SKF - Spherical Plain Bearings and Rod Ends

Lubrication
Maintenance-free spherical
plain bearings
Steel/PTFE sintered bronze and steel/
PTFE fabric sliding contact surface
combinations
During operation, PTFE is transferred from the
dry sliding contact surface of the outer ring to
the hard chromium plated steel surface of the
inner ring. Any external lubricant on the sliding
contact surfaces would disturb this self-lubrication
and shorten bearing service life.
As a result, these bearings must not be lubricated
and do not have any relubrication facility.
Steel/PTFE FRP sliding contact surface
combination
Bearings with this sliding contact surface combination
are also self-lubricating and can be
operated grease-free.
However, initial lubrication followed by occasional
relubrication of steel/PTFE FRP bearings
can extend the service life of the bearing by a
factor of two or more. The inner rings of radial
bearings or shaft washers of angular contact
and thrust bearings are coated with a lithium
base grease before leaving the factory.
If operating conditions are such that protection
against corrosion and enhanced sealing are
required, the free space surrounding the bearing
(† fig. 4) can be filled with the same grease
that was used to lubricate the bearing. The
appropriate time to replenish or renew the
grease in the bearing arrangement is determined
by the operating conditions and the ageing
of the grease.
Rust inhibiting, water-repellent lithium base
greases with a consistency of 2 on the NGLI
scale should be used. SKF recommends SKF
LGEP 2 grease († table 1 on page 87). Greases
containing molybdenum disulphide or other
solid lubricants should never be used.
CAUTION: Depending on their design, SKF
spherical plain bearings are either completely or
partially coated with an oily preservative or filled
with grease. Avoid skin contact as these substances
may cause skin irritation or an allergic
reaction.
Fig. 4
Relubricating the bearing from the side
88