Hexagon Bolts

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About Hexagon Bolts

Hexagon bolts, also known as hex bolts or hex head bolts, are among the most widely used fasteners in construction, engineering, and manufacturing applications. Characterised by their six-sided head and external thread, these versatile fasteners are designed to be driven with spanners or socket sets, providing secure, reliable connections for everything from structural steelwork to machinery assembly. The hexagonal head design offers superior grip and torque application compared to other bolt types, making them the preferred choice for applications requiring high clamping force and long-term stability.

Our range of Sirius hexagon bolts covers the most common specifications demanded by professionals across the UK. Available in various grades and finishes, including A2 304 and A4 316 stainless steel for corrosion resistance, as well as high tensile 8.8 and 10.9 grades in galvanised, zinc plated, and standard finishes, these bolts are engineered to meet exacting standards. Whether you're working on outdoor installations requiring weather resistance, structural projects demanding high load-bearing capacity, or marine environments needing superior corrosion protection, you'll find the appropriate specification within this category.

Hexagon bolts are typically used with nuts and washers to create strong mechanical joints, and are available in numerous thread sizes and lengths to suit different applications. The external threading extends along part of the shank, with the smooth portion beneath the head providing additional shear strength. This makes them ideal for applications where precision alignment and substantial holding power are essential requirements.

Jargon Buster

Grade 8.8 and 10.9

Property class markings indicating bolt strength. The first number represents tensile strength (8 or 10 x 100 MPa), whilst the second shows the ratio of yield strength to tensile strength. Grade 10.9 bolts are approximately 25% stronger than 8.8 grade, making them suitable for high-stress applications.

A2 and A4 Stainless Steel

Corrosion-resistant grades of stainless steel. A2 (304) offers excellent corrosion resistance for most environments, whilst A4 (316) provides superior protection against chlorides and marine conditions, making it ideal for coastal or chemical processing applications.

Galvanised vs Zinc Plated

Two methods of corrosion protection. Galvanising applies a thicker zinc coating through hot-dip processing, offering superior long-term protection. Zinc plating provides a thinner protective layer, suitable for indoor or less demanding outdoor applications.

Tensile Strength

The maximum load a bolt can withstand before breaking, measured in megapascals (MPa). Higher grade bolts offer greater tensile strength, essential for structural and safety-critical applications.

Thread Pitch

The distance between adjacent threads, typically specified in millimetres. Standard metric threads follow ISO specifications, ensuring compatibility with corresponding nuts and tapped holes across different manufacturers.

Who Uses Hexagon Bolts?

• Structural Engineers and Steel Erectors - for connecting steel beams, columns, and framework in building construction
• Mechanical Engineers and Fitters - assembling machinery, equipment, and mechanical systems
• Automotive Technicians - repairing and maintaining vehicles, including suspension, engine, and chassis components
• Agricultural Engineers - maintaining and repairing farm machinery and equipment
• Plant and Maintenance Engineers - for industrial equipment servicing and facility maintenance
• Fabricators and Welders - creating structural frameworks and custom metalwork
• Groundworkers and Civil Engineers - securing infrastructure components, barriers, and roadside furniture
• Marine Engineers - boat building and repair, particularly using A4 stainless steel grades
• DIY Enthusiasts - for home projects requiring robust, reliable fastening solutions

How to Choose the Right Hexagon Bolts

Material and Finish: Consider the environment where the bolt will be used. For indoor applications or where aesthetics matter, zinc plated bolts offer adequate protection at economical cost. Outdoor applications benefit from galvanised finishes, whilst marine environments, chemical processing, or food industry applications require A4 316 stainless steel. A2 304 stainless provides excellent all-round corrosion resistance for most outdoor situations.

Strength Grade: Match the bolt grade to your application's load requirements. Grade 8.8 bolts suit most general engineering and construction applications, providing reliable strength for everyday fastenings. Specify Grade 10.9 high tensile bolts for structural connections, critical safety applications, or where maximum clamping force is required. Always consult relevant engineering specifications and building regulations for structural work.

Size and Thread: Measure the diameter and length required for your application, accounting for the thickness of materials being joined plus adequate thread engagement in the nut. Standard metric threads are most common in the UK, following ISO specifications. Ensure sufficient thread protrudes through the nut - typically 2-3 threads beyond the nut face for proper connection.

Quantity Requirements: Calculate the number of bolts needed, adding a contingency for wastage or future maintenance. Many suppliers, including TooledUp, offer bulk purchasing options that provide better value for larger projects whilst ensuring you have matched sets from the same production batch.

Compatibility: Ensure you have compatible nuts, washers, and the correct spanners or socket sets for installation. Grade 8.8 and 10.9 bolts should be paired with nuts of matching or higher grade, and appropriate washers help distribute load and prevent surface damage.

Popular Accessories

• Hexagon Nuts - matching grade nuts in corresponding finishes and thread sizes
• Washers - flat washers, spring washers, and penny washers for load distribution
• Socket Sets and Spanners - quality tools from brands like Bahco, Wera, and Knipex for proper installation
• Torque Wrenches - essential for achieving specified tightening torque in critical applications
• Thread-Locking Compounds - for applications subject to vibration or where bolt loosening could occur
• Anti-Seize Compounds - particularly important for stainless steel bolts to prevent galling
• Impact Drivers and Wrenches - cordless options from Makita, DeWalt, and Milwaukee for efficient installation
• Thread Gauges and Callipers - for accurate measurement and specification verification

Safety Information

When working with hexagon bolts, always wear appropriate personal protective equipment including safety gloves to protect against sharp threads and edges, and safety glasses when cutting or grinding bolts to length. Ensure you're using the correct size tools to avoid rounding the bolt head or causing slippage that could result in injury.

For structural applications, never substitute lower grade bolts for specified higher grades, as this compromises structural integrity and safety. Always follow torque specifications provided by engineers or manufacturers - under-tightening can lead to joint failure whilst over-tightening may cause bolt fracture or thread stripping. When working at height or on critical safety applications, follow HSE guidelines and consider having work inspected by a qualified professional.

Store bolts in dry conditions organised by size and grade to prevent corrosion and ensure correct selection. When reusing bolts, inspect threads carefully for damage, deformation, or corrosion - critical applications should always use new fasteners. Be particularly cautious with stainless steel bolts, which can gall (cold weld) during installation; use appropriate anti-seize compounds and avoid over-tightening.

Frequently Asked Questions

What's the difference between Grade 8.8 and Grade 10.9 bolts?

Grade 10.9 bolts are approximately 25% stronger than Grade 8.8, with higher tensile and yield strength. Grade 8.8 is suitable for most general construction and engineering applications, whilst Grade 10.9 is specified for high-stress structural connections, automotive applications, and where maximum clamping force is required. Grade 10.9 bolts typically cost more, so specify them only where the additional strength is genuinely needed.

Can I use stainless steel bolts with mild steel components?

Yes, but consider potential galvanic corrosion when dissimilar metals are in contact, particularly in wet or coastal environments. Use appropriate washers to separate materials where necessary, or apply protective coatings. A2 stainless steel bolts are generally suitable for use with mild steel in most UK conditions, whilst A4 grade is preferable for marine or highly corrosive environments.

How much thread should protrude through the nut?

Best practice requires 2-3 complete threads protruding beyond the nut face after tightening. This ensures full thread engagement within the nut whilst providing visual confirmation of proper installation. For structural applications, consult the relevant engineering specifications as requirements may vary based on loading conditions and building regulations.

Should I use washers with hexagon bolts?

In most applications, yes. Washers distribute the clamping load over a larger area, protecting the surface being fastened and providing more consistent preload. Spring washers or locking washers help prevent loosening due to vibration. For structural steelwork and critical applications, washers are typically mandatory - always follow the specifications provided by your engineer or the relevant British Standards.

What's the advantage of galvanised over zinc plated finish?

Galvanising provides a thicker, more durable zinc coating that offers superior long-term corrosion protection, making it ideal for outdoor structural applications, agricultural use, and anywhere exposed to the elements. Zinc plating is thinner and more economical, suitable for indoor applications or less demanding outdoor use. For maximum longevity in harsh UK weather conditions, galvanised or stainless steel grades are recommended.