SUMMER 2019

64 THE DISTRIBUTOR’S

64 THE DISTRIBUTOR’S LINK COILOK FROM LIMIT LOCK LTD 38a Ahad Haam, Raanana, 4321120, ISRAEL TOLL-FREE 1-877-343-2770 TEL 919-741-4860 EMAIL info@CoiLok.com WEB www.CoiLok.com MAKING NEW & EXISTING BOLTED JOINTS VIBRATION RESISTANT Locking fasteners come in many shapes and sizes. They all try to solve a long-time problem in bolted joints: preventing unintentional loosening. Known solutions such as split lock washers, double nuts, nylon insert nuts or prevailing torque solutions have all been shown to be useful in static applications, but to fail vibration testing. Nevertheless, in the absence of effective alternatives, these solutions are used to prevent loosening under vibration. An examination of the three main causes of loosening in correctly torqued joints helps assess fasteners used in critical bolted joints subject to dynamic loads. Mechanical Shock: Sudden impacts - whether alternating or dynamic - are readily caused by machinery, military applications, off road transportation, etc. These sudden and severe forces can cause a bolted joint to slip and loosen. National Aerospace and Military Tests NAS 3350/3354 and NASM 1312-7 test the ability of a fastener system to withstand this mechanical shock, and fasteners used in joints subject to mechanical shock should be shown to pass these important tests. Vibration: Over many decades, vibration experiments on bolted joints have demonstrated that small but frequent transverse vibration between the sections of a joint relative to the bolt head or nut cause loosening. Repeated transverse movement works loose the friction the bolt and nut use in holding the joint together. Eventually, vibration causes the bolt and/or nut to “turn loose”, causing the joint to lose its clamping force. The Junker test was developed to test the performance of fasteners in bolted joints subject to transverse vibration. The standard for this test is DIN 65151. Embedding: Normally design engineers will account for the settling of a joint when it may relax after installation. Embedding, which leads to clamp load loss and joint loosening, can often be observed in softer work materials such as woods, soft metals or polished metals. It is for this reason that manufacturers of wedge locking washers and serrated washers/nuts often recommend their products only when the contact surfaces are as hard as the washers. To secure a joint in such a way that it can withstand loosening is no small task. A new product on the horizon is the CoiLok, which accomplishes vibration resistance while also providing versatility and reusability in one cost effective package. CoiLok is a small spring-like locking device that screws over the bolted connection and locks the nut firmly in place. It can be used on new bolted connections or retrofitted to existing connections. CoiLok uses three working principles to prevent loosening: [1] Thread Wedge Effect (TWE): Solid wedging between the threading of the bolt and nut threading, [2] Axial compression of the bolt threading, and [3] Radial compression on the bolt’s minor thread areas. CoiLok is tested to withstand severe vibration, providing effective bolting security resistant to loosening. BUSINESS FOCUS ARTICLE COILOK