What is Spherical Plain Bearings (Ball Bushings)?

Spherical Plain Bearings (Ball Bushings)

The basic parts which make up a spherical plain bearing are the following:

1. Inner Ring
2. Outer ring

These bearings are often referred to in the trade as Ball Bushings. An offshoot of this type of bearing is the rod end which is basically a spherical plain bearing contained in a housing.

It should be noted that spherical plain bearings and rod ends contain no rolling elements (Balls, Rollers). Movement is taken by the sliding action between the inner and outer ring, which have sliding contact surfaces. Because of this, spherical plain bearings and rod ends are only used where there are very slow rotation or oscillating (angular or not full rotation) movements.

There are basically three different combinations of shifting surfaces in these bearings, which determines the application for which they are used. These are:

Hardened steel inner ring on Hardened steel outer ring. This type requires lubrication or maintenance.
Hardened steel inner ring on bronze outer ring - low maintenance type.
Chromium steel inner ring on PTFE or Teflon outer ring - Maintenance free type.
COMPONENTS

We will now examine the basic parts of spherical plain bearings in more detail.

1) Inner Ring - Imagine a slice taken from the centre of a solid steel ball, which then has a hole drilled through the centre. This is the appearance of the inner ring of a spherical plain bearing. The inner ring is made from either hardened bearing steel or hardened chromium steel, depending on the sliding contact surface required.

2) Outer Ring- The outer ring of a spherical plain bearing has a cylindrical or parallel outside diameter and a spherical inside diameter into which the ball type inner ring fits. It is made from hardened steel which can be coated with bronze or PTFE depending on the sliding contact required.

It should be noted that due to the 'Ball and Socket' type arrangement of the inner and outer rings, these bearings can accept a certain amount of misalignment or tilting of the shaft relative to the housing, in much the same way as a spherical roller bearing.

Due to the large area of contact between the inner and outer rings, the bearing can accept very high radial loads and a certain amount of axial load at slow rotational or oscillating speeds.

Numbering System

Yousen bearing carry INA Elges Brand plain bearings and consequently use their numbering system. The Numbers consist of a prefix, size designation and suffix.

Part No
Explanation
GE__DO
Steel on steel types - standard type, available sealed with the additional suffix 2RS
GE__LO
Steel on steel - extended inner ring
GE__ZO
Steel on steel - standard type - inch sizes
GE__SX
Steel on steel - angular contact typ
GE__AX
Steel on steel - thrust type
GE__UK
PTFE (Teflon) on hard chrome type - available sealed - suffix 2RS
GE__SW
PTFE on hard chrome - angular contact type
GE__AW
PTFE on hard chrome, thrust type
GE__HO
Similar to DO type but with extended inner ring

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