NKS50 bearing: complete specifications & equivalents
The NKS50 is a DIN 616 radial bearing sized 50 x 65 x 22 mm (bore x OD x width). Verify dimensions against the official catalog before ordering.
Specification table
| Parameter | Value |
|---|---|
| Brand | SKF |
| Bore diameter d | 50 mm |
| Outer diameter D | 65 mm |
| Width B | 22 mm |
| Material | GCr15 |
| Seal / shield | open |
| Internal clearance | CN |
| Tolerance class | P0 |
| Cage | none |
| Basic dynamic load rating C | 42.9 kN |
| Basic static load rating C0 | 72 kN |
| Fatigue load limit Pu | 8.8 kN |
| Reference speed (thermal) | 8000 rpm |
| Limiting speed (mechanical) | 9000 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 160 g |
| Manufacturer designation | NKS 50 |
| 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 & NKS-series range
| Bore d | 1.969 in |
|---|---|
| Outer diameter D | 2.559 in |
| Width B | 0.866 in |
| ISO bore code | — |
| Radial section height (D−d)/2 | 7.5 mm |
| Smallest bore in NKS-series | 20 mm |
| Largest outer diameter in NKS-series | 95 mm |
| Width range across NKS-series | 20–28 mm |
| Bore position in NKS-series (smallest first) | 12 of 17 |
| Bore above smallest NKS-series size | 30 mm |
Cross references & equivalents
No verified interchange data yet. Send an inquiry and our team will confirm equivalents manually.
How the NKS50 model number is decoded
NKS 50 is a machined-ring needle roller bearing without an inner ring: a solid outer ring with integral flanges guiding the caged rollers, riding directly on a 50 mm hardened shaft journal, as listed in SKF catalogue PUB BU/P1 17000. Reading the designation: NKS gives the series and the numbers the boundary plan — 50 mm Fw for the shaft seat, 22 mm width; the 65 mm OD comes from the dimension series, and the absence of an inner ring is built into the family name. 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. Minimum load matters: below roughly 0.02·C the rollers skid and smear; preloading the pivot or specifying a heavier execution avoids the glazing that pure oscillation produces on these raceways. Fit the outer ring with a press and a fitting sleeve, not by hammering the flanges — rolled flanges chip; the 65 mm ground OD takes the press fit that prevents outer-ring creep in oscillating duty.
Typical equipment & failure modes
Common applications
- swing arms and lever pivots with oscillating duty
- 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
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
- rapid raceway scoring when the shaft journal hardness drops below 58 HRC or the ground finish wears away
Selection pitfalls — read before you substitute
- At 50 mm bore, verify shaft deflection against the needle length: these rollers tolerate little edge loading, and a simply supported span between 50 mm seats can bend past the compensation range long before the load rating is exhausted.
- The quoted 42.9/72 kN ratings are SKF catalogue values for this exact execution (NKS 50); ratings can be revised without the order number changing, so keep the catalogue version (SKF catalogue PUB BU/P1 17000) with the drawing.
- 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.
- The 42.9/72 kN ratings and 160 g mass are SKF catalogue values transcribed from ch. 7.3 of PUB BU/P1 17000 (PDF table page 632); 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 NKS 50?
Press on the ring faces only with a fitting sleeve, keep everything square to the 50 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 NKS 50 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 NKS 50 have?
A NKS 50 measures 50 mm bore/Fw × 65 mm outside diameter × 22 mm width (1.969 × 2.559 × 0.866 in). From SKF catalogue PUB BU/P1 17000: radial dynamic rating C 42.9 kN, static C0 72 kN, fatigue limit Pu 8.8 kN, limiting speed 9,000 r/min, reference speed 8,000 r/min, mass about 160 g.
What does NKS 50 mean in SKF part numbering?
NKS names a machined-ring needle roller bearing without inner ring: the figures give Fw 50 mm and width 22 mm, OD 65 mm comes from the dimension series, and the flanged outer ring retains the caged rollers.
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.