RNA4908-2RS bearing: complete specifications & equivalents
The RNA4908-2RS is a ISO 1206 radial bearing sized 48 x 62 x 22 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 | 48 mm |
| Outer diameter D | 62 mm |
| Width B | 22 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 | 150 g |
| Manufacturer designation | RNA 4908.2RS |
| Standard | ISO 1206 |
| Catalog version | SKF PUB BU/P1 17000/1 EN (Oct 2018), ch. 7.3 machined rings with flanges, without an inner ring |
| Last verified | 2026-09-26 |
Source: catalog reference (SKF PUB BU/P1 17000/1 EN (Oct 2018), ch. 7.3 machined rings with flanges, 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. 7.3 machined rings with flanges, 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 & RNA-49-series range
| Bore d | 1.89 in |
|---|---|
| Outer diameter D | 2.441 in |
| Width B | 0.866 in |
| ISO bore code | 08 |
| Radial section height (D−d)/2 | 7 mm |
| Smallest bore in RNA-49-series | 14 mm |
| Largest outer diameter in RNA-49-series | 190 mm |
| Width range across RNA-49-series | 13–50 mm |
| Bore position in RNA-49-series (smallest first) | 12 of 28 |
| Bore above smallest RNA-49-series size | 34 mm |
Cross references & equivalents
| Equivalent model | Brand | Match level | Note |
|---|---|---|---|
| RNA4908 | SKF | partial Main dimensions match; tolerances, seals or internal clearance differ. | Same 48×62×22 mm envelope, but catalogue C/C0 differ between the executions (36.9/58.5 vs 42.9/71 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 RNA4908-2RS model number is decoded
SKF's dimension series 49 needle roller bearings without inner ring include RNA 4908.2RS: 48 mm Fw, 62 mm outside diameter, 22 mm width — a machined and ground outer ring whose rolled flanges retain the needle rollers, running on the shaft as the inner raceway. In SKF nomenclature RNA families drop the inner ring: the numbers after the letters give the 48 mm under-roller diameter and the 22 mm width, with the 62 mm outside diameter set by the dimension series 49 needle roller bearings without inner ring plan. The wide NKS/NKIS siblings share the Fw and OD but add width for higher ratings — check both when the radial space allows a wider seat. Catalogue mass 150 g at 48×62×22 mm makes this one of the highest capacity-per-gram choices in the dimension series 49 needle roller bearings without inner ring; the limit is usually the shaft's ability to serve as a raceway, not the rolling contact itself. Fit the outer ring with a press and a fitting sleeve, not by hammering the flanges — rolled flanges chip; the 62 mm ground OD takes the press fit that prevents outer-ring creep in oscillating duty.
Typical equipment & failure modes
Common applications
- cam followers built up from separate components
- crank pins and eccentrics where the hardened journal is the raceway
- gearbox planetary and idler gears on hardened pins
- piston-pin style pivots in hydraulic pumps
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
- abrasive paste formation from dust ingressing past open ends without effective housing seals
- false brinelling of standby equipment under external vibration
- smearing of rollers and journal during idle periods because the radial section holds too little lubricant
Selection pitfalls — read before you substitute
- At 48 mm bore, verify shaft deflection against the needle length: these rollers tolerate little edge loading, and a simply supported span between 48 mm seats can bend past the compensation range long before the load rating is exhausted.
- The quoted 36.9/58.5 kN ratings are SKF catalogue values for this exact execution (RNA 4908.2RS); ratings can be revised without the order number changing, so keep the catalogue version (SKF catalogue PUB BU/P1 17000) with the drawing.
- 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.
- The 36.9/58.5 kN ratings and 150 g mass are SKF catalogue values transcribed from ch. 7.3 of PUB BU/P1 17000 (PDF table page 632); combined-type axial ratings appear in the text above because the structured record carries radial values only.
Frequently asked questions
What does RNA 4908.2RS mean in SKF part numbering?
RNA names a machined-ring needle roller bearing without inner ring: the figures give Fw 48 mm and width 22 mm, OD 62 mm comes from the dimension series, and the flanged outer ring retains the caged rollers.
Does the RNA 4908.2RS need a hardened and ground shaft?
No. In this execution the 48 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 RNA 4908.2RS?
Press on the ring faces only with a fitting sleeve, keep everything square to the 48 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.
Is the RNA 4908.2RS 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.
Reviewed & verified by the MPN Base engineering desk against source catalog SKF PUB BU/P1 17000/1 EN (Oct 2018), ch. 7.3 machined rings with flanges, without an inner ring on 2026-09-26. Read our editorial & correction policy.