Mil-Spec

Military-specification fasteners for aerospace and defense-grade hardware requirements. Filter by type and size; confirm the governing specification on each product listing. For volume orders see Wholesale.

Military Specification Fasteners: Aerospace & Defense Grade Hardware

Military specification (Mil-Spec) fasteners represent the highest standard of quality, traceability, and performance in the fastener industry. Engineered to meet rigorous Department of Defense requirements, these fasteners are essential components in aerospace, defense, and critical infrastructure applications where failure is not an option. At Ecom Fasteners, we maintain comprehensive inventory of Mil-Spec machine screws, bolts, washers, pins, and socket head products—all backed by full certifications and material traceability.

Understanding Mil-Spec Part Numbering Systems

Military fasteners follow standardized part numbering systems that communicate precise specifications at a glance. Understanding these systems is essential for proper specification and procurement:

MS (Military Standard) Specifications

MS-numbered fasteners are the most common military specification format. The MS prefix indicates Military Standard, followed by a base number identifying the fastener type, and additional digits specifying size, length, and material. For example, MS16995 designates machine screws meeting specific thread, head style, and material requirements. MS numbers replaced many older AN specifications starting in the 1960s and remain the primary specification system for new military fastener designs.

AN (Air Force-Navy) Specifications

AN specifications originated during World War II as joint Air Force-Navy standards. While many AN specs have been superseded by MS numbers, several remain active and widely specified. AN960 flat washers are perhaps the most common example—these precision washers are specified by size and material, with cadmium plating standard for corrosion resistance. AN bolts, screws, and nuts continue to be specified in legacy aircraft and equipment maintenance.

NAS (National Aerospace Standard) Specifications

NAS specifications are developed by the Aerospace Industries Association and represent the highest performance tier of aerospace fasteners. NAS1149 flat washers, for instance, are precision aerospace washers manufactured to tighter tolerances than AN960. NAS bolts and screws often feature 12-point heads, higher strength materials, and enhanced fatigue resistance for structural aerospace applications.

Cadmium Plating vs. Zinc Plating: Critical Differences

Plating selection is critical in military applications, and understanding the differences between cadmium and zinc is essential for proper specification:

Cadmium Plating (QQ-P-416)

Cadmium plating has been the traditional standard for military fasteners due to its exceptional properties:

• Superior corrosion resistance in marine and high-humidity environments
• Excellent lubricity providing consistent torque-tension relationships
• Galvanic compatibility with aluminum alloys—critical for aerospace applications
• Self-healing properties where minor scratches don't compromise protection
• Thin, uniform coating that doesn't affect dimensional tolerances

Cadmium plating per QQ-P-416 Type II Class 3 remains specified for many aerospace and defense applications despite environmental regulations limiting its use in commercial applications.

Zinc Plating (ASTM B633 / MIL-DTL-41624)

Zinc plating serves as an environmentally-friendly alternative where cadmium's specific properties aren't required:

• Sacrificial protection where zinc corrodes preferentially to protect steel
• Lower cost and reduced environmental compliance burden
• Multiple chromate options including clear, yellow, and olive drab
• RoHS compliance for applications requiring lead/cadmium-free materials

For ground vehicles and non-flight-critical applications, zinc plating often provides adequate protection at lower cost.

Traceability Requirements: From Mill to Installation

Traceability is the cornerstone of military fastener quality assurance. Every Mil-Spec fastener must maintain documented chain of custody from raw material through final installation:

Material Certifications

All military fasteners require certified mill test reports (MTRs) documenting:

• Heat number and lot identification
• Chemical composition analysis
• Mechanical properties (tensile, yield, hardness)
• Material specification compliance (e.g., ASTM A574, AMS 5731)

Process Certifications

Manufacturing processes must be documented and certified:

• Heat treatment records with time, temperature, and quench media
• Plating certifications per QQ-P-416, AMS 2400, or applicable specification
• Thread inspection reports (thread ring/plug gage certification)
• Hydrogen embrittlement relief baking documentation

Certificates of Conformance

Each shipment includes a Certificate of Conformance (C of C) attesting that fasteners meet all specification requirements. For critical applications, First Article Inspection Reports (FAIR) document detailed dimensional and material verification.

DFARS Compliance and Domestic Sourcing

Defense Federal Acquisition Regulation Supplement (DFARS) requirements significantly impact military fastener procurement:

DFARS 252.225-7014: Specialty Metals

Fasteners containing specialty metals (certain steel alloys, titanium, zirconium) must be melted in the United States, its territories, or qualifying countries. This requirement ensures supply chain security for critical defense materials.

Berry Amendment Compliance

The Berry Amendment requires that certain items—including textiles and clothing but impacting some fastener applications—be domestically manufactured. Understanding which applications trigger Berry Amendment requirements is essential for defense contractors.

Country of Origin Documentation

All military fasteners must include country of origin documentation. Many specifications require domestic manufacture, while others permit qualifying country sources. Our inventory includes extensive domestic-manufacture options with full DFARS documentation.

Common Military Specifications We Stock

Machine Screws

MS16995 / MS16996 / MS16997 — Phillips and slotted pan head machine screws in various materials and platings. MS35206 / MS35207 — Fillister head machine screws. AN526 — Truss head machine screws for legacy applications.

Bolts

MS90725 / MS90726 — Hex head bolts. AN3 through AN20 — Clevis bolts, drilled head bolts, and standard hex bolts for aircraft applications. NAS6603 through NAS6620 — Close-tolerance bolts for structural applications.

Washers

AN960 — The standard military flat washer, available in regular and light series. NAS1149 — Precision aerospace washers with tighter tolerances. MS15795 — Lock washers meeting military specifications.

Pins

MS16555 / MS16556 — Cotter pins and safety pins. MS20392 — Straight pins. NAS561 — Hi-Lok collar pins for aerospace structural joints.

Socket Products

MS16995 variants with socket head configurations. NAS1351 / NAS1352 — Socket head cap screws per aerospace standards. MS21042 — Self-locking hexagon nuts often paired with socket head bolts.

Quality Assurance and Certification Support

Every Mil-Spec fastener from Ecom Fasteners ships with complete documentation:

• Full traceability to original mill heat numbers
• Certificates of Conformance per applicable specification
• DFARS compliance documentation where required
• Test reports for mechanical and dimensional properties
• Plating certifications with hydrogen embrittlement relief documentation

Our quality management system ensures that every fastener meets the exacting standards demanded by aerospace and defense applications. Whether you're maintaining legacy aircraft, manufacturing defense systems, or building critical infrastructure, our Mil-Spec fastener inventory provides the quality, documentation, and traceability your application demands.

Expert Technical Support

Navigating military specifications can be complex. Our technical team understands MS, AN, and NAS specifications and can help you identify the correct fastener for your application, cross-reference between specification systems, and ensure your procurement meets all applicable requirements. Contact us for specification assistance, custom packaging, or volume pricing on military fastener orders.