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Hello Josh,

Some people use grease to apply while others use oil in bearings. From what I know is if most of the mechanical components are on the exterior part of the machine then grease is applied to avoid dripping while for inside of the equipment oil is applied. Should you want to provide a better lubrication for your bearing what would be the criteria and selection.
RM
I would say as a rough guide:
1 - Industrial machinery:
1A - Sleeve bearings - use oil
1B - Rolling Bearings:
1A1 - Rolling bearings with D*N > ~ 250,000 inch * RPM => use oil (grease would likely overheat)
1A2 - Rolling bearings with D*N < 250,000 inch * RPM => prefer grease since it is generally a simpler solution to install and maintain, no big leak issues or level-maintaining issues (but does need periodic greasing).
D*N = bearing bore diameter times speed. There may be slightly varying definitions using mean bearing diameter and slightly different limits as to where grease becomes ineffective. Higher-precision bearings with special cages can extend the viable range of grease lubricatation.

These choices are usually made by the OEM
RM
Hah, I think it's still helpful. Reading the values from the graph suggests the speed limit for oil lubricated bearing is generally more than 10 times as high as for greased bearing of same size at same load. More than 10x difference!

And yet according to SKF and/or ISO there is no need to distinguish greased bearing thermal speed limit from oil bearing (the greased limit that used to be in their catalogue has been removed citing iso)

http://maintenanceforums.com/e...611012993#3611012993

[shrugs and steps off of soapbox]
RM

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