Lubricant selection is of critical importance for the performance of precision ball bearing.
Bearing performance, such as life, torque, rotation stability and noise, depend on the bearing lubrication choices, even when the same materials and components are used. Bearings are typically lubricated with oil or grease.
After the initial fill, the oil or grease are usually not refilled or replenished. Generally grease is standard in enclosure type bearings (bearings with seals or shields) because the life of the grease is longer than that of oil. Grease is composed of thickener and base oil. Fiber bonding and oil separation of the thickener plays an important role in grease. Fiber bonding keeps the oils in, and they are released gradually by oil separation. When only oil is used to lubricate a bearing, leaking is expected. The slow release of base oils due to oil separation makes longer lubrication life possible. When an application requires extremely low torque or torque fluctuations need to be minimized, oils are the preferred choice. Oil lubrication will spread more than grease. Grease lubricants are semi-solid and could add resistance against rotation. Grease performance may be enhanced by additives such as oxidation-resistant agents, lube agents (improving boundary lubrication), extreme pressure agents, and rust-inhibitor agents.