Carriage Bolt vs. Hex Bolt: Which to Choose?

Carriage Bolt vs. Hex Bolt: Which to Choose?

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Do you know a hex bolt from a carriage bolt? Sometimes it can be difficult to tell the difference between fasteners. But with a bit of more understanding, you’ll know all about the two.

This article will cover the basics of both types of bolts and explain the right situations to use them.

Carriage and Hex Bolts: The Basics

Before jumping into their differences, let’s start by taking a look at each of the bolts.

What Is a Carriage Bolt?

Carriage Bolt A carriage bolt joins two components together. This is done by pulling one into the other, as a nut tightens over a thread on the neck of the bolt. A carriage bolt has a few distinct features that separate it from the other types of bolts including the hex bolt.

Firstly, the head of the carriage bolt is rounded, creating a side profile that looks similar to a mushroom. The underside of the head is flat and sits flush on the face of one component.

The neck is attached to the underside of the head. In the most common types of carriage bolts, the neck is square where it first begins. This square shape then rounds into a circle for the thread of the bolt to start.

What Is a Hex Bolt?

Hex Bolt A hex bolt is what most people imagine when they think of a bolt. The shape of its head gives the bolt its name. The head has six sides and is hexagonal, hence the name hex bolt.

Hex bolts can be used in a range of situations and with multiple materials. When combined with an anchor, they are a great way to solidly fix into masonry and rock.

Similarities of Carriage Bolts and Hex Bolts

Now, let’s take a look at the similarities between the two bolts.

1. Fastening Mechanics

Both bolts use the same mechanics to fix components together.

A bolt works like a clamp, the pressure created from the nut tightening squeezes the two components together. Both hex bolts and carriage bolts work like this.

2. Material They Are Constructed From

Carriage bolts and hex bolts are manufactured in a range of different materials. Stainless steel and steel are the most common. Out of these two, stainless steel is stronger and more resistant to rust.

3. Installation Requirements

Both bolts require a similar process for installation. A hole must be marked out, drilled, and the bolt inserted through

The only difference is that a hex bolt can be tightened from both ends, whereas a carriage bolt can only be tightened by the nut.

Differences Between Carriage Bolts and Hex Bolts

While they are largely similar, the two have important differences.

1. Design of Head

The head of the two bolts is very different. The carriage bolt has a smoother, rounder low profile head. It also has a larger circumference compared to the hex bolt head. Lastly, the carriage screw has a square neck, where the head and neck meet. This is to stop the bolt from turning at that end.

The hex bolt does not have this design.

2. Tightening Points

The carriage bolt is tightened and loosened from one end. In comparison, the hex bolt is tightened and loosened from both ends.

3. Applications

Some situations are better to use carriage bolts, others hex screws. This will be covered more in the next section.

Carriage Bolts vs. Hex Bolts: Which Should You Use?

Both bolts can do a lot of the same jobs. However, the design of each bolt’s head means that there are some situations where one is better than the other:

  • If you have limited space and only one side of a component can be accessed to tighten, use a carriage bolt.
  • If you want to put a bolt into masonry or stone, you will need a hex screw. This is because the smooth head of a carriage bolt won’t let you tighten the bolt from the accessible side.
  • If the project was to create a child’s climbing frame, for example, the carriage bolt would be better suited because the smoother head is less dangerous.

Alternatives to Carriage and Hex Bolts

There are a lot of different fixtures and fittings in the world. They have all been created for specific purposes. So, depending on the job, there could be a better alternative to carriage and hex bolts.

Here are just two examples:

  • Screws: Screws come in a variety of shapes and sizes. They are usually quicker to use, smaller in diameter, and cheaper than bolts.
  • Draw-bore pegs: This is a traditional joinery technique, used in wood, to lock two joints together. If you cut a mortise and tenon, you would drill a hole through one component, and offset that hole slightly in the next component. Then you would hammer a hardwood peg into the hole. Because the holes are offset, the peg pulls the joint even tighter together.

Summary

The carriage bolt and hex bolt share a lot of similar properties. This means that there are a lot of jobs that both bolts could safely do. However, the key differences in their design means that, for some tasks, one is better suited than the other.

The key defining features that would mean choosing one of these bolts over the other are space, access, and safety.