创建于05.06

Types of Nuts: Classification, Characteristics, and Applications

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Table of Contents

  • Nuts Classified by Structural Design
  • Nuts Classified by Material Properties
  • Nuts Classified by Functional Purpose
  • Special-Purpose Nuts for Unique Applications

I. Nuts Classified by Structural Design

1. Hex Nut

  • Characteristics
    • Classic hexagonal shape for wrench/socket operation; available in standard, thin (30–50% reduced height), and thick (20–30% higher load capacity) versions.
    • Thread sizes range from M3 to M100+; surface treatments include zinc plating, dacromet (1000+ hours salt spray resistance), and black oxide.
  • Applications
    • General machinery assembly (gearboxes, bearing housings), structural steel connections (building frameworks), and automotive chassis fixing (suspension systems).

2. Flange Nut

  • Characteristics
    • Integrated circular flange at the base (diameter ≥ 1.5x nut width), with anti-slip teeth or rubber washers to increase contact area by 50%+ and reduce loosening from vibration.
    • Stress-free design for thin-walled component connections.
  • Applications
    • Vibratory equipment (engine cylinder bolts, hydraulic pipelines in construction machinery), and low-strength substrates (aluminum/plastic materials).

3. Wing Nut

  • Characteristics
    • Hand-tightened dual-wing design for tool-free installation/removal; torque capacity ≤15N·m (steel) or ≤5N·m (plastic); available in double-ear or single-wing types.
    • Materials: carbon steel (zinc-plated), stainless steel (304/316), or nylon (insulated and lightweight).
  • Applications
    • Laboratory instruments (fixture adjustments), equipment access panels (quick maintenance), and furniture hardware (detachable connections).

4. T-Slot Nut

  • Characteristics
    • T-shaped cross-section for sliding in extruded profiles (e.g., European-standard aluminum profiles, industrial steel structures); spring-loaded variants prevent rotation during installation.
    • Fits M4–M12 threads; materials: carbon steel (zinc-plated) or stainless steel (304).
  • Applications
    • Industrial automation (assembly of conveyor brackets), modular workbenches (flexible structure building), and exhibition displays (quick 拼接).

5. Nylon Insert Lock Nut

  • Characteristics
    • Internal nylon ring or elastic washer for friction-based anti-loosening (verified by torque-angle method); spark-free; temperature range: -40°C to 120°C.
    • Compliant with GB/T 889.1 and ISO 7042; available in all-metal (high-temperature) and non-metal (standard) versions.
  • Applications
    • Rail transit (bogie connections), aerospace (engine accessory fixing), and precision instruments (vibration resistance).

6. Cap Nut

  • Characteristics
    • Closed-top design (hemispherical/cylindrical) to protect bolt threads from corrosion and impact; surface finishes include chrome/nickel plating or plastic coating.
    • Materials: stainless steel or aluminum; fits M5–M30 threads.
  • Applications
    • Outdoor lighting (bolt protection for street lamps), medical devices (dust prevention), and decorative hardware (exposed connections in furniture/bathroom fixtures).

II. Nuts Classified by Material Properties

1. Metallic Nuts

  • Stainless Steel Nuts (304/316/316L)
    • Characteristics
      • 304: Resists general corrosion (≥48 hours salt spray); 316: Chloride-resistant (seawater/chemical environments); tensile strength 500–800MPa.
      • Food-grade compliance (316L) with no additional surface treatment needed.
    • Applications
      • Marine equipment (seawater cooling systems), chemical reactors (acid/alkali media), and food processing machinery (hygienic requirements).
  • Carbon Steel Nuts (4.8/8.8/10.9/12.9 Grades)
    • Characteristics
      • Clear strength grading (nominal tensile strength ×100MPa); quenched and tempered for grades ≥8.8; zinc/dacromet coating (500–1000 hours salt spray).
      • Cost-effective; matches high-strength bolts (e.g., 10.9-grade bolts with 10-grade nuts).
    • Applications
      • Bridge construction (high-strength bolt connections), heavy machinery (gearbox fastening), and automotive engines (cylinder head bolts).
  • Aluminum Alloy Nuts (6061/7075)
    • Characteristics
      • 1/3 the density of steel; strength ≤600MPa (suitable for M12 and below); paired with aluminum bolts to prevent galvanic corrosion.
      • Anodized surface for enhanced hardness and corrosion resistance.
    • Applications
      • Aerospace (aircraft lightweight components), drones (frame 减重), and sports equipment (bicycles/ski gear).

2. Non-Metallic Nuts

  • Plastic Nuts (Nylon/Polypropylene/ABS)
    • Characteristics
      • Insulating, chemically resistant (acid/alkali/salt); density ≤1.2g/cm³; temperature resistance ≤100°C (nylon)/70°C (polypropylene); load capacity ≤5kN (M8).
      • Customizable colors; RoHS-compliant.
    • Applications
      • Electrical equipment (PCB insulation), bathroom fixtures (moist environments), and children’s toys (safe, metal-free).
  • Ceramic Nuts (Alumina/Silicon Nitride)
    • Characteristics
      • High-temperature resistance (alumina ≤1600°C, silicon nitride ≤1200°C); high hardness (HV≥1500); excellent insulation; brittle (requires precise installation).
      • High cost, for extreme conditions only.
    • Applications
      • Aircraft engines (high-temperature turbine areas), semiconductor equipment (cleanroom environments), and nuclear facilities (radiation resistance).

III. Nuts Classified by Functional Purpose

1. Locking Nuts

  • Types & Characteristics
    • Friction-based
    • Mechanical interlock
    • Permanent lock
  • Applications
    • All dynamic load scenarios (vehicle suspensions, vibrating screens), safety-critical connections (pressure vessels, lifting equipment).

2. Weld Nuts

  • Characteristics
    • Protruding/angled bottom for resistance welding (spot/projection) to workpieces (plate thickness ≥1.5mm); eliminates pre-tapping, improving assembly efficiency by 30%.
    • Materials: low-carbon steel (SPCC); copper/zinc-plated for better weldability.
  • Applications
    • Automotive bodywork (door/chassis welding), home appliance casings (refrigerator/washing machine brackets), and prefabricated steel structures.

3. Expansion Nuts

  • Characteristics
    • Internal expandable sleeve (metal/plastic) that grips substrates (concrete/brick/gypsum board) when tightened; drill bit size must match (±0.5mm tolerance).
    • Types: knock-in (manual) vs. self-tapping (screw-driven expansion).
  • Applications
    • Construction (curtain rod/AC bracket fixing), equipment foundations (heavy machinery anchor bolts), and bridge bearing installations.

4. Self-Tapping Nuts

  • Characteristics
    • Threads with cutting edges for tapping into thin sheets (1–3mm thickness) without pre-drilling (hole diameter = thread minor diameter - 0.2mm); materials: carbon steel (zinc-plated).
    • Used with self-tapping screws for tight connections.
  • Applications
    • Automotive interiors (plastic/steel sheet joining), furniture panels (particleboard/plywood), and electronic enclosures (aluminum sheets).

5. High-Strength Nuts (Grade 10/12)

  • Characteristics
    • Compliant with ISO 898-2; medium-carbon alloy steel (Cr/Mo) quenched and tempered; minimum 310HV hardness, tensile strength ≥1000MPa.
    • Matched with 10.9/12.9-grade bolts; preload control required (torque/turn angle method).
  • Applications
    • Pressure vessels (flange connections), wind turbines (tower bolts), and construction machinery (hydraulic cylinder fixing).

IV. Special-Purpose Nuts

1. Blind Rivet Nuts

  • Characteristics
    • Hollow design installed via rivet gun, creating a back-side anchor from one side of the plate (suitable for enclosed cavities); available in countersunk/flat head.
    • Materials: carbon steel, stainless steel, aluminum; fits 2–5mm plate thickness.
  • Applications
    • Aerospace (aircraft skin bonding), rail transit (carriage interior fixing), and container manufacturing (sealed structures).

2. Trapezoidal Nuts

  • Characteristics
    • 30° trapezoidal threads (0.5P thread height) for ≥90% transmission efficiency; withstands bidirectional axial loads; integral or split design (easy disassembly); bronze alloy (excellent anti-friction).
    • Matches trapezoidal lead screws (T8/T12/T16).
  • Applications
    • Machine tool drives (ball screw-nut pairs), lifting platforms (screw jacks), and valve control mechanisms (opening/closing adjustment).

3. Pipe Nuts

  • Characteristics
    • Compatible with pipe threads (NPT/BSPT/G); sealed with tapered faces or gaskets (copper/PTFE); single/double-head types; pressure rating ≤30MPa (steel).
    • Zinc/nickel-plated; compliant with ASME B1.20.1.
  • Applications
    • Plumbing (union connections), gas systems (stainless steel pipe fixing), and hydraulic circuits (high-pressure hoses).

4. Eye Nuts

  • Characteristics
    • Top loop for lifting; marked with safe working load (e.g., 2t/5t/10t); used with shackles/slings; materials: alloy steel (quenched and tempered).
    • Threads must align precisely to avoid eccentric loading.
  • Applications
    • Lifting equipment (machine hoisting), industrial machinery (mold handling), and construction (prefabricated component lifting).

Selection Guidelines

  1. Load Requirements
  1. Environmental Conditions
  1. Installation Convenience
  1. Standards Compliance
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By matching nuts to specific operational needs, you ensure optimal fastening performance, safety, and cost-efficiency.

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