NK 25/20 bearing
25 × 33 mm · dynamic rating 19 kN · static rating 32.5 kN. Dimensions, load ratings, designation meaning, life estimates and equivalent parts.
NK 25/20 specification
| Designation | NK 25/20 |
| Type | Needle roller bearing |
| Series | — |
| Bore diameter d | 25 mm |
| Outside diameter D | 33 mm |
| Basic dynamic load rating C | 19 kN (19,000 N) |
| Basic static load rating C0 | 32.5 kN (32,500 N) |
| Ratio C0/C | 1.71 |
| Speed guide, grease lubrication | 18,000 rpm |
| Life exponent p | 10/3 (roller bearing) |
Values come from the Rotec AI bearing catalogue and are indicative. Confirm against the manufacturer's current catalogue before ordering. Not every dimension (such as width) is listed here.
What the designation NK 25/20 means
| Code | Meaning |
|---|---|
| NK | Needle roller bearing, machined ring with flange, no inner ring — the hardened/ground shaft itself serves as the inner raceway |
| 25 | Bore (Fw) = 25 mm — stated directly, not a bore code |
| 20 | Bearing width = 20 mm — stated directly |
Basic rating life of the NK 25/20
Basic rating life is L10 = (C / P)p million revolutions, where P is the equivalent dynamic load and p = 10/3 (roller bearing). For a NK 25/20 with C = 19 kN, the table shows what that gives at different load levels. It is the ISO 281 basic life only: it does not include lubrication, contamination, misalignment or reliability modifiers.
| C / P | P as share of C | L10 (million rev) | L10 at 1,500 rpm | L10 at 3,000 rpm |
|---|---|---|---|---|
| 3 | 33.3% | 39 | 430 | 220 |
| 5 | 20.0% | 214 | 2,400 | 1,200 |
| 8 | 12.5% | 1,024 | 11,400 | 5,700 |
| 12 | 8.3% | 3,956 | 44,000 | 22,000 |
For example, a C / P of 5 means the equivalent load is 3.8 kN on this bearing. Use the Load Calculator to work out P for your actual radial and axial loads.
Equivalents of the NK 25/20
Brand-by-brand equivalents for this exact designation are not yet in the Rotec AI cross-reference tables. The Cross-Reference tool accepts SKF, FAG, NSK, NTN, Timken, Koyo and NRB designations, and shows what is catalogued.
Where the NK 25/20 is used
Needle roller bearings are chosen for: High radial load in limited radial space. Typical equipment: Transmissions, actuators, mobile equipment, compact machinery. Requires hardened raceways or inner ring; alignment sensitivity.
Other sizes in the same series
The NK 25/20 is size 4 of 24 in the Rotec AI catalogue for the “” series. The next size down, the NK 20/20, has a bore of 20 mm and a dynamic rating of 16.5 kN. The next size up, the NK 30/20 TN, has a bore of 30 mm and a rating of 25.1 kN (+32%).
Common problems on bearings like the NK 25/20
Most field failures trace back to lubrication, contamination, fits and alignment rather than the bearing itself. These guides explain how to recognise and prevent them:
Questions about the NK 25/20
What are the dimensions of a NK 25/20 bearing?
The NK 25/20 has a bore of 25 mm and an outside diameter of 33 mm. It is a needle roller bearing.
What is the load rating of a NK 25/20 bearing?
In the Rotec AI catalogue the NK 25/20 has a basic dynamic load rating C of 19 kN and a basic static load rating C0 of 32.5 kN. Always confirm against the manufacturer's current catalogue.
What is the equivalent of a NK 25/20 bearing?
Brand equivalents for the NK 25/20 are not yet in the Rotec AI tables. Use the Cross-Reference tool to check other designations.