Threaded Fasteners

Threaded Fasteners - Screws

The 21st century marks the advent of advancement in information technology as well as improvements in physical science, robotics and communication mechanisms all over the world. From the fastest ever automobile to have been created to the smartest phone, we have witnessed it all.

Much can be written about the methods via which these machines have been intricately packaged. Hundreds, if not thousands of small parts are assembled to give us our favourite machines. These include power-producing machines, industrial machines, electrical appliances, household appliances, vehicles; basically every vital big and small machinery we see around us that help us carry out our day to day activities with ease and comfort.

But What Holds These Machines Together?

Most of the objects we see around us are made of several parts joined together to give the final product. There are various ways to join parts together, from the simple and often temporary use of adhesive agents to the more advanced methods of welding or using mechanical fasteners.

Even though welding is common and considered as a permanent method to attach pieces together, the weld may need continual replacement and the joint may weaken in time due to the stresses it has to withstand. Due to this, mechanical fasteners have become a popular option for connecting pieces together.

Most Commonly Used Threaded Fasteners

Mechanical fasteners can be divided into two broad categories, namely non-permanent fasteners and permanent fasteners. Furthermore, non-permanent fasteners can be further broken down into sub categories of general fasteners and threaded fasteners.

The most commonly used non-permanent fasteners are threaded fasteners. This is because a joint formed via threaded fasteners is reversible, i.e. they can easily be disassembled and reused for further applications.

Another important attribute that distinguishes a threaded fastener from its non-threaded counterpart is its strength. The customary way of creating threads onto fasteners is via the use of a lathe machine, which is used to cut grooves onto the material that will be used in the manufacture of the fastener. Upon hardening, these cut parts enhance the mechanical strength of the material, making it stronger.

Thread rolling is another process which is used to make a threaded fastener. The resulting rolled threads from a thread rolling process are much stronger than the cut threads from the lathe machine. This is because the thread rolling process results in favourable stresses on the surface of the fastener material that makes it less likely to break and more likely to withstand forces. (Thomasnet.com, 2018)

Main Types of Threaded Fasteners

There are three main types of threaded fasteners, namely bolts, screws and studs.

Bolts

are used in conjunction with a nut and comprises of a head on one end and threads on the other. Bolts can be broadly classified into two categories – round head bolts and wrench head bolts. Round head bolts are used in conjunction with a square nut while wrench head bolt heads can be of square and hexagonal forms.

Screws

are very similar to bolts in that they also have a head on one end with threads on the opposite end. The only difference arises in the length of the threads. Screws usually have longer threads than bolts and thus can be made with slotted heads. The head is intricately shaped in order for screwdrivers or wrenches to have a firm grip when driving the screw in. Screws facilitate the positioning of things and are also fundamentally used to hold pieces together – for example wood.

Screws can be broken down into two categories – cap screws and machine screws. Machine screws are predominantly used for screwing into thin materials as they are comparatively smaller in size than cap screws.

Studs

are rods that are used to adjoin two mating parts and are threaded on both ends. (Kau.edu.sa, 2018)

Illustration of Threaded Fasteners - a Screw, a Bolt and a Nut

Figure 1: Illustration of a Screw, Bolt and a Nut (Agcoauto.com, 2018)

These tiny fasteners are used in millions of applications around the world. They are hugely advantageous to us as they hold integral systems and machines together, allowing them to function desirably and profitably.

Threaded fasteners are considered the most important category when considering mechanical assembly. They are often used immensely in a single application and therefore the ability to dissemble the fasteners readily is a great advantage. These fasteners are also cost effective and widely available in a variety of sizes for different applications.

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