introduction to coach screws

Coach Screws 101: Uses, Benefits, and Applications of Coach Screws

An Introduction to Coach Screws

Coach screws, also known as lag bolts or lag screws, are a type of fastener that have been in use for centuries as a reliable way of securing two or more materials together. They are most commonly found in woodworking projects but are also used in metalwork or masonry.


What is a Coach Screw?

Coach screws are a type of heavy-duty fastener characterised by their hexagonal head and coarse thread which gradually tapers to a sharp, pointed tip.

The hexagon head allows for increased torque when tightening with a spanner or socket wrench, enhancing their fastening capability.

They are typically larger and thicker than regular screws, designed for secure and sturdy connections in wood and other materials.


What are Coach Screws Used for?

They are commonly used to attach heavy fixtures, such as furniture legs, beams, or fencing, to wooden surfaces, but they can also be found in applications that connect timber to metal or concrete.

The deep threading of coach screws provides excellent grip and resistance against loosening over time, making them suitable for applications that require a strong and reliable hold.

Coach screws have a coarse thread that is designed to bite into wood or other materials to provide a strong and secure hold.

Their use dates back to the 18th century when they were first used to secure coach wheels to axles, but they were also used in the construction of bridges, boats, and other structures that required strong and durable fasteners. Their versatility has caused them to become more widely used in a range of home and garden projects as well as their traditional uses.

They come in a variety of sizes and lengths, but M6 and M12 coach screws are usually the end ranges of commonly used thread diameter sizes. M12 200mm coach screws are often the longest you available. You can find these on our website.

m12 x 200mm coach screw stainless steel

Coach screws are generally made from zinc plated steel, stainless steel, or brass, depending on their required corrosion and resistance, and aesthetic. 

Coach screws offer several advantages over other types of fasteners, making them one of the most widely used fasteners today. Due to their coarse thread, they are less likely become loose over time. This secure hold puts them in their own league from nails or regular screws. 

They are also easier to remove if needed, with their hexagonal head allowing them to be unscrewed with a spanner. This makes them ideal for temporary or adjustable installations.


Types of Coach Screws

Coach screws come in a variety of finishes which each have their specific use cases:

Steel coach screws: Generally plated with zinc to offer mild corrosion resistance, steel coach screws are durable and strong. Their main disadvantage is that although zinc plating offers some resistance to rust than their natural finish, for outdoor projects, stainless steel coach bolts are usually a better option.

Stainless steel coach screws: Stainless steel coach screws are a popular choice for outdoor and marine applications. A2 stainless steel is the most common, offering sufficient rust resistance in most climates.

A4 stainless steel is suitable for marine and salt water applications, although they are more expensive to buy so are usually only used when the use case requires it.

Stainless steel coach screws in boat

Brass coach screws: Brass coach screws are used in decorative applications, such as attaching brass hinges or handles to wooden doors or in other places around a home. They are the most prone to rusting, but they look attractive and are non-magnetic and non-conductive, making them great for electrical applications. 

When selecting a coach screw, it's important to consider the use case before deciding the material, length, and thread type. 


Choosing the Right Coach Screw

To achieve and strong and stable hold, you should choose the most appropriate type of coach screw. 

The material should be selected based on the application and environment, while the length and thread type should be selected based on the thickness of the materials being fastened together. M8 coach screws are the most common in a wide array of applications, but if you are securing heavy timber, M10 coach screws or larger could be appropriate. 

When installing coach screws, it's important to follow proper installation techniques to ensure a strong and secure hold. It is recommended that a pilot hole should be used, drilled to the correct size and depth, with the coach screw driven in straight and perpendicular to the surface.

Leaving the hexagon head of the screw exposed will allow you to remove it easily in the future. If the pilot hole is too big, not only do you risk a weak hold, but you may also bury the head and find it difficult to unscrew the bolt later.

It's important to use the correct torque and pressure when driving in the coach screw to prevent damage or breakage.


Coach Screws in Decking

Coach Screw Applications 

Coach screws are a versatile and reliable fastener that can be used in a wide range of applications in DIY and professional projects. 

Construction: Coach screws are commonly used in construction applications, such as framing, roofing, and decking. Their strong hold enables them to withstand high loads with heavy timber.

Woodworking: Coach screws are also great for general woodworking applications, such as furniture making, cabinetry, and joinery. 

Metalworking: Although slightly less common, coach screws can also be used in metalworking applications, particularly when they involve connecting metal and timber. 

Automotive: Coach screws can also be found in automotive applications, such as attaching metal brackets or other components to the body or frame of a vehicle. These are often stainless steel as they are resistant to rust and corrosion. 

Electrical: Coach screws, particularly brass ones, are used in electrical applications where a non-conductive fastener is required. As we mentioned earlier, brass coach screws are also non-magnetic.

Marine: Coach screws are used in boat building or construction at docks. A4 stainless steel can be the most appropriate as they will be exposed to salt water. 


Benefits of coach screws

Coach screws (lag bolts/lag screws) offer several benefits over other types of fasteners, making them one of the most popular bolts on the market.  

They are strong and durable (particular in larger sizes), highly versatile, and easy to install, requiring only a spanner or impact driver to secure, and are versatile for use in a wide range of DIY and professional applications..

They also provide a clean and neat finish. They can be countersunk flush to the surface of the materials being secured. This makes them great for applications where appearance is important, such as in woodworking or furniture making. 

Their coarse thread allows them to have a secure hold, while they also have self-tapping properties. Although a pilot hole is recommended, this is not always entirely necessary.  


Summing up Coach Screws

Coach screws are one of the most versatile and reliable fasteners that can be used in a wide range of applications. 

They offer several benefits over many other types of fasteners, including their strength, durability, ease of installation, versatility, clean finish, and secure hold

They are commonly used in construction, woodworking, metalworking, automotive, electrical, and marine applications. They are also a popular choice for DIY projects, small construction jobs, and heavy-duty applications, where a secure fastener is required. 

By selecting the right type of coach screw, including choosing the most appropriate material for use, and following proper installation techniques, you can ensure a strong and secure hold that will last for years to come.

You can find a wide range of stainless steel coach screws on our website.

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