Method for making rolling bearings DD ferrule forming method
September 12 01:15:21, 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 methods. However, the basic production process typically 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 most critical parts of a rolling bearing. Due to the variety of bearing types, the size, structure, equipment, and process methods for the ferrules vary significantly. Since the manufacturing of ferrules involves many complex steps and requires high precision, the quality of the ferrule directly affects the accuracy, performance, and service life of the entire bearing.
Ferrules are usually made from cylindrical bars or tubes. Depending on the type of bearing and its size, the production process may differ. Common methods include:
1) Bar material: blanking, casting, annealing (or normalizing), turning (cold forming), heat treatment (quenching and tempering), grinding, and part reversal.
2) Bar or tube material: cutting, cold heading, heat treatment, grinding, and part reversal.
3) Pipe material: cutting, turning, heat treatment, grinding, and part reversal.
4) Bar material: cutting, cold (or warm) forging, turning, heat treatment, grinding, and part reversal.
At that time, the main forming methods for ferrules included forging, turning, cold pressing, and cold (or warm) forging. Among these, forging was the most widely used method, accounting for about 80% of total production. For smaller general-purpose bearings, rod or tube materials could be directly machined. In the 1980s, some Chinese companies began using cold rolling and cold (or warm) forging for small and medium-sized ferrules.
Forging is an effective method that eliminates casting defects, improves metal structure, ensures proper flow lines, and enhances density. It is used across a wide range of bearing sizes, from small ones with an inner diameter of 20mm up to large ones with an outer diameter of 5000mm. Common forging techniques include hot forging, cold forging, and warm forging, with hot forging being the most commonly used in China.
Hot forging can be further divided into free forging, press forging, flat forging, and high-speed upsetting, depending on the equipment used.
Cold heading and cold rolling are also important processes. Cold rolling is a chipless method that improves material utilization and achieves finer metal grain structures. In theory, cold-formed parts can go directly to heat treatment and grinding without machining. This method is mainly used for medium and small deep groove ball bearings, with a typical process including casting blanks, turning, expansion, chamfering, and soft grinding.
Traditional turning methods use special lathes, but they have been gradually replaced due to low efficiency, difficulty in adjustment, and poor material utilization. With technological advances, CNC lathes have become more popular, especially for complex shapes and high-precision requirements.
In summary, the trend in ferrule forming is moving toward higher material utilization, greater production efficiency, and improved molding accuracy. As a result, high-speed upset forging, cold rolling, and CNC turning technologies will continue to play a more significant role in the future.
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