Hex bolts are one of the most widely used fasteners in industrial engineering, valued for their high tensile strength and versatility in connecting structural elements. Whether used in construction, machinery, or infrastructure projects, understanding the correct dimensions, standards, and applications of hex bolts is essential for procurement managers and engineers to ensure optimal performance and compliance. This comprehensive guide provides everything you need to know about hex bolts to support informed sourcing and specification.

What Are Hex Bolts?

Hex bolts, also known as hex cap screws or hex head bolts, feature a six-sided (hexagonal) head and a partially or fully threaded shank. They are primarily used to fasten two or more components together, either with a nut or directly into a tapped hole. Hex bolts offer superior clamping force and are designed for high-load applications.

Key Features of Hex Bolts

• Head shape: Six-sided hex head allows easy wrenching

• Thread type: Coarse or fine threading depending on application

• Shank: Can be partially threaded (for shear strength) or fully threaded (for clamping)

Hex Bolts Dimensions and Sizes

Accurate dimensioning ensures compatibility and performance. Hex bolts dimensions typically include:

• Diameter (d): Nominal size (e.g., M6, M12, 1/2 inch)

• Thread pitch (P): Distance between threads (fine or coarse)

• Length (L): From under head to tip

• Head width (A/F): Across flats — wrench size required

• Head height (k): Thickness of the head

Common Metric Hex Bolt Sizes (ISO 4014 / ISO 4017)

Common Inch Hex Bolt Sizes (ASME B18.2.1)

International Standards for Hex Bolts

Metric Standards

• ISO 4014 — Hex bolts (partially threaded)

• ISO 4017 — Hex bolts (fully threaded)

• DIN 931 / DIN 933 — German equivalents of ISO standards

• ISO 898-1 — Mechanical properties of carbon steel bolts (Grade 8.8, 10.9, etc.)

• ISO 3506 — Stainless steel mechanical properties (A2-70, A4-80, etc.)

Inch Standards

• ASME B18.2.1 — Dimensions for hex bolts (inch series)

• ASTM A307 — Carbon steel hex bolts (Grades A & B)

• ASTM A325 / A490 — High-strength structural bolts

• ASTM F593 — Stainless steel bolts

Material Options and Mechanical Properties

Selecting the right material ensures durability and load-bearing capacity.

Carbon Steel

• Grades 4.6, 8.8, 10.9, 12.9 (ISO 898-1)

• Applications: General engineering, structural steelwork

Stainless Steel

• A2 (304) and A4 (316) grades (ISO 3506)

• Applications: Corrosive environments, water treatment, marine

Alloy Steel

• ASTM A325, ASTM A490 high-strength bolts

• Applications: Heavy machinery, bridges, wind turbines

Hot-Dip Galvanized

• Corrosion-resistant coating for outdoor use

• Applications: Infrastructure, transmission towers

Key Applications of Hex Bolts in Industry

1. Construction and Structural Steel

• Steel frameworks, bridges, tunnels, and infrastructure projects

• Preferred standards: ISO 4014, ASTM A325

2. Machinery and Equipment Assembly

• Manufacturing equipment, industrial machinery, conveyors

• Preferred standards: ISO 4017, ISO 898-1 (Grade 8.8, 10.9)

3. Oil & Gas and Offshore Installations

• Pipeline flanges, subsea equipment, offshore platforms

• Preferred material: A4-80 stainless steel or Duplex stainless steel

4. Renewable Energy Projects

• Wind turbine towers, solar mounting systems, hydroelectric plants

• Preferred standards: ISO 4017, ISO 3506 (A4 grade)

5. Water Treatment and Marine

• Desalination plants, wastewater treatment, shipbuilding

• Preferred material: A4-80 (316 stainless steel)

How to Specify Hex Bolts for Your Project

To ensure you procure the correct hex bolts, specify:

• Diameter and length (e.g., M12 × 80 mm)

• Thread type (coarse/fine, fully/partially threaded)

• Material and grade (e.g., A4-80, Grade 10.9)

• Surface finish (plain, zinc plated, hot-dip galvanized)

• Compliance with standards (ISO, ASTM)

Conclusion

Hex bolts play a critical role in ensuring structural stability and operational reliability in industrial projects. By understanding their dimensions, standards, materials, and applications, procurement managers can make confident decisions that meet both technical and regulatory requirements.

For high-quality hex bolts compliant with international standards, contact IIIBEAR Intelligent Technology Co., Ltd. — our team is ready to support your industrial fastener needs.