Precision Spindle bearings, Installation and lubrication

I was reading about grease volume or how much grease and what brands to use and found these super articles.
I took a class at SKF bearing class years ago and back then they told us to use 30% grease pack. I see in these modern CNC spindles they say 15 to 30 % pack. Over packing bearings will create heat.

High Speed Spindle Design and Construction :


Modern Machine Shop

How to Replace CNC Spindle Bearing Part 2

Also in practical machinist a few years ago there was a good thread on replacing spindle bearings.

http://www.practicalmachinist.com/vb/general/spindle-bearing-grease-256614/


Trying to point out different points of view exist but generally most of us agree more then 30% grease is to much on precision bearings and not start an argument.

Richard King said:

I was reading about grease volume or how much grease and what brands to use and found these super articles.
I took a class at SKF bearing class years ago and back then they told us to use 30% grease pack. I see in these modern CNC spindles they say 15 to 30 % pack. Over packing bearings will create heat.

High Speed Spindle Design and Construction :


Modern Machine Shop

How to Replace CNC Spindle Bearing Part 2

Also in practical machinist a few years ago there was a good thread on replacing spindle bearings.

http://www.practicalmachinist.com/vb/general/spindle-bearing-grease-256614/


Trying to point out different points of view exist but generally most of us agree more then 30% grease is to much on precision bearings and not start an argument.

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Well, I'm glad this is not intended as an argument.

There are indeed different opinions when it comes to the amount of grease fill in bearings but I am glad to say that those opinions can be safely ignored - most come from people reading documentation carelessly. Here's what SKF says on their WEB site:

Grease lubrication

The ********* recommendations are identical only I have them in German.
The Kluber recommendations are also identical.

We see there that how much grease to put in a bearing depends on it's speed factor which is rpm times mean diameter. In our previous thread the OP was lubricating a 7205 which has a mean dia of aprox 38mm. At 2000 rpm the speed factor would be some 76000. But that is the max rpm and usually a manual machine used by say a toolmaker is ran much slower , somewhere around 500 rpm give or take.

With 76000 speed factor we see from SKF's Table 1

Speed ranges for grease lubricated radial bearings

that this is considered LOW SPEED. Further down the page SKF says :

"SKF recommends the following grease fill percentages for bearings:
100% for LOW SPEEDS...."

********* and Kluber make the EXACT same recommendations. And by the way, these EXACT figures are well known since before WWII. I have detailed service instructions for MP4 Jig Borer manufactured in 1932-34 with the exact same recommendations.

There is much more to talk here about types of greases, how to select the speed factor, how to estimate the average loads, what's a bearing and what's a housing etc but I believe those exceed the parameters of this sub-forum.

I have also bitched about this earlier. Kluber NBU-15 and 15% packing work for Dn 50mm 30000RPM spindle so it obviously has to be best also for turtle-speed WW2 era 1200 rpm mill spindle with tapered rollers.

Your arguments are compelling ..
but actual usage and real-life experience on 100k+ machine tools in service does not support that low rpm needs more grease.

Modern VMCs use high speed spindles 8k and up, some to 15k or up.
Generally none, that I know of, fail from using low rpm in service.
Some use oil, oil mist, and some use greased spindles.

I believe brother uses greased spindles, for example.
Brother is known for high speeds, excellent spindles, and long life, and no cautions re: low rpm as far as I am aware.

The kluber fill quantity link is here:
Bearing Lubrication Procedures: Part 2—Ensuring Proper Fill Quantity - Kluber USA / Canada Blog

It supports your point that for low speed use under 200k critical speed, a high pack of 90%-100% is appropriate.
BUT the grease (Kluber Isoflex 15) is also used in low speed apps like heavy textile machinery, with heavy rolls, that will *never* run at 5000 rpm, much less 8000 rpm+.
More like a few hundred rpm.
The textile machinery is mentioned by kluber.

Thus, for AC high precision bearings, in machine tools as the app, the low pack of 30% seems right--
and 2M+ machine tools in use in the world are not commonly failing under low rpm- when lubricated to 30% +/-.

AlexO said:

Well, I'm glad this is not intended as an argument.

There are indeed different opinions when it comes to the amount of grease fill in bearings but I am glad to say that those opinions can be safely ignored - most come from people reading documentation carelessly. Here's what SKF says on their WEB site:

Grease lubrication

The ********* recommendations are identical only I have them in German.
The Kluber recommendations are also identical.

We see there that how much grease to put in a bearing depends on it's speed factor which is rpm times mean diameter. In our previous thread the OP was lubricating a 7205 which has a mean dia of aprox 38mm. At 2000 rpm the speed factor would be some 76000. But that is the max rpm and usually a manual machine used by say a toolmaker is ran much slower , somewhere around 500 rpm give or take.

With 76000 speed factor we see from SKF's Table 1

Speed ranges for grease lubricated radial bearings

that this is considered LOW SPEED. Further down the page SKF says :

"SKF recommends the following grease fill percentages for bearings:
100% for LOW SPEEDS...."

********* and Kluber make the EXACT same recommendations. And by the way, these EXACT figures are well known since before WWII. I have detailed service instructions for MP4 Jig Borer manufactured in 1932-34 with the exact same recommendations.

There is much more to talk here about types of greases, how to select the speed factor, how to estimate the average loads, what's a bearing and what's a housing etc but I believe those exceed the parameters of this sub-forum.

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MattiJ said:

I have also bitched about this earlier. Kluber NBU-15 and 15% packing work for Dn 50mm 30000RPM spindle so it obviously has to be best also for turtle-speed WW2 era 1200 rpm mill spindle with tapered rollers.

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Oh, yes ! You should've spoken with my father. He was a maintenance manager for a huge plant with one or two machines and he loved Kluber and their endless marketing BS. I use NBU 15 in 1-2Kw Chinese router spindles and it works fine. I don't like the price and I switched to an SKF grease. Clearly better - lower current on idle, less noise and lower temp. I've already have spindles which past their NBU 15 life - we'll see how long they last on SKF. To use NBU 15 ( not an EP grease ) in a MAHO 1000 spindle is simply misguided.

hanermo said:

1. Your arguments are compelling ..

2. but actual usage and real-life experience on 100k+ machine tools in service does not support that low rpm needs more grease.

3. Modern VMCs use high speed spindles 8k and up, some to 15k or up.

4. Generally none, that I know of, fail from using low rpm in service.
Some use oil, oil mist, and some use greased spindles.

5. I believe brother uses greased spindles, for example.
Brother is known for high speeds, excellent spindles, and long life, and no cautions re: low rpm as far as I am aware.

The kluber fill quantity link is here:
Bearing Lubrication Procedures: Part 2—Ensuring Proper Fill Quantity - Kluber USA / Canada Blog

It supports your point that for low speed use under 200k critical speed, a high pack of 90%-100% is appropriate.

6. BUT the grease (Kluber Isoflex 15) is also used in low speed apps like heavy textile machinery, with heavy rolls, that will *never* run at 5000 rpm, much less 8000 rpm+.
More like a few hundred rpm.
7. The textile machinery is mentioned by kluber.

8. Thus, for AC high precision bearings, in machine tools as the app, the low pack of 30% seems right--

9. and 2M+ machine tools in use in the world are not commonly failing under low rpm- when lubricated to 30% +/-.

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1. Those are not my arguments. Those are the arguments of major bearing manufacturers with long experience and in possession of real data not " My Maho run on NBU 15 for 3/5/7.. years and no problem".

2. Well, the bearing manufacturers think otherwise. How did you reach your conclusion ? Do you have any hard data to back it up ?

3. Sure. Different game. Large bearings, large speed factors, much less grease

4. "Generally none that I know of" means nothing. Toyota ( major manuf here in RSA ) has a different "that I know of". It all depends on a ton of things and specific conditions. Also, the bearings might be getting hurt but it's a slow process and the user is unaware of it. You are not disassembling a spindle every day to see how it's doing.

5. Brother is a fine manufacturer but I couldn't comment - never took apart one of their spindles. Sealed bearings or bearings inside narrow housings can run on much less grease. Also, too much grease at high speed is far worse than 30% at low speed.

6. Kuber recommended NBU 15 for almost ANYTHING as long as it wasn't life threatening. In most applications the bearing loads are FAR less than one thinks and simple hand cream will do fine. When it gets serious like the outer front wheel of a heavy truck/bus fully loaded and cornering, Kluber is nowhere to be found. ( by the way, for certain stuff hand cream is actually hard to beat. Bearings, I mean. )

7. Everything is mentioned by Kluber. But Shell Gadus 220 still beats the shixxx out of their fancy greases. And for 1/10th of the price.

8. It depends. Speed factor, housing type, cage type etc.

9. Why would they ??? Who said they would ???? If the grease stays there and it's not getting too hot, 30% is more than a bearing can actually use. I surely would prefer to have a good reserve of grease there if things get hot but that's me. Toyota simply removes the spindles at a certain number of hours and send them to the manufacturer for replacement. I can't afford that, the spindle bearings on my Maho can not be replaced and I don't have the spare cash to buy a new spindle. I'll try get as long a life as possible from what I have.

By the way, you do know why low speed needs more grease - the physics reasoning in other words ?

Well I did some checking by calling SKF Tech support and talked with them for about 20 minutes. They said the grease pack depends on application of the bearing. They said one of their new enclosed bearing as in a sealed or shielded bearing, that 80% of their bearings use 30% pack, Also if the bearing is inside a cartridge and depending on application they recommend less grease down to 30%. They said if the bearing is used in a high contamination area they use more grease and in some applications they may use on open bearings 80 to 100% pack. Which totally blew my mind! Reminds me of the older Blanchard grinding machine and they used to use tons of grease on their ways so the grit and coolant could not move under the ways as it was used as a seal.

The SKF Engineer today said in their manuals you can read 100% and 30% depending on application of the bearing, what kind of bearing and where it's mounted.

As I stated I took a SKF class 30 years ago at SKF and that instructor told me 30%. As I think about it way back then I was the only student that took the class of about 50 that worked on machine tools. So I would premise my questions and he answered me from that perspective. "Machine Tools" So he told me 30% because the majority of machine tool spindles are enclosed inside a quill or "housing" the term today's engineer used.

I also called J L Lucas Precision Remanufactured Machines | J. L. Lucas Machinery Company, inc.

I spoke with their spindle rebuilder and company President. They said because they have a huge reservoir in the casting they use 80 to 100% pack of Mobil EP-2 Grease and as they test run the 715 RPM & 900 RPM spindles for 4 hours that grease "flings" out into the the cavity and the temp peeks and goes down. They also have a terrible problem with grinding grit contamination once their superior guards fail after poor maintenance or years of use and they never replaced them with new.

They said they expect that spindle to last 10 years of 24 hour a day running. Blew my mind as 2 years ago I rebuilt a Besley double disk grinder and I used the Isoflex grease because the owner of the machine told me to use it. Followed the Grease MFG recommendation spec of 25% and it worked. I would have used Mobil 32. The machines owner printed out the Isoflex spec to use 25%. I would have packed it 30% using the Mobil grease and sure it would)have worked as this machine may only run a week a month if that much. (I filled it by eye and didn't weigh or measure the amount. So it may have been more or less.)

As SKF told me today every application is different and both points are right. So Alex is Right and I am right. Depending on Application.

In my 50+ year career I have never packed a Machine tool spindle that full as MachTool and others probably haven't. We all need to relax and be more friendly as it sucks coming in here and have walk on egg shells when you offer an opinion that differs from Alex's.

I would never give the members bad advice. I have had a successful career using my techniques as others have had using their's.

Rich

In the economics of rebuilding a spindle, the initial cost of the grease is not a deciding factor...

I sometimes think most applications are not very grease sensitive and smashed bananas would work. I'm not sure any grease is going to protect you from grinding grit.

I've designed and built a number of high speed spindles (40K rpm and higher) for specialized applications. While some greased ball bearings are rated for this, whenever possible I prefer oil lubrication and un-shielded bearings. It is easy to make an oil trapping labyrinth on the spindle flanges and to fill the volume between the bearings with oil. For the same project I was as well using Dumore grinder spindles (Series 57) modified for oil lubrication by adding an oil fill nipple on the body and a couple of grooves in the flanges.

In my amateurish opinion, housing and spindle roundness, care of installation (no tipping races or gouging material out when inserting), balance of the rotating assembly, and initial cleanliness and in-use grit protection are all much more critical to spindle life than what percentage and specific brand of grease is used.

Oh, and don't run the dang thing into a vise. Or table. Or operator.

Cancel that on the operator, they're squishy and will protect the spindle.

Milland said:

Cancel that on the operator, they're squishy and will protect the spindle.

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LOL! Most especially the more highly opinionated ones that keep changing their position until they b'lieve they've found a well-supported place to stand!

FWIW-not-a-damned-thing-department, I'm on the "oil, rather" side whenever it is at all practical. Compare two VERY similar machines - Hendey T&G (greased spindle bearings) with Monarch 10EE (oiled), f'rinstance.

OTOH, all-too-often, it just isn't actually practical, so...

Monarchist said:

LOL! Most especially the more highly opinionated ones that keep changing their position until they b'lieve they've found a well-supported place to stand!

FWIW-not-a-damned-thing-department, I'm on the "oil, rather" side whenever it is at all practical. Compare two VERY similar machines - Hendey T&G (greased spindle bearings) with Monarch 10EE (oiled), f'rinstance.

OTOH, all-too-often, it just isn't actually practical, so...

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I'm not familiar with the 10EE but one thing I wish it was done more often was to have the spindle bearings lubrication isolated from the headstock gears. It's the rubbish from the gears which takes out the spindle bearings on a lathe. There was a lathe ( Weiller ??? ) which ran in grease packed bearings. I wonder how well it did.

I had a Romi that was built that way. Circulating oil for the gear box, but the spindle bearings were grease packed with a labyrinth seal on either side.

ewlsey said:

I had a Romi that was built that way. Circulating oil for the gear box, but the spindle bearings were grease packed with a labyrinth seal on either side.

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How did it do ?

Milland said:

In my amateurish opinion, housing and spindle roundness, care of installation (no tipping races or gouging material out when inserting), balance of the rotating assembly, and initial cleanliness and in-use grit protection are all much more critical to spindle life than what percentage and specific brand of grease is used.

Oh, and don't run the dang thing into a vise. Or table. Or operator.

Cancel that on the operator, they're squishy and will protect the spindle.

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Milland I would never call you an amateur with your experience in machine tools.

Richard King said:

Milland I would never call you an amateur with your experience in machine tools.

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Jeez, Richard - ya' got me blushing!

AlexO said:

By the way, you do know why low speed needs more grease - the physics reasoning in other words ?

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I don't - why is that?

AlexO said:

How did it do ?

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Probably just fine, like every other Romi.

Conrad Hoffman said:

I sometimes think most applications are not very grease sensitive and smashed bananas would work. I'm not sure any grease is going to protect you from grinding grit.

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When helping my neighbor replace his tractor wheel (I was 9yrs old), the bearing fell off and landed in the dirt. He picked it up and put it back on. When I asked him if we shouldnt clean it out and repack it, his comment was "the grease will grease before the grit will grind."

Now I dont follow that advice myself, but as a funny anecdote it works just fine. I suppose I would never know the difference between 25% or 30% in a bearing, but I know there are people who care. Thanks for the advice.

Charles

Charles