Buy Hex Bolts & Nuts Online in Australia
Hex Bolt & Nut Sizes — Quick Reference
Hex bolts are the workhorse structural fastener — sized by diameter × length, graded for tensile strength, and finished for corrosion resistance. Match the grade to the structural rating + the finish to the environment. AIMS stocks metric and imperial hex bolts + matching nuts from M6 to M36 in Grade 8.8, 10.9, hot-dip galvanised and 316 stainless.
| Bolt Size | AF (Across Flats) | Standard Pitch | Common Grade |
|---|---|---|---|
| M6 | 10 mm | 1.0 mm | Class 8.8 / Stainless A2-70 |
| M8 | 13 mm | 1.25 mm | Class 8.8 / 10.9 / Stainless A2-70 |
| M10 | 17 mm | 1.5 mm | Class 8.8 / 10.9 / Stainless A4-80 |
| M12 | 19 mm | 1.75 mm | Class 8.8 / 10.9 — workshop default |
| M16 | 24 mm | 2.0 mm | Class 8.8 / 10.9 — structural standard |
| M20 | 30 mm | 2.5 mm | Class 8.8 / 10.9 — heavy structural |
| M24 | 36 mm | 3.0 mm | Class 8.8 / 10.9 — very heavy structural |
| M30 | 46 mm | 3.5 mm | Class 8.8 / 10.9 — large machinery |
| M36 | 55 mm | 4.0 mm | Class 8.8 / 10.9 — very large mass |
Grade selection: 8.8 (800 MPa) is the standard structural grade. 10.9 (1,040 MPa) for high-tensile / machinery applications. Hot-dip galvanised for outdoor / structural exposure. 316SS for marine + chemical environments. For complete bolt grade reference, see our bolt grade chart. For torque values per size + grade, see our metric bolt torque chart. Companion: flat washers, spring lock washers, structural bolts.
Hex Bolts & Hex Nuts — Metric & Imperial Fasteners
Hex bolts and hex nuts are the most widely used structural fasteners in industrial, construction, and machinery applications. AIMS Industrial sells hex bolts and matching hex nuts in metric and imperial sizes — Grade 8.8 and 10.9 alloy steel, hot-dip galvanised, and 316 stainless steel — for the full range of industrial fastening applications from M6 to M36.
Hex Bolts & Nuts We Stock
- Grade 8.8 Hex Bolts: Metric Grade 8.8 zinc-plated hex head bolts (DIN 931 partially threaded, DIN 933 fully threaded) — the standard general-purpose structural and machinery bolt grade in ISO metric systems. Minimum tensile strength 800 MPa; yield strength 640 MPa.
- Grade 10.9 Hex Bolts: Metric Grade 10.9 alloy steel hex bolts for high-strength applications — minimum tensile strength 1,040 MPa. Grade 10.9 is specified for structural connections in machinery frames, high-load joints, and applications where a smaller fastener must carry a Grade 8.8 load.
- Hot-Dip Galvanised Hex Bolts & Nuts: HDG hex bolts and nuts for outdoor structural, civil infrastructure, mining, and agricultural applications. Hot-dip galvanising provides 80–100 micron zinc coating thickness — significantly greater corrosion resistance than electro-zinc plated fasteners in exposed outdoor conditions.
- 316 Stainless Steel Hex Bolts & Nuts: 316 ss hex bolts and matching nuts for marine, coastal, chemical, and food processing environments. 316 provides superior chloride resistance to 304 — required for coastal structures, marine fittings, and chemical plant.
- Matching Nuts: Hex nuts matched to bolt grade — Grade 8 nuts with Grade 8.8 bolts; Grade 10 nuts with Grade 10.9 bolts. Stainless nuts with stainless bolts. Always use matching or superior-grade nuts to avoid thread stripping under bolt preload.
Hex Bolt & Nut Specification Guide
- Fully Threaded vs Partially Threaded: Partially threaded hex bolts (DIN 931) have an unthreaded shank below the head — the shank fits the joint hole in bearing contact. Fully threaded hex screws (DIN 933) suit applications where thread runs to the bolt head. For structural shear connections, partially threaded bolts with shank in the shear plane are preferred.
- Bolt Length Selection: Bolt length should provide a minimum of 2–3 thread pitches protruding beyond the nut after full tightening. Excessive length wastes material and adds protruding thread hazard; insufficient length reduces thread engagement and joint integrity.
- Tightening to Specification: Structural hex bolt assemblies should be tightened to the specified torque using a calibrated torque wrench. Never estimate torque by feel — under-torqued joints relax under vibration; over-torqued joints damage threads and reduce clamping force.
Australian Business, Local Supply: As a proudly Australian business since 1988, we stock locally and work with trusted local Australian manufacturers and distributors to ensure fast, reliable supply.
Expert Support: Need help buying the right product for your application? Contact our team for application-specific advice or request a quote.
See our full fasteners range including hex head flanged bolts, hex set bolts, and hex lock nuts.
People Also Ask — Hex Bolts and Nuts
Q: What's the difference between a hex bolt and a hex screw?
Terminology varies — in Australian usage they're often interchangeable for hex-headed threaded fasteners. Strictly: a hex bolt is sized to be tightened with a nut (fully threaded or partially threaded shank passing through both parts), a hex screw threads into a tapped hole without a nut. Both have 6-sided heads driven by a spanner or socket. AIMS lists hex bolts and screws together as a single product family.
Q: What grade hex bolt do I need?
Grade 4.6: low-tensile carbon steel, general light-duty use. Grade 8.8: high-tensile workshop standard — most engineering applications, structural mounts, machinery fixings. Grade 10.9 and 12.9: high-tensile alloy steel for high-load critical bolting. A2-70 (304 stainless) and A4-70 (316 stainless) for corrosion service. The grade is stamped on the head — 8.8, 10.9, etc. Match the grade to the joint's clamp load requirement.
Q: What length hex bolt do I need?
Length is measured from under the head to the end of the thread (not including head height). For through-bolting: thickness of clamped parts + nut + 1-2 threads protruding. For tapping into a hole: thickness above the hole + at least 1-1.5× bolt diameter of thread engagement. Standard lengths step in 5mm or 10mm increments (metric) and 1/4" or 1/2" (imperial) — round up to next standard length.
Q: Do I need washers under hex bolts?
Strongly recommended for most applications. Flat washers spread load and protect surface finish. Spring washers (split-lock) or Nord-Lock washers prevent vibration loosening. Wave washers for take-up of small gaps. For permanent assemblies that won't be undone, washers can sometimes be skipped — but the small cost is worth the increase in joint reliability. Stainless bolts need stainless washers to prevent galvanic corrosion.
Q: How tight should I torque a hex bolt?
Match torque to bolt grade, size, and lubrication condition. Standard 8.8 dry: M6=10Nm, M8=24Nm, M10=48Nm, M12=83Nm, M16=205Nm. Lubricated threads reduce target torque by ~15-20% for same clamp force. For critical bolting, use a calibrated torque wrench. For general workshop assembly, calibrated feel works for non-critical joints. Always check the equipment manual for specific torque specs on automotive, structural, or pressure-vessel bolting.