NA4909 bearing: complete specifications & equivalents
The NA4909 is a ISO 1206 radial bearing sized 45 x 68 x 22 mm (bore x OD x width). Verify dimensions against the official catalog before ordering.
Specification table
| Parameter | Value |
|---|---|
| Brand | SKF |
| Bore diameter d | 45 mm |
| Outer diameter D | 68 mm |
| Width B | 22 mm |
| Material | GCr15 |
| Seal / shield | open |
| Internal clearance | CN |
| Tolerance class | P0 |
| Cage | none |
| Basic dynamic load rating C | 45.7 kN |
| Basic static load rating C0 | 78 kN |
| Fatigue load limit Pu | 9.65 kN |
| Reference speed (thermal) | 7500 rpm |
| Limiting speed (mechanical) | 8500 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 270 g |
| Manufacturer designation | NA 4909 |
| 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 | 1.772 in |
|---|---|
| Outer diameter D | 2.677 in |
| Width B | 0.866 in |
| ISO bore code | 09 |
| Radial section height (D−d)/2 | 11.5 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) | 13 of 28 |
| Bore above smallest NA-49-series size | 35 mm |
Cross references & equivalents
No verified interchange data yet. Send an inquiry and our team will confirm equivalents manually.
How the NA4909 model number is decoded
In SKF catalogue PUB BU/P1 17000, NA 4909 denotes a complete needle roller bearing for a 45 mm shaft — machined inner and outer rings, integral flanges on the outer ring retaining the roller set, 68 mm OD and 22 mm width. The NA 4909 code gives bore 45 mm and width 22 mm explicitly; unlike the RNA/NK families the shaft only needs a standard k5/j5 seat because the hardened inner ring is the raceway. TN polymer cage executions run quieter and tolerate grease-lubricated pivot duty; steel cage executions remain the choice for higher temperature or oil-bath lubrication. Catalogue mass 270 g at 45×68×22 mm makes this one of the highest capacity-per-gram choices in the dimension series 49 needle roller bearings with inner ring; the limit is usually the shaft's ability to serve as a raceway, not the rolling contact itself. 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
- printing and paper-handling rollers
- gearbox shafts where the journal cannot be hardened on site
- wheel and lever pivots needing a replaceable inner ring
- conveyor roller ends and return rollers
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
- brinelling of raceways from impact or pressing force transmitted through the rolling elements
- inner-ring bore fretting on a loose shaft seat, migrating hard particles into the rolling contact
Selection pitfalls — read before you substitute
- At 45 mm bore, verify shaft deflection against the needle length: these rollers tolerate little edge loading, and a simply supported span between 45 mm seats can bend past the compensation range long before the load rating is exhausted.
- Hardness is load capacity: in families without an inner ring the 45 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 45.7/78 kN ratings are SKF catalogue values for this exact execution (NA 4909); ratings can be revised without the order number changing, so keep the catalogue version (SKF catalogue PUB BU/P1 17000) with the drawing.
- The 45.7/78 kN ratings and 270 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
Can the NA 4909 run on an unhardened shaft?
Yes — that is the point of this family. The NA 4909 carries its own hardened, ground inner ring on a 45 mm seat, so the shaft needs only a normal k5/j6 finish. The inner ring is separable and replaceable.
How should the NA 4909 be mounted?
Mount the inner ring on the 45 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 4909?
Beyond the L10 rating, the practical limits are journal/raceway hardness for the 45 mm seat, lubricant condition at the roller ends, and contamination through open ends — the 11.5 mm radial section leaves no reserve once a raceway is dented or ribboned.
What are the dimensions and ratings of the NA 4909?
A NA 4909 measures 45 mm bore/Fw × 68 mm outside diameter × 22 mm width (1.772 × 2.677 × 0.866 in). From SKF catalogue PUB BU/P1 17000: radial dynamic rating C 45.7 kN, static C0 78 kN, fatigue limit Pu 9.65 kN, limiting speed 8,500 r/min, reference speed 7,500 r/min, mass about 270 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.