Cixi Baoci Bearing Co., Ltd

The five major components of a bearing are the outer ring (large ring), inner ring (small ring), balls, cage, and grease. These components collectively form the basic structure of a bearing.

open bearings or sealed bearings

Bearings can be categorized as open bearings or sealed bearings. In operation, most bearings require protection against dust and contamination, so dust covers or seals are often added. Bearings without dust covers or seals are referred to as open bearings, while those equipped with dust covers or seals are called sealed bearings (also known as closed bearings).

Classification of metal seals-ZZ

Dust covers can be further divided into two types based on their structure: removable and non-removable. Non-removable dust covers, commonly called fixed covers, are generally installed through stamping. They provide reliable contact and are compatible with automated cover assembly, making them widely used in miniature and small bearings. Removable dust covers, known as removable covers, use a spring ring to hold the cover in place. This design is often adopted in thin-walled miniature bearings to reduce deformation of the outer cylindrical surface.

Classification of rubber seals  -2RS、-2RZ

Bearings fitted with seals can be classified as contact seals (2RS ) or non-contact seals (2RZ). In a contact seal, the inner diameter or inner face of the seal is in contact with the outer diameter or shoulder face of the bearing's inner ring. In a non-contact seal, there is no such contact. Bearings with dust covers are considered a type of non-contact sealing.

Although sealed bearings have slightly more components than open bearings, they offer significant advantages. They provide dust protection, prevent lubricating grease from leaking during operation, simplify the structure of the host machine, and make maintenance and replacement easier—all with minimal additional cost. For these reasons, sealed bearings are widely used in various applications.

Functions of the Five Major Components

1. Inner and Outer Rings

The inner ring fits onto the shaft, while the outer ring fits into the housing. The end faces of the bearing contact the shaft shoulder or housing shoulder, providing axial positioning for the rings. Chamfers on the rings ensure reliable contact between the end faces and the shoulders.

During operation, typically one ring rotates while the other remains stationary. For example, in most electric motor bearings, the inner ring rotates. Bearings with a rotating inner ring are generally considered to have a longer service life than those with a rotating outer ring.

The raceways of the inner and outer rings, which contact the balls, are the primary working surfaces of the bearing. Their geometry and surface finish directly influence friction, wear, vibration, and overall service life.

2. Balls

The balls serve as the rolling elements and rotate within the raceways of the rings. The bearing’s load‑carrying capacity, both radially and axially, largely depends on the number and diameter of the balls.

Balls operate at high rotational speeds and are subjected to significant contact stress, making their precision and material quality critical to bearing performance.

3. Cage (Separator)

The cage, also known as a separator, evenly spaces the balls. This ensures smooth operation, reduces friction, and allows the bearing to carry loads efficiently. Depending on the bearing design and operating speed, cages can come in various materials and structures.

4. Grease (Lubricant)

The grease provides lubrication, ensuring smooth operation and minimizing wear between the rolling elements and raceways. Different operating temperatures and conditions require greases with specific performance characteristics to maintain optimal bearing function.

Bearing Code Designations

• N – The outer ring of the bearing has a snap ring groove.

• NR – The outer ring has a snap ring groove and is supplied with a snap ring.

• -RS – The bearing has a rubber seal (metal insert type) on one side. This is a contact-type seal.

• -RZ – The bearing has a rubber seal (metal insert type) on one side. This is a non-contact seal.

• -Z – The bearing has a shield on one side.

• -RZZ – The bearing has a rubber seal (metal insert type, non-contact) on one side and a shield on the other side.

• -RSN – The bearing has a rubber seal (metal insert type, contact type) on one side and a snap ring groove on the outer ring.