Product Overview

The NMT N 304 ECP is a single-row cylindrical roller bearing with N design – featuring two integral flanges on the inner ring and no flanges on the outer ring. With a 20 mm bore, 52 mm outer diameter, and 15 mm width, this bearing is manufactured from high-quality bearing steel, equipped with a glass fibre reinforced polyamide 66 (PA66) cage (ECP) , and features CN radial clearance (normal group) . It belongs to the SKF Explorer performance class, specifically designed for high radial loads in combination with high speeds, and features a separable design for easy mounting and maintenance. The bearing weighs 0.148 – 0.16 kg (148 – 160 g) .

 

Model Code Decoding – Understanding NMT N 304 ECP

Code Meaning

N Design code – inner ring with two integral flanges, outer ring without flanges, accommodates axial displacement in both directions

304 Size series designation – 20 mm bore, 52 mm OD, 15 mm width

EC Optimised internal design – accommodates more and/or larger rollers with improved roller end/flange contact for higher load capacity

P Glass fibre reinforced PA66 cage – roller-guided, injection moulded, lightweight, high strength, high speed capability

Core Value: The N design (inner ring with two flanges, outer ring without flanges) is the most prominent structural feature of this bearing – unlike the NU design (outer ring with two flanges, inner ring without flanges), the N design allows axial displacement in both directions, with displacement limited by the inner ring flanges. This makes it particularly suitable as a floating bearing, effectively accommodating shaft thermal expansion and axial displacement. The ECP glass fibre reinforced PA66 cage combines high strength with lightweight characteristics, providing excellent roller guidance accuracy at high speeds. The SKF Explorer performance class represents higher load capacity and extended service life. The separable design allows independent mounting of inner and outer rings, significantly simplifying assembly and maintenance. Logarithmically crowned rollers effectively optimise contact stress distribution between rollers and raceways. The synergy of high radial load capacity, bidirectional axial displacement, high speed performance, and separable design makes this bearing the ideal precision bearing solution for high-radial-load high-speed rotating equipment.

 

Core Performance Advantages

1. N Design – Bidirectional Axial Displacement Capability

The N design is the design specifically optimised for floating bearing arrangements among cylindrical roller bearings. The inner ring features two integral flanges, while the outer ring has no flanges, allowing axial displacement in both directions. This makes it particularly suitable as a floating bearing, effectively accommodating shaft thermal expansion and axial displacement. Compared to the NU design (outer ring with two flanges), the N design has its flanges on the inner ring, with displacement limited by the inner ring flanges.

 

2. SKF Explorer Performance Class – Higher Load Capacity, Longer Life

This bearing belongs to the SKF Explorer performance class, representing the highest level of SKF's bearing design, material, and manufacturing technology. Compared to standard class bearings, the Explorer class offers higher load capacity, longer service life, and superior operational reliability.

 

3. High Radial Load Capacity – High Load in Compact Space

The line contact design of cylindrical roller bearings provides extremely high radial load carrying capacity. With a basic dynamic load rating of 35.5 kN, static load rating of 26 kN, and fatigue load limit of 3.25 kN, this bearing offers radial load capacity far exceeding ball bearings of the same size.

 

4. High Speed Performance – 15,000 – 18,000 r/min

The optimised internal geometry and low-friction non-metallic cage design deliver a reference speed of 15,000 r/min and a limiting speed of 18,000 r/min. Precision-honed rolling contact surfaces further reduce friction and heat generation.

 

5. Separable Design – Easy Installation and Maintenance

The bearing features a separable design – inner ring and outer ring can be mounted independently, significantly simplifying assembly and maintenance. This allows bearing components to be interchanged, which is particularly important in applications requiring frequent maintenance or component replacement.

 

6. Glass Fibre Reinforced PA66 Cage (ECP) – Speed and Durability Combined

The roller-guided glass fibre reinforced PA66 cage offers an excellent strength-to-weight ratio, low friction characteristics, and dimensional stability. The non-metallic cage significantly reduces rotational friction, improving efficiency and extending bearing life.

 

7. CN Radial Clearance – Ideal for General Applications

CN radial clearance is normal clearance, suitable for most general applications, ensuring stable temperature performance and running accuracy under normal operating conditions.

 

8. Wide Operating Temperature Range

This bearing operates within a temperature range of -30°C to 120°C, capable of adapting to various demanding environments from cold to high-temperature processing.

 

9. Environmentally Compliant

The bearing has a carbon footprint of 0.55 kg CO₂e and is compliant with RoHS and REACH environmental standards.

 

10. Clear Performance Specifications

 

Parameter Value

Bore d 20 mm

Outer Diameter D 52 mm

Width B 15 mm

Outer Ring Shoulder Diameter D₁ ≈ 41.85 mm

Inner Ring Raceway Diameter F 27.5 mm

Chamfer r₁,₂ min. 1.1 mm

Chamfer r₃,₄ min. 0.6 mm

Permissible Axial Displacement s max. 0.9 mm

Shaft da min. 24.1 mm

Shaft da max. 26.2 mm

Shaft db min. 29 mm

Housing Da max. 45.4 mm

Max Fillet Radius ra max. 1 mm

Max Fillet Radius rb max. 0.6 mm

Dynamic Load Rating C 35.5 kN

Static Load Rating C₀ 26 kN

Fatigue Load Limit Pu 3.25 kN

Reference Speed 15,000 r/min

Limiting Speed 18,000 r/min

Minimum Load Factor kr 0.15

Limiting Value e 0.2

Calculation Factor Y 0.6

Design Code N (inner ring with two flanges, outer ring without flanges)

Cage Material Glass Fibre Reinforced PA66 (ECP)

Radial Clearance CN (Normal)

Number of Rows 1

Seal Type Open (Unsealed)

Bore Type Cylindrical

Tolerance Class Normal (PN/P0)

SKF Performance Class Explorer

Axial Displacement Capability In both directions

Weight 0.148 – 0.16 kg

Carbon Footprint 0.55 kg CO₂e

Temperature Range -30°C to 120°C

Typical Applications

The NMT N 304 ECP, with its N design bidirectional axial displacement capability, high radial load capacity, and high speed performance, covers an exceptionally wide range of high-end applications:

 

Traction Motors – railway and electric vehicle traction motors

 

Electric Motors – general industrial motors, servo motors

 

Gearboxes – industrial gearboxes, reducers

 

Floating Bearing Arrangements – accommodating shaft thermal expansion and bidirectional axial displacement

 

Pumps and Compressors – high-speed rotating machinery

 

Industrial Fans – high-speed, high-radial-load applications

 

Machine Tool Spindles – high-precision rotating equipment

 

Material Handling Equipment – conveyors, hoists

 

Important Installation Notes

✅ This bearing features N design (inner ring with two flanges, outer ring without flanges), allowing axial displacement in both directions, limited by the inner ring flanges (maximum 0.9 mm). Ensure correct floating bearing configuration during installation.

 

✅ This bearing features a separable design – inner ring and outer ring can be mounted independently, significantly simplifying assembly and maintenance.

 

✅ Ensure shaft and housing fits comply with normal precision class requirements (bore 20 mm, OD 52 mm). Shaft abutment diameter: da min. 24.1 mm, db min. 29 mm; housing abutment diameter: Da max. 45.4 mm; maximum chamfer radii: ra max. 1 mm, rb max. 0.6 mm.

 

✅ This bearing is unsealed (open design) – select appropriate lubrication method based on application – grease or oil lubrication.

 

✅ This bearing features CN (normal) radial clearance, suitable for most general applications.

 

✅ This bearing belongs to the SKF Explorer performance class, offering higher load capacity and extended service life.

 

⚠️ Cylindrical roller bearings primarily accommodate radial loads – axial load capacity is limited.

 

⚠️ This bearing has no lubrication groove and no lubrication holes – lubrication must be supplied through an external lubrication system.

 

⚠️ The ECP cage is made of glass fibre reinforced PA66 – avoid contact with sharp tools during installation to prevent cage damage.

 

NMT Quality Commitment

Japan NMT (Enmutī) has deep expertise in the precision bearing industry, with breakthroughs in material purification, process refinement, scenario customisation, and intelligent upgrading, transforming precision bearings into core solutions addressing pain points across multiple industries. The NMT N 304 ECP bearing is manufactured to strict Japanese quality standards – from ring material (high-purity bearing steel), rollers (logarithmically crowned), to superfinishing processes. The combination of N design (bidirectional axial displacement), ECP glass fibre reinforced PA66 cage, SKF Explorer performance class, high radial load capacity, and high speed performance makes this bearing the flagship precision bearing in the NMT cylindrical roller bearing series – offering the perfect balance of floating-end bidirectional axial displacement, high radial load, and high speed performance.

 

Choose NMT N 304 ECP for:

 

✅ N design – bidirectional axial displacement, ideal for floating applications

 

✅ ECP glass fibre reinforced PA66 cage – speed and durability combined

 

✅ 35.5 kN high radial load capacity – high load in compact space

 

✅ 18,000 r/min high speed performance – industry-leading

 

✅ Separable design – easy installation and maintenance

 

✅ SKF Explorer performance class – higher load capacity, longer life

 

✅ Logarithmically crowned rollers – extended service life

 

✅ CN radial clearance – ideal for general applications

 

✅ Wide temperature range – -30°C to 120°C

 

✅ Japanese precision manufacturing quality