M12 Coach Bolts Stainless Steel

M12 coach bolts, also known as M12 carriage bolts, are durable fasteners with a domed head and a square neck designed for secure fastening in wood or metal. The M12 size refers to the 12mm diameter of the threaded shaft, making these bolts ideal for heavy-duty applications such as construction, woodworking, and structural projects.

Their square neck prevents rotation during tightening, while the smooth, rounded head offers a clean, tamper-resistant finish. Suitable for both indoor and outdoor use, stainless steel M12 coach bolts are often used in conjunction with nuts and washers for a firm, lasting hold.

M12 Coach Bolt Dimensions

  • Thread Diameter: 12mm
  • Thread Pitch: 1.75mm
  • Head Height: 6mm
  • Specification: DIN 603 

Stainless Steel M12 Coach Bolts

At Fixabolt, we supply a complete range of stainless steel M12 coach bolts (also known as M12 carriage bolts).

If you're not after 12mm, browse our full range of stainless steel coach bolts.

Please Note: M12 coach bolts may come fully threaded or partially threaded depending on source of manufacture.

Not what you were looking for? Find the similarly-named M12 coach screws here. 

20 products


M12 Coach Bolts – Stainless Steel (DIN 603 Carriage Bolts) | Fixabolt®

Heavy-duty fixings. Clean finish. Built for strength.

Fixabolt® M12 coach bolts are tough, reliable fixings for timber-to-timber and metal-to-wood applications. Manufactured to DIN 603, these 12mm stainless steel carriage bolts feature a rounded, low-profile head and a square neck that locks into timber during tightening, preventing the bolt from spinning when access is limited to one side.

Ideal for large-scale structural joinery, outdoor frameworks, and landscaping work, M12 coach bolts offer serious holding power with a smooth, tamper-resistant finish.

Product Specifications

  • Thread Size: M12 (12mm diameter)
  • Standard: DIN 603 – coach bolt with mushroom head and square neck
  • Head Type: Smooth, domed head – tamper-resistant and low-profile
  • A2 (304) stainless steel – general-purpose corrosion resistance
  • Lengths Available: 50mm to 300mm

These 12mm coach bolts are commonly used in:

  • Heavy-duty timber framing and jointing
  • Decking, pergolas, and structural garden builds
  • Timber-to-metal fixings using brackets or baseplates
  • Securing gate posts, sleepers, or fencing
  • Outdoor furniture and public infrastructure

Perfect for any application where bolt access is only available from one side, and a clean, safe finish is required.

Shop related collections:

Stainless steel M6 coach bolts

Stainless steel M8 coach bolts

Stainless steel M10 coach bolts

Stainless steel M16 coach bolts

Why Fixabolt®?

✔ High-grade stainless steel fixings

✔ DIN 603 compliant for consistency and compatibility

✔ Bulk pricing for trade quantities

✔ Fast, reliable UK-wide delivery

✔ Trusted by UK builders, joiners, and landscapers

Fix it once. Fix it right. Fix it with Fixabolt®.