NKIS50 bearing: complete specifications & equivalents
The NKIS50 is a DIN 616 radial bearing sized 50 x 80 x 28 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 | 80 mm |
| Width B | 28 mm |
| Material | GCr15 |
| Seal / shield | open |
| Internal clearance | CN |
| Tolerance class | P0 |
| Cage | none |
| Basic dynamic load rating C | 62.7 kN |
| Basic static load rating C0 | 104 kN |
| Fatigue load limit Pu | 13.2 kN |
| Reference speed (thermal) | 6300 rpm |
| Limiting speed (mechanical) | 7500 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 520 g |
| Manufacturer designation | NKIS 50 |
| Standard | DIN 616 |
| Catalog version | SKF PUB BU/P1 17000/1 EN (Oct 2018), ch. 7.4 machined rings with flanges, with an inner ring |
| Last verified | 2026-09-26 |
Source: catalog reference (SKF PUB BU/P1 17000/1 EN (Oct 2018), ch. 7.4 machined rings with flanges, with 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. 7.4 machined rings with flanges, with 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 & NKIS-series range
| Bore d | 1.969 in |
|---|---|
| Outer diameter D | 3.15 in |
| Width B | 1.102 in |
| ISO bore code | — |
| Radial section height (D−d)/2 | 15 mm |
| Smallest bore in NKIS-series | 15 mm |
| Largest outer diameter in NKIS-series | 95 mm |
| Width range across NKIS-series | 20–28 mm |
| Bore position in NKIS-series (smallest first) | 9 of 12 |
| Bore above smallest NKIS-series size | 35 mm |
Cross references & equivalents
No verified interchange data yet. Send an inquiry and our team will confirm equivalents manually.
How the NKIS50 model number is decoded
SKF lists NKIS 50 in the wide-section machined-ring needle roller bearings with inner ring with boundary dimensions 50×80×28 mm: an inner ring turns on the shaft while the flanged outer ring carries the needle roller complement in the housing. The NKIS 50 code gives bore 50 mm and width 28 mm explicitly; unlike the RNA/NK families the shaft only needs a standard k5/j5 seat because the hardened inner ring is the raceway. TN polymer cage executions run quieter and tolerate grease-lubricated pivot duty; steel cage executions remain the choice for higher temperature or oil-bath lubrication. Speed planning separates the two ceilings: 6,300 r/min thermal reference and 7,500 r/min mechanical limiting — needle bearings tolerate high rpm only with adequate lubricant film at the 50 mm seat. For NA 49 2RS executions the wider outer ring changes the housing depth: verify the 28 mm width and s offset dimensions against the open execution before reusing an existing bore.
Typical equipment & failure modes
Common applications
- wheel and lever pivots needing a replaceable inner ring
- conveyor roller ends and return rollers
- agricultural implement pivots and cutter heads
- electric motor armature shafts with ground seats
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
- abrasive paste formation from dust ingressing past open ends without effective housing seals
- hard-particle indentation in unfiltered lubricant
- inner-ring bore fretting on a loose shaft seat, migrating hard particles into the rolling contact
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 62.7/104 kN ratings and 520 g mass are SKF catalogue values transcribed from ch. 7.4 of PUB BU/P1 17000 (PDF table page 642); combined-type axial ratings appear in the text above because the structured record carries radial values only.
Frequently asked questions
How is the NKIS 50 designation read?
The letters mark a machined-ring needle roller bearing with inner ring: 50 mm bore, 28 mm width, 80 mm OD per the series plan. The hardened inner ring is the raceway, so an ordinary k5 shaft seat suffices.
Can the NKIS 50 run on an unhardened shaft?
Yes — that is the point of this family. The NKIS 50 carries its own hardened, ground inner ring on a 50 mm seat, so the shaft needs only a normal k5/j6 finish. The inner ring is separable and replaceable.
How should the NKIS 50 be mounted?
Mount the inner ring on the 50 mm seat first (induction heat, max 120 °C, or press), then fit the flanged outer ring into the H7 housing bore. Verify free rotation and, for 2RS executions, check the wider outer ring against the housing depth.
What limits the service life of a NKIS 50?
Beyond the L10 rating, the practical limits are journal/raceway hardness for the 50 mm seat, lubricant condition at the roller ends, and contamination through open ends — the 15.0 mm radial section leaves no reserve once a raceway is dented or ribboned.
Reviewed & verified by the MPN Base engineering desk against source catalog SKF PUB BU/P1 17000/1 EN (Oct 2018), ch. 7.4 machined rings with flanges, with an inner ring on 2026-09-26. Read our editorial & correction policy.