Lubrication of FAG super precision bearings

Lubrication and maintenance are important in order to achieve reliable function, an adequate operating life, wear-free running and a low vibration level in FAG super precision bearings. An essential precondition here is the formation of a lubricant film that separates the rolling contact partners at their contact points.

In order to achieve this:

  • It must be ensured that lubricant is present at all contact points and at all times.
  • The lubrication method defined must be appropriate to the required speed.
  • A lubricant with the correct characteristics must be selected.

It should be determined as early as possible in the design process whether bearings should be lubricated using grease or oil. The decisive factor is the maximum operating speed required.

In consideration of the FAG bearing as a complete system, the lubricant plays an important role. The decision between grease and oil lubrication has a significant influence on the system costs.

Greases for FAG super precision bearings

An overview of suitable FAG greases for super precision bearings is shown in the table.

Greases Designation
L252 L055 L298
Identifier according to DIN 51825 KHCP2/3K–40 KPHC2N–30 KPHCP3P–40
Thickener Lithium complex Lithium Polycarbamide
Base oil PAO and ester oil PAO and mineral oil PAO and ester oil
Base oil viscosity at +40 °C 25 85 55
+100 °C 5 12.5 9
NLGI class 2 to 3 2 3
Maximum operating temperature
°C
80 80 110
Speed parameter n · dM
min–1 · mm
2000000 800 000 1300000
Specific mass
g/cm3
0.94 0.9 0.86
Application as high speed grease high pressure grease high temperature grease

L252

High speed greases have been developed for operation in spindles for machine tools. This class of greases includes the FAG high speed grease L252. This grease is the current standard grease for spindle bearings, due to the achievable speeds and the suitability for the typical temperature range in machine tools.

L298

L298 is a high temperature grease that, due to its higher base oil viscosity, is used at continuous temperatures up to approx. +110 °C.

L055

L055 is a high pressure grease that has proved extremely effective in the end bearings of ball screw drives, in indexing table bearings and for example also in tailstock lathe centre bearing arrangements.

Standard greasing

In the case of sealed bearings supplied with standard greasing, the grease grade is not stated on the packaging or on the bearing. Open bearings supplied greased with high speed grease are identical by the application-oriented grease group GA21 on the bearing and on the packaging. In the case of these bearings, Schaeffler Technologies reserves the right to change the grease grade without a change in designation on the precondition that the grease fulfils the requirements of the application-oriented grease group GA21 in relation to speed capacity, operating temperature and life.

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