NA4905-2RS bearing: complete specifications & equivalents
The NA4905-2RS is a ISO 1206 radial bearing sized 25 x 42 x 18 mm (bore x OD x width) with 2RS sealing. Verify dimensions against the official catalog before ordering.
Specification table
| Parameter | Value |
|---|---|
| Brand | SKF |
| Bore diameter d | 25 mm |
| Outer diameter D | 42 mm |
| Width B | 18 mm |
| Material | GCr15 |
| Seal / shield | 2RS |
| Internal clearance | CN |
| Tolerance class | P0 |
| Cage | none |
| Basic dynamic load rating C | 21.6 kN |
| Basic static load rating C0 | 27.5 kN |
| Fatigue load limit Pu | 3.25 kN |
| Limiting speed (mechanical) | 6300 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 90 g |
| Manufacturer designation | NA 4905.2RS |
| Standard | ISO 1206 |
| Catalog version | SKF PUB BU/P1 17000/1 EN (Oct 2018), ch. 7.4 machined rings with flanges, with an inner ring |
| Last verified | 2026-09-26 |
Source: catalog reference (SKF PUB BU/P1 17000/1 EN (Oct 2018), ch. 7.4 machined rings with flanges, with 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. 7.4 machined rings with flanges, with 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 & NA-49-series range
| Bore d | 0.984 in |
|---|---|
| Outer diameter D | 1.654 in |
| Width B | 0.709 in |
| ISO bore code | 05 |
| Radial section height (D−d)/2 | 8.5 mm |
| Smallest bore in NA-49-series | 10 mm |
| Largest outer diameter in NA-49-series | 190 mm |
| Width range across NA-49-series | 13–50 mm |
| Bore position in NA-49-series (smallest first) | 7 of 28 |
| Bore above smallest NA-49-series size | 15 mm |
Cross references & equivalents
No verified interchange data yet. Send an inquiry and our team will confirm equivalents manually.
How the NA4905-2RS model number is decoded
The dimension series 49 needle roller bearings with inner ring execution NA 4905.2RS measures 25×42×18 mm: needle rollers caged between a flanged outer ring and a ground inner ring, used wherever the journal cannot serve as a raceway. The designation NA 4905.2RS tells you the envelope — 25×42×18 mm — and the family tells you the construction: complete bearing, replaceable inner ring, flanged outer ring retaining the needle rollers. Execution notes: the inner ring is ground on bore and raceway, so the shaft seat is a normal k5/j6; the flanged outer ring needs no housing shoulder, and NA 49 2RS executions add seals with a wider outer ring. For life calculation, the 21.6/27.5 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: heat or press the inner ring onto the 25 mm k5 seat (max 120 °C), fit the flanged outer ring into the H7 housing bore, and check the 18 mm assembly for free rotation before applying load.
Typical equipment & failure modes
Common applications
- agricultural implement pivots and cutter heads
- electric motor armature shafts with ground seats
- printing and paper-handling rollers
- gearbox shafts where the journal cannot be hardened on site
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
- corrosion pitting from condensation in intermittently operated machinery
- inner-ring raceway spalling after the narrow ring section runs hot with excessive interference
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 42 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 21.6/27.5 kN ratings are SKF catalogue values for this exact execution (NA 4905.2RS); ratings can be revised without the order number changing, so keep the catalogue version (SKF catalogue PUB BU/P1 17000) with the drawing.
- The 21.6/27.5 kN ratings and 90 g mass are SKF catalogue values transcribed from ch. 7.4 of PUB BU/P1 17000 (PDF table page 640); 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 NA 4905.2RS?
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 8.5 mm radial section leaves no reserve once a raceway is dented or ribboned.
What are the dimensions and ratings of the NA 4905.2RS?
A NA 4905.2RS measures 25 mm bore/Fw × 42 mm outside diameter × 18 mm width (0.984 × 1.654 × 0.709 in). From SKF catalogue PUB BU/P1 17000: radial dynamic rating C 21.6 kN, static C0 27.5 kN, fatigue limit Pu 3.25 kN, limiting speed 6,300 r/min, mass about 90 g.
How is the NA 4905.2RS designation read?
The letters mark a machined-ring needle roller bearing with inner ring: 25 mm bore, 18 mm width, 42 mm OD per the series plan. The hardened inner ring is the raceway, so an ordinary k5 shaft seat suffices.
Can the NA 4905.2RS run on an unhardened shaft?
Yes — that is the point of this family. The NA 4905.2RS carries its own hardened, ground inner ring on a 25 mm seat, so the shaft needs only a normal k5/j6 finish. The inner ring is separable and replaceable.
Reviewed & verified by the MPN Base engineering desk against source catalog SKF PUB BU/P1 17000/1 EN (Oct 2018), ch. 7.4 machined rings with flanges, with an inner ring on 2026-09-26. Read our editorial & correction policy.