NA4909LL/3AS NTN 45x68x23 Needle Roller Bearing

NA4909LL/3AS NTN is a machined-ring needle roller bearing with an inner ring and seals on both sides. Its overall dimensions are 45x68x23 mm, with bore diameter d = 45 mm, outside diameter D = 68 mm and inner ring/overall width B = 23 mm. The outer ring width C is 22 mm, while the diameter under the rollers F is 52 mm.

NA4909LL/3AS NTN - Product Characteristics

The exact NTN designation is NA4909LL/3AS. Unlike the previously described HK4520 drawn-cup bearing, this reference uses machined rings and incorporates an inner ring.

Its technical identity is:

NA4909LL/3AS -> NTN -> machined-ring needle roller bearing -> inner ring -> double seals -> 45x68x23 mm

The bearing uses a single row of needle rollers. The long, small-diameter rolling elements provide substantial radial load capacity within a relatively compact radial cross-section.

Dimensions

Official NTN technical data specify:

d - Bore Diameter: 45 mm
F - Diameter Under Rollers: 52 mm
D - Outside Diameter: 68 mm
B - Bearing / Inner Ring Width: 23 mm
C - Outer Ring Width: 22 mm
rs min - Minimum Chamfer: 0.6 mm
Commercial Dimensions: 45x68x23 mm

This distinction between B and C is important. Describing NA4909LL/3AS simply as 45x68x23 mm is correct for commercial identification, but the detailed specification should show that B = 23 mm and C = 22 mm.

Machined-Ring Needle Roller Construction

NA4909LL/3AS belongs to NTN's family of machined-ring needle roller bearings.

Unlike a thin drawn-cup HK-series bearing, this design has a machined outer ring and a separate inner ring. The inner ring provides the raceway for the needle rollers, so the bearing can be used where the shaft itself is not intended to serve directly as a precision raceway.

The bearing is single-row and primarily designed for radial load support.

Inner Ring

The NA configuration includes an inner ring.

This is a significant distinction from the corresponding RNA construction, which does not incorporate an inner ring. Therefore, NA and RNA variants should not be treated as identical products even when they belong to the same dimensional family.

For NA4909LL/3AS, the inner ring provides the 45 mm bore diameter, while the needle roller running diameter is F = 52 mm.

LL Double-Seal Configuration

The suffix LL identifies the double-sealed version of this NTN needle roller bearing.

NTN's official catalogue distinguishes:

L - single seal
LL - double seal

Accordingly, NA4909LL/3AS is sealed on both sides. This is an important part of the exact specification and should not be omitted when selecting a replacement.

Radial Load Carrying Capacity

Official NTN data for the exact NA4909LL/3AS specify:

Basic Dynamic Radial Load Rating Cr: 28.6 kN
Basic Static Radial Load Rating C0r: 57 kN

Needle roller geometry provides a relatively large rolling contact area for the available radial cross-section, which is why this bearing type is used where substantial radial load capacity must be combined with compact radial dimensions.

These catalog ratings should not be interpreted as the maximum permissible loads of a complete bearing arrangement. Actual bearing life depends on load, speed, lubrication, fits and other operating conditions.

Limiting Speed

For NA4909LL/3AS, NTN specifies a limiting speed of:

Grease Lubrication: 3,800 rpm.

Because this is a sealed bearing configuration, a separate oil-lubricated limiting speed is not provided in the official table for this exact LL variant.

This value should not be confused with the higher speed ratings of the open NA4909R variant, which is a different bearing configuration.

Lubrication Groove and Hole

The official NTN Europe technical sheet confirms that NA4909LL/3AS has a lubrication hole in the outer ring.

The specified lubrication-hole diameter is:

k = 3 mm.

This feature is relevant when designing the lubrication arrangement and when comparing the NTN bearing with alternative products.

Meaning of NA4909LL/3AS

The designation should be retained in full when identifying the bearing.

NA4909 identifies the machined-ring needle roller bearing series and size with an inner ring.

LL identifies the version with seals on both sides.

/3AS is part of NTN's exact product designation for this sealed configuration. I would retain it unchanged rather than assigning an expanded meaning that is not explicitly defined for this exact product in the technical tables reviewed.

NA4909LL/3AS vs NA4909R

These NTN references belong to the same basic dimensional family but are not the same bearing configuration.

The official NTN-SNR catalogue gives:

NA4909R: B = 22 mm, C = 22 mm, Cr = 46 kN, C0r = 73 kN
NA4909LL/3AS: B = 23 mm, C = 22 mm, Cr = 28.6 kN, C0r = 57 kN.

This illustrates why the complete suffix is essential. Removing LL/3AS and listing the product simply as NA4909 can lead to incorrect technical data and product matching.

Selection and Interchangeability

When selecting a replacement for NA4909LL/3AS NTN, verify the complete specification rather than only the 45x68 mm diameters.

Important parameters include the 45 mm bore, 68 mm outside diameter, B = 23 mm overall width, C = 22 mm outer ring width, F = 52 mm roller diameter, inner-ring construction, double sealing, load ratings and lubrication arrangement.

Products marketed as NA4909-2RS by other manufacturers may have a broadly corresponding bearing concept, but identical basic dimensions do not by themselves establish full technical interchangeability.

Technical Specification

Manufacturer: NTN
Designation: NA4909LL/3AS
Bearing Type: Machined-ring needle roller bearing
Number of Rows: 1
Inner Ring: Yes
Sealing: Both sides
Commercial Dimensions: 45x68x23 mm
d - Bore Diameter: 45 mm
F - Diameter Under Rollers: 52 mm
D - Outside Diameter: 68 mm
B - Bearing / Inner Ring Width: 23 mm
C - Outer Ring Width: 22 mm
Minimum Chamfer rs: 0.6 mm
Basic Dynamic Radial Load Rating Cr: 28.6 kN
Basic Static Radial Load Rating C0r: 57 kN
Limiting Speed, Grease: 3,800 rpm
Lubrication Hole: Yes
Lubrication Hole Diameter k: 3 mm
Approximate Mass: 0.29 kg

FAQ

What are the dimensions of NA4909LL/3AS NTN?

The commercial dimensions are 45x68x23 mm. More precisely, NTN specifies d = 45 mm, D = 68 mm, B = 23 mm and outer ring width C = 22 mm.

Why are both 22 mm and 23 mm listed for this bearing?

Because they describe different dimensions. B = 23 mm is the bearing/inner ring width, while C = 22 mm is the outer ring width.

What type of bearing is NTN NA4909LL/3AS?

It is a single-row machined-ring needle roller bearing with an inner ring and seals on both sides.

Does NA4909LL/3AS have an inner ring?

Yes. The NA configuration includes an inner ring, giving the bearing a conventional 45 mm bore diameter.

What does LL mean in NA4909LL/3AS?

NTN uses LL for the double-sealed version. The bearing is therefore sealed on both sides.

What are the load ratings of NA4909LL/3AS NTN?

The basic dynamic radial load rating Cr is 28.6 kN, while the basic static radial load rating C0r is 57 kN.

What is the limiting speed of NA4909LL/3AS?

NTN specifies a limiting speed of 3,800 rpm with grease lubrication for this sealed version.

Is NA4909LL/3AS the same as an open NA4909?

No. The sealed NA4909LL/3AS has different dimensions and load ratings from the open NA4909R configuration. The complete designation must be considered when selecting a replacement.

AI Overview

NA4909LL/3AS NTN is a sealed, single-row machined-ring needle roller bearing with an inner ring. Its commercial dimensions are 45x68x23 mm, with d = 45 mm, D = 68 mm, B = 23 mm and C = 22 mm. NTN specifies radial load ratings of Cr 28.6 kN and C0r 57 kN.

SHORT DESCRIPTION

NA4909LL/3AS NTN is a single-row machined-ring needle roller bearing with an inner ring and seals on both sides. Commercial dimensions are 45x68x23 mm: d = 45 mm, D = 68 mm and B = 23 mm; the outer ring width C is 22 mm and F = 52 mm. Dynamic radial load rating Cr: 28.6 kN; static C0r: 57 kN. NTN specifies a limiting speed of 3,800 rpm with grease lubrication. The outer ring incorporates a lubrication hole.