Six Common Questions and Solutions in Rolling Bearing Installation

1. Are there any requirements for the mounting surface and installation location?

Yes. If foreign particles such as metal shavings, burrs, or dust enter the bearing, they can cause noise and vibration during operation and may even damage the raceways and rolling elements. Therefore, before installing the bearing, you must ensure that both the mounting surfaces and the installation environment are clean.

II. Must bearings be cleaned before installation?

The bearing surface is coated with anti-rust oil; you must carefully clean it with clean gasoline or kerosene, then apply a clean, high-quality lubricant suitable for high-speed, high-temperature applications before installation and use. Cleanliness has a significant impact on bearing life as well as vibration and noise levels. However, please note that fully sealed bearings do not require cleaning or relubrication.

III. How to Select Lubricating Grease?

Lubrication has a critical impact on bearing operation and service life. Here is a brief overview of the general principles for selecting grease. Grease is composed of a base oil, a thickener, and additives; different types—and even different grades within the same type—exhibit widely varying performance characteristics and allowable speed limits, so careful consideration is essential when making your selection. The performance of a grease is primarily determined by its base oil: low‑viscosity base oils are typically suited to low temperatures and high speeds, while high‑viscosity oils are preferred for high temperatures and heavy loads. The thickener also plays a key role in lubrication performance, and its water resistance dictates the grease’s overall water resistance. As a general rule, greases from different manufacturers should not be mixed, and even greases with the same thickener can adversely affect one another due to differences in their additive packages.

4. When lubricating bearings, is it better to apply as much grease as possible?

It is a common misconception that the more grease you apply when lubricating a bearing, the better. Excessive grease in the bearing and its housing leads to over‑agitation, which can generate extremely high temperatures. The appropriate amount of lubricant to fill the bearing is about one‑half to one‑third of the internal space; at high speeds, this should be reduced to one‑third.

5. How do I install and remove it?

During installation, do not strike the bearing’s end faces or non‑load‑bearing surfaces directly. Instead, use a press block, sleeve, or other specialized mounting tools to ensure even force distribution; never transmit force through the rolling elements. Applying a thin layer of lubricant to the mounting surfaces will facilitate smoother installation. If the interference fit is substantial, heat the bearing in mineral oil to 80–90°C and install it promptly, strictly ensuring that the oil temperature does not exceed 100°C to prevent tempering, which can reduce hardness and impair dimensional recovery. When removal proves difficult, we recommend using a puller to gently draw the bearing outward while carefully pouring hot oil onto the inner ring. The heat will cause the inner ring to expand, making it easier to separate.

6. Is it always better for a bearing to have the smallest possible radial clearance?

Not all bearings require a minimum operating clearance; you must select an appropriate clearance based on the specific operating conditions. According to the Chinese national standard GB 4604‑93, radial clearances for rolling bearings are classified into five groups—Group 2, Group 0, Group 3, Group 4, and Group 5—with clearance values increasing sequentially from smallest to largest. Group 0 represents the standard clearance. The basic radial clearance group is suitable for typical operating conditions, normal temperatures, and common interference fits. For bearings operating under special conditions—such as high temperature, high speed, low noise, or low friction—it is advisable to use a larger radial clearance. Conversely, for precision spindles and machine tool spindle bearings, a smaller radial clearance is preferred. Roller bearings may maintain a small amount of operating clearance. Additionally, for split-type bearings, clearance is not a critical consideration. Finally, the operating clearance of a bearing after installation will be smaller than its original clearance prior to installation, as the bearing must withstand a certain load during rotation, and elastic deformation resulting from bearing fit and applied loads also contributes to this reduction.

Lubrication method

Currently, bearing lubrication is primarily carried out using two distinct methods: grease lubrication and oil lubrication. To ensure optimal bearing performance, it is essential first to select a lubrication method that suits the operating conditions and intended application. When considering only lubrication performance, oil lubrication generally offers superior lubricity. However, grease lubrication excels in simplifying the design of the bearing housing and surrounding components. A comparative analysis of the advantages and disadvantages of grease and oil lubrication is therefore warranted.

Bearing Installation

The correctness of bearing installation affects accuracy, service life, and performance. Therefore, the design and assembly departments must conduct thorough studies on bearing installation. It is recommended to perform installation in accordance with established operating procedures. Typical items included in these procedures are as follows:

(1) Clean the bearing and its associated components;

(2) Inspect the dimensions and finish of the associated components.

(3) Installation;

(4) Inspection after bearing installation;

(5) Supply lubricant.

It is recommended to open the bearing packaging immediately before installation. For grease lubrication, no cleaning is required; simply fill the bearing with grease. For oil lubrication, routine cleaning is generally unnecessary; however, for instruments or high-speed bearings, use clean oil to thoroughly remove any anti‑rust coating applied to the bearing. Bearings that have had their anti‑rust coating removed are prone to rusting and should not be left unattended. Furthermore, bearings already filled with grease may be used directly without prior cleaning.

Bearing installation methods vary depending on the bearing design, fit, and operating conditions. In most cases, since the shaft typically rotates, an interference fit is required for the inner ring. For bearings with cylindrical bores, press‑fit installation is commonly used, or thermal expansion mounting may be employed. When dealing with tapered bores, the bearing is either mounted directly onto a tapered shaft or installed using a sleeve.

When mounting into the housing, a loose fit is typically used, with an interference fit on the outer ring; installation is usually performed by press‑fitting, or alternatively by a cold‑shrink fit achieved through cooling. When using dry ice as the coolant for cold‑shrink fits, moisture in the air can condense on the bearing surface. Therefore, appropriate rust‑preventive measures are required.