2021 Bearing Type Selection Guide

Bearing Selection Guide

2021 latest bearing type selection guide. To make the mechanical device play the expected performance, it is very important to choose the most suitable bearing. In addition, the selection of bearings requires research from many factors and evaluation of the selection of bearings from various angles. Although there are no special requirements, the general sequence is as follows

  • Master the operating conditions of mechanical devices and bearings, etc.
  • Clear requirements for bearings
  • Select the bearing
  • Selection of bearing arrangement
  • Select bearing size
  • Selection of bearing specifications
  • How to install the selected bearing
Bearing selection guide edited

Bearing operating conditions and environmental conditions

Correctly grasping the location of the bearing in the mechanical device and the conditions of use and environmental conditions are the prerequisites for choosing a suitable bearing. For this, it is necessary to obtain the following data and information:

  • Function and structure of the mechanical device
  • Where the bearing is used
  • Bearing load (size, direction)
  • Rotation speed
  • Vibration, shock
  • Bearing temperature (ambient temperature, temperature rise)
  • Ambient atmosphere (corrosiveness, cleanliness, lubricity)
Bearing type selection guide
2021 Bearing Type Selection Guide -TFL

The choice of bearing arrangement

Generally, the shaft is supported by two bearings in the radial and axial directions. At this time, the bearing on one side is called the fixed side bearing, the effect of relative axial displacement between. The other side is called the free side, which only bears the radial load and can move relative to the axial direction, which solves the problem of shaft expansion and contraction caused by temperature changes and the clearance error of installing the bearing.

  For fixed-side bearings, it is necessary to select a bearing that can move the rolling surface in the axial direction (such as cylindrical roller bearings) or on the assembly surface (such as radial ball bearings). When the fixed and free sides are the same on relatively short shafts, use bearings that only move in one direction (such as centripetal thrust ball bearings).

The choice of bearing arrangement
2021 Bearing Type Selection Guide -TFL

Bearings and It’s Types

Generally, all types of machinery are provided with supports for rotating shafts; the supporting device is known as a bearing. In other words, a bearing is a machine element that constrains relative motions and is used to reduce the friction between moving parts.  

Bearing employs to support, guide, and restrain moving the element. This is a stationary member, and it carries the load. 

The part of the shaft supported by the bearing is known as the journal, a moving member. Bearings are classified according to the type of operation they do. 

∙ The motions allowed, or 

∙ to the directions of the loads or forces applied to the parts. 

The typical applications of bearings are: 

1. Shafting in workshops, 

2. Spindles of a machine tool such as a lathe, drilling, milling machine, etc. 

3. The crankshaft of engines, and axles of automobiles, etc. 

Classification of Bearings 

There are three main classifications of bearings, according to the direction of load, viz., 

1. Journal or radial bearing, 

2. Footstep bearing, 

3. Thrust or collar bearing. 

∙ A journal or radial bearing afford support to the shaft at a right angle to the shaft axis. 

∙ A footstep or pivot bearing support shaft parallel to the shaft axis and the end of the shaft rests on the bearing surfaces. 

∙ A thrust or collar bearing provides support to the shaft subjected to end or axial thrust.

The surfaces of the bearing are generally flat or cylindrical. And they may consist of nonferrous metal surfaces known as bushes or hardened steel races supported by steel balls or rollers. In the above case, the bearing is known as bush bearings, and the latter is known as a ball or roller bearings. 

Bearing type 

Following are the different types of bearings: 

1. Bush Bearing 

2. Plummer Block 

3. Thrust Bearing  

1. Foot Step Bearing  

Rolling contact or Anti-friction Bearing  

1. Ball and Roller Bearings  

Read also: Gear Terminology: Basic Terms Used In Gear 

Bush Bearings 

The simplest type of bush bearing is shown in the figure. It consists of a cast-iron bearing block and a  brass or gunmetal bush. In these bearing types, The base plate of the bearing block provides holes for bolting down the bearing in position. 

At the top of the bearing, a counterboring oil hole passes through the block and bush to facilitate lubrication of the shaft and the bush. 

It is using for the shaft, which carries light loads and which rotate at slow speeds. In this type of solid bearing, the shaft may introduce and removed wisely. 

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Plummer Block 

When a long shaft requires support at an intermediate point, a pedestal bearing or more Plummer block is used. 

It consists of: 

1. A cast-iron pedestal or blocks with a sole, 

2. Tow split gum metal or bushes, 

3. A cast-iron cap and two square-headed bolts for fastening the cap and the block together. 

A projecting snug in the bottom bush, fitting in the corresponding hole in the body or block, prevents their rotation. The bush is preventing from moving along the length of the shaft by two collars at the sides. It is made of two halves to help. 

∙ Placing and removal of the shaft in and from the bearing. 

∙ Change for wear in the bushes, and 

∙ Renewal of the bushes. 

In a bush bearing. There is a rubbing action between the outer surface of the shaft and the inner surface of the bearing. And the resulting friction minimizes by the presence of a film of lubrication oil. 

For line shafting, ring oiling may be considered the safest and most efficient type under the ordinary service condition. 

Read also: Screw Thread Terminology and Types of Screw Threads 

Thrust Bearings

In thurst bearing, the bearing pressure will be axial. The axis of the shaft may have vertical or horizontal. 

Suppose the axis of the shaft is vertical; the thrust bearing is known as footstep bearing. If the axis of the shaft is horizontal, the thrust bearing is known as a roller bearing. 

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Foot Step Bearing 

The figure shows a simple type of footstep bearing. It is suitable for supporting a vertical shaft. It consists of a cast-iron block and a gunmetal bush. The lower end of the shaft rests on a steel disc having concave seating. 

In this type of bearing, the disc is prevented from rotating along the shaft and the shaft by partially inserting the pin into the bearing seat and partially inserting the disc. The bushing prevents rotation with the shaft by a tight fit provided at the neck below the collar. 

The main disadvantages of this type of bearing are that it is difficult to achieve adequate lubrication.  This type of bearing is generally using for slow-speed shafts carrying light loads. 

Generally, the vertical shaft is uncommon in the ordinary transmission of power. But they often occur on machine practice in machine tool turntables, textile machinery, etc. 

Rolling Contact or Anti-friction bearings

It is well-known that a smooth rounded surface will roll over a similar surface more than when it is sliding. This phenomenon employs hard chrome steel balls or rollers to run in special design cages to provide bearings with low friction loss. 

In these bearing types, the motion between the shaft and the bearing surface is of pure rolling.  Since the rolling friction is much less than the sliding friction, this type is known as an antifriction bearing. 

The two types of antifriction bearing

1. Ball Bearing 

2. Rolling Bearing. 

The outstanding feature of the antifriction bearings is their low starting frictions, which will be practically the same while running also. This renders their application particularly suitable for machinery which has to start, stop and restart frequently. 

Read Also: Clutch – Its Main Parts and Working Principle of Clutch 

Ball and Rolling Bearings 

The figure shows the simplest type of ball and rolling bearing. It consists of a rigid steel ball and rolling, between two suitable grooves, hard steel rings, known as races. 

In this type of bearing, the ball and rolling are retaining in positions by separators. These are known as cages, usually made of brass. The inner race should be of ‘drive fit’ on the shaft to rotate with it.  The outer race fits into the housing and does not rotate.  

A ball and rolling being free to rotate, the action in them is not that of rubbing but of rolling between the balls and rolling and their races. Since the rolling friction is much less than the sliding friction,  ball and rolling bearing are antifriction bearings. 

Rolling bearings maintain accurate alignment of every part over a long period and can carry the heavy momentary load. This renders them suitable for machinery which requires frequent starts and stops. Rolling makes the line contact with their races, while balls make point contact.  Rolling, thus, has a higher load-carrying capacity.

At the point (or line) of contact between a ball (or rolling) and its races, the pressure intensity is as great as film lubrication, as usually understood is impossible. Lubrication is necessary to protect the polished surface from rust and help exclude foreign matter. Pure mineral grease is so generally used. 

Read Also: Chain Drives and Types Of Chains 

Advantages of Rolling Contact Bearing 

1. Starting and running friction is negligible. 

2. Can be used for radial and thrust load. 

3. Requires minimum lubrication. 

4. Suitable for high speeds. 

5. Serves for long life. 

Disadvantages of Rolling Contact Bearings 

1. High initial cost. 

2. More liable to shock loads. 

3. Requires a very high precision machining of the bearing housing. 

4. Not suitable for heavy loads. 

5. Worn-out parts cannot be repaired; the only entire bearing unit is to be replaced.