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Ultimate Guide to Steel Bolts Grades

It is necessary for anybody dealing with steel bolts to have a solid understanding of the grades and what each one signifies. Finding the appropriate quality of bolts for your project may make a significant difference in how well it will hold up over time, and this applies to anything from fasteners to newly constructed buildings.

You’re in luck since this comprehensive reference covers all you need to know about the various grades of bolts made of steel.

After reading through these fundamentals, you will undoubtedly be an expert in selecting the appropriate grade of steel bolt for any application. Get ready to learn about anything from bolts designed for general-purpose applications to grades designed specifically for industrial usage.

hex bolts

Introduction of Steel Bolt

Steel bolts are a very versatile and strong type of fastener commonly used in construction, manufacturing, and other industries to connect two objects together. Steel bolts are made from a combination of high-quality alloys, giving them their strength and making them resistant to corrosion over time. An added benefit is that they require no lubrication when installed, making them a great choice for use in tight places where oil or grease may be impossible to reach. 

Steel bolts are not only the preferred choice for many applications due to their superior performance, but they also come in an abundance of sizes, including ones with special head designs that can accommodate more complex projects. 


Anyone who needs quality and dependability should look into purchasing steel bolt goods rather than any of the other hardware options that are available on the market today. Steel bolt products provide outstanding value for money buy.

Steel Bolts – ASTM Grades

Steel bolts that are produced to ASTM standards are built using materials of the greatest quality, guaranteeing that they are both long-lasting and dependable. These bolts are normally fabricated from stainless steel, which is a material that exhibits an exceptionally high level of resistance to corrosion. As a result, they are an excellent choice for a wide variety of applications.

They are available in many different dimensions and ratings, such as A193 Grade B5, A193 Grade B7, and A307 Grade A, amongst others. In order for a bolt to be regarded as suitable for its intended use, it must satisfy the particular standards for tensile strength, yield strength, ductility, and any number of other attributes that are specified for that grade.

ASTM Designation Material
A307 Low carbon steel
A325 type 1 Medium carbon steel, Q & T
A325 type 2 Low carbon martensite steel, Q & T
A325 type 3 Weathering steel, Q & T
A354 grade BC Alloy steel, Q & T
A354 grade BD Alloy steel, Q & T
A449 Medium carbon steel, Q & T
A490 type 1 Alloy steel, Q & T
A490 type 3 Weathering steel, Q & T

The American Society for Testing and Materials (ASTM) regulates standards for steel bolts to ensure that products meet certain quality standards. This includes testing their hardness and measuring the strength of their threads using a torque test.

It also requires bolt manufacturers to inspect each piece individually before it is shipped out to customers. This ensures that all ASTM-grade bolts are strong enough to withstand heavy loads without failure or deformation under normal conditions.

Steel bolts adhering to ASTM standards offer excellent durability because of their resistance to corrosion, high tensile strength, and ductility. This makes them ideal for many industrial applications including plumbing fixtures, support structures, machine parts, and more. Additionally, they can be used in outdoor environments where exposure to moisture or high heat would cause other types of fasteners to corrode or become brittle. The fact that these bolts meet 

ASTM standards mean they can be used with confidence knowing that they will hold up under even the toughest conditions.

Steel Bolts – SAE Grades

Steel bolts are a sort of fastener known as a nut and bolt, and they are used in a wide variety of businesses and activities. In accordance with the criteria established by the Society of Automotive Engineers (SAE), they are manufactured in a variety of grades, with each grade indicating the level of the bolt’s strength and endurance.

SAE Grade Material
1 Low – medium carbon steel
2 Low – medium carbon steel
5 Medium carbon steel, Q & T
5.2 Low carbon martensite steel, Q & T
7 Medium carbon alloy steel, Q & T
8 Medium carbon alloy steel, Q & T
8.2 Low carbon martensite steel, Q & T

Grade 2 bolts are considered general-purpose fasteners, usually made from low or medium-carbon steel, and are heat treated to increase their strength. 

Grade 5 bolts offer more strength and durability than Grade 2 bolts. They are made from medium-carbon alloy steel and they undergo a special quenching process during manufacture which increases their hardness and tensile strength. 

Grade 8 bolts are the strongest of all SAE-graded steel bolts, manufactured from high-carbon alloy steel which has been hardened through a combination of heat treating processes to achieve superior tensile strength levels. 

These bolts typically have a black oxide finish to protect against corrosion, as well as yellow markings on the head which denote their grade. 

Steel bolts can be used for a wide range of applications including automotive repair and maintenance, construction work, home improvement projects, machinery assembly, and more. 

They provide reliable joint integrity for many different types of materials such as wood, metal, plastic and composite materials. With its versatility and dependable performance, it is no surprise that steel bolts remain one of the most popular fastening solutions available today.

FAQs About Steel Bolt

Do you need a steel bolt to complete your project? We are able to give you any sort of bolts that you want, from carriage bolts to hex bolts and everything in between. You can rely on us to provide all of the bolts that you require.

In addition, these steel bolts are created to the highest quality standards, which means that you can be assured that they will successfully finish the work that is now being performed. The following are some of the questions about steel bolts that are asked the most often.

Why is steel used for bolts?

It has a high tensile strength and can sustain loading again and over again without breaking. It finds widespread use in sizes between 0.005 to 0.125 inches. 

Steels that have been desulfurized and/or phosphorized (AISI 1117 and 1215). These steels have a machinability that is superior to that of basic carbon steels and are often utilized for the production of components for screw machines.

What is the strongest steel for bolts?

The highest possible grade of SAE bolt is grade 8, which is also its name. The minimum tensile strength of grade 8 bolts is 150,000 pounds per square inch (PSI).

What are the grades of steel bolts?

There are a few different classes of bolts, but the most frequent ones for SAE are grades 2, 5, and 8. 5.8, 8.8, 10.9, and 12.9 are the usual classes (grades) for metric. There is a distinct bolt strength associated with each grade. 

Regardless of the method that is used to provide a grade to the bolts, a higher number indicates a stronger bolt.

What bolts will not rust?

Screws made of stainless steel are by far the superior alternative when it comes to preventing rust from forming on the fasteners. Screws made of stainless steel have unique qualities that make them better able to resist the damaging effects of the weather when used outside. 

Many different types of outdoor projects make use of stainless steel fasteners because of their resistance to rust and corrosion.

What is the hardest grade of bolt?

Grade 8 is the most difficult, Grade 5 is considered to be in the middle, and Grade 2 is considered to be the easiest. This type of steel fastener is the most frequent and it also happens to be the least costly. 

There is no marking on the head of grade 2 bolts, however, the manufacturer’s mark may sometimes be present. The bolts of this grade are constructed out of low or medium-carbon steel.


The grade designation on a steel bolt is incredibly essential to consider when choosing a bolt since it indicates the bolt’s strength. The ASTM-SAE classification and the metric system are the two that are used the most often in order to determine the grades of steel bolts.

In addition, bolts made of steel may be categorized according to the material groups they belong to. The three primary kinds of steel used to make bolts are carbon steel, alloy steel, and stainless steel. In order to prevent any failures or catastrophes, it is essential that you choose the appropriate sort of steel bolt for the application you will be using in.

Do you have expertise working with a variety of steel bolts in diverse applications? Leave a comment below telling us what you think are the most important factors to consider when selecting a steel bolt for a particular project.


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