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Schaublin 135 spindle bearings assembly and preload procedure

avivz

Cast Iron
Joined
Jan 28, 2009
Location
Israel
Bbackground- I’m rebuilding Schaublin 135 lathe and at least one of the spindle bearings has to be replaced as it got rusted and seized (likely the lathe was standing for a long period outside or who knows). The rebuilding process is documented here if you are interested in more details:
https://practicalmachinist.com/forum/threads/schaublin-135-rebuilding-project-ongoing-thread.420934/

There is barely info regarding servicing the spindle and I figured out I cannot tackle this job properly before gaining more knowledge on the topic (both theoretical and practical). Spindle experts literally don’t exist where I live.

The spindle is currently disassembled and all the bearings are out.
From what I saw in few tutorials, it seems that the spindle bearing arrangement is quite typical. Check the pictures below. On the front end of the spindle:

Super-precision double row cylindrical roller bearing with tapered bore (SKF NN 3014 KTN/SP), then-
Super-precision double angular contact thrust bearing (I think it’s a back to back matched pair) – SKF 234414/SP

On the rear end- Super-precision double row cylindrical roller bearing with tapered bore (SKF NN 3012 KTN/SP).
Both front and back sets are secured with a lock nuts.

Schaublin’s service manual provides guidance on how to adjust the front bearing radial and axial play as shown in the picture below.
I want to make sure I don’t miss anything here, so here are some questions/assumptions to be confirmed:

  1. As the first bearing has taper inner race, reducing the thickness of the “oil retainer (distance piece)” will allow the bearing to go further on the spindle taper, hence expanding the bearing against the housing which will reduce the internal clearance and hence eliminate radial play, correct?
  2. Is it element #10 in the picture?
  3. Regarding the second part- “reduce the thickness of the spacing ring of the thrust bearing by the amount to be taken up + 0.001 to 0.002 mm for preload”- I assume they mean the amount of the pre-measured axial play, correct?
  4. By the “spacing ring- do they mean element #6 or #7 in the picture? Why the preload cannot be simply adjusted by further tightening the lock-nut?
  5. Regarding the procedure of determining the radial and axial play in general- when the say “determine the value of both plays…” do they mean that I should try to move the spindle gently back and fourth axially and radially respectively to see by the indicator if there is a free play?
  6. On the theoretical side- in such an application are the bearing usually adjusted for a negative clearance (preload) or zero clearance?
Thanks In advance,
Aviv.
 

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135-21.o68 is the distance ring IMHO
It is there to lock the innerring secure in position
Those dubble row rollerbearings do not have preload Always possitive play The contact surface of rolls is much bigger as that of balls
I always put questionmarks to those values of 0.001 - 0.0p2mm endplay If you look at all the tolerances which every element in this setup may have you cannot hold that tolerance over the full circumference IMHO
But anyway your spacer has to be ground extremly parrallel . I had a college stone those rings parrallel using a 0.0002mm indicator

And important

CLEAN

Did I say Clean ?
 
If I read the instructions a certain way, it seems like the spacer ring is supposed to be reduced in thickness (via their formula) to give zero clearance but no axial preload, starting number for the formula being radial clearance?
 
Interestingly the axially adjustable piece - via grinding - (135-021.068) is at the very *front* of the bearing stack. Is it somehow adjusting the radial clearance on the roller bearing as well? is the spindle slightly tapered in the area of the roller bearing, or is that just a trick of the light?
 
"By the “spacing ring- do they mean element #6 or #7 in the picture? "

Neither, I think. The spacer ring is barely visible in your picture, butted up against the *left* side of what you have labeled "5" .

Zoom in on the manufacturer's photo and inspect the section lines around the *inner* thrust bearing races. There's a bit in between the inner races that has a different angle section lines - it's a separate cylindrical spacer that is NOT called out with a separate designation. That's the adjustable element (again, via grinding) to set axial clearance.

Or so I suspect.
 
Interestingly the axially adjustable piece - via grinding - (135-021.068) is at the very *front* of the bearing stack. Is it somehow adjusting the radial clearance on the roller bearing as well? is the spindle slightly tapered in the area of the roller bearing, or is that just a trick of the light?
Yes. As I wrote, the roller bearing has taper inner race and the spindle also has taper at this location. So my assumption is that when you push this bearing towards the front end, it expands the inner race which reduces the clearance hence reducing the radial play.
 
"By the “spacing ring- do they mean element #6 or #7 in the picture? "

Neither, I think. The spacer ring is barely visible in your picture, butted up against the *left* side of what you have labeled "5" .

Zoom in on the manufacturer's photo and inspect the section lines around the *inner* thrust bearing races. There's a bit in between the inner races that has a different angle section lines - it's a separate cylindrical spacer that is NOT called out with a separate designation. That's the adjustable element (again, via grinding) to set axial clearance.

Or so I suspect.
Jim there is nothing between elements #4 and #5. It's just the spindle shaft itself which is barely seen in that picture. #5 is the cage of the right part of this bearing.
 
135-21.o68 is the distance ring IMHO
It is there to lock the innerring secure in position
Those dubble row rollerbearings do not have preload Always possitive play The contact surface of rolls is much bigger as that of balls
I always put questionmarks to those values of 0.001 - 0.0p2mm endplay If you look at all the tolerances which every element in this setup may have you cannot hold that tolerance over the full circumference IMHO
But anyway your spacer has to be ground extremly parrallel . I had a college stone those rings parrallel using a 0.0002mm indicator

And important

CLEAN

Did I say Clean ?
Peter, could you identify this element (135-21.o68 is the distance ring) in the actual picture of the spindle parts?
 
135-21.o68 is the distance ring IMHO
It is there to lock the innerring secure in position
Those dubble row rollerbearings do not have preload Always possitive play The contact surface of rolls is much bigger as that of balls
I always put questionmarks to those values of 0.001 - 0.0p2mm endplay If you look at all the tolerances which every element in this setup may have you cannot hold that tolerance over the full circumference IMHO
But anyway your spacer has to be ground extremly parrallel . I had a college stone those rings parrallel using a 0.0002mm indicator

And important

CLEAN

Did I say Clean ?

I didn't know 0.2 micron indicator exists...
BTW, what is a reasonable accuracy for ring parallelism in such application?
 
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I didn't know 0.2 micron indicator exists...
BTW, what is a reasonable accuracy for ring parallelism in such application?
Here is a picture of the one I had
I do not know for sure but IIRC parallel within 0.002mm But better is better
 

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For a while I figured this indicator was not working
I did not see anything moving when I pressed the plunjer
turned out the needle was so narrow and went so fast you did not see it
Only when I jacked up the table against the plunjer I did see the needle

Peter
 
"Jim there is nothing between elements #4 and #5. "

In the manufacturer's line drawing there is. Look close. The outer thrust bearing (ball) races touch each other. The inner races, in that line drawing, don't. There's a spacer there apparently.
 
"Jim there is nothing between elements #4 and #5. "

In the manufacturer's line drawing there is. Look close. The outer thrust bearing (ball) races touch each other. The inner races, in that line drawing, don't. There's a spacer there apparently.

I think I got your point. This is element #7, which is a spacer between elements #1 and #8.
 
By my guess it should be between 2 (not clearly marked in your photo, belive it would be 2) and 5. Between the two inner races. Reduce the thickness of that, and you reduce the axial play, which is what the text discusses.

My other head scratcher is how the inner race of the roller bearing section can increase in size, to reduce radial play. Not sure how that would work, the race is a fixed dimension?
 
Oh, got it. The stack-up in your photo is a bit jumbled. Yes, 1 is one inner race, 8 is the other. So you're number 7 is indeed the spacer in question that would be trimmed to change axial play.
 
Regarding the axial clearance of the angular thrust bearing, simply reading in procedure it seems to me that the starting number is the axial play which is measured on an installed spindle, to which you add 1-2 micron which gives you how much to reduce the spacer. With this interpretation, it seem they aim to -1 to -2 mounted internal clearance (preload). Any other opinions?
 
  1. As the first bearing has taper inner race, reducing the thickness of the “oil retainer (distance piece)” will allow the bearing to go further on the spindle taper, hence expanding the bearing against the housing which will reduce the internal clearance and hence eliminate radial play, correct?
Yes, kind of. You need to achieve the correct mounted preload. As bearings differ, that could mean your spacer (oil retainer..) needs to get thinner OR wider, depending on the bearing dimensions. You wont know until you start the assembly process which way you need to go.
  1. Is it element #10 in the picture?
Yes
  1. Regarding the second part- “reduce the thickness of the spacing ring of the thrust bearing by the amount to be taken up + 0.001 to 0.002 mm for preload”- I assume they mean the amount of the pre-measured axial play, correct?
Im not sure what they mean, that bearing should come ground to predetermined preload with a new spacer (the spacer between the two inner races is what sets this). Maybe they didnt back in the day, but you should not have to mess with that inner spacer. You can prove it by stacking it up in an arbor press and just putting a little pressure on it to see if it loads.
  1. By the “spacing ring- do they mean element #6 or #7 in the picture? Why the preload cannot be simply adjusted by further tightening the lock-nut?
#7, tightening the nut wont change the relationship between the inners/outers because #7 is holding them apart
  1. Regarding the procedure of determining the radial and axial play in general- when the say “determine the value of both plays…” do they mean that I should try to move the spindle gently back and fourth axially and radially respectively to see by the indicator if there is a free play?
Dont know why they are having you assemble fully to check play, its a lot of work and can damage bearings. Set preload on rollers mathematically, the thrust should come "right" just tighten up. Set capture and assemble once.. Even if you have to adjust the thrust you can figure it all out before assembly.
  1. On the theoretical side- in such an application are the bearing usually adjusted for a negative clearance (preload) or zero clearance?
Preload, yes.

There is a lot of bad information in this thread, and I mean no offense, but you are being lead astray by some of the comments here. In terms of spindles, this is a cakewalk, but all the fundamentals still apply, and if you dont know them its a steep and expensive learning curve.
 








 
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