Home » NFE 25-511 M-Type Serrated Contact Conical Washers 430-500 HV Grade Zinc Yellow

NFE 25-511 M-Type Serrated Contact Conical Washers 430-500 HV Grade Zinc Yellow

NFE 25-511 M-Type Serrated Contact Conical Washers — 430–500 HV | 65Mn Spring Steel | Zinc Yellow

FULLERKREG NFE 25-511 M-Type Serrated Contact Conical Washers in 65Mn Spring Steel with Zinc Yellow (yellow chromate zinc plating) surface treatment deliver high hardness (430–500 HV), strong spring-back force, and reliable anti-loosening performance. The distinctive yellow iridescent finish provides enhanced corrosion protection and is widely recognised in industrial fastener applications worldwide.

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 serrated conical washers)
  • Type: M — For Hex Screws and Nuts
  • Material: 65Mn Spring Steel
  • Hardness: 430–500 HV
  • Surface Treatment: Zinc Yellow (Yellow Chromate Zinc Plating)
  • Thread Range: M3 – M12
  • Function: Anti-loosening, vibration damping, high pre-load maintenance

Dimensional Data — NFE 25-511 Type M (65Mn / Zinc Yellow)

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: Zinc Yellow plating thickness is typically 5–12 μm. Actual installed dimensions may vary slightly due to plating layer. Confirm with FULLERKREG technical team for tight-tolerance applications.

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

Zinc Yellow vs Zinc Cr3 — Surface Treatment Comparison

Property Zinc Yellow (This Page) Zinc Cr3
Chromate Type Yellow chromate (Cr6 / hexavalent) Trivalent chromate (Cr3)
Appearance Iridescent yellow / golden Bright silver / blue-silver
Salt Spray Resistance ≥200 hours NSS (ISO 9227) ≥120 hours NSS (ISO 9227)
Corrosion Resistance Superior Good
RoHS / ELV Compliant ⚠️ No — contains Cr6 ✅ Yes — Cr3 only
Automotive / Electronics Use Restricted (check supply chain requirements) Fully compliant
General Industrial Use ✅ Widely used ✅ Widely used

Important: Zinc Yellow (Cr6) finish offers superior corrosion resistance but contains hexavalent chromium. Please verify compliance requirements with your end-customer or supply chain before specifying. For RoHS/ELV-restricted applications, please refer to our Zinc Cr3 variant.

Material Grade Comparison — 65Mn vs Stainless Steel

Property 65Mn Spring Steel + Zinc Yellow (This Page) A2 Stainless Steel A4 Stainless Steel
Hardness 430–500 HV ~200–300 HV ~200–300 HV
Spring-back Force High Medium Medium
Pre-load Retention Excellent Good Good
Corrosion Resistance Superior (Zinc Yellow plated) Good (passivated) Excellent (passivated)
Suitable Environment General industrial, outdoor Mild outdoor / indoor Marine / chemical
RoHS Compliant ⚠️ Check application (Cr6) Yes Yes

Surface Treatment — Zinc Yellow Explained

Zinc Yellow (yellow chromate / iridescent yellow zinc plating) is a traditional electroplating process combining electrolytic zinc deposition with hexavalent chromium (Cr6) passivation. It is one of the most widely used industrial surface treatments for carbon and spring steel fasteners, offering:

  • 🛡️ Superior corrosion resistance — typically ≥200 hours neutral salt spray (NSS) per ISO 9227
  • 🌈 Distinctive yellow / golden iridescent appearance — easy visual identification in mixed fastener assemblies
  • 🔧 Plating thickness — typically 5–12 μm electrolytic zinc with Cr6 chromate passivation topcoat
  • ⚡ Good electrical conductivity — zinc layer maintains conductivity for grounding applications
  • 🏭 Cost-effective — economical surface protection for high-volume industrial production
  • ⚠️ Compliance note — contains hexavalent chromium (Cr6); not suitable for RoHS / ELV restricted supply chains

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
  • Automotive and rail sector maintenance parts (non-RoHS restricted)
  • Electrical panel and switchgear applications
  • Heavy machinery and construction equipment
  • General mechanical engineering assemblies requiring enhanced corrosion protection

FULLERKREG washers are manufactured to full NFE 25-511 dimensional and mechanical compliance. Material and surface treatment certification available on request for bulk orders.

Material & Surface Specification

Property Specification
Material 65Mn Spring Steel
Hardness 430–500 HV
Surface Treatment Zinc Yellow (Yellow Chromate Zinc Electroplating)
Plating Thickness 5–12 μm (typical)
Salt Spray Resistance ≥200 hours NSS (ISO 9227)
Chromate Type Hexavalent Chromium (Cr6) passivation
RoHS Compliant ⚠️ No — contains Cr6 (verify application requirements)
Temperature Range -40°C to +120°C (continuous service)

Key Features & Technical Advantages

  • 🔩 High hardness 430–500 HV — superior spring-back force vs stainless steel grades
  • 🔒 Radial serrations on both faces — bite into mating surfaces to resist rotation and self-loosening
  • 🛡️ Zinc Yellow surface protection — ≥200h NSS corrosion resistance for demanding industrial environments
  • 🌈 Distinctive yellow finish — easy visual identification and inspection in assembly lines
  • 📐 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

  • Automotive body, chassis, and powertrain assemblies (non-RoHS restricted)
  • Industrial machinery and heavy equipment subject to vibration
  • Electrical cabinets, control panels, and switchgear
  • Rail and transportation equipment
  • Construction steel structures and prefabricated buildings
  • Agricultural and off-highway equipment
  • General mechanical engineering assemblies requiring enhanced corrosion protection

Product Gallery

NFE 25-511 M-Type Serrated Conical Washers — 65Mn Spring Steel / Zinc Yellow

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Why Choose FULLERKREG?

🏆 Standard Compliance — Full NFE 25-511 dimensional conformance, with DIN/ISO cross-reference support
🔬 Material Traceability — 65Mn spring steel mill certificates and Zinc Yellow plating reports available on request
📦 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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