Helicoil® vs Recoil® vs Keysert®

Which Thread Repair Insert System Is Best?

Damaged or stripped threads are a common problem in manufacturing, automotive repair, maintenance, aerospace, and general machining. When a threaded hole becomes damaged, replacing the entire component is often unnecessary. A properly installed thread repair insert can restore the original thread size and often produce a stronger, more durable thread than the original material.

Three of the most widely used thread repair systems are:

Although these products all repair damaged threads, they are designed for different applications. Selecting the correct system depends on:

This guide explains the differences between these thread repair systems and helps you select the correct solution for your application.

Recoil® Thread Inserts

Recoil inserts are precision-formed stainless steel wire thread inserts designed to restore damaged internal threads. The insert creates a new, strong internal thread while distributing the load over a larger area of the parent material.

Because the load is spread through the insert coils, Recoil inserts are especially effective in softer materials such as aluminum and magnesium, where the original threads may strip easily.

Advantages of Recoil Inserts

  • Restores damaged threads quickly and economically
  • Provides stronger and more wear-resistant threads than many original materials
  • Excellent for aluminum, magnesium, and cast iron applications
  • Manufactured from corrosion-resistant stainless steel
  • Lightweight compared with solid inserts
  • Available in a wide range of thread sizes and standards
  • Easy installation using standard STI taps and installation tools

Common Recoil Applications

  • Engine blocks and cylinder heads
  • Motorcycle engines
  • Aircraft components
  • Machine tools
  • Hydraulic manifolds
  • Aluminum housings
  • Industrial equipment

Available Thread Forms

Recoil inserts are available in many common thread standards including:

  • Metric
  • UNC
  • UNF
  • BSP
  • NPT
  • BA
  • BSW
  • BSF
  • BSC

For most repairs, the installation process involves drilling the damaged hole, tapping the hole with the correct STI tap, installing the insert, and completing the repair by removing the tang.

View Newman Tools Recoil Thread Repair Products

Heli-Coil® Thread Inserts

Heli-Coil® inserts are another widely recognized wire thread insert system used to repair and strengthen threaded holes. Like Recoil®, Heli-Coil inserts are manufactured from precision-formed stainless steel wire and create a new internal thread within the parent material.

Heli-Coil has been used extensively in aerospace, automotive, manufacturing, and industrial applications for many years.

Advantages of Heli-Coil Inserts

  • High-quality stainless steel construction
  • Proven performance in aerospace and industrial applications
  • Restores damaged threads without replacing the component
  • Provides excellent wear resistance for repeated assembly
  • Available in metric and inch thread sizes

Recoil vs Heli-Coil

For many standard industrial applications, Recoil and Heli-Coil wire thread inserts operate on the same basic engineering principle. Both systems use a stainless steel wire coil to create a new internal thread.

Feature Recoil Heli-Coil
Insert Type Wire thread insert Wire thread insert
Material Stainless steel Stainless steel
Installation Method STI tap and installation tool STI tap and installation tool
Typical Applications Industrial, automotive, maintenance Aerospace, automotive, industrial
Performance Comparable for most applications Comparable for most applications

In many cases, the choice between Recoil and Heli-Coil is determined by product availability, customer preference, existing tooling, or specific engineering requirements.

Keysert® Key-Locking Thread Inserts

Keyserts® are solid-body thread repair inserts designed for applications where maximum strength and resistance to vibration are required. Unlike wire thread inserts, Keyserts are mechanically locked into place using keys that are driven into the surrounding material after installation.

This mechanical locking system prevents the insert from rotating or backing out during repeated bolt installation and removal.

Advantages of Keysert Inserts

  • Extremely high pull-out strength
  • Excellent resistance to vibration and shock loads
  • Ideal for repeated assembly and disassembly
  • Cannot unwind when removing fasteners
  • Suitable for heavy-duty industrial applications
  • Available in steel and stainless steel versions

Typical Keysert Applications

  • Aircraft structures
  • Heavy machinery
  • Tooling plates
  • Injection mould equipment
  • Mining equipment
  • Military and defence applications
  • High-performance industrial equipment

View Newman Tools Keysert Key-Locking Inserts

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Which Thread Repair System Should You Choose?

The best thread repair insert depends on the application. The following table provides a general guide.

Application Recommended System
General thread repair Recoil
Aluminum engine repair Recoil
Machine repair and maintenance Recoil
Frequent bolt removal Keysert
Heavy vibration applications Keysert
Maximum pull-out strength Keysert
Aerospace applications Recoil or Keysert depending on specification

Recoil vs Keysert Comparison

Feature Recoil Keysert
Insert Type Stainless steel wire coil Solid threaded insert
Installation Simple and fast Requires additional locking key installation
Cost Lower Higher
Weight Very lightweight Heavier construction
Pull-Out Strength Excellent Outstanding
Vibration Resistance Excellent Outstanding
Repeated Assembly Good Excellent
Installation Speed Fast Moderate
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Frequently Asked Questions About Thread Repair Inserts

Are Recoil® and Heli-Coil® inserts interchangeable?

For many standard thread sizes, Recoil and Heli-Coil wire thread inserts use the same basic installation method and STI thread specifications. Both systems require the correct drill size, STI tap, installation tool, and insert length.

However, customers should always confirm the required specification for critical applications such as aerospace, defence, or OEM production.

Are thread inserts stronger than the original threads?

In many applications, a properly installed stainless steel wire insert can provide a stronger and more durable thread than the original material. This is especially true when repairing softer materials such as aluminum or magnesium.

The insert distributes the load over a larger area, reducing the chance of thread stripping during assembly and service.

When should I use a Keysert instead of a Recoil insert?

A Keysert is recommended when maximum strength, vibration resistance, or repeated removal and installation of fasteners are required.

Typical examples include heavy machinery, tooling fixtures, aircraft components, and applications where a wire insert may not provide enough mechanical locking strength.

What is an STI tap and why is it required?

An STI (Screw Thread Insert) tap creates the special internal thread required for installing a wire thread insert. The installed insert then provides the final standard thread size for the bolt or screw.

Using the correct STI tap is essential for proper insert installation and maximum thread strength.

Can thread inserts repair aluminum threads?

Yes. Thread inserts are commonly used to repair damaged aluminum threads because aluminum is softer than steel and can become damaged from over-tightening or repeated assembly.

Common applications include engine components, transmission housings, pump bodies, and aluminum machine parts.

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Newman Tools Thread Repair Products

Newman Tools has supplied industrial cutting tools and maintenance products to Canadian customers for more than 30 years.

We stock a comprehensive range of thread repair products including:

  • Recoil® wire thread inserts
  • Keysert® key-locking inserts
  • STI taps
  • Thread insert installation tools
  • Thread repair kits
  • Metric and Unified thread sizes
  • British thread forms
  • Pipe thread repair inserts

Whether you are repairing a stripped engine thread, restoring a machine casting, or maintaining industrial equipment, Newman Tools can help you select the correct thread repair solution.

View Recoil Thread Repair Products   View Keysert Thread Repair Products

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Trademark Notice

Heli-Coil®, Recoil®, and Keysert® are registered trademarks of their respective owners. Product names are used on this page for identification and comparison purposes only.

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July 2026

The descriptions, illustrations, specifications, dimensions, and part numbers are subject to change without notice.


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