Today in industries, appliances of any materials are often joined using fasteners so that clean and strong joints can be produced. Other alternative methods of material joining include welding, soldering, brazing, gluing, etc. will permanently join material. This is why most fasteners serve better as the joint can be removed and dismantled without damaging the joining components, although some fasteners like rivet bonds permanently. Except that the rivet itself will be destroyed for the joint to be dismantled.
Today you’ll get to know the definition, applications, functions, materials, and types of mechanical fasteners. You’ll also get to know the advantages and disadvantages of these fasteners over the permanent joining process.
What is a fastener?
A fastener is a device that mechanically joins two or more objects together. Normally, fasteners can be permanent or non-permanent but are often used to create non-permanent joints. This allows the joints to be dismantled or removed without damaging the joined parts. Other joining processes like welding create a permanent joint.
Fasteners are used in different fields such as metalworking and woodworking. Employing fasteners as a joining process in this field has made life easy in many ways which will be further stated. Metal fasteners must be strong and be able to bear significant loads. They are often manufactured using powder metallurgical and casting processes.
Threaded fasteners are the most widely and commonly used for assembling parts because they offer ease in installing and uninstalling as required. Fastener threads are standardized to two major standards: ISO (Metric) and ANSI (Unified). Their threads can also be right-handed or left-handed, depending on the application, but the majority are right-hand threaded. The threaded fastener is of three main types; bolts, screws, and studs.
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Applications of fasteners
Applications of fasteners are common today since it offers a greater benefit over other joining processes. In fact, almost all industrial applications can be design to use fasteners only that some factors must be considered. Things to considered include:
- Applied load on the fastener
- Stiffness of the fastener
- Also, the number of fasteners required must be taken into account.
When choosing a fastener for a given application, some things must also be put into consideration. These include:
- Installation process
- Environment occurrence such as temperature, potentially corrosive elements, and water exposure.
- Weight restrictions
- Materials to be joined
Common applications of fasteners around us include chairs, tables, stools, doors, windows, kitchen utensils, electrical devices, etc. Broad use of fastener are automotive industries, aviation, agricultural equipment, marines, etc. in fact, anywhere equipment is dealt with fasteners are always put into consideration.
Just as earlier stated, powder metallurgical or casting are the common techniques for manufacturing fasteners. Fasteners are commonly made with steel. The major used steel fasteners in industries are carbon steel, stainless steel, and alloy steel. Stainless steel fasteners are used in three grade 200 series, 300 series, and 400 series.
Some other materials such as titanium, aluminum, and various alloys are also used for the construction of metal fasteners. In most cases, special coatings or plating may be applied to metal fasteners to increase their performance characteristics, for instance, enhancing corrosion resistance. Zinc, chrome, and hot-dip galvanizing are common coating/plating perform on fasteners. Although, iron is a constituent of most fasteners.
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Types of fasteners
Below are the common types of fastener and their descriptions.
A threaded fastener has internal and external screw threads. Screws, nuts, and bolts are common types of threaded fasteners out there.
Bolts – have a head on one end, usually a hex head, and are threaded on the other. Bolts are generally used in conjunction with a nut and sometimes with a washer to hold them in place.
Screws – are similar to bolts because they also have a head on one end and a thread on the other. Screws are usually used to screw into an internally threaded hole. Cap screws, machine screws, and woodscrews are the different types of screws available.
Studs – in this case, studs are threaded on both ends, and therefore have no end. They are also used to join components with internally threaded holes together. However, two parts are joined in this case.
Nuts are used in conjunction with a bolt to clamp two or more parts together. Common types of nuts include:
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Hex nuts – is a plain, hexagonal nut with an internal thread. It is the most common type of nut and is used in numerous applications.
Locknuts – these types of fasteners are used when the nut needs to be locked in place without clamping onto another object.
Nylon insert nuts – have hexagonal-shaped nuts have a nylon insert which prevents the nut from losing due to vibration.
Shear nuts – these types of fasteners are cone-shaped nuts with a hexagonal gripping point that snaps off when the maximum torque has been reached. These nuts are difficult to remove.
Wingnuts – feature two external wings that allow manual turning. They are commonly used in applications where the nut will be regularly removed.
Washers are types of fasteners used between the had of a bolt, screw, and nut to clamp material together. Their primary purpose is to increase the bearing area of the head and also protecting the material underneath from damage. Below are the different types of washer and their uses.
Flat washers – are the most common types of washers and are used to evenly distribute the bolt, screw, and nut load as the fastener is tightened.
Cup washers – is in form of a cup so that the head of the fastener can fit in. these create a flush finish with the fastener head, it is used in conjunction with a wood screw.
Spring washers – these types of fasteners are also known as locking washer because it stops the bolt, screw or nut from vibrating loose.
Repair washers – also referred to as penny washers or fender washers. They are designed to create a greater bearing surface and prevent pull-through. These fastener types feature a small inside diameter.
Just as earlier mentioned, rivets are permanent fasteners, that is, when removed, they cannot be re-used. Rivets are used in some industries and for some special applications. However, they are commonly used to join metal sheets and plates.
Pop rivets – these types of fasteners consist of hats and mandrels. They are used to join two materials together. In its working, the mandrel is forced into the rivet body, forcing the body to expand and grip onto the material. The remaining mandrel snaps off as soon as it’s gripped.
Large flange pop rivets – are similar to pop rivets in their application but features a larger flange.
Multi-grip rivets – these types of fasteners are used when joining materials with different thicknesses. Normally, the materials will be required multiple rivet sizes. Multi-grip rivets are very versatile and cost-effective.
Advantages and disadvantages of fasteners
Below are the benefits of fasteners in their various applications:
- Weight reduction in the component is typically achieved.
- Ability to join high-strength steel up to a tensile strength of Rm = 1500 MPa.
- Minimum space requirements are needed within the tool.
- Tool maintenance is easy and simple.
- Capable of joining a wide range of sheet metal thickness with only one nut type t = 0.5 to 5mm.
- All surface-coated sheet metal panels are feasible.
- Easy and simple installation in every work direction.
Despite the good advantages of fasteners, some limitations still occur. Below are the disadvantages of fasteners in their various applications:
- Extra weight is added to the components.
- Bond lines are obvious.
- They require holes that weaken the components.
- They carry all load at specific points, which contribute to fatigue.
- Difficulty of refastening
- Corrosion, and
- Force precision.
Normally, fasteners can be permanent or non-permanent but are often used to create non-permanent joints. They are devices that mechanically join two or more objects together. That is all for this post where we discussed the definition, applications, functions, materials, and types of mechanical fasteners. You also learned the advantages and disadvantages of these fasteners.
I hope you get a lot from this post, if so, kindly share with other students. Thanks for reading, see you next time!