JIS B 1180 Hexagon Head Bolt Specifications & Dimensions Reference Guide
Complete engineering reference for JIS B 1180 metric hexagon head bolts: width across flats (s), wrench clearances, ISO 4014 / DIN 931 cross-reference, and torque specs.
Standard Scope
Specifies the dimensional characteristics, thread tolerances, material property classes, and wrench clearance envelopes for metric hexagon head steel bolts (M3 to M36) per Japanese Industrial Standards (JIS). JIS B 1180 serves as the authoritative manufacturing and assembly standard for industrial machinery, automotive equipment, and tooling originating in Japan.
Typical Applications
- •Industrial assembly layout and wrench/socket clearance sizing for Japanese imported machinery.
- •Fastener interchangeability audits between JIS B 1180, ISO 4014 / ISO 4017, and DIN 931 / DIN 933 standards.
- •Precision metric bolting design in machine tools, robotic actuators, and automotive drivetrains.
- •Preload and tightening torque calculations with the [Bolt Torque Calculator](/calculators/bolt-torque).
Key Engineering Concepts
Width Across Flats (s)
The outer head width determining the wrench, spanner, or socket size required for assembly.
JIS vs ISO/DIN Width Differences
Notable dimensional deviations occur on common metric sizes: M8 (12 mm or 13 mm in JIS vs 13 mm in ISO), M10 (14 mm across flats in JIS vs 16 mm in ISO / 17 mm in DIN), M12 (17 mm across flats in JIS vs 18 mm in ISO / 19 mm in DIN), and M14 (21 mm in JIS vs 21 mm in ISO / 22 mm in DIN).
Property Classes
Conforms to metric mechanical strength grades per ISO 898-1 / JIS B 1051, primarily Class 4.8, 8.8, 10.9, and 12.9.
Thread Pitch Series
Standard coarse metric pitch series is standard, with selected fine pitch variants defined for precision automotive fastening.
Wrench Clearance Envelope
Minimum radial and axial clearance required around the bolt head to seat standard socket tooling without galling surrounding counterbores.
Engineering Notes & Best Practices
- •Tooling Interference: Always verify socket wall thickness when replacing DIN/ISO fasteners with JIS B 1180 bolts in recessed counterbores, as the smaller JIS width across flats (e.g. 14 mm vs 17 mm for M10) requires different socket dimensions.
- •Preload and Torque Calculation: Tightening torque must be evaluated using the nut-factor method ($T = K \cdot F_i \cdot d$) per VDI 2230, available on our [Bolt Torque Calculator](/calculators/bolt-torque).
- •Thread Engagement Safety: Minimum thread engagement length in tapped holes must exceed $1.0 d$ for steel, $1.5 d$ for cast iron, and $2.0 d$ for aluminum; verify shear pull-out with our [Thread Strip Strength Calculator](/calculators/thread-strip-strength).
- •Preload Guidelines: For detailed tightening mechanics, consult our comprehensive [Bolt Preload Explained](/knowledge/articles/bolt-preload-explained) engineering guide.
Official Standards Reference
Hexagon head bolts
Japanese Industrial Standards Committee (JISC) detailing dimensions, metric threads, and properties
Hexagon head bolts — Product grades A and B
International Organization for Standardization reference standard
Systematic calculation of high-duty bolted joints
Verein Deutscher Ingenieure systematic bolted joint guidelines