Best method to repair a Spherical OD journal bearing (also called babbitt sleeve bearing)?

[Mech5656]

Hello All,

We have a spherical type babbitt sleeve bearing that is oversized on ID. The clearance between shaft OD and bearing ID should be 0.007". But we have 0.015". The OD is also undersize. Since the OD is spherical, it is difficult to repair.

In order to fix the OD, we have two options:

-Install shims between the split lines of bearing and restore the OD.
-Add extra Babbitt and stick it out from the split line to restore the OD size. (as shown in picture).

Which one do you recommend based on your experience? Can you recommend another method instead of these two?

 

[TugboatEng]

I usually use hard chrome to build up diameters on parts with sensitive dimensions. Because you need to refinish both the OD and ID, thermal spray. Maybe a less expensive option. It won't be too much trouble to restore all of the original dimensions of this part. I can recommend one company that is able to do both the hard chrome and babbit application as well as machining to the finished product in house to save shipping the part too many locations.

I would generally recommend against shimming the housing to increase the OD. I doubt it is spherical anymore and shimming it will reduce its roundness even further.

 

[JS_]

Curiosity, is getting the better of me.....

How did you come up with the .007 vs .015 for the Inside Diameter?

How did you check the fit on the outside diameter?

If it really is out of spec.. Why not make the supplier fix the issue?

 

[Mech5656]

TugboardEng:

Thank you for providing your feedback. Can you explain why roundness is important and what is the max out of roundness we can have? This is a 12" OD bearing so we should have slight room out of roundness. Can you please share the vendor name?

JS:
I came up with those numbers like this:
This is just an example and I dont have the exact numbers.

Shaft OD: 5.000
Sleeve bearing bore ID: 5.007
The clearance is 0.007" between the two.

This is an example. I We are measuring clearance of 0.015" but recommended is 0.007"

We have a micro meter that can measure the outside diameter of the bearing.

The supplier is suggesting two options stated in original post.

 

[JJPellin]

Does the bearing housing have a jam bolt coming down from the top, locking the bearing in place in the lower housing? If so, the fit between the bearing OD and the housing is less important. You could lap the bearing into the lower housing to restore the contact and re-babbit the bore. Of course, the best repair is a new bearing.

Johnny Pellin

 

[JS_]

I will use this for an example:

A 4" journal turns at 100 rpm , the circumference is moving at 100 feet per minute......

Out of an old book on journal bearings

Under 600 feet per minute (Diameter X .001) + .001 = recommended clearance

Same book

over 600 feet per minute (Diameter X .002)+.002 = recommended clearance
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If the completed bearing is a wrong have the vendor make you a new one....

That would be a re-pour and shim before machining

Depending on how much RPM and loading.

I have seen bearings like that put into service....

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If it is out of round it is possible that the bearing was clamped too tight while machining.

 

[TugboatEng]

If the spherical OD is not round any rotation of the housing would contribute additional misalignment to the shaft.

This shop has the ability to do babbitt and chrome. I am assuming they can grind a spherical OD. I'm only a customer and they have satisfied my requirements.

http://www.bbcmachine.com