NKX50 bearing: complete specifications & equivalents
The NKX50 is a DIN 616 radial bearing sized 50 x 62 x 35 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 | 62 mm |
| Width B | 35 mm |
| Material | GCr15 |
| Seal / shield | open |
| Internal clearance | CN |
| Tolerance class | P0 |
| Cage | none |
| Basic dynamic load rating C | 38 kN |
| Basic static load rating C0 | 78 kN |
| Fatigue load limit Pu | 9.65 kN |
| Reference speed (thermal) | 4300 rpm |
| Limiting speed (mechanical) | 6300 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 280 g |
| Manufacturer designation | NKX 50 |
| Standard | DIN 616 |
| Catalog version | SKF PUB BU/P1 17000/1 EN (Oct 2018), ch. 7.9 needle roller / thrust ball, caged thrust part |
| Last verified | 2026-09-26 |
Source: catalog reference (SKF PUB BU/P1 17000/1 EN (Oct 2018), ch. 7.9 needle roller / thrust ball, caged thrust part) · extracted 2026-09-26
Parameters extracted from the official SKF Rolling Bearings catalogue (SKF PUB BU/P1 17000/1 EN (Oct 2018), ch. 7.9 needle roller / thrust ball, caged thrust part); 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 & NKX-series range
| Bore d | 1.969 in |
|---|---|
| Outer diameter D | 2.441 in |
| Width B | 1.378 in |
| ISO bore code | — |
| Radial section height (D−d)/2 | 6 mm |
| Smallest bore in NKX-series | 10 mm |
| Largest outer diameter in NKX-series | 85 mm |
| Width range across NKX-series | 23–40 mm |
| Bore position in NKX-series (smallest first) | 11 of 13 |
| Bore above smallest NKX-series size | 40 mm |
Cross references & equivalents
| Equivalent model | Brand | Match level | Note |
|---|---|---|---|
| NKX50-Z | SKF | full Dimensions and internal design equivalent — standard interchange. | Same 50×62×35 mm envelope and equivalent catalogue ratings; NKX50-Z is the combined needle/thrust ball execution — boundary-dimension interchangeable, execution differences (seals, shields, cage) apply. |
| NK50-35-TN | SKF | partial Main dimensions match; tolerances, seals or internal clearance differ. | Same 50×62×35 mm envelope, but catalogue C/C0 differ between the executions (38/78 vs 58.3/137 kN) — boundary dimensions match, not a load-rating equivalent. |
| NKXR50 | SKF | full Dimensions and internal design equivalent — standard interchange. | Envelope-identical (50×62×35 mm) combined needle/thrust needle execution with ratings within 10 % — substitution possible after checking ring/flange construction. |
| NKXR50-Z | SKF | full Dimensions and internal design equivalent — standard interchange. | Envelope-identical (50×62×35 mm) combined needle/thrust needle execution with ratings within 10 % — substitution possible after checking ring/flange construction. |
Interchange levels: full standard interchange · partial verify parameters · verify manual confirmation required. Links resolve to the equivalent model's specification page where available.
How the NKX50 model number is decoded
In SKF catalogue PUB BU/P1 17000, NKX 50 designates a combined bearing with needle roller radial part and caged thrust ball part: 50 mm shaft seat, 62 mm OD, thrust dynamic rating 28.6 kN (Ca). In SKF nomenclature NKX is the combined family: the number states 50 mm, and unlike NX the thrust balls are caged, trading some axial capacity for speed and friction. Caged thrust balls allow higher speeds than the full complement NX execution in the same envelope; the trade-off is a somewhat lower axial rating — compare the Ca figures before choosing. Axial capability is one-direction: size the arrangement so working thrust pushes the thrust-washer face, and provide a mirrored unit or separate bearing for load reversals. Mounting: press the unit onto the 50 mm seat against the inner faces, orient the thrust set toward the axial load, and verify the 35 mm overall height against the housing stack after fitting.
Typical equipment & failure modes
Common applications
- turntable and swivel mounts
- machine tool feed spindles with one-direction thrust
- pump impeller shafts with steady axial pull
- gear pairs generating one-direction axial force
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
- grease starvation at the roller ends when relubrication intervals are stretched in dirty duty
- rolling-contact fatigue spalling after the rated L10 life
- thrust-part ball or roller skidding and smearing when the axial load falls below the minimum factor
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 38/78 kN ratings are SKF catalogue values for this exact execution (NKX 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.
- Do not treat the axial rating 28.6 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 thrust part is one-direction: reverse axial events — however brief — lift the rolling elements off the raceway, and the subsequent re-entry impact dents the washer face; mount the NKX 50 facing the working thrust.
- The 38/78 kN ratings and 280 g mass are SKF catalogue values transcribed from ch. 7.9 of PUB BU/P1 17000 (PDF table page 658); combined-type axial ratings appear in the text above because the structured record carries radial values only.
Frequently asked questions
Is the NKX 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 NKX 50 have?
A NKX 50 measures 50 mm bore/Fw × 62 mm outside diameter × 35 mm width (1.969 × 2.441 × 1.378 in). From SKF catalogue PUB BU/P1 17000: radial dynamic rating C 38 kN, static C0 78 kN, fatigue limit Pu 9.65 kN, limiting speed 6,300 r/min, reference speed 4,300 r/min, mass about 280 g. Axial ratings of the thrust part: dynamic Ca 28.6 kN (Ca), static C0a 81.5 kN (C0a), minimum load factor A 0.034; the thrust set carries load in one direction only.
What does NKX 50 mean in SKF part numbering?
NKX = needle roller radial part + caged thrust ball part for a 50 mm shaft: 62 mm OD, 35 mm overall height. The caged thrust part trades some axial capacity for higher permissible speed versus NX.
Does the NKX 50 need a hardened and ground shaft?
The radial needle part of the NKX 50 runs directly on the 50 mm journal — harden to 58–64 HRC and grind it. The thrust washers are integral, so no separate inner ring exists; size the shaft for the raceway tolerances in the catalogue table.
Reviewed & verified by the MPN Base engineering desk against source catalog SKF PUB BU/P1 17000/1 EN (Oct 2018), ch. 7.9 needle roller / thrust ball, caged thrust part on 2026-09-26. Read our editorial & correction policy.