: Since the washers are captive, they cannot be forgotten or lost during maintenance.
The German standard for screw and washer assemblies. DIN 6900 components can sometimes replace JIS B 1188 parts, but you must verify the flat washer outer diameter ( ) and thickness ( ) to ensure clearance in recessed pockets.
View detailed dimension tables for pan head machine screws with double washers (split lock and flat) on the ITP Bolt Specification Sheet .
It is important to note that while the official standard is copyrighted and not freely distributable, many technical resources provide sufficient detail for engineering research without the need to purchase the full document. jis b 1188 pdf
Search terms like "JIS B 1188 manufacturer catalog PDF" will often yield detailed technical catalogs with the engineering tables you need without requiring a paid subscription. Conclusion
Robotic arm assembly systems handle integrated SEMS screws much more reliably than loose screws and washers. Common Applications of JIS B 1188 Fasteners
JIS B 1188 is a Japanese Industrial Standard that specifies the dimensions, materials, and testing requirements for socket head cap screws. The standard covers a wide range of screws, including those with a socket head, a cylindrical body, and a threaded portion. These screws are commonly used in various industries, including automotive, aerospace, and construction. : Since the washers are captive, they cannot
The Significance and Technical Standards of JIS B 1188 In the world of precision engineering and manufacturing, standardized fasteners are the silent backbone of structural integrity. One such standard, JIS B 1188 , established by the Japanese Industrial Standards Committee (JISC) , defines the specifications for cross-recessed head screws with captive washers—commonly known as "Sems" screws. This standard is vital for industries that require high-speed assembly and reliable vibration resistance, particularly in the electronics and automotive sectors.
The current active version is (published March 21, 2017), superseding the 1995 version.
JIS B 1188 is a Japanese Industrial Standard that specifies the requirements for . In simple terms, it defines "SEMS screws"—fasteners that come with a washer already assembled, which is designed so it cannot detach. According to the standard’s official terminology, these are formally described as steel and brass cross recessed head screws with captive washer for general purposes (English) or 座金組込み十字穴付き小ねじ (Japanese). Unlike a standard screw and washer combination, the washer in a JIS B 1188-compliant part is mechanically secured during the manufacturing process, which significantly enhances assembly efficiency and safety. View detailed dimension tables for pan head machine
These variations allow engineers to select the optimal fastener for specific applications, based on the desired balance between load distribution, vibration resistance, and material thickness. Standardized types, such as (ISO flat washer) and I=3 (spring washer + flat washer), are the most widely available and commonly recommended.
JIS B 1188 specifies the characteristics, dimensions, and tolerances for cross-recessed screws pre-assembled with plain and/or spring lock washers. The fundamental design mechanism ensures that the washers are trapped permanently on the screw blank before the threads are rolled. Once the threads are formed, the outer diameter of the thread becomes larger than the inner diameter of the washer, preventing the washer from falling off. Key Benefits of JIS B 1188 Assemblies