Home » M-Type Serrated Contact Conical Washers (NFE 25511) - Stainless Steel (A4)

M-Type Serrated Contact Conical Washers (NFE 25511) - Stainless Steel (A4)

M-Type Serrated Contact Conical Washers — NFE 25-511 | Stainless Steel A4 (SUS316)

FULLERKREG M-Type Serrated Contact Conical Washers in A4 Stainless Steel (SUS316 / 1.4401) conform to the French standard NFE 25-511. The conical (Belleville-style) profile combined with radial serrations on both faces delivers superior vibration resistance and reliable pre-load retention — ideal for marine, chemical, and high-corrosion environments where A2 grade is insufficient.

Product Overview

NFE 25-511 defines three washer types for different fastener head geometries. This listing covers Type M (M-Type) — designed for use with hex head screws and nuts. The M-Type features a larger outer diameter and is the most widely specified variant for general structural and industrial applications.

  • Standard: NFE 25-511 (French national standard, equivalent function to DIN 6796 / ISO 10673 serrated conical washers)
  • Type: M — For Hex Screws and Nuts
  • Material: A4 Stainless Steel (SUS316 / 1.4401)
  • Surface Treatment: Passivated & Whitened (Passivation)
  • Thread Range: M3 – M12
  • Function: Anti-loosening, vibration damping, pre-load maintenance

Dimensional Data — NFE 25-511 Type M (Stainless Steel A4)

All dimensions in mm. Data verified against NFE 25-511 standard catalogue.

Thread Size Inner Dia. d1 (Min) Outer Dia. d2 (Min) Outer Dia. d2 (Max) Height h (Min) Height h (Max) Thickness s (Min) Thickness s (Max)
M3 3.2 6.35 7.25 0.80 1.00 0.37 0.43
M4 4.3 8.55 9.55 1.00 1.20 0.47 0.53
M5 5.3 10.45 11.45 1.15 1.35 0.57 0.63
M6 6.4 12.61 13.61 1.30 1.50 0.67 0.73
M8 8.4 16.54 18.54 1.65 1.95 0.87 0.97
M10 10.5 20.58 22.58 2.00 2.40 1.07 1.23
M12 13.0 24.58 26.58 2.20 2.60 1.27 1.43

Note: All A4 Stainless Steel fasteners may exhibit slight magnetic properties due to the manufacturing process. Refer to ISO 3506-2 Annex I.

Selection Guide — NFE 25-511 Type Comparison

Type Designed For Fastener Head Style Relative Outer Diameter
Type M (this page) Hex screws & nuts Hexagonal head / nut bearing face Largest OD
Type B Cylindrical head screws Socket cap head (ISO 4762 / DIN 912 style) Medium OD
Type C Flat nuts & countersunk fasteners Countersunk / flat bearing surface Smallest OD

A4 vs A2 — Which Grade Should You Choose?

Property A2 (SUS304) A4 (SUS316) — This Page
Base Alloy 18% Cr, 8% Ni 16% Cr, 10% Ni, 2% Mo
Molybdenum Content None 2–3% — key for chloride resistance
Corrosion Resistance Good — indoor / mild outdoor Excellent — marine, chemical, coastal
Chloride Resistance Limited Superior (pitting & crevice corrosion)
Recommended Environment General industrial Marine, food processing, chemical plant
Price Standard Premium

Standard & Compliance

The NFE 25-511 standard is a French national standardisation specification governing serrated contact conical (Schnorr-type) washers. While largely superseded in new designs by DIN 6796 and ISO 10673, NFE 25-511 remains widely specified in:

  • French OEM and industrial legacy assemblies
  • Aerospace and defence sub-assemblies requiring French certification
  • Electrical panel and switchgear applications in corrosive environments
  • Marine and offshore equipment
  • Food processing and pharmaceutical machinery

FULLERKREG washers are manufactured to full NFE 25-511 dimensional and mechanical compliance. Material certification (EN 10204 3.1) available on request for bulk orders.

Material & Surface Specification

Property Specification
Material Grade A4 Stainless Steel (SUS316 / 1.4401)
Surface Treatment Passivated & Whitened
Corrosion Resistance Excellent — suitable for marine, coastal, and chemical environments
Magnetic Properties Slightly magnetic after cold forming (per ISO 3506-2 Annex I)
Temperature Range -196°C to +300°C (continuous service)
RoHS Compliant Yes

Key Features & Technical Advantages

  • 🔩 Conical spring action — maintains clamp load under thermal cycling and dynamic loads
  • 🔒 Radial serrations on both faces — bite into mating surfaces to resist rotation and self-loosening
  • ⚡ Electrical conductivity — serrations penetrate oxide layers for reliable grounding connections
  • 🌊 Superior corrosion resistance — A4 / SUS316 with molybdenum for marine and chemical environments
  • 📐 Precision manufactured — tight dimensional tolerances per NFE 25-511
  • 🏭 Bulk supply ready — available in full reels, bags, and custom packaging for production lines

Typical Applications

  • Marine and offshore structures, deck fittings, and hull assemblies
  • Coastal and waterfront construction
  • Food processing equipment and pharmaceutical machinery
  • Chemical plant pipework and pressure vessels
  • Swimming pool and water treatment installations
  • Electrical cabinets in humid or corrosive environments
  • Automotive and rail equipment in salt-spray zones

Product Gallery

M-Type NFE 25-511 Serrated Conical Washers — A4 Stainless Steel

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Why Choose FULLERKREG?

🏆 Standard Compliance — Full NFE 25-511 dimensional conformance, with DIN/ISO cross-reference support
🔬 Material Traceability — EN 10204 3.1 mill certificates available for A4 grade
📦 Flexible MOQ — Small batch samples to full production reels; custom packaging available
🌍 Global Shipping — Reliable export logistics to Europe, North America, Southeast Asia, and beyond
💬 Technical Support — Engineering team available for selection guidance, substitution advice, and custom specifications
⚙️ Broad Range — Complementary washer types (Type B, Type C) and related DIN/ISO standards stocked

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