# Please educate me on tapered spindle bearings for mills



## richl (Sep 20, 2017)

As the title suggests, I am woefully uninformed about tapered spindle bearings. I need to replace the bearing in my mill a 1956 south bend ram head, 1 hp, 1800lbs sorta a Bridgeport model 1 copy... her highest speed is 3750rpms, I never checked, it does seem to move though...

After I have studied the parts breakdown, and attempted a couple trial breakdowns, I will finally pull the machine apart...
As for spindle bearings, I am pretty sure I will not find any information other than what I have now. I am hoping to find the original numbers still stampede on the bearings... what about ratings for the bearings, my lathe came with class 5 nsk tapered bearings, will the numbers on the bearings indicate that kind of information or is that something I need to let the bearing dist know.

I am watching you tube videos on guys doing spindle bearing on Bridgeport machines, any chance that will relate to what I need to do?. I am curious on preloading and install of the direction of the bearings, is it common for these to need to be installed very specifically?
Will a heavy hydraulic be required or suggested?

Lots of questions, and I have more. I want this to go as smoothly as possible

Thanks for all help and suggestions.
rich


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## Ulma Doctor (Sep 20, 2017)

Hi Rich,
bearings are not really as difficult to get as you may imagine.
the first thing is helpful is the numbers off the bearing cup (race) as well as the cone (the part that has rollers)
with that information you or a bearing house could look up the part number by those numbers inscribed.
if for any reason you don't have numbers on the cup and cone, you can reverse look up the correct bearing by doing a bit of measurement.
you'll measure the inside diameter of the cone, the outside diameter of the cup, and the assembled distance from the cup outside thickness to the cone outside thickness.
you have already ascertained that the class is 5 .
do the measurement in millimeters and inches if possible, if you must measure.
a lot of old tapered roller bearings are imperial on old machinery, but they may be metric replacements if they are manufactured by NSK.
NSK does make Imperial bearings as well as Metric bearings, it would be a good idea to get all the info you can as far as measurements.

anything you watch on bearing replacement will aid in your familiarity with the process.
it may be a bit different in your mill, but it never hurts to gain knowledge.

i have not changed the spindle bearings on your mill, but i imagine the process is not rocket science.
this is not the Gospel, but how i approach tapered roller replacement.

spindles often use tapered roller bearings that oppose each other on a shaft.
usually there is a nut of some sort that applies pressure to one end of the assembly (sometimes both ends will have nuts possibly with seals)
the nut is cranked down and the clearance between the bearings is reduced to a preload point, then backed off and set to zero clearance.
lubricate the bearings with oil or grease as the South bend intended.
it would be safe at this point to switch to synthetic grease, if you choose to go that route.
run and give a feel test after a few minutes, or sooner if there are any funny sounds

a lot of spindle bearings come off the shaft easily, i can't say specifically on your mill, but they can be manually removed.

have a look at it this way, it's already messed up- you can only make it better


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## jakes_66 (Oct 25, 2017)

Rich,

I'll be watching your progress on your SB VMM.  There are not many of these machines in use, so I'm very curious to see what you find.

I'm not sure what you'll find for spindle bearing lubrication.  If it is in fact grease, it would be a perfect time to switch.  There is a spindle/quill oiler on mine that the Owner's Manual recommends South Bend Cat. No. CE1600 oil.  I have been using spindle oil I bought from Blue Chip Machine Shop.  The manual also mentions a small oil drain hole in the back of the quill for overflow to prevent the spindle from 'running hot' from excessive oil.  There's an allen-head screw in the hole you're supposed to open and allow to drain to maintain the correct level.

Keep us posted!

-Jake


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## Silverbullet (Oct 25, 2017)

There are YouTube's by h&m I think , they have been rebuilding Bridgeport machines for years . Some good footage of complete machines even the oiling system. 
I have a couple used mills that ill be upgrading in the future , even a new uncrated HF drill mill. Ill be adding an oiler system to it just to protect it from as much wear as possible. Real mechanics doing the work not staged , the shop background shows the real deal.


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## Dabbler (Oct 26, 2017)

I'll second the H&M videos - they taught me a lot.


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## richl (Nov 27, 2017)

Nice, the videos are great. Not sure how much they will help with my machine, excellent level of detail


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