NKXR25-Z bearing: complete specifications & equivalents
The NKXR25-Z is a DIN 616 radial bearing sized 25 x 37 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 | 25 mm |
| Outer diameter D | 37 mm |
| Width B | 30 mm |
| Material | GCr15 |
| Seal / shield | open |
| Internal clearance | CN |
| Tolerance class | P0 |
| Cage | none |
| Basic dynamic load rating C | 19 kN |
| Basic static load rating C0 | 32.5 kN |
| Fatigue load limit Pu | 4 kN |
| Reference speed (thermal) | 3200 rpm |
| Limiting speed (mechanical) | 6300 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 130 g |
| Manufacturer designation | NKXR 25 Z |
| Standard | DIN 616 |
| Catalog version | SKF PUB BU/P1 17000/1 EN (Oct 2018), ch. 7.10 needle roller / cylindrical-needle thrust |
| Last verified | 2026-09-26 |
Source: catalog reference (SKF PUB BU/P1 17000/1 EN (Oct 2018), ch. 7.10 needle roller / cylindrical-needle thrust) · extracted 2026-09-26
Parameters extracted from the official SKF Rolling Bearings catalogue (SKF PUB BU/P1 17000/1 EN (Oct 2018), ch. 7.10 needle roller / cylindrical-needle thrust); 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 & NKXR-series range
| Bore d | 0.984 in |
|---|---|
| Outer diameter D | 1.457 in |
| Width B | 1.181 in |
| ISO bore code | — |
| Radial section height (D−d)/2 | 6 mm |
| Smallest bore in NKXR-series | 15 mm |
| Largest outer diameter in NKXR-series | 62 mm |
| Width range across NKXR-series | 23–35 mm |
| Bore position in NKXR-series (smallest first) | 4 of 9 |
| Bore above smallest NKXR-series size | 10 mm |
Cross references & equivalents
| Equivalent model | Brand | Match level | Note |
|---|---|---|---|
| NKXR25 | SKF | full Dimensions and internal design equivalent — standard interchange. | Same 25×37×30 mm envelope and equivalent catalogue ratings; NKXR25 is the combined needle/thrust needle execution — boundary-dimension interchangeable, execution differences (seals, shields, cage) apply. |
| RNA6904 | SKF | partial Main dimensions match; tolerances, seals or internal clearance differ. | Same 25×37×30 mm envelope, but catalogue C/C0 differ between the executions (19/32.5 vs 35.2/53 kN) — boundary dimensions match, not a load-rating equivalent. |
| NX25-Z | SKF | partial Main dimensions match; tolerances, seals or internal clearance differ. | Same 25×37×30 mm envelope, but catalogue C/C0 differ between the executions (19/32.5 vs 15.1/24.5 kN) — boundary dimensions match, not a load-rating equivalent. |
| NX25 | SKF | partial Main dimensions match; tolerances, seals or internal clearance differ. | Same 25×37×30 mm envelope, but catalogue C/C0 differ between the executions (19/32.5 vs 15.1/24.5 kN) — boundary dimensions match, not a load-rating equivalent. |
| NKX25-Z | SKF | full Dimensions and internal design equivalent — standard interchange. | Envelope-identical (25×37×30 mm) combined needle/thrust ball execution with ratings within 10 % — substitution possible after checking ring/flange construction. |
| NKX25 | SKF | full Dimensions and internal design equivalent — standard interchange. | Envelope-identical (25×37×30 mm) combined needle/thrust ball 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 NKXR25-Z model number is decoded
In SKF catalogue PUB BU/P1 17000, NKXR 25 Z denotes a combined bearing with needle roller radial part and full complement thrust needle part for one-direction axial loads at slow to moderate speed. The code NKXR 25 Z identifies the construction exactly — needle radial part, needle thrust part — for a 25 mm shaft; the thrust set is one-directional and must face the working axial load. Thrust needle sets tolerate slow speeds and heavy loads: the 6,300 r/min limiting speed is far below ball-thrust equivalents, and lubricant film at the washer faces governs life. Speed ceilings differ by part: 3,200 r/min thermal reference and 6,300 r/min limiting — the thrust element governs, since its washer faces see sliding components of contact. Mounting: the thrust needle complement is held by grease during assembly; fill the washer set, orient toward the axial load, and preload to at least factor A 0.00039 before rotating.
Typical equipment & failure modes
Common applications
- turntables and slewing pivots with shock loads
- press-fit die set guide positions
- heavy screw presses and clamping spindles
- crane slew rings and kingposts at low speed
Known failure patterns
- raceway spalling once the catalogue L10 life is exceeded or after overload events
- 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
- rolling-contact fatigue spalling after the rated L10 life
- 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 25 mm seat the housing bore quality dominates life: a bore 0.02 mm out of round pinches the 37 mm ring or cup into a lobed shape, and the rollers then trace the housing's geometry error, not the design load.
- Hardness is load capacity: in families without an inner ring the 25 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 quoted 19/32.5 kN ratings are SKF catalogue values for this exact execution (NKXR 25 Z); ratings can be revised without the order number changing, so keep the catalogue version (SKF catalogue PUB BU/P1 17000) with the drawing.
- Do not treat the axial rating 25 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 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 NKXR 25 Z facing the working thrust.
- The 19/32.5 kN ratings and 130 g mass are SKF catalogue values transcribed from ch. 7.10 of PUB BU/P1 17000 (PDF table page 660); combined-type axial ratings appear in the text above because the structured record carries radial values only.
Frequently asked questions
How is the NKXR 25 Z designation read?
NKXR = needle roller radial part + full complement needle thrust part for a 25 mm shaft: 37 mm OD, 30 mm overall height, the highest axial rating of the combined needle families.
Can the NKXR 25 Z run on an unhardened shaft?
The radial needle part of the NKXR 25 Z runs directly on the 25 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.
How should the NKXR 25 Z be mounted?
Press on the ring faces only with a fitting sleeve, keep everything square to the 25 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 NKXR 25 Z?
Beyond the L10 rating, the practical limits are journal/raceway hardness for the 25 mm seat, lubricant condition at the roller ends, and contamination through open ends — the 6.0 mm radial section leaves no reserve once a raceway is dented or ribboned.
Reviewed & verified by the MPN Base engineering desk against source catalog SKF PUB BU/P1 17000/1 EN (Oct 2018), ch. 7.10 needle roller / cylindrical-needle thrust on 2026-09-26. Read our editorial & correction policy.