All About Construction Carriage Bolts and Fasteners

A carriage bolt is a threaded fastener for use in securing wood. This type of fastener is also referred to as a plow bolt or a coach bolt. They are available in a variety of diameters, thread pitches and lengths and are typically composed of steel, stainless steel or zinc-plated steel.

What Are Common Carriage Bolt Uses?
Carriage bolts are typically used to fasten wood through holes already drilled into the beam. They can also be used to fasten two pieces of metal together. This type of bolt is found in the wooden beams used to construct a home, furniture that is ready to assemble, in outdoor decks and even in automobiles.

What Are Standard Carriage Bolt Dimensions?
Carriage bolts are available in a wide range of sizes for use in different applications and thicknesses of wood. Typical carriage bolt sizes are diameters of 0.25 to 0.75 inches with lengths ranging from 0.75 inches to 10 inches. The threading typically encompasses half the length of the bolt plus an additional half-inch.

What Is Typical Carriage Bolt Strength?
The strength of carriage bolts depends on the material they are composed of and the length and diameter of the bolt shaft and head. Carriage bolts made of stainless steel have a tensile strength of 85,000 psi and a shear strength of up to 35,000 psi. Careful sizing of carriage bolts is essential as too narrow a diameter can cause failure of the fastening of materials while too wide of a diameter can put undue stress upon the wood timbers or metal components.

When Is a Carriage Bolt Washer Needed?
The large size of the heads of carriage bolts mean that washers are not an essential part of the installation process. However, using washers when installing carriage bolts does help to evenly distribute the load and can help to minimize friction and vibration between the two materials.

What Is the Difference Between Carriage Bolts and Lag Bolts?
Carriage bolts and lag bolts are shaped differently and require different installation procedures. A carriage bolt is wide and flat on the bottom and has narrow threads while a lag bolt is pointed at the bottom and has wide threads. Lag bolts do not require the use of an already drilled hole in the materials to be fastened together, which allows for added strength in the connection between the two timbers or metal components.

Construction crews and home do-it-yourself gurus have a wide variety of fasteners to choose from when undertaking a project. In general, when one material needs to be secured to something much larger, such as a deck to the back of a house, lag bolts are used, and when two materials of a similar size are being attached, such as timbers for a child’s swing set, carriage bolts are the fastener of choice. No matter what bolts you need, for example eye bolts, we carry thousands of in-stock options and can custom fabricate special sizes.

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