Miscellaneous Fasteners

the heavy-duty fasteners. Otherwise, their construction features are about the same. Figure 2-12 shows the parts of a light-duty Dzus fastener. Notice that they include a spring and a stud. The spring is made of cadmium-plated steel music wire, and is usually riveted to an aircraft structural member. The stud comes in a number of designs (as shown in views A, B, and C) and mounts in a dimpled hole in the cover assembly. When the panel is being positioned on an aircraft, the spring riveted to the structural member enters the hollow center of the stud. Then, when the stud is turned about one-fourth turn, the curved jaws of the stud slip over the spring and compress it. The resulting tension locks the stud in place and secures the panel. Miscellaneous Fasteners Some fasteners cannot be classified as rivets, turnlocks, or threaded fasteners. Included in this category are connectors, couplings, clamps, taper and flat-head pins, snap rings, studs, and heli-coil inserts. FLEXIBLE CONNECTORS AND COUPL- INGS.—A variety of clamping devices are used in connecting ducting sections to each other or to various components. Whenever lines, components, or ducting are disconnected or removed for any reason, you should install suitable plugs, caps, or coverings on the openings to prevent the entry of foreign materials. You should also tag the various parts to ensure correct reinstallation. You should exercise care during handling and installation to ensure that flanges are not scratched, distorted, or deformed. Flange surfaces should be free of dirt, grease, and corrosion. The protective flange caps should be left on the ends of the ducting until the installation progresses to the point where removal is necessary. In most cases it is mandatory to discard and replace seals and gaskets. You should ensure that seals and gaskets are properly seated and that mating and alignment of flanges are fitted. This will prevent the excessive torque required to close the joint, which imposes structural loads on the clamping devices. Adjacent support clamps and brackets should remain loose until installation of the coupling has been completed. Figure 2-12.—Dzus fastener. 2-9