NA4908-2RS bearing: complete specifications & equivalents
The NA4908-2RS is a ISO 1206 radial bearing sized 40 x 62 x 23 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 | 40 mm |
| Outer diameter D | 62 mm |
| Width B | 23 mm |
| Material | GCr15 |
| Seal / shield | 2RS |
| Internal clearance | CN |
| Tolerance class | P0 |
| Cage | none |
| Basic dynamic load rating C | 36.9 kN |
| Basic static load rating C0 | 58.5 kN |
| Fatigue load limit Pu | 7.1 kN |
| Limiting speed (mechanical) | 4000 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 250 g |
| Manufacturer designation | NA 4908.2RS |
| 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 | 1.575 in |
|---|---|
| Outer diameter D | 2.441 in |
| Width B | 0.906 in |
| ISO bore code | 08 |
| Radial section height (D−d)/2 | 11 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) | 12 of 28 |
| Bore above smallest NA-49-series size | 30 mm |
Cross references & equivalents
No verified interchange data yet. Send an inquiry and our team will confirm equivalents manually.
How the NA4908-2RS model number is decoded
The dimension series 49 needle roller bearings with inner ring execution NA 4908.2RS measures 40×62×23 mm: needle rollers caged between a flanged outer ring and a ground inner ring, used wherever the journal cannot serve as a raceway. The NA 4908.2RS code gives bore 40 mm and width 23 mm explicitly; unlike the RNA/NK families the shaft only needs a standard k5/j5 seat because the hardened inner ring is the raceway. Inner rings are separable: order replacement inner rings separately by d×D×B, since the outer ring and roller assembly survive journals that ruin an inner raceway. Speed planning separates the two ceilings: no reference speed listed for this sealed/slow execution and 4,000 r/min mechanical limiting — needle bearings tolerate high rpm only with adequate lubricant film at the 40 mm seat. For NA 49 2RS executions the wider outer ring changes the housing depth: verify the 23 mm width and s offset dimensions against the open execution before reusing an existing bore.
Typical equipment & failure modes
Common applications
- wheel and lever pivots needing a replaceable inner ring
- conveyor roller ends and return rollers
- agricultural implement pivots and cutter heads
- electric motor armature shafts with ground seats
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
- inner-ring raceway spalling after the narrow ring section runs hot with excessive interference
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 36.9/58.5 kN ratings and 250 g mass are SKF catalogue values transcribed from ch. 7.4 of PUB BU/P1 17000 (PDF table page 642); combined-type axial ratings appear in the text above because the structured record carries radial values only.
Frequently asked questions
How is the NA 4908.2RS designation read?
The letters mark a machined-ring needle roller bearing with inner ring: 40 mm bore, 23 mm width, 62 mm OD per the series plan. The hardened inner ring is the raceway, so an ordinary k5 shaft seat suffices.
Can the NA 4908.2RS run on an unhardened shaft?
Yes — that is the point of this family. The NA 4908.2RS carries its own hardened, ground inner ring on a 40 mm seat, so the shaft needs only a normal k5/j6 finish. The inner ring is separable and replaceable.
How should the NA 4908.2RS be mounted?
Mount the inner ring on the 40 mm seat first (induction heat, max 120 °C, or press), then fit the flanged outer ring into the H7 housing bore. Verify free rotation and, for 2RS executions, check the wider outer ring against the housing depth.
What limits the service life of a NA 4908.2RS?
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 11.0 mm radial section leaves no reserve once a raceway is dented or ribboned.
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.