Method for making rolling bearings DD ferrule forming method
September 12 01:25:16, 2025
Do you know how a rolling bearing is made? Of course, there are many types of rolling bearings, and each has different structural designs, tolerances, materials, and manufacturing processes. However, the basic production process generally includes several key steps: manufacturing of bearing components, reverse processing of parts, assembly of the bearing, quality inspection, demagnetization, cleaning, oiling, packaging, and finally, storage in the warehouse.
The inner and outer rings (ferrules) are the main components of a rolling bearing. Because there are so many types of bearings, the size, structure, equipment, and processing methods for the ferrules vary. Moreover, since the processing of ferrules involves multiple steps and requires high precision, the quality of this part significantly affects the accuracy, lifespan, and performance of the entire bearing.
The raw materials used for the ferrules are typically cylindrical bars or tubes. Depending on the forming process, the general production procedures for rolling bearing ferrules include the following:
1) For bar material: blanking, casting, annealing (or normalizing), turning (cold forming), heat treatment (quenching and tempering), grinding, and reverse processing.
2) For bar or tube material: cutting, cold heading, heat treatment (quenching and tempering), grinding, and reverse processing.
3) For pipe material: cutting, turning, heat treatment (quenching and tempering), grinding, and reverse processing.
4) For bar material: cutting, cold (or warm) forging, turning, heat treatment (quenching and tempering), grinding, and reverse processing.
In the past, common forming methods for ferrules included forging, turning, cold pressing, and cold (or warm) forging. Among these, forging was the most widely used, accounting for about 80% of total output. For some small, general-purpose bearings, rod or tube materials could be directly machined.
Since the 1980s, some Chinese companies have started using cold rolling and cold (or warm) forging techniques for small to medium-sized ferrules.
1) Forging forming helps eliminate casting defects, improves metal structure, ensures reasonable flow lines, and increases density. This method is widely used across various bearing sizes, from small bearings with an inner diameter of ~20mm up to large ones with an outer diameter of 5000mm. Common forging methods include hot forging, cold forging, and warm forging, with hot forging being most commonly used in China.
Hot forging can be further divided into free forging, press forging, flat forging, and high-speed upsetting based on the equipment used.
2) Cold heading and cold rolling are chipless processes that improve material utilization and metal flow. In theory, cold-formed parts can go directly to heat treatment and grinding without machining. These methods are mainly used for medium and small deep groove ball bearings. The process typically involves: casting blanks (rings) – turning (excluding the raceway) – rolling expansion (groove and chamfer) – full-diameter soft grinding. The accuracy of the final product depends on both the machine tool and the die.
3) Traditional turning involves special lathes and is completed through a series of operations. However, due to the difficulty in adjusting the equipment and low material efficiency, this method is gradually being replaced.
With technological advancements, CNC lathes have become more precise and widely used. As a result, complex-shaped, high-precision parts increasingly rely on CNC turning technology.
In summary, the trend in ferrule forming is moving toward higher material utilization, greater production efficiency, and improved molding precision. Therefore, high-speed upset forging, cold rolling, and CNC turning technologies will be used more extensively in the future.
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