Guide to Hex Bolt Dimensions for Engineering Projects

Selecting the correct metric hex bolt dimensions is crucial for any engineering project. This comprehensive reference provides detailed specifications to ensure proper bolt selection and prevent installation issues.

Hex bolts serve as critical fastening components in mechanical assemblies. Incorrect dimensions can lead to structural weaknesses, joint failures, or safety hazards. Precise measurements ensure proper load distribution and connection integrity.

• Nominal Size (D): The bolt's designated diameter (e.g., M10 indicates 10mm diameter)
• Body Diameter: Shaft dimensions including maximum (D MAX) and minimum (D MIN) tolerances
• Head Thickness: Height measurements (H MAX/H MIN) affecting torque capacity and clearance
• Across Flats: Wrench size requirements (F MAX/F MIN) for installation
• Across Corners: Diagonal measurements (C MAX/C MIN) indicating head strength

When specifying hex bolts, engineers should evaluate these additional factors:

• Material Composition: Carbon steel, alloy steel, and stainless steel offer different strength and corrosion resistance properties
• Strength Classifications: Standard ratings include 4.8, 8.8, 10.9, and 12.9 grades indicating tensile strength
• Surface Treatments: Zinc plating, nickel coating, or Dacromet finishes provide environmental protection

1. Verify all dimensional requirements against mating components
2. Cross-reference torque specifications with bolt size and material
3. Confirm thread pitch compatibility with nuts or threaded holes
4. Validate environmental suitability of selected materials and coatings

Proper bolt selection requires careful consideration of dimensional specifications combined with material properties and application requirements. This reference provides the fundamental data needed for initial sizing decisions in mechanical design projects.