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 needle roller bearings with machined rings are given below.
Basic bearing designation system

Example

RNA 4900.2RSwhereR =
NA 4900 =
.2RS =
Test Designation 1
  Prefixes
R
Bearing without an inner ring

Test Designation 2
Basic designation
NA 48Needle roller bearing with machined rings, with flanges, with an inner ring
NA 49Needle roller bearing with machined rings, with flanges, with an inner ring
NA 69Needle roller bearing with machined rings, with flanges, with an inner ring
NAONeedle roller bearing with machined rings, without flanges, with an inner ring
NKNeedle roller bearing with machined rings, with flanges, without an inner ring
NKINeedle roller bearing with machined rings, with flanges, with an inner ring
NKISNeedle roller bearing with machined rings, with flanges, with an inner ring
NKSNeedle roller bearing with machined rings, with flanges, without an inner ring

Catalogue image - Test Designation 3
Suffixes - Internal design (n.a.)

Test Designation 4
Suffixes - External design (seals, snap ring groove etc.)
RSContact seal, NBR, on one side
.2RSContact seal, NBR, on both sides
ASR..
Outer ring with annular groove and lubrication hole(s), the number following indicates the number of holes
IS..Inner ring with lubrication hole(s), the number following indicates the number of holes
ISR..Inner ring with annular groove and lubrication hole(s), the number following indicates the number of holes

Catalogue image - Test Designation 5
Suffixes - Cage design
TNGlass fibre reinforced PA66 cage

Catalogue image - Test Designation 6.1
Suffixes - Materials, heat treatment (n.a.)

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 two middle quaters 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
  • R = Normal clearance range in accordance with the withdrawn DIN 620-4:1982
The above letters H, L, M and P are also used together with the clearance classes C2, C3, C4
C2Radial internal clearance smaller than Normal
C3Radial internal clearance greater than Normal
C4Radial internal clearance greater than C3
H..
Bearing without an inner ring and reduced inside diameter (under rollers) tolerance, the numbers following indicate the tolerance limits in µm, e.g. H+27+20
P5Dimensional and geometrical tolerances to class P5
P6Dimensional and geometrical tolerances to class P6
P62P6 + C2
P63P6 + C3
P6CNRP6 + CNR

Catalogue image - Test Designation 6.3
Suffixes - Bearing sets, matched bearings
..S
Matched bearings for an equal load distribution. The number preceding indicates the number of bearings, e.g. NK 50/25 TN/2S

Test Designation 6.4
Suffixes - Stabilization (n.a.)
S0
Bearing heat stabilized for operating temperatures ≤ 150 °C (300 °F)
S1
Bearing heat stabilized for operating temperatures ≤ 200 °C (390 °F)
S2
Bearing heat stabilized for operating temperatures ≤ 250 °C (480 °F)
S3
Bearing heat stabilized for operating temperatures ≤ 300 °C (570 °F)


Suffixes - Lubrication (n.a.)

Test Designation 6.6
Suffixes - Other variants (n.a.)
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