NKIA5904 bearing: complete specifications & equivalents
The NKIA5904 is a DIN 616 radial bearing sized 20 x 37 x 23 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 | 23 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 | 100 g |
| Manufacturer designation | NKIA 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 & NKIA-series range
| Bore d | 0.787 in |
|---|---|
| Outer diameter D | 1.457 in |
| Width B | 0.906 in |
| ISO bore code | 04 |
| Radial section height (D−d)/2 | 8.5 mm |
| Smallest bore in NKIA-series | 12 mm |
| Largest outer diameter in NKIA-series | 100 mm |
| Width range across NKIA-series | 16–40 mm |
| Bore position in NKIA-series (smallest first) | 4 of 15 |
| Bore above smallest NKIA-series size | 8 mm |
Cross references & equivalents
No verified interchange data yet. Send an inquiry and our team will confirm equivalents manually.
How the NKIA5904 model number is decoded
NKIA 5904 solves compact radial-plus-thrust duty: a needle roller cage and an angular contact ball bearing built into one 23 mm wide unit with a 20 mm bore and 37 mm outside diameter. Reading the designation: the letters combine the needle roller family with the ball execution — NKIA marks angular contact — and 595904 the heavy 59 dimension series around the 20 mm bore. 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. 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
- spindle heads needing compact radial-plus-axial support
- lead-screw and ball-screw support positions
- pump rotors with hydraulic axial pull
- bevel gear shafts with moderate axial force
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
- abrasive paste formation from dust ingressing past open ends without effective housing seals
- brinelling of raceways from impact or pressing force transmitted through the rolling elements
- 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.
- 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: NKIA 5904 shares its 20×37×23 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 3.79 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 21.6/28 kN ratings and 100 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 does NKIA 5904 mean in SKF part numbering?
NKIA combines a needle roller cage with an angular contact ball bearing in one unit; 595904 gives the series and 20 mm bore. The offset (a catalogue-listed offset) positions the ball raceway inside the 23 mm overall width.
Does the NKIA 5904 need a hardened and ground shaft?
The needle roller part of the NKIA 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.
What mounting mistakes ruin a NKIA 5904?
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.
Is the NKIA 5904 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.
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.