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Steel Carriage Bolt GB12 DIN603 M4 Truss Round Head Square Neck 10–100mm 10pcs
Steel Carriage Bolt GB12 DIN603 M4 Truss Round Head Square Neck 10–100mm 10pcs
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Steel Carriage Bolt GB12 DIN603 — M4 Truss Round Head Square Neck, 10–100mm, 10pcs
DIN603 / GB12 carriage bolts (also called coach bolts or round head square neck bolts) feature a smooth dome head with no drive recess and a square neck that bites into wood or soft material to prevent rotation during tightening — allowing the nut to be tightened from one side only without holding the bolt head. This makes them the standard fastener for wood furniture assembly, shelving, and structural joinery where a clean, tool-free bolt head is required.
Key Specifications
| Parameter | Value |
|---|---|
| Material | Carbon Steel (zinc-plated) |
| Standard | DIN603 / GB12 |
| Thread Size | M4 |
| Head Style | Truss round head (dome, no drive recess) |
| Neck Style | Square neck (anti-rotation) |
| Length Range | 10mm – 100mm |
| Quantity | 10pcs per pack |
Why Choose DIN603 Carriage Bolts?
- Square neck anti-rotation — square neck bites into wood or soft material; prevents bolt from spinning during nut tightening without holding the head
- Smooth dome head — no drive recess; clean, snag-free appearance on the visible face of furniture and structural assemblies
- One-side assembly — tighten the nut from one side only; ideal for through-bolted furniture joints where the bolt head is inaccessible after assembly
- 10–100mm length range — covers thin panel assembly (10–20mm) through thick structural timber joinery (80–100mm)
- 10pcs pack — practical quantity for furniture assembly and DIY projects
Typical Applications
- Wood furniture assembly — table legs, shelf brackets, bed frames, cabinet joints
- Outdoor furniture and garden structures (treated timber, decking)
- Playground and climbing frame structural joinery
- Shelving and storage rack assembly
- DIY workbench and workshop furniture construction
- Structural timber joinery and post-and-beam construction
Compatible With
- M4 hex nuts, nyloc nuts, and wing nuts
- M4 flat washers and spring washers
- Wood materials: softwood, hardwood, plywood, MDF, OSB
- Spanner / socket for nut: M4=7mm AF
Package Contents
- 10× M4 DIN603 carriage bolts (length per variant)
- Note: nuts and washers sold separately
Frequently Asked Questions
- Q: How does the square neck prevent the bolt from spinning?
- A: When the carriage bolt is pushed through a drilled hole in wood, the square neck is pulled into the wood as the nut is tightened. The corners of the square neck bite into the wood fibres, creating a mechanical interlock that prevents the bolt from rotating. This allows the nut to be tightened from one side without holding the bolt head.
- Q: What drill bit size should I use for M4 carriage bolts?
- A: Drill a 4.5mm round hole for the bolt shank. The square neck will self-locate and bite into the wood when the nut is tightened. Do not drill a square hole — the round hole is correct.
- Q: Can carriage bolts be used in metal?
- A: Carriage bolts are designed for wood and soft materials where the square neck can bite in. In metal, the square neck cannot grip and the bolt will spin. For metal assembly, use a standard hex bolt with a spanner on both the bolt head and nut.
