M12 (12mm) Hex Head Coach Screws - Heavy Duty BZP Timber Fasteners

M12 hexagon head coach screws, manufactured to DIN 571 with the wood-screw thread form conforming to DIN 7998. Also widely known as lag screws or lag bolts, these heavy-duty fasteners are fitted with a hexagon head rather than a slotted or recessed drive, so they are tightened with a standard spanner, socket or impact wrench rather than a screwdriver – delivering much higher installed torque and a stronger, more positive clamping force than a driven screw head allows. That combination of a robust hex head and a coarse wood-screw thread is what makes the coach screw the standard choice wherever a demanding timber connection needs to be pulled up tight and stay tight.

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

At 12mm (0.47in) diameter, this is the heaviest-duty size in the coach screw range, built for critical structural and semi-structural timber connections where a lighter-gauge screw would not offer sufficient shank strength or thread engagement. 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 of the joint. Used with a suitable wall plug, the same screw can also be driven into brick, block or concrete – a genuinely versatile heavy fixing for both timber-to-timber and timber-to-masonry work.

Key Features

• DIN 571 hex head coach screw: manufactured to the DIN 571 dimensional standard, with the wood-screw thread form to DIN 7998, so head, shank and thread dimensions are consistent batch to batch.
• Hexagon head drive: tightens with a standard spanner, socket or impact wrench, delivering far higher installed torque than a screwdriver-driven screw head.
• High-tensile carbon steel: gives the shank and thread the strength needed for heavy structural and semi-structural timber connections.
• Bright zinc-plated (BZP) finish: general-purpose corrosion resistance.
• 12mm (0.47in) diameter: the heaviest-duty size in the coach screw range, for the most demanding timber fixings.
• Coarse, deep wood-screw thread: bites directly into timber for high pull-out resistance without the need for a nut on the far side.
• 19mm (0.75in) head across flats: a single spanner or socket size fits every length in the range.
• Wide length range: 80mm to 300mm (3.15in to 11.81in) across 11 sizes, covering everything from light structural work to heavy sleeper and post fixings.

Specification

Thread, head and drive dimensions are as specified in DIN 571 for the M12 (12mm) thread size. Minimum thread length is DIN 571's own specified 60% of the overall shank length – actual thread length on a given batch may run longer than this minimum.

Typical Applications

The coach screw's combination of a hex head, for high installed torque, and a deep wood-screw thread, for high pull-out resistance, makes it well suited to permanent, load-bearing timber connections:

• Structural timber: beams, joists and wall plates, where a strong mechanical connection needs to be pulled up tight with a spanner, socket or wrench rather than driven with a screwdriver.
• Decking and outdoor timber structures: decking subframes, pergolas and carports, with the screw's high pull-out resistance.
• Heavy-duty fencing and gates: fence posts, gate hinges and supports, where a fixing that can be torqued up hard and won't work loose is essential.
• Landscaping work: railway-sleeper retaining walls and raised beds, where the coarse thread bites securely into dense, often reclaimed sleeper timber.
• Timber-to-masonry fixing: with a suitable wall plug, the same screw can be used to fix large brackets or heavy-duty ironmongery into brick, block or concrete.

Installation Guidance

Pre-drilling a pilot hole is strongly recommended to prevent the timber from splitting and to ease driving, particularly at this larger 12mm diameter:

• Drill a clearance hole through the first (fixing) timber, sized to the screw's shank diameter.
• Drill a pilot hole into the second timber, sized to roughly the thread's root diameter – use a smaller pilot in softer timbers and a larger one in dense hardwoods.
• Drill to at least the full length of the screw before driving, rather than relying on the screw to cut its own way through undrilled timber.
• Drive home with a 19mm (0.75in) spanner, socket or impact wrench.
• Fit a washer under the head as good practice – this spreads the load and helps prevent the head sinking into softer timber.

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