# Spindle Bearing Question



## astjp2 (Nov 28, 2015)

So I am planning on having to replace my Rockwell 11 lathe spindle bearings.  The originals are available at $541 each for the Timken 387-90043 ones.  I can find non precision 387A bearings for like $50 each.  Is it worth spending 10 times the amount for a hobby lathe?  My thoughts are that the modern standard bearings are about 5 times the precision that the older bearings were.  What are the thoughts of the tribe?  Also what should I be looking for in the preload?  I know that Rockwell did not publish the specs, so I was thinking that about 40~60 inlbs would be about right.  Tim


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## Uglydog (Nov 28, 2015)

1. Error is compounded. That is a little bit of run out from the spindle, a little bit of twist in the bed, a little bit of tailstock offset, etc. This can all add up to be considerable. Reduce the error at every opportunity and you'll be able to do some very nice work. Yes, she is only a hobby lathe, but this doesn't mean that she and you can't do some great work together.

2. I don't know how your spindle is designed, nor do I know the specs. Consider tightening her up until you feel a little drag and then loosen her up just a little bit. 

But, then I'm still in learning mode on both points. 
Daryl
MN


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## TommyD (Nov 28, 2015)

I guess it depends on the TIR of the bearings and what you find acceptable. Have you looked elsewhere for the Timkens or do they cross reference with another bearing company? Old bearings were pretty accurate, I had a few companies in my area that made bearings....all gone now.

Sorry, I can't help on the preload.


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## astjp2 (Nov 28, 2015)

The spindle bearing are tapered roller bearings on the chuck end, with a ball on the other end.  TIR is not my problem, they seem to be really stiff/bound up...I am just thinking that I need to get new ones here before I tear down the head, or I will be a few more years on this lathe.  Tim


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## 4GSR (Nov 28, 2015)

I would tear down the headstock and check out the existing bearings for condition before buying any replacements.  What I would do is, if the bearings need replacing, is ask for a class 3 precision taper roller bearing.  This would be far better than your standard off the shelf quality of tapered roller bearing.  And the price may be high but not $541!  Class 3 precision will be unnoticed to us H-M.


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## astjp2 (Nov 29, 2015)

I also found this number on the forum, but I am not sure what bearing it is.  Tim

New Departure
Inner - 3209
Outer - 99509
Sealed
Special code X3 (indicates precision bearing)


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## TommyD (Nov 29, 2015)

New Departure is a bearing manufacturer, they used to be located in Bristol, CT but have since moved to Sandusky, Ohio. They may have made your bearing, the codes are sizes of the races and sealed means it had a seal to keep in grease and garbage out.

You may only need to repack the bearings with grease. If you are careful you may be able to gently pry the seal out, stay away from, especially, the id lip. They are usually only rubber where the body out to the od is rubber clad steel. I apprenticed for a company that made bearing seals for almost every bearing company there was in the early 80's.


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## Kernbigo (Nov 29, 2015)

I did a lot of spindle rebuilding and some of the comments are write, take it apart  and insect the bearing timkens are rugged bearing they may just need cleaning and reassembled.You can set them up with a indicator checking the end play, start with .001 warm and if that is ok you may be able to go as tight as .0005. I f you  can run oil instead of grease also, a drip oiler system.


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## 4GSR (Nov 29, 2015)

astjp2 said:


> ...snip...The originals are available at $541 each for the Timken 387-90043 ones.  I can find non precision 387A bearings for like $50 each. ...snip.....  Tim



After reviewing the assembly of the headstock on your lathe.  The bearing in question appears to be a double row Timken NA series bearing.  Which means you cannot use two single row 387 bearings. Will not work in the space the double row bearing is taking up.  So your are back to buying the $541 double row bearing.  If you insist on buying the bearing, ask what precision this bearing is.  If it is "00" or "0" precision, ask if they have it available in class 3 precision.  May save you a few bucks!
On the other hand, do what Kern said above, clean up the existing bearing and reuse.  Most of the time, these bearings don't see damage unless they have been neglected over the years.  Long term storage of a machine tool is it's worst enemy, if it has not been prepared for storage.  Condensation sets in causes galvanic corrosion between the rollers and races, causing premature failure of a bearing.  
Word of caution when tearing down the spindle assembly,  pay close attention of which cone goes to each side of the double cup race.  Also, there may be witness marks to indicate alignment of the cone to the cup and or to the spindle.  And what ever you do, do not mix new bearing cones to a old cup, this will cause almost immediate bearing failure!

The rear bearing on the spindle is a standard 200 series double row bearing.  Probably a class 3 or P4 bearing, going with the newer bearing standards.  You should be able to get that one off the shelf with double seals or shields.

Ken


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## astjp2 (Nov 29, 2015)

Ok, I am now confused...it looked like all 387 series bearings were single row...These are the same as the ones in my dana 60 carrier, I usually set them to something like a preload of 9 ftlb of running torque.


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## 4GSR (Nov 29, 2015)

astjp2 said:


> Ok, I am now confused...it looked like all 387 series bearings were single row...These are the same as the ones in my dana 60 carrier, I usually set them to something like a preload of 9 ftlb of running torque.



It's the same cone, BUT it is matched at the factory to the double cup, making it a NA series bearing.  The bearing used in your Dana 60 carrier is a much sloppier bearing compared to a "0" precision tapered roller bearing.  In fact the arrangement of the Dana carrier has the cones back to back vs face to face as on the lathe spindle.  Both are treated different when setting the preload on the assemblies.  The NA series double row bearing has the preload set at the factory.  It don't matter how tight you tighten the bearing lock nut, the preload stays the same.


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## 4GSR (Nov 29, 2015)

How about posting a picture of all of the bearings pieces along with the spindle to let us know what was on the spindle originally?  Very good chance someone has already been into the headstock and did their thing.


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## astjp2 (Nov 29, 2015)

I have not taken mine apart yet, I am still scraping my carriage and crossfeed because my lathe was worn pretty good and also required a new bed.  Tim


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## 4GSR (Nov 29, 2015)

I wish my 14" Rockwell lathe had Timken bearings.  It has a special 3215 double row bearing made to a higher class of precision.

BTW- I notice someone replied to your thread on the Rockwell Lathe group saying they use two single row Timken bearings with a spacer, not a double row as I had mentioned.  My apology for being incorrect.  Ken


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## astjp2 (Nov 29, 2015)

Ken, I am glad you pitched in your experience.  I was looking at the double row bearings too, but the part numbers and drawings were not showing them.  I still don't know what bearing tension is supposed to be, is there a backlash or should I have some preload and running torque.  I know that some tapered bearings run a preload, we have them on ballscrews on some mills at work, others have compensation built in the software for the backlash.  Our old lathes get hot, does the spindles expand enough to need to be in tension?  The manual says drag and then backoff the jam nut 10*.  Maybe I am reading into this too much, but if I have to drop $1080 in bearings, I need to have it right the first time.  Tim


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## 4GSR (Nov 29, 2015)

Tim,
In all of the readings out of the Timken bearing books I have, for that bearing arrangement, they say nothing about how much preload to put on a bearing. They talk about fitting practice, bearing bores and shaft OD's.  I was always taught to tighten the bearing to about the torque of 9 ft/lbs as you mentioned for this size bearing.  Run the spindle until it get hot, if it does at all, let it cool down.  Go in and back off the bearing nut, then snug hand tight and secure.  Run again, if temperature is ok, should be good.  Temperature should be warm to touch by hand, no more than 100 deg F.  That would be at 500-700 RPM.  Even at max RPM, you should still be able put your hand on the headstock and not be hot.   Last, run a tenth's reading indicator, check for excessive runout.  My guess, runout, slop in the bearings, linear movement should be less than .0002" in any direction.  May have to come back later and readjust the bearings, especially if you start getting abnormal cutting from turning, facing off or parting off.


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