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.
Example
| RNA 4900.2RS | where | R = |  |
| NA 4900 = |  |
| .2RS = |  |
| Prefixes
|
R
| Bearing without an inner ring (applicable to NA 48, NA 49, NA 69 and NAO series)
|
| Basic designation (table 1) |
NA 48, NA 49, NA 69
| Needle roller bearing with machined rings, with flanges, with an inner ring |
| NAO | Needle roller bearing with machined rings, without flanges, with an inner ring |
NK, NKS
| Needle roller bearing with machined rings, with flanges, without an inner ring |
NKI, NKIS
| Needle roller bearing with machined rings, with flanges, with an inner ring |
| Suffixes - Internal design (n.a.) |
| Suffixes - External design (seals, snap ring groove etc.) |
| RS | Contact seal, NBR, on one side |
| .2RS | Contact 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 |
| Suffixes - Cage design |
| TN | Glass fibre reinforced PA66 cage |
| Suffixes - Materials, heat treatment (n.a.) |
 | 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 two middle quarters 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R = Normal clearance range in accordance with the withdrawn DIN 620-4:1982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 |
| C2 | Radial internal clearance smaller than Normal |
| C3 | Radial internal clearance greater than Normal |
| C4 | Radial 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
|
| P5 | Dimensional and geometrical tolerances to class P5
|
| P6 | Dimensional and geometrical tolerances to class P6 |
| P62 | P6 + C2 |
| P63 | P6 + C3 |
| P6CNR | P6 + CNR |
| 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
|
| 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.) |
| Suffixes - Other variants (n.a.) |
