Armstrong ArmaCoil inserts allow you to protect and strengthen all tapped threads. Armstrong 
ArmaCoil inserts 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. 


ArmaCoil 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. 


ArmaCoil Locking Inserts 

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. 


ArmaCoil Insert Materials

Armstrong ArmaCoil inserts are manufactured from 18-8 stainless steel, which is the standard 
material. Other materials available include: 

•Nitronic
•Nimonic 90
•Inconel X750
•Zeron 100
•Phosphor Bronze


ArmaCoil Insert Platings

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:

•Cadmium Plating
•Silver Plating
•Zinc Plating
•Dry Film Lubricated

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 ArmaCoil 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 Phosphor Bronze Inserts 

ArmaCoil Nimonic 90 Inserts

ArmaCoil Screw Thread Inserts