NKIB5903 bearing: complete specifications & equivalents
The NKIB5903 is a DIN 616 radial bearing sized 17 x 30 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 | 17 mm |
| Outer diameter D | 30 mm |
| Width B | 20 mm |
| Material | GCr15 |
| Seal / shield | open |
| Internal clearance | CN |
| Tolerance class | P0 |
| Cage | none |
| Basic dynamic load rating C | 11.4 kN |
| Basic static load rating C0 | 16.3 kN |
| Fatigue load limit Pu | 1.96 kN |
| Reference speed (thermal) | 18000 rpm |
| Limiting speed (mechanical) | 20000 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 58 g |
| Manufacturer designation | NKIB 5903 |
| 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 | 0.669 in |
|---|---|
| Outer diameter D | 1.181 in |
| Width B | 0.787 in |
| ISO bore code | 03 |
| Radial section height (D−d)/2 | 6.5 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) | 3 of 15 |
| Bore above smallest NKIB-series size | 5 mm |
Cross references & equivalents
No verified interchange data yet. Send an inquiry and our team will confirm equivalents manually.
How the NKIB5903 model number is decoded
NKIB 5903 is the combined needle roller / three-point contact ball bearings entry for a 17 mm shaft: needle rollers run the radial load while the three-point contact ball set takes axial force in both directions through the three-point contact geometry, in a single machined envelope of 17×30×20 mm. In SKF nomenclature NKIB denotes the combined construction and 595903 the series/bore; the ball raceway sits offset on the inner ring, which is why the 20 mm overall width is greater than a plain needle bearing of the same bore. Execution notes: the ball set runs on a raceway offset by s 18 mm from the roller set centreline — this offset is why the overall width exceeds a plain needle bearing and why the units cannot be dismantled without losing preload. Speed ceilings differ by part: 18,000 r/min thermal reference and 20,000 r/min limiting — the thrust element governs, since its washer faces see sliding components of contact. Life-lubricated as supplied in most sizes; where a relubrication path exists, meter grease gently — pressure through the 20 mm wide unit can lift the seals of adjacent components.
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
- needle edge loading and raceway denting when the shaft deflects beyond the compensation range
- 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
- hard-particle indentation in unfiltered lubricant
- thrust washer raceway wear from reverse axial shocks the one-direction thrust part cannot carry
Selection pitfalls — read before you substitute
- On a 17 mm seat the housing bore quality dominates life: a bore 0.02 mm out of round pinches the 30 mm ring or cup into a lobed shape, and the rollers then trace the housing's geometry error, not the design load.
- 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.
- Do not interchange envelope-identical needle families blindly: NKIB 5903 shares its 17×30×20 mm outline with inner-ring and sealed siblings whose ratings differ — the family letters are part of the specification, not decoration.
- Height stack-up is easy to mis-check: the ball-raceway part adds height beyond a plain needle bearing, and clamping the stack solid over it preloads the thrust set beyond its rating.
- Do not treat the axial rating 2.24 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 11.4/16.3 kN ratings and 58 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
What mounting mistakes ruin a NKIB 5903?
Press on the ring faces only with a fitting sleeve, keep everything square to the 17 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.
Is the NKIB 5903 sealed?
No — this execution is open and depends on the housing sealing arrangement; grease it at assembly and keep the relubrication interval short in dirty duty.
Which dimensions does the NKIB 5903 have?
A NKIB 5903 measures 17 mm bore/Fw × 30 mm outside diameter × 20 mm width (0.669 × 1.181 × 0.787 in). From SKF catalogue PUB BU/P1 17000: radial dynamic rating C 11.4 kN, static C0 16.3 kN, fatigue limit Pu 1.96 kN, limiting speed 20,000 r/min, reference speed 18,000 r/min, mass about 58 g. Axial ratings of the ball part: dynamic Ca 2.24 kN (Ca), static C0a 2.74 kN (C0a); three-point contact geometry accepts axial load in both directions.
What does NKIB 5903 mean in SKF part numbering?
NKIB combines a needle roller cage with an three-point contact ball bearing in one unit; 595903 gives the series and 17 mm bore. The offset (s 18 mm) positions the ball raceway inside the 20 mm overall width.
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.