Thread Rolling and Its Characteristics

**Thread Rolling and Its Characteristics: Practical! No Need to Search for Information Every Time**

Bolts and screws are the most widely used and mass-produced external threaded fasteners. The most common processing methods for these fasteners are generally rolling and cutting.

The most commonly used cutting methods include turning, milling, and threading. Among these, turning threads is the easiest to achieve, highly efficient, and suitable for processing fasteners of various materials, specifications, and precision levels.

However, since cutting involves removing excess material to form the thread profile, the metal flow lines are interrupted during the process. As a result, the threads produced often lack high strength and have limited fatigue life. Therefore, this method is not suitable for high-volume, high-performance aerospace external threaded fasteners.

The most commonly used thread processing method for aerospace bolts and screws is rolling, which is extensively applied to high-strength fasteners. In relevant aerospace fastener standards, high-strength bolts are typically required to have rolled threads.

The purpose of rolling is to redistribute the metal material along the thread profile, ensuring that the metal flow lines remain uninterrupted and reach maximum density at the thread root (as shown in Figure 2). This significantly enhances the tensile strength and fatigue fracture resistance of threaded fasteners.

At the same time, thread rolling is also one of the most efficient methods for thread processing. Therefore, in practical production, the rolling method is the most widely used.

The principle of thread rolling involves using rolling dies or rolling plates to plastically deform the workpiece, causing the metal material to flow and form threads through extrusion. This method not only improves the strength of the threads but also enhances surface quality and reduces stress concentration.

The main characteristics of rolled threads include:

1. **High Strength**: Since the metal flow lines remain uninterrupted, the strength and fatigue life of the threads are significantly improved.

2. **High Efficiency**: Thread rolling is a fast processing method, making it suitable for mass production.

3. **Excellent Surface Quality**: Rolled threads have a smooth surface, reducing friction and wear.

4. **High Material Utilization**: The rolling process generates almost no waste, with material utilization approaching 100%.

In practical applications, the primary equipment for thread rolling includes thread rolling machines and rolling plates. Thread rolling machines are suitable for mass production, while rolling plates are used for small batches or special thread specifications.

The processing parameters for thread rolling include rolling pressure, rolling speed, and the number of rolling passes. The selection of these parameters directly affects the quality and performance of the threads. Therefore, in actual production, optimization and adjustment are necessary based on the specific materials and specifications.

In summary, thread rolling, as an efficient and high-quality processing method, is widely used in industries such as aerospace, automotive, and mechanical manufacturing. By selecting appropriate processing equipment and parameters, high-strength threaded fasteners that meet various performance requirements can be produced.