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Designation system

The designations of most SKF rolling bearings follow a system that may consist of a basic designation with or without one or more prefixes and/or suffixes (→ Basic bearing designation system).
An example and the applicable options for four-row cylindrical roller bearings are given below.
Basic bearing designation system
NNUD 6056 ECMAS/P53whereNNUD 6056 =
EC =
P53 =
In addition to their designation, four-row cylindrical roller bearings are also identified by the design variant/features (→ product table). Some of these features may not be part of the bearing designation, but are always part of the design variant/features (→ Variants/features).
Test Designation 1Prefixes (n.a.)

Test Designation 2Basic designation
NNUDFour-row cylindrical roller bearing based on two NNU design double row bearings
Listed in table 1 or drawing number identification

Catalogue image - Test Designation 3Suffixes - Internal design
A, B, C, D, EDeviating or modified internal design. Combinations of these letters are also used, e.g. DC. The actual modification is specific to the individual bearing and is given on the drawing.
ECOptimized internal design incorporating more and/or larger rollers and with modified roller end / flange contact

Test Designation 4Suffixes - External design (seals, snap ring groove, etc.)
GHelical groove in inner ring bore
KTapered bore, taper 1:12
K30Tapered bore, taper 1:30

Catalogue image - Test Designation 5Suffixes - Cage design
FAMachined steel cage, outer ring centred
MMachined brass cage, roller centred
MA(S)Machined brass cage, outer ring centred. The S indicates a lubrication groove in the guiding surface

Catalogue image - Test Designation 6.1Suffixes - Materials, heat treatment
HA1Case-hardened inner and outer rings
HA2Case-hardened outer ring
HA3Case-hardened inner ring
HA4Case-hardened inner and outer rings and rollers
HA5Case-hardened rollers
HA6Case-hardened outer ring(s) and rollers
HA7Case-hardened inner ring(s) and rollers
HB1Bainite-hardened inner and outer rings
HB2Bainite-hardened outer ring(s)
HB3Bainite-hardened inner ring(s)

Test Designation 6.2Suffixes - Accuracy, clearance, preload, quiet running
CNNormal radial internal clearance; only used together with an additional letter that identifies a reduced or displaced clearance range
  • H = Reduced clearance range corresponding to the upper half of the actual clearance range
  • L = Reduced clearance range corresponding to the lower half of the actual clearance range
  • M = Reduced clearance range corresponding to the middle half of the actual clearance range
  • P = Displaced clearance range comprising the upper half of the actual clearance range plus the lower half of the next larger clearance range
The above letters are also used together with the clearance classes C2, C3, C4 and C5, e.g. C2H
C2Radial internal clearance smaller than Normal
C3Radial internal clearance greater than Normal
C4Radial internal clearance greater than C3
C5Radial internal clearance greater than C4
P5Dimensional and geometrical tolerances to class P5
P6Dimensional and geometrical tolerances to class P6
P53P5 + C3

Catalogue image - Test Designation 6.3Suffixes - Bearing sets, matched bearings (n.a.)

Test Designation 6.4Suffixes - Stabilization
S1Bearing rings heat stabilized for operating temperatures ≤ 200 °C (390 °F)
S2Bearing rings heat stabilized for operating temperatures ≤ 250 °C (480 °F)

Test Designation 6.5Suffixes - Lubrication
W20Lubrication holes in the outer ring(s)
W33Annular groove and lubrication holes in the outer ring(s)

Test Designation 6.6Suffixes - Other variants
VA907Sealed bearing
VJ202Set of two matched double row bearings
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