Screw locking

HELICOIL® locknuts

Efficient and reliable. With HELICOIL® special nuts for secured screw joints.


Fastening in high-temperature applications

HELICOIL® nuts with integrated HELICOIL® Screwlock ensure secure screw joints.

An efficient linking of two fasteners. The nuts comprise a nut body and an integrated HELICOIL® Screwlock thread insert.

This product is made by Böllhoff

Method / principle

Locking is achieved by one or more polygonal threads of the HELICOIL® Screwlock. They exert a clamping effect on the flanks of the inserted screw, creating an elastically resilient frictional locking. The resulting clamping torques are comparable with those specified in ISO 2320 or can be adjusted individually.


HELICOIL® locknuts are used in engine exhaust systems in the automotive industry, in mechanical engineering, in construction machinery, rail vehicles and agricultural machinery.

  • Equal clamping torque with repeated usage
  • Uniform load and stress distribution
  • High thermal stability
  • Constant thread friction
  • Reduced residual dirt

Product benefits

There are many good reasons for using our products.

Strength and options.
Point by point.

Clamping effect directly in the thread – elastically resilient

Prevents self-loosening. The threads of the HELICOIL® Screwlock clamp the flanks of the screw or bolt to be inserted – for an elastically resilient frictional locking and optimal screw locking.

Modular design.

High-strength nuts in combination with HELICOIL® Screwlock thread inserts – optionally with washer. No loosening on loss of preload force due to the use of seals. For greater security.


The locknut retains its strength even at high working temperatures, e.g. in exhaust systems. Seizing is also prevented.

Detailed description


The function of the HELICOIL® locknut

The locknut consists of a nut body and the HELICOIL® Screwlock thread insert. Screw locking is achieved by a polygonal thread of the HELICOIL® Screwlock. These threads clamp the flanks of the screw or bolt to be inserted. The result is an elastically resilient frictional locking and hence screw locking to prevent self-loosening. Depending on the application, multiple polygonal threads can be used to achieve increased clamping torques.

HELICOIL® locknut

HELICOIL® locknut

Base and washer + HELICOIL® Screwlock = HELICOIL® locknut
collar nut version with washer

Base and washer + HELICOIL® Screwlock = HELICOIL® locknut collar nut version with washer

Product variants

Every project deserves a tailor-made solution.

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

Hexagon nut


Flange nut


Cap nut


Weld nut


Exhaust manifold nut


Nut with integrated washer


Square nut



Find out more: related downloads.

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

Title Language Version File Download
HELICOIL® locknuts
Special nuts with screw lock
English 0560/15.02 687 kB / PDF
English 0560/15.02 687 kb / PDF

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