M8 Carriage Bolts A2 Stainless Steel — Cup Square Dome Head Coach Screws DIN 603 (30–70mm) - HomeDIYer
M8 Carriage Bolts A2 Stainless Steel — Cup Square Dome Head Coach Screws DIN 603 (30–70mm) - HomeDIYer
M8 Carriage Bolts A2 Stainless Steel — Cup Square Dome Head Coach Screws DIN 603 (30–70mm) - HomeDIYer
M8 Carriage Bolts A2 Stainless Steel — Cup Square Dome Head Coach Screws DIN 603 (30–70mm) - HomeDIYer
M8 Carriage Bolts A2 Stainless Steel — Cup Square Dome Head Coach Screws DIN 603 (30–70mm) - HomeDIYer
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M8 Carriage Bolts A2 Stainless Steel — Cup Square Dome Head Coach Screws DIN 603 (30–70mm) - HomeDIYerM8 Carriage Bolts A2 Stainless Steel — Cup Square Dome Head Coach Screws DIN 603 (30–70mm) - HomeDIYerM8 Carriage Bolts A2 Stainless Steel — Cup Square Dome Head Coach Screws DIN 603 (30–70mm) - HomeDIYerM8 Carriage Bolts A2 Stainless Steel — Cup Square Dome Head Coach Screws DIN 603 (30–70mm) - HomeDIYerM8 Carriage Bolts A2 Stainless Steel — Cup Square Dome Head Coach Screws DIN 603 (30–70mm) - HomeDIYer

M8 Carriage Bolts A2 Stainless Steel — Cup Square Dome Head Coach Screws DIN 603 (30–70mm)

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By HomeDIYer®

Price:
$12.58 USD
Stock:
In stock (500 units), ready to be shipped

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Description

 

M8 Carriage Bolts in A2 Stainless Steel — Secure, Rust-Resistant Fastening for Wood & Structural Projects

Whether you're building a backyard deck, assembling a timber pergola, or hanging a heavy gate, loose or rusted fasteners can compromise the entire structure. DIYers and contractors working with outdoor wood need a bolt that locks in place without spinning, resists the elements season after season, and meets a recognized dimensional standard — not a generic hardware bin grab-bag.

Each box in this listing contains M8 cup square dome head carriage bolts manufactured to DIN 603 in A2 (304) stainless steel. The 8mm shank features a square neck that embeds into timber to prevent rotation while you tighten the nut from the other side. Available lengths run from 30mm (≈1-3/16") to 70mm (≈2-3/4"), with pack quantities of 15–30 pieces per box depending on the length selected. All bolts carry a standard M8 metric coarse thread (1.25mm pitch) compatible with any M8 hex or wing nut.

Typical use cases include deck board-to-joist connections, fence rail and post assembly, timber frame and pergola construction, and wood-to-metal bracket fastening in garden structures. The smooth dome head sits flush and clean on the surface, making these coach screws a practical choice wherever a finished appearance matters alongside structural integrity.

🔩 Thread Compatibility: Standard M8 metric coarse thread (pitch 1.25mm) — fits all DIN 934 M8 hex nuts, M8 wing nuts, and M8 flat washers. Not compatible with imperial (SAE/UNC) threaded hardware.

✅ Key Features of These M8 Stainless Steel Carriage Bolts

  • 🔒Anti-Rotation Square Neck — The square shoulder under the dome head bites into timber on installation, holding the bolt stationary so you can tighten the nut single-handed without a second wrench on the bolt side.
  • 🌧️A2 Stainless Steel Construction — Grade 304 stainless provides reliable corrosion resistance for outdoor decking, fencing, and garden structures exposed to rain, humidity, and temperature cycling.
  • 📐DIN 603 Dimensional Standard — Manufactured to the DIN 603 specification for cup square dome head coach bolts, ensuring consistent head geometry, thread pitch, and square neck dimensions across every piece in the box.
  • 📦Project-Ready Pack Quantities — Sold in counted boxes (15–30 pcs depending on length) so you can order exactly what a job requires without sorting through bulk bags or paying for excess hardware.
  • 📏Five Length Options in One Listing — Choose from 30mm, 40mm, 50mm, 60mm, or 70mm to match your timber thickness — no need to source different products for different joints on the same build.
  • ✨Smooth Dome Head Finish — The rounded cup head leaves a clean, low-profile surface on the visible face of the joint — suitable for finished woodwork, furniture frames, and anywhere aesthetics matter alongside strength.

📐 Technical Specifications — M8 DIN 603 Carriage Bolts

Thread Size M8 (8mm diameter)
Thread Standard Metric coarse, pitch 1.25mm
Head Type Cup square dome head (carriage / coach bolt)
Dimensional Standard DIN 603
Material A2 Stainless Steel (Grade 304)
Finish Mill / natural stainless (no coating)
Available Lengths 30mm (≈1-3/16"), 40mm (≈1-9/16"), 50mm (≈2"), 60mm (≈2-3/8"), 70mm (≈2-3/4")
Head Diameter (typical) Typically 21–22mm — see variant options to confirm
Square Neck Width (typical) Typically 8mm — contact us to confirm if critical
Pack Quantity 30mm: 30 pcs/box | 40mm: 25 pcs/box | 50mm: 20 pcs/box | 60mm: 20 pcs/box | 70mm: 15 pcs/box
Nuts / Washers Included Bolts only — nuts and washers sold separately
Recommended Use Timber framing, decking, fencing, pergolas, wood-to-metal connections
Not Suitable For Concrete anchoring, masonry, or marine/saltwater immersion (use A4/316 for those)

❓ Frequently Asked Questions

How do I choose the right bolt length for my project?

Add up the total thickness of all materials being joined, then add approximately 10–15mm to allow for a flat washer and nut on the back. For example, joining two 20mm (3/4") boards typically calls for a 50mm (≈2") bolt. The five lengths in this listing — 30mm, 40mm, 50mm, 60mm, and 70mm — cover timber thicknesses from roughly 15mm up to 55mm combined.

What does A2 stainless steel mean, and how strong are these bolts?

A2 stainless (also called 304 stainless) is an austenitic grade with a tensile strength of typically 500–700 MPa and good resistance to rust and oxidation. It handles outdoor exposure in most climates well. For highly aggressive environments — prolonged saltwater spray, coastal installations, or chemical exposure — A4 (316) stainless is generally the better choice.

Can I use these carriage bolts outdoors or in wet conditions?

Yes. A2 stainless steel provides solid corrosion resistance for outdoor decking, fencing, pergolas, and garden structures exposed to rain and humidity. For prolonged saltwater or coastal environments, A4 (316) stainless fasteners are generally recommended to maximize service life.

Are these compatible with standard M8 nuts and washers I already have?

Yes — these bolts use a standard M8 metric coarse thread (1.25mm pitch) and are compatible with any DIN 934 M8 hex nut, M8 wing nut, or M8 flat washer. They are not compatible with imperial (SAE/UNC) threaded hardware. To maintain consistent corrosion resistance, we recommend pairing with A2 stainless M8 nuts and washers.

What are the dome head and square neck dimensions on an M8 DIN 603 bolt?

For M8 DIN 603 carriage bolts, the dome head diameter is typically around 21–22mm and the square neck width is typically 8mm. The square neck is designed to embed into timber and prevent the bolt from spinning during tightening. If you have critical tolerance requirements, please contact us to confirm exact dimensions before ordering.

Do nuts and washers come included in the box?

No — this listing includes carriage bolts only. Matching M8 hex nuts and flat washers are sold separately. We recommend sourcing A2 stainless M8 nuts and washers to keep the entire fastener assembly at the same corrosion-resistance level.

What applications are M8 DIN 603 carriage bolts not suitable for?

These bolts are designed for wood-to-wood and wood-to-metal connections. They are generally not suitable for concrete anchoring, masonry, or applications requiring through-hardened structural bolts. For those uses, consult a structural engineer and select the appropriate fastener grade and type.

🛒 Select your length above, then add to cart — ships from our US warehouse.

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