Lathe spindle checkup

[durableoreo]

I have a used 9x20. The original owner had installed tapered roller bearings and done a few other improvemements, so I assumed all was well. But this is the condition of the spindle bearings:



So I cleaned them up and re-installed. If I had new bearings, I would have used them but I have a job coming up so I needed it re-assembled for Monday. The shaft for the rear bearing was 34.991 mm, which is a 0.009 mm interference fit for the 32007X bearing. That's 4 tenths. Such a relief. I had read about the procedure and the importance of a proper fit for setting pre-load but had no way to make corrections, if the fit had been too tight.

Seems like spindle grease is a constant debate over the years. I was able to get some Kluuber Isoflex NBU 15, so I used that. The previous owner may have used the same grease. There was a lot of it in the dust shield inside the casting. After cleaning thoroughly, I put on gloves, squeezed out a 3/4" nurdle of grease onto the rollers and messaged it in, making sure all surfaces where whetted. The I applied CMD to the ID of the rear bearing and pressed everything together. Ran for 20 min at 1000 RPM with the mildest warming. Much quieter! If I apply about 50 lb force to a bar in the chuck (6" away from front bearing) I get about 0.001 of deflection but it bounces back to 0.000. Same in both directions, with no obvious dead zone. I'd prefer to have it as stiff as possible, so I may end up increasing the pre-load after a bit more testing.

 

[markba633csi]

Looks like some moisture got in there somehow- is that rust?

 

[durableoreo]

Looks like some moisture got in there somehow- is that rust?

I think so. Feels like it. But no trace of rust on the rollers, cage, or races. I think the lathe had sat for years before the first owner sold it. The rust may have developed then. But when I got it, I used it a lot, which probably broken the rust off and mixed it into the grease. Bits of rust have accumulated mostly where pressure is low---on the cage and the end of the rollers. When I cleaned everything up (IPA and an air gun) there was no sign of rust spots on the cage. All the rollers had tiny grooves and minor damage. I've already ordered replacements.

 

[durableoreo]

I'm second guessing myself on the sound, amount of grease, etc. This is 1000 RPM. Does it sound OK?

 

[markba633csi]

It's hard for me to tell- how does the spindle feel when you spin it by hand? Fingers are sensitive transducers

 

[Smithdoor]

I have a used 9x20. The original owner had installed tapered roller bearings and done a few other improvemements, so I assumed all was well. But this is the condition of the spindle bearings:

View attachment 480161View attachment 480162

So I cleaned them up and re-installed. If I had new bearings, I would have used them but I have a job coming up so I needed it re-assembled for Monday. The shaft for the rear bearing was 34.991 mm, which is a 0.009 mm interference fit for the 32007X bearing. That's 4 tenths. Such a relief. I had read about the procedure and the importance of a proper fit for setting pre-load but had no way to make corrections, if the fit had been too tight.

Seems like spindle grease is a constant debate over the years. I was able to get some Kluuber Isoflex NBU 15, so I used that. The previous owner may have used the same grease. There was a lot of it in the dust shield inside the casting. After cleaning thoroughly, I put on gloves, squeezed out a 3/4" nurdle of grease onto the rollers and messaged it in, making sure all surfaces where whetted. The I applied CMD to the ID of the rear bearing and pressed everything together. Ran for 20 min at 1000 RPM with the mildest warming. Much quieter! If I apply about 50 lb force to a bar in the chuck (6" away from front bearing) I get about 0.001 of deflection but it bounces back to 0.000. Same in both directions, with no obvious dead zone. I'd prefer to have it as stiff as possible, so I may end up increasing the pre-load after a bit more testing.

View attachment 480163View attachment 480164

The biggest problem with tapper roller bearings is most do not seal the bearings.
The bearings looses lubrication then loose the bearings.

Dave

 

[Smithdoor]

I have a used 9x20. The original owner had installed tapered roller bearings and done a few other improvemements, so I assumed all was well. But this is the condition of the spindle bearings:

View attachment 480161View attachment 480162

So I cleaned them up and re-installed. If I had new bearings, I would have used them but I have a job coming up so I needed it re-assembled for Monday. The shaft for the rear bearing was 34.991 mm, which is a 0.009 mm interference fit for the 32007X bearing. That's 4 tenths. Such a relief. I had read about the procedure and the importance of a proper fit for setting pre-load but had no way to make corrections, if the fit had been too tight.

Seems like spindle grease is a constant debate over the years. I was able to get some Kluuber Isoflex NBU 15, so I used that. The previous owner may have used the same grease. There was a lot of it in the dust shield inside the casting. After cleaning thoroughly, I put on gloves, squeezed out a 3/4" nurdle of grease onto the rollers and messaged it in, making sure all surfaces where whetted. The I applied CMD to the ID of the rear bearing and pressed everything together. Ran for 20 min at 1000 RPM with the mildest warming. Much quieter! If I apply about 50 lb force to a bar in the chuck (6" away from front bearing) I get about 0.001 of deflection but it bounces back to 0.000. Same in both directions, with no obvious dead zone. I'd prefer to have it as stiff as possible, so I may end up increasing the pre-load after a bit more testing.

View attachment 480163View attachment 480164

The biggest problem with tapper roller bearings is most do not seal the bearings.
The bearings looses lubrication then loose the bearings.

Dave

 

[durableoreo]

It's hard for me to tell- how does the spindle feel when you spin it by hand? Fingers are sensitive transducers

Feels good. Smooth, easy to turn. But it's somewhat noisy at 1000 RPM and very noisy at 2000 RPM

 

[markba633csi]

Like a roaring sound? That's ok

 

[durableoreo]

The biggest problem with tapper roller bearings is most do not seal the bearings.
The bearings looses lubrication then loose the bearings.

Dave

There is a dust seal on the outer faces of the headstock. It is a machine-finish part, flat, smooth, and round. It runs flush with the outside of the headstock. On the inside faces of the bearing, there is a non-precision sheet metal part that might be a seal but might be meant as a grease... reservoir? I'm not sure. I don't have enough experience to say. There's a lot of volume in there.