K50X55X30 bearing: complete specifications & equivalents
The K50X55X30 is a DIN 5402 radial bearing sized 50 x 55 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 | 50 mm |
| Outer diameter D | 55 mm |
| Width B | 30 mm |
| Material | GCr15 |
| Seal / shield | open |
| Internal clearance | CN |
| Tolerance class | P0 |
| Cage | none |
| Basic dynamic load rating C | 37.4 kN |
| Basic static load rating C0 | 98 kN |
| Fatigue load limit Pu | 12 kN |
| Reference speed (thermal) | 8500 rpm |
| Limiting speed (mechanical) | 9500 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 65 g |
| Manufacturer designation | K 50x55x30 |
| 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 | 1.181 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 K50X55X30 model number is decoded
For pivots and crank pins where every millimetre of radial height counts, SKF supplies K 50x55x30: needle rollers in a pressed cage (DIN 5402 boundary plan), dimensioned Fw 50 × E 55 × B 30 mm. In the K code K 50x55x30, Fw×E×B reads directly as journal 50 mm, complement diameter 55 mm and cage width 30 mm; the housing bore is ground to E with H6/H7 tolerance to complete the outer raceway. 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 65 g at 50×55×30 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. Lubrication reaches both raceways through the open cage windows; grease the bore and journal before assembly, since after fitting the 30 mm narrow cage cannot be relubricated through a closed housing.
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
- 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
- grease starvation at the roller ends when relubrication intervals are stretched in dirty duty
- hard-particle indentation in unfiltered lubricant
- smearing of rollers and journal during idle periods because the radial section holds too little lubricant
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.
- 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 quoted 37.4/98 kN ratings are SKF catalogue values for this exact execution (K 50x55x30); ratings can be revised without the order number changing, so keep the catalogue version (SKF catalogue PUB BU/P1 17000) with the drawing.
- The 37.4/98 kN ratings and 65 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
What limits the service life of a K 50x55x30?
Beyond the L10 rating, the practical limits are journal/raceway hardness for the 50 mm seat, lubricant condition at the roller ends, and contamination through open ends — the 2.5 mm radial section leaves no reserve once a raceway is dented or ribboned.
What are the dimensions and ratings of the K 50x55x30?
A K 50x55x30 measures 50 mm bore/Fw × 55 mm outside diameter × 30 mm width (1.969 × 2.165 × 1.181 in). From SKF catalogue PUB BU/P1 17000: radial dynamic rating C 37.4 kN, static C0 98 kN, fatigue limit Pu 12 kN, limiting speed 9,500 r/min, reference speed 8,500 r/min, mass about 65 g.
How is the K 50x55x30 designation read?
K = needle roller and cage assembly (DIN 5402); the three figures give Fw 50 mm (shaft journal), E 55 mm (complement outside diameter, matched by the housing bore) and B 30 mm width. TN marks the glass fibre reinforced PA66 cage.
Can the K 50x55x30 run on an unhardened 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.
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.