M12 Coach Screws

M12 coach screws have a thread diameter of 12mm and are commonly used for fastening metal to wood or two or more pieces of timber. They are also known as M12 lag screws or M12 lag bolts.

M12 Coach Screw Dimensions

  • Thread Diameter: 12mm
  • Socket Size: 19mm
  • Head Height: 8mm
  • Head Type: Hexagon
  • Specification: DIN 571

M12 stainless steel coach screws are tightened with a 19mm socket, making them easy to grip and remove. The threads on M12 coach screws are coarser than those on M10 coach screws, making them less likely to strip. 

M12 Stainless Steel Coach Screws 12mm DIN 571

M12 coach screws in stainless steel are sometimes called M12 lag bolts or lag screws because they were commonly used to attach lag brackets to wood. They are also used to fasten metal to wood, in applications where a high level of torque is required, such as attaching deck boards to a joist, and sometimes in masonry projects. It is recommended to drill a pilot hole before use for maximum stability.

Browse our full range of stainless steel coach screws.

Not what you were looking for? Find M12 coach bolts DIN 603 here. 

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M12 Coach Screws – Stainless Steel (DIN 571 Hex Head) | Fixabolt®

Big screws for big builds. Made for timber. Built to last.

Fixabolt® M12 coach screws are heavy-duty hex head timber fixings engineered for structural strength and long-term durability. Manufactured to DIN 571, these 12mm diameter stainless steel screws are ideal for securing large timbers, sleepers, beams, and wall plates, whether you're working on landscaping projects, outdoor joinery, or timber-to-masonry connections with plugs.

The coarse thread and sharp point deliver solid bite into wood, while the hex head allows fast and powerful installation with a spanner or impact driver.

Product Specifications

  • Thread Size: M12 (12mm diameter)
  • Standard: DIN 571 – part-threaded, hex head timber screw
  • Drive Type: Hex head – compatible with spanners, sockets, and impact tools
  • Lengths Available: 50mm to 200mm

Material Options:

A2 stainless steel (304) – ideal for outdoor structural use. Made for strength. Designed for the elements. Ready for the job site.

Common Applications for M12 Coach Screws

Fixabolt® M12 coach screws are perfect for:

  • Securing structural timber beams and wall plates
  • Fixing large fence posts, gate hinges, and supports
  • Timber-to-brick or timber-to-steel fixings (with rawl plugs)
  • Retaining walls, railway sleepers, and pergolas
  • Heavy-duty joinery, garden frames, and external timber builds

Pre-drilling is recommended for best performance and to prevent splitting, especially in hardwood or dense materials.

Why Buy Coach Screws from Fixabolt®?

✔ Stainless steel as standard – no rust, no nonsense

✔ DIN 571 compliant for consistent sizing and strength

✔ Perfect for builders, landscapers, and outdoor trades

✔ Bulk pricing available for trade quantities

✔ Fast, tracked UK delivery – from a supplier you can rely on

Need matching M12 stainless steel washers? You’ll find them right here at Fixabolt®.

Fixings you can count on. From start to finish. Fix it with Fixabolt®.