Common die specification range and standard code
Dies, as tools for producing external threads, are widely used in machinery manufacturing, maintenance, and other fields. Their specification ranges and standard codes are crucial for ensuring consistency and interchangeability in thread production. Common die specifications are primarily categorized by thread diameter and pitch, and can be divided into three main categories: metric, imperial, and pipe thread dies. Metric thread dies typically range in diameter from M1.6 to M2, M3, M4, and up to M100 and even larger. Thread pitches vary, with coarse and fine pitches. For example, an M8 has a coarse pitch of 1.25mm, while fine pitches range from 1mm to 0.75mm. Imperial thread dies are measured in inches, with diameters typically expressed as 1/4-inch, 3/8-inch, and 1/2-inch. Pitch is expressed in threads per inch, such as 1/4-20, which indicates a thread with a 1/4-inch diameter and 20 threads per inch. Pipe thread dies are used to process threads for pipe connections. They are divided into non-thread-sealed pipe threads (such as G type) and thread-sealed pipe threads (such as R type). The specifications range from 1/8 inch to 4 inches to meet the connection needs of pipes of different diameters.
Die designations are a numbering system established by countries or industry organizations to standardize die production and use. These designations vary from country to country. Commonly used die designations in my country are primarily based on national (GB) standards. For example, GB/T 970.1-1994 specifies the dimensions and technical requirements for metric coarse-pitch thread dies, while GB/T 970.2-1994 governs metric fine-pitch thread dies. Internationally, standards developed by the International Organization for Standardization (ISO) are widely adopted, such as ISO 529-1983, “Threading Tool Dies – Dimensions and Designation,” which standardizes die form, dimensional tolerances, and materials. Furthermore, the American National Standards Institute (ANSI) has also developed corresponding die standards, such as ANSI B94.7-1984, while Europe has EN 2529. These standards not only clearly define die specifications but also provide detailed specifications for manufacturing materials, hardness, surface quality, and other technical indicators, providing a reliable basis for die production, inspection, and selection.
Metric thread dies are one of the most widely used types, with a clear correspondence between their specifications and standard codes, making them easy to find and select. Metric thread dies are typically denoted by “thread code x pitch.” For example, M10 x 1.5 represents a coarse thread die with a nominal diameter of 10mm and a pitch of 1.5mm, while M10 x 1 represents a fine thread die. According to GB/T 970.1 and GB/T 970.2, metric dies are categorized as round, square, and hexagonal. Round dies are the most commonly used, with their outer diameter varying depending on the thread diameter. For example, the outer diameter of an M6 round die is approximately 10mm, while that of an M12 round die is approximately 18mm. Dies are typically constructed from high-speed steel (such as W18Cr4V) or alloy tool steel (such as 9SiCr), with a hardness requirement of HRC 60-65 to ensure adequate wear resistance and long service life. In terms of marking, metric dies are usually marked with thread code, standard code and material code, such as “M8×1.25 GB/T 970.1 W18Cr4V”, which clearly reflects the key information of the die.
Imperial thread dies and pipe thread dies have unique specification ranges and standard designations, suited to specific threaded connection scenarios. Imperial thread die specifications are expressed in inches of the major thread diameter and the number of threads per inch. For example, 1/2-13 represents a 1/2-inch major diameter, 13 threads per inch, for a coarse thread (UNC), while 1/2-20 represents a fine thread (UNF). These designations primarily follow standards such as ANSI B94.7 and ISO 228. The die’s shape and dimensions are determined by the thread specifications, and the primary material used is high-speed steel. Among pipe thread dies, non-thread-sealing pipe thread dies (G-type) are used for pipe connections where sealing isn’t required. They range in size from G1/8 to G4, are standardized under GB/T 7307-2001 and correspond to ISO 228-1. Thread-sealing pipe thread dies (R-type) are used where sealing is required. They are available in tapered external threads (R) and cylindrical internal threads (Rp). Their specification range is similar to that of the G-type, and are standardized under GB/T 7306-2000 and correspond to ISO 7/1. Pipe thread dies have a 55° thread angle, which differs from the 60° thread angle of standard metric and imperial threads, so careful consideration is required when selecting these dies.
The correct selection of die specifications and standard codes is crucial to thread processing quality and requires comprehensive consideration based on the specific application scenario and technical requirements. When selecting a die, first determine the die type based on the thread type (metric, imperial, or pipe) of the part being processed. Then, select the appropriate specification based on the thread diameter and pitch, ensuring that the die specifications fully match the part requirements. Also, verify that the die standard code complies with relevant standards to ensure thread interchangeability. For example, for threading products intended for export, dies that comply with ISO standards or the standards of the importing country should be selected. Furthermore, the characteristics of the material being processed should be considered. For harder materials (such as stainless steel and high-strength alloys), dies made of high-speed steel or coated should be selected to improve cutting performance and service life. During use, die installation and operation should be carried out in accordance with the technical requirements of the die standard. Dies should be regularly inspected for wear and promptly replaced if excessively worn, to ensure that the processed threads meet dimensional accuracy and surface quality requirements. Proper die selection and use can effectively improve thread processing efficiency and quality, ensuring the reliability of mechanical connections.
