From everyday items to automobiles, aircraft, and buildings, screws are indispensable components across all industries. Though they may seem like small parts, their role is significant—they affect product safety and durability. Screw manufacturing involves multiple processes and advanced technologies, making it a complex and highly important operation.

The quality of a screw largely depends on the materials selected. Common materials include steel, stainless steel, and brass. Steel is strong and widely used for general applications. Stainless steel offers excellent corrosion resistance and is ideal for humid or outdoor environments. Brass is highly workable and often used for decorative purposes. Choosing the appropriate material based on environment, required strength, and durability allows screws to perform optimally and ensures long-term safety.

Screw manufacturing begins with material selection and proceeds through various stages—heading, thread rolling, heat treatment, and surface treatment. Each stage plays a crucial role in determining the final quality of the screw.

The heading process forms the head of the screw. First, wire is cut to the necessary length, then a press called a header machine applies pressure via a die to shape the head. There are two types: cold heading (performed at room temperature and suitable for mass production) and hot heading (using heated material to enable more complex shapes).

Header machines perform automated sequences including cutting, forming, and ejecting. The die is a critical tool that defines the screw’s head shape and requires high precision.

Key quality control points in this process include temperature and pressure regulation. Poor temperature control may lead to cracking or deformation. Insufficient pressure can result in irregular head shapes. Skilled technicians carefully operate machinery to maintain strict quality management.

Thread rolling creates the threads on the screw blanks formed in the heading process. Using tools called thread rolling dies, threads are formed by pressing the blanks while rotating them. Compared to cutting, thread rolling results in stronger threads and higher production efficiency.

Common machines include flat-die and cylindrical-die rolling machines. Flat-die machines press the blank between two flat dies using a reciprocating motion. Cylindrical-die machines use rotating round dies for continuous thread formation.

Important quality control points include pressure and speed settings. Excessive pressure can crush threads or crack the material; insufficient pressure may produce incomplete threads. High speed may reduce thread accuracy. Optimal settings are used to maintain stable quality.

Heat treatment enhances the strength and toughness of screws. Common techniques include quenching and tempering, selected based on material and application. Quenching involves heating the material and rapidly cooling it to increase hardness. Tempering reheats the hardened material to improve ductility and toughness.

Heat treatment greatly affects screw performance, especially for high-strength bolts and tapping screws, where precise control is essential.

Quality control focuses on managing temperature and time. Too high a temperature or prolonged exposure may alter the material, while too low a temperature or short duration may result in inadequate treatment. Precision temperature control systems and strict time monitoring are essential.

Surface treatment improves a screw’s resistance to corrosion and wear. Common methods include plating and painting. Plating forms a thin metallic film on the surface for enhanced corrosion resistance. Painting applies protective and decorative coatings.

Since corrosion and abrasion resistance greatly depend on surface treatment, the appropriate method must be selected based on the intended environment. For example, screws used outdoors often receive high-corrosion-resistant plating.

Key quality control points include uniformity and coating thickness. Uneven coating may cause localized corrosion or rapid wear. Too thin a coating may be ineffective, while too thick a coating can easily peel. Uniform application and proper thickness control are essential.

There are many different types of screws, each with manufacturing processes tailored to their specific applications and operating environments. Here, we will look at three representative types—wood screws, high-strength bolts, and stainless steel screws—and explain how their production processes differ.

Wood screws are used for fastening into wood. They are characterized by deep threads and sharp tips, which allow them to bite into wood and hold securely. Their manufacturing process is relatively simple compared to other screws: the head is formed in the heading process, threads are rolled, and surface treatment is applied. Heat treatment is generally omitted.

High-strength bolts are used in structural applications such as buildings and bridges. Their manufacturing requires strict quality control to ensure strength. Materials such as chromium-molybdenum steel (a special alloy steel) are used. Both heading and rolling processes must meet high precision and consistency standards. Heat treatment is essential—quenching and tempering are applied to achieve the necessary strength and toughness.

Stainless steel screws offer excellent corrosion resistance and are used in wet or outdoor environments. Since stainless steel tends to harden during processing, special attention is needed during manufacturing. Intermediate annealing may be added between heading and rolling to prevent cracking due to excessive work hardening. The optimal production method may vary depending on the grade of stainless steel used.

As shown, the manufacturing process varies based on screw type, with each adapted to meet the required performance and application conditions.

In screw manufacturing, quality control and environmental stewardship are essential for enhancing product reliability and contributing to a sustainable society.

Screw quality is maintained through rigorous quality control at every stage—from material inspection to heading, rolling, heat treatment, and surface treatment. At each stage, dimensions, shape, hardness, and surface condition are inspected. For example, in the heading process, regular maintenance and replacement of dies ensure dimensional accuracy. In rolling, the thread shape and pitch are measured to confirm compliance with specifications. In heat treatment, precise temperature control ensures uniform hardness. In surface treatment, coating thickness and adhesion are checked to guarantee corrosion and wear resistance.

In the final inspection stage, screws are thoroughly checked for dimensions, strength, and appearance. Dimensional inspections use tools like calipers and micrometers to ensure tolerances are met. Strength tests—such as tensile and torsion tests—confirm that required specifications are achieved. Visual inspections check for defects such as scratches or deformation. Only screws that pass all these tests proceed to the next stage. Supplying products compliant with standards such as ISO and JIS is essential for guaranteeing screw quality.

Various initiatives are being taken in screw manufacturing to reduce environmental impact. For example, chips from cutting processes are recycled to make effective use of resources. Energy-saving furnaces are used in heat treatment to reduce CO₂ emissions. Wastewater treatment is strictly managed in surface treatment to minimize pollution. There is also a growing adoption of environmentally friendly materials and surface treatments. Thanks to these efforts, screw manufacturing is evolving into a more sustainable industry.

The manufacturing of screws involves many processes—from material selection to final shipment. In each stage, both quality control and environmental awareness are essential, supporting the reliability and performance of the final product.

In recent years, advances in technologies such as AI and IoT have promoted automation and efficiency in manufacturing processes. These innovations are expected to improve productivity and stabilize quality. Additionally, developing sustainable manufacturing methods to reduce environmental impact has become increasingly important.

Screws are critical components that support our daily lives. Their production involves deep expertise and dedicated craftsmanship. We hope this article helps deepen your understanding of how screws are made.