182 Summary • Arc welding presents dangers of electrical shock, fumes and gases, hot metal, arc rays, and fi re. The application of proper safety precautions prevents injury to personnel and damage to equipment. • Two methods to start an arc are to scratch the electrode on the metal and then withdraw it, or to use a straight up-and-down or pecking motion. • The arc length determines the voltage and amperage across the arc. Therefore, the arc length must remain fairly constant while welding. • The arc length should be about equal to the diameter of the electrode. • In SMAW, a backhand or drag travel angle is usually used. • Two angles are used to describe how to hold or position an electrode in any arc welding process. The travel angle describes the position of the electrode as it is tilted along the weld axis. The work angle describes the position of the electrode as it tilts from side to side about the weld axis. • Drag welding is a welding technique in which the electrode covering is in contact with the base metal. Drag welding ensures a constant arc length. • Each weld bead, or weld pass, must be cleaned by chipping and brushing. • Reading the weld bead provides information about amperage setting, arc length, and travel speed. • Welding defects include overlap, undercut, slag inclusions, and porosity. Overlap occurs when the weld toe is not fused into the base metal. Undercut occurs when the base metal at the weld toe area is melted but is not fi lled with fi ller metal. Slag inclusions are caused when slag is trapped during a multiple-pass weld. Porosity is a defect that can be seen on the surface of some welds. Review Questions Answer the following questions using the information provided in this chapter. Know and Understand 1. Which of the following statements is not true? A. Do not touch the electrode and the workpiece at the same time. B. Never make polarity or current range changes while the machine is under load. C. Always wear clothing that is fl ame- resistant. D. Always wear clear safety glasses that provide UV protection when looking at the welding arc. 2. True or False? The electrode holder is held with two hands, like a baseball bat. 3. Which of the following is one correct way to strike an arc? A. Scratch the electrode on the base metal. B. Scratch the electrode coating on the base metal. C. Scratch the electrode holder on the base metal. D. Scratch the base metal on the worktable. 4. Which of the following results in the least arc blow? A. DCEN. B. DCEP. C. AC. D. All are equal. 5. True or False? A stringer bead made with a 1/8″ electrode should be 1/4″ to 1/2″ wide. 6. True or False? The work angle is the position of the electrode as it is tilted along the weld axis. 7. When restarting an arc, how far in front of the existing crater is the arc struck? A. 1/8″ B. 1/4″ C. 3/8″ D. 1/2″ Copyright Goodheart-Willcox Co., Inc.