The Ultimate Guide To Customized Hexagon Head Cap Screws

Hexagon head cap screws are threaded fasteners with a six-sided head. They are commonly referred to as hex bolts or hex cap screws and are often used in applications where precise tolerances are required, such as construction projects and infrastructure. These screws are typically installed with a wrench or a socket and offer a larger surface-bearing area for better clamping compared to other fasteners. Hexagon head cap screws come in a variety of materials, dimensions, and grades, and can be customized to meet specific requirements.

Hex cap screw head markings

The markings on the head of a hex cap screw will vary depending on whether it is a SAE or Metric screw. SAE screws will have radial markings, with higher numbers of markings indicating a higher grade. For example, a grade 5 screw will have three radial lines, while a grade 8 screw will have six. Metric screws will have markings such as 8.8, 10.9, 12.9, and 18.8, which refer to the tensile strength of the screw.

SAE hex cap screws are available in grades 2, 5, and 8, as well as L9. Grade 2 screws are made from low to medium carbon steel and are suitable for non-critical applications. Grade 5 screws are made from medium carbon steel and are commonly used in automotive applications. Grade 8 screws are also made from medium carbon steel and are used in high-stress applications. Grade L9 screws are made from high-quality alloy steel and are perfect for high-stress environments.

Metric hex cap screws are available in grades 8.8, 10.9, 12.9, and 18.8. Grade 8.8 screws are made from heat-treated, medium-quality carbon steel and are commonly used in motors, engines, and industrial equipment. Grade 10.9 screws can be made from medium-quality carbon steel, carbon steel alloy, or low-quality boron steel. They are often used in automotive applications. Grade 12.9 screws are the highest class of metric cap screws and are used in high-stress environments.

Hex cap screw classifications

The first classification of hex cap screws is based on their head style. The most common head styles for hex cap screws are the hex head and the socket head. The hex head screws have a hexagonal-shaped head that is designed to be driven by a wrench or a socket. The socket head screws have a cylindrical head with a hexagonal recess that is driven by a hex key or a socket driver.

The second classification is based on the thread type. There are two common thread types for hex cap screws: coarse and fine. Coarse threads are used for most general-purpose applications, as they are faster to thread and have a higher load capacity. Fine threads, on the other hand, offer a finer adjustment and are used in precision applications or when a tighter seal is required.

The third classification is based on the material used. Hex cap screws are typically made from a variety of materials, including steel, stainless steel, brass, and nylon. Each material has its unique properties and is suitable for different applications. For instance, steel screws are ideal for applications that require high strength and durability, while stainless steel screws provide superior corrosion resistance, making them a common choice for outdoor use or in high-moisture environments.

The fourth classification is based on the screw dimensions, including length and diameter. Hex cap screws are available in a wide range of sizes to accommodate different fastening needs. The length is typically measured from the underside of the head to the tip of the screw, while the diameter refers to the thickness of the screw shaft. Selecting the appropriate length and diameter is crucial to ensure secure fastening and adequate load-bearing capacity.

Lastly, hex cap screws can be classified based on their finish or coating. These screws may be coated to enhance their appearance, improve corrosion resistance, or provide other specific properties. Common finishes in the market include zinc plating, black oxide, and cadmium plating, each offering unique advantages depending on the specific requirements of the application.

Hex cap screw grades

SAE Hex Cap Screw Grades

SAE hex cap screw grades include Grade 2, Grade 5, and Grade 8. Grade 2 hex cap screws are made from low or medium carbon steel and are an economical choice for use in non-critical applications where the screw is not subject to extreme temperatures or stress. Grade 5 hex cap screws are made from medium carbon steel and are heat-treated. They are commonly used in automotive applications and have greater tensile strength than Grade 2 screws. Grade 8 hex cap screws are also made from medium carbon steel and are heat-treated. They have greater tensile strength than Grade 5 screws and are designed for use in high-stress applications.

Metric Hex Cap Screw Grades

Metric hex cap screw grades include 8.8, 10.9, and 12.9. Grade 8.8 fasteners are made from heat-treated, medium-quality carbon steel and are commonly used in motors, engines, and industrial equipment. Grade 10.9 fasteners are similar to Grade 8 but can also be made from a carbon steel alloy or low-quality boron steel. They have high tensile strength and are often used in automotive applications. Grade 12.9 fasteners are the highest class of metric cap screws and are used in high-stress environments. They have a higher tensile strength than Grade 8 fasteners, making them more durable.

ASTM Hex Cap Screw Grades

ASTM refers to the grade standards set by the American Society for Testing and Materials. A2/Type 304 (18-8) stainless hex cap grade fasteners are the most common type on the market. They are perfect for high-temperature applications and resistant to corrosive acids. A4/Type 316 stainless hex cap grade fasteners are also known as marine-grade fasteners as they can withstand saltwater. These screws are often used in docks, piers, boats, and boathouses.

Hex cap screw dimensions and specifications

Hex cap screws are commonly used in applications where precise tolerances are required, such as construction and machine assembly. They are often mistakenly called hex bolts, but the main difference is that hex cap screws feature a washer face under the head and a chamfered point, while hex bolts do not.

The dimensions and specifications of hex cap screws can vary depending on the specific application and requirements. Here are some important factors to consider when selecting or customising a hex cap screw:

Basic Product Diameter

This refers to the nominal size or basic bolt diameter of the hex cap screw. It is an important factor in ensuring the compatibility of the screw with the threaded hole or mating component. The diameter can range from standard sizes such as 1/4 inch to larger sizes like 1-1/2 inches.

Width Across Flats (F) and Width Across Corners (G)

These dimensions refer to the distance measured across the hex head of the screw. The width across flats (F) is the distance between two parallel sides of the hexagon, while the width across corners (G) is the distance between two opposite corners. These measurements are important for tool selection and ensuring adequate clearance during installation.

Length

The length of a hex cap screw is measured from the underhead bearing surface to the extreme end of the screw. Hex cap screws can come in various lengths, typically ranging from under 1 inch to over 6 inches. It is important to select the appropriate length for your specific application to ensure proper fastening and avoid interference with other components.

Thread Type

Hex cap screws can be either fully threaded or partially threaded. Fully threaded screws are suitable for projects that require significant gripping strength, while partially threaded screws offer more holding power when force is applied from the side. The appropriate thread type depends on the specific application and the type of force the screw will be subjected to.

Grade and Material

Hex cap screws are classified by grade, which indicates their intended application and performance characteristics. Common grades include Grade-2, Grade-5, and Grade-8, with each grade offering varying levels of tensile strength and suitability for different stress applications. The material used can vary, including low carbon steel, medium carbon steel, stainless steel, and alloys.

Performance and Mechanical Specifications

The performance and mechanical specifications of hex cap screws include tensile strength, yield strength, elongation, and reduction of area. These specifications are important for understanding the load-bearing capacity and behaviour of the screws under different conditions. For example, Grade-5 screws have higher tensile strength than Grade-2, while Grade-8 screws are designed for high-stress applications.

Finish

Hex cap screws can be finished in various ways to enhance their appearance or protect against corrosion. Common finishes include plain, hot-dipped galvanised, and zinc finishes. The choice of finish depends on the intended application and the level of corrosion resistance required.

Hex cap screw vs hex bolts

Hex cap screws and hex bolts are often confused with one another, but they are two distinct types of fasteners. The most basic difference between the two is the way they are installed. A hex bolt is installed by turning a nut to tighten the fastener, while a hex cap screw is installed by turning the head of the bolt to assemble and tighten.

Hex cap screws are typically used in precise applications, such as in an OEM setting, where tight tolerances are required. They have a flat washer facing under the head that meets specific tolerances as described under ASME B18.2.1-1996. They also have tighter tolerances on the body dimensions and a chamfered end. Hex cap screws are commonly used without a nut and are tightened directly into a tapped or threaded hole.

On the other hand, hex bolts are often used when the mechanical properties are more important than dimensional tolerances, such as in the construction industry. Hex bolts are flat underneath the head and have a flat end. They are typically manufactured by a hot-forging process.

When it comes to customization, both hex cap screws and hex bolts can be made from different materials and come in various grades, depending on the specific requirements of the project. For example, hex cap screws are available in grades 2, 5, and 8, with each grade offering different tensile strength and suitability for different temperatures and stress levels. Similarly, hex bolts also have different grades and property classes that determine their mechanical properties.

In summary, while hex cap screws and hex bolts may look similar, they have distinct differences in their installation methods, applications, and dimensional characteristics. It is important to carefully consider the specific requirements of a project before choosing between these two types of fasteners.

Frequently asked questions