Product Overview

The NMT RNU 204 ECP is an inner ringless single-row cylindrical roller bearing with RNU design – essentially an NU type cylindrical roller bearing without an inner ring, consisting of an outer ring (with two integral flanges) and a roller and cage assembly. With a roller bore (Fw) of 26.5 mm, an outer diameter of 47 mm, and a width of 14 mm, 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) . Specifically designed for high radial loads in combination with high speeds, the inner ringless design allows direct mounting on hardened and ground shaft raceways.

 

The bearing offers a basic dynamic load rating of 28.5 kN, a static load rating of 22 kN, and a fatigue load limit of 2.75 kN. It achieves a reference speed of 17,000 r/min and a limiting speed of 24,000 r/min. The bearing weighs only 0.054 kg (54 g) with an operating temperature range of -30°C to 120°C.

 

Model Code Decoding – Understanding NMT RNU 204 ECP

Code Meaning

RNU Design code – inner ringless cylindrical roller bearing, essentially an NU bearing without an inner ring

20 Size series designation

4 Bore size code – 26.5 mm roller bore, 47 mm OD, 14 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 RNU design (inner ringless) is the most prominent structural feature of this bearing – it is essentially an NU type cylindrical roller bearing without an inner ring. The inner ringless design allows direct mounting on hardened and ground shaft raceways, offering multiple advantages: larger shaft diameters for stronger, more rigid shafts; more compact bearing arrangements. The ECP cage, made of glass fibre reinforced PA66, combines high strength with lightweight characteristics, providing excellent roller guidance accuracy at high speeds. The CN radial clearance (normal group) is suitable for most general applications. The outer ring with two integral flanges allows axial displacement in both directions, limited only by the width of the raceway on the shaft. The synergy of high radial load capacity, high speed performance, and inner ringless compact design makes this bearing the ideal precision bearing solution for high-radial-load high-speed rotating equipment.

 

Core Performance Advantages

1. Inner Ringless Design (RNU) – Compact Space, Stronger Shaft

An RNU bearing is essentially an NU bearing without an inner ring, with the roller assembly running directly on hardened and ground shaft raceways. This design offers:

 

Larger shaft diameter: Without the inner ring occupying space, a larger diameter shaft can be used, providing a stronger, more rigid shaft suitable for high-speed applications

 

More compact bearing arrangement: Bearing arrangement design can be further miniaturised

 

Bidirectional axial displacement: The outer ring double-flange design allows axial displacement in both directions, limited only by the width of the raceway on the shaft

 

2. 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 28.5 kN, static load rating of 22 kN, and fatigue load limit of 2.75 kN, this bearing offers radial load capacity far exceeding ball bearings of the same size. Combined with the ECP cage, it delivers stable performance under high speeds, rapid accelerations, and peak loads.

 

3. High Speed Performance – 17,000 – 24,000 r/min

The low-friction characteristics of the ECP glass fibre reinforced PA66 cage, combined with optimised internal geometry, deliver a reference speed of 17,000 r/min and a limiting speed of 24,000 r/min.

 

4. Optimised Roller Profile – Extended Service Life

Logarithmically crowned rollers effectively optimise contact stress distribution between rollers and raceways, reducing edge stress concentration and extending bearing service life.

 

5. 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, providing superior guidance accuracy at high speeds while reducing centrifugal forces, friction, and heat generation.

 

6. 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.

 

7. 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.

 

8. Clear Performance Specifications

 

Parameter Value

Roller Bore Fw 26.5 mm

Outer Diameter D 47 mm

Width C 14 mm

Dynamic Load Rating C 28.5 kN

Static Load Rating C₀ 22 kN

Fatigue Load Limit Pu 2.75 kN

Reference Speed 17,000 r/min

Limiting Speed 24,000 r/min

Design Code RNU (inner ringless cylindrical roller bearing)

Cage Material Glass Fibre Reinforced PA66 (ECP)

Radial Clearance CN (Normal)

Number of Rows 1

Seal Type Open

Tolerance Class Normal (PN/P0)

Weight 0.054 kg (54 g)

Temperature Range -30°C to 120°C

Typical Applications

The NMT RNU 204 ECP, with its inner ringless design, high radial load capacity, and high speed performance, covers an exceptionally wide range of high-end applications:

 

Gearboxes – industrial gearboxes, reducers

 

Electric Motors – general industrial motors, servo motors

 

Pumps and Compressors – high-speed rotating machinery

 

Agricultural Machinery – various agricultural equipment

 

Traction Motors – high radial load and high speed combinations

 

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

 

Rotating Shaft Systems Requiring Larger Shaft Diameters or More Compact Designs – leveraging the advantages of the inner ringless design

 

Important Installation Notes

⚠️ This bearing features an inner ringless design (RNU) – ensure the shaft raceway is hardened and ground. The surface hardness, roughness, and precision of the shaft raceway directly affect bearing performance and service life.

 

✅ This bearing accommodates axial displacement in both directions, limited only by the width of the raceway on the shaft.

 

✅ Ensure shaft raceway dimensions and tolerances match the bearing roller bore (26.5 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.

 

⚠️ 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 RNU 204 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 RNU inner ringless design, ECP glass fibre reinforced PA66 cage, CN radial clearance, 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 compact design, high radial load, and high speed performance.

 

Choose NMT RNU 204 ECP for:

 

✅ RNU inner ringless design – larger shaft diameter, more compact configuration

 

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

 

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

 

✅ 24,000 r/min high speed performance – industry-leading

 

✅ Bidirectional axial displacement accommodation – ideal for floating applications

 

✅ 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