1 Model Information & Technical Parameters

Model：NJ 304 ECP

Dimensions

Bore d：20 mm

Outer diameter D：52 mm

Width B：15 mm

Inner ring shoulder d₁：≈31.2 mm

Outer ring raceway diameter E：45.5 mm

Min chamfer r₁,₂：1.1 mm；r₃,₄：0.6 mm

Performance Data

Basic dynamic load rating Cr：35.5 kN

Basic static load rating C0r：26 kN

Fatigue load limit Pu：3.25 kN

Reference speed：15000 r/min

Limiting speed：18000 r/min

Technical Attributes

Supply form: Complete bearing unit

Number of roller rows: Single row

Structure type: NJ design (double flanged outer ring, single flanged inner ring)

Axial characteristic: Supports unidirectional axial load for one-way shaft location; limited axial float in reverse direction

Bore type: Cylindrical bore

Cage: P glass fiber reinforced PA66, roller centered window cage

Inner ring flanges: 1; Outer ring flanges: 2

Coating: None

Seal: Open type, no seal

Pre-grease: None

Logistics & Industry Codes

Net weight：0.15 kg

Indicative carbon footprint：0.24 kg CO₂e

eClass code：23-05-09-01

UNSPSC code：31171505

Suffix Explanation

NJ: NJ-type cylindrical roller bearing, outer ring with two integral flanges, inner ring with one flange. Able to sustain unidirectional axial force and serve as one-way locating support for shaft system; bidirectional locating can be realized by matching HJ thrust collar.

EC: Optimized internal geometry, crowned roller profile equalizes contact stress, suppresses edge pitting between roller ends and ribs, improves load capacity and fatigue life.

P: Glass fiber reinforced PA66 polyamide window cage, roller-guided, lower operating temperature for continuous medium-high speed operation.

Important reminder: NJ bearing can only withstand axial load from one single direction, bidirectional restriction is not available. Standard shaft layout: install NJ304ECP at one end as fixed bearing to limit one-way shaft movement, adopt N/NU/RNU floating bearing on the opposite side to absorb thermal elongation and prevent seizure caused by temperature rise. Select NUP304 or NJ304 fitted with HJ collar if bidirectional axial positioning is required. Continuous operating temperature range for PA66 cage: -40～+120℃. Open design requires housing sealing against dust and moisture. Avoid highly polar aggressive synthetic lubricants. Press force must apply only on ring end faces; never strike roller assembly directly.

2 Structure & Operating Characteristics

Japan NMT NJ 304 ECP high-performance NJ single row cylindrical roller bearing adopts separable construction, inner ring, outer ring and roller cage assembly can be disassembled separately, suitable for various interference fitting conditions. EC crowned roller profile optimizes load distribution, greatly reducing contact stress between ribs and roller ends and improving shock resistance and long-term operational stability. Matched glass fiber reinforced PA66 roller-centered cage features low centrifugal force and vibration, generating less heat compared with pressed steel cage.

Selection reference: N/NU/RNU are pure floating bearings unable to bear axial loads; NJ type supports unidirectional axial force as basic locating bearing; NUP type comes with loose rib to realize native bidirectional positioning.

3 Core Performance Advantages

1. NJ locating construction bears heavy radial load and unidirectional axial load simultaneously to achieve one-way axial limitation of shaft.

2. EC crowned roller geometry eliminates edge load concentration, restrains fatigue spalling and extends bearing service life.

3. Glass fiber reinforced PA66 cage is lightweight with excellent toughness, delivering low vibration and temperature rise under medium-high speed operation.

4. Outstanding radial load capacity and structural rigidity, capable of stably sustaining continuous heavy load and moderate shock load.

5. Separable inner and outer rings allow flexible assembly, convenient for independent interference fitting on shaft and housing bore.

6. Coating-free open design compatible with mineral greases, circulating mineral oils and most synthetic lubricants.

4 Typical Application Fields

4.1 Gear Transmission Equipment

Standard gear reducers, industrial gearbox fixed support

4.2 Fluid Power Equipment

Centrifugal fans, blowers, screw air compressor fixed end support

4.3 Light Conveying Machinery

Conveyor rollers, chain drive units, packaging machinery transmission shaft locating end

4.4 General Power Machinery

Medium-small variable frequency motors, small machine tool transmission shaft one-way locating support

5 Assembly Specifications & Usage Guidelines

5.1 Assembly Environment & Operation Standards

Maintain clean assembly area free of metal debris. Apply pressing force only on inner or outer ring end faces; direct impact on rollers and cage is prohibited. Rotate bearing manually after assembly to verify smooth rotation without sticking or abnormal noise. Confirm the direction of axial load matches bearing limiting direction during installation to avoid reverse axial impact.

5.2 Selection Guidance

One-way axial positioning & unidirectional axial load required → NJ 304 ECP

Pure radial support, thermal expansion compensation, no axial positioning needed → N304 / NU304 / RNU304 ECP

Bidirectional axial positioning & bidirectional axial load required → NUP304 ECP or NJ304 with HJ thrust collar

5.3 Lubrication Maintenance Instruction

No pre-filled lubricant upon delivery; fully apply grease during assembly. Circulating oil lubrication recommended for high-speed working conditions. Establish regular regreasing schedule based on load and rotating speed; dry friction operation is strictly forbidden.

5.4 Environmental Application Notes

No anti-rust coating. Apply anti-rust oil and seal tightly for long-term storage. Strengthen housing sealing under dusty and humid conditions. Switch to machined brass cage version if continuous operating temperature exceeds 120℃.

6 Fault Identification

Common failure modes: pitting & abrasion on roller ends and ribs, raceway fatigue spalling, cage wear & cracking, raceway scuffing due to insufficient lubrication. Full bearing replacement is mandatory once extensive rib abrasion, cracked cage or widespread roller pitting appears.