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White Metal Bearings

Updated on July 17, 2013
White Metal Bearing
White Metal Bearing

Bearings are used on machineries to reduce wear and friction between running / moving surfaces. Various metals and alloys are used as bearings. There is always some kind of lubricant between running surfaces which takes the load acting on the bearing, thereby separating both running surfaces. Even though the oil film in between two surfaces takes load, 100% separation of surfaces is not guaranteed, especially while starting up of the machinery. Also foreign materials in lubricating oil can damage running surfaces. Hence careful selection of bearing material, considering the nature and amount of load, is essential for satisfactory performance of the machine.

Slot and Holes in the Bearing are for Retention of Lubricating Oil
Slot and Holes in the Bearing are for Retention of Lubricating Oil

White metal bearings are commonly used in auxiliary engine big end bearings. White metal bearing alloys may be either tin or lead base materials containing antimony and copper or antimony alone. Tin based white metals are sometimes referred to as "Babbitt metals", after Sir Issac Babbitt, who patented them originally. These metals are the most commonly used white metals because of

  • Good bearing surfaces, and
  • Uniform micro structure

The use of copper in a white metal ensures uniform distribution of the hard cuboids of the inter-metallic compound of antimony and tin within the soft thin rich matrix. Coefficient of friction for a white metallic bearing, when lubricated, is approximately 0.002. The melting point of white metal varies with composition but is approximately between 200 - 300 Degree Celsius.

Bottom End Bearing of an Auxiliary Engine Removed for Inspection
Bottom End Bearing of an Auxiliary Engine Removed for Inspection
Tin
Antimony
Copper
Lead
Uses
86%
8.5%
5.5%
-
Heavy Duty, High Temperatures
78%
13%
6%
3%
Normal Load Bearings
-
20%
-
80%
Normal to Low Load Bearings
Composition of Alloys for Particular Applications

There are both lead based and tin based white metals. As shown in the table, tin based white metals are widely used and they have good corrosion resistance and fatigue strength. Normally a bearing over layer of 90 % lead and 10 % tin is applied as galvanic coating. This is to make sure better conformity and embeddability between the surfaces. Another layer of tin is coated over the white metal bearing to protect it from corrosion. This layer is washed out while initial running in.

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    • jabelufiroz profile image
      Author

      Firoz 4 years ago from India

      Thank you Haseena

    • Haseena Firdousia profile image

      Haseena 4 years ago from India

      Wonderful hub explaining bearing.

    • jabelufiroz profile image
      Author

      Firoz 4 years ago from India

      yes you are right

    • profile image

      Alex 4 years ago

      these bearing can resist much higher loads.