Lubricants

Grease or oil is usually used to lubricate the bearing. In the case of miniature and small-diameter bearings, most are used for the life of the equipment without replacing the initially filled lubricant. Therefore, when selecting a lubricant, it is necessary to carefully consider the life, torque, rotating performance, noise level, etc.

Thickener is dispersed in base oil to make it semi-solid or solid. It consists of base oil, thickener and additives, and the characteristics are determined by the combination of these.
・Base oil
Base oils are roughly classified into mineral oil, synthetic oil and mixed oil.
・Thickener
Thickener is added to disperse in base oils to make them semi-solid (grease-like). It is an important substance in setting the properties and performance of grease. Thickeners are broadly classified into soap using metallic soap (such as lithium) and non-soap (such as urea) that does not use metallic soap.
・Additive
Additive is utilized to improve the physical and chemical performance of grease. Additive types include antioxidant, rust inhibitor, corrosion inhibitor and extreme pressure additive.

Oils are roughly classified into mineral oil, synthetic oil and mixed oil. Since oil is fluid and only a small amount is applied to the bearing, it is possible to reduce torque, but the life needs to be examined. It is also used as a base oil for grease.

Grease is broadly classified according to the thickener type, etc. as shown in Table 18-1.
The characteristics of typical grease are shown below.
・Lithium soap grease
Lithium grease provides excellent quietness and durability, and is the most widely used universal grease in general industries, automobiles and home appliances. A relatively low-cost grease.
･Urea grease
Urea grease has excellent heat resistance, high speed and water resistance, and is widely used in electrical components for automobiles, motors for vacuum cleaners and ventilation fans. In addition, there are greases that have excellent chemical attack resistance (resin cracking) when combined with synthetic oil.
･Fluorine grease
Fluorine grease has excellent chemical stability and is used in high-temperature environments such as around automobile engines. It is also used in vacuum environments. It is a very expensive grease.
･Conductive grease
Conductive grease has conductivity and can conduct electricity in bearings, and is used for copying machines and other devices that should not be electrified.

The standard grease fill amount for small-diameter and miniature rolling ball bearings is 30%. The fill amount is shown in the table on the right to adapt to the application.

In recent years, as devices become smaller and lighter, resin materials are increasingly utilized where bearings are incorporated. Some resin materials have poor chemical compatibility with certain oil and grease, and may cause deterioration or breakage. When selecting a lubricant, it is necessary to carefully consider the operating environment.