Sewing & Knitting

The Best Thread Locking Inserts

This post contains affiliate links. As an Amazon Associate we earn from qualifying purchases.

Our picks are based on Amazon bestseller rankings, verified customer ratings, and product availability. We update our recommendations regularly to ensure accuracy.

Thread locking inserts are essential for reinforcing damaged or worn threads in various materials, from metal to plastic. Choosing the right type ensures a secure and durable repair, preventing further damage and extending the life of your components. This guide will help you select the ideal insert for your needs.

No. 1
E-Z LOK - 453-8 E-Z Lok Externally Threaded Insert, 303 Stainless Steel, M8-1.25 Internal Threads, M12x...
  • THREADED INSERTS FOR METAL – E-Z LOK Thread Inserts for metal. Solid threaded inserts that are strong, easy to install, and self-locking. For optimal holding power in metal.
  • INSTALL WITH STANDARD TOOLS – 303 stainless steel threaded inserts machined out of solid steel for strength. Install with standard tools. No special drills, taps, or special installation tools are needed.
  • QUICKLY REPAIR DAMAGED THREADS – Quickly repair damaged threads or reinforce tapped holes in soft metals with these steel thread inserts.
  • FOR USE WITH APPLICATIONS – The threaded inserts are designed for use with soft metals: aluminum, cast iron, magnesium, etc.
  • STRONG THREADS MADE EASY – Simply drill the hole with a standard drill. Tap the hole with a standard tap. Turn in the insert with a screwdriver, bolt/jam nut, or an E-Z LOK drive tool.
No. 2
E-Z Lok Externally Threaded Insert, 303 Stainless Steel, 3/8"-16 Internal Threads, 9/16"-12 External Threads...
  • Easy to Use Solution For Repairing Damaged Threads in Metal
  • Install With Standard Drill & Tap; NO Special Tools Needed
  • Self Locking; Preapplied Adhesive Activates Upon Installation and is Fastener-Ready in 3-5 Minutes
  • Ideal For Soft Metals Like Aluminum, Cast Iron, or Magnesium
  • Made in America - Strong, Solid Construction Design
No. 3
E-Z LOK Threaded Insert for Metal 12L14 Carbon Steel Thread Inserts 1/4-20 Internal Threads, 7/16-14 External...
  • THREADED INSERTS FOR METAL – E-Z LOK Thread Inserts for metal. Solid threaded inserts that are strong, easy to install, and self-locking. For optimal holding power in metal.
  • INSTALL WITH STANDARD TOOLS – 12L14 Carbon steel threaded inserts. Install with standard tools. No special drills, taps, or special installation tools are needed.
  • QUICKLY REPAIR DAMAGED THREADS – Quickly repair damaged threads or reinforce tapped holes in soft metals with these steel thread inserts.
  • FOR USE WITH APPLICATIONS – The threaded inserts are designed for use with soft metals: aluminum, cast iron, magnesium, etc.
  • STRONG THREADS MADE EASY – Simply drill the hole with a standard drill. Tap the hole with a standard tap. Turn in the insert with a screwdriver, bolt/jam nut, or an E-Z LOK drive tool.
No. 4
E-Z LOK Threaded Insert for Metal 12L14 Carbon Steel Thread Inserts 5/16-18 Internal Threads, 1/2-13 External...
  • THREADED INSERTS FOR METAL – E-Z LOK Thread Inserts for metal. Solid threaded inserts that are strong, easy to install, and self-locking. For optimal holding power in metal.
  • INSTALL WITH STANDARD TOOLS – 12L14 Carbon steel threaded inserts. Install with standard tools. No special drills, taps, or special installation tools are needed.
  • QUICKLY REPAIR DAMAGED THREADS – Quickly repair damaged threads or reinforce tapped holes in soft metals with these steel thread inserts.
  • FOR USE WITH APPLICATIONS – The threaded inserts are designed for use with soft metals: aluminum, cast iron, magnesium, etc.
  • STRONG THREADS MADE EASY – Simply drill the hole with a standard drill. Tap the hole with a standard tap. Turn in the insert with a screwdriver, bolt/jam nut, or an E-Z LOK drive tool.
No. 5
XunLiu Key Locking Inserts Thread Repair (Int.M12X1.25 Ext.M18X1.5Lg18)
  • PROFESSIONAL THREAD REPAIR — Designed to restore damaged or stripped internal threads to full original strength. Eliminates costly part replacement and rework, saving time and material costs in industrial and manufacturing environments.
  • 4-KEY LOCKING MECHANISM FOR VIBRATION RESISTANCE — Four external locking keys are permanently pressed into the parent material, providing a 360° mechanical lock that prevents rotation, loosening, or pull-out even under high torque and heavy vibration...
  • PREMIUM 303 STAINLESS STEEL CONSTRUCTION — Manufactured from corrosion-resistant 303 stainless steel, offering excellent performance in harsh environments including moisture, chemicals, and elevated temperatures. Built for long-lasting reliability.
  • REINFORCES LOW-STRENGTH BASE MATERIALS — Ideal for aluminum alloy, cast iron, engineering plastics, and other soft or brittle materials. Dramatically increases the load-bearing capacity of threaded holes, extending service life of assemblies.
  • REMOVABLE WITHOUT DAMAGING PARENT MATERIAL — The key insert can be removed and replaced without compromising the base material, making it perfect for repair, maintenance, and prototype applications where flexibility is essential.
No. 6
AUNMAS 10-24UNC Helical Inserts Kit, Stainless Steel Thread Repair Inserts for Aluminum Metal with ST Tap and...
  • Enhanced Durability: These stainless steel coiled inserts are for applications requiring frequent screw removal, significantly extending the service life and reducing wear on screw threads
  • Improved Connection Strength: Suitable for use in low-strength materials like aluminum, these thread inserts help prevent thread damage and improve the overall connection performance and strength
  • Load Distribution and Vibration Absorption: With built-in elasticity, these inserts distribute the load evenly across threads, eliminating pitch and tooth deviations and absorbing vibrations to increase connection strength and fatigue resistance
  • Prevents Loosening: Designed to keep screws securely in place, they are especially useful for products requiring a high safety coefficient to prevent loosening
  • Simple Maintenance and Installation: Easily restore a damaged screw hole to working condition by installing a thread insert, thus preventing workpiece loss and simplifying maintenance
  • Complete Kit Included: This 10-24UNC helical inserts kit comes with stainless steel thread repair inserts, ST tap, and installation tool for comprehensive thread repair solutions
No. 7
E-Z LOK-C108 Threaded Inserts For Metal; Assortment Kit; Carbon Steel; Heavy Wall; UNC Internal Threads...
  • Price For: Each Item: Thread Repair Kit Application: For Installation in Metal Type: Heavy Wall Size: 10 Ea. #10-24, 1/4-20, 5/16-18, 3/8-16, 6 Ea. 1/2-13 Internal Thread Sizes Includes: (10) Each: 10-24, 1/4-20, 5/16-18, 3/8-16, (6) Each: 1/2-13, Molded...
No. 8
E-Z LOK Threaded Insert for Metal Thin Wall 303 Stainless Steel Thread Inserts 5/16-18 x 7/16-20 Pack of 5
  • THREADED INSERTS FOR METAL – E-Z LOK Thin Wall Thread Inserts for metal. Solid threaded inserts that are strong, easy to install, and self-locking. For optimal holding power in metal.
  • INSTALL WITH STANDARD TOOLS – 303 stainless steel threaded inserts machined out of solid steel for strength. Install with standard tools. No special drills, taps, or special installation tools are needed.
  • QUICKLY REPAIR DAMAGED THREADS – Quickly repair damaged threads or reinforce tapped holes in soft metals with these steel thread inserts. The Thin Wall feature reduces the hole size.
  • FOR USE WITH APPLICATIONS – The threaded inserts are designed for use with soft metals: aluminum, cast iron, magnesium, etc.
  • STRONG THREADS MADE EASY – Simply drill the hole with a standard drill. Tap the hole with a standard tap. Turn in the insert with a screwdriver, bolt/jam nut, or an E-Z LOK drive tool.
No. 9
E-Z LOK Threaded Insert for Metal 12L14 Carbon Steel Thread Inserts 3/8-16 Internal Threads, 5/8-11 External...
  • THREADED INSERTS FOR METAL – E-Z LOK Thread Inserts for metal. Solid threaded inserts that are strong, easy to install, and self-locking. For optimal holding power in metal.
  • INSTALL WITH STANDARD TOOLS – 12L14 Carbon steel threaded inserts. Install with standard tools. No special drills, taps, or special installation tools are needed.
  • QUICKLY REPAIR DAMAGED THREADS – Quickly repair damaged threads or reinforce tapped holes in soft metals with these steel thread inserts.
  • FOR USE WITH APPLICATIONS – The threaded inserts are designed for use with soft metals: aluminum, cast iron, magnesium, etc.
  • STRONG THREADS MADE EASY – Simply drill the hole with a standard drill. Tap the hole with a standard tap. Turn in the insert with a screwdriver, bolt/jam nut, or an E-Z LOK drive tool.

Last update on 2026-07-17 / Affiliate links / Images from Amazon Product Advertising API

How to Choose the Best Thread Locking Inserts

Understanding Thread Locking Inserts

Thread locking inserts, often called Helicoil or thread repair kits, are precision-engineered coils that create stronger, more durable threads within a pre-drilled hole. They are commonly used to repair stripped screw holes or to strengthen threads in softer materials. When selecting an insert, consider the material you are working with, the size of the original thread, and the desired strength of the repair.

Types of Thread Locking Inserts

There are several primary types of thread locking inserts:
  • Coiled Inserts: These are the most common, made from a diamond-shaped wire that forms a spring-like coil. They offer excellent resistance to vibration and wear.
  • Solid Bushings: These are one-piece inserts, often made of metal, that are tapped into a pre-drilled hole. They provide a very strong and permanent repair.
  • Self-Tapping Inserts: Designed for direct installation into plastic or wood without pre-tapping, these inserts cut their own threads as they are screwed in.

Material and Size Considerations

The material of the insert is crucial for compatibility and strength. Stainless steel is a popular choice for its corrosion resistance and durability, suitable for metal applications. For plastics and softer materials, inserts made from hardened steel or specialized alloys might be necessary. Always ensure the insert's internal thread size matches the bolt or screw you intend to use, and the external thread size is appropriate for the hole you are repairing. Kits often include the necessary drill bit, tap, and installation tool for a complete repair.

Installation Process

Proper installation is key to a successful thread repair. This typically involves drilling out the damaged threads with a specific size drill bit, tapping the hole with a dedicated tap to create new threads for the insert, and then screwing the insert into place using the provided tool. For coiled inserts, a tang (a small piece at the end) is often broken off after installation to ensure a flush finish.

Frequently Asked Questions

What is a thread locking insert used for?
Thread locking inserts are used to repair stripped or worn-out screw threads in various materials. They can also be used to strengthen threads in softer materials, creating a more robust connection.
What materials can thread locking inserts be used in?
These inserts are versatile and can be used in a wide range of materials, including metals (aluminum, steel), plastics, wood, and composites. The specific type of insert will determine its suitability for each material.
Are all thread locking inserts the same size?
No, thread locking inserts come in various sizes to match different bolt and screw thread dimensions. It is essential to select an insert kit that corresponds to the original thread size you are repairing or creating.
Do I need special tools to install thread locking inserts?
Yes, most thread locking insert kits include specialized tools for installation. These typically include a drill bit for preparing the hole, a tap to cut the internal threads, and an installation tool to wind the insert into place.
How do I choose the right type of insert?
Consider the material you are working with, the size of the thread you need to repair or create, and the required strength of the final connection. Coiled inserts are common for general repairs, while self-tapping options are good for plastics.