NKX20 bearing: complete specifications & equivalents
The NKX20 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) | 10000 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 83 g |
| Manufacturer designation | NKX 20 |
| 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-Z | SKF | full Dimensions and internal design equivalent — standard interchange. | Same 20×30×30 mm envelope and equivalent catalogue ratings; NKX20-Z 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 model number is decoded
For a 20 mm shaft under radial plus one-direction axial load, NKX 20 from the combined needle roller / thrust ball bearings with caged thrust part provides both in 30×30 mm: needle roller cage below, caged thrust ball set above. The code NKX 20 reads as combined radial/thrust for a 20 mm shaft; the catalogue height 30 mm stacks the radial cage and the thrust set, and the 30 mm OD seats both parts in one bore. 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. The minimum load factor A 0.0038 applies to the thrust part: below that axial load the rolling elements of the thrust set skid, so springs or preload washers are part of the arrangement, not an afterthought. Mounting: press the unit onto the 20 mm seat against the inner faces, orient the thrust set toward the axial load, and verify the 30 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
- raceway spalling once the catalogue L10 life is exceeded or after overload events
- 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
- corrosion pitting from condensation in intermittently operated machinery
- 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.
- Do not interchange envelope-identical needle families blindly: NKX 20 shares its 20×30×30 mm outline with inner-ring and sealed siblings whose ratings differ — the family letters are part of the specification, not decoration.
- 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.
- Height stack-up is easy to mis-check: the thrust-washer part adds height beyond a plain needle bearing, and clamping the stack solid over it preloads the thrust set beyond its rating.
- Do not treat the axial rating 14.3 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 16.5/25.5 kN ratings and 83 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
How should the NKX 20 be mounted?
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.
What limits the service life of a NKX 20?
Beyond the L10 rating, the practical limits are journal/raceway hardness for the 20 mm seat, lubricant condition at the roller ends, and contamination through open ends — the 5.0 mm radial section leaves no reserve once a raceway is dented or ribboned.
What are the dimensions and ratings of the NKX 20?
A NKX 20 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 10,000 r/min, reference speed 7,500 r/min, mass about 83 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.
How is the NKX 20 designation read?
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.