Which statement best describes babbit in engine bearings?

Which statement best describes babbit in engine bearings?

• A. It is a hard alloy used for gears
• B. It is a soft bearing material comprising tin and lead
• C. It is a ceramic coating for piston rings
• D. It is an oil additive for heat resistance

Answer: (B)

Babbitt refers to a soft bearing lining material. It is typically a tin-based alloy, often with lead (and sometimes antimony or copper), cast onto a bearing shell to create a smooth, conformable surface for the crankshaft journal. The softness allows the bearing to embed small debris and conform to minor journal irregularities while the oil film carries the load, protecting the shaft and providing low friction. It’s not a hard alloy used for gears, not a ceramic coating for piston rings, and not an oil additive for heat resistance, which is why this description best fits the concept.

Babbitt refers to a soft bearing lining material. It is typically a tin-based alloy, often with lead (and sometimes antimony or copper), cast onto a bearing shell to create a smooth, conformable surface for the crankshaft journal. The softness allows the bearing to embed small debris and conform to minor journal irregularities while the oil film carries the load, protecting the shaft and providing low friction. It’s not a hard alloy used for gears, not a ceramic coating for piston rings, and not an oil additive for heat resistance, which is why this description best fits the concept.