Forgefix Carriage Bolt & Nut - M10 x 180mm - Bag 10 - White

A Carriage Bolt (also known as a Coach Bolt or Cup Square Hex Bolt) is a type of bolt characterized by its domed or countersunk head and a square section directly underneath the head. This square section is designed to grip into wood, preventing the bolt from rotating when the nut is tightened.

Zinc plating is a protective coating applied to the steel bolt. It prevents rust and corrosion by forming a barrier against moisture and air, and also by acting as a 'sacrificial anode,' meaning the zinc corrodes before the steel underneath, thereby protecting the bolt's integrity.

While the bolt itself is strong, its design (specifically the square neck) is optimized for embedding into timber. For metal-to-metal connections, the square neck would not seat properly, allowing the bolt to spin during tightening. Standard hex bolts or other specialized metal fasteners are generally more suitable for such applications.

Washers are not strictly required as the hex nut provides a sufficient bearing surface. However, adding a flat washer under the nut is often recommended, especially when fastening into softer woods, as it helps distribute the clamping force over a wider area, reducing the risk of crushing the timber surface and providing a more secure hold.

These Forgefix Carriage Bolts and their accompanying nuts conform to DIN 603 (for the carriage bolt) and DIN 934 (for the hex nut) standards. These are German industrial standards that specify the dimensions, materials, and mechanical properties, ensuring quality and interoperability.

This specific product variant, 'Forgefix Carriage Bolt & Nut - Zinc Plated - M10 x 180mm', comes in a bag of 10 bolts, each with its corresponding hex nut.

Ensure the square section directly under the bolt head is fully embedded into the timber. If not, gently tap the bolt head with a hammer to seat it properly. The pilot hole might be slightly too large, or the timber might be too soft to grip the square section effectively. Consider using a washer under the nut to increase clamping force if the issue persists due to material softness.

Verify the pilot hole diameter. It should be slightly larger than the bolt's shank but smaller than the square section. For an M10 bolt, a 10.5mm or 11mm drill bit is usually appropriate. If the hole is too small, enlarge it slightly. If the timber is very hard, ensure the drill bit is sharp.

While zinc plated, severe abrasions or prolonged exposure to harsh corrosive agents can compromise the coating. Inspect for physical damage to the plating. For minor surface rust, it might be cosmetic, but for deeper rust, the protective layer has been breached. Consider applying a rust-inhibiting paint or sealant over the bolt head and nut for added protection, especially in severely exposed areas.