Lockbolt Fastening Systems  Installation Procedure Also pioneered in the 1940s, the lockbolt is a two-piece  fastener that combines the features of a high-strength bolt  and a rivet with advantages over each.  [Figure 4-105]  In  general, a lockbolt is a nonexpanding fastener that has either  a collar swaged into annular locking grooves on the pin shank  or a type of threaded collar to lock it in place. Available  with either countersunk or protruding heads, lockbolts are  permanent type fasteners assemblies and consist of a pin  and a collar.  A lockbolt is similar to an ordinary rivet in that the locking  collar, or nut, is weak in tension and it is difficult to remove  once installed. Some of the lockbolts are similar to blind  rivets and can be completely installed from one side. Others  are fed into the workpiece with the manufactured head on the  far side. The installation is completed on the near side with  a gun similar to blind rivet gun. The lockbolt is easier and  more quickly installed than the conventional rivet or bolt and  eliminates the use of lockwashers, cotter pins, and special  nuts. The lockbolt is generally used in wing splice fittings,  landing gear fittings, fuel cell fittings, longerons, beams, skin  splice plates, and other major structural attachment. Often called huckbolts, lockbolts are manufactured by  companies such as Cherry$^{®}$ Aerospace (Cherry$^{®}$ Lockbolt),  Alcoa Fastening Systems (Hucktite$^{®}$ Lockbolt System),  and SPS Technologies. Used primarily for heavily stressed  structures that require higher shear and clamp-up values than  can be obtained with rivets, the lockbolt and Hi-lok$^{®}$ are often  used for similar applications. Lockbolts are made in various  head styles, alloys, and finishes.  The lockbolt requires a pneumatic hammer or pull gun  for installation. Lockbolts have their own grip gauge  and an installation tool is required for their installation.  [Figure 4-106]  When installed, the lockbolt is rigidly and  permanently locked in place. Three types of lockbolts are  commonly used: pull-type, stump-type, and blind-type. The pull-type lockbolt is mainly used in aircraft and primary  and secondary structure. It is installed very rapidly and has  approximately one-half the weight of equivalent AN steel  bolts and nuts. A special pneumatic pull gun is required for  installation of this type lockbolt, which can be performed by  one operator since buckling is not required. The stump-type lockbolt, although not having the extended  stem with pull grooves, is a companion fastener to the pull- type lockbolt. It is used primarily where clearance does not  permit effective installation of the pull-type lockbolt. It is  driven with a standard pneumatic riveting hammer, with  a hammer set attached for swaging the collar into the pin  locking grooves, and a bucking bar. The blind-type lockbolt comes as a complete unit or  assembly and has exceptional strength and sheet pull-together  characteristics. Blind-type lockbolts are used where only  one side of the work is accessible and generally where it is  difficult to drive a conventional rivet. This type lockbolt is  installed in a manner similar to the pull-type lockbolt. The pins of pull- and stump-type lockbolts are made of heat- treated alloy steel or high-strength aluminum alloy. Companion  collars are made of aluminum alloy or mild steel. The blind- type lockbolt consists of a heat-treated alloy steel pin, blind  sleeve, filler sleeve, mild steel collar, and carbon steel washer. These fasteners are used in shear and tension applications.  The pull-type is more common and can be installed by one  person. The stump type requires a two-person installation.  An assembly tool is used to swage the collar onto the serrated  grooves in the pin and break the stem flush to the top of the  collar. The easiest way to differentiate between tension and shear  pins is the number of locking grooves. Tension pins normally  have four locking grooves and shear pins have two locking  grooves. The installation tooling preloads the pin while  swaging the collar. The surplus end of the pin, called the  pintail, is then fractured. Installation of lockbolts involves proper drilling. The hole  preparation for a lockbolt is similar to hole preparation for a  Figure 4-105.  Lockbolts.  Figure 4-106.  Lockbolt grip gauge. 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 2 4 6 8  10  12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 INCH SCALE GRIP SCALE Shear and tension  pull-type pins Shear and tension  stump-type pins 4-52