Difference Between a Bolt a Screw and a Stud

Bolts, screws, and studs are commonly known fasteners. They are used mainly in the manufacturing industry. They all serve different functions and have various shapes and appearances. Here we are trying to understand the difference between a bolt a screw and a stud.

How do you think your car wheels are attached to the body of your car? That’s right! Screws, bolts and studs. These are the most commonly used items, but we hardly pay any attention to them while benefiting a lot from these innocuously small looking devices.

The differences between these three fasteners will be highlighted and discussed below.

Screws

A screw can be defined as an inclined plane wrapped around a nail and characterized by a helical ridge. In other words it is a long metal shaft with threads circling along its length. It has also a turning where a screwdriver can be used to rotate the screw.

A screw generally has a head with specially formed shape. Head size and shape determines the size of the tool to be used to turn or drive the screw. Common used tools are wrenches and screwdrivers.

The underside part of the head is a shank which may be fully or partially threaded. A screw thread is a structure on cylindrical or coned shape in the form of a helix. The top of the ridge is called a crest and the bottom a root. The distance between the crest of the one thread to the next one is called a pitch.

Screws are tightened by rotating the tool clockwise or anticlockwise and are usually used for joining materials that do not have existing holes in them. Most common types of screws used in manufacturing are: concrete screws, dowel screws, drywall screws and mirror screws.

The strength of a screw relies on the width of the thread and the distance between them. However, the more numbers of the threads, the more rotations would be required to attach the screw. Also, if the distance between consecutive thread is wider, more force must be exerted on the tool  in the rotations.

Screws are widely used in many applications. From furniture to motorcycles, from air conditioners to kid’s remote control cars.

Bolts

A bolt is an external threaded fastener created for the insertion through holes in the assembled parts. Generally, bolts are intended to be tightened or released by nuts.

Generally, bolts have a uniform circular cross-section, the threads are spiral in structure and have smaller pitch as compared to screws and studs.

Unlike screws, bolts do not have tapered shanks and the parts secured by bolts possess greater strength than parts secured by screws. Bolts act on the application together with the nut and are tightened on the part in which the torque is applied.

Some of the commonly used bolts are: carriage bolts, plow bolts and track bolts. The reliability and durability of parts joined by bolts is much higher than joined by screws.

Applications that use bolts include flange joints or fastening of objects made of metal materials. Moreover, bolts are not only used in machinery but also in plumbing and electronics. Bolts are integral part of equipment and component reliability.

Studs

A stud is a metal rod or shaft with threads on both sides. Usually the rod is longer but depending upon the requirement the size can vary. A stud is an external threaded headless fastener. In other words we can say that one end of the stud is connected to the tapering part and the other end to the standard nut.

Unlike screws and bolts, studs do not have the heads that require tightening. While installing studs they don’t require any external force to torque it down and one is able to install studs manually.

Studs are relatively larger than bolts and screws, thus they go much deeper inside the threaded hole of the connected application and are actually going close to the portion of the thread that have not torque applied to them.

Screws and bolts have two forces applied on them: rotational force and linear force which would give an inaccurate torque reading. Studs have no rotational force applied, hence we can get more accurate reading.

Studs are categorized into three main types: fully threaded stud bolts, tap end stud bolts, and double end stud bolts. Depending upon the application studs are made from various materials to satisfy the operation requirements. Since there’s no stretching in the threads of the studs they are able to produce repeatable clamping force, thus lasting longer.

Studs are often used for fastening flanges. The quality of flange for connections is determined by the holes in the flange diameter and length of the studs is determined by the flange type and pressure class.

Studs prevent leakage of fluids through holes in machines. They are also used in the assembling of heavy materials such as turbines, tanks, cylindrical heads and gaskets.

Bottom Line – Difference Between a Bolt a Screw and a Stud

It is important to note that each of these have their different purpose and you should identify which would work best for the project you choose. Also, make sure you know the strength and material the bolt, the screw or the stud is made of before you choose to use it on a project. It is necessary to consider how it would impact or enhance the overall performance of a project before choosing it.

References

• Sme.org. (2018). Threading. [online] Available at: https://www.sme.org/WorkArea/DownloadAsset.aspx?id=73766 [Accessed 20 Apr. 2018].
• Smartbolts.com. (2018). Fundamentals of Basic Bolting. [online] Available at: http://www.smartbolts.com/fundamentals/ [Accessed 20 Apr. 2018].