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## Prick 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: 

• 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. 

## Center Punch 

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: 

• 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. 

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## Automatic Center 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] 

## Transfer Punch 

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] 

## Drive 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] 

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