Thread Rolling: Chipless Thread Forming By Plastic Deformation

In the pursuit of high efficiency and high quality in large-scale production, a thread processing method that does not require cutting demonstrates significant advantages: Thread Rolling, which belongs to the "Material Forming Method".

1. What is Thread Rolling?

Thread rolling is a chipless processing technique. It utilizes forming rolling dies to apply pressure to the workpiece surface, causing plastic deformation, thereby extruding threads that match the shape of the dies. In essence, it does not "cut" the threads but "squeezes" them out.

2. Working Principle and Equipment

Working Principle: Hardened rolling dies (thread rollers or dies) are pressed against a cylindrical blank. The metal of the blank flows plastically under the pressure, causing the fibers to deform continuously and form the thread profile.

Common Equipment: Thread rolling machines, thread forming machines, or automatic lathes equipped with self-opening and closing thread rolling heads.

3. Process Characteristics and Capabilities

• Processing Range: Primarily used for producing external threads. The external diameter generally does not exceed 25 mm, and the length is usually not more than 100 mm. Thread accuracy can be as high as Grade 2.
• Blank Requirement: The diameter of the blank must be precisely calculated and is approximately equal to the pitch diameter of the thread to be formed.
• Internal Thread Rolling: Traditional rolling cannot process internal threads. However, for workpieces made of softer materials, internal threads can be cold-formed using fluteless taps (maximum diameter about 30 mm). Its working principle is similar to tapping but requires higher torque.

4. Five Core Advantages of Thread Rolling

• Excellent Surface Quality: The surface roughness of rolled threads is far superior to that achieved by turning, milling, or grinding. The surface is smooth and has a burnished effect.
• Higher Strength and Hardness: Due to cold working induced during the process, the fatigue strength and surface hardness of the threads are significantly improved.
• 100% Material Utilization: The entire process generates no chips, saving material.
• Extremely High Production Efficiency: The processing speed is very fast, typically several times that of cutting methods, and it is easily automated.
• Long Die Life: Rolling dies have high wear resistance and a very long service life.
•  Limitations
• Despite its prominent advantages, thread rolling has certain applicable ranges:
• The hardness of the workpiece material typically should not exceed HRC 40.
• Requirements for the dimensional accuracy and hardness consistency of the blank are very strict.
• Manufacturing high-precision and high-hardness rolling dies is relatively difficult itself.
• It is not suitable for processing threads with asymmetric profiles.