Page History: Babbitt - What is Babbitt?

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Babbitt metal, also called white metal, is a soft, white non-ferrous alloy used to provide a bearing surface. It has properties that help reduce friction which make it a good material to use in a plain bearing. It was invented in 1839 by Isaac Babbitt in Taunton, Massachusetts, USA. The term is used today to describe a series of alloys used as a bearing metal.

Original and true babbitt is primarly a tin based metal but some materials that are called babbitt are also lead based. Here is a breakdown of several types of Babbitt that are avaliable and commonly used when restoring old machinery:

• Lead Based Babbitt. The cheapest babbitt that you can buy. Also the softest. Composition is 80.25 percent lead, 14.75 percent antimony and 5 percent tin. While this material would work fine for light duty and low speed applications, for just a little more money, you can get a much better quality material. Probably best to shy away from for most machinery applications. Pouring Temperature is 650 degrees F. Prices vary buy expect to pay around $4.50 per pound.
  

• Lead Based Coppered Babbitt. The Mid-grade Babbitt product. Composition is 74.5 lead, 14.75 percent antimony, 10 percent tin, 0.25 percent copper and 0.5 percent arsenic. With twice as much tin as plain lead based Babbitt, as well as some copper and arsenic, this Babbitt is stronger and more suited for heavy loads. Still only recommended for low speed applications - not what you would want to use on a jointer or planer head but probably plenty adequate for a band saw with wheels only turning in the 400-500 RPM range. Prices vary but expect to pay around $6.00 per pound. For no more than it cost, this Babbitt would nearly always be preferred over plain lead based. Pouring Temperature is 700 degrees F.
  

• Tin Based Babbitt. The best choice for high-speed applications (such as jointers and planers) and hard to lubricate bearings. Composition is 89% tin, 7.5% antimony, and 3.5% copper. In reality, probably overkill for band saw bearings but sure would not hurt to be safe than sorry. While the higher tin content does make this Babbitt more expensive, when you consider the cost of time and labor for pouring bearings, probably money well spent. Cost for tin based products is much higher than the lead based at approximately $16.50 per pound. Pouring Temperature is 725 degrees F.
  

Originally used as a cast in place bulk bearing material, it is now more commonly used as a thin surface layer in a complex, multi metal structure.

Babbitt metal is soft and easily damaged, and seems at first sight an unlikely candidate for a bearing surface, but this appearance is deceptive. The structure of the alloy is made up of small hard crystals dispersed in a matrix of softer alloy. As the bearing wears the harder crystal is exposed, with the matrix eroding somewhat to provide a path for the lubricant between the high spots that provide the actual bearing surface.