Thread reinforcement


Load capacity and precision at the highest stage. With HELICOIL® thread technology for high-strength screw joints.

Thread reinforcement

The new HELICOIL® Smart

Strength and precision at their best.

The new HELICOIL® Smart with tang which does not have to be broken off.


For high-strength fastenings

HELICOIL® thread inserts create load-bearing joints in metal materials with low shear strength.

HELICOIL® thread inserts have been proven in practice. For over 65 years. They are available in Free Running and Screwlock versions. The green or red color simplifies identification even when installed.

This product is made by Böllhoff

Method / principle

HELICOIL® is thread reinforcement and repair.
Threads are reinforced whenever low-strength materials (e.g. aluminium, aluminium-magnesium alloys and fibrereinforced plastics) are used.
HELICOIL® thread inserts produce high-strength, wear- and heat-resistant threads of highest precision.
The nut thread is wear resistant even in cases of frequent use.


The HELICOIL® is used in mechanical engineering and in the electronics, automotive and aerospace industries. HELICOIL® is also applied in gear housings, exhaust systems, engines and satellites, thread reinforcement, repeated installations, maintenance and repair as well as in lights, electrical appliances, hammer drills and printing presses.

HELICOIL® Plus thread inserts comply with a variety of requirements and industry standards, including those in the aerospace industry, and feature other approvals as well as suitability tests, e.g. in the field of power plant technology.

Product benefits
  • High-strength
  • Strong
  • Corrosion and temperature-resistant
  • Easy to identify even after insertion (due to color)
  • Different versions for every requirement
  • Various technical surface finishes available
  • Assembly systems, tools and products from a single source
  • Available with imperial and metric dimensions and in special versions

Product benefits

There are many good reasons for using our products.

Strength and options.
Point by point.

Corrosion and temperature-resistant

True quality appears under extreme conditions. Even when exposed to high temperatures and humidity, HELICOIL® thread inserts remain stable and reliable. Depending on the application, the thread inserts are made of different materials.


Long-lasting. The high surface quality of the rolled thread made of austenitic chrome-nickel steel ensures a high-strength, wear-resistant thread with a constant, extremely low thread friction torque.

Uniform load and stress distribution

Uniform along the entire length of the screw. The elastic properties of the HELICOIL® thread insert allow uniform load and stress distribution.

Screw locking

No self-loosening. The thread technology and polygonal twist of the HELICOIL® Screwlock result in a high degree of frictional connection and therefore in a screw lock. Additional locking of the joint using split pins, wires or washers is not necessary.

Reduced thread friction

Less friction, more precision. For a torque-controlled screw tightening application, the screw pre-load force can be adjusted more precisely and the yield point of the screw utilized more efficiently.


Perfect for lightweight construction. HELICOIL® combines minimum space requirements and high strength. Thus, high-strength screws are also perfect for use in materials with low shear strength.

Detailed description



A coil thread insert with tang which does not have to be broken off. Installed quickly and securely – The innovation: The installation mandrel bends it backward during spinning off and then compresses it. This smart thread insert merges the advantages of the HELICOIL® Plus and the HELICOIL® Tangfree.

The HELICOIL® Smart thread insert, which is made from a wire with rhombic profile, is also formed into an elastic spiral. As to the Free Running version, thread by thread it is a completely free running coarse thread. The result is a truetogauge internal thread including the last thread which is in every case threadable.
To screw in the thread insert, all you need is the Smart installation mandrel of similar size as a tap. Very special is the blade position control. Upon screwingin, the blade has a pullin function, whereas upon screwingout, it turns into a bending and compression tool.

HELICOIL® Smart with installation mandrel – The thread insert with tang which does not have to be broken off

HELICOIL® Plus – The advantage

Wire with rhombic profile is formed into elastic spirals – the “Plus” refers to the special thread start compared to the HELICOIL® Classic. Simply place it and screw it in like a screw using an installation mandrel with similar dimensions to those of a tap. Existing tools from the previous model can still be used. Due to the considerably expanded range of tools to be used, installation times are reduced by up to 20 % compared to previous methods.

HELICOIL® Plus thread inserts

HELICOIL® Tangfree – The innovative thread insert with no tang

Installed quickly and securely – and no tang to break. The innovative coil of the insert allows installation from both ends with identical quality. Thanks to the reduced thread on both ends and the coil ends optimized for insertion, the HELICOIL® Tangfree thread insert can be installed without special alignment. The HELICOIL® Tangfree is easily screwed onto the mandrel and goes into the pilot thread smoothly. The spring-mounted installation blade grips into the notch of the coil thread insert and securely installs it in the prepared pilot thread.
In addition, the optimized geometry minimizes wear on the tools. The tool concept is impressive, boasting long service life for the blades and simple maintenance.

HELICOIL® Tangfree thread insert and installation mandrel

Product variants

Every project deserves a tailor-made solution.

Learn more about the product types and find the right variant for your particular application.

Free Running

The new thread insert merges the advantages of the HELICOIL® Plus and the HELICOIL® Tangfree. There is a tang, but it does not have to be broken off and removed. The installation time is therefore reduced by approx. 20 %.


Free Running

The thread insert with its precision-formed rhombic profile runs through freely turn for turn. The result is an internal thread that is true to gauge and accepts the insertion of a screw at both ends.



This thread insert also has an additional screw-locking section. One or more polygonal threads clamp the flanks of the installed screw.


HELICOIL® Tangfree
Free Running

The innovative thread insert without a tang. You do not need a tang to install these thread inserts. Therefore, tang break and removal are not required. Combined with the matching installation tools, the current innovation status in the HELICOIL ® technology is a perfect addition to the HELICOIL® product family.


HELICOIL® Tangfree

HELICOIL® Tangfree Screwlock has the same advantages as HELICOIL® Tangfree. In addition, there is a screw-locking area.


Free Running

Every thread of the thread insert with precision-formed, rhombic profile is free running.



This thread insert offers an additional screw-locking section as well.


HELICOIL® Plus Twinsert

The HELICOIL® Plus Twinsert consists of two HELICOIL® Plus thread inserts and is used for extensively stripped tapped holes.


HELICOIL® with Primer‑Free® 2

PrimerFree® 2 protects your magnesium or aluminium components against galvanic corrosion. The resin-bonded, Teflon® impregnated fluoropolymer coating ensures an even, electrically insulating coating and thus overall protection against galvanic cell formation.

Simply install stainless steel HELICOIL® thread inserts with PrimerFree® 2 coated surface into holding materials such as aluminium and magnesium. PrimerFree® 2 replaces therefore previous zinc-chromate primers, which had to be assembled in the holding thread before the HELICOIL® installation.



Find out more: related downloads.

If you would like to know more, simply download the relevant brochures.

Title Language Version File Download
Metric thread inserts for metals
English 0100/16.02 2941 kB / PDF
English 0100/16.02 2941 kb / PDF
Imperial thread inserts for metals
English 0101/15.02 3494 kB / PDF
English 0101/15.02 3494 kb / PDF
The new generation of thread technology for high-strength joints
English 10/2019 2870 kB / PDF
English 10/2019 2870 kb / PDF
HELICOIL® Tangfree
The tangfree coil thread insert for high-strength threads
English 03/2019 2618 kB / PDF
English 03/2019 2618 kb / PDF
HELICOIL® with Primer‑Free® 2
The well-established thread technology with new surface coating
English 03/2020 178 kB / PDF
English 03/2020 178 kb / PDF
Repair solutions for damaged threads
English 02/18 994 kB / PDF
English 02/18 994 kb / PDF
Thread reinforcement in automotive engineering
English 10/2021 4285 kB / PDF
English 10/2021 4285 kb / PDF

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