NX12 bearing: complete specifications & equivalents
The NX12 is a DIN 616 radial bearing sized 12 x 21 x 18 mm (bore x OD x width). Verify dimensions against the official catalog before ordering.
Specification table
| Parameter | Value |
|---|---|
| Brand | SKF |
| Bore diameter d | 12 mm |
| Outer diameter D | 21 mm |
| Width B | 18 mm |
| Material | GCr15 |
| Seal / shield | open |
| Internal clearance | CN |
| Tolerance class | P0 |
| Cage | none |
| Basic dynamic load rating C | 5.39 kN |
| Basic static load rating C0 | 5.2 kN |
| Fatigue load limit Pu | 0.61 kN |
| Reference speed (thermal) | 8000 rpm |
| Limiting speed (mechanical) | 9000 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 28 g |
| Manufacturer designation | NX 12 |
| Standard | DIN 616 |
| Catalog version | SKF PUB BU/P1 17000/1 EN (Oct 2018), ch. 7.8 needle roller / thrust ball, full complement thrust part |
| Last verified | 2026-09-26 |
Source: catalog reference (SKF PUB BU/P1 17000/1 EN (Oct 2018), ch. 7.8 needle roller / thrust ball, full complement 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. 7.8 needle roller / thrust ball, full complement 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 & NX-series range
| Bore d | 0.472 in |
|---|---|
| Outer diameter D | 0.827 in |
| Width B | 0.709 in |
| ISO bore code | — |
| Radial section height (D−d)/2 | 4.5 mm |
| Smallest bore in NX-series | 7 mm |
| Largest outer diameter in NX-series | 47 mm |
| Width range across NX-series | 18–30 mm |
| Bore position in NX-series (smallest first) | 3 of 9 |
| Bore above smallest NX-series size | 5 mm |
Cross references & equivalents
| Equivalent model | Brand | Match level | Note |
|---|---|---|---|
| NX12-Z | SKF | full Dimensions and internal design equivalent — standard interchange. | Same 12×21×18 mm envelope and equivalent catalogue ratings; NX12-Z is the combined needle/thrust ball execution — boundary-dimension interchangeable, execution differences (seals, shields, cage) apply. |
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 NX12 model number is decoded
The combined needle roller / full complement thrust ball bearings execution NX 12 measures 12×21×18 mm: radial duty on caged needle rollers, axial duty on a full complement of thrust balls rated 5.27 kN (Ca), both in one shaft position. Reading the designation: NX marks needle roller + full complement thrust ball, the number the 12 mm shaft seat; 21 mm OD and 18 mm overall height follow the series plan. The thrust washer set is keyed to the housing, the ball complement to the shaft washer — assembly orientation matters, since reverse axial shocks would unload the packed ball set. Selection arithmetic for the combined unit: radial C 5.39 kN, radial C0 5.2 kN, axial dynamic 5.27 kN (Ca) and axial static 9.65 kN (C0a); combine them with the equivalent-load factors from the catalogue before checking L10. Mounting: assemble the thrust washer set with the keyed washer in the housing, fill the packed ball complement with grease so the balls adhere during fitting, and orient the thrust part toward the working axial load.
Typical equipment & failure modes
Common applications
- screw jack and lifting screw spindles
- valve and dosing pump stems with slow axial push
- light rotary tables under axial load
- oscillating pivots with steady axial preload
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
- 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 12 mm seat the housing bore quality dominates life: a bore 0.02 mm out of round pinches the 21 mm ring or cup into a lobed shape, and the rollers then trace the housing's geometry error, not the design load.
- 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: NX 12 shares its 12×21×18 mm outline with inner-ring and sealed siblings whose ratings differ — the family letters are part of the specification, not decoration.
- 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 5.27 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 5.39/5.2 kN ratings and 28 g mass are SKF catalogue values transcribed from ch. 7.8 of PUB BU/P1 17000 (PDF table page 656); 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 NX 12?
Press on the ring faces only with a fitting sleeve, keep everything square to the 12 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 NX 12 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 NX 12 have?
A NX 12 measures 12 mm bore/Fw × 21 mm outside diameter × 18 mm width (0.472 × 0.827 × 0.709 in). From SKF catalogue PUB BU/P1 17000: radial dynamic rating C 5.39 kN, static C0 5.2 kN, fatigue limit Pu 0.61 kN, limiting speed 9,000 r/min, reference speed 8,000 r/min, mass about 28 g. Axial ratings of the thrust part: dynamic Ca 5.27 kN (Ca), static C0a 9.65 kN (C0a), minimum load factor A 0.00048; the thrust set carries load in one direction only.
What does NX 12 mean in SKF part numbering?
NX = needle roller radial part + full complement thrust ball part for a 12 mm shaft; the catalogue plan completes 21 mm OD and 18 mm overall height. The packed thrust set maximises axial capacity at low speed.
Reviewed & verified by the MPN Base engineering desk against source catalog SKF PUB BU/P1 17000/1 EN (Oct 2018), ch. 7.8 needle roller / thrust ball, full complement thrust part on 2026-09-26. Read our editorial & correction policy.