RPNA40-55 bearing: complete specifications & equivalents
The RPNA40-55 is a DIN 616 radial bearing sized 40 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 | 40 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 | 26.4 kN |
| Basic static load rating C0 | 51 kN |
| Fatigue load limit Pu | 6.3 kN |
| Reference speed (thermal) | 10000 rpm |
| Limiting speed (mechanical) | 11000 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 140 g |
| Manufacturer designation | RPNA 40/55 |
| Standard | DIN 616 |
| Catalog version | SKF PUB BU/P1 17000/1 EN (Oct 2018), ch. 7.5 alignment needle roller bearings, without an inner ring |
| Last verified | 2026-09-26 |
Source: catalog reference (SKF PUB BU/P1 17000/1 EN (Oct 2018), ch. 7.5 alignment needle roller bearings, without an inner ring) · extracted 2026-09-26
Parameters extracted from the official SKF Rolling Bearings catalogue (SKF PUB BU/P1 17000/1 EN (Oct 2018), ch. 7.5 alignment needle roller bearings, without an inner ring); 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 & RPNA-series range
| Bore d | 1.575 in |
|---|---|
| Outer diameter D | 2.165 in |
| Width B | 0.787 in |
| ISO bore code | — |
| Radial section height (D−d)/2 | 7.5 mm |
| Smallest bore in RPNA-series | 15 mm |
| Largest outer diameter in RPNA-series | 62 mm |
| Width range across RPNA-series | 12–20 mm |
| Bore position in RPNA-series (smallest first) | 7 of 8 |
| Bore above smallest RPNA-series size | 25 mm |
Cross references & equivalents
| Equivalent model | Brand | Match level | Note |
|---|---|---|---|
| NKI40-20-TN | SKF | partial Main dimensions match; tolerances, seals or internal clearance differ. | Same 40×55×20 mm envelope, but catalogue C/C0 differ between the executions (26.4/51 vs 31.4/65.5 kN) — boundary dimensions match, not a load-rating equivalent. |
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 RPNA40-55 model number is decoded
In SKF catalogue PUB BU/P1 17000, RPNA 40/55 denotes an alignment needle roller bearing for a 40 mm shaft: machined rings, integral flanges, and a spherical outside surface that compensates static misalignment of the housing bore. The code RPNA 40/55 reads as alignment needle roller bearing, 40 mm bore, 20 mm width — the wide section is what absorbs both load and the seat-angle errors the family is designed for. These are heavy-section machined rings, not drawn cups: the sphered outside surface is ground, the flanges retain the rollers, and the PNA execution adds the ground inner ring for unhardened shafts. For life calculation, the 26.4/51 kN ratings assume raceway geometry supplied by the shaft and housing in families without an inner ring — journal hardness, roundness and finish are part of the bearing, not of the application. Mounting: seat the convex outer ring surface in its sphered counterpart dry first, confirm the 40 mm raceway rotates freely through the full alignment range, then lubricate and assemble for service.
Typical equipment & failure modes
Common applications
- agricultural machinery joints exposed to frame distortion
- door and gate hinges with heavy radial load
- construction equipment blade and arm pivots
- steering knuckles and kingpin supports with seat angle errors
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
- corrosion pitting from condensation in intermittently operated machinery
Selection pitfalls — read before you substitute
- At 40 mm bore, verify shaft deflection against the needle length: these rollers tolerate little edge loading, and a simply supported span between 40 mm seats can bend past the compensation range long before the load rating is exhausted.
- 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 26.4/51 kN ratings and 140 g mass are SKF catalogue values transcribed from ch. 7.5 of PUB BU/P1 17000 (PDF table page 650); combined-type axial ratings appear in the text above because the structured record carries radial values only.
Frequently asked questions
Can the RPNA 40/55 run on an unhardened shaft?
Depends on the family member: RPNA runs directly on the shaft (hardened, 58–64 HRC, ground), while PNA includes a ground inner ring for an ordinary 40 mm k5 seat. Both add the sphered outer ring for seat misalignment.
How should the RPNA 40/55 be mounted?
Press on the ring faces only with a fitting sleeve, keep everything square to the 40 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 RPNA 40/55?
Beyond the L10 rating, the practical limits are journal/raceway hardness for the 40 mm seat, lubricant condition at the roller ends, and contamination through open ends — the 7.5 mm radial section leaves no reserve once a raceway is dented or ribboned.
What are the dimensions and ratings of the RPNA 40/55?
A RPNA 40/55 measures 40 mm bore/Fw × 55 mm outside diameter × 20 mm width (1.575 × 2.165 × 0.787 in). From SKF catalogue PUB BU/P1 17000: radial dynamic rating C 26.4 kN, static C0 51 kN, fatigue limit Pu 6.3 kN, limiting speed 11,000 r/min, reference speed 10,000 r/min, mass about 140 g.
Reviewed & verified by the MPN Base engineering desk against source catalog SKF PUB BU/P1 17000/1 EN (Oct 2018), ch. 7.5 alignment needle roller bearings, without an inner ring on 2026-09-26. Read our editorial & correction policy.