NKIB5904 bearing: complete specifications & equivalents
The NKIB5904 is a DIN 616 radial bearing sized 20 x 37 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 | 20 mm |
| Outer diameter D | 37 mm |
| Width B | 25 mm |
| Material | GCr15 |
| Seal / shield | open |
| Internal clearance | CN |
| Tolerance class | P0 |
| Cage | none |
| Basic dynamic load rating C | 21.6 kN |
| Basic static load rating C0 | 28 kN |
| Fatigue load limit Pu | 3.35 kN |
| Reference speed (thermal) | 15000 rpm |
| Limiting speed (mechanical) | 17000 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 110 g |
| Manufacturer designation | NKIB 5904 |
| 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 | 0.787 in |
|---|---|
| Outer diameter D | 1.457 in |
| Width B | 0.984 in |
| ISO bore code | 04 |
| Radial section height (D−d)/2 | 8.5 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) | 4 of 15 |
| Bore above smallest NKIB-series size | 8 mm |
Cross references & equivalents
No verified interchange data yet. Send an inquiry and our team will confirm equivalents manually.
How the NKIB5904 model number is decoded
NKIB 5904 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, 20×37×25 mm, listed by SKF in SKF catalogue PUB BU/P1 17000. The designation NKIB 5904 identifies the two rolling elements in one unit; the 20 mm bore and 37 mm OD come from the 59-series plan, and the 25 mm width stacks roller set plus ball set. The combined unit is greased for life at assembly in many applications; relubrication, where provided, must reach both the roller cage and the ball set through the same axial bore features. Selection arithmetic for the combined unit: radial C 21.6 kN, radial C0 28 kN, axial dynamic 3.79 kN (Ca) and axial static 4.21 kN (C0a); combine them with the equivalent-load factors from the catalogue before checking L10. Life-lubricated as supplied in most sizes; where a relubrication path exists, meter grease gently — pressure through the 25 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
- 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
- electrical erosion on VFD-driven shafts without brush or insulated mounting
- thrust-part ball or roller skidding and smearing when the axial load falls below the minimum factor
Selection pitfalls — read before you substitute
- On a 20 mm seat the housing bore quality dominates life: a bore 0.02 mm out of round pinches the 37 mm ring or cup into a lobed shape, and the rollers then trace the housing's geometry error, not the design load.
- 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.
- Minimum axial load is a real requirement: below the catalogue minimum the thrust elements skid, polish their raceways and lose them — springs or preload washers belong in the arrangement drawing, not the troubleshooting notes.
- 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.
- The 21.6/28 kN ratings and 110 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 5904 run on an unhardened shaft?
The needle roller part of the NKIB 5904 rides directly on the 20 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 5904 be mounted?
Press on the ring faces only with a fitting sleeve, keep everything square to the 20 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 5904?
Beyond the L10 rating, the practical limits are journal/raceway hardness for the 20 mm seat, lubricant condition at the roller ends, and contamination through open ends — the 8.5 mm radial section leaves no reserve once a raceway is dented or ribboned.
What are the dimensions and ratings of the NKIB 5904?
A NKIB 5904 measures 20 mm bore/Fw × 37 mm outside diameter × 25 mm width (0.787 × 1.457 × 0.984 in). From SKF catalogue PUB BU/P1 17000: radial dynamic rating C 21.6 kN, static C0 28 kN, fatigue limit Pu 3.35 kN, limiting speed 17,000 r/min, reference speed 15,000 r/min, mass about 110 g. Axial ratings of the ball part: dynamic Ca 3.79 kN (Ca), static C0a 4.21 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.