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A Complete Analysis of Needle Roller Bearing Models

Needle roller bearings are widely used in mechanical design and equipment maintenance due to their high load capacity and compact design. However, many technicians and sales engineers remain confused by the myriad model names, including NATR, NAKD, and KR. This article, based on the national standard GB/T 272, "Rolling Bearing Designation Method," provides an in-depth analysis of the needle roller bearing designation logic, helping practitioners quickly master selection techniques.

 

1. Decoding the Core Designation: The Meaning of Prefixes and Basic Models

 

Needle roller bearing models are not randomly assigned; they follow strict coding rules. The core designation typically consists of a "basic designation" followed by a suffix, with the basic designation revealing the bearing type and structural features.

 

NA series: represents needle roller bearings without an inner ring. These bearings utilize the shaft journal as the inner ring raceway, saving space and are suitable for applications with hardened shaft surfaces.

 

NK series: needle roller bearings with an inner ring offer a more stable structure and are suitable for higher speeds or when the shaft material is unsuitable for direct raceway operation.

 

KR series: Designates specifically roller needle roller bearings with bolted shafts. They are commonly used in conveying equipment and guide rail systems, offering easy installation and high load capacity.

 

NATR / NATV: These are needle roller bearings with a flanged outer ring and no inner ring. TR designates a flanged outer ring and thrust-locating design, while V stands for a full complement of needle rollers (no cage). They are suitable for low speeds and heavy loads.

 

Tip: Distinguishing whether a bearing has an inner ring is the first step in selecting a bearing. Types without an inner ring offer lower costs and smaller radial dimensions, but require higher shaft hardness and surface quality.

 

II. Suffix Code: Seal, Cage, and Outer Ring Type

 

The suffix letter further details the bearing's functional characteristics and directly impacts the operating environment and lifespan.

 

Suffix Meaning Application

 

-2RS Double-sided rubber seals: Dust and water resistant, suitable for humid or dusty environments.

 

-Z Single-sided steel plate dust cover: Protects against large particles and offers superior high-speed performance compared to sealed models.

 

X Cylindrical outer ring (non-cam-shaped): Suitable for applications requiring high positioning accuracy.

 

TV Polyamide cage: Reduces weight and increases maximum speed.

 

For example, NA4904-2RS indicates a 20mm inner diameter needle roller bearing without an inner ring, equipped with double-sided rubber seals. Suitable for small motors or gearboxes.

 

3. How to Quickly Match Models? Three-Step Selection Method

 

Determine structural requirements: Is a flange required for locating? Is the shaft allowed to serve as a raceway?

 

Check the dimensional table: Select a basic model based on the installation space (inner diameter, outer diameter, and width).

 

Add suffixes based on operating conditions: Consider factors such as sealing, lubrication, and speed to select the appropriate variant.

 

It is recommended to compare the cross-sectional structure diagram in the product manual with the dimensional parameter table to intuitively understand the internal structure and installation method.

 

Mastering the designation system for needle roller bearings not only demonstrates technical proficiency but is also crucial for enhancing service expertise. Understanding the engineering logic behind designations like NA, KR, and -2RS can significantly improve selection, procurement, and troubleshooting.