SKF four-row cylindrical roller bearings nomenclature

SKF four-row cylindrical roller bearings follow a system that may consist of a basic designation with or without one or more prefixes and/or suffixes

In addition to their designation, four-row cylindrical roller bearings are also identified by the design variant/features. Some of these features may not be part of the bearing designation, but are always part of the design variant/features

1 Prefixes (n.a.)
2 Basic designation
NNUD Four-row cylindrical roller bearing based on two NNU design double row bearings
Listed in SKF bearing designation (nomenclature)
3 Suffixes - Internal design
ABCDE Deviating 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.
EC Optimized internal design incorporating more and/or larger rollers and with modified roller end / flange contact
4 Suffixes - External design (seals, snap ring groove etc.)
G Helical groove in inner ring bore
K Tapered bore, taper 1:12
K30 Tapered bore, taper 1:30
5 Suffixes - Cage design
FA Machined steel cage, outer ring centred
M Machined brass cage, roller centred
MA(S) Machined brass cage, outer ring centred. The S indicates a lubrication groove in the guiding surface
6.1 Suffixes - Materials, heat treatment
HA1 Case-hardened inner and outer rings
HA2 Case-hardened outer ring
HA3 Case-hardened inner ring
HA4 Case-hardened inner and outer rings and rollers
HA5 Case-hardened rollers
HA6 Case-hardened outer ring(s) and rollers
HA7 Case-hardened inner ring(s) and rollers
HB1 Bainite-hardened inner and outer rings
HB2 Bainite-hardened outer ring(s)
HB3 Bainite-hardened inner ring(s)
6.2 Suffixes - Accuracy, clearance, preload, quiet running
CN Normal 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
C2 Radial internal clearance smaller than Normal
C3 Radial internal clearance greater than Normal
C4 Radial internal clearance greater than C3
C5 Radial internal clearance greater than C4
P5 Dimensional and geometrical tolerances to class P5
P6 Dimensional and geometrical tolerances to class P6
P53 P5 + C3
6.3 Suffixes - Bearing sets, matched bearings (n.a.)
6.4 Suffixes - Stabilization
S1 Bearing rings heat stabilized for operating temperatures ≤ 200 °C (390 °F)
S2 Bearing rings heat stabilized for operating temperatures ≤ 250 °C (480 °F)
6.5 Suffixes - Lubrication
W20 Lubrication holes in the outer ring(s)
W33 Annular groove and lubrication holes in the outer ring(s)
6.6 Suffixes - Other variants
VA907 Sealed bearing
VJ202 Set of two matched double row bearings

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