GMN >> Ball bearings > Products > Spindle ball bearings > Technology > Lubrication

Lubrication

The correct choice of lubricant and method of lubrication is as important for the proper operation of the bearing as the selection of the bearing and the design of the associated components.

Grease lubrication

Grease should be used if...

• maintenance-free operation over long periods of time is desired,
• the heat generated is almost uniformly dissipated by the environment,
• low friction losses are required with bearings working under small loads and at high speeds.

Grease quantity

Theoretically a grease quantity of < 10% of the free volume of a bearing is sufficient for lubrication.
However a grease quantity of approx. 25% to 30% is recommended for most applications for reasons of safety and lubricant consumption.

 Standard values for the lubrication of GMN spindle bearings are available as download: "Grease quantity 618 + 619", "Grease quantity 60 + 62".

Running-in period with grease lubrication

In order to obtain an optimum lubrication effect and long grease life it is absolutely necessary to run a proper grease distribution procedure.
In this way the grease is displaced from the raceway and the base oil continuously supplied by the grease can build up the required oil film between balls and raceways.
Thereby full work, friction and operating temperatures are minimised.
This results in long grease and bearing life.

 For the execution of a proper running-in process a description is available as download: "Running-in process".

Grease manufacturers offer a multitude of greases suitable for high speeds.
The n x dm factor is a criterion for the selection of the grease taking into consideration bearing size and operating speed.

Standard greases

This table is available as PDF file "Grease lubrication".

Oil lubrication

Oil lubrication should be provided if...

• high speeds do not permit the use of greases,
• the lubricant must simultaneously serve to cool the bearing.

The most widely used lubricating methods are:

• Oil mist lubrication:
  The oil mist is produced in an atomiser and conveyed to the bearings by an air current.
  The air current also serves to cool the bearings and the slightly higher pressure prevents contamination from penetration.
• Oil-air lubrication (minimised lubrication):
  The oil is conveyed to the bearing in droplets by compressed air.
  The droplet size and the intervals between two droplets are controlled.
• Oil-jet lubrication (cooling lubrication):
  Considerable amounts of oil are carried through the bearing by injection, the frictional heat generated in the bearing is dissipated.
  The cooling of the oil is achieved e.g. with an oil-to-air heat exchanger.

Standard oils

This table is available as PDF file "Oil lubrication".