM
Thanks all.

Willy: I checked for that document on your link. My basket is tracked separate from yours, so I saw nothing. Is it 029679141-0000?

Direct Link to Catalog (http://www.fag.com/content.fag.de/en/services/library/library.jsp?addedItem=rel%20PubLanguage(386195)&isDownloadable=1&companycategory_id=all&pubmediacategory_id=3748&showPicture=1&page_size=5&query=PubLanguage&isOrderable=1&branchcategory_id=all&language_id=EN&productcategory_id=all&submitted=true)

Willy
06-28-2007, 07:07 PM
Thanks all.

Willy: I checked for that document on your link. My basket is tracked separate from yours, so I saw nothing. Is it 029679141-0000?

Direct Link to Catalog (http://www.fag.com/content.fag.de/en/services/library/library.jsp?addedItem=rel%20PubLanguage(386195)&isDownloadable=1&companycategory_id=all&pubmediacategory_id=3748&showPicture=1&page_size=5&query=PubLanguage&isOrderable=1&branchcategory_id=all&language_id=EN&productcategory_id=all&submitted=true)

Yes,that's it...Rolling Bearings.
1450 pages of hardcover bearing info...it might take a couple of weeks, they ship from Germany.

BadDog
06-28-2007, 07:19 PM
Thanks, just ordered...

Spin Doctor
06-29-2007, 07:00 PM
Mobilgrease 28 uses a clay-based thickener, which a lot of bearing manufacturers, including Barden, recommend against for angular
contact bearings.

40% grease fill is a little high. The Barden bearings come with a nice installation guide, and they recommend a 25% grease fill. A
couple of Old-Timers have recommended one-third fill.

Agree on the thickness -- the Mobilith SHC I suggested is NGLI 1.5. Any thinner consistency than that and it's almost like a gel.

The Kluber Isoflex NBU-15 that folks on CNCZone sing songs about is NGLI 2 (roughly the consistency of creamy peanut butter).

Go with the Kluber. The best way to insert the grease is with the syringe that comes with a fill chart in cc's for each size bearing. But if it already hasn't been said the odds are that unless you were extremely careful taking the spinple out and the bearing off they are probably already a lost cause. Plus the way you describe the condition of the lube and the amount of contamination IMO the bearings would be suspect.