To view more KATO tech articles please visit KATOpedia

KATO Insert Materials

KATO Tangless Inserts are used extensively in aircraft applications, such as engines, gear boxes , fuel systems, radar, avionics, flight controls, lighting and HVAC systems. They are also used widely by the military and in many other electronic and mechanical commercial applications. The KATO tangless, FOD-free design is the preferred standard for optimum thread assemblies in new fastening system designs.

Emerging technologies have created new insert requirements, triggering the development of innovative insert materials to meet those exacting needs such as higher temperature capabilities, reduced friction, corrosion resistance, increased strength and other requirements.

The following insert materials are typical of those specifically engineered to meet the demanding requirements of our customers’ applications:

304 Stainless Steel


This is the most popular insert material, and it will satisfy most application requirements for strength, corrosion resistance and temperature capability. The inserts can be used in applications with a temperature range from -320° F to 800° F. Cold rolling the stainless steel wire to a diamond shape work hardens it to a tensile strength above 200,000 PSI, a hardness of Rc 43-50 and a smooth 8-16 micro-inch finish. The inserts become slightly magnetic from the work hardening that occurs during the manufacturing process (approx. 2-10 G/O). The insert material is covered by specifications AS7245, NASM8846 and alloy number UNS S30400.

Inconel X-750


Inserts are supplied in this material for higher temperature capability and reliability applications. Inconel X-750 inserts have approximately the same strength and hardness characteristics of 304 stainless steel inserts, but can be used in environments up to 1,000° F. The material is a nickel-chromium alloy, made precipitation hardenable by the additions of aluminum and titanium. It has good rupture resistance at higher temperatures, good corrosion and oxidation resistance and lower permeability than 304 stainless steel inserts (< 1.0 G/O). Typical applications include gas turbines, rocket engines, nuclear reactors, pressure vessels, and various aircraft components operating in higher temperature environments. The insert material is covered by specification AS7246.

Phosphor Bronze


Inserts made from this material are ideal for salt water applications and have superior corrosion resistance over 304 Stainless Steel and Inconel X-750, although it is not as strong as either material. It has a tensile strength of approximately 140,000 PSI and a hardness of HRB 95. Phosphor Bronze inserts are also used in applications requiring very low permeability (< 1.0 G/O) and electrical connectivity and conductivity, and they can be used in environments up to 250° F. Typical applications Include Naval vessels, aircraft instrumentation paper and textile manufacturing, automotive systems, mining and drilling equipment, pumps and valves, and electrical connectors. The insert material is covered by specification AMS7247.

Nitronic 60®

Nitronic 60

Inserts made from Nitronic 60 are specifically engineered to eliminate galling and fretting when used with stainless steel screws. The surface friction between the mating screw and the Nitronic 60 insert is superior to 304 Stainless Inserts due to the additions of silicon and manganese to the alloy which limits the wear and galling, thus particulate matter is eliminated completely or minimized. The inserts require no additional coatings or platings, making them ideal for use in a vacuum as there is no out gassing, and they are not limited by the lower temperature capabilities of some platings and coatings, e.g. cadmium and dry film lubricant. The inserts are non-magnetic (< 1.0 G/O), have good corrosion resistance, a tensile strength of approximately 200,000 PSI, and a hardness of Rc 43-50 and can be used in temperatures up to 500° F. Typical applications include the semiconductor and aerospace industries. The material is metal alloy number UNS S21800.

Nimonic 90®

Inserts made from this material are used in high temperature environments where pressure and heat are extreme such as jet engines. It is a nickel-chromium-cobalt alloy that is precipitation hardenable and having high stress-rupture strength at elevated temperatures. Nimonic 90 is an ideal material for applications in aircraft parts and gas turbine components, such as jet engine exhaust nozzles. Typically free running inserts are used in environments with temperatures up to 1200° F and locking inserts up to 900° F. The chemical composition of Nimonic 90 is Ni 54%, Cr 18-21%, Co 15-21%, Ti 2-3%, and Al 1-2%. The material is covered by British Standard BS HR 503.


Inserts made from Titanium have a superior strength to weight ratio over 304 Stainless Steel inserts. They also provide very good corrosion resistance and are non-magnetic. Titanium inserts are slightly lower in tensile strength (150,000 to 220,000 PSI) and hardness (Rc 35-43), but are approximately 45% lighter in weight than 304 Stainless Steel inserts, making them ideal where weight reduction is critical. Titanium is very stable and its low coefficient of thermal expansion makes it an excellent choice for use in aerospace applications, such as satellites that must survive temperature fluctuations from sub-zero to 600° F (maximum temperature for insert applications). Titanium is used in biomedical applications; as it is compatible with the human body it is used extensively for applications that involve biological implants. Titanium inserts are covered by material specifications AMS 4957 and AMS 4958A.

Nitronic 60® is a registered trademark of AK Steel.

Nimonic 90® is a registered trademark of Special Metals Corporation.

If you have any questions contact the KATO Tech-Group. To view more technical articles please visit KATOpedia.