Hex flange screws serration under head, Hex flange bolts

   ISO: ISO 4162 (Metric) – Specifies dimensions for hex flange screws with serrations.
   DIN: DIN 6921 (Metric, common in Europe).
   JIS: JIS B 1189 (Japanese Industrial Standard).
   ANSI/ASME: Less common for serrated flange screws; typically replaced by ISO/DIN standards.

Grades/Classes:
   Metric Property Classes:
   Class 8.8: Medium strength (common for general use).
   Class 10.9: High strength (for heavy-duty applications).
   Class 12.9: Ultra-high strength (limited ductility).
SAE Grades:
   Grade 5 or Grade 8 (less common for flange screws).

Materials:
   Carbon Steel: Most common (e.g., ASTM A307, ISO 898-1).
   Alloy Steel: For higher grades (e.g., 10.9/12.9).
Stainless Steel:
   A2 (304): General corrosion resistance.
   A4 (316): Superior corrosion resistance (marine/chemical environments).
   Other: Brass, aluminum (niche applications).

Thread Types:
   Metric Coarse (M): Standard thread (e.g., M6, M8).
   Metric Fine (MF): Less common, used for precision adjustments.
   Unified (UNC/UNF): Rare for flange screws; typically ISO/DIN standards dominate.

Surface Treatments:
Zinc Plating:
   Electroplated (Zn): Basic corrosion resistance (e.g., white/blue/yellow zinc).
   Zinc Flake (Geomet): Superior corrosion/chemical resistance (e.g., DIN 267-10).
   Hot-Dip Galvanizing: Thick coating for outdoor use (may require re-tapping threads).
   Phosphate/Oil: Anti-friction and mild corrosion resistance.
   Dacromet: Non-electrolytic coating for high corrosion resistance.
   Stainless Passive: Natural oxide layer (no additional coating for A2/A4).
Anti-Loosening Features:
Serrations under the flange act as amechanical lock against vibration.
Alternative: Adhesive patches (e.g., Loctite) on threads.

✔ Anti-Loosening: Serrations grip the surface, resisting vibration.
✔ No Separate Washer Needed: Flange replaces a flat washer.
✔ Even Clamping Force: Flange distributes pressure, reducing damage to soft materials.
✔ Space-Saving: Combines head + washer into one part.

Automotive: Engine mounts, brackets, exhaust systems.
Machinery: Pumps, motors, gearboxes (high-vibration areas).
Electronics: Grounding connections (serrations improve conductivity).
Construction: Steel frames, HVAC systems.