Fasteners on aircraft are designed for many different functions. Some are made for high-strength requirements, while others are designed for easy installation and removal.

Lock-bolt fasteners are designed to meet high-strength requirements. Used in many structural applications, their shear and tensile strengths equal or exceed the requirements of AN and NAS bolts. The lock-bolt pin, shown in view A of figure 2-6, consists of a pin and collar. It is available in two head styles: protruding and countersunk. Pin retention is accomplished by swaging the collar into the locking grooves on the pin.

The blind lock bolt, shown in view B of figure 2-6, is similar to the self-plugging rivet shown in figure 2-3. It features a positive mechanical leek for pin retention.

Hi-Lok Fasteners 

The hi-lok fastener, shown in figure 2-7, com-bines the features of a rivet and a bolt and is used for high-strength, interference-free fit of primary structures. The hi-lok fastener consists of a threaded pin and threaded locking collar. The pins are made of

Figure 2-6.Lock bolts.

Figure 2-7.Hi-lok fastener.

cadmium-plated alloy steel with protruding or 100-degree flush heads. Collars for the pins are made of anodized 2024-T6 aluminum or stainless steel. The threaded end of the pin is recessed with a hexagon socket to allow installation from one side. The major diameter of the threaded part of the pin has been truncated (cut undersize) to accommodate a 0.004-inch maximum interference-free fit. One end of the collar is internally recessed with a 1/16-inch, built-in variation that automatically provides for variable material thickness without the use of washers and without fastener preload changes. The other end of the collar has a torque-off wrenching device that controls a predetermined residual tension of preload (10%) in the fastener.

Jo-Bolt Fasteners 

The jo-bolt, shown in figure 2-8, is a high-strength, blind structural fastener that is used on difficult riveting jobs when access to one side of the work is impossible. The jo-bolt consists of three factory-assembled parts: an aluminum alloy or alloy steel nut, a threaded alloy steel bolt, and a corrosion-resistant steel sleeve. The head styles available for jo-bolts are the 100-degree flush head, the hexagon protruding head, and the 100-degree flush millable head.