as  shown  to  eliminate  possible  errors.  In  reassembly, refer first to the sets of punchmarks to determine the approximate position of the parts. Then line up the scribed  lines  to  determine  the  exact  position. To  make  the  intersection  of  two  layout  lines,  bring the point of the prick punch to the exact point of intersection  and  tap  the  punch  lightly  with  a  hammer. If  inspection  shows  that  the  exact  intersection  and  the punchmark do not coincide, as in view A of figure 1-37,  slant  the  punch  as  shown  in  view  B  and  strike again with the hammer, thus enlarging the punchmark and centering it exactly. When the intersection has been correctly punched, finish off with a light blow on the  punch  held  in  an  upright  position.  View  C  shows the  corrected  punchmark. DRIFT  punches,    sometimes  called    “starting punches,” have a long taper from the tip to the body. They  are  made  that  way  to  withstand  the  shock  of heavy blows. They may be used for knocking out rivets  after  the  heads  have  been  chiseled  off  or  for freeing  pins  that  are  “frozen”  in  their  holes. After  a  pin  has  been  loosened  or  partially  driven out, the drift punch may be too large to finish the job. The follow-up tool to use is the PIN PUNCH. It is designed to follow through the hole without jamming. Always use the largest drift or pin punch that will tit the hole. These punches usually come in sets of three to  five  assorted  sizes.  Both  of  these  punches  will have  flat  ends,  never  edged  or  rounded. Figure 1-37.-Marking the intersection of lines with a prick To remove a bolt or pin that is extremely tight, start  with  a  drift  punch  that  has  an  end  diameter  that is slightly smaller than the diameter of the object you are removing. As soon as the bolt or pin loosens, finish driving it out with a pin punch. Never use a pin punch for starting a pin, because it has a slim shank and a hard blow may cause it to bend or break. For  assembling  units  of  a  machine,  an ALIGNMENT (aligning) punch is invaluable. It is usually about 1-foot long and has a long gradual taper. Its purpose is to line up holes in mating parts. Hollow metal-cutting punches are made from hardened tool steel. They are made in various sizes and are used to cut holes in light gauge sheet metal. Other punches have been designed for special uses. One of these is the soft-faced drift. It is made of brass or fiber and is used for such jobs as removing shafts, bearings, and wrist pins from engines. It is generally heavy enough to resist damage to itself, but soft  enough  not  to  injure  the  finished  surface  on  the part  that  is  being  driven. You may have to make gaskets of rubber, cork, leather, or composition materials. For cutting holes in gasket  materials,  a  hollow  shank  GASKET  PUNCH may be used (fig. 1-35). Gasket punches come in sets of various sizes to accommodate standard bolts and studs. The cutting end is tapered to a sharp edge to produce  a  clean  uniform  hole.  To  use  the  gasket punch, place the gasket material to be cut on a piece of hard wood or lead so that the cutting edge of the punch  will  not  be  damaged.  Then  strike  the  punch with  a  hammer,  driving  it  through  the  gasket  where holes  are  required. TAPS AND DIES Taps and dies are used to cut threads in metal, plastics, or hard rubber. The taps are used for cutting internal  threads,  and  the  dies  are  used  to  cut  external threads. There are many different types of taps. However,  the  most  common  are  the  taper,  plug, bottoming,  and  pipe  taps  (fig.  1-38). The taper (starting) hand tap has a chamfer length of 8 to 10 threads. These taps are used when starting a tapping operation and when tapping through holes. 1-23 punch.