Thread Rolling
Overview of Thread Rolling
Thread rolling forms threads, gear teeth, and similar profiles by applying pressure to the material and deforming it plastically. Dedicated tools (rolling dies or rolls) press continuously on the metal to form the shape. The result is a highly accurate profile with greater strength and durability than a cut thread.
Types of Thread Rolling
- Flat-die rolling: The part is rolled between flat dies. Widely used for small parts such as screws, it is fast and highly accurate.
- Cylindrical-die rolling: The part is rolled between round dies. Suited to hollow bolts and similar parts; productivity is lower than the other two types.
- Rotary (planetary) die rolling: The part rotates against a cylindrical die. It handles medium to large parts and applies high torque to form accurate threads and grooves.
The Thread Rolling Process
Thread rolling generally follows these steps.
- Material preparation: The material is normally supplied as bar or wire and prepared to the correct size and shape. At Yamaguchi Nut, all blanks are cold headed before rolling.
- Die setup: The dies are set up for the shape and size to be produced. The type and profile of the die depend on the form and dimensions required.
- Rolling: The dies or rolls apply continuous pressure and the material deforms to take on the die profile.
- Cooling and lubrication: Because pressure and friction are high, rolling oil is generally used. It prevents overheating of the dies and material and maintains rolling quality.
- Finishing and inspection: After rolling, parts receive finishing or surface treatment as required and are inspected to confirm that dimensions and form meet the specification.
Advantages of Thread Rolling
- Stronger parts: Because the thread is formed under pressure, the grain flows with the profile, increasing strength and durability. Rolled threads are roughly 30–40% stronger than cut threads.
- Superior surface finish: Since no material is cut away, the rolled surface is smooth and precise. Lower wear and friction extend product life.
- Less material waste: Unlike cutting, rolling deforms the material rather than removing it, so little is wasted.
- Well suited to volume production: Fast, efficient forming makes it ideal for high volumes. It is widely used for automotive and aircraft components.
- Environmentally friendly :No chips are produced, so waste is minimal.
Key Points in Thread Rolling
Thread rolling has many advantages, but several points must be managed to ensure accuracy and quality.
- Material selection: Because the material is deformed under pressure, its hardness and ductility must be suitable for rolling. Material that is too hard is difficult to roll and accelerates die wear.
- Tool wear management: Dies and rolls wear under the high pressure and need regular maintenance. As wear progresses, accuracy falls and product quality suffers, so proper upkeep is essential.
- Rolling speed: Excessive speed can harm material quality and tool life, so an appropriate rolling speed is recommended.
- Rolling oil: A suitable lubricant reduces friction and preserves the surface quality of both the part and the tool.
Typical Applications of Thread Rolling (industry-wide)
Thread rolling is used especially in the following fields.
- Automotive parts: Engine components, gears, shafts, screws, and more.
- Aerospace: Parts that must combine high strength and durability.
- Precision instruments: Watch and camera components and small parts for electronics.
- Construction bolts and screws: Bolts and screws that require strength and durability.