What Are Bolts And Nuts?

The bolted connection is an appealing method due to its ease of use. It combines a screw/stud with a threaded counterpart such as a nut or tapped hole and only requires a simple torque wrench to operate. This differentiates it from other technologies such as:
• Bonding: Relies on the operator's judgement to determine quality and correct application.
• Riveting: This assembly requires press tools that makes the process more complex.
• Welding: Requires a certified welder, advanced tooling and failure can remain undetected.

A bolted joint is not a permanent assembly, it can be easily removed and reused using the same tools with which it was assembled. This is very helpful for maintenance, simple checks or replacement of parts. It is also useful when the product is at the end of its life cycle as parts made of different materials can be separated, sorted and recycled effectively.

Bolts are available in a range of sizes and materials depending on the demand of the application. They are commonly made of steel, which provides strong mechanical characteristics that are usually greater than the capacities of the assembled parts.

Bolts can be used to join parts made of materials that are different than the bolt itself, such as plastics and composites. No special arrangement or design is required to make this assembly compatible.

The thickness of the assembled parts can be as large as they need to be to fit the manufacturer's needs. The thickness and the hole size can be produced with large tolerances. This usually implies economical and regular well-known machining processes.

Normalized steel bolts can sustain temperatures between -50°C and 200°C and for wider demands, stainless steel bolts can function between the ranges of -160°C and 500°C. Special designs using materials able to sustain high temperatures and alloys capable of functioning in an acidic environment can bring the connection to the right level of performance.

The shank diameter is the diameter of the smooth or unthreaded portion of the bolt shaft. It is often referred to as the nominal diameter or body diameter.

The major diameter is the largest diameter of the bolt thread. It is the distance between two opposite crests or the topmost surface of the thread. The major diameter is often equal to the nominal diameter.

The minor diameter (or root diameter) is the smallest distance of the bolt thread. It is the distance between two opposite roots or the bottommost surface of the thread.

The pitch diameter is the diameter halfway between the major and minor diameters.

Anchor Bolts
Anchor bolts are designed to join components into concrete surfaces. They are commonly used in the construction industry. They are usually found in the bases of steel poles. They are also used in attaching façade systems to reinforced concrete walls. There are two classifications of anchor bolts:
• Cast-in-place anchor bolts are installed by drilling a hole in the concrete slightly larger than the bolt, fixing the bolt in place, and pouring a concrete mixture into the remaining spaces in the hole. Once the concrete settles, the bolt will not dislodge easily.
• Drilled-in-place anchor bolts are installed without the use of wet concrete. They are installed directly into an ample-sized hole drilled into hardened concrete. Adhesives are applied on the bolt installation to stabilize the connection.

Arbor Bolts
Arbor bolts are pre-assembled bolts with a washer permanently attached to the head of the bolt. Their head has a sinker design with ridges around it. Arbor bolts have a dark or black finish and reverse threads that differentiate them from other bolts. The reverse thread is the most important feature of arbor bolts and is critical to their use. Unlike other types of bolts, arbor bolts are not commonly sold in home improvement stores or hardware stores. They have a single function and are not considered to be fasteners. Arbor bolts are used with electric saws to keep the blade of the saw secure and working properly and are a critical part of a saws operation.

Blind Bolts
Blind bolts are a specialty bolt that was developed for applications where hex bolts and rivets can't be used due to restricted access. They have good tensile strength and can handle loads that are slightly less than standard bolts. Blind bolts are used to join objects using a pre-drilled hole in one of the objects to be joined and where there is limited space due to adjacent components.The head of a blind bolt has a series of teeth that interlock with a nut, which provides extra strength and stability when secured. Blind bolts get their name due to their ability to access only one side of objects to be joined and the inability to see the other side. They have a pin, collar, and sleeve. The collar is designed to collapse as the blind bolt is tightened.

Carriage Bolts
Carriage bolts are partially threaded along their shank and have a round head with a square neck that keeps the bolt from turning when being fastened. They are referred to as plow or coach bolts and are mainly used in wood applications. Carriage bolts have tensile and shear strength, which varies according to the type of material from which they are manufactured. Carriage bolts made of stainless steel have a shear strength of 90,000 psi.A carriage bolt is secured using a nut with a washer that is attached to the threads on the flat end of the bolt. When determining the size of a carriage bolt, it is important to measure them from under the head to the end of the bolt. Measuring from under the square neck leads to inaccurate measurements. A pilot hole of the diameter of the flat end of a carriage bolt has to be drilled prior to inserting the bolt. It is important to use a washer with a nut when securing a carriage bolt to reduce potential surface damage.

Elevator Bolts
Elevator bolts get their name from their use in the construction of elevators. Their flat head allows them to secure components without interfering with the movement of the elevator. The distinct feature of elevator bolts is their flat round thin head that becomes flush with the surface to which they are attached when secured.Threads on an elevator bolt go part way up the shaft. Underneath the flat head is a square neck that is similar to that of carriage bolt, which provides for a tight secure connection and prevents the bolt from turning during installation. Elevator bolts are made from several types of materials and come in different diameters, lengths, and sizes.A common use for elevator bolts is in the construction of conveyors, which require a flat surface for smooth operation. Additionally, since elevator bolts form a highly secure connection, they prevent conveyors from vibrating or shifting. They are also an ideal fastener for soft materials such as softwoods, fabrics, and plastics.