NKX30 bearing: complete specifications & equivalents
The NKX30 is a DIN 616 radial bearing sized 30 x 42 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 | 30 mm |
| Outer diameter D | 42 mm |
| Width B | 30 mm |
| Material | GCr15 |
| Seal / shield | open |
| Internal clearance | CN |
| Tolerance class | P0 |
| Cage | none |
| Basic dynamic load rating C | 22.9 kN |
| Basic static load rating C0 | 38 kN |
| Fatigue load limit Pu | 4.8 kN |
| Reference speed (thermal) | 6000 rpm |
| Limiting speed (mechanical) | 8500 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 140 g |
| Manufacturer designation | NKX 30 |
| 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 | 1.181 in |
|---|---|
| Outer diameter D | 1.654 in |
| Width B | 1.181 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) | 7 of 13 |
| Bore above smallest NKX-series size | 20 mm |
Cross references & equivalents
| Equivalent model | Brand | Match level | Note |
|---|---|---|---|
| NKX30-Z | SKF | full Dimensions and internal design equivalent — standard interchange. | Same 30×42×30 mm envelope and equivalent catalogue ratings; NKX30-Z is the combined needle/thrust ball execution — boundary-dimension interchangeable, execution differences (seals, shields, cage) apply. |
| RNA6905 | SKF | partial Main dimensions match; tolerances, seals or internal clearance differ. | Same 30×42×30 mm envelope, but catalogue C/C0 differ between the executions (22.9/38 vs 38/62 kN) — boundary dimensions match, not a load-rating equivalent. |
| NX30-Z | SKF | full Dimensions and internal design equivalent — standard interchange. | Envelope-identical (30×42×30 mm) combined needle/thrust ball execution with ratings within 10 % — substitution possible after checking ring/flange construction. |
| NX30 | SKF | full Dimensions and internal design equivalent — standard interchange. | Envelope-identical (30×42×30 mm) combined needle/thrust ball execution with ratings within 10 % — substitution possible after checking ring/flange construction. |
| NKXR30 | SKF | full Dimensions and internal design equivalent — standard interchange. | Envelope-identical (30×42×30 mm) combined needle/thrust needle execution with ratings within 10 % — substitution possible after checking ring/flange construction. |
| NKXR30-Z | SKF | full Dimensions and internal design equivalent — standard interchange. | Envelope-identical (30×42×30 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 NKX30 model number is decoded
In SKF catalogue PUB BU/P1 17000, NKX 30 designates a combined bearing with needle roller radial part and caged thrust ball part: 30 mm shaft seat, 42 mm OD, thrust dynamic rating 20.3 kN (Ca). Reading the designation: NKX marks needle roller + caged thrust ball, the number the 30 mm shaft seat; the 42 mm OD and 30 mm overall height come from the series plan. 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. 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. 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
- 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
- electrical erosion on VFD-driven shafts without brush or insulated mounting
- thrust-part ball or roller skidding and smearing when the axial load falls below the minimum factor
Selection pitfalls — read before you substitute
- At 30 mm bore, verify shaft deflection against the needle length: these rollers tolerate little edge loading, and a simply supported span between 30 mm seats can bend past the compensation range long before the load rating is exhausted.
- Reference and limiting speeds are different limits: the 6,000 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 30 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.
- Minimum axial load is a real requirement: below factor A 0.01 the thrust elements skid, polish their raceways and lose them — springs or preload washers belong in the arrangement drawing, not the troubleshooting notes.
- 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.
- The 22.9/38 kN ratings and 140 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
Which dimensions does the NKX 30 have?
A NKX 30 measures 30 mm bore/Fw × 42 mm outside diameter × 30 mm width (1.181 × 1.654 × 1.181 in). From SKF catalogue PUB BU/P1 17000: radial dynamic rating C 22.9 kN, static C0 38 kN, fatigue limit Pu 4.8 kN, limiting speed 8,500 r/min, reference speed 6,000 r/min, mass about 140 g. Axial ratings of the thrust part: dynamic Ca 20.3 kN (Ca), static C0a 45.5 kN (C0a), minimum load factor A 0.01; the thrust set carries load in one direction only.
What does NKX 30 mean in SKF part numbering?
NKX = needle roller radial part + caged thrust ball part for a 30 mm shaft: 42 mm OD, 30 mm overall height. The caged thrust part trades some axial capacity for higher permissible speed versus NX.
Does the NKX 30 need a hardened and ground shaft?
The radial needle part of the NKX 30 runs directly on the 30 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.
What mounting mistakes ruin a NKX 30?
Press on the ring faces only with a fitting sleeve, keep everything square to the 30 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.
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.