NKIB5911 bearing: complete specifications & equivalents
The NKIB5911 is a DIN 616 radial bearing sized 55 x 80 x 38 mm (bore x OD x width). Verify dimensions against the official catalog before ordering.
Specification table
| Parameter | Value |
|---|---|
| Brand | SKF |
| Bore diameter d | 55 mm |
| Outer diameter D | 80 mm |
| Width B | 38 mm |
| Material | GCr15 |
| Seal / shield | open |
| Internal clearance | CN |
| Tolerance class | P0 |
| Cage | none |
| Basic dynamic load rating C | 57.2 kN |
| Basic static load rating C0 | 106 kN |
| Fatigue load limit Pu | 13.2 kN |
| Reference speed (thermal) | 6300 rpm |
| Limiting speed (mechanical) | 7000 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 560 g |
| Manufacturer designation | NKIB 5911 |
| Standard | DIN 616 |
| Catalog version | SKF PUB BU/P1 17000/1 EN (Oct 2018), ch. 7.7 needle roller / angular contact ball bearings |
| Last verified | 2026-09-26 |
Source: catalog reference (SKF PUB BU/P1 17000/1 EN (Oct 2018), ch. 7.7 needle roller / angular contact ball bearings) · extracted 2026-09-26
Parameters extracted from the official SKF Rolling Bearings catalogue (SKF PUB BU/P1 17000/1 EN (Oct 2018), ch. 7.7 needle roller / angular contact ball bearings); 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 & NKIB-series range
| Bore d | 2.165 in |
|---|---|
| Outer diameter D | 3.15 in |
| Width B | 1.496 in |
| ISO bore code | 11 |
| Radial section height (D−d)/2 | 12.5 mm |
| Smallest bore in NKIB-series | 12 mm |
| Largest outer diameter in NKIB-series | 100 mm |
| Width range across NKIB-series | 17.5–45 mm |
| Bore position in NKIB-series (smallest first) | 12 of 15 |
| Bore above smallest NKIB-series size | 43 mm |
Cross references & equivalents
No verified interchange data yet. Send an inquiry and our team will confirm equivalents manually.
How the NKIB5911 model number is decoded
NKIB 5911 is a combined needle roller / three-point ball bearing: one unit carrying radial load on the needle roller set and one-direction-leaning axial load on the ball set, 55×80×38 mm, listed by SKF in SKF catalogue PUB BU/P1 17000. The NKIB 5911 code breaks into series letters (needle roller + ball), dimension series 59, and the two-digit bore reference for 55 mm; the 38 mm width covers both the roller cage and the offset ball set (s offset 34 mm). NKIB three-point contact ball raceways accept axial load in both directions, while NKIA angular contact ball raceways lean the axial capacity toward one direction — check the load direction before ordering either. Selection arithmetic for the combined unit: radial C 57.2 kN, radial C0 106 kN, axial dynamic 9.27 kN (Ca) and axial static 16.7 kN (C0a); combine them with the equivalent-load factors from the catalogue before checking L10. Fit the combined unit so the ball raceway offset faces the working axial load, check rotation in both directions, and preload if required with the washer stack the catalogue recommends.
Typical equipment & failure modes
Common applications
- gearbox main shafts carrying radial plus one-direction thrust
- worm gear shafts with axial reaction toward the worm
- spindle heads needing compact radial-plus-axial support
- lead-screw and ball-screw support positions
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
- grease starvation at the roller ends when relubrication intervals are stretched in dirty duty
- false brinelling of standby equipment under external vibration
- thrust-part ball or roller skidding and smearing when the axial load falls below the minimum factor
Selection pitfalls — read before you substitute
- Above 50 mm bore, thermal growth matters: the 55 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.
- Hardness is load capacity: in families without an inner ring the 55 mm journal must hold 58–64 HRC with a ground finish; a surface that looks fine but sits at 45 HRC will rib the raceway within weeks.
- The quoted 57.2/106 kN ratings are SKF catalogue values for this exact execution (NKIB 5911); ratings can be revised without the order number changing, so keep the catalogue version (SKF catalogue PUB BU/P1 17000) with the drawing.
- Do not treat the axial rating 9.27 kN (Ca) as independent of radial load: the combined equivalent load formulas couple them, and a unit sized on radial life alone will spall the ball raceway first under real thrust.
- The thrust part is one-direction: reverse axial events — however brief — lift the rolling elements off the raceway, and the subsequent re-entry impact dents the washer face; mount the NKIB 5911 facing the working thrust.
- The 57.2/106 kN ratings and 560 g mass are SKF catalogue values transcribed from ch. 7.7 of PUB BU/P1 17000 (PDF table page 654); combined-type axial ratings appear in the text above because the structured record carries radial values only.
Frequently asked questions
Can the NKIB 5911 run on an unhardened shaft?
The needle roller part of the NKIB 5911 rides directly on the 55 mm journal, so it must be hardened to 58–64 HRC and ground; the ball set runs on its own integrated raceways. There is no inner-ring variant — harden the shaft or move to a separate bearing arrangement.
How should the NKIB 5911 be mounted?
Press on the ring faces only with a fitting sleeve, keep everything square to the 55 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.
What limits the service life of a NKIB 5911?
Beyond the L10 rating, the practical limits are journal/raceway hardness for the 55 mm seat, lubricant condition at the roller ends, and contamination through open ends — the 12.5 mm radial section leaves no reserve once a raceway is dented or ribboned.
What are the dimensions and ratings of the NKIB 5911?
A NKIB 5911 measures 55 mm bore/Fw × 80 mm outside diameter × 38 mm width (2.165 × 3.15 × 1.496 in). From SKF catalogue PUB BU/P1 17000: radial dynamic rating C 57.2 kN, static C0 106 kN, fatigue limit Pu 13.2 kN, limiting speed 7,000 r/min, reference speed 6,300 r/min, mass about 560 g. Axial ratings of the ball part: dynamic Ca 9.27 kN (Ca), static C0a 16.7 kN (C0a); three-point contact geometry accepts axial load in both directions.
Reviewed & verified by the MPN Base engineering desk against source catalog SKF PUB BU/P1 17000/1 EN (Oct 2018), ch. 7.7 needle roller / angular contact ball bearings on 2026-09-26. Read our editorial & correction policy.