1. Standards & Specifications
US Standards: Compliant with ANSI/ASME B18.2.2, ASTM A563, and SAE J995.
Thread System: Unified Thread Standard (UTS), including UNC (coarse) and UNF (fine) threads (e.g., 1/2″-13 for UNC).
Types: Regular hex nuts, heavy hex nuts (thicker for higher load), and locking nuts (nylon insert, metal prevailing torque).

2. Material & Grades
Carbon Steel: Grades 2 (low strength), 5 (medium), and 8 (high strength), often zinc-plated or phosphate-coated.
Stainless Steel: 304 (A2) and 316 (A4), ideal for corrosion resistance.
Special Materials: Brass (conductive) or nylon (insulating, vibration-resistant).

3. Key Features
Hexagonal Design: Compatible with standard SAE wrenches/sockets (e.g., 3/4″ wrench for 1/2″ nut).
High Torque Capacity: Heavy hex nuts withstand extreme loads in construction and machinery.
Locking Options: Nylon-insert or deformed-thread nuts prevent loosening in dynamic environments.

4. Applications
Automotive: Engine assembly, chassis components (e.g., Grade 8 for high-stress areas).
Heavy Machinery: Mining, agriculture, and construction equipment.
Infrastructure: Bridges, pipelines, and power plants (stainless steel for harsh environments).

5. Advantages
Interchangeability with US-standard bolts (ASTM A307, A325).
Robust performance in high-vibration and high-load scenarios.

Note: Match nut grade with bolt grade (e.g., Grade 8 nut for Grade 8 bolt) and select coatings (e.g., hot-dip galvanized) for outdoor durability.
Summary: US-standard hex nuts, defined by inch-based sizing and UTS threads, excel in reliability and versatility across North American industrial systems.