The basic knowledge of Hex Nut
2025-05-28
1. Definition
A hex nut is a six-sided (hexagonal) fastener with an internal threaded hole. It pairs with a bolt or threaded rod to clamp parts together.
2. Geometry & Dimensions
Hexagonal Shape: Six flat faces allow a wrench to grip from multiple angles.
Width Across Flats (WAF): Distance between two opposite flat sides; standard sizes correspond to bolt diameters.
Thickness: Typically close to the bolt’s nominal diameter (e.g., a 1/4″ nut is ~1/4″ thick).
3. Thread Types
Coarse Thread (UNC/Metric Coarse): Fewer threads per inch/mm; faster assembly, more tolerant of damage.
Fine Thread (UNF/Metric Fine): More threads per inch/mm; higher tensile strength, better for precise adjustments.
4. Materials & Finishes
Carbon Steel: Common, economical; often zinc-plated for corrosion resistance.
Stainless Steel (e.g., A2, A4): Excellent corrosion resistance; used outdoors or in corrosive environments.
Brass, Nylon, Alloy: Specialty applications (e.g., electrical conductivity, vibration resistance).
5. Strength Grades & Standards
Imperial Grades: Grade 2 (low), Grade 5 (medium), Grade 8 (high strength).
Metric Classes: 4.6, 8.8, 10.9, 12.9. Higher numbers = higher tensile strength.
Standards:
ISO 4032 / DIN 934 (metric hex nuts)
ASME B18.2.2 (inch hex nuts)
A563 (heavy hex nuts for structural bolts)
6. Variants
Standard (Hex): Most common.
Heavy Hex: Thicker and wider across flats; used with structural bolts.
Jam Nut: Thinner; used as a locknut.
Lock Nut: With nylon insert (nyloc), distorted threads, or metal insert to resist loosening.
7. Installation & Torque
Apply lubrication or use dry nuts depending on requirement.
Torque to manufacturer’s specification to ensure proper clamp load without over-stressing threads.
8. Applications
Machinery assembly
Structural connections
Automotive and aerospace
General-purpose fastening in construction and repair
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