Are Carriage Bolts Better Than Lag Bolts?

A carriage bolt can indeed carry more weight than a lag bolt. But that doesn’t mean we can say that a carriage bolt is better than a lag bolt. With a flat screwing structure, carriage bolts are more robust but require hassles of pre-drilling. Lag bolts are quite the opposite and have quite complimentary pros and cons.

Difference between a Carriage Bolt and a Lag Bolt

Although they are often used for a similar or interchangeable meaning, they are very different in their shape and use. Here we will talk about how they are different from each other and learn the proper use of both.

Carriage Bolt

A carriage bolt is a cylindrical bolt with a dome-shaped head. The front of the bolt is flat so it cannot be used to pierce things. So, you need to drill a hole then put the carriage bolt through it.

Since you are drilling a hole for it to pass through it will not be able to stay inside the hole. You also need a nut or washer to hold the bolt tightly in place. But once it is in place, it works as a strong joint.

But by sacrificing the piercing it gains a lot more strength to hold things. Once you install a carriage bolt it can hold thousands of tones of weight with ease. This is exactly why carriage bolt is the first choice when making anything that needs to hold a lot of weight.

Lag Bolt

The lag bolt is often called a lag screw. As for structure, it has a hexagonal head with a round neck. The end of the lag bolt is pointy. It can be drilled directly into any wood because of this. So this doesn’t need any drilling, washer, or nuts to hold it in place.

Even though it is convenient to use it is not as strong as a carriage bolt. So it is used in construction that doesn’t need to hold too much weight. But that doesn’t mean it is weak by any means. It can still hold up to hundreds of pounds of weight with some proper placement.

Both the Carriage and Lag Bolts have Their Usage

When comes to working with bolts both the lag bolt and the carriage bolt have their own use cases. The lag bolt is commonly used in normal construction like running cable in new construction while the carriage bolt is mainly used in heavy-duty construction.

Lag Bolt Use Case

The lag bolt is used for building a shed such as a garage or any other outbuilding. They are also used in making docks since they can be screwed directly to the studs. Other than that, the lag bolt is often used in making furniture, children’s wooden playground equipment, large timber constructions, and the construction of beams and doorways.

Carriage Bolt Use Case

On the other hand, carriage bolts are a great choice in supporting wood-wood or wood-metal joints. They are also used in some docks and heavy beams. As the name suggests it is always used in building carriage and sometimes in ready-made furniture and fence and outdoor decks.

The carriage bolt is also used when it comes to metal structures. Most of the heavy metal machines use carriage bolt if it is not welded together.

Sometimes Either Type of Bolt Works

From the usage, we can see that some of the usages overlap with one another. For many cases, you can use either one of them. Such as, in docks and furniture you can use the lag bolt for easy application or you can use a carriage bolt for more strength. But no matter what you use, it will work either way.

Choosing the Right Type of Bolt for Your Work

A few things you need to consider when choosing the right bolt for your work. The first thing is the application. Means, is it going to be a lightweight thing or load bearing thing? Then you can choose the bolt according to that.

A Rule of Thumb

You can also think of the two bolts like this: the carriage bolt is better for making stronger joints and for heavy-load projects. But the lag bolt is going to make the fastening even stronger. It is less strong than carriage but easier to use.

While choosing a bolt make sure to get the right side of the bolt as they differ in size. Depending on the size their load-bearing capacity also varies. So get the right size of bolt for your project.

Material of the Bolt

Another thing is the material of the bolt. Like many hardware, bolts are also graded. They can vary from grade 2 to grade 8. Usually around grade 5 can be used for everything as long as it is not an extremely heavyweight project. So make sure to get the right grade bolt.

FAQ

Are carriage bolts strong?

Ans: Yes, carriage bolts are made to withstand bigger weight and force. A grade 5 carbon steel carriage bolt has 150 thousand psi of tensile strength.

Are carriage bolts stronger than lag bolts?

Ans: In terms of weight-bearing capacity, carriage bolts are strong than lag bolts. But both have their unique use cases.

How much weight a lag bolt can hold?

Ans: A 3/8 inch lag bolt can hold almost 200 pounds of weight per inch.

Do lag bolts need a washer?

Ans: No, the lag bolt has a pointy tip. So you can drill it directly to the joint and it will hold the joint. Thus there is no need to use a washer.

Conclusion

When evaluating the suitability of carriage bolts and lag screws for your project, consider the specific requirements of your construction projects. Carriage bolts, also known as coach bolts, offer a unique combination of a square neck and round head, making them ideal for heavy duty fasteners in applications where movement or stress could cause traditional bolts to loosen. Most carriage bolts are made from high quality fasteners like stainless steel or hot-dipped galvanized steel, ensuring durability and resistance to corrosion. These bolts excel on concrete surfaces and in structural hardware applications, where the flat tip and pre-drilled hole design provide a secure, stable fit.

Lag screws, on the other hand, are versatile structural screws with a pointed tip, allowing for easy installation without the need for a pilot hole. They are commonly used in wood construction, offering a strong hold when pre-drilled holes are not feasible. Although not as robust as carriage bolts in load-bearing applications, lag screws are an excellent choice for lighter construction projects. In summary, while both types of fasteners have their unique advantages, the choice between a bolt vs carriage or lag screw ultimately depends on the specific requirements of your project, whether it’s the need for plow bolts, the nature of the materials involved, or the environmental conditions to which the fasteners will be exposed.