Skip to main content

WHAT ARE BEARING METALS ?

 Bearing metals may be classified into the following groups :

 1. Copper Base Bearing metals containing copper, tin and lead.

 2. Tin-base bearing metals containing tin, antimony and copper.

 3. Lead - Base bearing metals containing lead, tin and antimony.

 4. Cadmium - Base Bearing metals containing cadmium and nickel. 

Those alloys in which tin, lead, and cadmium are predominating elements are designated as white-metal bearing alloys. They have the properties of high plasticity combined with the low hardness and comparatively low melting point, which facilitates the formation of  bearings by casting the metal directly in place and usually require no machining.




The copper based alloys are harder and stronger than the white metals and are used for which are required to resist heavier pressures. Tin-base white metals are used where bearings are subjected to high pressure and load, whereas for light roads and pressure lead - base alloys are used. Of the lead base alloys , the alloys which contain 80 percent lead and 20 percent antimony is generally used. Cadmium - base bearing metals have more favorable properties, especially at elevated temperatures, than the tin - base alloys. The compressive strength of the cadmium base bearing alloys are greater than those of tin-base alloys. 

To give an efficient bearing combinations the following conditions are necessary :

1. That the shaft and bearing be dissimilar in their nature with bearing softer than the shaft.

2. That the most efficient bearing metal is one consisting of small pieces of comparatively  hard  

3. That the bearing metals should have sufficient compressive strength to carry the bearing pressure, should wear to smooth surfaces as they rub together, and should develop a minimum of friction when they actually come in contact, as for example, when a shaft is staring or stopping.

 

Labels:

Comments

Post a Comment

Popular posts from this blog

Advantages And Disadvantages Of Air Refrigeration System :

 Advantages Of  Air Refrigeration : 1. The refrigerant used namely air is cheap and easily available. 2. There is no danger of fire or toxic effects due to leakages. 3. The weight to ton of refrigeration ratio is less as compared to other systems. Disadvantages Of Air Refrigeration : 1. The quantity of  Refrigerant used per ton of refrigeration is high as compared to other systems. 2. The COP of the system is very low. Therefore running cost is high. 3. The danger of frosting at the expander valves is more as the air contains moisture content. 
Post a Comment
Read more

SIMPLE CARBURETOR - CONSTRUCTION AND WORKING

CONSTRUCTION OF SIMPLE CARBURETOR :  The main Components of Simple Carburetor are : Float Chamber, float, nozzle, venturi, throttle valve, inlet valve, and metering jet . In the float chamber, a constant level of petrol is maintained by the float and a needle valve.  The float chamber is ventilated to atmosphere.  This is used to maintain atmospheric pressure inside the chamber. The float which is normally a metallic hollow cylinder rises and closes the inlet valve as the fuel level in the float chamber increases to certain level. The mixing chamber contains venturi, nozzle and throttle valve. The venturi tube is fitted with the inlet  manifold. This tube has a narrow opening called venturi. A nozzle is provided just below the centre of this venturi. The nozzle keeps the same level of petrol as that of the level in the float chamber. The mixing chamber has two butterfly valves.  One is to allow air into the mixing chamber known as choke valve. The other is to al...
Post a Comment
Read more

MELTING FURNACES FOR FERROUS METALS : CUPOLA AND ITS WORKING

Various types of melting furnaces are used in different foundry shops, depending upon the quantity of metal to be melted at a time, and the nature of work that is carried out in the shop.  The primary objective in cupola is to produce iron of desired composition, temperature and properties at the required rate in the most economical manner. Besides, this furnace has many distinct advantages over the other types, e.g., simplicity of operation, continuity of production, and increased output coupled with a high degree of efficiency.  Description Of a Cupola : The Cupola Furnace consists of a vertical, cylindrical steel sheet, 6 to 12 mm thick, and lined inside with acid refractory bricks or acid tamping clay. The refractory bricks or the tamping clay used consist of  silicon oxide acid (SiO2) and alumina (Al2O3). The lining is generally thicker in the lower where the temperatures encountered are higher than in the upper region. The shell is mounted either on a brick work fo...
Post a Comment
Read more