Sockets are classified by size according to two factors.  One  is  the  size  of  the  square  opening,  which fits on the square drive lug of the handle. This size is known as the drive size. The other is the size of the opening  in  the  opposite  end,  which  fits  the  nut  or  bolt. The  standard  toolbox  can  be  outfitted  with  sockets having  1/4-,  3/8-,  and  1/2-inch-square  drive  lugs. Larger  sets  are  usually  available  in  the  tool  room  for temporary  checkout.    The  openings  that  fit  onto  the bolt or nut are usually graduated in 1/16-inch sizes. Sockets are also made in deep lengths to fit over spark plugs and long bolt ends. Socket  Handles There are four types of handles used with these sockets.  (See  fig.  1-8.)  Each  type  has  special advantages,  and  the  experienced  worker  chooses  the one best suited for the job at hand. The square driving lug on the socket wrench handles has a spring-loaded ball that fits into a recess in the socket receptacle.  This  mated  ball-recess  feature  keeps  the socket engaged with the drive lug during normal usage. A  slight  pull  on  the  socket,  however, disassembles  the  connection. RATCHET.  – The ratchet handle has a reversing lever  that  operates  a  pawl  (or  dog)  inside  the  head  of the tool. Pulling the handle in one direction causes the  pawl  to  engage  the  ratchet  teeth  and  turn  the socket. Moving the handle in the opposite direction causes  the  pawl  to  slide  over  the  teeth,  permitting  the handle to back up without moving the socket. This allows rapid turning of the nut or bolt after each partial turn of the handle. With the reversing lever in one position, the handle can be used for tightening. In  the  other  position,  it  can  be  used  for  loosening. HINGED HANDLE. – The hinged handle is also very  convenient.  To  loosen  tight  nuts,  swing  the handle at right angles to the socket. This gives the greatest  possible  leverage.  After  loosening  the  nut  to the  point  where  it  turns  easily,  move  the  handle  into the vertical position and then turn the handle with the fingers. SLIDING  T-BAR  HANDLE.  – When you are using  the  sliding  bar  or  T-handle,  the  head  can  be positioned  anywhere  along  the  sliding  bar.  Select  the position that is needed for the job at hand. SPEED  HANDLE.  – The speed handle is worked like  the  woodworker’s  brace.  After  the  nuts  are  first loosened with the sliding bar handle or the ratchet handle,  the  speed  handle  can  be  used  to  remove  the nuts  more  quickly. In  many  instances  the  speed handle is not strong enough to be used for breaking loose  or  tightening  the  nut.  The  speed  socket  wrench should be used carefully to avoid damaging the nut threads. Accessories Several  accessory  items  complete  the  socket wrench set. Extension bars of different lengths are made to extend the distance from the socket to the handle.  A  universal  joint  allows  the  nut  to  be  turned with  the  wrench  handle  at  an  angle.  Universal  sockets are  also  available.  The  use  of  universal  joints,  bar extensions, and universal sockets in combination with appropriate  handles  makes  it  possible  to  form  a variety  of  tools  that  will  reach  otherwise  inaccessible nuts  and  bolts. Another  accessory  item  is  an  adapter,  which allows you to use a handle having one size of drive and  a  socket  having  a  different  size  drive. For example, a 3/8- by 1/4-inch adapter makes it possible to turn all 1/4-inch-square drive sockets with any 3/8-inch-square  drive  handle. TORQUE  WRENCHES There  are  times  when,  for  engineering  reasons,  a definite force must be applied to a nut or bolt head. In such cases a torque wrench must be used. For example,  equal  force  must  be  applied  to  all  the  head bolts  of  an  engine.  Otherwise,  one  bolt  may  bear  the brunt  of  the  force  of  internal  combustion  and ultimately  cause  engine  failure. The  three  most  commonly  used  torque  wrenches are  the  deflecting  beam,  dial  indicating,  and micrometer  setting  types  (fig.  1-10).  When  using  the deflecting beam and the dial indicating torque wrenches,  read  the  torque  visually  on  a  dial  or  scale mounted on the handle of the wrench. To use the micrometer setting type, unlock the grip and adjust the handle to the desired setting on the micrometer-type scale, then relock the grip. Install the  required  socket  or  adapter  to  the  square  drive  of the  handle.  Place  the  wrench  assembly  on  the  nut  or bolt  and  pull  in  a  clockwise  direction  with  a  smooth, 1-8