NK50-25-TN bearing: complete specifications & equivalents
The NK50-25-TN is a DIN 616 radial bearing sized 50 x 62 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 | 50 mm |
| Outer diameter D | 62 mm |
| Width B | 25 mm |
| Material | GCr15 |
| Seal / shield | open |
| Internal clearance | CN |
| Tolerance class | P0 |
| Cage | polymer (PA66 glass-fibre reinforced) |
| Basic dynamic load rating C | 42.9 kN |
| Basic static load rating C0 | 91.5 kN |
| Fatigue load limit Pu | 11.2 kN |
| Reference speed (thermal) | 8000 rpm |
| Limiting speed (mechanical) | 9000 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 150 g |
| Manufacturer designation | NK 50/25 TN |
| 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 | 1.969 in |
|---|---|
| Outer diameter D | 2.441 in |
| Width B | 0.984 in |
| ISO bore code | — |
| Radial section height (D−d)/2 | 6 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) | 32 of 46 |
| Bore above smallest NK-series size | 45 mm |
Cross references & equivalents
No verified interchange data yet. Send an inquiry and our team will confirm equivalents manually.
How the NK50-25-TN model number is decoded
SKF's machined-ring needle roller bearings without inner ring include NK 50/25 TN: 50 mm Fw, 62 mm outside diameter, 25 mm width — a machined and ground outer ring whose rolled flanges retain the needle rollers, running on the shaft as the inner raceway. The letters identify a flanged machined outer ring without inner ring; the figures give 50 mm Fw and 25 mm B — dimensionally identical envelopes exist with an inner ring under the NA/NKI names, which changes the shaft seat entirely. The wide NKS/NKIS siblings share the Fw and OD but add width for higher ratings — check both when the radial space allows a wider seat. Minimum load matters: below roughly 0.02·C the rollers skid and smear; preloading the pivot or specifying a heavier execution avoids the glazing that pure oscillation produces on these raceways. Grease through the housing groove before fitting the shaft; the integral flanges hold the grease film at the roller ends, which is where these bearings first starve.
Typical equipment & failure modes
Common applications
- swing arms and lever pivots with oscillating duty
- cam followers built up from separate components
- crank pins and eccentrics where the hardened journal is the raceway
- gearbox planetary and idler gears on hardened pins
Known failure patterns
- raceway spalling once the catalogue L10 life is exceeded or after overload events
- cage pocket wear and roller skew after sustained operation with too little radial preload
- abrasive paste formation from dust ingressing past open ends without effective housing seals
- electrical erosion on VFD-driven shafts without brush or insulated mounting
- smearing of rollers and journal during idle periods because the radial section holds too little lubricant
Selection pitfalls — read before you substitute
- At 50 mm bore, verify shaft deflection against the needle length: these rollers tolerate little edge loading, and a simply supported span between 50 mm seats can bend past the compensation range long before the load rating is exhausted.
- 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 42.9/91.5 kN ratings and 150 g mass are SKF catalogue values transcribed from ch. 7.3 of PUB BU/P1 17000 (PDF table page 632); 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 50/25 TN?
A NK 50/25 TN measures 50 mm bore/Fw × 62 mm outside diameter × 25 mm width (1.969 × 2.441 × 0.984 in). From SKF catalogue PUB BU/P1 17000: radial dynamic rating C 42.9 kN, static C0 91.5 kN, fatigue limit Pu 11.2 kN, limiting speed 9,000 r/min, reference speed 8,000 r/min, mass about 150 g.
How is the NK 50/25 TN designation read?
NK names a machined-ring needle roller bearing without inner ring: the figures give Fw 50 mm and width 25 mm, OD 62 mm comes from the dimension series, and the flanged outer ring retains the caged rollers.
Can the NK 50/25 TN run on an unhardened shaft?
No. In this execution the 50 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 50/25 TN be mounted?
Press on the ring faces only with a fitting sleeve, keep everything square to the 50 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.