Electronics engineers now have access to enhanced electronics performance – including fastener resistance to vibrational loosening, drop shock, and high heat – thanks to the self-locking Spiralock internal thread form design in micro threaded inserts. STANLEY Engineered Fastening, a global provider of innovative fastening and assembly technologies, offers its self-locking Spiralock internal thread form design to more securely and cost-effectively attach components in compact electronic assemblies. The micro threaded inserts also improve fastener reusability and reduce overall assembly costs by eliminating the need for nylon patch or chemical adhesive application on screw threads.
Electronics can experience vibrational loosening, drop shock, thread damage, and high thermal heat cycles not only during use, but also during shipping, particularly if manufactured overseas. Yet traditional nylon patch screws and chemical adhesives may progressively lose their effectiveness under these conditions, especially if reused during assembly, inspection, or repair, as their bonding material wears away. These traditional thread-locking methods can also add to assembly cost and complexity, when the nylon patches or chemical adhesives are applied on screw threads.
In place of cumbersome nylon patches and chemical adhesives, STANLEY’s self-locking Spiralock internal thread form in micro threaded inserts can enhance electronics performance and assembly. The micro threaded inserts can be used in a full range of electronics – from handheld mobile devices to mainframes including smart phones, tablets, laptops, desktops and monitors – in sizes as small as M1, in any size thread or pitch necessary.
Spiralock threads, fasteners, and inserts have been proven in thousands of applications over many years. They accept standard male fasteners, eliminate the need for other locking devices, provide extensive reusability, streamline assembly since they are free spinning, and substantially reduce the potential for fatigue failure compared to standard threads.
The Spiralock thread form solves thread loosening and joint integrity issues by changing the physics of how the threads interact. In traditional 60° threads, the gap between the crests of the screw/bolt and the major diameter of the internal thread is where loosening begins.
With significant transverse motion, thermal variance, shock or impact, microscopic movements and preload loss occur in the fastener’s threads. This tiny clearance gap allows the bolt to minimally “slip” relative to the major diameter of the female threaded hole. Once preload loss begins, the joint will fail and lose most of its clamp load during service. Furthermore, with standard threads, most of the load is carried by the first few threads, where stress concentration and fatigue can lead to premature joint failure.
The Spiralock self-locking wedge ramp thread profile eliminates the clearance gap, locking the male fastener in place. The Spiralock wedge ramp creates line contact with the screw/bolt along the entire length of thread engagement, preventing any movement between the screw/bolt and Spiralock wedge locking ramp.
Since Spiralock is free running and begins to lock once torque is applied, tension is created between the male fastener and the Spiralock threads. This enables quick, smooth bolt rundown with minimal drag or resistance when threading components. It also reduces assembly cost, time, as well as extends thread lock reusability and product longevity.
The Spiralock micro threaded inserts can be installed into many types materials such as plastic components, steel chassis, and other materials that normally would utilise the conventional micro threaded inserts while using a patch screw as the means for locking.
Spiralock micro threaded inserts can be produced in various materials, such as brass, carbon steel, or stainless steel ultrasonic inserts or press-in inserts. Brass ultrasonic inserts resist corrosion and are ideal for use in plastics. Steel pressed-in inserts are typically made of carbon steel, often with an electroless nickel coating that resists corrosion and satisfies salt spray requirements; these inserts can be installed into aluminum materials to eliminate the risk of stripping and shearing.
To install the micro threaded inserts, press them into a mounting hole using either ultrasonic insertion equipment or a thermal press. When installed ultrasonically, friction and vibrational oscillation warms and softens the plastic surrounding the insert, allowing the insert to install into the plastic component. The plastic cools and solidifies around the knurls of the insert, locking the insert in place.
For more than 35 years, the Spiralock thread form has been used in extreme fastening applications where joint failure or loosening is not an option: from the main engines of NASA’s Space Shuttle, the Saturn Cassini orbiter and Titan Huygens probe to deep sea oil rigs, military and aerospace vehicles, as well as medical implants, artificial limbs, and heart pumps.