NX12-Z bearing: complete specifications & equivalents
The NX12-Z 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) | 5300 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 28 g |
| Manufacturer designation | NX 12 Z |
| 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 | SKF | full Dimensions and internal design equivalent — standard interchange. | Same 12×21×18 mm envelope and equivalent catalogue ratings; NX12 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-Z model number is decoded
NX 12 Z is a combined needle roller / full complement thrust ball bearing: a caged needle roller set for the 12 mm radial seat stacked with a maximum-ball-count thrust ball set, per SKF catalogue PUB BU/P1 17000 ch. 7.8. The number in NX 12 Z is the shaft diameter in millimetres; NX types differ from NKX only in the thrust part — full complement balls here, caged balls there — which changes axial capacity and speed ceiling. Full complement thrust parts run slower than caged ones: observe the 5,300 r/min limiting speed, and expect the thrust part to govern the thermal ceiling. 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. The full complement thrust set has no cage to retain the balls — hold them with grease during assembly and never rotate the shaft before the axial preload (at least factor A 0.00048) is applied.
Typical equipment & failure modes
Common applications
- actuator output shafts
- screw jack and lifting screw spindles
- valve and dosing pump stems with slow axial push
- light rotary tables under axial load
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
- abrasive paste formation from dust ingressing past open ends without effective housing seals
- brinelling of raceways from impact or pressing force transmitted through the rolling elements
- thrust-part ball or roller skidding and smearing when the axial load falls below the minimum factor
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.
- Oscillating pivots fail differently: rocking through a small angle concentrates wear in the same roller positions — inspect those zones, and consider rotating the assembly's clock position at service intervals.
- 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.
- 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 NX 12 Z facing the working thrust.
- Minimum axial load is a real requirement: below factor A 0.00048 the thrust elements skid, polish their raceways and lose them — springs or preload washers belong in the arrangement drawing, not the troubleshooting notes.
- 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
How should the NX 12 Z be mounted?
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.
What limits the service life of a NX 12 Z?
Beyond the L10 rating, the practical limits are journal/raceway hardness for the 12 mm seat, lubricant condition at the roller ends, and contamination through open ends — the 4.5 mm radial section leaves no reserve once a raceway is dented or ribboned.
What are the dimensions and ratings of the NX 12 Z?
A NX 12 Z 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 5,300 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.
How is the NX 12 Z designation read?
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.