Mil-Spec Socket Cap Screws: A Complete Buyer’s Guide

Posted: September 22, 2025 | Author: mfsupplyblog | Filed under: Mil-Spec, Mil-Spec Fasteners, MS16995, MS16996, MS16997, MS16998, MS24671, NAS1351, NAS1352, Socket Head Cap Screw | Tags: Fasteners, Guide, Mil-spec fasteners, Mil-Spec Fasteners Distributor, Mil-Spec Fasteners Supplier, Mil-Spec Socket Head Cap Screws, Military Fasteners, Military Fasteners Supplier, MS16995, MS16996, MS16997, MS16998, MS24671, NAS1351, NAS1352, Socket Cap Screws | Leave a comment

When it comes to aerospace, defense, and mission-critical industrial applications, not all socket cap screws are created equal. While commercial socket cap screws can be sufficient for general manufacturing, Mil-Spec socket cap screws are engineered, tested, and certified to meet the stringent requirements of the U.S. military and defense supply chain.

In this guide, we’ll cover:

• The variations of Mil-Spec socket cap screws
• Materials, platings, and optional features
• The part number taxonomy (MS, NAS, NASM, AN designations)
• How Mil-Spec differs from commercial socket caps
• Typical applications and industries
• MF Supply’s Mil-Spec socket cap screw catalog offerings

Variations of Mil-Spec Socket Cap Screws

Mil-Spec socket cap screws (sometimes called MS or NAS socket head cap screws) come in multiple variations to meet specific performance requirements: The 2 main Mil-Spec standards are:  

• Standard socket head cap screws – Cylindrical head, hexagonal drive. Designed for high-strength fastening where space is limited. 
• Flat socket cap screws – Used in clearance-sensitive applications where flush mounting is critical. 

Note: Low Head and Button Head socket cap screws do not have a Mil-Spec equivalent. 

Mil-Spec socket head cap screws come in several varieties, including: 

• Drilled heads (safety wire holes) – Feature cross-drilled holes in the head to allow safety wiring, preventing loosening in high-vibration environments like aircraft engines. 
• Thread-locking (pre-applied patch) – Includes a nylon or chemical locking element on the threads, providing resistance to vibration loosening. 
• Vent/drilled-through screws – Designed to eliminate trapped gas or contamination in vacuum or cleanroom environments. 

Note: Varieties including threadlocking, drilled heads and vented options are less common and may only be available per special order with minimums and lead times. 

Materials & Platings

Mil-Spec socket cap screws are offered in specific materials and platings with mechanical properties that meet or exceed ASTM/SAE standards. Common options include: 

• Alloy Steel – High tensile strength, black oxide or cadmium plated for corrosion resistance 
• CRES Stainless Steel (18-8/300 series stainless steel) – Corrosion resistance, often used in aerospace and marine environments 
• CRES A286 Stainless Steel superalloy – Extreme temperature resistance, high strength and with excellent corrosion & oxidation resistance 

Note: SS316 stainless steel is less common and may only be available by special order with minimums and lead times. 

Platings and Coatings: 

• Black Oxide (MIL-C-13924, Class 1) – Standard corrosion resistance 
• Cadmium Plating (QQ-P-416) – Excellent corrosion resistance and lubricity. Widely specified in legacy Mil-Spec standards. 
• Passivation (for stainless steels, QQ-P-35) – Removes surface contaminants and improves corrosion resistance. 

Part Number Taxonomy

Military grade fasteners or “Mil-Spec” fasteners are usually designated by an AN, MS, NAS or NASM prefix followed by a part number.  Each of these prefixes is an abbreviation: NAS stands for National Aerospace Standard and MS stands for Military Standard. 

The Defense Supply Center Philadelphia (DSCP), part of the DLA (Defense Logistics Agency), has a Qualified Suppliers List for Manufacturers (QSLM) identifying pre-qualified sources for certain products purchased by DSCP. Referred to also as the QPL (Qualified Products List), manufacturers on this list are recognized by DSCP as meeting all necessary criteria, particularly regarding quality control and paperwork.

Each part number defines key parameters: head style, material, finish, thread class, and whether features like drilled heads or locking elements are included.

The main core part numbers identifying standard Mil-Spec socket head cap screws are MS16995, MS16996, MS16997, MS16998, NAS1351, and NAS1352. Flat head socket head cap screws fall under parts MS24671 and MS24672.

• MS (Military Standard) – Legacy part numbers (e.g., MS16995), still widely used in aerospace and defense
• NAS (National Aerospace Standards) – High-performance standards developed for aerospace (e.g., NAS1351, NAS1352)
• NASM – Updated versions of NAS standards under SAE governance
• AN (Army-Navy) – Older standards, often superseded by MS or NAS numbers

The base part is followed by a Material Code:

• “-” = Alloy Steel 
• “C” = Corrosion Resistance Steel (18-8 stainless steel) 
• “N” = Heat-Resistant Steel (A286) 
• Let’s further break down a common Mil-Spec socket cap: 
• For example: NAS1352N028, sometimes written as NAS1352N02-8 
•  2-56 X 1/2 Mil-Spec Socket Head Cap Screw A286 Stainless Steel DFAR 
• NAS1352 = Coarse thread Socket Head cap screw 
• N = Heat-Resistant Steel (A286) 
• 02 = 2-56 Diameter 
• 8 = .500 or 1/2 screw length 

Note: The Aerospace Industries Association maintains an updated list of NAS parts available to members and/or for purchase. 

Why Mil-Spec Socket Caps Are Different from Commercial

Commercial socket caps may look identical to Mil-Spec socket caps.  However, commercial fasteners may lack the controlled processes, documentation, and certifications required for military or aerospace projects.   

Differences between Mil-Spec and commercial socket head cap screws may include: 

1. Certification & Paperwork 

Available Paperwork may include:  

• Manufacturer’s Certificate of Conformance (C of C) 
• Lot and heat traceability 
• Dimensional testing 
• Material Test Reports (MTRs) 
• DFARS compliance certification for defense projects 

2. Testing 

Mil-Spec socket caps undergo rigorous mechanical, dimensional, and sometimes nondestructive testing to verify hardness, tensile strength, shear strength, plating thickness, and more. 

3. Authorized Manufacturers 

Manufacturers listed on the QPL (Qualified Products List), the Qualified Suppliers List for Manufacturers (QSLM), or those approved under aerospace quality systems (AS9100, NADCAP for plating, etc.) are authorized to produce Mil-Spec socket caps. This ensures supply chain integrity and reliability in defense applications. 

Applications

Mil-Spec socket head cap screws are commonly used in: 

• Aerospace & Defense – Aircraft structures, engines, avionics, and ground support equipment 
• Military Vehicles & Marine – Tanks, ships, submarines, and defense electronics 

Other industries use Mil-Spec fasteners because of their quality and traceability.  Two examples include Precision Manufacturing where vibration, temperature extremes, or strict compliance require certified fasteners, and Medical & High-Tech Industries where cleanrooms, vacuums, or corrosive environments require traceability is essential. 

MF Supply’s Mil-Spec Socket Cap Offerings 

At MF Supply, we stock and source a broad catalog of Mil-Spec socket head cap screws including: 

• NAS1351 & NAS1352  
• MS16995, MS16996, MS16997, MS16998 
• MS24671 & MS24672 
• Variants with drilled heads, vent holes, and locking elements 
• Multiple materials, platings, and DFARS-compliant options 

We partner with only qualified U.S. and global manufacturers and provide full certification packages upon request. 

Beyond strength and performance, the real differentiators are the certifications, testing, and compliance requirements that ensure supply chain integrity. 

MF Supply has over 50 years of experience supplying Mil-Spec, DFARS-compliant, and certified hardware. Whether you need a handful of parts or long-term stocking solutions, we’re Your Purchasing Department’s Secret Weapon. 

👉 Explore Our Catalog of Mil-Spec Socket Cap Screws or Request a Quote today.

---

Book a one-on-one consultation with our President, Robin, to discuss how MF Supply can help you solve your Industrial Sourcing, Fastener, and Safety concerns.

---

---

• We Source and Deliver What Others Can’t, Faster Than You Imagined – With speedy solutions for elusive parts and lengthy delivery times – We’ve got you covered with both custom-made specials (send us your prints!) and hard-to-source options, quickly and at a fair price.
• Cost-Effective Functional Equivalents to OEM Brand Fasteners-Why Pay More? – Reduce lead times and costs with the same quality and same performance.  Try us for alternatives to brands like McMaster-Carr, MSC, Misumi, PEM, and RAF and experience unmatched savings! Same form, fit and function for less.  
• Huge Selection of Certified and Commercial Hardware with Same-day Shipping Available for Countless Items – We source and stock standards, specials, commercial, Mil-Spec & OEM brands in inch and metric sizes. Standards include AN, NAS, MS, IFI, ASTM, ASME, DIN, ISO, JIS. We are sourcing experts for inserts, certified Mil-Spec parts and anything in stainless steel. Many parts are available with manufacturers’ certifications, including DFAR, ROHS and CoC. Trust us to ship on-time from our national distribution centers. 
• A User-Friendly, 24/7 Online Shopping Experience – Enjoy a 24/7 online shopping experience with easy-to-use filters, detailed product information, and a constantly updated technical directory. Sign up now for a seamless experience! 
• WBE/WOSB Certified Woman-Owned Small Business – As a certified Woman-Owned Small Business, we support your diversity goals. Trust us to meet your fastener and sourcing needs with expertise and efficiency [Cage Code 58QG4].  

---

MF Supply is a WBE/WOSB certified supply chain partner to business, industry and government.  We are sourcing experts and stocking distributors of Hardware, Precision & Mil-Spec Fasteners and Safety supplies.  For more than 50 years, we have been supplying manufacturers in the electronics, industrial, commercial, aerospace and military markets with the full range of fastener products and services.  Our Cage Code is 58QG4 and our registered name is RL Supply Inc dba MF Supply.  

---