NKX20-Z bearing: complete specifications & equivalents
The NKX20-Z is a DIN 616 radial bearing sized 20 x 30 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 | 20 mm |
| Outer diameter D | 30 mm |
| Width B | 30 mm |
| Material | GCr15 |
| Seal / shield | open |
| Internal clearance | CN |
| Tolerance class | P0 |
| Cage | none |
| Basic dynamic load rating C | 16.5 kN |
| Basic static load rating C0 | 25.5 kN |
| Fatigue load limit Pu | 3.05 kN |
| Reference speed (thermal) | 7500 rpm |
| Limiting speed (mechanical) | 6000 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 90 g |
| Manufacturer designation | NKX 20 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 | 0.787 in |
|---|---|
| Outer diameter D | 1.181 in |
| Width B | 1.181 in |
| ISO bore code | — |
| Radial section height (D−d)/2 | 5 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) | 5 of 13 |
| Bore above smallest NKX-series size | 10 mm |
Cross references & equivalents
| Equivalent model | Brand | Match level | Note |
|---|---|---|---|
| NKX20 | SKF | full Dimensions and internal design equivalent — standard interchange. | Same 20×30×30 mm envelope and equivalent catalogue ratings; NKX20 is the combined needle/thrust ball execution — boundary-dimension interchangeable, execution differences (seals, shields, cage) apply. |
| NKXR20 | SKF | full Dimensions and internal design equivalent — standard interchange. | Envelope-identical (20×30×30 mm) combined needle/thrust needle execution with ratings within 10 % — substitution possible after checking ring/flange construction. |
| NKXR20-Z | SKF | full Dimensions and internal design equivalent — standard interchange. | Envelope-identical (20×30×30 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 NKX20-Z model number is decoded
NKX 20 Z integrates two bearings in one envelope: needle rollers for the radial load on a 20 mm seat, and a cage-held thrust ball set for axial loads up to 14.3 kN (Ca) dynamic. Reading the designation: NKX marks needle roller + caged thrust ball, the number the 20 mm shaft seat; the 30 mm OD and 30 mm overall height come from the series plan. The thrust part takes axial load in one direction only; mount it facing the working load and provide a separate locating bearing for reverse events. Speed ceilings differ by part: 7,500 r/min thermal reference and 6,000 r/min limiting — the thrust element governs, since its washer faces see sliding components of contact. Apply the working axial load after mounting and re-check running torque; a rising torque in the first minutes signals balls climbing the washer lip under reversed thrust.
Typical equipment & failure modes
Common applications
- machine tool feed spindles with one-direction thrust
- pump impeller shafts with steady axial pull
- gear pairs generating one-direction axial force
- rotary indexing tables under combined load
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
- hard-particle indentation in unfiltered lubricant
- thrust washer raceway wear from reverse axial shocks the one-direction thrust part cannot carry
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 30 mm ring or cup into a lobed shape, and the rollers then trace the housing's geometry error, not the design load.
- Reference and limiting speeds are different limits: the 7,500 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 20 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 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 20 Z facing the working thrust.
- Minimum axial load is a real requirement: below factor A 0.0038 the thrust elements skid, polish their raceways and lose them — springs or preload washers belong in the arrangement drawing, not the troubleshooting notes.
- The 16.5/25.5 kN ratings and 90 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 20 Z?
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 NKX 20 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 20 Z have?
A NKX 20 Z measures 20 mm bore/Fw × 30 mm outside diameter × 30 mm width (0.787 × 1.181 × 1.181 in). From SKF catalogue PUB BU/P1 17000: radial dynamic rating C 16.5 kN, static C0 25.5 kN, fatigue limit Pu 3.05 kN, limiting speed 6,000 r/min, reference speed 7,500 r/min, mass about 90 g. Axial ratings of the thrust part: dynamic Ca 14.3 kN (Ca), static C0a 27 kN (C0a), minimum load factor A 0.0038; the thrust set carries load in one direction only.
What does NKX 20 Z mean in SKF part numbering?
NKX = needle roller radial part + caged thrust ball part for a 20 mm shaft: 30 mm OD, 30 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.