Structural Hex Nuts

Structural Hex Nuts for Australian Steel Construction

Structural hex nuts are the matched component to structural bolts in load-bearing steel connections — engineered to develop the full tensile strength of the matching bolt without thread strip or nut failure. For Australian structural steelwork, building construction, and bridge engineering, structural hex nuts compliant with AS/NZS 1252 are essential. AIMS Industrial supplies structural hex nuts from Hobson and approved fastener brands matched to the structural bolt range.

The structural nut grades we stock

• Class 8 nuts — matched to Class 8.8 structural bolts
• Class 10 nuts — matched to Class 10.9 high-strength structural bolts
• Galvanised structural nuts — hot-dip galvanised for outdoor and corrosive environments
• Self-colour structural nuts — untreated for indoor applications

Why structural nuts differ from standard hex nuts

Structural hex nuts are dimensionally and materially different from standard hex nuts in three ways:

• Higher tensile grade — must develop the full strength of the matching high-tensile bolt
• Greater height (thicker section) — provides more thread engagement length to handle higher loads
• Tighter dimensional tolerance — produces consistent bolt-and-nut assembly behaviour for engineered connections

Substituting a standard nut in a structural application means the nut may strip or fail before the bolt reaches its rated tension. The matched assembly performance is lost.

Match to bolt grade — the rule

• Class 8.8 bolts → Class 8 nuts
• Class 10.9 bolts → Class 10 nuts

Don't mix grades — using a Class 8 nut on a Class 10.9 bolt limits the assembly to Class 8 capacity at best, and may strip under tightening to Class 10 specifications. Match grades exactly.

Where structural hex nuts earn their place

• Steel building construction — primary structural connections
• Bridge engineering — load-bearing connections in steel bridges
• Industrial steelwork — heavy frames, equipment supports, structural mounts
• Pre-engineered buildings — bolted moment connections
• Structural repairs and modifications — adding or modifying structural connections

Compliance — AS/NZS 1252

Structural hex nuts used in Australian structural steelwork must comply with AS/NZS 1252. The standard specifies dimensions, materials, mechanical properties, and marking requirements. Compliant nuts carry stamped grade markings on the nut face — Class 8 and Class 10 markings are standardised. Building inspectors and structural engineers verify compliance via these markings; unmarked nuts can't be used in approved structural connections.

Sizing

Structural hex nuts are sized to match the corresponding bolt diameter — M12, M16, M20, M24, M30, M36 are the common metric sizes. The wrench size (across-flats dimension) is standardised for each diameter. Don't substitute nut sizes; nuts are paired one-for-one with the matching bolts.

Brands stocked at AIMS

Hobson covers the structural hex nut range across Class 8 and 10 grades in galvanised and self-colour finishes. Bremick stocks complementary structural fasteners. For specific applications or large-quantity orders, sourcing through our distribution channels covers most requirements.

Surface treatment matching

Match the nut finish to the bolt finish: galvanised bolts with galvanised nuts, self-colour bolts with self-colour nuts. Mixing galvanised and untreated components in the same connection leads to galvanic corrosion that fails the connection prematurely in outdoor environments.

Companion ranges at AIMS

Structural hex nuts sit alongside our broader structural fastener range — see structural bolt assemblies, structural washers, safety washers, and threadlockers for the related products.

Need help speccing structural nuts for a specific project? contact our team — we'll match by grade, size, and AS/NZS 1252 compliance requirements.