What Is a Carriage Bolt?
A carriage bolt is a type of fastener which is designed to be used with wood, although specialized versions can be used to fasten metal components. Also known as plow bolts or coach bolts, carriage bolts are very common, and can be found in many hardware stores in an assortment of sizes. People can also order specialty versions directly from manufacturers, if they have a need of a specific kind for a particular project. Carriage bolts are also handy to keep around the house, for people who like to maintain a basic supply of useful tools and equipment for repair jobs and other tasks.
The design of a carriage bolt includes a round head with an externally threaded bolt projecting from it. Underneath the head, a square fitting is mounted. This fitting grips the wood as the bolt is placed and fastened, keeping the bolt from twisting or turning and maintaining a snug, smooth fit. In a variation on the basic carriage bolt, the square fitting is replaced with ribbing which is used to hold the bolt in place when it is used with other metal components.
Like other bolts, the carriage bolt is designed to be used with a nut which is used to fasten the bolt and secure it in place. The nut can be hand tightened for a reasonably snug fit, or tightened with the assistance of a hand tool which will lock the carriage bolt in place, ensuring that it cannot move. Specialized versions may be made from metals which resist corrosion so that they can be used in wet environments or environments where corrosive chemicals are utilized.
Carriage bolts are typically placed into predrilled holes. It is important to select a bolt of the right width for an application; if the bolt is too narrow, the fastening may fail under strain, causing an object to break. If the carriage bolt is too big, it can stress the surrounding wood or metal, causing cracks. Length is also important, as the bolt must be long enough to go through the material being fastened, but not so long that the protruding end becomes a nuisance.
Many pieces of flatpack furniture come with carriage bolts which people can use the bolt the furniture together. These bolts may be accompanied with a small wrench for fastening the nuts, or people may need to use a wrench of their own. It is a good idea to make a habit of counting fasteners before assembling furniture, to confirm that everything needed is present.
Written by S.E. Smith
