Jis B 1188 Pdf !link! May 2026

You can obtain the official, full-text technical documentation through several authorized standards distributors: JIS B1188 Double Washer Sems

The standard specifies that the pan head's diameter and height are slightly smaller than a standard DIN or ISO pan head, making them ideal for compact electronics. Technical Benefits & Applications jis b 1188 pdf

The standard covers both steel and brass screws intended for general-purpose applications. The most common configuration is a machine screw combined with one or two captive washers. Standard Specifications Material Carbon steel (Class 4.8), Stainless steel (A2), and Brass Head Type Pan Head (Small pan head is 5%–20% smaller than standard) Washer Types Standard Specifications Material Carbon steel (Class 4

The helical split lock washer provides constant tension to prevent the screw from loosening under mechanical stress. Core Specifications of JIS B 1188

JIS B 1188 is often categorized into specific types based on the washer assembly:

The standard defines the specifications for cross-recessed head screws with captive washers , commonly known in the industry as "Sems" screws. These specialized fasteners feature pre-assembled washers that are mounted onto the screw blank before the threads are rolled, ensuring the washers remain permanently attached and free-spinning. Core Specifications of JIS B 1188