NKX50-Z bearing: complete specifications & equivalents
The NKX50-Z 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) | 3600 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 300 g |
| Manufacturer designation | NKX 50 Z |
| 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 | SKF | full Dimensions and internal design equivalent — standard interchange. | Same 50×62×35 mm envelope and equivalent catalogue ratings; NKX50 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-Z model number is decoded
The combined needle roller / thrust ball bearings with caged thrust part execution NKX 50 Z measures 50×62×35 mm and carries radial load 38 kN dynamic plus one-direction axial load 28.6 kN (Ca) — the caged thrust part runs at higher speed than full complement NX types. 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. Execution notes: the Z suffix adds a shield over the thrust balls, TN a polymer cage; the open execution allows relubrication through the shaft, the Z execution is greased for life. Selection arithmetic for the combined unit: radial C 38 kN, radial C0 78 kN, axial dynamic 28.6 kN (Ca) and axial static 81.5 kN (C0a); combine them with the equivalent-load factors from the catalogue before checking L10. The caged thrust part survives moderate speed only with the Z shield intact — damaged shields admit grit straight into the ball raceways, and the narrow section leaves no margin.
Typical equipment & failure modes
Common applications
- conveyor screw thrust ends
- turntable and swivel mounts
- machine tool feed spindles with one-direction thrust
- pump impeller shafts with steady axial pull
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
- grease starvation at the roller ends when relubrication intervals are stretched in dirty duty
- brinelling of raceways from impact or pressing force transmitted through the rolling elements
- thrust washer raceway wear from reverse axial shocks the one-direction thrust part cannot carry
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.
- 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: NKX 50 Z shares its 50×62×35 mm outline with inner-ring and sealed siblings whose ratings differ — the family letters are part of the specification, not decoration.
- 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 Z facing the working thrust.
- Minimum axial load is a real requirement: below factor A 0.034 the thrust elements skid, polish their raceways and lose them — springs or preload washers belong in the arrangement drawing, not the troubleshooting notes.
- The 38/78 kN ratings and 300 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
What mounting mistakes ruin a NKX 50 Z?
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 NKX 50 Z 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 Z have?
A NKX 50 Z 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 3,600 r/min, reference speed 4,300 r/min, mass about 300 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 Z 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.
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.