Mastering Mil-Spec Dowel Pins: Fit, Material, and Series Made Simple

What Makes Mil-Spec Dowel Pins Different?

Mil-Spec (Military Standard) dowel pins are precision-ground, solid headless fasteners engineered for exact alignment, location, and secure assembly of components in aerospace, defense, and precision manufacturing.

They are produced under strict Mil-Spec specifications to ensure dimensional accuracy, repeatability, and conformance. Unlike commercial pins, Mil-Spec versions must be tested and certified for mechanical properties, hardness, and finish supported by documentation packages that may include Material Test Reports (MTRs), Certificates of Conformance (COCs), Heat Treat Certifications and DFARs compliance statements.

Dowel pins are commonly used as hinges, shafts, pivots, or locating devices to align or secure parts within precision assemblies or fixtures.

Four Common Mil-Spec Dowel Pin Series

Not all dowel pins are created equal. Each Mil-Spec series follows strict guidelines for fit, tolerance, material and other attributes to ensure accuracy and repeatability in demanding applications. Whether double-chamfered or featuring a radius and chamfer combination, these pins play a vital role in precision alignment. Below we deconstruct the taxonomy and attributes of the four series most frequently used in military and aerospace manufacturing.

1 – MS16555 — Standard Headless Dowel Pin (Press Fit)

Equivalent: Similar to ASME B18.8.2 standard series

Design: Straight, solid headless dowel pin normally made with a chamfered crown on one end and a chamfer on the other
Fit Type: Provides a standard interference/press fit
Tolerance: -0 / +0.0002 over nominal size
Material Options:
- MS16555-1 to -145: Steel (Carbon or Alloy), hardened
- MS16555-301 to -444: Phosphate-coated Steel, hardened
- MS16555-601 to -744: CRES 410/416 Stainless Steel, hardened and passivated
Diameter Range: 1/16″ (.0626–.0628) to 1″ (1.0001–1.0003)
Length Range: 3/16″ to 6″ (lengths over 3″ may be limited)
Applications: Ideal for vibration-resistant, high-strength alignment in aircraft and defense assemblies

➡️ Available for purchase online or RFQ

2 – MS16556 — Oversize Headless Dowel Pin (Extended Length / Oversize Fit)

Equivalent: Similar to ASME B18.8.2 oversize standard series

Design: Straight, solid headless dowel pin normally made with a chamfered crown on one end and a chamfer on the other (Similar to MS16555 with oversize tolerance)
Fit: Oversize interference fit
Tolerance: -0 / +0.001 over nominal diameter
Material Options:
- MS16556-1 to -144: Steel (Carbon or Alloy), hardened
- MS16556-301 to -444: Phosphate-coated Steel, hardened
- MS16556-601 to -744: Stainless Steel, hardened and passivated
- MS16556-801 to -944: Cadmium-plated Steel, hardened
Diameter Range: 1/16″ to 1″
Length Range: 3/16″ to 6″ (extended per spec; over 3″ limited)
Applications: Ideal for worn holes and to replace pins that no longer fit securely.

➡️ Now available for RFQ at mfsupply.com

MIL-P-21143 Series

3 – M21143/1 — CRES 303 Stainless Steel Dowel Pin (Press Fit)

Specification: MIL-P-21143

Design: Straight, headless pin with .015/.010 x 45° chamfer on both ends
Fit: Press fit — standard interference fit (referred to as “Oversize” in spec)
Tolerance: -0 / +0.0002 over nominal
Material: CRES 303 Stainless Steel
Diameter Range: 1/16″ to 1″
Applications: Used to join moving components or in high-precision assemblies requiring corrosion resistance and tight alignment

➡️ Available for RFQ at mfsupply.com

4 – M21143/2 — CRES 303 Stainless Steel Dowel Pin (Slip Fit / Undersize)

Design: Produced similar to M21143/1, straight, headless dowel pin with precision-ground surfaces, generally produces with a .015/.010 x 45° chamfer both ends
Fit: Slip fit — slightly undersized for easy removal or adjustment
Tolerance: +0 / -0.0002 under nominal diameter
Material: CRES 303 Stainless Steel.
Applications: Used in assemblies requiring frequent disassembly or maintenance; ideal for prototypes or variable-fit applications

➡️ Available for RFQ at mfsupply.com

Choosing the Right Material

Material	Key Traits	Common Uses
Alloy/Carbon Steel (Plain, Cadmium, Phosphate)	High strength, durable	Heavy-load or high-temp applications
CRES 410/416 Stainless Steel	Hardened, corrosion-resistant	Aerospace and defense
CRES 303 Stainless Steel	Corrosion-resistant, easy to machine	Slip-fit and/or precision alignment

All Mil-Spec dowel pins from MF Supply include Manufacturer’s Certificates of Conformance. Full certification packages — MTRs, Dimensional Reports, Heat-Treat, Passivation, and DFARS statements — are available upon request and may incur a fee.

👉 Checkout our Mil-Spec Precision Dowel Pins Cross-Reference Charts

Checklist: Sourcing the Correct Mil-Spec Dowel Pin

Before placing your RFQ or order, confirm:

Specification / Part Number – e.g., MS16555, MS16556, M21143/1, M21143/2. Check the diameter, length, tolerance, material and all specs to the Mil-Spec print.
Material & Finish – Match environment and strength needs.
Fit / Tolerance – Choose standard press fit, oversize, or slip fit as required.
Documentation – Determine your paperwork requirements at every stage of the process from initial RFQ to receiving inspection to insure audit readiness.

Mil-Spec Dowel Pins from MF Supply

MF Supply is your WBE/WOSB-certified U.S. distributor for certified, commercial, and custom dowel pins, including:

MS16555, MS16556, M21143/1, and M21143/2 series
Alloy and CRES Stainless Steel options
Certification packages (MTRs, COCs, Passivation, DFARS, Heat-Treat)
Fast RFQ turnaround and domestic stock for quick delivery
Made to order option for parts that are not COTs or for special sizes, materials and tolerances

We’re proud to announce that MS16556 dowel pins are now available for RFQ — joining our comprehensive Mil-Spec, metric, and precision dowel pin lineup.

👉 Visit MF Supply to request a quote or browse our catalog.

We are your Purchasing Department’s Secret Weapon for Mil-Spec hardware!

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.

Your Purchasing Department’s Secret Weapon!
Here are 5 reasons to buy from MF Supply

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.

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.

Your Purchasing Department’s Secret Weapon!
Here are 5 reasons to buy from MF Supply

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 Recertified as a Small Woman-Owned Business Enterprise!

Posted: January 22, 2025 | Author: mfsupplyblog | Filed under: Custom Fasteners per print, Domestic Fasteners, Electronic Hardware, Fasteners, Mil-Spec Fasteners, Panel Fasteners, Supply chain - manufacturing | Tags: Certifications, Fasteners, Fasteners Distributor, Fasteners Supplier, Hardware, Inclusion & Diversity, MF Supply Recertified, Mil-spec fasteners, Military Fasteners, SBE, Small Business Enterprise, Supply Chain Partner, WBE, Women Owned Business | Leave a comment

MF Supply, a leading distributor of fasteners and hardware, is proud to announce that we have successfully been recertified as a Women’s Business Enterprise (WBE) and Small Business Enterprise (SBE) by the state of New Jersey. This certification reaffirms MF Supply’s commitment to providing high-quality products while fostering diversity and inclusion in the manufacturing and distribution sectors.

How Does This Benefits You

Meet Your Diversity Goals: As a certified WBE and SBE supplier, we can help your business fulfill inclusion and diversity requirements while ensuring top-tier service and reliability.
Hard-to-Find Parts? Solved! From mil-spec fasteners to custom hardware, we specialize in sourcing hard-to-find components like Keensert® style key-locking inserts, helical inserts, dowel pins, socket head cap screws and more—all with precision and speed.
Decades of Expertise: Partner with a team that understands your needs. Whether it’s aerospace engineering, manufacturing, or government projects, we act as an extension of your purchasing departments providing lightning-fast responses, direct support, and competitive pricing.

Why Choose MF Supply?

With 50 years of fastener experience, we offer lightning-fast responses, direct phone support, free samples, and act as an extension of your team. We are fastener & sourcing experts, so you don’t have to be. With vast experience as a leading supplier and distributor of commercial and Mil-Spec fasteners, both in inch and metric sizes, we excel in providing:

A vast inventory of certified and commercial hardware with same-day shipping available.
Cost-effective solutions for OEM brand equivalents like McMaster-Carr, PEM, and RAF.
24/7 online shopping with a user-friendly experience at www.mfsupply.com.

Featured Products:

Some of our featured product lines include:

Manufacturers working with us can expect timely deliveries, competitive pricing, and access to expert guidance to help optimize their fastener choices. Visit our website, Connect with our team or send us a request for quote and our team of sourcing experts will help you find what you need. “Finding the right screw for you” is our tag line after all!

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.

Your Purchasing Department’s Secret Weapon!
Here are 5 reasons to buy from MF Supply

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].

Mil-Spec Fasteners in Stock at MF Supply

Posted: November 27, 2024 | Author: mfsupplyblog | Filed under: Mil-Spec, Mil-Spec Electronic Hardware, Mil-Spec Fasteners | Tags: Fasteners, Hardware, Mil-spec fasteners, Mil-Spec Fasteners Distributor, Mil-Spec Fasteners Supplier, Mil-Spec Helical Inserts, Mil-Spec Hex Head Cap Screws, mil-spec keenserts, Mil-Spec Self-Tapping Screws, Mil-Spec Set Screws, Mil-Spec Socket Head Cap Screws, Military Electronic Hardware Supplier, Military Fasteners, Military Fasteners Supplier, supply chain | Leave a comment

Are you searching for certified Mil-Spec fasteners to meet your bill of requirements (BOM) or project specifications? Look no further! MF Supply specializes in sourcing and supplying domestically manufactured AN, MS, and NAS Mil-Spec fasteners for aerospace, defense, and industrial applications. MF Supply stocks over 3,000 unique certified parts from the Qualified Suppliers List for Manufacturers & Distributors (QSLM & QSLD). Mil-Spec products stocked include Keensert® Style Key-Locking Inserts, Helical (HeliCoil®) Inserts, Precision Dowel Pins, Slotted Spring Pins, Extended Prong Cotter Pins, Nuts, Washers, Machine Screws, Precision Shoulder Screws, Hex Head Cap Screws/Bolts, Socket Head Cap Screws, Set Screws, Self-Tapping Screws and more. All Mil-Spec parts undergo rigorous testing and are DFARS or domestically manufactured with Certificate of Conformance (COC) and Material and Physical certification paperwork available to ensure compliance.

Buy Mil-Spec Fasteners and Precision Electronic Hardware at MF Supply!

We Have All the Mil-Spec Fasteners and Precision Hardware You Need

We offer a huge selection of DFARS certified and domestic Mil-Spec fasteners directly on our website, making it easier for you to find exactly what you need for your project at the click of a button or via RFQ depending on your preferred method of procurement. Below is a list of some of our most popular Mil-Spec product categories available:

1 – Mil-Spec Keensert® Style Key-Locking Inserts

Standards: MS51830, MS51831, MS51832, NA0146, NA0147, NA0148, NA0149, NA0150, NA0151, and NAS1395.
Styles: Miniature, Thin Wall, Heavy Duty, Thick Wall, and Extra Heavy Duty
Available Sizes: 2-56 to 1/2-13 Internal thread for inch sizes and M2 x 0.4 to M24 x 2 for metric sizes
Materials: 4140 alloy steel, Nitronic 60, CRES A286 and 303 series stainless steel
Applications: Can be used to create new threads, for thread reinforcement, and to repair stripped threads

2 – Helical Inserts (aka HeliCoil®)

Standards: MS121, MS122, MS124, MS21209, MA3279, and MA3329
Styles: Free-running and self-locking
Available Sizes: #2-56 to 1½-6 for inch sizes and M2 to M36 for metric sizes
Materials: CRES 300/18-8 stainless steel
Applications: Can also be used to create new threads, for thread reinforcement, to convert threads between inch and metric sizes, and to repair stripped threads

3 – Mil-Spec Precision Dowel Pins

Standards: MS16555, MS16556, and MIL-P-21143
Styles: Interference/Press Fit, Undersize/Slip Fit and Oversize +.001
Sizes: Diameters from 1/32 to 1 inch and lengths from 3/32 to 6 inches
Materials: CRES 303, 400, 416 series stainless steel
Applications: Can be used as a hinge, shaft, precise location device or pivot to align or secure parts within a precision assembly or fixture

4 – Mil-Spec Slotted Spring Pins

Standards: MS16562
Styles: Slotted
Sizes: Diameters from 1/16 to ½ inch and lengths from 3/16 up to 3 inches long
Materials: Alloy steel with a zinc phosphate finish
Applications: Can be used as a hinge or shaft for the purpose of securing and fastening components together

5 – Mil-Spec Extended Prong Cotter Pins

Standards: MS9245
Styles: Extended Prong
Sizes: Diameters from 1/32 to 5/32 inch and lengths from 1/4 to 1/2 inches long
Materials: T321 stainless steel
Applications: Designed to retain/secure a variety of fasteners such as bolts, nuts and pins in place and prevent them from sliding or coming out

6 – Mil-Spec Hex Finished Nuts

Standards: MS51967B & MS51967C
Styles: Grades B & C
Sizes: Stock sizes from 1/4-20 through 3/4-10 inches thread
Materials: Alloy steel with a cadmium yellow finish
Applications: Used to fasten parts together by pairing and tightly securing bolts in place

7 – Mil-Spec Hex Machine Nuts

Standards: MS35649 & MS35650
Available Sizes: Stock sizes from 2-56 through 3/8 thread
Materials: Alloy steel cadmium yellow and 300/18-8 series stainless steel
Applications: Typically paired with bolts or screws to ensure parts/components stay firmly fastened in place

8 – Mil-Spec Washers

Standards: MS51848, NAS620, MS35333, MS35335, MS35338, AN960, AN960-C, AN970, MS15795, MS27183, NAS1149 & NAS620
Styles: flat, light flat, flat machine screw, split lock, high collar split lock, internal tooth lock, and external tooth lock
Materials: Carbon steel, Alloy steel and 300/18-8, 316, 400 series stainless steel
Applications: Distribute the load of a fastener, such as a bolt or screw, over a larger surface area. This in turn helps reduce the effects of wear, damage or vibration on the fastener assembly by providing a cushion between the fastener head and the parent material

9 – Mil-Spec Machine Screws

Standards: MS24693, MS35190, MS35191, MS35206, MS35207, MS35265, MS35266, MS35275, MS35276, MS51957, MS51958, MS51959, & MS51960
Styles: 82d & 100d Flat Phillips, Drilled Slotted Fillister, Philips Pan Head
Available Sizes: Diameters range from 0-80 to 3/8-16 inches with lengths ranging from 3/32 to 3 inches long
Materials: Carbon steel, Alloy steel, and 300/18-8 series stainless steel
Applications: Often used in conjunction with other fastening elements, such as washers and nuts, they have uniform threads that when fastened engage with corresponding threads in a tapped hole or nut, creating a secure mechanical connection between components

10 – Mil-Spec Precision Shoulder Screws

Standards: MS51576 & MS51575
Styles: Hex and slotted drives
Available Sizes: Stock sizes range from 4-40 to 3/8-16 thread
Materials: 300/18-8 series stainless steel
Applications: Feature a cylindrical unthreaded shoulder that serves as a dowel or pivot point for rotating parts, also used to hold parts together within a precision assembly

11 – Mil-Spec Hex Head Cap Screws/Bolts

Style: Hex head
Standards: MS35307, MS35308, MS90725, MS90726, MS90728G & MS90727F, B1821
Sizes: Stock sizes range from 1/4-20 through 1-1/4 diameter
Materials: Alloy steel, 300/18-8 Series Stainless Steel
Applications: Their hexagonal heads allow for the application of high torque using a wrench or socket, which enables a very tight and secure fastening for load-bearing structures in military vehicles, aircrafts and more

12 – Socket Head Cap Screws

Style: Socket head
Standards: NAS1352C / MS16995, NAS1351C / MS16996, MS16997, MS16998, NAS1351N & NAS1352N, & MS24671
Sizes: Stock sizes range from 0-80 through 1-1/2 diameter
Materials: Alloy steel, 300/18-8 series stainless steel, A286
Applications: These screws have a cylindrical head with a hexagonal recess (socket) that allows for tightening with an Allen wrench/hex key. The socket head design allows for use in applications where there is limited space. The hexagonal socket allows for precise control during assembly, ensuring the screw is driven straight and accurately into the desired position

Can’t find what you’re looking for in the list above? Send us an RFQ with the product description or part number that you are looking for and our MF Supply team of sourcing experts will help find what you need!

Why Buy Mil-Spec Fasteners from MF Supply?

When precision, compliance, and reliability are non-negotiable, MF Supply stands out as a trusted partner for mil-spec fasteners. Here’s why industrial buyers across aerospace, robotics, defense, and manufacturing sectors turn to MF Supply:

Compliance and Certification: MF Supply’s mil-spec fasteners meet stringent U.S. Department of Defense (DoD) specifications, including MS51830, MS51831, and more. Each fastener is available with Material and Physical Test Reports, Certificates of Conformance, and DFARS/Domestic Statements—providing peace of mind for critical applications.

Sourcing Expertise: MF Supply works with the best factories across fastener categories, offering tailored solutions based on your budget, delivery and certification needs.

Reliability Across Critical Industries: Serving aerospace, defense, robotics, automotive, and manufacturing sectors for over 50 years, MF Supply is a trusted partner for industries where delivery times, precision and reliability are non-negotiable.

Shop Over 3,000 Unique Mil-Spec Fasteners and Precision Hardware Directly on Our Website!

Manufacturers working with us can expect timely deliveries, competitive pricing, and access to expert guidance to help optimize their fastener choices. Manufacturers eager to explore our Mil-Spec products’ catalog, including our other recently expanded product categories, are encouraged to visit our website at www.mfsupply.com, reach out to us at sales@mfsupply.com or request a quote. Our MF Supply team of sourcing experts will help you find what you need. “Finding the right screw for you” is our tag line after all!

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.

Your Purchasing Department’s Secret Weapon!
Here are 5 reasons to buy from MF Supply

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].

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MF Supply's experts discuss fasteners and electronic hardware

Mastering Mil-Spec Dowel Pins: Fit, Material, and Series Made Simple