AS9120B, ISO 9001:2015, and FAA AC 0056B Accredited
Posted on April 9, 2025 Eon Lewis Aerospace
In aerospace engineering, fasteners must be able to endure extreme conditions like intense vibrations, high loads, and repeated maintenance cycles to reliably secure critical assemblies and structures. When handling lightweight alloys like aluminum and magnesium, traditional tapped threads often fall short in terms of providing necessary durability and load resistance for security. This is where helical inserts come in, such components offering a high-performance solution that benefits a range of applications. In this blog, we will cover what helical inserts are, their importance, and how they enhance thread strength, so keep reading to learn more.
Helical inserts are precision-formed wire coils designed to be inserted into tapped holes. Once installed, they provide a high-strength internal thread that is superior to the original in terms of load distribution and wear resistance. These inserts are often made of stainless steel or heat-resistant alloys, making them ideal for the demanding conditions of aerospace applications.
There are two primary types of helical inserts: free-running inserts and self-locking inserts. Free-running inserts provide a smooth thread for standard fastening, whereas self-locking inserts incorporate a friction-generating feature to resist loosening due to vibration.
A major advantage of helical inserts is their ability to distribute load more evenly across the length of threads. Unlike traditional threads that are cut directly into soft materials, the insert’s helical shape reduces stress concentration at any single point. This minimizes the chances of thread shear, even under fluctuating or high-tensile loads.
In aerospace structures where components are frequently exposed to tensile forces, maintaining strong thread engagement is essential. Helical inserts are thus used to increase the effective diameter and length of a thread contact, enabling a joint to handle significantly higher tensile loads. This enhancement reduces the likelihood of fasteners pulling out under stress, a critical advantage when working with thin-walled sections or lightweight alloys.
Frequent assembly and disassembly can quickly degrade threads in soft materials, making them prone to stripping. Once threads deform, a fastener will begin to lose grip, leading to loosening or total failure. Helical inserts act as a hardened interface between the fastener and the base material, absorbing torque forces more effectively than unreinforced threads. They preserve thread form even after repeated fastener engagement, ensuring that maintenance procedures do not unnecessarily reduce the reliability of the threaded joint over time.
Aircraft structures endure constant vibration that is generated by engines, airflow, and general movement. This vibration can cause fasteners to gradually rotate loose if not properly secured, making it a great concern for design. Self-locking helical inserts address this issue by incorporating a deformed section within the coil that grips the fastener threads tightly, creating friction that resists loosening. Unlike chemical thread lockers or external locking mechanisms, the insert’s locking action is built-in, does not degrade over time, and requires no additional components.
In repair and overhaul scenarios, stripped threads often result in scrapped parts or costly delays. Helical inserts provide a reliable method for restoring damaged threads to a condition that often exceeds the strength of the original, extending component life and reducing maintenance costs. This makes making these inserts an essential aspect in aerospace MRO operations.
Modern aerospace design heavily makes use of materials that offer high strength-to-weight ratios. However, these materials cannot always support strong threads on their own, making it necessary at times for inserts to be added. Helical inserts enable the use of such alloys by reinforcing fastening points, which preserves structural strength without compromising weight efficiency.
If you are looking for helical insert components or any other part type of need, Emergent Fastening is your go-to source for high-quality solutions. Operated by ASAP Semiconductor, an AS9120B, ISO 9001:2015, and FAA AC 00-56B accredited distributor, our website features a selection of more than 2 billion part listings that are sourced from over 5100 reliable manufacturers and suppliers. Our portal has a simple and easy-to-use interface that allows customers to find any desired part seamlessly, so be sure to begin exploring at your leisure. Once you find aerospace components of interest, you just need to fill out a Request for Form (RFQ) form online to begin the procurement process. Within 15 minutes of our review, one of our experienced team members will connect with you to provide a customized solution.
We hope that you will visit us again the next time you need hardware and fasteners parts and make us your strategic purchasing partner.
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