Forgefix Carriage Bolt & Nut - White

'M8' refers to the bolt's nominal diameter of 8 millimeters. '40mm' indicates the bolt's length, measured from the underside of its head to the tip of the threaded portion. This specifies the size of the fastener.

Zinc plating (ZP) is a protective coating applied to the bolt. Its primary purpose is to enhance corrosion resistance, helping to prevent rust and extend the lifespan of the fastener, especially when used in outdoor or damp environments.

While these bolts are designed with a square neck to embed into timber, they can be used to fasten timber to metal. However, they are generally not recommended for metal-to-metal applications unless a square hole can be precisely created in the metal to accommodate the neck, which is uncommon.

While the bolt can function without one, it is highly recommended to use a washer under the nut. A washer helps distribute the clamping force over a larger area, reducing the risk of the nut biting into or damaging the material, and can help prevent loosening over time.

To choose the right length, measure the combined thickness of all materials you intend to join. The bolt should be long enough to pass through these materials and leave sufficient thread exposed to fully engage the nut and any washer you plan to use, typically an additional 5-10mm.

You will need an electric drill with an 8mm drill bit (for M8 bolts) to create the pilot hole. For tightening the nut, an appropriate spanner or wrench (typically 13mm or 14mm for an M8 nut, depending on the nut's specific size) will be necessary. A hammer or mallet can be useful for seating the bolt head.

This indicates the square neck of the bolt is not properly seated in the timber. Remove the bolt, ensure the pilot hole is correctly sized to allow the square neck to bite into the wood, and firmly tap the bolt head with a hammer until the neck is fully embedded and locked.

The pilot hole may be too small. Redrill the hole with a drill bit that matches the bolt's diameter (8mm for M8) precisely, or just slightly larger, ensuring smooth passage while still allowing the square neck to embed.

Check for damaged threads on both the bolt and the nut. Ensure you are using the correct M8 size nut. If threads are damaged, replace the affected component. Sometimes, applying a small amount of lubricant can help if the issue is stiffness, but usually, it points to thread damage or misalignment.

The timber may have compressed under the pressure of the bolt. Re-tighten the nut after a period, as timber can settle. Consider using a large washer under the nut to distribute the load more evenly and reduce timber compression, especially in softer woods.