1. Standards & Specifications
Imperial Standards: Compliant with BS 3692 (British Standard) or other imperial specifications, using inch-based sizing (e.g., 1/2″-12 BSW).
Thread System: Whitworth (BSW) coarse threads or BSF (British Standard Fine) threads (e.g., 1/2″-12 BSW).
Types: Regular hex nuts, heavy hex nuts (thicker design), and locking nuts (e.g., nylon insert).

2. Material & Grades
Carbon Steel: Grades 4, 8, or 10 (similar to SAE grades), often zinc-plated or hot-dip galvanized.
Stainless Steel: A2/A4 (304/316), resistant to corrosion.
Special Materials: Brass (electrical applications) or nylon (vibration resistance).

3. Key Features
Hexagonal Head: Compatible with imperial wrench sizes (e.g., 1/2″ nut fits 3/4″ wrench).
Thread Angle: 55° Whitworth thread profile (distinct from 60° metric/UTS threads).
Heavy-Duty Options: Thickened nuts (BS 3692 Heavy Series) for high-load applications.

4. Applications
Legacy Machinery: Maintenance of older British-made equipment or machinery.
Railway & Marine: Traditional imperial systems in rail components or shipbuilding.
Construction: Structural connections in regions using imperial standards.

5. Comparison with Metric Nuts
Unit System: Inches (imperial) vs. millimeters (metric).
Thread Standards: BSW/BSF threads (imperial) vs. ISO metric threads (e.g., M12).
Strength Marking: Grade-based (imperial) vs. numeric classes (e.g., 8.8 in metric).

Note: Ensure compatibility with imperial bolts (e.g., BSW threads). Avoid mixing with metric or UTS threads to prevent cross-threading.
Summary: Imperial hex nuts, defined by Whitworth threads and inch sizing, remain vital for maintaining legacy systems and machinery in the UK and Commonwealth countries, offering durability and historical compatibility.