What Are Hex Bolts?
Hex bolts, commonly known as hexagon head bolts or hex cap screws, are one of the most widely used fastener types in construction, machinery, and various industrial applications. These bolts feature a six-sided hexagonal head that allows for easy tightening with a wrench or socket. The threaded shaft provides secure fastening when used with a nut or in a tapped hole.
Hex bolts are designed to join two or more components together securely, offering excellent load-bearing capacity and resistance to loosening. Their standardized design makes them versatile for countless applications across industries.
Types of Hex Bolts
Hex bolts come in several variations to suit different applications:
- Fully Threaded Hex Bolts – Threads run the entire length of the bolt shaft
- Partially Threaded Hex Bolts – Feature an unthreaded portion near the head
- Heavy Hex Bolts – Have larger, thicker heads for higher torque applications
- Flange Hex Bolts – Incorporate a flange beneath the head to distribute load
- Tap End Hex Bolts – Designed to cut their own threads in pre-drilled holes
- Metric Hex Bolts – Manufactured to metric dimensions and thread pitches
- Inch Hex Bolts – Made to imperial measurement standards
Key Features of Hex Bolts
Hex bolts offer several distinctive characteristics:
- Hexagonal head for easy wrench or socket application
- Durable construction from various materials (see below)
- Precise threading for secure fastening
- Standardized dimensions for interchangeability
- High strength grades for different load requirements
- Multiple finishes for corrosion resistance
Applications of Hex Bolts
Hex bolts are used in virtually every industry:
- Construction – Structural steel connections, framing
- Automotive – Engine components, chassis assembly
- Machinery – Equipment assembly, maintenance
- Infrastructure – Bridges, towers, rail systems
- Manufacturing – Production line equipment
- DIY Projects – Home repairs, furniture assembly
How Hex Bolts Work
Hex bolts function by creating a clamping force between joined materials. When the bolt is tightened:
- The bolt passes through aligned holes in the materials being joined
- A nut is threaded onto the bolt’s end (or threads into a tapped hole)
- As the head and nut are tightened, they compress the materials together
- The bolt’s shank resists shear forces, while tension in the bolt maintains the clamp
The hexagonal head provides multiple contact points for tools, allowing high torque application without slipping.
Hex Bolt Materials
Hex bolts are manufactured from various materials to suit different environments and strength requirements:
- Carbon Steel – Most common, economical, good strength
- Alloy Steel – Higher strength for demanding applications
- Stainless Steel – Excellent corrosion resistance (grades 304, 316)
- Brass – Corrosion resistant, decorative, non-magnetic
- Titanium – High strength-to-weight ratio, corrosion resistant
- Aluminum – Lightweight, moderate strength, corrosion resistant
Hex Bolt Size Charts
Standard Hex Bolt Dimensions (Metric)
| Diameter (mm) | Head Width (mm) | Head Height (mm) | Thread Pitch (mm) |
| M6 | 10 | 4 | 1 |
| M8 | 13 | 5 | 1.25 |
| M10 | 16 | 6 | 1.5 |
| M12 | 18 | 7 | 1.75 |
| M16 | 24 | 10 | 2 |
| M20 | 30 | 12 | 2.5 |
DIN 933 Hex Bolt Dimensions (Full Thread)
| Diameter (mm) | Head Width (mm) | Head Height (mm) | Thread Length (mm) |
| M4 | 7 | 2.8 | Full |
| M5 | 8 | 3.5 | Full |
| M6 | 10 | 4 | Full |
| M8 | 13 | 5 | Full |
| M10 | 16 | 6 | Full |
| M12 | 18 | 7 | Full |
Note: Dimensions may vary slightly by manufacturer and standard. Always consult specific product specifications for critical applications.
Hex bolts remain one of the most reliable and versatile fastening solutions available, offering strength, durability, and ease of use across countless applications. Understanding their types, materials, and proper sizing ensures optimal performance in any project.
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