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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.

 

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