Cup Head Bolts Nuts

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.

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 bolts and nuts, hex head flanged bolts, and flat washers.