M8 Hex Head Coach Screws DIN 571

M8 hexagon head coach screws manufactured to DIN 571. Also known as lag screws, lag bolts or hex head wood screws, these heavy-duty fasteners use a hexagon head rather than a slotted or recessed drive, so they can be tightened with a standard spanner or socket for much higher torque than a screwdriver allows – useful wherever a standard wood screw can't generate enough clamping force on its own.

The screws are manufactured from high-tensile carbon steel and finished with a bright zinc-plated (BZP) coating, giving general-purpose corrosion resistance.

The coarse, deep wood-screw thread is designed to bite directly into timber, generating high pull-out resistance without needing a nut on the far side – making these screws well suited to structural and semi-structural timber connections. Used with a suitable wall plug, they can also be driven into brick, block or concrete.

Key Features

• Manufactured to DIN 571, so thread, head and drive sizes are consistent and standard-compliant across every length.
• Hexagon head accepts a standard spanner or socket rather than a screwdriver, allowing far greater tightening torque – useful for dense or hardwood timber and heavier structural fixings.
• High-tensile carbon steel construction with a bright zinc-plated (BZP) finish for reliable general-purpose corrosion resistance.
• Coarse, deep wood-screw thread bites directly into timber and generates high pull-out resistance without requiring a nut on the reverse face.
• Also known as lag screws or lag bolts, and suited to structural and semi-structural timber-to-timber connections.
• Available in seven lengths from 30mm (1.18in) to 160mm (6.30in), all sharing the same M8 (8mm / 0.31in) thread diameter and 13mm (0.51in) head across flats.
• Thread length is 60% of the overall screw length on every size, giving a longer grip length as the screw gets longer.
• Can be combined with a suitable wall plug to fix into brick, block or concrete as well as solid timber.

Specification

Thread, head and drive dimensions are as specified in DIN 571 for the M8 (8mm) thread size.

Typical Applications

The combination of a coarse, deep wood-screw thread, high pull-out resistance and a spanner-drivable hexagon head makes these coach screws well suited to a wide range of structural and semi-structural timber fixing tasks, including:

• Decking frames, ledger boards and joists, where high pull-out resistance and spanner-driven torque suit structural timber-to-timber connections.
• Fence posts, rails and gate hardware, including heavier gate fittings that need a secure, split-resistant fixing.
• General timber framing and carpentry work, wherever a coarse-thread, hex-drive fastener is preferred over a standard wood screw.
• Furniture making, interior fittings, and repair and renovation projects in timber.
• Landscaping projects such as railway-sleeper retaining walls and raised beds, where the longer lengths bite deep into thick timber sections.
• With a wall plug, fixing heavy-duty ironmongery, brackets and fittings into brick, block or concrete.

Installation Guidance

Pre-drilling correctly is the single biggest factor in a strong, split-free fixing with a coach screw this size. As a general guide:

• Pre-drill a pilot hole – strongly recommended to prevent the timber splitting and to ease driving.
• Drill a clearance hole through the first (fixing) timber, sized to the screw's shank.
• Drill a smaller pilot hole into the second timber, sized to roughly the thread's root diameter – use a smaller pilot in softer timbers than in dense hardwoods.
• Drill to at least the full length of the screw before driving.
• Drive home with a 13mm (0.51in) spanner or socket.
• Fit a washer under the head – good practice that spreads the load and stops the head sinking into softer timber.

Common Questions

Which length do I need?
Choose a length that passes through the timber you are fixing and leaves the threaded part in the timber beneath. Thread length is 60% of the screw length, listed for every size in the table above.

What spanner or socket fits?
A 13mm (0.51in) spanner or socket on every length.

Do I need to pre-drill?
Yes, a pilot hole is strongly recommended to prevent splitting: a clearance hole through the first timber and a smaller pilot hole into the second, as in the Installation Guidance above.

Can I fix them into brick or concrete?
Yes, with a suitable wall plug in brick, block or concrete.