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Miniature & small ball bearings

18. 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 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 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.

Lubricant type

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
luorine 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.

Grease filling amount

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.

Filling amount symbol Filling amount
X 5~10%
L 10~15%
T 15~20%
No symbol (standard) 25~35%
H 40~50%
J 50~60%


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.

Name Thickener Base oil Noise Torque High
High speed Resin
Conductivity Low dust Price Code Characteristics Base oil kinematic viscosity
mm2 S@40°C
temperature range
Representing value Representing value
Lithium soap grease Li soap Ester, etc. ◎◎ × - × ◎◎ LY121 General 24 250 -50~+150
◎◎ ◎◎ × - × LY72 Low torque 16 275 -50~+130
Urea grease Urea Synthetic hydrocarbon - ◎◎ LY551 Heat resistance, high speed 48 235 -40~+200
Ester ◎○ × × - - LY706 Heat resistance 100 263 -40~+180
Fluorine grease PTFE Fluorine - ◎◎◎ - -

- - × LY500 Heat resistance 190 280 -50~+260
- ◎◎ - - × LY586 Heat resistance 85 280 -65~+260
- ○○ ◎◎ - - ×× LY699 Heat resistance, low torque 85 280 -50~+220
Fluorine + Ester - ◎◎◎ - - - - LY655 Heat resistance, low price 210 290 -40~+200
Conductive grease Carbon Synthetic hydrocarbon × - - × - LY764 Conductivity 120 260 -40~+120
Fluorine × - ◎◎ - × - × LY768 Conductivity, heat resistance 390 260 -30~+260
Oil - Ester ◎◎◎ × - × LO1 Low torque 12 -57~+177
Synthetic hydrocarbon ◎◎◎ - × LY650 Resin resistance 32 - -40~+130

Consult us for those with *.

Note: The operating temperature range is the catalog value of the lubricant manufacturer and not the possible operating temperature range of the bearing. (The setting method differs depending on the manufacturer.)

Remarks: Superior/inferior display mark: Superior ◎◎◎−◎◎−◎〇−◎−〇〇−〇−△−×−×× Inferior

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