Introduction to Plain Bearings

Flat bearings (thrust bearings) are components composed of a flat cage assembly with needle rollers, cylindrical rollers, or steel balls, and a flat washer. Flat bearings 

are divided into flat bearings with needle rollers and flat bearings with balls.

The needle roller and cylindrical roller are held and guided by a flat cage. When used with different series of DF flat bearing washers, many different combinations can 

be provided for the bearing configuration.

Due to the use of high-precision cylindrical rollers (needle rollers) to increase the contact length, this bearing can achieve high load capacity and high stiffness in a very 

small space.

Another advantage is that if the surfaces of adjacent parts are suitable as raceways, washers can be omitted, which can make the design compact. DF flat needle roller 

bearings and flat cylindrical roller bearings use cylindrical surfaces of needle and cylindrical rollers as modified surfaces, which can reduce edge stress and improve service 

life.

The flat needle roller and cage assembly are the main components of the flat needle roller bearing. The rolling needle is maintained and guided by radially arranged bags. 

The profile of the cage has a specific shape and is formed using hardened steel strips. The small-sized cage is made of industrial plastic.

The high-precision needle roller diameter grouping tolerance is 0.002mm, ensuring uniform load distribution. The flat needle roller and cage components are guided by a 

shaft. In this way, even at high speeds, a relatively low circumferential velocity can be obtained by guiding the surface.

If the surface of adjacent parts is designed as a raceway surface to eliminate washers, a particularly space saving support can be obtained. If this plan cannot be implemented, 

using thin-walled steel AS series washers can also make the design compact with sufficient support.

Flat bearings mainly bear axial loads in assemblies and are widely used. Although the installation operation of flat bearings is relatively simple, errors often occur during 

actual maintenance, that is, the installation positions of the tight and loose rings of the bearings are incorrect, resulting in the bearings losing their function and the shaft 

neck quickly being worn. The figure shows that the tightening ring is installed on the end face of the stationary part, which is an incorrect assembly. The inner ring of the 

tight ring is in a transitional fit with the shaft neck. When the shaft rotates, it drives the tight ring and rubs against the end face of the stationary part. When subjected to 

axial force (Fa), there will be a torque of friction greater than the inner diameter fit resistance, causing the tight ring to rotate forcefully with the shaft fitting surface, exace

rbating the wear of the shaft neck.

When installing flat bearings, attention should be paid to the following points: (1) Distinguish the tight and loose rings of the bearings (judged based on the size of the 

bearing inner diameter, with a difference of 0.1~0.3mm in aperture).

(2) Distinguish the stationary parts of the mechanism (i.e. non moving parts, mainly referring to the assembly body).

(3) Regardless of the situation, the loose ring of the bearing should always rest against the end face of the stationary part.