Q&A: Carriage Bolt

Carriage Bolts

What exactly IS a carriage bolt?

Carriage bolts are an application specific fastener designed for use in carpentry, wood base materials and the construction of wood products. They get their name from their original purpose, which was in the construction of carriages and carriage wheels back in the early 1800s. They are easily identified by a dome shaped head and typically a square shaped neck although through the years several varieties now exist with other head and neck styles available.

Who would typically use a carriage bolt?

Carriage bolts are extremely common and their uses are so varied that most people have probably seen or used one at some point. Anyone involved in carpentry or wood construction will rely on carriage bolts frequently. Homeowners and DIYers will also frequently use carriage bolts in your typical home maintenance or repair project because they are so handy for use in wood. Because of their domed shaped head, carriage bolts offer a smooth, aesthetic appeal and provide some level of safety in backyard play equipment, wood decking, ornamental fencing as well as most styles of wood furniture.

At FMW Fasteners, how are carriage bolts sold?

At FMW we offer several different styles of carriage bolts and we sell them in any quantity you like. You can purchase sizes individually or in bulk. Currently we offer 4 different discount levels so that customers can take advantage of purchasing in bulk and even varying degrees of bulk. We don’t require someone to purchase 100 pieces or any type of minimum when they may only need 3 or 4 pieces for their specific application.

What different types of carriage bolts are there?

Over the years manufacturers have produced many different styles based on customer demand and specific applications. Dome or round head are the most common but flat head exist as well as with no neck, ribbed neck fins and short square neck versions. We currently offer carriage bolts in A307 Grade A (low carbon steel), Grade 5 (medium carbon steel) and 304 (18-8) stainless steel. All of our carriage bolt patterns are the standard dome or round head with a square neck above the shank. We offer A307 Grade A carriage bolts in both zinc and hot dipped galvanized platings.

How long has FMW Fasteners been selling carriage bolts?

Because carriage bolts are such a common product with such a wide range of uses, FMW Fasteners has been selling carriage bolts since the company was started in 1986. So the current inventory we offer as well as the styles we carry are based on 29 years of history with these products.

Are there any particular things to consider when using carriage bolts?

Two major things to always consider with carriage bolts are the environment in which they will be in service and the thread length requirements considering that the square neck takes up a certain portion of the shank. We always recommend hot dip galvanized or stainless steel carriage bolts for exterior applications, particularly here on the Texas Gulf Coast. When calculating the amount of shank needed to achieve a certain amount of thread pattern it’s also handy to note that our carriage bolts are fully threaded up to 6 inches. Any bolts with a shank longer than 6 inches will have 6 inches of thread. This makes calculating thread requirements on the fly easy as you can assume you will always have 6 inches of thread on the bolt. Wood species for pilot hole requirements is another one where you should always consider soft wood vs hard wood before pre-drilling for your carriage bolts.


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