NKXR50-Z bearing: complete specifications & equivalents
The NKXR50-Z is a DIN 616 radial bearing sized 50 x 62 x 35 mm (bore x OD x width). Verify dimensions against the official catalog before ordering.
Specification table
| Parameter | Value |
|---|---|
| Brand | SKF |
| Bore diameter d | 50 mm |
| Outer diameter D | 62 mm |
| Width B | 35 mm |
| Material | GCr15 |
| Seal / shield | open |
| Internal clearance | CN |
| Tolerance class | P0 |
| Cage | none |
| Basic dynamic load rating C | 38 kN |
| Basic static load rating C0 | 78 kN |
| Fatigue load limit Pu | 9.65 kN |
| Reference speed (thermal) | 2200 rpm |
| Limiting speed (mechanical) | 4300 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 290 g |
| Manufacturer designation | NKXR 50 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 | 1.969 in |
|---|---|
| Outer diameter D | 2.441 in |
| Width B | 1.378 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) | 9 of 9 |
| Bore above smallest NKXR-series size | 35 mm |
Cross references & equivalents
| Equivalent model | Brand | Match level | Note |
|---|---|---|---|
| NKXR50 | SKF | full Dimensions and internal design equivalent — standard interchange. | Same 50×62×35 mm envelope and equivalent catalogue ratings; NKXR50 is the combined needle/thrust needle execution — boundary-dimension interchangeable, execution differences (seals, shields, cage) apply. |
| NK50-35-TN | SKF | partial Main dimensions match; tolerances, seals or internal clearance differ. | Same 50×62×35 mm envelope, but catalogue C/C0 differ between the executions (38/78 vs 58.3/137 kN) — boundary dimensions match, not a load-rating equivalent. |
| NKX50-Z | SKF | full Dimensions and internal design equivalent — standard interchange. | Envelope-identical (50×62×35 mm) combined needle/thrust ball execution with ratings within 10 % — substitution possible after checking ring/flange construction. |
| NKX50 | SKF | full Dimensions and internal design equivalent — standard interchange. | Envelope-identical (50×62×35 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 NKXR50-Z model number is decoded
NKXR 50 Z is the heavy-thrust member of the combined needle roller family: 50 mm radial seat, 62 mm OD, and a full complement of thrust needles rated 47.5 kN (Ca) dynamic / 166 kN (C0a) static. In SKF nomenclature NKXR is the highest-capacity combined family: 50 mm shaft seat, packed thrust needles above the radial cage, axial rating 47.5 kN (Ca) dynamic. Thrust needle sets tolerate slow speeds and heavy loads: the 4,300 r/min limiting speed is far below ball-thrust equivalents, and lubricant film at the washer faces governs life. Selection arithmetic for the combined unit: radial C 38 kN, radial C0 78 kN, axial dynamic 47.5 kN (Ca) and axial static 166 kN (C0a); combine them with the equivalent-load factors from the catalogue before checking L10. Fit with a press against the washer faces only — needles packed without a cage will skew if the assembly is dropped or driven sideways onto the 50 mm seat.
Typical equipment & failure modes
Common applications
- extruder and mixer thrust positions
- large valve stems under high axial load
- turntables and slewing pivots with shock loads
- press-fit die set guide positions
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
- brinelling of raceways from impact or pressing force transmitted through the rolling elements
- thrust washer raceway wear from reverse axial shocks the one-direction thrust part cannot carry
Selection pitfalls — read before you substitute
- At 50 mm bore, verify shaft deflection against the needle length: these rollers tolerate little edge loading, and a simply supported span between 50 mm seats can bend past the compensation range long before the load rating is exhausted.
- Reference and limiting speeds are different limits: the 2,200 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 50 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 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 50 Z facing the working thrust.
- Minimum axial load is a real requirement: below factor A 0.0022 the thrust elements skid, polish their raceways and lose them — springs or preload washers belong in the arrangement drawing, not the troubleshooting notes.
- The 38/78 kN ratings and 290 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
Which dimensions does the NKXR 50 Z have?
A NKXR 50 Z measures 50 mm bore/Fw × 62 mm outside diameter × 35 mm width (1.969 × 2.441 × 1.378 in). From SKF catalogue PUB BU/P1 17000: radial dynamic rating C 38 kN, static C0 78 kN, fatigue limit Pu 9.65 kN, limiting speed 4,300 r/min, reference speed 2,200 r/min, mass about 290 g. Axial ratings of the thrust part: dynamic Ca 47.5 kN (Ca), static C0a 166 kN (C0a), minimum load factor A 0.0022; the thrust set carries load in one direction only.
What does NKXR 50 Z mean in SKF part numbering?
NKXR = needle roller radial part + full complement needle thrust part for a 50 mm shaft: 62 mm OD, 35 mm overall height, the highest axial rating of the combined needle families.
Does the NKXR 50 Z need a hardened and ground shaft?
The radial needle part of the NKXR 50 Z runs directly on the 50 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 NKXR 50 Z?
Press on the ring faces only with a fitting sleeve, keep everything square to the 50 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. 7.10 needle roller / cylindrical-needle thrust on 2026-09-26. Read our editorial & correction policy.