What are the differences between Bolts, Nuts, and Screws?

Fasteners are critical components found in a myriad of industrial operations, ranging from marine and medical to aerospace and aviation applications. Bolts, nuts, and screws are just three classes of fasteners, each of which serve different roles. While they may look similar in appearance, bolts, nuts, and screws vary in many aspects. With this in mind, we will be taking a look at those particular distinctions and the functions such fasteners serve.

As these fastening components are often conflated with one another, we will outline each one’s unique features. Beginning with bolts, these unique components are equipped with a threaded shaft. Bolts are typically used when you seek to join two parts of a given material. By aligning the pilot holes in the material and inserting a bolt, you can generate a tight seal.

What makes bolts so special is their holding strength. The threads of the bolts are what provide them with an unparalleled level of holding power. However, they cannot achieve this alone. Bolts require washers or nuts to be installed. The washer or nut can help distribute the loads being placed on the assembly while also reducing friction. Furthermore, there are a wide range of bolts to choose from, some of which include anchor bolts, hex bolts, carriage bolts, u-bolts, and more.

Anchor bolts allow you to attach objects to concrete. First, you must place the bolt head in the concrete before it completely cures, allowing the threading head of the bolt to be visible. Hex bolts, on the other hand, are the most widely used variety and are available in many metric sizes. Next, carriage bolts are defined by their smooth rounded head and square section that prevents the bolt from turning. U-bolts, as their name suggests, are in the shape of a “U” and possess a threaded section on each end.

Used alone or in conjunction with other fasteners like bolts and screws, nuts offer increased holding power and prevent axial movement. For instance, nuts have a threaded hole wherein you can insert a bolt. While the bolt’s shaft prevents radial movement, the bolt’s head and the nut eliminate axial motion. Like bolts, there are many nut types, each varying in thread pattern, material, size, and shape. As such, we will go over the most common, some of which include locknuts, wheel nuts, hex nuts, and flange nuts.

To begin, locknuts are typically used to secure other nuts by preventing them from loosening over time. Meanwhile, wheel nuts are exclusively used in automotive applications. Hex nuts are hexagonal in design and require a wrench for installation. Lastly, flange nuts feature a flange and act as external washers, providing additional load distribution.

The last fastener that will be covered is the screw. Containing a threaded shaft, screws can be fastened into most materials with ease. They are commonly available as self-tapping and wood screws, and they consist of a sharp point that can be used to cut into a material. Similar to their counterparts, screws are made in varying designs to suit a diverse set of applications.

Wood screws are the first type which are not actually made of wood, but are intended to join two or more wooden parts. Lag screws, also called coach bolts or lag bolts, are jumbo-sized and coated in zinc to prevent rusting and corrosion. The last type is a twinfast screw which is of the self-tapping variety with two threads instead of one.

While we have defined the difference between bolts, nuts, and screws, it is important to note the particular distinctions between bolts and screws. These two are typically confused for one another, though they have varying characteristics. Bolts are reliable fasteners that lack a tapered shank, but contain a spiral thread structure. Not nearly as reliable as bolts, screws are only available as small or medium-sized components, and they are not as durable. Furthermore, screws have a pointed shank and helical structure threads.

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