Mil-Spec Fasteners in Stock at MF Supply

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.


MF Supply Work With Us

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.  


Ultimate Guide: Inch, Mil-Spec, and Metric Keensert® Equivalent Cross Reference Guide!

At MF Supply, we spend a lot of time sourcing hard to find, back ordered, expensive, or out-of-stock OEM hardware brands. We do this in order to save money and to reduce long lead times for our customers, without sacrificing quality. In fact, you can find hundreds of registered trademark-branded fasteners and components in the industrial marketplace. Much like brand-name pharmaceuticals such as Tylenol and Advil are available generically as acetaminophen and ibuprofen, some brand name fasteners are also available as “generics,” “crosses,” “alternatives” or “functional equivalents.”

In the world of fasteners, a functional equivalent fastener is a part that is the same as the brand-name product in form, fit and function, including material and plating specifications, but is made by an alternative manufacturer.

Below, find a sample list of brands that have generic alternatives: 

3 STAR RIVETS USA, ABBATRON®, ALCOA, AMATOM®, APEX®, ARCONIC®, ATLAS®, AVDEL®, AVK®, B. F. GOODRICH, BOLLHOFF, BUCKEYE, CAPTIVE, CELUS®, CHERRY®, CONCORD, FASTENAL, GESIPA®, GRIPCO®, GLOBE ELECTRONICS, H. H. SMITH, HUCK, INDUX, INTERFAST, KEENSERT®, KEYSTONE, LOCTITE®, LYN-TRON, MACLEAN­ESNA®, MARSON®, MCMASTER-CARR, MISUMI, MSC INDUSTRIAL, PEM®, PIC DESIGN®, POP®, POWERS®, QUICKSCREWS, RAF, RED HEAD®, ROTOR CLIP®, SHEREX, SIMPSON, SOUTHCO®, SPS TECHNOLOGIES, TINNERMAN®, U. S. ANCHOR. VIP, W. M. BERG, W. W. GRAINGER, WALDES TRUARC®.

One example of an OEM hardware brand is the trademarked names Keensert®and Keysert®. Although the name Keensert® is often used to describe a Key-locking insert — like Band-Aid® is used to describe an adhesive bandage, or like Kleenex® is used to describe facial tissues — Keensert® is the registered trademark of Huck Patents; its close cousin, the Keysert®, is a registered trademark of Alcoa Fastening Systems.

The same key-locking inserts manufactured under the Keensert® and Keysert® brand names are also available (or have been available in the past, prior to industry consolidation) from alternative manufacturers under brand names such as Acme, Camloc, Clarendon, Fairchild, Kaynar, Microdot, Rexnord and Tridair. You may also find Keenserts® under their Mil-Spec numbers, which include MS51830, MS51831, MS51832 and NA series. Keenserts® come in imperial, metric and mil-spec sizes and materials.

Below, checkout our three most popular key-locking insert cross reference charts, to see if there is a functional equivalent to the Keensert® you need.

Keensert® Equivalent Cross Reference Charts: Find OEM Brands, Mil-spec & Functional Equivalents

Mil-Spec & Inch Keensert® Style Keylocking Inserts Cross Reference Chart – MS51830 | MS51831 | MS51832

Miniature, Thinwall & Lightweight, Heavy Duty, Extra Heavy Duty, Key-locking Inserts in Stainless Steel, A286, 4140 Alloy. Includes MS51830, MS51831, MS51832, NAS1394, NAS1395, KN, KNC, KNH, KNHX, KNL & KNCL Series.

Metric Keensert® Cross Reference Chart – 4140 Alloy | A286

Miniature, Thinwall & Lightweight, Heavy Duty, Key-locking Inserts in A286 and 4140 Alloy. Includes NA0146, NA0147, NA0148, NA0149, NA0150, NA0151, KN, KNC, KNL & KNCL Series.

Metric Keensert® Cross Reference Chart – Stainless Steel

Miniature, Thinwall & Lightweight, Heavy Duty, Keylocking Inserts in Stainless Steel, KN, KNC, KNL & KNCL Series.

MF Supply is a leading supplier of Keensert® style key-locking inserts including major brands and equivalents. We stock a huge inventory including Miniature, Thinwall, Lightweight, Heavy Duty, Extra Heavy Duty, Locking, Non-Locking, Solid and Floating style Keenserts®. Our Mil-Spec products are DFAR compliant with COC and full certifications available upon request.

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 product catalog, including our 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 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.


MF Supply Work With Us

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. 

Read More https://conta.cc/3r0B1Q3

Carbon Steel Key-Locking Inserts (AKA Keenserts®) at www.mfsupply.com

MF Supply is an expert and industry leader when it comes to key-locking inserts, commonly known by the popular brand name Keensert®. We stock and source key-locking inserts in a wide variety of materials, platings and sizes, including Inch, Metric, Commercial and Mil-Spec options.

In today’s blog, we will showcase a comprehensive overview of Carbon Steel Key-Locking Inserts, covering their benefits, uses, styles, standards, sizes, and comparison with other key-locking inserts made from other materials — so you are all set before jumping off to procure them for your next project.

What are Carbon Steel Key-Locking Inserts?

Carbon Steel Key-Locking Inserts, often referred to in industry vernacular as Carbon Steel Keenserts®, are precision-engineered threaded inserts predominantly fabricated from high-grade carbon steel.

Featuring both internal and external threads, these inserts are adept at providing wear-resistant thread interfaces in substrates that are inherently susceptible to thread degradation or are insufficiently robust for the intended mechanical loads. The external threading of these inserts exhibits a larger diameter and pitch compared to the internal threads, ensuring a secure engagement with the parent material.

These components are specifically designed for thread reinforcement and repair applications across a broad spectrum of parent materials. Their key-locking mechanism involves the deployment of keys integrated into the insert body. Upon installation into a pre-tapped hole, these keys are driven outward into the parent material, thereby affording a secure mechanical lock that resists rotational and axial forces. Hence, this feature is pivotal in applications where vibrational loads or cyclic stresses are prevalent.

The versatility of Carbon Steel Key-Locking Inserts makes them beneficial for any sector requiring durable, reliable threaded connections, especially where materials are subject to wear, high stress, or require thread repair and reinforcement.

Carbon Steel Keenserts®, or Key-Locking Inserts, have different styles in order to cater to a wide range of application requirements and material conditions. The distinct styles are designed to address specific challenges such as load capacity, space constraints, installation requirements, and the physical properties of the base material. Below is a list of all the styles available for these Key-Locking Inserts:

  • Thin Wall | RKKA | KNM: These are used when minimal space is available or in applications where less material needs to be removed. They offer a good balance between strength and size. Available off the shelf in Internal Thread 10-24 through 1/2-20 and Metric M5-M12. Often referred to by their original Fairchild part numbers: RKKA
  • Heavy Duty | RKK | KNHM: Designed for higher strength and durability, these are suitable for applications subject to high stress or where a stronger thread is required. Available off the shelf in Internal Thread 8-32 through 1-1/2, and Metric M4-M24. Often referred to by their original Fairchild part numbers: RKK
  • Extra Heavy Duty | KNHXH: These inserts are used in extremely demanding applications where very high pull-out and torque resistance is needed. Available off the shelf in Internal Thread 6-32 through 1-12. No standard Metric option available. Often referred to by their original Fairchild part numbers: KNHXH
  • Solid | KNJ: Unlike other types have both internal and external thread, solid inserts have only external thread. Once installed, they can be drilled and tapped as required. These solid inserts can be used to relocate misplaced holes, customize the internal threads, or plug existing holes.  They are extremely durable but might require more installation space. Available off the shelf in External Thread 3/8-16 through 1-1/4 and Metric M8-M32. Often referred to by their original Fairchild part numbers: KNJ.

Commonly available in diameters from 6-32 through 1-1/2, Carbon Steel Key-Locking Inserts can be used in a wide range of applications from small electronics to heavy machinery. The thread pitch varies accordingly, with finer pitches for delicate applications and coarser pitches for heavy-duty applications.

Carbon Steel Key-locking inserts are generally offered as commercial parts, and don’t have a Mil-Spec equivalent. They come standard with a phosphate finish.

*Note – Carbon Steel Key-locking Inserts do not come with a Self-Locking option, which is a standard option with Stainless Steel Keenserts®.

The Carbon Steel Difference!

How do Carbon Steel Key-Locking Inserts stack up against other materials? Here’s the breakdown:

  • Stainless Steel: Stainless Steel Keenserts® are known for their corrosion resistance, especially in marine and chemical environments. However, Carbon Steel Key-Locking Inserts are generally stronger and more wear-resistant, which is beneficial in applications where the primary concern is strength rather than exposure to corrosive elements.
  • 4140 Alloy Steel: This is a high-carbon alloy steel that provides excellent wear resistance and strength. While 440 Alloy Steel Keenserts® offer superior hardness, Carbon Steel Key-Locking Inserts typically excel in toughness and are more ductile, making them less likely to crack under high stress.
  • A286: A286 is an iron-nickel-chromium stainless steel alloy known for its high strength and corrosion resistance at elevated temperatures. Carbon Steel Key-Locking Inserts may not match the high-temperature performance but are significantly more cost-effective for applications where extreme temperatures are not a concern.
  • Nitronic 60: This material provides excellent galling and wear resistance. While it is superior in environments where these factors are critical, Carbon Steel Key-Locking Inserts offer a better balance of strength and cost-efficiency for general-purpose use.
  • Inconel: Known for its ability to withstand extreme temperatures and corrosion, Inconel is often used in high-temperature applications. Carbon Steel Key-Locking Inserts, on the other hand, are more widely used in applications where high temperature and corrosion are not as critical but where high strength and lower cost are important.

Hence, Carbon Steel Key-Locking Inserts offer an excellent balance of performance and value, making them a preferred choice for applications where the benefits of higher-cost, specialized materials are not required. They stand out for their strength, toughness, and cost-effectiveness, providing a reliable and affordable solution for thread reinforcement and repair.

Carbon Steel Key-Locking Inserts at MF Supply!

MF Supply is a WBE/WOSB certified business, and a leading supplier of Carbon Steel Key-locking Inserts (AKA Keenserts®) for manufacturers, government and industry. At MF Supply, we understand the dynamic needs of the industry, including the balance of price, quality, availability and certification paperwork. Ready to see how we can help you make a difference?

Visit our website or browse through the links provided below to discover the perfect Carbon Steel Key-Locking Inserts for your next project!

Inch Carbon Steel Key-locking Inserts:

Metric Carbon Steel Key-locking Inserts:

Note – Installation requires a drill bit, a standard tap, an installation tool, and a hammer. Feel free to ask us about Keensert® Kits available for many Carbon Steel sizes. Kits include a minimum of 2 inserts, a drill bit, a tap and an installation tool.

Do you still have questions or would like to speak with a representative? Reach out to us, and our MF Supply team of sourcing experts will help you find what you’re looking for. “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.


MF Supply Work With Us

Six Reasons To Buy From MF Supply

  • Creatively Solve Problems – We are sourcing experts and specialize in hard to find parts. We offer custom manufacturing and reworking solutions at competitive pricing, reducing long deliveries.
  • Functional Equivalents To Expensive Brand Names- We stock and source alternatives to brand name fasteners, reducing long lead times and saving you money.
  • Full eCommerce Enabled Website With Technical Manual Available 24/7 – Visit our website and Create a New Account, track online orders, browse our product catalog, check technical specs, subscribe to our blog, or buy online.  We are adding items and improving functionality daily!
  • Same Day Shipping From The USA – Our hardware products are in stock and ship to you directly from our USA based distribution centers. 
  • One-Stop Shopping On Certified Hardware – We stock and source a full line of fasteners including Mil-Spec, DFARS compliant and other industrial products.
  • WBE/WOSB Woman Owned Certified Small Business – To meet your diversity & set-aside needs.

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, with an expertise in inserts, military fasteners and stainless steel hardware.  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. 


Inch & Metric Nitronic Keenserts® Now Available at www.mfsupply.com!

In the bustling world of manufacturing and engineering, where every component counts and the margin for error is slim, MF Supply recognizes the intricacy involved in sourcing materials that offer both superior performance and extended durability. This is where our friends, the Key-locking Inserts (AKA Keenserts®) become the stars of the show. Today, we’re turning the spotlight on an insert that’s been making waves in the industry: the Nitronic 60 Key-locking Insert!

If you’re on the quest for Key-locking Inserts that promise to elevate the integrity of your projects, you’re in the right place. Nitronic 60 key-locking Inserts are not just components; they’re your peace of mind molded into high-performance alloy.

Why Nitronic 60 Key-locking Inserts? The Vanguard of Resilience

Picture a material that laughs in the face of wear, shrugs off corrosion, and doesn’t flinch under high torque. That’s Nitronic 60 for you — an alloy steel that’s as tough as they come. Crafted from this robust alloy, Nitronic Key-locking Inserts boast unparalleled wear and galling resistance. For those of you constantly battling the wear and tear that comes with mechanical demands, these threaded inserts are your knights in shining armor. Think of them as the silent guardians against the everyday wear-and-tear that can compromise your work.

The Rust Doesn’t Sleep, But You Can

Corrosion is the arch-nemesis of metal, lurking and waiting to undermine your structures. But with Nitronic 60’s exceptional corrosion resistance, rest easy knowing that your components are as steadfast as your ambition. Whether it’s the salty bath of marine environments or the demanding conditions of chemical processing, they’ve got you covered.

Strength That Speaks Volumes

Nitronic 60 Key-locking Inserts don’t just resist wear; they embrace strength. High stress, high torque — bring it on! The formidable might of Nitronic 60 makes these Key-locking Inserts the backbone for applications that can’t afford to falter, from the aerospace zeniths to the depths of automotive innovation.

The Nitronic 60 Difference

We hear you asking, “But how do they stack up against other materials?” Here’s the deal:

Nitronic 60, as a material, is a high-performance stainless steel alloy known for its excellent strength and resistance to wear and galling. This versatile alloy provides exceptional resistance to high temperature oxidation, crevice corrosion and general corrosion, making it well suited to marine and chemical applications. Key-locking inserts made from Nitronic 60 are used in various applications where high strength and corrosion resistance are a must.

  • Carbon Steel Inserts: Compared to standard steel, Nitronic 60 offers superior resistance to corrosion and galling.
  • Stainless Steel Inserts: Among stainless steels, Nitronic 60 typically outperforms varieties such as 304 or 316 in wear resistance.
  • Inconel Inserts: Inconel excels in high-temperature applications but comes at a higher cost and greater machining difficulty than Nitronic 60.
  • 4140 Alloy Inserts: 4140 Alloy provides greater tensile strength and enhanced performance at high temperatures, although it falls short in corrosion resistance and often necessitates protective coatings. Nitronic 60 is better suited for applications involving friction at moderate temperatures.
  • A286 Inserts: A286 excels in high-temperature applications, maintaining higher strength at elevated temperatures, though it’s tougher to machine and more expensive than Nitronic 60.

A Spectrum of Possibilities

We’re not about “one-size-fits-all” because we know your engineering needs are as unique as your blueprints. That’s why we offer Key-locking Inserts in inch, mil-spec and metric sizes that are tailored to the scope and scale of your vision — common internal diameters include #2-56 through 1 1/2-6 for inch & mil-spec sizes, and M2 through M24 for metric sizes. And with varying lengths at your disposal, the only limit is the application and your imagination. Materials

Compliance with stringent industry standards is not just a promise; it’s our practice. Our inserts meet or exceed critical aerospace and military specifications, ensuring that they deliver in applications where there is no room for error. Standards available include MS51830, MS51831, MS51832, NAS1394 and NAS1395. Series available include Miniature KNC, Thin Wall KN & KNM, heavy-duty KNH & KNHM, and extra heavy-duty series KNHXH.

Whether you’re in aerospace, automotive, defense, or any field that demands unyielding materials, these inserts are ready to serve. They’re the go-to for applications that require repeated assembly and disassembly, ensuring longevity and reliability every step of the way.

Discover More, Achieve More

MF Supply is a WBE/WOSB certified business, and a trusted supplier of Nitronic 60 Key-locking Inserts (AKA Keenserts®) for manufacturers, government and industry. Eager to delve deeper into the world of Nitronic 60 Key-locking Inserts? Visit our website, where innovation is just a click away, and join the ranks of manufacturers and engineers who don’t just build, but inspire.

With Nitronic 60 Key-locking Inserts, it’s not just about holding things together; it’s about unlocking possibilities. Discover the sizes, standards, and the success that our inserts can enable.

Inch & Mil-Spec Nitronic 60 Key-locking Inserts

Metric Nitronic 60 Key-locking Inserts

Do you still have questions or would like to speak with a representative? Reach out to us, and our MF Supply team of sourcing experts will help you find what you’re looking for. “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.


MF Supply Work With Us

Six Reasons To Buy From MF Supply

  • Full eCommerce Enabled Website With Technical Manual Available 24/7 – Visit our website and Create a New Account, track online orders, browse our product catalog, check technical specs, subscribe to our blog, or buy online.  We are adding items and improving functionality daily!
  • Same Day Shipping From The USA – Our hardware products are in stock and ship to you directly from our USA based distribution centers. 
  • Functional Equivalents To Expensive Brand Names- We stock and source alternatives to brand name fasteners, reducing long lead times and saving you money.
  • Creatively Solve Problems – We are sourcing experts and specialize in hard to find parts. We offer custom manufacturing and reworking solutions at competitive pricing, reducing long deliveries.
  • One-Stop Shopping On Certified Hardware – We stock and source a full line of fasteners including Mil-Spec, DFARS compliant and other industrial products.
  • WBE/WOSB Woman Owned Certified Small Business – To meet your diversity & set-aside needs.

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. 


“Heli-coils®” vs. “Keenserts®”: 3 differences you must know-Part 2 of 2

Welcome back to the second part of, “Heli-coils®” vs. “Keenserts®”: 3 differences you must know. As a refresher, both Helical Wire Inserts (AKA Heli-coils®) & Key-locking Inserts (AKA Keenserts®) are popular threaded inserts that are commonly used in precision manufacturing, transportation, and aerospace applications. Their uses overlap range from restoring/repairing stripped threaded holes, strengthening threaded holes in metals and other soft materials, providing high resistance to torque-out and pull-out, & to place threaded holes on materials too thin to accept them. The three main differences between Wire Inserts and Key-Locking Inserts lie in their strength, ease of installation & price. Today we will continue on from where we left of on our previous blog, and discuss about OEM brands, Mil-spec options, and how to order them!

Threaded Inserts’ Brands & Equivalents

A Helical Wire Insert, commonly known as “threaded wire insert,” is essentially a coil-wire made of stainless steel or other materials which, when installed, provide a new threaded hole surface. One of the most recognized brands for helical inserts is “Heli-Coil®,” but there are several others as well, including E-Z Lok, Bollhoff, Recoil, KATO, Perma-Coil, V-Coil and Time-Sert. Below is a list of some of the most well known brands for this category:

  • Heli-Coil®: Part of the Stanley Engineered Fastening brand, Heli-coil’s name is nearly synonymous with threaded wire inserts, and Heli-coil®is a registered trademark of Emhart® Teknologies, Inc.
  • Recoil®: Part of Howmet’s (previously Arconic, formerly Alcoa Fastening Systems) wire thread insert offering. Recoil offers helical wire inserts in bulk, replacement packets, kits and associated tools, taps and drill bits.
  • E-Z Lok®: Offering Wire Inserts under the E-Z Coil™ Helical Coil Insert brand, specializing in industrial and automotive .
  • KATO®: The Original Inventor & Manufacturer of the Bi-Directional Tangless Insert.

A Key-locking Threaded Insert, commonly known by the popular brand name “Keensert® and Keysert®,” is a solid bushing style threaded insert with unique external keys that get hammered into grooves through the threads—permanently locking the insert in place. Key-locking inserts are specifically designed for high-stress applications where strong, permanent threads are essential. Key-locking inserts offer exceptional resistance to vibration, torque-out and pull-out, making them suitable for critical components and assemblies that require a secure, immovable joint, or in scenarios where frequent assembly and disassembly might weaken the primary thread strength of the base material. While “Keensert®” is a trademarked name, tens of manufacturers and brands offer similar products in the solid threaded insert category including Acme, Camloc, Chrislynn, Clarendon, Fairchild, Loksert, Kaynar, Microdot and Tridair brands. Here is a list of the most popular brands:

  • Keensert®: is a registered trademark of Huck Patents, Inc. The trademark name is currently owned by the company that started it all, Howmet (formerly Arconic & Alcoa Fastening Systems).
  • Recoil®: The trademarked Keysert name belongs to Recoil, which is also part of the current Howmet family (formerly Arconic & Alcoa Fastening Systems).
  • Carr-Lane: Specializing in Tooling Components, Carr-Lane offers a large selection of Inch and Metric Key-locking inserts in steel and stainless steel.
  • Fairchild Fasteners®: Purchased by Arconic in 2002, Many original Fairchild part numbers are still produced and commonly used in the aerospace industry.
  • Acme – USA based manufacturers of inch, metric, Industrial Style and Mil-Spec key-locking inserts in a variety of materials and finishes.

Note: Various manufacturers and brands have their own designs, strengths, materials and applications for which they’re best suited. When choosing a threaded insert, it’s essential to consider factors like the material you’re working with, the stresses the insert will be under, and the expected lifecycle of the product. Industrial, automotive and aerospace industries each have their own requirements, which may include DFAR, First Article or other certifications. If you need assistance finding out what type of threaded insert is best suited for the project you’re working on, read part one of this blog, or reach out to us with your questions. MF Supply is an expert and leading supplier of Helical Wire Inserts and Key-locking Threaded Inserts—functional equivalents to top & expensive brands, such as Heli-Coil® & Keensert®.

Mil-Spec Options

Mil-spec Helical Wire Inserts (Heli-Coils®) are crafted to meet military specifications. They carry specific labels signifying their adherence to the rigorous standards established by the U.S. Department of Defense in order to guarantee that the inserts will fulfill the necessary requirements for military applications.

With that having been said, these threaded inserts often show up as free-running or self-locking inserts under their Mil-spec numbers, which can be crossed to commercial equivalents. Some common Mil-spec Helical Wire Inserts’ series include MS122076 through MS124831, MA1565, MA3276, MA3277, MA3278, MA3279, MA3280, MA3281, MA3329, MA3330, MA3331, , MS21208, MS21209, MS33537, NA0276, NAS1130

Mil-Spec key-locking threaded inserts (Keenserts®) adhere to distinct mil-spec (military specification) series. Options for these inserts include Miniature, Thinwall & Lightweight, Heavy Duty, Extra Heavy Duty, Keylocking Inserts in Stainless Steel, A286, and 4140 Alloy materials. Here are several prevalent mil-spec series associated with them: MS51830, MS51831, MS51832, NAS1394, NAS1395, NA0146, NA0147, NA0148, NA0149, NA0150, NA0151. The mil-spec parts will often have a commercial equivalent that is also known under the original Fairchild nomenclature, including the KN, KNC, KNH, KNL & KNCL Series.

Authentic Mil-spec parts will be available with documentation that confirm their compliance to the specification. Examples of certified paperwork might include a Certificate of Conformance, material traceability, DFAR statement, and chemical and/or physical tests reports.

How to Order

Now you know the differences between Helical / Heli-coils® and Key-locking / Keensert® / Keyserts®, the brands available, and the mil-spec series options.

To find the exact insert you are seeking on our website, there are currently four ways to proceed:

1. You can visit the Keenserts®, Threaded Inserts & Helical Wire Inserts category section of our website, and choose between Keenserts® for Manufacturers or Helical Wire Inserts. Once you select the desired category of products, you can then narrow down your search by selecting between metric or inch & mil-spec sizes, materials, etc.

2. You can also visit our website and enter the product standard, product number or keyword (e.g., MS51830, MS51830-101, “Keenserts,” “Helical Inserts,” etc.) in our search bar, and click the “Search” button. Once the list of available products are listed, you may use our product filters to search for the desired size, material, etc.

3. Alternatively, you could also use our newly added Product Finder tool! Select the desired Item Type, Subtype, Material, etc. And when you’re done selecting, simply click on the “Search” button, and the product finder will display a list of available products for you. 

4. Lastly, you could also reach out to us or Request a Quote. Our MF Supply team of sourcing experts are here to assist you and help you find the right product(s).

Once you find the insert you need, you can request a quote or buy online.

Key-locking Inserts (Keenserts®) & Helical Wire Inserts (Heli-Coils®) at MF Supply

MF Supply is a WBE/WOSB woman owned business, and leading supplier of Keenserts® & Helical Wire Inserts including major OEM brands and brand equivalents, in imperial, metric and mil-spec sizes and materials.

We stock a huge inventory including Miniature, Thinwall, Lightweight, Heavy Duty, Extra Heavy Duty, Locking, Non-Locking, Solid and Floating style Keenserts® in a variety of sizes and materials. Our mil-spec and certified insert products are DFAR compliant with COC and full certifications available upon request.

We Invite You To Request a QuoteDownload a Guide or a Line Card Today!

Do you still have questions or would like to speak with a representative to request a quote? Reach out to us, and our MF Supply team of sourcing experts will help you find what you’re looking for. “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.


MF Supply Work With Us

Six Reasons To Buy From MF Supply

  • Full eCommerce Enabled Website With Technical Manual Available 24/7 – Visit our website and Create a New Account, track online orders, browse our product catalog, check technical specs, subscribe to our blog, or buy online.  We are adding items and improving functionality daily!
  • Same Day Shipping From The USA – Our hardware products are in stock and ship to you directly from our USA based distribution centers. 
  • Functional Equivalents To Expensive Brand Names- We stock and source alternatives to brand name fasteners, reducing long lead times and saving you money.
  • Creatively Solve Problems – We are sourcing experts, offer competitive pricing and specialize in finding hard to find parts and reducing long deliveries.
  • One-Stop Shopping On Certified Hardware – We stock and source a full line of fasteners including Mil-Spec, DFARS compliant and other industrial products.
  • WBE/WOSB Woman Owned Certified Small Business – To meet your diversity & set-aside needs.

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.