Automotive Bolts and Screws: Know Their Categories and Manufacturing

Bolts and screws are mechanical fasteners for joining two or more objects, making them a critical part of the product assembly process in many industries. In the automotive industry, bolts, and screws, often called automotive bolts and screws, are critical parts of the automotive design process as they aid in joining several automotive parts.

The applications of automotive bolts and screws in automotive assembly depend on the types, material makeup, and the parts to be joined together. Therefore, this article will explain their classifications, innovations, and considerations and how to eliminate the risks of loosening automotive fasteners.

boltsWhat is a Bolt?

A bolt is a mechanical fastener used with a nut or a washer and applicable in joining two or more components. It has a cylindrical body with a specified diameter and threading profile (a thread part shaft and an unthreaded shank) and a non-tapered end. The bolt can be divided into several sections, which are:

  • Head: The bolt’s head is the top part where torque is applied to loosen or tighten it. It comes in various shapes and sizes, such as hexagons (hex heads), square, round, etc., and is partly responsible for the different types of automotive bolts currently in the market.
  • Shank: This is the elongated and cylindrical part of the bolt that does not have threading. It is the underside of the head to the point where the threading begins and is responsible for gripping the two parts together.
  • Threaded End: This bolt part has a helical or spiral threading that matches the nut. The interlocking between the threading of the bolts and nuts forms a secure connection that joins the two together.
  • Tapered End: The tapered end ensures proper insertion of the bolt into the threaded hole.

screwsWhat is a Screw?

A screw is another mechanical fastener with a cylindrical body but a full threading profile that mechanically secures two parts by interlocking with a threaded hole. It does not need a nut and can be self-tapped (installed without a need for an already made tapered hole) or not. It can be divided into several sections, which are:

  • Head: The screw head is the top part of the whole fastener. It has a unique design that determines the type of tools for loosening or tightening it.
  • Shank: This is the cylindrical and threaded portion of the screw that extends from the lower part of the head to the tip.
  • Thread: The threading is helical or spiral runs along the shank’s exterior, and is responsible for gripping the two parts together.
  • Tip: The screw tip facilitates the entry of the screw into the parts being fastened.

Classifications of Automotive Bolts and Screws

Automotive bolts and screws come in different types and are classified based on their functions, designs, and material makeup. Below is an extensive explanation of the different types, their design, and applications.

different car bolts and screws1. Based on Functions

Automotive bolts and screws are classified based on their application in the automotive industry. The three common applications of both automotive fasteners include;

1.1 Structural Automotive Bolts and Screws

Bolts and screws in this category are applicable in joining automotive parts with structural functions. They have high tensile strength and durability. Hence, they are suitable for components with load-bearing capabilities, such as suspension systems, chassis, and frame elements.

1.2 Fastening Automotive Bolts and Screws

This category is the opposite of the previous, hence, their name (general purpose bolts and screws). They have lesser strength and durability and are suitable for joining non-structural components such as panels and trim pieces with lower strength requirements.

1.3 Specialty Automotive Bolts and Screws

Bolts and screws under this category are applicable in special fastening operations. As a result, they have unique designs and features such as coatings, material makeup, and threading profile, which allows them to function in special settings. Examples include bolts and screws designed for anti-corrosion parts (e.g., car underbody), high temperature (e.g., exhaust systems), and components that experience vibration (e.g., engine mounts).

2. Based on Design

Car bolts and screws can also be classified based on their designs. This is the most common way to classify automotive screws and bolts. The common examples of bolts and screws in this section include:

hex head2.1 Hex Head Automotive Bolts and Screws

Hex-head automotive bolts and screws are the most common automotive fasteners. They have a six-sided head or hexagonal (hex) head, with the bolts having a shank while the screws have a full threading profile. Both types allow a very secure engagement, although the bolt is more secure as it uses a nut while the screw doesn’t.

flange bolts and screws2.2 Flange Automotive Bolts and Screws

Flange automotive screws and bolts have a head likened to a washer. The shank extends slightly in the bolt head before joining the threaded end, providing a strong and secure connection. However, in the screw, the whole shaft has full threading. The flange makes these bolts and screws more suitable for load-bearing surfaces as it distributes forces effectively while reducing the deformation of the joint.

flat head screw2.3 Flat Head Automotive Screws

Flat-head automotive screws have a flat top surface with a countersunk, allowing the screw to align with the parts being joined after full tightening. As a result, it has a smooth and unobtrusive finish after installation.

They are the perfect type of automotive screws when there is a need to maintain a streamlined appearance. As a result, they are applicable in joining interior panels, dashboard components, trim pieces, and other automotive components that need a sleek and professional finish without reducing the parts’ structural integrity.

pan head screw2.4 Pan Head Automotive Screws

Pan-head automotive screws have a slightly raised head. The round head reduces sharp edges, snagging, and interference with other parts while improving the ease and versatility of installation. Furthermore, their larger head size increases their load-bearing capabilities due to their larger head size. As a result of their profile, they are applicable in securing parts with larger contact areas.

socket head screw2.5 Socket Head Automotive Screws

Socket head automotive screws have a cylindrical head with an internal hexagonal socket and a thread that allows a secure connection with a hex key or socket tool. The design makes the automotive screw suitable for parts located in tight spaces, and the internal hex socket ensures a better, precise, and secure fit during installation. They are applicable in parts requiring precise tightening due to the ease of installation, exceptional torque transfer and control, and head compactness, reducing protrusion. These include tight engine compartments.

u bolt2.6 U bolts

These automotive bolts have a U shape with threaded arms that allow for secure fastening. It applies to clamping cylindrical automotive parts such as exhaust pipes to flat surfaces. They are versatile car bolts that prevent rolling or shifting of the automotive parts, and their design aids easy installation and adjustment.

carriage bolt2.7 Carriage Automotive Bolts

Carriage automotive bolts have a round head which gives them visual appeal, and a square neck which allows them to fit into a square hole and prevent rotation during installation. They are suitable for aesthetics and functionality components such as exterior components, trim, and decorative elements.

3. Based on Material

Automotive bolts and screws are made using several materials which give distinct properties and are responsible for the fastener’s durability, performance, and suitability. Common materials for making these bolts and screws:

bolts and screws for steel3.1 Steel Bolts and Screws

Car screws and bolts made from steel are strong and cost-effective. You can use different steel grades for screws and bolts; the higher the grades, the higher the tensile strength. Aside from strength, steel automotive bolts and screws are versatile and suitable for structural components such as engines and chassis.

stainless steel bolts and screws3.2 Stainless Steel Bolts and Screws

Car screws and bolts made using stainless steel have better corrosion resistance. As a result, they are suitable for parts that will be subjected to moisture or harsh environments. They are durable and visually appealing, which makes them a popular option for automotive exterior trim and interior components.

bolts and screws for titanium3.3 Titanium Bolts and Screws

Car bolts and screws made using titanium have exceptional strength-to-weight ratio and corrosion resistance. Furthermore, they are lightweight and are suitable where there is a need to reduce the weight of cars. As a result, they are widely applicable in exhaust, suspension, and other lightweight automotive parts.

aluminum screws3.4 Aluminum Bolts and Screws

Aluminum is another material for making car screws and bolts and is popular for its lightweight properties and corrosion resistance. They have lower tensile strength compared to steel. As a result, they are often chosen for non-structural purposes. Common examples include interior panels and decorative elements.

plastics bolts and screws3.5 Plastics Bolts and Screws

You can also use vinyl and other plastics with immense tensile strength and other properties to make Car bolts and screws. However, they are commonly suitable for aesthetic functions. Furthermore, they are suitable for one-time use, have insulative properties, and are cheaper than metal bolts and screws.

Automotive Bolts and Screws Manufacturing: Challenges and Considerations

Automotive fastener manufacturing ensures that vehicles have structural integrity, are safe, and of required performance. However, this also has its challenges. Below are the different challenges and considerations in automotive bolts and screw manufacturing.

bolts and screws manufacturing for automotiveCorrosion Resistance

Vehicles come in contact with moisture and high humidity that make corrosion of parts and fasteners a huge possibility. As a result, corrosion resistance is a huge challenge. A working solution is using strong corrosion-resistant materials such as stainless steel and titanium, coatings, and plating to ensure the fasteners’ longevity and reliability.

Proper Fastening Techniques

Another challenge with bolt and screw manufacturing is adherence to stringent fastening standards for proper installation. Deviation from these standards can lead to loosening, reduced joint integrity, and safety. There is a need to employ suitable torque tools and procedures that align with standards to maintain the structural integrity of vehicles.

Compatibility with Different Materials

Automotive parts come from several materials such as metals, plastics, and composites. As a result, the challenge is that the bolts and screws should be compatible with these materials.

There is a huge need to make automotive screws and bolts using the right material, with the right design and coatings, and must account for the automotive part’s stiffness, thermal expansion, stiffness, and other properties. This will ensure a consistent clamping force and reduce material damage or fatigue.

How to Eliminate Risks to Loosen Automotive Fasteners?

A loose automotive fastener can lead to safety issues. As a result, there is a need for effective strategies to prevent the fastener from loosening:

automotive fastenersChoose Screw Locking Insert

The insert will grip the bolts and nuts, preventing them from loosening due to vibrations. They are repeatable. Furthermore, they allow for easy assembly and disassembly without loosening the fastener.

Use a Washer

A washer can help improve the bolts and nuts grips for automotive bolts, thereby preventing them from loosening due to vibrations.

Test the Torque

The torque is the rotational force you apply to tighten the automotive fastener. As a result, you should test the torque using a machine such as the Skidmore-Wilhelm Bolt Tension Calibrator. You can determine how the surface area and roughness affect friction using bearing surface testing. Finally, the coefficient of friction test will measure the kinetic and static resistance of a surface dragged across another.

Innovations in Automotive Bolts and Screws

The automotive industry is highly evolving, hence, there have been several innovations in automotive fasteners. Common innovations include:

Use of Lightweight Materials

Lightweight materials such as titanium, aluminum, and advanced alloys are now applicable in car bolts and screws. As a result, automotive manufacturers have been able to improve fuel efficiency and reduce carbon emissions. Aside from the lightweight, they are also strong.

Self-Locking Mechanisms

The self-locking mechanism allows modern fasteners to use an integrated locking mechanism. As a result, additional components such as washers or nuts are eliminated. Furthermore, there is a reduction in vibrations which prevents the fasteners from loosening.

Anti-Corrosion Coatings

Now coatings like zinc-nickel, ceramic, and polymer coatings give the fasteners corrosion resistance. As a result, these increase the longevity of the fasteners in challenging environments

Smart Bolts with Embedded Sensors

Smart bolts now have embedded sensors that allow tracking factors such as torque, stress, tension, and temperature. Consequently, it is possible to know the health of fastened joints and predict maintenance and safety.

Need Automotive Bolts and Screws for Test Products?

Choosing the right bolts and screws can be challenging without the right information. As a result, automotive part manufacturers need a knowledgeable and reliable automotive fastener manufacturer. At WayKen, we can help you choose different types of automotive fasteners using different materials for prototyping or end-use products based on your requirements.

Our engineering team is highly experienced in automotive prototypes and components using custom manufacturing processes such as CNC machining, sheet metal fabrication, and 3D printing. Furthermore, we can provide free DfM and work with high quality and precision. Upload your CAD files today.


Bolts and screws are automotive fasteners that are crucial components in joining many types of automotive parts. They come in several types and designs and come from several materials such as titanium, aluminum, steel, and even plastics. This article discussed the types of automotive bolts and screws, their functions, innovation, challenges and considerations, and the innovations.


What is the difference between bolts and screws?

The difference between a bolt and a screw is that screw has a full threading, while a bolt does not. Furthermore, a bolt also has tapering and requires a washer or nut, while a screw does not need a washer or nut.

What is the most common automotive bolt?

The most common automotive bolt is the hex head automotive bolt used in the automotive industry.

What is the female part of a bolt called?

The female part of the bolt is the nut. It has internal threads that match the bolt. Washers are not the female part but are suitable for preventing loosening and crushing.

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