Safety Note Punch and Chisel Eye Protection Always wear eye protection when using chisels or punches. 2.9.1 Punches A center punch and the prick punch are similar, but the prick punch has a sharper point. Either one can be used to mark parts before disas- sembly. This ensures proper alignment when the parts are reassembled. A punch is also used to make an indentation in metal before drilling a hole. The indentation prevents the drill bit from wandering (moving off center). A pin punch has a straight shank for driving pins or rivets out of a hole. A similar tool, the drift punch, is often used for aligning holes in different sections of material. Safety Note Damaged Punch Point Never use a punch with a dull, chipped, or deformed point. Such a damaged punch could slip and cause injury. 2.9.2 Cold Chisels Cold chisels are used to cut off damaged or badly rusted nuts, bolts, rivet heads, or other fasteners, Figure 2-46. The angle and thickness of the cutting edge is designed to give maximum cut and durability. A dull cold chisel can slip and cause injury. Sharpen the hardened cutting edge as needed with a hand file or a whetstone (special sharpening stone). 2.8.4 Using Snips Safely • Always wear safety goggles when using snips. • Be careful of the sharp cutting edges on snip blades. • Always wear gloves to protect against cuts from sharp metal edges. • Use snips only for cutting soft metal or other soft materials. • Use only hand pressure for cutting. Never hammer on the snip or use your foot to put extra pressure on the cutting edge. • Perform periodic maintenance to keep snips efficient and safe. Occasionally oil the pivot bolt, and protect the cutting edges from damage. Sharpen the edges as necessary. Never try to sharpen an aviation snip, however. This removes the serrations that grip the metal so it does not slip. 2.9 Punches and Cold Chisels Punches, Figure 2-45, and cold chisels, are called struck tools, because they are struck with a hammer. They are made of special alloy steel that is heat-treated and drawn to provide maximum resistance to impact. They are designed to direct the force of each blow toward the center, or body, of the tool. Tools must be struck squarely. Blows that are off-center can damage the chisel or mate- rial or cause injury. A B C Goodheart-Willcox Publisher Figure 2-45. Punches are usually struck with a ball pein hammer. A—Center punch. B—Pin punch. C—Drift punch. 32 Heating and Cooling Essentials Copyright Goodheart-Willcox Co., Inc.