JIS B 1189 Hexagon Flange Bolts

JIS B 1189 Hexagon Flange Bolts are metric bolts with a hexagon head and an integral flange beneath the head. The flange acts as a built-in bearing surface, increasing the contact area under the bolt head compared with a conventional hexagon bolt.

This allows the bolt to be used without a separate flat washer in applications where the flange geometry and bearing area meet the assembly requirements.

JIS B 1189 is the Japanese standard for hexagon bolts with flange and is currently an active standard. The 2014 revision was developed in correspondence with ISO 15071 for coarse-thread flange bolts and ISO 15072 for metric fine-pitch flange bolts, with additional Japanese-specific requirements included in the standard.

The standard covers both coarse-thread and fine-pitch configurations. In the Japanese-specific Annex JA, flange bolts are further divided into Type 1, with a flat flange upper surface, and Type 2, with a tapered flange upper surface. These legacy Japanese configurations should be distinguished from the ISO-aligned product specifications in the main body of the current standard.

JIS B 1189 flange bolts are commonly used in automotive components, machinery, industrial equipment, fabricated assemblies, and other applications where a larger integrated bearing surface is preferred.

They are commonly specified by thread diameter, length, thread pitch, strength class, material, surface treatment, and any required flange configuration.