Prick Punch Automatic Center Punch Transfer Punch Center Punch Drive Punch Figure 4-11.  Transfer punch. Figure 4-9.  Center punch. Figure 4-8.  Prick punch.  Figure 4-10.  Automatic center punch. A prick punch is primarily used during layout to place  reference marks on metal because it produces a small  indentation.  [Figure 4-8]  After layout is finished, the  indentation is enlarged with a center punch to allow for  drilling. The prick punch can also be used to transfer  dimensions from a paper pattern directly onto the metal.  Take the following precautions when using a prick punch:  The automatic center punch performs the same function as an  ordinary center punch, but uses a spring tension mechanism  to create a force hard enough to make an indentation without  the need for a hammer. The mechanism automatically strikes  a blow of the required force when placed where needed and  pressed. This punch has an adjustable cap for regulating  the stroke; the point can be removed for replacement or  sharpening. Never strike an automatic center punch with a  hammer.  [Figure 4-10] A transfer punch uses a template or existing holes in the  structure to mark the locations of new holes. The punch is  centered in the old hole over the new sheet and lightly tapped  with a mallet. The result should be a mark that serves to locate  the hole in the new sheet.  [Figure 4-11] A center punch is used to make indentations in metal as an  aid in drilling.  [Figure 4-9]  These indentations help the drill,  which has a tendency to wander on a flat surface, stay on  the mark as it goes through the metal. The traditional center  punch is used with a hammer, has a heavier body than the  prick punch, and has a point ground to an angle of about 60°.  Take the following precautions when using a center punch: The drive punch is made with a flat face instead of a point  because it is used to drive out damaged rivets, pins, and  bolts that sometimes bind in holes. The size of the punch  is determined by the width of the face, usually  1 ⁄ 8-inch to  1 ⁄ 4-inch.  [Figure 4-12] •  Never strike a prick punch a heavy blow with a  hammer because it could bend the punch or cause  excessive damage to the item being worked. •  Do not use a prick punch to remove objects from holes  because the point of the punch spreads the object and  causes it to bind even more. •  Never strike the center punch with enough force to  dimple the item around the indentation or cause the  metal to protrude through the other side of the sheet. •  Do not use a center punch to remove objects from holes  because the point of the punch spreads the object and  causes it to bind even more. Transfer punch Use old skin as template New skin 4-6