The KATO engineers’ exacting approach to technical fastener application solutions has lead them to testing inserts in a broad range of parent materials that go beyond the normal utilization of inserts in materials like aluminum and magnesium. KATO Tangless® and tanged inserts have been used for many years in applications in the aerospace, defense, ship-building, communication, automotive, power-generation and transportation industries to name a few. And, these many applications utilizing these various parent materials selected to meet their application requirements require an insert to optimize the fastener assembly.
Normally inserts are used to provide strong threads in light-weight materials or to provide locking threads or both. The basic advantages provided by KATO wire thread inserts are smooth free-running, reusable threads, or with locking inserts, self-locking torque on the male threaded member. Another advantage is balanced distribution of static and dynamic loads. In a conventional bolted assembly over 75% of the load is taken up by the first three threads of the tapped hole. Using a KATO insert, each coil flexes allowing each coil to carry its share of the load along every thread. This flexibility also compensates for lead and angle error in the tapped hole. The hardness of the insert and mirror-smooth finish assure virtually no tread wear and provide true clamping torque with minimum wrench torque.
When KATO engineers are asked if KATO inserts can be used in a particular material, the standard answer is yes, if a viable thread can be produced in that material to accept the insert; meaning by tapping, molding, etc. For example, inserts are used in plastics, but some plastics are not able to be tapped depending on their glass content, or if they are thermoplastics or thermoset plastics. In many applications like these the STI threads are molded in. A rule of thumb for using locking inserts in plastics is make sure the insert length is two (2) diameter minimum.
This will allow for better insert retention in the weaker materials and the locking torque will usually be lower than in metal parent materials.
Can KATO inserts be used in wood? The answer is yes, but why would you want to do this? There are many self-tapping inserts on the market that would eliminate the tapping operation required for a wire thread insert. However, one of our customers had a critical application in wood where he had to know that a thread existed prior to installing his insert, thereby assuring him that there was a secure assembly once he installed his bolt. Prior to using wire inserts, his assemblers were installing solid bushing self-tapping inserts using pneumatic tooling and stripping the wood parent material. After switching to KATO wire inserts, the customer’s engineer believed that the insert transferred the shear load from the bolt into an outward radial load, thus substantially increasing the assembly strength over the previous unreliable self-tapping insert. So, in critical applications, if it is the solution to the problem, wire inserts can be used in virtually any tappable material.
In many cases, the parent materials used in applications are selected for severe conditions like temperature, corrosion, high strength, space (vacuum), etc. Special insert materials are utilized in these parent materials to optimize the assemblies. These insert materials are discussed in KATO Insert Materials – Article 1009. You can also find valuable information on insert platings and coatings, and corrosion problems by visiting KATO Tech Info.
It is critical to remember that the length of the insert in an assembly is designed based upon the shear strength of the parent material. The tensile strength of the insert assembly should exceed the breaking (tensile) strength of the bolt. For further information on this please see Insert Assembly Tensile Strength – Article 1199 and The KATO Tensile Strength Wizard.
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