Machine bolts play a crucial role in various industries and everyday applications, providing secure fastening solutions for countless projects. With the convenience of online shopping, Amazon offers a wide selection of machine bolt sets from various brands. To help you make an informed decision, we have compiled a list of the five best machine bolt products available on Amazon, complete with a summary and a detailed list of pros and cons for each. 

To see our related product guide article, click here.

Top Picks for Best Machine Bolt

K Kwokker 1263PCS Metric Bolt Assortment

The K Kwokker 1263PCS Metric Bolt Assortment offers a comprehensive selection of bolts in various metric sizes (M2, M3, M4) and 21 different sizes. It includes hex socket head cap machine screws made from 12.9 alloy steel with a zinc plated finish.

Pros:

• Wide range of sizes for M2, M3, and M4 bolts.
• Durable and corrosion-resistant 12.9 alloy steel material.
• Handy storage case for easy organization and access.

Cons:

• Limited to only three metric sizes.

Senyard Zinc Plated Hex Socket Head Cap Machine Screws

This assortment kit includes 890 pieces of screws, nuts, and washers, providing a variety of M6, M5, M4, and M3 metric screws. The kit also comes with lock and flat washers and wrenches, making it a versatile choice for different projects.

Pros:

• Extensive assortment of screws with M6, M5, M4, and M3 metric sizes.
• Lock and flat washers, along with wrenches, add value and versatility.
• Zinc plated finish offers protection against rust and corrosion.

Cons:

• Some users may prefer a wider range of sizes, including larger dimensions.
• The case design might not be the most durable for heavy use.

Senyard Stainless Steel Hex Head Metric Screws Assortment Set

This kit offers a collection of 815 machine screws in various sizes (#6-32, #8-32, #10-24) with a Phillips pan head. The screws are made from durable 304 stainless steel, and the kit includes lock and flat washers, as well as wrenches.

Pros:

• High-quality 304 stainless steel ensures excellent corrosion resistance.
• Wide range of sizes, covering #6-32, #8-32, and #10-24.
• The inclusion of washers and wrenches adds practicality.

Cons:

• Limited to specific screw head type (Phillips pan head).

VIGRUE Stainless Steel Screw Bolt Nut Washers Assortment Kit with Case

This kit contains 470 pieces of #8-32 Phillips pan head screws, along with nuts, flat washers, and a screwdriver bit. The components are made from durable 304 stainless steel, ideal for various applications.

Pros:

• High-quality 304 stainless steel material for rust resistance.
• The inclusion of a screwdriver bit provides added convenience.
• Compact and durable storage case.

Cons:

• Limited to one specific size (#8-32) and screw head type.
• The number of screws may not be sufficient for large-scale projects.

VIGRUE M6-1.0 x 12/16/20/25/30mm Flange Button Head Screws Nuts Assortment Kit

The VIGRUE M6-1.0 kit consists of 170 pieces of M6-1.0 flange button head screws and matching nuts. These screws have a black oxide finish, providing both durability and a sleek appearance.

Pros:

• Flange button head design offers a unique aesthetic and added functionality.
• Black oxide finish enhances corrosion resistance.
• Kit includes a range of sizes for M6-1.0 screws.

Cons:

• Limited to M6-1.0 size screws, which may not cover all needs.
• Lack of washers and other accessories.

Conclusion

Choosing the right machine bolt set is essential for the success and longevity of your projects. Each of the top 5 machine bolt products on Amazon offers unique advantages, catering to various requirements. Consider your specific needs, such as materials, sizes, and applications, before making a purchase. Whether you need a comprehensive assortment, specialized security screws, or reliable T nuts, these top-rated machine bolts are sure to meet your fastening needs effectively.

What Should You Look for in a Machine Bolt?

When choosing a machine bolt, there are several important factors to consider to ensure it meets the requirements of your project or application. Here are some key aspects to look for in a machine bolt:

1. Size and Length: Machine bolts come in various sizes and lengths, typically indicated in metric or imperial measurements. Ensure that you select the right size and length that matches the specific requirements of your project. The length should be sufficient to securely fasten the joint without being too long or too short.
2. Material: Machine bolts are available in different materials, such as stainless steel, carbon steel, alloy steel, brass, and more. The material choice depends on the intended use and environmental factors. Stainless steel bolts are corrosion-resistant, making them suitable for outdoor and marine applications, while carbon steel bolts are cost-effective and commonly used in indoor projects.
3. Strength and Grade: The strength of a machine bolt is often denoted by its grade, such as Grade 2, Grade 5, or Grade 8 for carbon steel bolts. Higher-grade bolts offer greater tensile strength and are suitable for applications that require increased load-bearing capabilities. Consider the strength requirements of your project and select the appropriate grade accordingly.
4. Thread Type: Machine bolts can have different thread types, such as coarse threads or fine threads. Coarse threads are more common and offer quicker assembly and disassembly, while fine threads provide better holding power and are ideal for applications where vibration resistance is essential.
5. Head Type: Machine bolt heads come in various designs, including hex head, square head, and round head. Hex head bolts are the most common and can be tightened with a standard wrench, making them easy to use in many applications.
6. Coating or Finish: Some machine bolts may come with special coatings or finishes to enhance their durability and corrosion resistance. Common coatings include zinc plating, galvanizing, or black oxide coating. Choose the appropriate coating based on the environmental conditions the bolts will be exposed to.
7. Application Specific Requirements: Consider any specific requirements for your project, such as the need for weather-resistant or heat-resistant bolts, bolts with anti-loosening features (e.g., nylon insert lock nuts), or bolts designed for high-temperature or high-pressure environments.
8. Certification and Standards: If the application demands it, ensure that the machine bolts meet specific industry standards or certifications, such as ASTM, ISO, or DIN standards, to ensure the bolts’ quality and performance.
9. Cost: Finally, consider the budget for your project and balance the cost with the required quality and performance. Opting for cheaper low-quality bolts may lead to failures and additional costs in the long run.

By carefully considering these factors, you can select the most suitable machine bolts for your project, ensuring its success and longevity. Always consult with a hardware professional or supplier if you are uncertain about the best bolts for your specific application.

Frequently Asked Questions

What are the strongest rated bolts?

The strength of bolts is typically indicated by their grade, and the strongest rated bolts are those with higher-grade classifications. In the United States, the most common grading system for bolts is the SAE J429, which categorizes bolts into different grades based on their tensile strength. Here are some of the strongest rated bolts according to the SAE J429 grading system:

1. Grade 8: Grade 8 bolts are the highest strength bolts commonly available. They are made from medium carbon alloy steel and are quenched and tempered to achieve their high tensile strength. Grade 8 bolts have a minimum tensile strength of 150,000 psi (pounds per square inch) and a minimum yield strength of 130,000 psi.
2. Grade 9: Grade 9 bolts are even stronger than Grade 8 bolts. They are made from a higher carbon alloy steel and undergo the same quenching and tempering process. Grade 9 bolts have a minimum tensile strength of 180,000 psi and a minimum yield strength of 153,000 psi. However, Grade 9 bolts are less common and often used in specialized applications.
3. Grade 10.9: In metric grading systems, Grade 10.9 bolts are equivalent to Grade 8 bolts in the SAE J429 system. These bolts have a minimum tensile strength of 1,040 MPa (megapascals) and a minimum yield strength of 940 MPa. Grade 10.9 bolts are widely used in automotive and engineering applications.

It’s important to note that the strength of a bolt is not the only consideration when choosing the right fastener for a specific application. Factors such as the material of the bolt, the thread type, and the head type should also be taken into account. Additionally, for critical applications or in industries with specific requirements, it’s essential to adhere to the appropriate standards and certifications to ensure the bolts’ quality and performance. Consulting with a professional or knowledgeable supplier is recommended to select the most suitable and strongest bolts for a particular project.

What are the different grades of bolts?

Bolts are graded based on their material, strength, and intended use. The grading systems can vary depending on the country and the standard used. In the United States, the most common grading system for bolts is the SAE J429, which categorizes bolts into different grades based on their tensile strength. In the metric system, bolts are graded using the ISO metric grading system or the property class system. Here are the different grades of bolts in both systems:

SAE J429 Grading System (Imperial):

1. Grade 2: These bolts are made from low or medium carbon steel and have a minimum tensile strength of 74,000 psi. They are used for general-purpose applications with low or moderate stress.
2. Grade 5: Grade 5 bolts are made from medium carbon steel and are quenched and tempered to achieve a higher tensile strength. They have a minimum tensile strength of 120,000 psi and are commonly used in automotive and machinery applications.
3. Grade 8: Grade 8 bolts are made from medium carbon alloy steel and undergo quenching and tempering to achieve their high tensile strength. They have a minimum tensile strength of 150,000 psi and are used in high-stress applications where strength is crucial.
4. Grade 9: These bolts are made from a higher carbon alloy steel and have a minimum tensile strength of 180,000 psi. Grade 9 bolts are less common and used in specialized applications.

ISO Metric Grading System / Property Class (Metric):

1. Property Class 4.6: These bolts are made from low carbon steel and have a tensile strength of 400 MPa and a minimum yield strength of 240 MPa. They are used for general-purpose applications.
2. Property Class 5.8: Bolts of this class are made from low to medium carbon steel and have a tensile strength of 500 MPa and a minimum yield strength of 320 MPa.
3. Property Class 8.8: These bolts are made from medium carbon steel and are quenched and tempered. They have a tensile strength of 800 MPa and a minimum yield strength of 640 MPa, making them suitable for various applications.
4. Property Class 10.9: Bolts of this class are made from alloy steel and are quenched and tempered to achieve a tensile strength of 1,040 MPa and a minimum yield strength of 900 MPa. They are commonly used in automotive and engineering applications.
5. Property Class 12.9: The highest grade in the metric system, these bolts are made from alloy steel and have a tensile strength of 1,220 MPa and a minimum yield strength of 1,090 MPa. They are used in high-stress and critical applications.

When selecting bolts, it’s crucial to consider the specific requirements of your project and choose the appropriate grade to ensure the bolts can handle the intended load and stress levels.

Are machine bolts strong?

Yes, machine bolts are generally considered to be strong fasteners. Machine bolts are designed to provide strong and reliable fastening for a wide range of applications. They are commonly used in machinery, equipment, and structural components where a secure and robust connection is essential.

The strength of machine bolts depends on various factors, including the material, grade, and size of the bolt. Machine bolts are available in different materials, such as stainless steel, carbon steel, and alloy steel, each with its own level of strength and durability.

Higher-grade machine bolts, such as Grade 8 or Grade 10.9, are made from stronger materials and undergo specific heat treatment processes, resulting in bolts with increased tensile strength and yield strength. These high-grade machine bolts are commonly used in applications that require superior strength and load-bearing capabilities.

It’s important to note that the strength of a bolt also depends on the proper installation, including the torque applied during tightening. Properly torquing the bolt ensures that it reaches its intended clamping force, making the connection secure and strong.

When selecting machine bolts for a specific application, it is essential to consider the requirements of the project, including the expected load, environmental conditions, and any industry standards or certifications that may apply. Consulting with a hardware professional or engineer can help ensure that you choose the right machine bolts that offer the necessary strength and performance for your particular project.