Spindle Bearing Question

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.
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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.
 
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.
 
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
 
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
 
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
 
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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