NSK rolling bearings generally consist of two rings, rolling elements, and a cage, and they are classified into radial bearings or thrust bearings depending on the direction of the main load. In addition, depending on the type of NSK rolling elements, they are classified into NSK ball bearings or NSK roller bearings, and they are further segregated by differences in their design or specific purpose.
The most common NSK bearing types and name of bearing parts are shown below. 
NSK rolling bearing types
NSK radial ball bearing types
NSK deep groove ball bearings
NSK single row deep groove ball bearings are the most common type of rolling bearings. Their use is very widespread. The raceway grooves on both the inner and outer rings have circular arcs of slightly larger radius than that of the balls. In addition to radial loads, axial loads can be imposed in either direction. Because of their low torque, they are highly suitable for applications where high speeds and low power loss are required.
NSK NSK magneto bearings
The inner groove of magneto bearings is a little shallower than that of deep groove bearings. Since the outer ring has a shoulder on only one side, the outer ring may be removed. This is ofter advantageous for mounting. In general, two such bearings are used in duplex pairs. Magneto bearings are small bearings with a bore diameter of 4 to 20 mm and are mainly used for small magnetos, gyroscopes, instruments, etc. Pressed brass cages are generally used.
NSK angular contact ball bearings
NSK single row anguar contact ball bearings: individual bearings of this type are capable of taking radial loads and also axial loads in one direction. Four contact angles of 15°, 25°, 30°, and 40° are available. The larger the contact angle, the higher the axial load capacity. For high speed operation, however, the smaller contact angles are preferred. Usually, two bearings are used in duplex pairs, and the clearance between them must be adjusted properly.
NSK duplex bearings: a combination of two radial bearings is called a duplex pair. Usually, they are formed using angular contact ball bearings or tapered roller bearings. Possible combinations include face-to-face, which have the outer ring faces together (type DF), back-to-back (type DB), or both front faces in the same directions (type DT). DF and DB type duplex bearings are capable of taking radial oads and axial loads in both direction. Type DT is used when there is a strong axial load in one direction and it is necessary to impose the load equally on each bearing.
NSK double row angular contact ball bearings are basically two single row angular contact ball bearings mounted back-to-back except that they have only one innering and one outer ring, each having raceways. They can take axial loads in both direction.
NSK four point contact bearings
Then inner and outer rings of NSK four point contact bearings are separable because the inner ring is split in a radial plane. They can take axial loads from either direction. The balls have a contact angle of 35° with each ring. Just one bearing of this type can replace a combination of face-to-face or back-to-back angular contact bearings.
NSK self-aligning ball bearings
The inner ring of this type of NSK bearing has two raceways and the outer ring has a single spherical raceway with its center of curvature coincident with the bearing axis. Therefore, the axis of the inner ring, balls, and cage can deflect to some extent around the bearing center. Consequently, minor angular misalignment of the shaft and housing caused by machining or mounting error is automatically corrected.
NSK radial roller bearing types
NSK cylindrical roller bearings
In bearings of this type, the cylindrical rollers are in linear contact with the raceways. They have a high radial load capacity and are suitable for high speeds. There are different types designated NU, NJ, NUP, N, NF for single row bearings, and NNU, NN for double row bearings depending on the design or absence of side ribs. The outer and inner rings of all types are separable.
NSK needle roller bearings
NSK needle roller bearings contain many slender roller with a length 3 to 10 times their diameter. As a result, the ratio of the bearing outside diameter to the inscribed circle diameter is small, and they have a rather high radial load capacity. There are numerous types available, and many have no inner rings. The drawn-cup type has a pressed steel outer ring and the solid type has a machined outer ring. There are also cage and roller assemblies without rings. Most bearings have pressed steel cages, but some are without cages.
NSK tapered roller bearings
Bearings of this type use conical rollers guided by a back-face rib on the cone. There NSK bearings are capable of taking high radial loads and also axial loads in one direction. In the HR series, the rollers are increased in both size and number giving it an even higher load capacity. They are generally mounted in pairs in a manner similar to single-row angular contact ball bearings. In this case, the proper internal clearance can be obtained by adjusting the axial distance between the cones or cups of th etwo opposed bearings. Since they are separable, the cone assemblies and cups can be mounted independently.
NSK spherical roller bearings
These NSK bearing types have barrel-shaped rollers between the inner ring, which has two raceways, and the outer ring which has one spherical raceway. Since the center of curvature of the outer ring raceway surface coincides with the bearing axis, they are self-aligning in a manner similar to that of self-aligning ball bearings. Therefore, if there is deflection of the shaft or housing or misalignment of their axes, it is automatically corrected so excessive force is not applied to the bearings. NSK spherical roller bearings can take, not only heavy radial loads, but also some axial loads in either direction. They have excellent radial load-carrying capacity and are suitable for use where there are heavy or impact loads.
NSK thrust ball bearing types
NSK single-direction thrust ball bearings
NSK single-direction thrust ball bearings are composed of washer-like bearing rings with raceway grooves. The ring attached to the shaft is called the shaft washer (or inner ring) while that attached to the housing is called the housing washer (or outer ring).
NSK double-direction thrust ball bearings
In double-direction thrust ball bearings, there are three rings with the middle one (center ring) being fixed to the shaft.
NSK thrust roller bearing types
NSK spherical thrust roller bearings
These NSK bearings have a spherical raceway in the housing washer and barrel-shaped rollers obliquely arranged around it. Since the raceways in the housing washer in spherical, these NSK bearings are self-aligning. They have a very high axial load capacity and are capable of taking moderate radial loads when an axial load is applied.
Contact angle and NSK bearing types
The contact angle (α) refers to the angle between a vertical plane of the rotation axis of NSK bearing and a straight line between the points where the rolling element comes in contact with the inner ring raceway and outer ring raceway.
Radial bearings and thrust bearings are classified depending on the size of the contact angle.
- Radial bearin α: less than 45°
- Thrust bearing α: over 45°
The picture below shows the relation between contact angle and loading direction on the bearing.