NKS28 bearing: complete specifications & equivalents
The NKS28 is a DIN 616 radial bearing sized 28 x 42 x 20 mm (bore x OD x width). Verify dimensions against the official catalog before ordering.
Specification table
| Parameter | Value |
|---|---|
| Brand | SKF |
| Bore diameter d | 28 mm |
| Outer diameter D | 42 mm |
| Width B | 20 mm |
| Material | GCr15 |
| Seal / shield | open |
| Internal clearance | CN |
| Tolerance class | P0 |
| Cage | none |
| Basic dynamic load rating C | 28.6 kN |
| Basic static load rating C0 | 39 kN |
| Fatigue load limit Pu | 4.75 kN |
| Reference speed (thermal) | 13000 rpm |
| Limiting speed (mechanical) | 15000 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 84 g |
| Manufacturer designation | NKS 28 |
| 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 & NKS-series range
| Bore d | 1.102 in |
|---|---|
| Outer diameter D | 1.654 in |
| Width B | 0.787 in |
| ISO bore code | — |
| Radial section height (D−d)/2 | 7 mm |
| Smallest bore in NKS-series | 20 mm |
| Largest outer diameter in NKS-series | 95 mm |
| Width range across NKS-series | 20–28 mm |
| Bore position in NKS-series (smallest first) | 4 of 17 |
| Bore above smallest NKS-series size | 8 mm |
Cross references & equivalents
| Equivalent model | Brand | Match level | Note |
|---|---|---|---|
| NKI28-20-TN | SKF | partial Main dimensions match; tolerances, seals or internal clearance differ. | Same 28×42×20 mm envelope, but catalogue C/C0 differ between the executions (28.6/39 vs 26.4/48 kN) — boundary dimensions match, not a load-rating equivalent. |
Interchange levels: full standard interchange · partial verify parameters · verify manual confirmation required. Links resolve to the equivalent model's specification page where available.
How the NKS28 model number is decoded
NKS 28 is a ribbed machined-ring needle roller bearing (no inner ring) sized 28×42×20 mm: the ground outside diameter seats in the housing, the integral flanges hold the rollers, and the 28 mm shaft journal completes the bearing. The NKS 28 code states Fw 28 and width 20 mm directly; because the family has no inner ring, the 28 mm journal must be ground, hardened to 58–64 HRC and finished to the raceway tolerance the catalogue specifies. The machined ring is through-hardened and ground on OD, bore-side raceway and faces; the flanged lip design means the housing shoulder can be omitted — the ring clamps axially between housing wall and cover washer. 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. Fit the outer ring with a press and a fitting sleeve, not by hammering the flanges — rolled flanges chip; the 42 mm ground OD takes the press fit that prevents outer-ring creep in oscillating duty.
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
- false brinelling of standby equipment under external vibration
- smearing of rollers and journal during idle periods because the radial section holds too little lubricant
Selection pitfalls — read before you substitute
- At 28 mm bore, verify shaft deflection against the needle length: these rollers tolerate little edge loading, and a simply supported span between 28 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 28.6/39 kN ratings and 84 g mass are SKF catalogue values transcribed from ch. 7.3 of PUB BU/P1 17000 (PDF table page 628); combined-type axial ratings appear in the text above because the structured record carries radial values only.
Frequently asked questions
What limits the service life of a NKS 28?
Beyond the L10 rating, the practical limits are journal/raceway hardness for the 28 mm seat, lubricant condition at the roller ends, and contamination through open ends — the 7.0 mm radial section leaves no reserve once a raceway is dented or ribboned.
What are the dimensions and ratings of the NKS 28?
A NKS 28 measures 28 mm bore/Fw × 42 mm outside diameter × 20 mm width (1.102 × 1.654 × 0.787 in). From SKF catalogue PUB BU/P1 17000: radial dynamic rating C 28.6 kN, static C0 39 kN, fatigue limit Pu 4.75 kN, limiting speed 15,000 r/min, reference speed 13,000 r/min, mass about 84 g.
How is the NKS 28 designation read?
NKS names a machined-ring needle roller bearing without inner ring: the figures give Fw 28 mm and width 20 mm, OD 42 mm comes from the dimension series, and the flanged outer ring retains the caged rollers.
Can the NKS 28 run on an unhardened shaft?
No. In this execution the 28 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.
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.