Although sounding similar, coach bolts and coach crews are two different fasteners. In fact, they have different uses and are not used interchangeably. It is also important to understand the confusing terminology surrounding these fasteners. For example, coach bolts are often referred to as carriage bolts and coach screws are also known as lag screws or lag bolts. Read on as we highlight the key differences and explain uses of these fasteners.
Coach Bolts
Coach bolts are a fixing with a unique design, used mostly for timber-to-timber applications. The rounded head with the square underneath enables the user to tighten the bolt whilst the square restricts the bolt from turning. This is particularly useful in scenarios where only one side of the carriage bolt is fully accessible. Regarding fastening, coach bolts need a slightly larger hole diameter due to their dowel shaft design. They also need a nut and washer (usually a square plate washer) to ensure they are securely fastened.
Types of coach bolts
Carriage bolts can come in a range of materials and finishes that differ in price and durability. Zinc plated coach bolts are usually the cheapest option. This is largely due to other bolts providing greater protection. Despite this, they are still widely used for indoor applications.
Galvanised coach bolts are also a zinc coated fastening. They feature a thicker coating and therefore offer further protection. Due to this, they are commonly used in outdoor applications. Examples of this include fencing or building work where the carriage bolts are out in the elements.
The most durable option is the stainless steel coach bolt. Manufactured from steel and chromium, the product is resistant to corrosion. This makes the carriage bolt the best-suited for outdoor applications as a long-lasting fixing and for applications where oak timbers are used.
Coach Screws
Like coach bolts, coach screws (also known as lag screws and lag bolts) are a fixing commonly used for timber-to-timber applications. You can also fix them into nylon wall plugs for masonry. The lag screws differ from the coach bolts as they do have a tapered shaft. This allows you to fasten them straight into the wood without a pilot hole. Despite this, it is common practice to use a pilot hole to reduce the risk of wood splitting and also less strain on the shaft. Another top tip to remember – ensure you use a washer. This will restrict you from overdriving the screw when using timber.
Types of coach screws
Again, like carriage bolts, coach screws come in a wide range of types, including size, material and finish. Passivated zinc plated coach screws can offer further corrosion resistance. They do feature a high-shine finish, which is ideal for designs where the screws are clearly visible.
Galvanised coached screws are zinc coated and are often a low-cost option. Their increased levels of zinc coating provides a higher layer of protection against corrosion. This makes them suitable for outdoor use when exposed to the elements. The galvanised lag bolts have a wide range of uses across the automotive and construction industry.
Stainless steel coach screws provide the benefit that is synonymous with stainless steel. The metal’s composition is resistant to corrosion and highly durable. This makes it a long-lasting option where the fastening is likely to remain outside.
How to choose which coach screw or coach bolt to use
It is important to fasten the coach screw and coach bolt based on the recommended methods. You should choose from the range of materials and finishes with the project in mind. For example, you need to consider durability, cost, and aesthetics when making your selection.
At Tradefix Direct, we have a wide range of coach screws and coach bolts available. You can browse our selection of products online. We stock leading brands such as the range of Timco Coach Screws. For more help with choosing the right product, get in touch today. All orders over £60 get free next day delivery!