What Are Carriage Bolts And What Are They Used For?

A carriage bolt features a distinctive round head and square neck that helps to prevent turning when securing materials. Whether you're a seasoned professional or a hobbyist, understanding these bolts will enhance the quality and durability of your work. 

In this post, we'll delve into everything you need to know about carriage bolts, including what they are and when to use them. 

What Is A Carriage Bolt?

A carriage bolt is a type of bolt with a rounded button head, square neck, round shank, and thread. Carriage bolts may also be referred to as coach bolts, as they were historically used to fasten metal to wood on carts, carriages, and coaches.

Carriage bolts are known for their self-locking quality, as the bolt's square neck prevents it from spinning when inserted into a pilot hole with a square slot. This unique feature eliminates the need for lock washers during installation. 

Additionally, these bolts are known to be easy to install for just one person — just a hammer and a wrench should do. 

What Are Carriage Bolts Used For?

Carriage bolts are commonly used in woodworking and carpentry projects to fasten wood to metal or more wood. However, they may also rarely be used to fasten metal to metal. 

Here's a look at the most common uses for carriage bolts:

• Woodworking Projects: Wooden furniture, decks, and playground equipment typically utilize carriage bolts because the round head provides a smooth finish that minimizes the risk of snagging or catching.

• Metal Fabrication: Carriage bolts are used in metal structures. Their square necks fit securely into pre-drilled square holes and prevent the bolt from turning while tightening the nut.

• Automotive and Trailer Assembly: Trailers and some automotive equipment are assembled using carriage bolts due to their ease of installation and strength. 

• Construction: Builders may use carriage bolts to join wood to wood or wood to metal, especially in framing and structural applications.

• Agricultural and Outdoor Equipment: Carriage bolts are used in fencing, gates, and farm machinery, and their durability helps them withstand outdoor conditions.
  
  
• Security Applications: As carriage bolts can only be removed from one side, they are used in designs where security is at the top of mind.

Types Of Carriage Bolts

There are many types of carriage bolts, including those with a zinc coating, galvanized finish, short neck, or long neck. 

Zinc-plated carriage bolts resist corrosion and have a smoother finish, but galvanized carriage bolts offer stronger corrosion and weather resistance. 

Further, galvanized carriage bolts cost more and last longer, while zinc-plated carriage bolts are cheaper, but more susceptible to damage.

Carriage bolt length should be determined based on the depth of the materials you're fastening together, while diameter should be assessed based on the joint load. 

Ultimately, the type of carriage bolt you should use depends on your project. For example, you may need shorter, zinc-plated carriage bolts for a garage shelf project and longer, galvanized carriage bolts for an outdoor fence.

What's The Difference Between Carriage Bolts And Lag Bolts?

Although similar, a lag bolt or screw differs from a carriage bolt. Lag bolts typically feature a hexagonal head and pointed tip for being driven into place, whereas carriage bolts have rounded button heads and are flat-tipped for use with nuts and washers.

What's The Difference Between Carriage Bolts and Coach Bolts?

There is no difference between carriage bolts and coach bolts; they are two names for the same bolt. The names are used interchangeably due to the historic use of these bolts in both carriages and coaches.

How To Install Carriage Bolts

Carriage bolts must always be installed into pre-drilled holes as the bolt's head does not feature a drive and must be hammered into place. Once hammered in securely, a nut and washer may be installed to the thread with a wrench. 

To remove a carriage bolt, loosen the nut and washer, but do not remove them completely. Next, hammer the threaded end of the bolt where the nut and washer are so that the head pops up and is no longer flush against the wood or material. 

Once the head pops up, you can remove the nut and washer, then use the hammer's clawed end to pull out the bolt. 

Choosing The Right Carriage Bolt

Ensuring you select a high-quality bolt suited to your project's needs is crucial for the integrity and longevity of your work. That's why it's important to turn to a trusted supplier who can provide expert guidance and reliable products. 

We are here to help you make the best choice and supply you with top-notch carriage bolts for any application. Please contact us for personalized assistance and to help the success of your next project.