Turnbuckles are fitted in the cable assembly for the purpose of making minor adjustments in cable length and for adjusting cable tension. One of the terminals has right-hand threads and the other has left-hand threads. The barrel has matching right- and left-hand internal threads. The end of the barrel with the left-hand threads can usually be identified by a groove or knurl around that end. When installing a turnbuckle in a control system, it is necessary to screw both of the terminals an equal number of turns into the barrel. It is also essential that you screw both turnbuckle terminals into the barrel until not more than three threads are exposed. After you adjust a turnbuckle properly, it must be safetied. We will discuss the methods of safetying turnbuckles later in this chapter. TAPER PINS Taper pins are used in joints that carry shear loads and where the absence of clearance is essential. See figure 5-17. The threaded taper pin is used with a taper pin washer and a shear nut if the taper pin is drilled. Use a self-locking nut if the taper pin is undrilled. When a shear nut is used with the threaded taper pin and washer, the nut is secured with a cotter pin. FLAT HEAD PINS The flat head pin is used with tie-rod terminals or secondary controls, which do not operate continuously. The flat head pin should be secured with a cotter pin. The pin is normally installed with the head up. See figure 5-17, view C. This precaution is taken to maintain the flat head pin in the installed position in case of cotter pin failure. FLEXIBLE CONNECTORS/CLAMPS Some of the most commonly used clamps are shown in figure 5-18. When installing a hose between two duct sections, the gap between the duct ends should be one-eighth inch minimum to three-fourths inch maximum. When you install the clamps on the connection, the clamp should be one-fourth inch minimum from the end of the connector. Misalignment between the ducting ends should not exceed one-eighth inch maximum. Marman type clamps, commonly used in ducting systems, should be tightened to the torque value indicated on the coupling. Use the torque value as specified on the clamp or in the applicable maintenance instruction manual. Q5-9. What are five fasteners that are included in the category of miscellaneous fasteners? AIRCRAFT ELECTRICAL SYSTEM HARDWARE LEARNING OBJECTIVE: Identify the special hardware found in an aircraft's electrical system. An important part of aircraft electrical maintenance is determining the correct type of electrical hardware for a given job. You must become familiar with wire and cable, connectors, terminals, and bonding. 5-12 ANF0517 STATIONARY MEMBER STATIONARY MEMBER PLAIN TAPER PIN MOVABLE MEMBER MOVABLE MEMBER COTTER PIN COTTER PIN CASTELLATED NUT TAPER PIN WASHER THREAD TAPER PIN FLAT HEAD PIN WASHER A.  PLAIN TAPER PIN INSTALLED B.  THREADED TAPER PIN INSTALLED C.  FLAT HEAD PIN INSTALL Figure 5-17.—Types of aircraft pins.