NA4903-2RS bearing: complete specifications & equivalents
The NA4903-2RS is a ISO 1206 radial bearing sized 17 x 30 x 14 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 | 17 mm |
| Outer diameter D | 30 mm |
| Width B | 14 mm |
| Material | GCr15 |
| Seal / shield | 2RS |
| Internal clearance | CN |
| Tolerance class | P0 |
| Cage | none |
| Basic dynamic load rating C | 9.52 kN |
| Basic static load rating C0 | 12.9 kN |
| Fatigue load limit Pu | 1.53 kN |
| Limiting speed (mechanical) | 9000 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 40 g |
| Manufacturer designation | NA 4903.2RS |
| 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 | 0.669 in |
|---|---|
| Outer diameter D | 1.181 in |
| Width B | 0.551 in |
| ISO bore code | 03 |
| Radial section height (D−d)/2 | 6.5 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) | 4 of 28 |
| Bore above smallest NA-49-series size | 7 mm |
Cross references & equivalents
No verified interchange data yet. Send an inquiry and our team will confirm equivalents manually.
How the NA4903-2RS model number is decoded
For a 17 mm shaft that cannot be hardened on site, NA 4903.2RS adds a hardened, ground inner ring to the machined needle roller design: envelope 17×30×14 mm per the dimension series 49 needle roller bearings with inner ring plan. Reading the designation: the letters name the series with inner ring, the numbers the boundary plan — 17 mm bore (d), 14 mm width; the 30 mm OD follows the dimension series, and the inner ring is a separate ground component. 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. The 40 g catalogue mass and 6.5 mm radial section ((30−17)/2) frame a rating of about 0.56 kN dynamic per millimetre of bore — the needle construction's density advantage over ball bearings of the same envelope. Because the inner ring is separable, mount it first against its shoulder, then slide the outer ring and roller set over it — the order avoids forcing rollers across the shaft threads or burrs.
Typical equipment & failure modes
Common applications
- conveyor roller ends and return rollers
- agricultural implement pivots and cutter heads
- electric motor armature shafts with ground seats
- printing and paper-handling rollers
Known failure patterns
- needle edge loading and raceway denting when the shaft deflects beyond the compensation range
- 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
- brinelling of raceways from impact or pressing force transmitted through the rolling elements
- inner-ring raceway spalling after the narrow ring section runs hot with excessive interference
Selection pitfalls — read before you substitute
- On a 17 mm seat the housing bore quality dominates life: a bore 0.02 mm out of round pinches the 30 mm ring or cup into a lobed shape, and the rollers then trace the housing's geometry error, not the design load.
- 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.
- Do not interchange envelope-identical needle families blindly: NA 4903.2RS shares its 17×30×14 mm outline with inner-ring and sealed siblings whose ratings differ — the family letters are part of the specification, not decoration.
- The 9.52/12.9 kN ratings and 40 g mass are SKF catalogue values transcribed from ch. 7.4 of PUB BU/P1 17000 (PDF table page 638); combined-type axial ratings appear in the text above because the structured record carries radial values only.
Frequently asked questions
Does the NA 4903.2RS need a hardened and ground shaft?
Yes — that is the point of this family. The NA 4903.2RS carries its own hardened, ground inner ring on a 17 mm seat, so the shaft needs only a normal k5/j6 finish. The inner ring is separable and replaceable.
What mounting mistakes ruin a NA 4903.2RS?
Mount the inner ring on the 17 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.
Is the NA 4903.2RS sealed?
Yes — the 2RS execution seals both faces with rubber contact seals; note its wider outer ring (B and s differ from the open execution), so housing dimensions must be re-checked.
Which dimensions does the NA 4903.2RS have?
A NA 4903.2RS measures 17 mm bore/Fw × 30 mm outside diameter × 14 mm width (0.669 × 1.181 × 0.551 in). From SKF catalogue PUB BU/P1 17000: radial dynamic rating C 9.52 kN, static C0 12.9 kN, fatigue limit Pu 1.53 kN, limiting speed 9,000 r/min, mass about 40 g.
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.