Better understanding of fasteners

Industrial fasteners are an essential part of fastening systems used in mechanics, construction, and maintenance. Understanding bolt types, dimensions, threading, grade, material, and finish helps you choose the right product for the application.
Whether it’s for a mechanical assembly, a steel structure, or industrial equipment, selecting the proper bolts, nuts, and screws ensures safety, durability, and performance.

Unit of Measurement
Measurement is an important concept to understand when it comes to fasteners. Bolts are measured in inches or millimeters (imperial or metric system), and their dimensions are expressed based on diameter, thread, and length. For example, a 1/2-13 x 3” bolt has a 1/2-inch diameter, a 13 TPI thread (threads per inch), and a 3-inch length.

The same applies to nuts; their size is expressed according to their diameter and thread. For example, a 1/2-13 nut has a 1/2-inch diameter and a 13 TPI thread, which ensures compatibility with the matching bolt

Heads and threads
Bolt heads can come in different shapes, such as hex, square, or round. Hex heads are the most used in industrial applications because their shape allows efficient use with a socket wrench or a standard wrench.

Threads can also be coarse or fine: UNC (Unified National Coarse) or UNF (Unified National Fine). UNC threads have a wider spacing between threads, which makes them well suited for applications that require strong mechanical resistance and good performance under vibration. UNF threads, on the other hand, are preferred for applications that require greater precision, a tighter fit, and higher assembly quality.

Alloy
Bolts can be manufactured from different alloys and materials, each offering different properties in terms of mechanical strength, durability, and corrosion resistance. One of the most used materials in industrial fasteners is carbon steel, which is generally used for standard applications.

Stainless steel is also widely used in industrial fastening due to its excellent corrosion resistance, making it ideal for humid environments or applications exposed to the elements. Other bolt materials include alloy steel, aluminum, and brass, each providing specific advantages depending on performance requirements, weight considerations, and longevity.

Bolt Alloy Chart:

Alloy	properties
Carbon steel	Medium resistance, used for standard applications
Stainless steel	High resistance to corrosion, widely used in the industrial sector
Aluminium	Lightweight and corrosion resistant, used in aerospace and construction applications
Brass	Corrosion resistant and easy to work with, used for decorative and electrical applications

Grade
Bolts are classified based on their mechanical strength and performance, according to their bolt grade. Bolt grades are usually expressed as numbers: the higher the number, the greater the tensile strength and load capacity.

Grade 2 bolts are among the most used for general industrial applications. They are suitable for light-duty uses and offer a tensile strength of approximately 74,000 PSI.

Grade 5 bolts are stronger, with a tensile strength of around 120,000 PSI, making them a good choice for mechanical applications that require better durability and resistance under load.

Grade 8 bolts are the strongest, with a tensile strength of approximately 150,000 PSI. Grades 5 and 8 are often used in industrial applications that require higher strength and performance.

Bolt Grade Chart:

Finish
A bolt’s finish is an important factor to consider for industrial applications that require strong corrosion resistance or an aesthetic appearance. Bolts can receive various coatings and surface treatments—such as zinc, chrome, or cadmium—depending on the required level of protection, durability, and mechanical performance.
These fastener finishes help improve corrosion protection and extend the service life of fastening systems.

Bolt Finish Chart :

In conclusion, industrial fasteners play a crucial role across many industries. Understanding key concepts—such as units of measurement, materials and alloys, bolt grades, and finishes or surface treatments—is essential to selecting the right bolts and nuts for each specific application.

As an importer and distributor of industrial fasteners, we offer a complete range of bolts to meet our customers’ needs, whether they are looking for performance, durability, or corrosion resistance. We take pride in our expertise, our commitment to quality, and customer satisfaction.

Access our full range of industrial products through our: AB Industriel Home Page !