Double-Row Cylindrical Roller Bearings (NN Type and NNU Type)

Specifications

How to choose Rolling Bearings

Points to check when selecting, with the values for this product (Double-Row Cylindrical Roller Bearings (NN Type and NNU Type)).

1. 1. Bore and housing bore dimensions

   This product: Inner diameter d 670～710 mm

   Select the bore diameter d to match the shaft seat, the outside diameter D to match the housing bore, and the width B to suit the installation space. Main dimensions are standardized in ISO and JIS dimension series, so interchangeable products can be found by boundary dimension designation. For tapered roller bearings, also check the assembled width T; for thrust bearings, also check the height H.

2. 2. Dynamic load rating based on life calculation

   This product: Basic dynamic load rating Cr 5890～7370 kN

   The basic dynamic load rating Cr is the reference value for calculating rated life. Verify that the required life is met using the equivalent load during operation and the rotational speed. For ball bearings, life is proportional to the cube of the load ratio, so providing load margin greatly extends life.

3. 3. Margin for static and shock loads

   The basic static load rating C0r is the allowable standard for permanent deformation generated at the rolling elements and raceways under stationary or low-speed conditions. For applications with oscillating motion or shock loads, confirm that a static safety factor against the maximum load is secured using C0r.

4. 4. Operating speed and lubrication method

   The limiting speed differs by lubrication method, and separate values are given for grease lubrication and oil lubrication. Confirm that the normal operating speed does not exceed the limiting value, and in high-speed ranges also consider cage material and precision grade. The reference speed can also be consulted as a thermal guideline.

5. 5. Precision grade and internal clearance

   Precision grades (P0, P6, P5, etc.) indicate rotational accuracy and dimensional accuracy; for high-precision applications such as machine tool spindles, select higher grades. Internal clearance (C2, CN, C3, etc.) is selected to allow for changes caused by interference fit and temperature differences during operation.

6. 6. Materials and lubrication suited to the environment

   For corrosive, high-temperature, vacuum, or clean environments, select specifications such as rings and rolling elements made of stainless steel or ceramics, or solid lubricants and fluorine grease for vacuum use. Check the operating temperature range, low dust generation, and whether food-grade grease registration applies against the application conditions.

This guide was written by AI based on the listed products' documents and specification items.

About Rolling Bearings and all products

Description

Dimensions, basic load ratings, and mounting-related dimensions for NN type (cylindrical bore) and NNU type (with locking ring groove in outer ring, cylindrical or tapered bore).

FAQ

Q. What are the bore diameter and outside diameter ranges of NN and NNU double-row cylindrical roller bearings?

A. Bore diameter d is 670 to 710 mm, and outside diameter D is 920 to 950 mm.

Q. What are the width and basic dynamic load rating of NN and NNU double-row cylindrical roller bearings?

A. Width B is 243 to 330 mm, and basic dynamic load rating Cr is 5890 to 7370 kN.

Q. What types of NN and NNU double-row cylindrical roller bearings are available, and how do their bore shapes differ?

A. NN type has a cylindrical bore. NNU type has a locking ring groove in the outer ring and is available with a cylindrical bore or a tapered bore.

Q. What is the fatigue load limit Pu of NN and NNU double-row cylindrical roller bearings?

A. Fatigue load limit Pu is 16200 to 20800 kN.

Written by AI based on the content of the source documents.

Source documents

• Catalog JTEKT 大形転がり軸受カタログ（技術解説・軸受寸法表）
  Found on: https://koyo.jtekt.co.jp/support/catalog-download/