Rolling bearings are essential components in mechanical engineering. Their designations are crucial identifiers for bearing type, structure, size, precision, and other information, making them crucial for bearing selection, procurement, installation, and maintenance. Rolling bearing designations typically consist of a prefix, base, and suffix, each with its own specific meaning and coding rules. Understanding the structure of rolling bearing designations helps engineers quickly and accurately understand bearing parameters, ensuring compatibility between bearings and mechanical devices, thereby improving equipment efficiency and reliability.
The basic designation is the core of a rolling bearing designation, used to identify the bearing type, structure, and size. It consists of three parts: the type designation, the size series designation, and the bore diameter designation. The type designation uses numbers or letters to indicate the basic bearing type, such as “6” for deep groove ball bearings, “N” for cylindrical roller bearings, “3” for tapered roller bearings, and “5” for thrust ball bearings. The size series designation consists of a width designation and a diameter designation. The width designation indicates the width dimension series of the bearing (or height dimension series for thrust bearings), while the diameter designation indicates the outer diameter dimension series. The combination of the two designations distinguishes bearings with the same bore diameter but different outer diameters and widths. For example, in the size series designation “02,” “0” represents the width designation and “2” represents the diameter designation. The inner diameter code indicates the inner diameter size of the bearing. When the inner diameter is in the range of 20-480mm, the inner diameter code multiplied by 5 is the bearing inner diameter (unit: mm). For example, the inner diameter code “06” indicates an inner diameter of 30mm. For bearings with an inner diameter less than 20mm or greater than 480mm, there are special regulations for the inner diameter code, such as “00” for an inner diameter of 10mm, “01” for 12mm, etc.
Prefix designations are used to identify bearing components and are typically composed of letters. They are primarily used for combined bearings and bearing units. For example, “L” represents the separable inner or outer ring of a separable bearing, “K” represents the rolling element and cage assembly of a bearing, and “R” represents a bearing without a separable inner or outer ring (such as a needle roller bearing). Prefix designations clearly identify bearing components and facilitate assembly and maintenance. For example, in the bearing designation “LNU207,” “L” represents the separable inner ring, and “NU207” represents the outer ring and rolling element assembly of a cylindrical roller bearing. The overall designation represents a cylindrical roller bearing with a separable inner ring.
The suffix code follows the basic code and indicates special requirements for the bearing, such as the internal structure, tolerance grade, clearance, cage structure, seals, and dust protection devices. Composed of letters and numbers, it is categorized, in order, as supplementary code, tolerance grade code, clearance code, and configuration code. The supplementary code indicates changes to the bearing’s internal structure. For example, “C” designates an angular contact ball bearing with a nominal contact angle of α = 15°, “AC” designates α = 25°, and “B” designates α = 40°. “E” indicates a reinforced design, meaning the bearing has an increased number of rollers and higher load capacity. The tolerance grade code indicates the bearing’s manufacturing accuracy and is categorized as Grade 2, Grade 4, Grade 5, Grade 6, Grade 6X, and Grade 0, designated by the letters “B,” “C,” “D,” “E,” “EX,” and “G,” respectively. Grade 0 is the standard grade and is the most widely used, while Grade 2 offers the highest accuracy and is primarily used in precision machinery. The clearance code indicates the radial clearance or axial clearance of the bearing, which is divided into Group 1, Group 2, Group 0, Group 3, Group 4 and Group 5, represented by the letters “C1”, “C2”, “C0”, “C3”, “C4” and “C5” respectively. Group 0 is the basic clearance, and the clearance increases successively. The selection should be determined according to factors such as operating temperature and interference fit.
The cage structure, material code, and seal/dust shield designation are also important components of the bearing suffix designation. The cage structure designation uses letters to indicate the cage type, such as “M” for a copper alloy solid cage, “2F” for a steel solid cage, “TN” for an engineering plastic molded cage, and “Y” for a stamped steel cage. The seal/dust shield designation indicates the bearing’s sealing method, such as “Z” for a single-sided stamped steel seal cap, “2Z” for a double-sided stamped steel seal cap, “RS” for a single-sided rubber seal, “2RS” for double-sided rubber seals, and “ZZ” for double-sided steel seal caps. In addition, there are some special-purpose suffix designations, such as “QJ” for a four-point contact ball bearing, “N” for a retaining groove on the outer ring, and “NR” for a retaining groove and retaining ring on the outer ring.
Understanding the structure of rolling bearing designations requires analysis with specific examples. For example, in the bearing designation “6208/C3,” “6” represents a deep groove ball bearing, “2” denotes the size series (width series 0, diameter series 2), “08” indicates a 40mm bore diameter ( 08 x 5 = 40), and “C3” indicates radial clearance group 3 (greater than basic clearance). Another example is “7310B/P5,” in which “7” represents an angular contact ball bearing, “3” denotes the size series (width series 0, diameter series 3), “10” denotes a 50mm bore diameter, “B” indicates a 40° contact angle, and “P5” indicates tolerance grade 5. These designations allow engineers to quickly understand key information such as bearing type, size, accuracy, and clearance, providing an accurate basis for bearing selection and application. As bearing technology advances, new designations and meanings continue to emerge, so it’s important to stay updated with standard updates to ensure accurate understanding of the designations.
