purpose and should be used only on the objects they are designed for. When you use a hand tool for other purposes, you usually damage both the tool and the object  it  is  used  on.  Use  screwdrivers  to  drive  and remove screws. Do not use them to scrape paint, as a pry bar or chisel, and certainly never use them to test an  electrical  circuit. STANDARD  SCREW DRIVER Three main parts make up the construction of the standard screwdriver (fig. 2-1, view A), the handle, the shank, and the end. The end (called the blade) fits into the screw slot. When using a screwdriver, select the proper size blade for the job intended. A blade too large or too small causes the screwdriver blade and the screwhead to become damaged. At least 75 per- cent of the screw slot should be filled by the blade for proper  fit. PHILLIPS HEAD SCREWDRIVER A  Phillips  head  screwdriver  (fig.  2-1,  view  B) differs in construction from a standard screwdriver only in that the tip is shaped to fit the special cavity in the  Phillips  screwhead.  A  standard  screwdriver  must never  be  used  in  a  Phillips  screwhead  as  damage  will occur to it. The Phillips cavity should be filled com- pletely  by  the  selected  driver  for  proper  fit. HAMMER The hammer (fig. 2-1. view G) most used by the ABF is the ball peen. The ball peen hammer is used for working metals, such as chiseling rivets and shear- ing  metal. COMBINATION  PLIERS Combination pliers (fig. 2-1, view C) are manu- factured with straight serrated jaws for gripping ob- jects. The pivots, with which the jaws are attached, are adjustable to fit different size objects. Pliers should not be used to grasp the shanks of screwdrivers to gain greater  twisting  force. DIAGONAL  PLIERS Diagonal pliers (fig. 2-1, view D) are used only for cutting small material such as wire or cotter pins. They   are   designed   specifically   for   cutting.   They should NOT be used for grasping objects such as nuts and bolts. ADJUSTABLE  WRENCHES An  adjustable  wrench  (fig.  2-1,  view  E)  is  not intended  to  replace  an  open-end  wrench,  but  it  is useful in working in restricted areas. In addition, it can  be  adjusted  to  fit  odd-sized  nuts  or  bolts.  This wrench is often called a knuckle buster because me- chanics  frequently  suffer  the  consequences  of  using  it improperly. PIPE WRENCHES A pipe wrench (fig. 2-1, view F) is primarily used for  rotating  round  stock  and/or  various  pipes  and  pip- ing. The most common pipe wrench is the Stillson. It has two jaws that have serrated teeth to provide a gripping ability. The larger jaw is a fixed jaw. The smaller jaw is adjustable and the weaker of the two jaws. Whenever a Stillson wrench is used, it should be applied in such a manner that the fixed jaw provides the  twisting  force.  These  wrenches  also  come  in  vary- ing lengths, which makes the jaw sizes vary. A Still- son   wrench   should   never   be   used   on   machined surfaces, as the teeth tend to mar or otherwise ruin the metal. The strap wrench (fig. 2-2) should be used instead of a Stillson to eliminate damage to soft metals. The strap wrench employs a heavy nylon strap. One end is attached to the wrench handle. while the other end is free  to  pass  around  the  object  to  be  rotated,  and  then back  through  the  locking  device  provided  on  the wrench  handle. SPANNER  WRENCHES Many special nuts are made with notches cut into their  outer  edge.  For  these  nuts  a  hook  spanner Figure   2-2.—Strap   wrench. 2-2