Best Thread Locking Inserts of 2026

Brian Howie Avatar
Brian Howie
Last Updated: Jan 8, 2026

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Thread locking inserts are small, cylindrical devices designed to securely hold screws and bolts in place. They are typically made of stainless steel or other durable materials and feature internal threads that match the external threads of the fasteners. These inserts are commonly used in applications where vibration or high levels of stress may cause traditional fasteners to loosen over time. By providing a reliable and permanent locking mechanism, thread locking inserts help prevent thread stripping, loosening, and failure, ensuring the longevity and stability of the assembled components.

At a Glance: Our Top Picks

E-Z LOK 12L14 Carbon Steel Threaded Inserts 1/4-20 Cover #TOP 1
E-Z LOK 12L14 Carbon Steel Threaded Inserts 1/4-20
ftb score rating icon 9.8
E-Z LOK C12L14 Carbon Steel Threaded Inserts M10-1.25 Cover #TOP 2
E-Z LOK C12L14 Carbon Steel Threaded Inserts M10-1.25
ftb score rating icon 9.7
E-Z Lok Threaded Insert C12L14 Cover #TOP 3
E-Z Lok Threaded Insert C12L14
ftb score rating icon 9.5

Top 10 Thread Locking Inserts

#TOP 1

E-Z LOK 12L14 Carbon Steel Threaded Inserts 1/4-20

329-4
Pack of 10
E-Z LOK 12L14 Carbon Steel Threaded Inserts 1/4-20 Cover
E-Z LOK Threaded Insert for Metal 12L14 Carbon Steel Thread Inserts 1/4-20 Internal Threads, 7/16-14 External Threads, 0.437 Length Pack of 10

The E-Z LOK Threaded Inserts are designed to give you strong, reliable threads in soft metals like aluminum and cast iron. You don't need any special tools to install these inserts—they work with standard drills and taps, making the process simple and convenient. If you have damaged or worn threads, these inserts can quickly fix and reinforce them, saving you time and effort. Plus, their self-locking design ensures a secure fit, so you can trust that your repairs or installations will hold up well in various applications.

What We Like
Strong and durable threads
No special tools needed
Quick thread repair
Works with soft metals
Self-locking design
#TOP 2

E-Z LOK C12L14 Carbon Steel Threaded Inserts M10-1.25

650-10F
31/64 "
E-Z LOK C12L14 Carbon Steel Threaded Inserts M10-1.25 Cover
E-Z LOK Threaded Insert for Metal C12L14 Carbon Steel Thread Inserts M10-1.25 Internal Threads, 9/16-12 External Threads, 13.08 mm Length Pack of 10

The E-Z LOK Threaded Inserts are solid and reliable inserts designed for metal, providing strong and secure threads that hold well under pressure. You don’t need any special tools to install them; just use your regular drills, taps, and screwdrivers, which makes the process simple and convenient. If you have damaged threads or want to strengthen holes in softer metals like aluminum or cast iron, these inserts are a quick and effective solution. They are especially useful for reinforcing or repairing threads, saving you time and effort when working with soft metal materials.

What We Like
Strong, self-locking inserts
No special tools required
Quick thread repair
Ideal for soft metals
#TOP 3

E-Z Lok Threaded Insert C12L14

329-5
27/64"
E-Z Lok Threaded Insert C12L14 Cover
E-Z LOK Threaded Insert for Metal 12L14 Carbon Steel Thread Inserts 5/16-18 Internal Threads, 1/2-13 External Threads, 0.484 Length Pack of 10

The E-Z Lok Threaded Insert offers an effortless way to repair damaged threads in metal. You can easily install it using a standard drill and tap, eliminating the need for special tools. This insert features a self-locking mechanism with a pre-applied adhesive that activates upon installation, allowing you to be fastener-ready in just 3-5 minutes. It's particularly effective for soft metals like aluminum, cast iron, or magnesium, making it a versatile solution for various projects. With its strong American-made construction, you can trust that this insert will provide reliable performance.

What We Like
Easy installation
Fast adhesive activation
Versatile for soft metals
Strong American construction
#TOP 4

E-Z LOK 329-6 Threaded Insert

329-6
31/64"
E-Z LOK 329-6 Threaded Insert Cover
E-Z LOK Threaded Insert for Metal 12L14 Carbon Steel Thread Inserts 3/8-16 Internal Threads, 9/16-12 External Threads, 0.515 Length, Pack of 10

E-Z LOK Threaded Insert is a solid and self-locking insert designed for metal applications. Made of 12L14 carbon steel, it provides optimal holding power in soft metals such as aluminum, cast iron, and magnesium. The inserts are easy to install with standard tools, requiring no special drills or taps. They can quickly repair damaged threads or reinforce tapped holes, making them a convenient solution for any metalworking project. With E-Z LOK Threaded Insert, you can easily create strong threads by drilling the hole, tapping it, and turning in the insert using a screwdriver, bolt/jam nut, or an E-Z LOK drive tool. Experience the convenience and reliability of E-Z LOK Threaded Insert in your metalworking projects.

What We Like
Strong and self-locking
Easy to install with standard tools
Quickly repairs damaged threads
#TOP 5

E-Z LOK 453-8 Stainless Steel Threaded Inserts

453-8
stainless steel
E-Z LOK 453-8 Stainless Steel Threaded Inserts Cover
E-Z LOK - 453-8 E-Z Lok Externally Threaded Insert, 303 Stainless Steel, M8-1.25 Internal Threads, M12x1.75 External Threads, 12.50mm Length, Made in US (Pack of 5)

The E-Z LOK Threaded Inserts are designed to provide strong and reliable thread reinforcement for metal parts. Made from durable 303 stainless steel, these inserts are easy to install using common tools, so you don’t need any special equipment. They are perfect for quickly fixing damaged threads or strengthening holes in softer metals like aluminum and cast iron, saving you time and effort. With a simple drilling and tapping process, you can easily insert them using a screwdriver or bolt, ensuring a secure and lasting hold for your projects.

What We Like
Strong metal inserts
Easy installation
Repairs damaged threads
Works with soft metals
#TOP 6

E-Z LOK 303 Stainless Steel Threaded Inserts #6-32 / 1/4"-20

303-006
E-Z LOK 303 Stainless Steel Threaded Inserts #6-32 / 1/4"-20 Cover
E-Z Lok Externally Threaded Insert, 303 Stainless Steel, #6-32 Internal Threads, 1/4"-20 External Threads, 0.280" Length, Made in US (Pack of 5)

The E-Z LOK Threaded Inserts are designed to provide strong, reliable threads in metal materials. If you need to fix damaged threads or strengthen soft metals like aluminum or magnesium, these inserts offer a quick and effective solution. Made from solid 303 stainless steel, they are durable and easy to install using common tools—no special equipment required. You simply drill and tap the hole with standard tools, then screw in the insert using a screwdriver or bolt. This makes it simple for you to reinforce or repair threaded holes without hassle, ensuring long-lasting holding power in your metal projects.

What We Like
Strong metal threads
Easy installation
Repairs damaged threads
Works with soft metals
#TOP 7

E-Z LOK Externally Threaded Insert

329-8
1/2"-13
E-Z LOK Externally Threaded Insert Cover
E-Z LOK Threaded Insert for Metal 12L14 Carbon Steel Thread Inserts 1/2-13 Internal Threads, 3/4-10 External Threads, 0.656 Length, Pack of 5

E-Z LOK Externally Threaded Insert is a strong and easy-to-install threaded insert designed for use with soft metals such as aluminum, cast iron, and magnesium. This pack of 5 inserts is made of 12L14 Carbon Steel and meets AISI 12L14 standards. With these inserts, you can quickly repair damaged threads or reinforce tapped holes in soft metals. The inserts are self-locking, providing optimal holding power. Installation is a breeze as you can use standard tools, with no need for special drills or taps. Simply drill the hole, tap it, and turn in the insert with a screwdriver, bolt/jam nut, or an E-Z LOK drive tool. The E-Z LOK Externally Threaded Insert is a reliable and convenient solution for your metal threading needs.

What We Like
Strong and self-locking
Easy to install with standard tools
Quickly repairs damaged threads
#TOP 8

E-Z LOK 453-6 Stainless Steel Threaded Insert M6-M10

453-6
Silver
E-Z LOK 453-6 Stainless Steel Threaded Insert M6-M10 Cover
E-Z LOK - 453-6 E-Z Lok Externally Threaded Insert, 303 Stainless Steel, M6-1.0 Internal Threads, M10x1.5 External Threads, 10.49mm Length, Made in US (Pack of 5)

The E-Z LOK Threaded Insert is a solid stainless steel solution designed to give you strong, reliable threads in metal. If you work with soft metals like aluminum or cast iron, these inserts help you create durable, long-lasting threads. You don’t need any special tools to install them—just standard drills and taps. This makes it easy and convenient to use, even if you’re not a professional. Plus, if you have damaged threads, these inserts let you quickly repair and reinforce them, saving time and effort on your projects.

What We Like
Strong metal inserts
Easy installation
Repairs damaged threads
Works with soft metals
No special tools needed
#TOP 9

MOLLIFII Thin Wall Thread Insert

319-820-A
Brown
1/2"-20, 5/8 inches
MOLLIFII Thin Wall Thread Insert Cover
Thin Wall Self Locking Thread Insert, 1/2"-20 Int Thrd Sz, Carbon Steel, 5 PK

The MOLLIFII Thread Insert is designed with a thin wall and made from durable carbon steel, making it an excellent choice for securing internal threads of size 1/2"-20. This self-locking feature ensures that once installed, the insert stays in place, providing you with peace of mind in various applications. Its thin wall design allows for easy installation in tight spaces, giving you flexibility in your projects. With a pack of five, you can conveniently stock up for multiple uses, ensuring you always have the right insert on hand when you need it most.

What We Like
Durable carbon steel material
Self-locking design
Thin wall for easy installation
Pack of five for convenience
#TOP 10

E-Z LOK Externally Threaded Insert, C12L14 Carbon Steel

319-428
Pack of 10
E-Z LOK Externally Threaded Insert, C12L14 Carbon Steel Cover
E-Z LOK - 319-428 E-Z Lok Externally Threaded Insert, C12L14 Carbon Steel, Meets AISI 12L14, 1/4"-28 Internal Threads, 3/8"-16 External Threads, 0.375" Length, Made in US (Pack of 10)

E-Z LOK Threaded Insert is a strong, easy-to-install, and self-locking threaded insert made of C12L14 carbon steel. It is designed for use with soft metals such as aluminum, cast iron, and magnesium. With E-Z LOK Threaded Insert, you can quickly repair damaged threads or reinforce tapped holes in soft metals. Installation is a breeze as it requires no special drills, taps, or installation tools. Simply drill the hole with a standard drill, tap the hole with a standard tap, and turn in the insert with a screwdriver, bolt/jam nut, or an E-Z LOK drive tool. The threaded inserts provide optimal holding power in metal and ensure strong threads that are built to last. Upgrade your metal projects with the convenience and reliability of E-Z LOK Threaded Insert.

What We Like
Strong and self-locking
Easy and quick installation
Repairs damaged threads in soft metals
Buying Guide Image

Frequently Asked Questions (FAQs)

1. What is the difference between helicoil and threaded insert?

Heli-Coil inserts and threaded inserts differ in their construction and performance. Heli-Coil inserts are wound wire inserts, which have less pull-out and torque-out strength compared to solid metal threaded inserts like Helisolid®. Heli-Coil may be prone to cross-threading, while accidental cross-threading is unlikely with Helisolid®.

2. What are the two types of threading inserts?

There are two types of threading inserts: full profile and partial profile. Full profile inserts produce specific thread types, such as round (Rd) according to DIN 405 and British Standard Whitworth (BSW). These inserts are designed to provide accurate threading for various applications.

3. How long does thread lock last?

Thread lockers like Loctite have a shelf life of 24 months when unopened or 12 months once the tube is opened. Proper storage conditions between 46-82 degrees F are recommended to ensure the effectiveness of the thread lock. It is important to note that Loctite should not be frozen.

4. What are the different types of locking inserts?

Locking inserts are available in two primary types: free-running wire inserts and screw locking wire inserts. Both types offer two installation styles: tanged and tangless. These variations come in various materials and platings to suit different application requirements.

5. Do threaded inserts need to be glued?

The need to glue threaded inserts depends on the specific application. In most cases, gluing is unnecessary. However, for heavily used inserts, gluing may be beneficial to provide additional stability and strength.

6. Are Heli-Coil stronger than original threads?

When properly installed, helical inserts like Heli-Coil create a permanent bond that is stronger than the original bolt fastening. The wider coils of the insert expand and create a tight seal against the threads, resulting in a strong and durable threaded assembly.

7. What is the strongest thread insert?

Helically coiled wire thread inserts are considered to be the strongest and most durable threaded assembly known to engineers. These inserts provide exceptional strength and reliability in threaded connections.

8. What are the three categories of threaded inserts?

Threaded inserts are available in various categories. The three common categories include captive inserts, externally threaded inserts, and press-fit inserts. Additionally, helical inserts are also widely used. Each category serves different purposes and can be chosen based on specific application requirements.

Editor's Notes

During our thread locking insert research, we found 24 thread locking insert products and shortlisted 10 quality products. We collected and analyzed 4,894 customer reviews through our big data system to write the thread locking inserts list. We found that most customers choose thread locking inserts with an average price of $16.17.

The thread locking inserts are available for purchase. We have researched hundreds of brands and picked the top brands of thread locking inserts, including E-Z LOK, MOLLIFII. The seller of top 1 product has received honest feedback from 51 consumers with an average rating of 4.8.

Written by
Brian Howie Avatar

Brian Howie is a content writer and senior industrial designer. After graduation from Westminster College, he has been engaged in product design and manufacturing for 18 years. Brian Howie has always found great pleasure in designing industrial products and sharing his ideas and experience online.