NK73-25 bearing: complete specifications & equivalents
The NK73-25 is a DIN 616 radial bearing sized 73 x 90 x 25 mm (bore x OD x width). Verify dimensions against the official catalog before ordering.
Specification table
| Parameter | Value |
|---|---|
| Brand | SKF |
| Bore diameter d | 73 mm |
| Outer diameter D | 90 mm |
| Width B | 25 mm |
| Material | GCr15 |
| Seal / shield | open |
| Internal clearance | CN |
| Tolerance class | P0 |
| Cage | none |
| Basic dynamic load rating C | 52.8 kN |
| Basic static load rating C0 | 106 kN |
| Fatigue load limit Pu | 13.2 kN |
| Reference speed (thermal) | 5600 rpm |
| Limiting speed (mechanical) | 6300 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 300 g |
| Manufacturer designation | NK 73/25 |
| Standard | DIN 616 |
| Catalog version | SKF PUB BU/P1 17000/1 EN (Oct 2018), ch. 7.3 machined rings with flanges, without an inner ring |
| Last verified | 2026-09-26 |
Source: catalog reference (SKF PUB BU/P1 17000/1 EN (Oct 2018), ch. 7.3 machined rings with flanges, without an inner ring) · extracted 2026-09-26
Parameters extracted from the official SKF Rolling Bearings catalogue (SKF PUB BU/P1 17000/1 EN (Oct 2018), ch. 7.3 machined rings with flanges, without an inner ring); SKF® and SKF Explorer® are trademarks of AB SKF, used here for identification only — mpnbase is not an authorized SKF distributor. Boundary dimensions are ISO 15 interchangeable; current production values may differ, verify at skf.com.
Dimensions in inches & NK-series range
| Bore d | 2.874 in |
|---|---|
| Outer diameter D | 3.543 in |
| Width B | 0.984 in |
| ISO bore code | — |
| Radial section height (D−d)/2 | 8.5 mm |
| Smallest bore in NK-series | 5 mm |
| Largest outer diameter in NK-series | 130 mm |
| Width range across NK-series | 10–40 mm |
| Bore position in NK-series (smallest first) | 38 of 46 |
| Bore above smallest NK-series size | 68 mm |
Cross references & equivalents
No verified interchange data yet. Send an inquiry and our team will confirm equivalents manually.
How the NK73-25 model number is decoded
NK 73/25 is a ribbed machined-ring needle roller bearing (no inner ring) sized 73×90×25 mm: the ground outside diameter seats in the housing, the integral flanges hold the rollers, and the 73 mm shaft journal completes the bearing. The NK 73/25 code states Fw 73 and width 25 mm directly; because the family has no inner ring, the 73 mm journal must be ground, hardened to 58–64 HRC and finished to the raceway tolerance the catalogue specifies. Execution notes: the outer ring flanges are rolled from the ring material (no loose ribs to dislodge), the roller set is caged for low friction, and the TN option swaps in a polymer cage for quieter running. Speed planning separates the two ceilings: 5,600 r/min thermal reference and 6,300 r/min mechanical limiting — needle bearings tolerate high rpm only with adequate lubricant film at the 73 mm seat. Fit the outer ring with a press and a fitting sleeve, not by hammering the flanges — rolled flanges chip; the 90 mm ground OD takes the press fit that prevents outer-ring creep in oscillating duty.
Typical equipment & failure modes
Common applications
- gearbox planetary and idler gears on hardened pins
- piston-pin style pivots in hydraulic pumps
- guide rollers running on hardened tracks
- swing arms and lever pivots with oscillating duty
Known failure patterns
- raceway spalling once the catalogue L10 life is exceeded or after overload events
- polymer cage deformation when the local temperature exceeds the 120 °C sustained limit
- grease starvation at the roller ends when relubrication intervals are stretched in dirty duty
- brinelling of raceways from impact or pressing force transmitted through the rolling elements
- smearing of rollers and journal during idle periods because the radial section holds too little lubricant
Selection pitfalls — read before you substitute
- Above 50 mm bore, thermal growth matters: the 73 mm inner ring or journal grows with temperature faster than the housing, and the small clearance of a needle roller contact leaves little reserve — check running clearance hot, not just at assembly.
- Oscillating pivots fail differently: rocking through a small angle concentrates wear in the same roller positions — inspect those zones, and consider rotating the assembly's clock position at service intervals.
- Contamination, not fatigue, kills most small needle bearings: with raceways this narrow, one hard particle dents a full-width line — seal the housing even when the bearing execution itself is open.
- The 52.8/106 kN ratings and 300 g mass are SKF catalogue values transcribed from ch. 7.3 of PUB BU/P1 17000 (PDF table page 634); combined-type axial ratings appear in the text above because the structured record carries radial values only.
Frequently asked questions
What are the dimensions and ratings of the NK 73/25?
A NK 73/25 measures 73 mm bore/Fw × 90 mm outside diameter × 25 mm width (2.874 × 3.543 × 0.984 in). From SKF catalogue PUB BU/P1 17000: radial dynamic rating C 52.8 kN, static C0 106 kN, fatigue limit Pu 13.2 kN, limiting speed 6,300 r/min, reference speed 5,600 r/min, mass about 300 g.
How is the NK 73/25 designation read?
NK names a machined-ring needle roller bearing without inner ring: the figures give Fw 73 mm and width 25 mm, OD 90 mm comes from the dimension series, and the flanged outer ring retains the caged rollers.
Can the NK 73/25 run on an unhardened shaft?
No. In this execution the 73 mm shaft journal is the inner raceway: it must be ground and hardened to 58–64 HRC (with matching housing bore quality on the outside). If the shaft cannot meet that, order the inner-ring sibling (NKI/NA execution) plus its ground inner ring instead.
How should the NK 73/25 be mounted?
Press on the ring faces only with a fitting sleeve, keep everything square to the 73 mm seat, and never transmit force through the rolling elements. Follow the catalogue's seat tolerances — the narrow needle contact forgives neither tilt nor burrs.
Reviewed & verified by the MPN Base engineering desk against source catalog SKF PUB BU/P1 17000/1 EN (Oct 2018), ch. 7.3 machined rings with flanges, without an inner ring on 2026-09-26. Read our editorial & correction policy.