Nuts

A metal nut is a type of fastener with a threaded hole. It's typically used with a bolt to fasten materials together.

The purpose of a steel nut is to provide a mating thread for a bolt, allowing them to be tightened together and hold objects in place. The bolt passes through a hole in one object, and then the nut is threaded onto the end of the bolt from the other side. By turning the nut in the direction of the bolt's threads, the two pieces are drawn closer together, creating a tight and secure connection. When a nut is tightened onto a bolt, it applies compressive force, clamping the components together and preventing them from coming apart unintentionally.

Nuts come in various shapes and sizes, but they all serve the same purpose of providing a secure connection. The most common type is hex nut. Its hexagonal shape allows for easy application of torque using tools such as wrenches or socket wrenches during fastening. They are made of metals like steel, stainless steel, brass, aluminum, titanium, and others, each offering specific properties suited for different applications.

Here are some common types of metal nut:

• Hex Nut:  Hex nuts have a hexagonal shape and are among the most common types of nuts. 
• Lock Nut: They often have features such as nylon inserts, serrations, or prevailing torque designs to resist loosening under vibration or torque.
• Square Nut:  Square nuts have a square shape instead of a hexagonal shape. 
• Flange Nut:  Flange nuts have a built-in washer-like flange that distributes the load and helps prevent damage to the surface being fastened. 
• Cap Nut:  Cap nuts, also known as hex acorn nuts, have a domed top that covers the end of the bolt.
• Wing Nut:  Wing nuts have two large metal "wings" that allow them to be tightened or loosened by hand without the need for tools.
• Cage Nut:  Cage nuts have a spring steel cage that allows them to be easily inserted into square holes in metal panels. 
• Weld Nut: Weld nut is a specialized type of nut designed to be welded onto another object using spot welding.

1) Most commonly used materials for nuts: 

• Carbon steel - The most common material for screws and bolts, relatively inexpensive and suitable.
• Stainless steel - 304 & 316 are renowned for their corrosion resistance, making them ideal for environments exposed to moisture or corrosive elements.
• Alloy steel - Made from steel combined with other elements to enhance its mechanical properties, including strength and hardness. 
• Titanium - Lightweight and highly corrosion-resistant, where both strength and corrosion resistance are critical.
• Brass - Corrosion-resistant, great electrical conductivity, commonly used in electrical and decorative applications.
• Aluminum - Lightweight & corrosion-resistant. 

2) Common finish types:

• Zinc - provides moderate corrosion resistance.
• Copper - good corrosion resistance, and excellent conductor of electricity.
• Nickel - often used for decorative purposes due to shiny appearance.
• Zinc nickel - excellent corrosion resistance, and longer service life than common zinc finish.
• Black oxide - a chemical finish that provides corrosion resistance and a black appearance. 
• Zinc Phosphate - act as a barrier against corrosion by providing a protective layer between the metal substrate and corrosive elements.
• Coatings per automotive standards (RoHs compliance)