Lead Babbitt Applications
The eponymous babbitt is named after Isaac Babbitt
Babbitt formulated a metal alloy in 1839 that was successfully used as the bearing surface in metal bearings. Also know as Babbitt metal, white metal or bearing metal, the exact formulation invented by Babbitt is not know, however several compositions have been created, some common ones involve alloys of lead and are known as lead babbitt:
- 80% lead, 15% antimony, 5% tin
- 76% copper, 24% lead
- 75% lead, 10% tin
- 67% copper, 28% tin, 5% lead
Babbitt metal is often used as the surface layer in a the moving surface of multi-metal structure bearings.
Babbitt metal is soft and easily damaged so it seems at first to be an unlikely material for bearings, however the detail structure of the metal consists of hard crystals embedded in softer material, when this material wears it creates lubricant paths within the bearing between the hard crystals that provide the actual bearing surface.
Traditional Babbitt bearings are cast in place around a shaft loosely embedded in a cast iron pillow block, through a hole that eventually becomes a lubricating hole. After casting the metal is trimmed back, lubricating oil ways are cut into the surface and the bearing is “run in” at low loads and revolution..
The expression a “run bearing” also derives from this style of bearing, since failure of lubrication will lead to heat build up due to friction in the bearing, eventually leading to the bearing metal liquefying and running out of the pillow block.
Before the advent of low cost electric motors, power was distributed through factories from a central engine via overhead shafts running in hundreds of Babbitt bearings.
Lead based babbitts are more economical and used for low speed, uniform speed and moderate pressure as in line shafting, electric motors and general machinery. These babbitts are also used in applications subjected to shock loads.
Nuclead can make any custom babbitt. Supply us with your specifications and we’ll fabricate and certify to your special needs.
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