Flat Washer

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Flat Washer

Flat washers are thin, circular plates with a central hole, used in conjunction with bolts, screws, and nuts to distribute load, reduce surface damage, and improve joint stability. They act as a protective interface between the fastener and the mating surface, preventing embedding, wear, and loosening under load.

Types of Flat Washers
  • Plain Flat Washer: Standard washer for general-purpose applications
  • Hardened Washer: Heat-treated for high-strength bolting applications
  • Fender Washer: Larger outer diameter for increased load distribution
  • Square Washer: Used in structural and timber applications
  • Stainless Steel Washer: Corrosion-resistant for harsh environments

Applicable Standards

Dimensional Requirements:
  • ASME B18.22.1 – Plain washers (inch series)
  • DIN 125 / DIN 126 – Metric flat washers
  • ISO 7089 / ISO 7090 – Metric washers (normal and chamfered)
  • ASTM F436 – Hardened washers (structural applications)
Material Grades:
  • Carbon Steel: General-purpose applications
  • Hardened Steel (ASTM F436): : High-strength and structural use
  • Alloy Steel: For high-load and critical applications
  • Brass / Non-metallicElectrical or specialized uses
Material Grades (Commonly Used)

High Tensile, Stainless Steel, Alloy Steel, Inconel, Incoloy, Hastelloy, Monel, Silicon Bronze, Phosphor Bronze, Aluminium Bronze, Nickel, Brass, Copper, Copper Nickel,Duplex, Super Duplex, Titanium Alloys, CB20, Nitronic, Nimonic, ASME, ASTM etc…

Technical Specifications
  • Inner Diameter (ID): Matches bolt size
  • Outer Diameter (OD)::Varies depending on load distribution requirement
  • Thickness: Standard or heavy-duty as per application
  • HardnessAs per ASTM or ISO specification (for structural washers)
Surface Protection / Coating:
  • PTFE Coated (Blue, Yellow, Red, Green & Black)
  • Hot Dip Galvanized
  • Yellow Zinc Plated or Cadmium Plated
  • Blue Zinc Plated
  • Molykote
  • Aluminium Zinc Flake Coated
  • Black Phosphate
  • Zinc Plated
  • Nickel Plated
  • Polished / Chrome plated (decorative)
Engineering Applications
  • Structural steel connections
  • Machinery and equipment assembly
  • Automotive and mechanical systems
  • Piping and flange connections
  • Wood and soft material fastening
Performance & Key Features
  • Distributes load evenly across the surface
  • Prevents damage to mating surfaces
  • Reduces risk of loosening due to vibration
  • Improves joint stability and durability
  • Compatible with all standard fasteners
Design Considerations
  • Select appropriate washer size (ID/OD) based on bolt and load
  • Use hardened washers with high-strength bolts (e.g., ASTM A193 B7)
  • Ensure proper coating for corrosion resistance
  • Use larger OD washers for soft materials (wood, aluminum, etc.)