How Should These Spindle Bearings Be Lubricated? Also, What Bearings to Buy?

[ChandlerJPerry]

I'm also pretty perplexed about it. I could be thinking about this incorrectly, but wouldn't it be possible to swap to an angular contact bearing by assembling the two bearings and spacer on the spindle with thrust directions facing each other, and then shimming under the snap ring to apply appropriate preload?

At that point it appears to me that the bearing assembly would be held captive into the quill by the end nut. The lock nut at the top could then be adjusted to basically be finger tight and locked in place with the tabbed washer as to not place any force on the lower angular contact bearing.

I could be missing something obvious here. But in the perfect world of my mind it makes sense lol.

If that's even a correct line of logic, I also have no idea if any performance gains would be realized in terms of accuracy or rigidity.

 

[Pevehouse]

To answer your question, I would say grease. I would also recommend using Kluber NBU 15. This grease is expensive but has some desirable characteristics in applications like this. The only downsides are price and compatibility with other lubricants. By the way, I usually order not only enough for what I’m working on but also keep some on hand as it is a good solution for problematic lubrication situations you may encounter in the shop.

You only need about 30% fill on the bearing. Over greasing can cause heating.

Interesting that the bearings themselves are single row, angular contact bearings. They are probably ABEC 7 or 5. I try to use the higher precision bearings as you gain a little tighter tolerance and a little smoothness. The contact angle on these bearings is 40 degrees. This is unusual. Most milling machines will have 15-degree contact angle with an inner and outer spacers to regulate preload and to also achieve stiffness. The 40-degree contact angle can take a much higher axial load.

One machine that I’ve worked on that had this type of spindle setup was a Cincinnati Bickford Super Service drill. However, instead of having a center ball bearing it had a long, bronze bushing to stabilize the center of the spindle. The bearings themselves were angular contact ABEC 7 P4 bearings with 40-degree contact angle. This set up can handle a higher axial load that would be encountered in drilling, but it gives up some higher speed capability. The preload was adjusted by a single nut tightened enough to remove most of the deflection but not so tight so that it developed heat. Heat in a quill will cause it to expand and can cause stiffness or even seizure of the quill if it is close enough tolerance.

I would probably go with NSK, a good quality Japanese bearing. These days you want to pay attention to a good brand and order from a reputable source. I often use EZ Bearing and talk to Darrel. Motion Industry would also work.

Good luck

Just curious, I’m in the process of replacing my taper roller spindle bearings and have wondered what would be the best grease to use. Would the Kluber NBU 15 be the best choice for taper bearings as well?

 

[Ischgl99]

I'm also pretty perplexed about it. I could be thinking about this incorrectly, but wouldn't it be possible to swap to an angular contact bearing by assembling the two bearings and spacer on the spindle with thrust directions facing each other, and then shimming under the snap ring to apply appropriate preload?

At that point it appears to me that the bearing assembly would be held captive into the quill by the end nut. The lock nut at the top could then be adjusted to basically be finger tight and locked in place with the tabbed washer as to not place any force on the lower angular contact bearing.

I could be missing something obvious here. But in the perfect world of my mind it makes sense lol.

If that's even a correct line of logic, I also have no idea if any performance gains would be realized in terms of accuracy or rigidity.

No, a snap ring is too flexible to provide preload, there needs to be a locknut with a flat face pressing against the bearing. If you put two ACBs in the lower position, the upper bearing would need to provide the preload still.

You could increase the rigidity by mounting the bottom bearings in tandem or back to back and have the upper bearing provide the preload. I’m not sure if the smaller upper bearing would be able to provide sufficient preload to two bearings mounted that way before getting overloaded, but that is an interesting thought.

 

[tailstock4]

I agree with Ischgl99. Don’t go the snap ring route. It would have way too uneven of a preload on the bearings. You could actually lose ground in terms of runout. As far as the tandem arrangement, I have a Toolmex lathe with a tandem DBD arrangement of angular contact bearings upfront then a double-row conical bearing in the center, and a deep groove ball bearing in the rear. This makes for a very rigid but free turning spindle.

Having said all that, I believe in your case I might well try to clean up the bearings and reinstall them. (Hopefully you marked the race position on the quill housing and spindle – this could be relevant depending on how the taper was ground.) If you’re unhappy at that point and depending on the condition of the rest of the mill, I might consider new bearings and upgrading their precision. You may still end up needing to grind the taper.

One thing that is good to remember, especially on precision bearings, is that it is a three-part exercise. One is the precision and quality of the bearings. Two is the quality of the installation (and there is more to this than many may think.) And third is the quality of the machine such as roundness of the bores, their alignment, etc. To get the best performance you really need all three.

 

[tailstock4]

Just curious, I’m in the process of replacing my taper roller spindle bearings and have wondered what would be the best grease to use. Would the Kluber NBU 15 be the best choice for taper bearings as well?

My answer would be “it depends.” Kluber NBU15 is a very good quality grease. It is long lasting and helps with cool running especially for higher speed, precision bearings. But as mentioned it is not cheap and it needs to be isolated from other lubricants. In the case of my Cincinnati Bickford drill, I already had the Kluber grease, the spindle bearings are isolated and have access plugs to add grease in the future.

I have Toolmex lathe that runs a tandem DBD angular contact on the front of the spindle and these are lubricated with Kluber grease. They are isolated from the rest of the headstock by a labyrinth seal and the intermediate conical bearing and back ball bearings are lubricated by headstock oil.

An example of where I don’t use it is a radial drill that uses taper roller bearings that gets a little bit of oil washout from the power feed’s way oil. It is a total loss system. In this machine, I just use a #2 good quality bearing grease. It is a relatively slow speed spindle that is easy to add grease to.

 

[ChandlerJPerry]

Well hard luck for me. Definitely getting disheartened with this among a few other things in the machine. I'm beginning to feel like I bought a lemon. An expensive, greasy, heavy lemon. Got to cleaning parts up tonight and found this.

The bearings were clearly not preloaded correctly and it's obvious that the lower angular contact bearing has been spinning on the spindle. The inner race has worn a groove into what looks like was a nicely precision ground surface once.




To loop back around to the bearing discussion, I did clean them up and inspect for further markings. I didn't see anything of note on the angular contact bearings. One of them has a "G" marking, and the other has an "H". I don't think they're of any real significance.



Interestingly the radial bearing has some unique markings. Some hand made electropencil marks that seem to show "WL-16", as well as a "P" and "E", all in the outer race.



Not sure if there's any significance to them. All I know is that from where I stand right now it looks like I've got a mill with bottom of the barrel bearings and a spindle that needs re grinding. Not sure where I could take the spindle, but it already sounds like a costly proposition to me .

 

[machPete99]

If if has worn evenly maybe you could wrap a piece of shim stock in there. I essentially did that on my Rockwell mill as it had excessive clearance around the bearings. I think I had to use 0.001 or 0.0005 shim stock. It runs fine with angular contact bearings and has less than 0.0005" runout.

On the grease: Its a bit expensive but Kluber IsoFlex NBU 15 is one of the better options, intended for mill spindles.

 

[ChandlerJPerry]

If if has worn evenly maybe you could wrap a piece of shim stock in there. I essentially did that on my Rockwell mill as it had excessive clearance around the bearings. I think I had to use 0.001 or 0.0005 shim stock. It runs fine with angular contact bearings and has less than 0.0005" runout.

So essentially you wrapped shim material around the spindle and then slid the bearing over it? That's not a bad idea.

The majority of the wear is on the face displaying the groove. I couldn't find any gouging on the actual OD of the spindle, however I think a more thorough inspection is warranted. I am thinking I can attach an indicator to the mill head and hold the spindle in my vise to try and sweep it. I could also clamp the spindle directly to the table, oriented vertically and use the knee to move it along the indicator path.

Unfortunately my lathe is also taken apart for...wait for it...spindle bearings! Previous owner ran with no oil in the bearings. So I can't use it as an inspection tool for the spindle. It feels like I really know how to pick my machine tools right now .

 

[Pevehouse]

So essentially you wrapped shim material around the spindle and then slid the bearing over it? That's not a bad idea.

The majority of the wear is on the face displaying the groove. I couldn't find any gouging on the actual OD of the spindle, however I think a more thorough inspection is warranted. I am thinking I can attach an indicator to the mill head and hold the spindle in my vise to try and sweep it. I could also clamp the spindle directly to the table, oriented vertically and use the knee to move it along the indicator path.

Unfortunately my lathe is also taken apart for...wait for it...spindle bearings! Previous owner ran with no oil in the bearings. So I can't use it as an inspection tool for the spindle. It feels like I really know how to pick my machine tools right now .

+1 on the shimstock , I have had to do this in the past as well. Works pretty well. Just don’t get frustrated with itt and give up. I have been bitten multiple times while learning about these old machines. Just have to make do with what you have till something better comes along. Thanks for the input from you guys on the grease. I’m gonna place an order for it in just a few minutes. Don’t mind spending the money since I now know it’s a good product

 

[Ischgl99]

Well hard luck for me. Definitely getting disheartened with this among a few other things in the machine. I'm beginning to feel like I bought a lemon. An expensive, greasy, heavy lemon. Got to cleaning parts up tonight and found this.

The bearings were clearly not preloaded correctly and it's obvious that the lower angular contact bearing has been spinning on the spindle. The inner race has worn a groove into what looks like was a nicely precision ground surface once.

View attachment 501968
View attachment 501969

To loop back around to the bearing discussion, I did clean them up and inspect for further markings. I didn't see anything of note on the angular contact bearings. One of them has a "G" marking, and the other has an "H". I don't think they're of any real significance.

View attachment 501970View attachment 501971

Interestingly the radial bearing has some unique markings. Some hand made electropencil marks that seem to show "WL-16", as well as a "P" and "E", all in the outer race.

View attachment 501972View attachment 501973

Not sure if there's any significance to them. All I know is that from where I stand right now it looks like I've got a mill with bottom of the barrel bearings and a spindle that needs re grinding. Not sure where I could take the spindle, but it already sounds like a costly proposition to me .

I believe the H and G are factory designations where the bearings were made.

I have never seen P by itself, usually it would be P and a number for the precision class. It doesn't look like something got worn off, so that is confusing. I haven't seen WL-16 either before, and nothing like it shows up in their nomenclature catalog.

For the wear on the face by the nose, is that the width of the gap between the inner and outer rings, or is the lip on the inner side of the face the width of the fillet on the bearing ring? If that is between the inner and outer rings and there is enough space for the inner ring to seat against, you don't need to do anything, but if there is not enough surface for the rings to press against, then it should get repaired. I don't know how much effort you want to put into this, but sending it out to get flame sprayed and reground would be the ideal fix, but using a shim as previously mentioned would be a good first step to try and see if the results are acceptable. Another option is an epoxy to rebuild the worn area of the shaft, but you will need a working lathe for that. I haven't used Belzona, but a customer did for worn parts and it seemed to work. https://www.belzona.com/en/products/1000/1221.aspx