Product Description
DIN 603 Stainless Steel Carriage Bolts, also known as Coach Bolts or Mushroom Head Square Neck Bolts, are widely used fastening components designed for secure and anti-rotation installation in wood, metal, construction, furniture, agricultural equipment, and industrial assemblies. Featuring a smooth domed mushroom head and square neck beneath the head, these bolts provide a clean appearance while preventing spinning during tightening.
Manufactured according to DIN 603 standards, these carriage bolts are available in high-quality stainless steel grades such as A2 (304) and A4 (316), offering excellent corrosion resistance, high durability, and long service life in indoor, outdoor, and marine environments.
The square neck locks into pre-drilled square or wooden holes, allowing the nut to be tightened from one side without requiring a tool on the bolt head. This makes DIN 603 carriage bolts ideal for timber structures, fencing systems, decking, machinery, playground equipment, and stainless steel assemblies.
Key Features
- Manufactured according to DIN 603 standard
- Smooth mushroom dome head for safety and aesthetics
- Square neck design prevents bolt rotation during installation
- Excellent corrosion resistance for outdoor and humid environments
- Suitable for wood-to-wood and wood-to-metal fastening
- Available in full thread and partial thread options
- Easy one-sided installation
- Clean finished appearance without exposed hex heads
- Suitable for industrial, structural, and decorative applications
Available Materials
| Material Grade |
Description |
Application |
| Stainless Steel A2 / 304 |
Standard corrosion-resistant stainless steel |
General outdoor & industrial use |
| Stainless Steel A4 / 316 |
Marine-grade stainless steel |
Coastal & chemical environments |
| Carbon Steel |
High strength economical option |
Indoor & heavy-duty fastening |
| Zinc Plated Steel |
Corrosion-protected carbon steel |
General industrial applications |
Surface Finishes
| Finish |
Characteristics |
| Plain Stainless Steel |
Natural corrosion resistance |
| Polished |
Decorative and clean appearance |
| Zinc Plated |
Basic rust protection |
| Hot Dip Galvanized |
Heavy-duty outdoor protection |
| Black Oxide |
Industrial dark finish |
Product Structure
DIN 603 carriage bolts consist of:
| Part |
Function |
| Mushroom Head |
Smooth rounded surface for safety and appearance |
| Square Neck |
Prevents rotation during tightening |
| Threaded Shank |
Secures fastening with nut |
| Nut & Washer (Optional) |
Provides locking and load distribution |
Technical Specifications
| Standard |
DIN 603 |
| Product Type |
Carriage Bolt / Coach Bolt |
| Head Type |
Mushroom Dome Head |
| Neck Type |
Square Neck |
| Thread Type |
Metric Coarse Thread |
| Material |
Stainless Steel 304 / 316 |
| Thread Direction |
Right-Hand Thread |
| Size Range |
M5 – M20 |
| Length Range |
16mm – 300mm |
| Application |
Wood, Construction, Machinery, Furniture |
Common Size Range
| Diameter |
Common Lengths |
| M5 |
16mm – 60mm |
| M6 |
20mm – 100mm |
| M8 |
25mm – 150mm |
| M10 |
30mm – 200mm |
| M12 |
40mm – 250mm |
| M16 |
50mm – 300mm |
| M20 |
60mm – 300mm |
Advantages of DIN 603 Carriage Bolts
Anti-Rotation Design
The square neck locks firmly into wood or square holes, preventing unwanted spinning during tightening.
Safe Smooth Head
The rounded mushroom head reduces snagging and injury risks compared to hex head bolts.
Excellent Corrosion Resistance
Stainless steel construction ensures long-lasting performance in humid, outdoor, and marine conditions.
Attractive Appearance
Ideal for visible installations where aesthetics matter, such as furniture, fences, playgrounds, and architectural structures.
Easy Installation
Can be installed using only one-side tool access.
Typical Applications
- Wooden structures
- Timber framing
- Fence systems
- Decking construction
- Agricultural machinery
- Playground equipment
- Outdoor furniture
- Solar mounting systems
- Steel-to-wood assemblies
- Industrial equipment
DIN 603 Dimensional Reference
| Thread Size |
Pitch (P) |
Head Diameter (dk) |
Square Neck (s) |
| M5 |
0.8 |
13.55mm |
5mm |
| M6 |
1.0 |
16.55mm |
6mm |
| M8 |
1.25 |
20.65mm |
8mm |
| M10 |
1.5 |
24.65mm |
10mm |
| M12 |
1.75 |
30.65mm |
12mm |
| M16 |
2.0 |
38.8mm |
16mm |
| M20 |
2.5 |
46.8mm |
20mm |
Why Choose Stainless Steel DIN 603 Carriage Bolts?
Stainless steel carriage bolts offer superior durability compared to ordinary carbon steel fasteners. They maintain structural integrity and appearance even after long-term exposure to moisture, rain, chemicals, and outdoor environments.
A2 stainless steel is suitable for most industrial and construction projects, while A4 stainless steel is recommended for marine, coastal, and chemical applications requiring enhanced corrosion resistance.
Packaging Options
| Packaging Type |
Description |
| Small Box Packing |
Retail & hardware distribution |
| Bulk Carton Packing |
Industrial wholesale supply |
| Pallet Packaging |
Export shipment |
| Customized Packaging |
OEM branding available |
FAQ
What is the difference between a carriage bolt and a hex bolt?
A carriage bolt has a smooth mushroom head and square neck designed to prevent rotation, while a hex bolt uses a hexagonal head tightened with a wrench.
Why is the square neck important?
The square neck locks into wood or square holes to stop the bolt from spinning during tightening.
Are DIN 603 carriage bolts suitable for outdoor use?
Yes. Stainless steel A2 and A4 carriage bolts provide excellent corrosion resistance for outdoor and humid environments.
What is the difference between A2 and A4 stainless steel?
A2 (304) stainless steel is suitable for general applications, while A4 (316) offers superior resistance against saltwater and chemicals.
Can carriage bolts be used with metal?
Yes. They are commonly used in wood-to-metal and metal-to-metal fastening applications when paired with washers and nuts.
Are custom sizes available?
Yes. Customized diameters, lengths, materials, finishes, and packaging can be supplied according to project requirements.
What industries commonly use DIN 603 carriage bolts?
Construction, furniture manufacturing, agriculture, machinery, transportation, fencing, and renewable energy industries widely use DIN 603 carriage bolts.
Do you provide OEM or customized packaging?
Yes. OEM laser marking, custom labels, private packaging, and export carton solutions are available for bulk orders.
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