“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. 


“Heli-coils®” vs. “Keenserts®”: 3 differences you must know-Part 1 of 2 (Refreshed for 2023)

Today we will re-introduce you to our blog, “Heli-coils®” vs. “Keenserts®”: 3 differences you must know-Part 1 of 2, published back on 2020. We will compare these two fastener products that are used to repair damaged threads & threaded holes, or to strengthen/reinforce a weaker parent material like aluminum. Both Helical Wire Inserts & Key-locking Inserts are commonly used in precision manufacturing, transportation and aerospace applications. Their versatility, however, ensures their presence in nearly every industry that utilizes threaded fasteners.

What are the main uses of Threaded inserts?

Both “Heli-coil®” or Helical wire inserts and “Keensert®” or Key-locking inserts fall under the “Threaded Insert” category of fasteners.

Threaded insert, also known as a threaded bushing, is an insert that has internal threads, and is fastened into an object to add or reinforce a threaded hole.  Threaded inserts may be used to repair a stripped threaded hole, provide a durable threaded hole in a soft material, place a thread on a material too thin to accept it, mold or cast threads into a work piece thereby eliminating a machining operation, or simplify changeover from unified to metric threads or vice versa. Although Helical Wire inserts and Key-locking externally threaded inserts are used in similar ways, there are 3 main distinctions that we detail below. But first, let’s take a closer look at each of these fasteners:

What is a Helical Insert Wire Insert? (aka Heli-coil®)

Helical wire inserts are precision-formed continuous wire coils that provide permanent, wear-resistant threads which exceed the strength of the parent material. Often underestimated, the popular misconception is that Helical wire inserts are intended solely for thread repair, when, in fact, they have other significant uses.  Not to be confused with other types of threaded inserts or rivnuts, Helical wire inserts resemble springs and are sometimes referred to as “Screw Thread Inserts (STI)” ,“Helicals” or by the popular brand “Heli-Coil®” which is a registered trademark of Emhart® Teknologies, Inc.

Three typical applications for using Helical wire inserts are:

  • to repair damaged threads in parts that would otherwise have to be scrapped
  • to strengthen threads against failures due to stripping, seizing or corrosion
  • to convert threads between inch and metric sizes

What is a Key-locking insert? (aka Keensert® or Keysert®)

The Key-locking threaded insert is a solid bushing style insert that is threaded on both the inside and the outside and has wedges or “keys” attached to the top of the insert. These externally threaded inserts are used to distribute loads and repair or strengthen threads against failures due to stripping, seizing or corrosion. Key-locking inserts are commonly used in high torque and high temperature situations, and in applications where fasteners may be repeatedly removed and reassembled. Key-locking inserts are often referred to as Keenserts® and Keyserts®, which are registered trademarks for the most popular brand names for this part. (Keensert® is a registered trademark of Huck Patents, Inc. & Keysert® is a registered trademark of Alcoa Fastening Systems).

Typical applications are transmission housings, electronic equipment and suspension units. Key-locking inserts are commonly found in aerospace assemblies.

How do they work?

Helical wire inserts work because the diamond shaped helically formed wire coil screws into a threaded hole to form a mating internal thread for a screw or stud.  

Key-locking inserts are threaded into a pre-tapped hole, and then the keys are hammered into grooves through the threads, permanently locking the insert in place. Their “keys”, which are driven down into the tapped threads, provide a mechanical lock against rotation, especially when the mating stud or bolt will be removed frequently.

What materials, sizes and styles are available?

Key-locking Inserts/ Keenserts®

Key-locking inserts come in four main styles: Miniature, Thin Wall, Heavy Duty Wall (general purpose) and Extra Heavy Duty.

  • Miniature Key-locking inserts are used in electronic and aerospace applications where size and strength are critical. These inserts may be installed in sheet material as thin as 1/16″.
  • Thinwall inserts have smaller external threads than standard heavy-duty inserts and are ideal for tight spaces where less pull-out strength is acceptable.
  • Heavy Duty inserts have a thick, heavy-duty thread wall, suitable for most applications.
  • Extra-heavy duty inserts are used in oversized and overly worn holes.

Key-locking inserts can be internally self-locking or non-locking (the standard is non-locking and is sufficient for the most common applications).

Inserts with the internal self-locking feature are designed to securely lock a bolt when it is entered into the insert only a few turns. Even after repeated installations and removals of the bolt, the lock maintains sufficient locking torque to prevent the bolt from vibrating out.

Common Materials available include Carbon steel, Stainless Steel, Alloy 4140 and A286. Nitronic and other materials may be available with a lead time.

Internal Diameters available: American/Inch #2-56 to 1 ½-6 ” and Metric M2 to M24

Helical wire inserts / Heli-Coils®

Helical wire inserts come in 2 main styles: tanged and tangless (currently, MF Supply specializes in the tanged style).

The original and widely used tang style has a prong at one end to facilitate installation. The newer tangless style has no prongs to break off, retrieve, or lose. Tangless inserts are commonly used in electronic applications where loose tangs are might cause damage.

Helical wire inserts can be free-running or self-locking.

Free running is the most common style used for thread repair. The “free” diameter of the insert is larger than the installed diameter and this configuration generates balanced pressure distribution between the coils and threads.

Self-locking style inserts are recommended for applications that require constant torque, or are subject to stress or vibration. The locking style features a crimped turn that acts as a locking mechanism that grips the bolt or screw to prevent loosening from vibration, eliminating the need for lock wiring, lock-nuts, lockwashers, pellets/patches or other thread locking devices.

Common Materials available include Stainless Steel, Phosphorous Bronze, Inconel X-750 and Nitronic 60 and 90.

Internal Diameters available: American/Inch #2-56   to   1 ½-6” and and Metric M2   to   M24.  Standard inserts lengths measure from 1x to 3x the diameter. Note: larger sizes may be available by special order.

Why use a Key-locking insert vs. a Helical wire insert?

There are three main differences between Key-locking inserts and Helical wire inserts:

1) Strength: Key-locking inserts are stronger than Helical wire inserts

2) Ease of installation: Key-locking inserts are easier to install than Helical wire inserts

3) Price: Key-locking inserts are more expensive than Helical wire inserts!

So here is some direction on how to select the correct threaded insert for your application:  In heavy wear, high vibration and high heat situations where saving space is not a concern and hole depth is limited, Key-locking inserts are the best bet.

When reducing costs and minimizing space are priorities, Helical wire inserts are the way to go. They are particularly useful for creating permanent strong threads in softer materials such as aluminum, titanium and magnesium alloys, and are best suited to lower heat and lower torque environments.

Stay tuned for our next blog, where we discuss, brands and mil-spec options, how to order and installation options!

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

MF Supply is a WBE/WOSB woman owned business, and a trusted supplier of Keenserts & Helical Wire Inserts for manufacturers, government and industry.

We Invite You To Request a Quote, Download a Guide or a Line Card Today!

  • Full ecommerce enabled website with technical manual available 24/7
  • Same day drop ship from factory for thousands of items.
  • Functional Equivalents to expensive brand name fasteners save money and reduce long lead times.
  • Creatively solve problems including hard to find parts and long lead times
  • WBE/WOSB Woman Owned Certified Small Business.

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. 


“Heli-coils” vs. “Keenserts”: 3 differences you must know-Part 1 of 2

Today we will compare 2 popular fastener products that are used to repair damaged threads or strengthen a weaker parent material like aluminum: Helical Wire Inserts and Key-locking Inserts.  Both are commonly used in precision manufacturing and aerospace applications.

What are the main uses of these threaded inserts?

Both “Heli-coil” or Helical wire inserts and “Keensert” or Key-locking inserts fall under the “Threaded Insert” category of fasteners. A threaded insert, also known as a threaded bushing, is a fastener element that is inserted into an object to add a threaded hole. They may be used to repair a stripped threaded hole, provide a durable threaded hole in a soft material, place a thread on a material too thin to accept it, mold or cast threads into a work piece thereby eliminating a machining operation, or simplify changeover from unified to metric threads or vice versa. Although Helical Wire inserts and Key-locking externally threaded inserts are used in similar ways, there are 3 main distinctions that we detail below. But first, let’s take a closer look at each of these fasteners:

What is a Helical Insert Wire Insert? (aka Heli-coil)

Helical wire inserts are precision-formed continuous wire coils that provide permanent, wear-resistant threads which exceed the strength of the parent material. Often underestimated, the popular misconception is that Helical wire inserts are intended solely for thread repair, when, in fact, they have other significant uses.  Not to be confused with other types of threaded inserts or rivnuts, Helical wire inserts resemble springs and are sometimes referred to as “Screw Thread Inserts (STI)” ,“Helicals” or by the popular brand “Heli-Coil” which is a registered trademark of Emhart® Teknologies, Inc.

Three typical applications for using Helical wire inserts are 1) to repair damaged threads in parts that would otherwise have to be scrapped; 2) to strengthen threads against failures due to stripping, seizing or corrosion; 3) to convert threads between inch and metric sizes.

What is a Key-locking insert? (aka Keensert or Keysert)

The Key-locking threaded insert is a solid bushing style insert that is threaded on both the inside and the outside and has wedges or “keys” attached to the top of the insert. These externally threaded inserts are used to distribute loads and repair or strengthen threads against failures due to stripping, seizing or corrosion. Key-locking inserts are commonly used in high torque and high temperature situations, and in applications where fasteners may be repeatedly removed and reassembled. Key-locking inserts are often referred to as Keenserts® and Keyserts, which are registered trademarks for the most popular brand names for this part. (Keensert® is a registered trademark of Huck Patents, Inc. & Keysert® is a registered trademark of Alcoa Fastening Systems).

Typical applications are transmission housings, electronic equipment and suspension units. Key-locking inserts are commonly found in aerospace assemblies.

How do they work?

Helical wire inserts work because the diamond shaped helically formed wire coil screws into a threaded hole to form a mating internal thread for a screw or stud.  

Key-locking inserts are threaded into a pre-tapped hole, and then the keys are hammered into grooves through the threads, permanently locking the insert in place. Their “keys”, which are driven down into the tapped threads, provide a mechanical lock against rotation, especially when the mating stud or bolt will be removed frequently.

What materials, sizes and styles are available?

Keenserts

Key-locking inserts come in four main styles: Miniature, Thin Wall, Heavy Duty Wall (general purpose) and Extra Heavy Duty.

  • Miniature Key-locking inserts are used in electronic and aerospace applications where size and strength are critical. These inserts may be installed in sheet material as thin as 1/16″.
  • Thinwall inserts have smaller external threads than standard heavy-duty inserts and are ideal for tight spaces where less pull-out strength is acceptable.
  • Heavy Duty inserts have a thick, heavy-duty thread wall, suitable for most applications.
  • Extra-heavy duty inserts are used in oversized and overly worn holes.

Key-locking inserts can be internally self-locking or non-locking (the standard is non-locking and is sufficient for the most common applications).

Inserts with the internal self-locking feature are designed to securely lock a bolt when it is entered into the insert only a few turns. Even after repeated installations and removals of the bolt, the lock maintains sufficient locking torque to prevent the bolt from vibrating out.

Common Materials available include Carbon steel, Stainless Steel, Alloy 4140 and A286.

Internal Diameters available: American/Inch #2-56   to   1 ½-6 ” and Metric M2 to M24

Helical wire inserts

Helical wire inserts come in 2 main styles: tanged and tangless (currently, MF Supply spcializes in the tanged style).

The original and widely used tang style has a prong at one end to facilitate installation. The newer tangless style has no prongs to break off, retrieve, or lose. Tangless inserts are commonly used in electronic applications where loose tangs are might cause damage.

Helical wire inserts can be free-running or locking.

Free running is the most common style used for thread repair. The “free” diameter of the insert is larger than the installed diameter and this configuration generates balanced pressure distribution between the coils and threads.

Locking style inserts are recommended for applications that require constant torque, or are subject to stress or vibration. The locking style features a crimped turn that acts as a locking mechanism that grips the bolt or screw to prevent loosening from vibration, eliminating the need for lock wiring, lock-nuts, lockwashers, pellets/patches or other thread locking devices.

Common Materials available include Stainless Steel, Phosphorous Bronze, Inconel X-750 and Nitronic 60 and 90.

Internal Diameters available: American/Inch #2-56   to   1 ½-6” and and Metric M2   to   M24.  Standard inserts lengths measure from 1x to 3x the diameter. Note: larger sizes may be available by special order.

Why use a Key-locking insert vs. a Helical wire insert?

There are three main differences between Key-locking inserts and Helical wire inserts:

1) Strength: Key-locking inserts are stronger than Helical wire inserts

2) Ease of installation: Key-locking inserts are easier to install than Helical wire inserts

3) Price: Key-locking inserts are more expensive than Helical wire inserts!

So here is some direction on how to select the correct threaded insert for your application:  In heavy wear, high vibration and high heat situations where saving space is not a concern and hole depth is limited, Key-locking inserts are the best bet.

When reducing costs and minimizing space are priorities, Helical wire inserts are the way to go. They are particularly useful for creating permanent strong threads in softer materials such as aluminum, titanium and magnesium alloys, and are best suited to lower heat and lower torque environments.

Stay tuned for our next blog, where we discuss, brands and mil-spec options, how to order and installation options.

We Invite You To Request a Quote, Download a Guide or a Line Card Today!

  1. Full ecommerce enabled website with technical manual available 24/7
  2. Same day drop ship from factory for thousands of items.
  3. Functional Equivalentsto expensive brand name fasteners save money and reduce long lead times.
  4. Creatively solve problems including hard to find parts and long lead times
  5. WBE/WOSB Woman Owned Certified Small Business.
Request A Quote

Please forward you comments to robin@mfsupply.com