What Are Metal Fasteners?
Metal fasteners are mechanical components made of metal that are used to permanently or temporarily join two or more parts together. They do not rely on welding or adhesives but instead provide mechanical strength to hold parts together—and are often removable. They are among the most fundamental and widely used standard parts in modern manufacturing and engineering.
Primary Functions of Metal Fasteners
- Structural connection: Provide mechanical joining to maintain structural integrity
- Load transmission: Transfer tensile, shear, or torsional forces
- Disassembly capability: Enable easy assembly, disassembly, and maintenance
- Environmental adaptability: Withstand corrosion, high temperature, or pressure through proper material selection
Main Types of Metal Fasteners (by Structure and Function)
| Type | Description |
| Bolts | External threaded fasteners used with nuts for through-hole connections |
| Nuts | Internally threaded components used with bolts |
| Screws | Threaded fasteners that can be driven directly into materials, often without nuts |
| Washers | Discs placed under bolt heads or nuts to distribute load and prevent loosening |
| Studs | Headless bolts with threads on both ends, commonly used in flanged connections |
| Rivets | Permanent fasteners that are deformed after installation |
| Pins | Used for positioning, hinging, or light-duty fastening |
| Anchors | Expansion fasteners used in concrete or masonry |
| Clips/Clamps | Used to fix pipes, cables, or parts in place |
Common Materials and Properties
| Material | Characteristics | Applications |
| Carbon Steel | Low cost, high strength, poor corrosion resistance | General mechanical or structural use |
| Stainless Steel | Excellent corrosion resistance and appearance | Food processing, marine, medical |
| Brass (Copper Alloy) | Corrosion-resistant, conductive, aesthetic | Electrical connectors, decorative |
| Aluminum Alloy | Lightweight, rust-resistant, easy to form | Aerospace, light equipment |
| Nickel Alloys (e.g., Monel, Inconel, Hastelloy) | High-temperature and chemical resistance | Petrochemical, marine, nuclear |
| Titanium Alloy | High strength-to-weight ratio, corrosion-resistant | Aerospace, biomedical |
Standards for Metal Fasteners
Standardization ensures interchangeability, consistent quality, and global compatibility. Common standards include:
| Organization | Example Standards | Region/Notes |
| ASTM | ASTM A193, A194 | U.S. material standards |
| ASME | ASME B18.2.1, B18.3 | U.S. mechanical standards |
| ISO | ISO 4014, ISO 898 | International Organization for Standardization |
| DIN | DIN 931, DIN 933 | German standards |
| JIS | JIS B1180, B1181 | Japanese standards |
| GB | GB/T 5782, GB/T 6170 | Chinese national standards |
Application Fields
Metal fasteners are widely used in:
- Mechanical engineering (e.g., engines, machine tools)
- Construction and steel structures
- Automotive and transportation
- Petrochemical and chemical plants
- Aerospace and aviation
- Power and renewable energy systems
- Marine and offshore engineering
- Electronics and communication equipment
Key Considerations for Selecting Metal Fasteners
When choosing a metal fastener, consider the following:
- Operating environment (e.g., corrosion, temperature)
- Load type and strength requirements
- Assembly method and space constraints
- Material compatibility (to avoid galvanic corrosion)
- Reusability or disassembly needs
- Applicable standards or customer specifications
Main Manufacturing Methods of Metal Fasteners
| Method | Common Applications | Description |
| Cold Heading | Bolts, screws, rivets | Deforming metal blanks at room temperature using dies and high pressure |
| Hot Forging | Large bolts, studs | Forging metal at high temperature, suitable for high-strength or oversized fasteners |
| Turning (Machining) | Studs, custom fasteners | Using a lathe to shape parts and threads, ideal for small-batch custom parts |
| Thread Rolling | All types of threaded parts | Rolling external threads using dies without cutting, resulting in higher thread strength |
| Thread Tapping | Nuts and internal threads | Cutting internal threads with a tap |
| Milling/Drilling | Special-shaped fasteners | Used for slots, precise holes, or non-standard shapes |
| Heat Treatment | High-strength fasteners | Enhances mechanical properties such as hardness and tensile strength |
| Surface Treatment | All fasteners | Provides corrosion resistance, lubrication, or aesthetics (e.g., galvanizing, black oxide, Dacromet) |
Typical Manufacturing Process (Example: Bolt)
Step 1: Raw Material Preparation
- Start with steel wire rod or bar stock (carbon steel, stainless steel, alloy steel, etc.)
- Cut to desired length
Step 2: Cold Heading
- Use a cold heading machine to form the bolt head (e.g., hex, countersunk) via one or multiple strokes
- No heating required; fast, cost-efficient, and good for high-volume production
Step 3: Trimming & Chamfering
- Remove burrs and chamfer the end to prepare for threading
Step 4: Thread Rolling
- Use thread rolling dies to form threads on the bolt shaft
- No material is cut; the thread grain flows with the metal, making it stronger than cut threads
Step 5: Heat Treatment (if required)
- For high-strength bolts, perform quenching and tempering to meet mechanical standards (e.g., ASTM A193 B7)
Step 6: Surface Treatment
- Apply protective or functional coatings depending on use case:
Coating Method Purpose Electro/Hot-dip Galvanizing Corrosion resistance, bright finish Black Oxide (Phosphate) Rust prevention, good lubricity Dacromet High corrosion resistance, no hydrogen embrittlement Nickel/Chrome Plating Decorative, wear-resistant PTFE Coating Chemical resistance, anti-galling
Manufacturing of Nuts, Washers, Pins, etc.
- Nuts: Typically produced by cold or hot forging, followed by hole punching and internal thread tapping
- Washers: Usually made by stamping from sheet metal—ideal for high-volume production
- Rivets/Pins: Often produced via cold heading or cold extrusion, with optional machining for precision
Choosing the Right Process
| Conditions | Recommended Method |
| High-volume, standard parts | Cold heading + thread rolling |
| Large, high-strength parts | Hot forging + machining |
| Small-batch, precision parts | Turning + thread rolling/tapping |
| Special materials (e.g., titanium) | Heat treatment + protective coating |
Contact MT.BOLTS
MT.BOLTS specializes in the manufacturing and supply of industrial fasteners including screws, bolts, nuts, and washers. Our products conform to international standards (ANSI / ASTM / DIN / ISO / JIS) and are available in various materials, dimensions, and surface finishes.
Contact us today to learn more about fasteners and to procure high-quality products. Our technical team is ready to provide expert support and custom selection solutions.
