PDA

View Full Version : Thorough cleaning of plain bearings i.e. "babbitt" / brass: recommendations?



Arthur.Marks
09-22-2013, 02:36 PM
I have a pulley from a backgeared lathe headstock with a "plain" bearing on the inside integral with a gear. This is so the gear can be un-coupled and transmit power through alignment with a set of reduction gears ("backgear") or be coupled and transmit power 1:1 ("direct drive"). So that is the scenario. The actual spindle bearings are angular contact and double-row cylindrical type. Anyway, at some point in this thing's history the oiling ports were mistaken for grease ports. When the bearings were later correctly oiled, the grease managed to migrate everywhere throughout the bearings and spindle including the "plain" bearing portion.

How would you thoroughly clean such a bearing? Wiping it clean with an oil wetted rag doesn't seem to rid the brass of the black residue completely. I can still wipe my finger across it and come up black. It just doesn't seem appropriate to submerge a plain bearing like this in a solvent tank. I have done it in the past with less critical surfaces, but I wonder if that damages the bearing -- as I understand it, plain bearings retain and soak in oil. Certain types are integrally infused with oil under pressure (Oilite?)... although this could be absolutely wrong for all I know.

:confused:
So what say ye? What is a correct way to clean a plain bearing without damage?
...wipe as good as is practical and run with correct lubrication in the future? Or...

Boucher
09-22-2013, 02:52 PM
I would, ".wipe as good as is practical and run with correct lubrication in the future."

CCWKen
09-22-2013, 03:06 PM
Oilite bearings aren't used for heavy loads or constant oiled points so I wouldn't expect them to be used except in idler gear or light load applications. Clean them up and oil them regularly. The oil will eventually wash the grease out any way. The black residue is probably metal particles from the shaft. You may want to check clearances. Could be that the bushings and/or shafts are worn beyond the service limit and need replacing.

Arthur.Marks
09-22-2013, 04:05 PM
CCWKen, this is the main headstock drive pulley. The "shaft" it runs on is the headstock spindle itself.

CCWKen
09-22-2013, 06:00 PM
Ok.... Should that make a difference in service limit? If it's worn, it worn. Some bronze bushing have clearance limit of .005-.006" but this one may be more. If you can live with clearance, so can I. :)

Arthur.Marks
09-22-2013, 09:19 PM
There is no perceptible play on the bearing fit, so I went with the conservative approach. I doused the whole thing with a fine mineral oil and cleaned everything twice over with a soft toothbrush. I'm not convinced the sludge is anything but, well, sludge. As evidence, I offer the thrust bearing cage pre-cleanup. :)
http://i771.photobucket.com/albums/xx357/Arrak_Thumrs/Schaublin%20items/102%20backgeared%20headstock%20maintenance/DSCN7495_zpsf687f4fb.jpg (http://s771.photobucket.com/user/Arrak_Thumrs/media/Schaublin%20items/102%20backgeared%20headstock%20maintenance/DSCN7495_zpsf687f4fb.jpg.html)

The spindle finish shows some minor difference from the area the plain bearing rides on vs. not. The wear, though, is minimal as best I can tell. So she's well on her way to being put back together. Thanks for the replies, Boucher and CCWKen. It is very helpful to get feedback on this kind of stuff.