Coach Bolts

What Are Coach Bolts?

Coach bolts, also known as carriage bolts or cup square hex bolts, are highly versatile fasteners renowned for their strength and reliability. They feature a round, smooth head with a square shoulder beneath it, which prevents the bolt from turning when tightened. This feature makes coach bolts ideal for high-torque applications and ensures that the bolt stays securely in place, even under pressure. 

Typically, coach bolts are used to fasten wood to wood, metal to wood, or metal to metal, making them a go-to choice for a variety of projects. Although originally designed to be paired with square plate washers, many modern coach bolts can now be used independently.

These fasteners are widely employed in the construction industry, as well as for both small DIY projects and heavy duty industrial applications.

How Do Coach Bolts Work?

Coach bolts are installed by inserting the bolt through pre-drilled holes in the materials that need to be joined. The rounded head typically sits flush against the surface of the material, while the square shoulder beneath the head grips into the material to prevent the bolt from rotating when tightened. A nut is then threaded onto the bolt's shaft, and the bolt is tightened with a wrench. The square shoulder locks into place, and the nut secures the connection

Where Are Coach Bolts Used?

Coach bolts are essential for securing structural elements. These bolts are perfect for joining timber, metal, and other building materials, particularly when the materials require high-strength connections to withstand load-bearing stresses.

Coach bolts, especially when made from zinc-plated materials for added durability, are frequently used in timber projects. They provide a strong and reliable fastening solution for:

• Decking and fencing installations.
• Assembling garden furniture.
• Attaching metal brackets to wooden beams.

For assembling heavy furniture pieces, cup square bolts or coach screws are commonly used to ensure the pieces are tightly held together. This includes applications in:

• Metal bed frames.
• Large storage units.
• Office furniture.
  
  

Key Features of Coach Bolts

• Round Head: The top is dome-shaped, offering a smooth finish.
• Square Shoulder: This feature ensures the bolt doesn’t turn once it’s installed.
• Threaded Shaft: The shaft is threaded for secure attachment to nuts or directly into the material.
  
  

Types of Coach Bolts

Coach bolts come in various types, each suited for specific applications. Understanding the different variations can help you select the right bolt for your needs.

Standard Coach Bolts

These are the most commonly used types of coach bolts. They are designed with a smooth, round head and a square neck. These bolts are ideal for general use and offer a high level of strength.

Stainless Steel Coach Bolts

Made from stainless steel, these bolts are resistant to rust and corrosion, making them ideal for outdoor and marine environments where moisture exposure is common.

Galvanised Coach Bolts

Galvanised bolts are coated with a layer of zinc to provide enhanced corrosion resistance. These are perfect for outdoor applications where the bolts are exposed to the elements but don’t necessarily require the higher performance of stainless steel.

Long-Shank Coach Bolts

Long-shank coach bolts are designed with extended shafts, allowing for the fastening of thicker materials. They are ideal for securing items that require extra reach or for fastening items in deep wooden structures.

Tips for Using Coach Bolts Effectively

To get the most out of your coach bolts, keep these tips in mind:

• Use Washers: When fastening the bolts to wood or other soft materials, it’s essential to use a washer to distribute the load evenly and prevent the material from getting damaged.
• Pre-drill Holes: Always pre-drill the hole to ensure the coach bolt can be inserted easily, especially when working with hard materials like metal or thick wood.
• Select the Right Size: Choose the correct bolt size for your project. Using a bolt that is too long or too short can affect the stability of the connection.
• Ensure Proper Threading: Make sure the threads are aligned properly during installation to avoid damaging the bolt or nut.
• Use Anti-Corrosion Coating: For outdoor use, opt for galvanised or stainless steel coach bolts to prevent rust and corrosion.