Needle Roller Bearing Types

Needle roller bearings are a type of roller bearings and are classified as either radial or thrust depending on the direction of the load they support. Needle roller bearings include bearings whose rollers slightly exceed the size range of needle rollers as stipulated by ISO.

Needle roller bearings include drawn cup and solid radial bearings, as well as application-specific cam followers, roller followers. Thrust bearings include thrust needle bearings. Although not classified as a rolling bearing, there is also a spherical sliding bearing that supports radial and axial loads.

Cage & Needle Roller Assemblies

The cage has a unique structure that facilitates handling by holding the rollers securely in place.
The outside surface of the cage serves as a guide face and helps create favorable lubricating conditions.
The cage guides the rollers accurately to ensure that stable roller movement is maintained.
The single-piece cage has high strength and rigidity and facilitates the free circulation of lubricant.
High load capacity is possible due to the presence of many rollers of relatively long length.
To prevent stress concentrations on both ends of the rollers (edge loads), appropriate crowning is applied.

Drawn Cup Needle Roller Bearings

Drawn cup needle roller bearings are available in two types: caged and full complement. Drawn cup outer rings are made of carefully selected alloy steel sheet. They are surface-hardened after precise pressing, giving them a unique structure.
The outer ring is precisely pressed and is in tight line contact with the rollers. Optimum heat treatment gives the raceway surface uniform strength and the ability to carry heavy loads.
The low height of the bearings saves space so machines can be made more compact and lightweight.
The bent part of the drawn cup outer ring securely holds the rollers and/or cage and acts as a labyrinth seal that prevents both the entry of dust and dirt and lubricant leakage. At the same time, it enhances the strength of the outer ring end faces.
When the shaft has adequate hardness and is finished to proper dimensional accuracy, the inner ring can be omitted and space in the radial direction can be saved.
As securing in the axial direction is achieved by press fitting, a locating snap ring, collar, housing shoulder or the like is not required. This simplifies the housing structure and facilitates low-cost design.
Mounting is made easier because press fitting can be performed with an arbor press or the like.
Lubricating the bearing is easy and a lubrication hole can also be provided upon request.
If a closed type is used at the shaft end, savings can be made on the housing end cover.
The full complement roller bearing carries the load on many rollers and thus maximizes load capacity.
Among full complement roller bearings, bearings whose rollers are held in place by grease before assembly have the maximum load capacity because the rollers have the longest possible length.
The cage of the needle bearing accurately guides the rollers at the pitch diameter of the rollers. The surface of the cage is hardened to reduce frictional torque and increase rigidity and wear resistance.
The unique structure of the cage allows extensive space for storing lubricant, thus enabling smooth lubricant circulation and increasing grease life.

Solid Needle Roller Bearings

The bearing ring can sustain high shock loads because it is precisely ground after being heat treated.
Providing high load capacity, many rollers are held in the outer ring by strong integrated ribs.
The unique single-piece cage is also excellent for high speeds as the cage accurately guides the rollers at the roller pitch diameter at both ends of the rollers.
Considerable space is allotted for lubricant and lubricant life is long.
The cage is surface treated, increasing wear resistance and rigidity.
Appropriate crowning is applied to the rollers to avoid edge load.
Outer rings provided with a lubrication groove and lubrication hole facilitate the replenishment of lubricant.
As the size variation per unit of roller diameter is small, the distribution of the roller load is favorable and bearing life is long

Thrust Bearings

Making compact design feasible, the height of the cross-section is similar to that of a conventional thrust washer.
The cage, which is made of two steel sheets precisely pressed, holds and accurately guides the rollers. The cage is surface hardened to increase wear resistance and rigidity.
There are thrust washers of various thicknesses available to meet the requirements of different applications.

Cam Followers and Roller Followers

The thick-walled outer ring made of high- carbon chromium bearing steel, which is finished by grinding after hardening, has high shock resistance and is highly resistant to deformation.
The cam follower has lubrication holes in three places. Lubrication can be provided easily from any of these three locations.
Crowning is applied to the rollers in order to avoid edge loading.
The labyrinth seal structure reduces friction. In addition, a special thrust washer is integrated in order to enhance heat seizure resistance.
Increasing shock resistance, the shaft of the cam follower has a hardened raceway surface.
The roller follower can carry heavy loads because both ends are supported.

Needle Rollers

There are a variety of end faces available from which an appropriate shape can be selected for specific applications.
Rounded rollers are the most widely used.
Flat rollers have a longer effective load- carrying length.
Crank pin rollers are suitable for where the corner of the shaft or housing step is considerably rounded.
Appropriate crowning can be applied for various usage conditions.

Spherical Plain Bearings

Since the structure is composed simply of an inner ring with spherical outside and an outer ring with a spherical bore, this bearing is ideal for applications where the inner and outer rings are misaligned.
Carefully selected high-carbon chromium bearing steel is used, and high load capacity is achieved thanks to ideal hardening.
Bearings with single-cut outer rings are not separable even without snap rings.
Bearings with double-cut outer rings are assembled by a wire snap ring into a single body.
The lubrication grooves and lubrication holes provided in the inner and outer rings facilitate re-lubrication.
After phosphate coating, a coating of molybdenum disulfide is applied to the whole surface.

Needle Roller Bearings for Universal Joints

While the tightening method is mainly used for securing drawn cup needle bearings in a yoke hole, another method employs a rose washer and bearing assembly is carried out using special equipment. Universal joints made by assembling drawn cup needle bearings have the following characteristics:
1. It is possible to impose a light preload between the bearing inner bottom and cross shaft end.
2. It is possible to have the cross shaft’s rotating center aligned with the shaft center.
3. Universal joints made in this way are economical and contribute to making products more compact and lightweight.
As solid needle bearings can sustain heavier loads than drawn cup needle bearings, universal joints with solid needle bearings are suitable for medium and heavy-duty motor vehicles.

Drawn Cup Roller Clutches

There are three types with a clutch only: FC, FCL and RC; and three types with a clutch and bearing combined: FCB, RCB and FCBN.

The unique structure of the drawn cup outer ring makes the clutch lightweight and compact.
The height of the cross-section is the same as standard drawn cup needle bearings and the torque capacity is high.
Performance is accurate and friction torque is low during overrunning.
Installation can be done in the same way as for drawn cup needle bearings, that is, by simply press fitting the unit into the housing.

NSK Needle Roller Bearings https://www.nsk.com/common/data/ctrgPdf/bearings/e1419c.pdf