Spindle Bearing Question

[astjp2]

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

 

[Uglydog]

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

 

[TommyD]

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.

 

[astjp2]

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

 

[4GSR]

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.

 

[astjp2]

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)

 

[TommyD]

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.

 

[Kernbigo]

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.

 

[4GSR]

...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

 

[astjp2]

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.