Buy Cup Head Bolts Nuts Online in Australia
Cup Head Bolt (Coach / Carriage Bolt) Selection — Quick Reference
Cup head bolts (coach bolts / carriage bolts) have a domed (cup) head + a SQUARE NECK below the head — the square neck bites into timber + prevents the bolt rotating during nut tightening. Used in timber + structural + decking + framing assembly.
| Cup Head Bolt Type | Best For | Material / Coating |
|---|---|---|
| Galvanised Cup Head (Hot-Dip) | Outdoor + structural timber + decking | Hot-dip galv carbon steel |
| Zinc-Plated Cup Head | Indoor + dry timber assembly + workshop | Zinc-plated steel |
| Stainless 304 Cup Head | General corrosion + indoor outdoor | 304 SS |
| Stainless 316 Cup Head | Marine + chemical + saltwater + chloride | 316 SS |
| Metric Sizes (M6/M8/M10/M12/M16) | Standard workshop range | — |
| Imperial Sizes (1/4" - 5/8") | Older AU + UK + imported equipment | — |
| Common Lengths | 25mm – 200mm typical | Match to material thickness + nut engagement |
| Matched Cup Head Nut + Washer | Square + flat washer pair to spread load | — |
How it works: Drill clearance hole through timber. Insert cup head bolt with hammer — square neck bites into timber. Tighten nut from other side — bolt stays still (no spanner on head needed). The DOMED head sits flush + safe. Critical: Square neck must FULLY engage timber — undersized hole = bolt won't seat; oversized = bolt spins under torque. Match washer + nut to bolt grade. Brands: Bremick, Hobson, Champion. Companion: fasteners, hex bolts + nuts, coach bolt guide.
Cup Head Bolts & Coach Bolts — Carriage Bolts for Timber & Structural Use
Cup head bolts (coach bolts or carriage bolts) feature a domed head and a square neck below the head that bites into timber — preventing the bolt from rotating during nut tightening. AIMS Industrial sells cup head bolts in metric hot-dip galvanised and 316 stainless steel for timber construction, fencing, agricultural structures, and outdoor fastening applications requiring corrosion resistance.
Cup Head Bolts We Stock
- Hot-Dip Galvanised Cup Head Bolts: Hot-dip galvanised (HDG) cup head bolts for outdoor timber construction, fencing, agricultural infrastructure, and coastal construction. HDG provides superior corrosion resistance compared to electro-galvanised or zinc-plated equivalents — the thick zinc coating sacrificially protects the steel substrate in exposed conditions.
- 316 Stainless Steel Cup Head Bolts: 316 stainless steel cup head bolts for marine, coastal, and chemical environments where hot-dip galvanised would corrode in the service life. 316 ss resists chloride and oxidation attack — required within 500m of the coastline per Australian coastal construction guidelines.
- Metric Cup Head Bolt Range: Cup head bolts from M6 × 25mm to M16 × 200mm — covering the standard size range for post-and-rail fencing, timber frame construction, and structural bracing applications.
- Cup Head Nuts & Washers: Matching hex nuts and large-area flat washers for cup head bolt assemblies — supplied in matching galvanised or stainless steel grade to prevent galvanic corrosion between dissimilar metals at the joint.
Cup Head Bolt Selection Guide
- Square Neck Timber Grip: The square neck under the cup head bolt head must be fully embedded in timber to be effective — in metalwork and non-timber applications the square neck does not key and the bolt must be held with a spanner or socket from the head side during tightening.
- HDG vs Stainless in Coastal Environments: For coastal construction within 500m of the ocean, 316 stainless is generally required. HDG may be suitable for inland agricultural use. Check the relevant Australian Standard or engineer specification for the required corrosion protection grade.
- Thread Length: Select cup head bolt length to provide at least 2–3 threads protruding beyond the nut after final tightening — insufficient thread length risks nut disengagement under load or vibration.
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