Choosing the right fastener for a steel structure project isn't complicated—but getting it wrong means joint failure and rework. This guide covers bolt grades, coatings, installation methods, and standards so you can select fasteners that stay secure and meet code.

Introduction to Various Fasteners and Their Applications

1. Bolts

Bolts feature an externally threaded shank and typically a hexagonal head; they are the most common detachable fasteners used in machinery and steel structures, usually employed in combination with nuts and washers.

Types include standard hex-head, square-head, fitted (reamed-hole), anti-rotation, T-slot, and anchor bolts, as well as high-strength large hex-head bolts specifically designed for steel structures.

2. Nuts

These are mating fasteners with internal threads most commonly hexagonal in shape designed to be used with bolts or studs to secure components.

 3. Screws

Generally compact in size and featuring diverse head styles (such as flat, countersunk, or Phillips), these are typically driven directly into pre-threaded holes in the workpiece rather than paired with nuts; their primary functions are fastening and positioning.

4. Studs (Double-ended studs)

These feature external threads at both ends with a smooth, unthreaded shank in the middle; they are categorized into unequal-length and equal-length types. During installation, one end is screwed into a thick-walled base component, while the other protrudes to be secured with a nut. They are suitable for applications involving thick components, compact structures, or the need for frequent disassembly—situations where standard bolts are impractical—and also serve to provide positioning or limiting functions.

 5. Wood Screws

Designed specifically for joining wood, these screws come in various head styles—such as round head and countersunk head—and are secured by being driven directly into the wood.

6. Self-tapping screws

These screws do not require pre-tapped internal threads in the workpiece; they cut their own threads during installation. They are primarily used for joining materials such as thin sheet metal, plastics, copper, and aluminum. Self-tapping thread-locking variants are also available, offering superior vibration resistance.

7. Washers

Installed between the contact surfaces of bolts, screws, or nuts and the workpiece, washers come in various types:

8. Retaining Rings

Primarily installed on shafts or within bores to provide axial positioning, locking, and anti-loosening functions for components. Types include elastic retaining rings, wire retaining rings, locking rings, and shaft-end retaining rings; various styles accommodate different load-bearing and positioning requirements.

9. Pins

Primarily used for positioning, though they also serve to connect parts and prevent loosening; some pins can act as safety overload protection components.

10. Rivets

These fasteners feature an unthreaded shank with a pre-formed head at one end; a permanent connection is achieved through deformation caused by hammering or squeezing, making them non-detachable fasteners. They are classified by manufacturing process into hot-forged and cold-headed rivets; hollow or semi-hollow rivets are commonly used for joining lightweight materials such as leather, plastic, and wood.

11. Fastener Assemblies

These are composite fasteners consisting of a bolt, screw, or self-tapping screw paired with a washer. The assembly is designed so that the washer can rotate freely without detaching, and the unit is used as a whole for fastening connections.

12. Other Fasteners

Represented by weld studs, these are primarily used in specialized applications such as welded connections in steel structures.

 Principles for Fastener Selection

Standardization

Minimize the variety of fasteners used within a single piece of equipment or project to enhance manufacturing and assembly efficiency.

Cost-Effectiveness and Practicality

Prioritize the use of commercially available standard parts to control costs.

Selection Based on Requirements

Determine the fastener type and grade by considering the application environment, load magnitude, precision requirements, thread specifications, and mechanical properties.

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