K50X55X20 bearing: complete specifications & equivalents
The K50X55X20 is a DIN 5402 radial bearing sized 50 x 55 x 20 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 | 55 mm |
| Width B | 20 mm |
| Material | GCr15 |
| Seal / shield | open |
| Internal clearance | CN |
| Tolerance class | P0 |
| Cage | none |
| Basic dynamic load rating C | 25.5 kN |
| Basic static load rating C0 | 60 kN |
| Fatigue load limit Pu | 7.2 kN |
| Reference speed (thermal) | 8500 rpm |
| Limiting speed (mechanical) | 9500 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 43 g |
| Manufacturer designation | K 50x55x20 |
| Standard | DIN 5402 |
| Catalog version | SKF PUB BU/P1 17000/1 EN (Oct 2018), ch. 7.1 needle roller and cage assemblies |
| Last verified | 2026-09-26 |
Source: catalog reference (SKF PUB BU/P1 17000/1 EN (Oct 2018), ch. 7.1 needle roller and cage assemblies) · extracted 2026-09-26
Parameters extracted from the official SKF Rolling Bearings catalogue (SKF PUB BU/P1 17000/1 EN (Oct 2018), ch. 7.1 needle roller and cage assemblies); 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 & K-series range
| Bore d | 1.969 in |
|---|---|
| Outer diameter D | 2.165 in |
| Width B | 0.787 in |
| ISO bore code | — |
| Radial section height (D−d)/2 | 2.5 mm |
| Smallest bore in K-series | 3 mm |
| Largest outer diameter in K-series | 63 mm |
| Width range across K-series | 7–32 mm |
| Bore position in K-series (smallest first) | 21 of 22 |
| Bore above smallest K-series size | 47 mm |
Cross references & equivalents
No verified interchange data yet. Send an inquiry and our team will confirm equivalents manually.
How the K50X55X20 model number is decoded
K 50x55x20 is a needle roller and cage assembly to DIN 5402: a complement of needle rollers held by a lightweight cage, with no inner or outer ring of its own — the 50 mm hardened shaft journal and the 55 mm housing bore serve as the raceways, as tabulated in SKF catalogue PUB BU/P1 17000. Reading the designation: K marks the needle roller and cage assembly, the three numbers give Fw 50 (shaft journal), E 55 (assembly outside diameter) and B 20 (width) in millimetres — the machine parts complete the bearing. SKF supplies these assemblies in single rows as tabulated; the cage quality determines the speed ceiling, and the catalogued 9,500 r/min limiting speed assumes a precision ground journal and bore. Catalogue mass 43 g at 50×55×20 mm makes this one of the highest capacity-per-gram choices in the needle roller and cage assemblies; the limit is usually the shaft's ability to serve as a raceway, not the rolling contact itself. Mounting: grind the 50 mm journal to the catalogue raceway tolerance after hardening to 58–64 HRC, bore the housing to E 55 mm H6, and slide the assembly in axially — pressing through the cage distorts it and locks the rollers.
Typical equipment & failure modes
Common applications
- planetary gear pins in compact transmissions
- connecting rods of small compressors where radial height is critical
- rocker arm and rocker pin pivots on camshafts
- pump and gearbox idler gears running on hardened pins
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
- rolling-contact fatigue spalling after the rated L10 life
- rapid raceway scoring when the shaft journal hardness drops below 58 HRC or the ground finish wears away
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 8,500 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 25.5/60 kN ratings and 43 g mass are SKF catalogue values transcribed from ch. 7.1 of PUB BU/P1 17000 (PDF table page 618); combined-type axial ratings appear in the text above because the structured record carries radial values only.
Frequently asked questions
Does the K 50x55x20 need a hardened and ground shaft?
No. In this execution the 50 mm shaft journal is the inner raceway: it must be ground and hardened to 58–64 HRC (with matching housing bore quality on the outside). If the shaft cannot meet that, order the inner-ring sibling (NKI/NA execution) plus its ground inner ring instead.
What mounting mistakes ruin a K 50x55x20?
Slide the assembly over the ground 50 mm journal with a mounting sleeve, bore the housing to E 55 mm, and retain with a washer spanning the cage. Never press against the cage or rotate before the bearing is lubricated and loaded.
Is the K 50x55x20 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 K 50x55x20 have?
A K 50x55x20 measures 50 mm bore/Fw × 55 mm outside diameter × 20 mm width (1.969 × 2.165 × 0.787 in). From SKF catalogue PUB BU/P1 17000: radial dynamic rating C 25.5 kN, static C0 60 kN, fatigue limit Pu 7.2 kN, limiting speed 9,500 r/min, reference speed 8,500 r/min, mass about 43 g.
Reviewed & verified by the MPN Base engineering desk against source catalog SKF PUB BU/P1 17000/1 EN (Oct 2018), ch. 7.1 needle roller and cage assemblies on 2026-09-26. Read our editorial & correction policy.