Japanese Industrial Standard – Complete detail to understand the Fastener System
The Japanese Industrial Standard (JIS) is a comprehensive set of national standards used for various industries and products in Japan. When it comes to fasteners—such as bolts, screws, nuts, and washers—the JIS defines specifications to ensure consistency, interchangeability, and quality in manufacturing. Below is a detailed overview to understand the JIS fastener system:
- JIS Standard Overview for Fasteners
Fasteners under JIS are standardized in terms of:
- Thread types and sizes
- Dimensions (length, diameter, pitch, etc.)
- Tolerances
- Material and strength requirements
- Surface finishes
- Markings and labeling
- Thread Standards
The JIS fastener system defines thread types primarily for bolts and screws, similar to international standards such as ISO (International Organization for Standardization) and DIN (Deutsches Institut für Normung).
- Metric Thread: The JIS predominantly uses metric threads, which are referred to as “M” (e.g., M10, M12, etc.). This system is based on the ISO metric thread standard.
- Coarse threads (e.g., M10x1.5): The most common form of threading.
- Fine threads (e.g., M10x1.25): Used where a higher strength or precision is required.
Thread Classes
- Class 1: Loose fit, used for ease of assembly.
- Class 2: Standard fit, used for most fasteners.
- Class 3: Tight fit, for high-precision applications.
- Types of Fasteners
JIS categorizes fasteners into different types. Some of the commonly used fasteners are:
- Bolts: Designed for use with nuts or tapped holes.
- Screws: Designed to be used without nuts, driving directly into materials.
- Nuts: Paired with bolts to hold materials together.
- Washers: Used with bolts and screws to distribute load.
Each type is designated with a JIS code for easy identification and classification.
Common JIS Fastener Codes:
- JIS B 0205: Tolerances for metric threads.
- JIS B 1111: Hexagon head bolts.
- JIS B 1112: Hexagon head screws.
- JIS B 1180: Mechanical properties of fasteners.
- JIS B 1256: General use washers.
- Material and Strength Classes
JIS fasteners come in various strength grades based on the material and intended application. This is indicated by a numerical strength class on the fastener (e.g., 4.8, 8.8, 12.9).
- Steel Fasteners: The numbers (e.g., 8.8) represent the strength and hardness of the material. The first number indicates the tensile strength (in hundreds of MPa), while the second number indicates the percentage of yield strength.
- 4.8: Standard mild steel fasteners.
- 8.8: Medium strength.
- 10.9 and 12.9: High-strength fasteners for heavy-duty applications.
- Stainless Steel Fasteners: Typically denoted with the series 300 or 400, referring to corrosion-resistant materials such as 304 or 316 stainless steel.
- Surface Treatments: The JIS also standardizes different coatings such as zinc plating, hot-dip galvanizing, and black oxide to protect fasteners from corrosion.
- Markings
JIS fasteners have specific markings that provide information about the fastener’s grade, material, and manufacturer:
- Bolt heads: Often marked with the strength grade.
- Nut faces: Marked with the strength grade, material code, or manufacturer’s initials.
- Dimensional Standards
Fasteners under JIS have precise dimensions for all features (e.g., head size, thread length, shaft diameter). This is to ensure interchangeability across different manufacturers.
For example:
- JIS B 1111: Specifies the dimensions for hexagon head bolts, including head height, head width, and thread length.
- JIS B 1180: Describes the dimensional tolerances for fasteners.
- Common JIS Fastener Standards
Here are some commonly referenced JIS standards for different fasteners:
- JIS B 1051: Strength classification of steel fasteners.
- JIS B 1176: Self-tapping screws.
- JIS B 1181: Hexagon socket head cap screws.
- JIS B 1186: Washers (including plain and spring washers).
- JIS B 1214: Rivets.
- Tolerances and Precision
Each fastener type has a tolerance range defined in the JIS standards. This ensures that fasteners fit correctly and provide the desired performance.
- Dimensional Tolerances: Tolerances are specified for the length, diameter, and other critical dimensions of fasteners.
- Thread Tolerances: Defined in JIS B 0205, which covers external and internal thread tolerances.
- Inspection and Testing
JIS standards include guidelines for the inspection and testing of fasteners:
- Hardness testing: For material verification.
- Tensile strength tests: To ensure the fastener meets the designated strength class.
- Dimensional inspection: To verify that the fastener meets the tolerance specifications.
- JIS vs. Other Standards
While JIS fasteners are widely used in Japan, they are often compatible with international standards such as:
- ISO standards: JIS fasteners are often aligned with ISO metric standards, though there are minor differences in tolerances and dimensions.
- DIN standards: German DIN fasteners are very similar to JIS, but with slight differences in head sizes and thread pitches.
- ANSI standards: American fasteners use imperial measurements, so JIS fasteners may not be interchangeable without modifications.
Conclusion
The JIS fastener system is essential for standardizing the production and use of fasteners in various industries, ensuring quality, reliability, and interchangeability. Understanding the different thread types, materials, strength grades, and inspection procedures defined by the JIS system helps in selecting the right fasteners for specific applications.
Here is an illustrative image showing key aspects of the Japanese Industrial Standards (JIS) for fasteners, including bolts, screws, nuts, washers, and relevant dimensions. It also highlights thread types and strength classifications. This representation mimics the technical style seen in engineering manuals.