NK28-30 bearing: complete specifications & equivalents
The NK28-30 is a DIN 616 radial bearing sized 28 x 37 x 30 mm (bore x OD x width). Verify dimensions against the official catalog before ordering.
Specification table
| Parameter | Value |
|---|---|
| Brand | SKF |
| Bore diameter d | 28 mm |
| Outer diameter D | 37 mm |
| Width B | 30 mm |
| Material | GCr15 |
| Seal / shield | open |
| Internal clearance | CN |
| Tolerance class | P0 |
| Cage | none |
| Basic dynamic load rating C | 31.9 kN |
| Basic static load rating C0 | 60 kN |
| Fatigue load limit Pu | 7.5 kN |
| Reference speed (thermal) | 14000 rpm |
| Limiting speed (mechanical) | 16000 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 82 g |
| Manufacturer designation | NK 28/30 |
| Standard | DIN 616 |
| Catalog version | SKF PUB BU/P1 17000/1 EN (Oct 2018), ch. 7.3 machined rings with flanges, without an inner ring |
| Last verified | 2026-09-26 |
Source: catalog reference (SKF PUB BU/P1 17000/1 EN (Oct 2018), ch. 7.3 machined rings with flanges, without 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. 7.3 machined rings with flanges, without 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 & NK-series range
| Bore d | 1.102 in |
|---|---|
| Outer diameter D | 1.457 in |
| Width B | 1.181 in |
| ISO bore code | — |
| Radial section height (D−d)/2 | 4.5 mm |
| Smallest bore in NK-series | 5 mm |
| Largest outer diameter in NK-series | 130 mm |
| Width range across NK-series | 10–40 mm |
| Bore position in NK-series (smallest first) | 20 of 46 |
| Bore above smallest NK-series size | 23 mm |
Cross references & equivalents
No verified interchange data yet. Send an inquiry and our team will confirm equivalents manually.
How the NK28-30 model number is decoded
NK 28/30 belongs to the machined-ring needle roller family: an outer ring turned and ground to 37 mm with two retaining flanges, a roller-and-cage set inside, and envelope 28×37×30 mm on a hardened 28 mm shaft. In SKF nomenclature NK families drop the inner ring: the numbers after the letters give the 28 mm under-roller diameter and the 30 mm width, with the 37 mm outside diameter set by the machined-ring needle roller bearings without inner ring plan. The machined ring is through-hardened and ground on OD, bore-side raceway and faces; the flanged lip design means the housing shoulder can be omitted — the ring clamps axially between housing wall and cover washer. Catalogue mass 82 g at 28×37×30 mm makes this one of the highest capacity-per-gram choices in the machined-ring needle roller bearings without inner ring; the limit is usually the shaft's ability to serve as a raceway, not the rolling contact itself. Fit the outer ring with a press and a fitting sleeve, not by hammering the flanges — rolled flanges chip; the 37 mm ground OD takes the press fit that prevents outer-ring creep in oscillating duty.
Typical equipment & failure modes
Common applications
- cam followers built up from separate components
- crank pins and eccentrics where the hardened journal is the raceway
- gearbox planetary and idler gears on hardened pins
- piston-pin style pivots in hydraulic pumps
Known failure patterns
- needle edge loading and raceway denting when the shaft deflects beyond the compensation range
- cage pocket wear and roller skew after sustained operation with too little radial preload
- abrasive paste formation from dust ingressing past open ends without effective housing seals
- false brinelling of standby equipment under external vibration
- smearing of rollers and journal during idle periods because the radial section holds too little lubricant
Selection pitfalls — read before you substitute
- At 28 mm bore, verify shaft deflection against the needle length: these rollers tolerate little edge loading, and a simply supported span between 28 mm seats can bend past the compensation range long before the load rating is exhausted.
- Reference and limiting speeds are different limits: the 14,000 r/min reference is the thermal criterion under load, The limiting value is mechanical; the reference value is thermal under load, and grease choice moves it substantially.
- Hardness is load capacity: in families without an inner ring the 28 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 31.9/60 kN ratings and 82 g mass are SKF catalogue values transcribed from ch. 7.3 of PUB BU/P1 17000 (PDF table page 628); combined-type axial ratings appear in the text above because the structured record carries radial values only.
Frequently asked questions
Does the NK 28/30 need a hardened and ground shaft?
No. In this execution the 28 mm shaft journal is the inner raceway: it must be ground and hardened to 58–64 HRC (with matching housing bore quality on the outside). If the shaft cannot meet that, order the inner-ring sibling (NKI/NA execution) plus its ground inner ring instead.
What mounting mistakes ruin a NK 28/30?
Press on the ring faces only with a fitting sleeve, keep everything square to the 28 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 NK 28/30 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 NK 28/30 have?
A NK 28/30 measures 28 mm bore/Fw × 37 mm outside diameter × 30 mm width (1.102 × 1.457 × 1.181 in). From SKF catalogue PUB BU/P1 17000: radial dynamic rating C 31.9 kN, static C0 60 kN, fatigue limit Pu 7.5 kN, limiting speed 16,000 r/min, reference speed 14,000 r/min, mass about 82 g.
Reviewed & verified by the MPN Base engineering desk against source catalog SKF PUB BU/P1 17000/1 EN (Oct 2018), ch. 7.3 machined rings with flanges, without an inner ring on 2026-09-26. Read our editorial & correction policy.