Armstrong ArmaCoil inserts allow you to protect and strengthen all tapped threads. They are mirror-smooth, reinforced internal threads of 18-8 stainless steel, or of other materials, with a hardness far in excess of the usual tapped materials.

The outstanding engineering features of ArmaCoil inserts, long recognised by the leading aircraft, industrial and military equipment manufacturers, have ensured their widespread use in these fields.

Free Running Inserts Armstrong ArmaCoil free running inserts are manufactured from high tensile stainless steel wire, formed into a diamond section, to exacting dimensional standards. When installed, the ArmaCoil insert provides a precision female thread of high surface finish and strength.

In addition to all the characteristics of free running inserts, the Armstrong ArmaCoil Locking insert has one or more of its intermediate coils deformed polygonally. This creates strong resilient pressure onto the thread flanks of the bolt as it passes through the ArmaCoil Locking insert. This in-built prevailing torque of the grip coil positively locks the inserted bolt, preventing it from loosening under vibrations or impact. Screws can be inserted by hand up to the grip coil, after which some mechanical means must be employed to overcome the locking medium.

ArmaCoil Locking inserts are coloured red for identification purposes only, to distinguish them from free running inserts.

Armstrong ArmaCoil inserts are manufactured in a wide range of materials and platings to suit different usage needs, such as high temperature applications, corrosion & stress cracking resistance, salt water applications, electrical conductivity, and non-magnetism.

Where corrosion or galling resistance is required, or additional lubrication is needed in high friction applications, surface treatments can be added to standard stainless steel ArmaCoil inserts.

Some of these treatments include:

In latest developments, new treatments such as Cadmium Plate & Olive Drab and ArmaGuard (which prevents galvanic corrosion between insert and parent material) have been created to cater to market demand.

Five lengths of Armstrong ArmaCoil inserts for each thread size are available - lengths of 1, 1.5, 2, 2.5 & 3 times the thread diameter of the bolt. These different insert lengths offers the designer the opportunity to balance the tensile strength of the bolt material against the shear strength of the parent material.

ArmaCoil Screw Thread Inserts are available in:

ArmaCoil TwinCoils are used to salvage wire thread insert holes that have become worn or stripped, as well as in the correction of out-of-position holes and tapped holes that are gauged to be oversized. The ArmaCoil TwinCoil system consists of two ArmaCoil inserts. An Outer TwinCoil is installed into an oversize tapped hole, which has an Inner TwinCoil fitted inside to give a standard female thread. The Outer TwinCoil is installed into the TwinCoil tapped hole (larger than a conventional wire thread insert tapped hole) and is the same nominal length as the original thread. The Outer TwinCoil is always a free running insert while the Inner TwinCoil can be either free running or screw lock, depending on the application. As the Inner TwinCoil must be supported by the Outer TwinCoil, its length is ONE COIL shorter than the Outer TwinCoil. This allows the Inner TwinCoil to be installed below the end of the Outer TwinCoil at each end. Thread lengths less than 1.5 times the nominal diameter are usually not available. This is due to reduced thread engagement affecting the assembled strength to a potentially un-acceptable level.