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Fasteners are essential mechanical components that connect two or more parts to ensure stability and functionality. This guide will introduce common fastener types, their unique functions, and their main application scenarios.
1. Bolts
Bolts are robust fasteners consisting of a head and a threaded shaft, designed for strong, disassemblable connections.
Key Features:
Components: Composed of a head and a threaded body. Common head shapes include hexagonal, round, countersunk, and square. The shaft typically has a flat bottom.
Installation: Requires pre-tapped holes or nuts for fastening. Not ideal for very thin materials unless a nut is used.
Connection Type: Designed for use with nuts, allowing for strong, repeatedly disassemblable connections.
Common Applications:
Building & Construction: Essential for steel structure connections, bridge construction, and other heavy-duty applications.
Heavy Machinery: Used to secure motors, gearboxes, and other critical components in industrial machinery.
Automotive Manufacturing: Key for assembling engines, chassis, and other core vehicle parts.
Furniture Assembly: Facilitates the splicing and joining of larger furniture pieces like tables, chairs, and wardrobes.
2. Nuts
Nuts are internally threaded components designed to work in conjunction with bolts or screws, providing adjustable and secure fastening.
Key Features:
Internal Threading: Feature internal threads that match the external threads of bolts or screws.
Shapes & Types: Available in various shapes, including hexagonal, round, and square. Common types include hexagonal nuts, cap nuts, and wing (butterfly) nuts.
Adjustable Tightness: Allow for precise adjustment of tightening force.
Common Applications:
General Assembly: Widely used across machinery, construction, electronics, and many other fields when paired with bolts.
Manual Adjustments: Wing nuts (butterfly nuts) are ideal for applications requiring frequent, tool-free manual tightening, such as laboratory equipment, photographic gear, and quick-release mechanisms.
Important Note: To ensure a secure and durable connection, always match the nut’s internal thread to the bolt’s external thread. Additionally, ensure the strength grade of the nut and bolt are compatible to prevent failure.
3. Screws
Screws are versatile fasteners with a pointed end, allowing them to create their own threads or be driven into pre-drilled holes, often without the need for a separate nut.
Key Features:
Head Variety: Similar to bolts but with a wider range of head types, including Phillips (cross slot), slotted, pan, and countersunk. The bottom end is typically pointed.
Installation Simplicity: Can often be driven directly into thin metal sheets, plastic, or wood without pre-tapping or pre-drilling large holes. Generally provide a moderate level of fastening strength.
Common Applications:
Electronics: Crucial for securing casings of computers, mobile phones, and other electronic devices.
Woodworking: Ideal for connecting wooden boards, particleboard, and MDF in furniture and cabinetry.
Interior Finishing: Used for fixing gypsum boards, skirting boards, and other decorative elements.
Small Instruments: Employed to secure internal components of instruments and small machinery.
4. Washers
Washers are flat, annular (ring-shaped) components primarily used to distribute load, prevent loosening, and protect surfaces in a fastened joint.
Key Features:
Placement: Typically placed between the head of a bolt or nut and the surface of the connected part.
Pressure Dispersion: Distributes the fastening load evenly, preventing damage to the connected material.
Loosening Prevention: Increases friction and resistance to vibration, reducing the likelihood of loosening.
Sealing: Can prevent leaks (e.g., water, air) when used with appropriate sealing materials or specific washer types.
Common Applications:
Surface Protection: Used when connecting parts need protection from the tightening force of bolts or nuts.
Anti-Loosening: Essential in applications subject to vibration, such as under car tire bolts, to maintain joint integrity.
Sealing: Employed in plumbing (like faucet washers to prevent water leakage) or in systems requiring an airtight seal.
5. Rivets
Rivets are permanent mechanical fasteners that create a fixed joint by deforming one end of a pin-like shaft, forming a new head.
Key Features:
Structure: Consist of a head at one end and a pin-like shaft. Types include solid, hollow, and pull (blind) rivets.
Installation: Requires pre-drilled holes in both thin and thick parts. Professional tools are needed for installation.
Connection Type: Forms a permanent, non-disassemblable joint with high fastening strength.
Common Applications:
Aerospace: Critical for lightweight yet strong connections in aircraft skin and frame structures.
Automotive Manufacturing: Used for securing body panels, interior components, and structural elements.
Consumer Goods: Found in everyday items like luggage buckles, belt buckles, and metal furniture.
Construction & Fabrication: Ideal for splicing metal plates, such as in billboard frames and metal cladding.
6. Pins
Pins are cylindrical or conical fasteners primarily used for precise positioning, alignment, or light load transmission between components.
Key Features:
Shapes & Types: Common types include cylindrical pins (for precise fitting), conical pins (for self-locking and alignment), and cotter pins (for anti-loosening).
Function: Used for accurately locating parts, transmitting shear forces, or acting as anti-loosening devices.
Common Applications:
Mechanical Positioning: Essential for accurate alignment of parts in molds, jigs, and fixtures.
Connecting & Pivoting: Used as connecting elements in bicycle chains, door and window hinges, and clevis joints.
Anti-Loosening: Cotter pins are frequently used as a secondary locking mechanism to secure slotted nuts (e.g., on automotive half-axle nuts) or clevis pins, preventing them from backing off.
Fastener Types Summary
| Type | Main Details |
| Bolt | 1. Hexagon head bolt (most common, divided into full thread / partial thread) 2. Square head bolt (easy for wrench fixing, high torsional strength) 3. Countersunk head bolt (head can sink into the surface, aesthetic) 4. T-shaped bolt (used with T-shaped grooves, such as machine tool worktables) 5. Anchor bolt (fix equipment to the foundation, L-shaped / 9-shaped) |
| Nut | 1. Hexagon nut (standard type, thin type, thickened type) 2. Square nut (matching with square head bolts, good anti-loosening property) 3. Wing nut (can be hand-tightened without tools, suitable for scenarios requiring frequent disassembly) 4. Lock nut (such as nylon insert nut, flanged nut, anti-vibration loosening) 5. Cap nut (protects bolt threads, aesthetic and rust-proof) |
| Screw | 1. Machine screw (requires pre-drilled threaded holes, such as cross recessed / slotted screws) 2. Self-tapping screw (coarse thread, sharp tip, can tap threads by itself, used for thin metal / plastic) 3. Wood screw (shallow thread, sharp tip, used for wood connection) 4. Set screw (no head, positions by the tail against the part, such as hexagon socket set screw) 5. Eye bolt (head with a ring, used for lifting equipment) |
| Washer | 1. Flat washer (protects the surface, distributes pressure, divided into ordinary type and large type) 2. Spring washer (anti-loosening, offsets vibration through elastic deformation) 3. Lock washer (such as serrated lock washer, increases friction for anti-loosening) 4. Locking washer (such as single ear / double ear locking washer, fixed by bending to prevent nut rotation) 5. Sealing washer (rubber / metal material, used for pipeline connection sealing and leakage prevention) |
| Rivet | 1. Solid rivet (high strength, used for heavy-duty scenarios such as steel structures and ships) 2. Hollow rivet (lightweight, used for connecting soft materials like leather and plastic) 3. Blind rivet (also called pop rivet, fixed by rivet gun, single-sided operation, suitable for closed structures) 4. Drive rivet (no tools needed, fixed by tapping, for temporary connection) 5. Pan head rivet (semicircular head, common in steel structures and buildings) |
| Pin | 1. Cylindrical pin (fixed by interference fit, used for positioning or transmitting light loads) 2. Taper pin (1:50 taper, easy for disassembly and positioning, high precision) 3. Split pin (inserted into bolt slots or pin holes to prevent parts from falling off, such as fixing nuts) 4. Grooved pin (surface with grooves, fixed in the hole by elasticity, anti-vibration) 5. Dowel pin (with head, used for hinged connections, such as hinges and chains) |
Bolts, nuts, and screws are threaded fasteners commonly used for removable high-strength connections.
Rivets create permanent joints through deformation and are typically used in non-removable structures.
Washers enhance connection stability and are often used in layers depending on the application—such as for load distribution, vibration reduction, or surface protection.
Pins serve as positioning or anti-slip elements, primarily used in industrial machinery to ensure accurate alignment.
Material and Application Scenario Summary
| Category | Main Material Types | Application Scenarios |
| Bolts | 1. Carbon steel (Q235, 45# steel, 35# steel) 2. Stainless steel (304, 316, 316L) 3. Alloy steel (40Cr, 35CrMoA, high – strength) 4. Copper and copper alloys (Brass H62, Red copper T2, conductive/corrosion – resistant) 5. Titanium alloys (TA2, TC4, lightweight, high – temperature/corrosion – resistant) | Carbon steel: Low cost, moderate strength, suitable for ordinary mechanical connections. Stainless steel: Highly resistant to rust and corrosion, used in humid and corrosive environments, such as chemical and food processing equipment. Alloy steel: High strength (e.g., 10.9 – grade bolts), applied in heavy – load and high – pressure scenarios, like automotive engines and construction machinery. |
| Nuts | 1. Carbon steel (Q235, 45# steel) 2. Stainless steel (304, 316) 3. Aluminum alloys (6061, 7075, lightweight) 4. Brass (H59, H62, wear – resistant, easy to machine) 5. Plastics (Nylon, POM, insulating, corrosion – resistant) | Aluminum alloys: Lightweight, used in aerospace and electronic devices. Brass: Wear – resistant and not prone to rust, commonly used for water pipe and instrument connections. Plastics: Insulating and non – magnetic, suitable for electrical equipment or scratch – sensitive scenarios, such as medical devices. |
| Screws | 1. Carbon steel (Q235, 10B21) 2. Stainless steel (304, 316) 3. Brass (H65, H70, aesthetically pleasing) 4. Zinc alloys (formed by die – casting, used for decorative parts) 5. Titanium alloys (TC4, high – strength and lightweight) | Self – tapping screws often use carbon steel (with galvanized surface for corrosion protection). Brass screws: Aesthetically appealing, used for furniture and decorative items. Zinc alloys: Low cost and easy to form, but with lower strength, suitable for low – load scenarios, such as lighting fixtures and toys. |
| Washers | 1. Carbon steel (galvanized or blackened for corrosion protection) 2. Stainless steel (304, 316) 3. Copper (Red copper, Brass, conductive/heat – conductive) 4. Rubber (NBR, Fluororubber, for sealing and shock absorption) 5. Plastics (Nylon, PTFE, insulating, scratch – resistant) | Spring washers often use 65Mn spring steel (good elasticity). Sealing washers: Rubber materials are used to prevent pipeline leakage; PTFE is resistant to high temperatures and corrosive media, such as in chemical pipelines. Copper washers: Excellent electrical conductivity, used for electrical connections. |
| Rivets | 1. Aluminum alloys (5052, 6061, lightweight) 2. Carbon steel (Q235, 10# steel, with galvanized surface) 3. Stainless steel (304, 316) 4. Copper (Red copper T2, Brass H62, good conductivity) 5. Titanium alloys (TA1, TA2, high – strength and corrosion – resistant) | Blind rivets are mostly made of aluminum alloys (lightweight and easy to rivet), used in automotive and aerospace industries. Solid rivets commonly use carbon steel or stainless steel, used in heavy – load scenarios such as steel structures and ships. Copper rivets: Used for connecting electronic components and conductive parts. |
| Pins | 1. Carbon steel (45# steel, 20# steel, with surface quenching) 2. Stainless steel (304, 316) 3. Tool steel (T8, T10, high hardness, such as set pins) 4. Aluminum alloys (6061, lightweight) 5. Plastics (POM, ABS, insulating, low – friction) | Cylindrical pins and taper pins often use 45# steel (high hardness after quenching, providing precise positioning). Split pins commonly use low – carbon steel (Q215, easy to bend and shape); Plastic pins: Used in toys, medical devices, and other scenarios requiring insulation or low friction. |
Plastics and aluminum alloys are used for light loads and have low strength;
Carbon steel usually needs to be galvanized and blackened to prevent rust;
Stainless steel, titanium alloy, and copper alloy have high strength and strong corrosion resistance;
Alloy steel and tool steel have the highest strength and are suitable for high-load scenarios.
Special functions: copper material is selected for conductivity, plastic for insulation, rubber gasket for shock absorption, and aluminum alloy and titanium alloy for lightweight.
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