Initial grease fill

Super-precision bearings operating at high speeds should have less than 30% of the free space in the bearings filled with grease.

Open angular contact thrust ball bearings for screw drives should be lubricated with a grease quantity that fills ~ 25 to 35% of the free space in the bearing.

Freshly greased bearings should be operated at low speeds during the running-in period (→ Running-in of grease lubricated bearings.) This enables excess grease to be displaced and the remainder to be evenly distributed within the bearing. If this running-in phase is neglected, there is a risk that temperature peaks can lead to premature bearing failure.

The initial grease fill depends on the bearing type, series and size as well as the speed factor A.

A = n dm

=speed factor [mm/min]
dm=bearing mean diameter [mm]
= 0,5 (d + D)
n=rotational speed [r/min]

The initial grease fill for open bearings can be estimated using

G = K Gref

=initial grease fill [cm3]
Gref=reference grease quantity [cm3] (→ Product tables)
K=a calculation factor dependent on the bearing type and the speed factor A (diagram 1)
Sealed bearings are filled with a high grade, low viscosity grease that fills ~ 15% of the free space in the bearing. They are considered to be relubrication-free under normal operating conditions. The grease is characterized by:
  • high-speed capability
  • excellent resistance to ageing
  • very good rust inhibiting properties

The technical specifications of the grease are listed in table 1.

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