Carriage Bolts

What Are Carriage Bolts?

Carriage bolts, sometimes wrongly referred to as carriage screws, have a round head, a square neck and machine threads. Carriage bolts have a round head that gives a wide load-bearing surface (without the need for washers) as well as a finished appearance when installed. The square neck on the carriage bolts is designed to fit snugly into the mating material so that it prevents the bolt from spinning during the tightening of the nut. More info

Why Use Carriage Bolts

Carriage Bolts offer a high level of security when securely fastened if access to the nut is not possible, making these screws the go-to choice for garage barn doors and all other entry points. Adding a washer on the nut side is advisable for improved fastening and holding power when joining pieces of wood together. To ensure a snug fit between two metal components, the hole in which the fastener passes through must have an identical size to the square shank.

Carriage Bolts - Key Features

While they may seem similar to many other nut and bolt combinations, carriage bolts have a few distinguishing factors that set them apart:

A Flat Head

Because these bolts have a completely flat head, they are essentially tamperproof when the nut is inaccessible. With hex nuts, lag nuts, and most types of screws, people can turn the nut from outside since the head is either shaped like a nut or has some other means of adjustment (Phillips head, flat head, etc.)

A Square Neck

Carriage bolts have a unique shape, with a square-shaped neck beneath the flat head. Once this square neck is securely seated within a socket of the same size and shape, the bolt is immovable. Not only does this make fastening easier, but it adds to the security of the carriage bolt and nut.

Immense Strength

Carriage bolts, or coach bolts, are heavy-duty bolts designed to work well continuously. They generally have thick shafts and are made from durable materials like galvanized or stainless steel, making them nearly impervious to rust. In fact, carriage bolts are so strong that they were originally used to build carriages and carriage wheels, which is where they get their name.

Machine Threads Down Part of the Length

Carriage bolts have machined threads down a part of their length, meaning that the smooth part slips into place, and you can then secure the nut on the other side.

Frequently Asked Questions About Carriage Bolts

Which materials do carriage bolts and nuts come in?

When buying carriage bolts, you can choose between galvanized steel, stainless steel 316, or stainless steel 18-8.

What is the difference between a carriage bolt and a coach bolt?

Carriage bolts are another name for coach bolts, and in some places they may be used interchangeably. In other words, if you're looking for a ¼”-20 coach bolt, you can buy a ¼”-20 carriage bolt.

What is the difference between a lag bolt and a carriage bolt

Lag bolts are used for woodworking and have a pointed tip. Carriage bolts have a flat tip and are used when you need to ensure that the bolt is completely immovable after fastening.