Inspection: The fillet welds must be the correct size. A convex weld bead must be formed with smooth and evenly spaced ripples. No undercut is permitted. Butt Joint Metal less than 1/4″ (6.4 mm) thick is welded using a square-groove butt joint. No edge preparation is required. A bevel-, V-, J-, or U-groove joint is used on thicker metal. The root pass is the fi rst and most important weld pass. Complete penetration to the opposite side of the metal can occur only on this weld pass. A keyhole, an enlarged root opening, must be seen throughout the root pass to ensure penetration. Refer to Figure 12-20. Additional weld passes must fuse with the base metal and the previous weld beads. The weld toes must fuse with the surface of the base metal. No undercut should be seen. A butt weld may be made from one or both sides. See Figure 12-21. Double-bevel-groove welds are used to ensure 100% fusion and penetration when welding thick sections. Less electrode material and welder time is required to weld a double-bevel- groove weld than to make a single-bevel-groove weld. 9. Clean the slag from the second pass and read the weld. 10. Make any change needed to the weld current. Decide if a change is needed in electrode angle or travel speed. Weld a third pass using E6010 to complete the weld joint. This pass must obtain penetration into the first pass, into the second pass, and into the second piece of the base metal. A C-shaped weld pool should be visible. 11. Clean the slag and read the weld. The completed three-pass weld should have a total leg size of about 3/8″ (10 mm) and a 1/2″ (13 mm) weld face. 12. Repeat steps 5–11, but use E6013 electrodes. Set the proper polarity and current. Complete two fillet welds using E6013 electrodes. 13. Repeat steps 5–11 using 5/32″ (4.0 mm) iron powder electrodes, such as E6027. The fillet weld size will be larger because the electrode diameter is larger. Remember to change the polarity and current setting on the welding machine if needed. 14. Compare the ease or difficulty of running a bead with each electrode type. Compare any differences in the appearance of the different welds. First pass Second pass Third pass Keyhole Goodheart-Willcox Publisher Figure 12-19. Three weld passes were used on this fillet weld. Each weld bead was stopped at a different point to show its placement. The first weld pass was laid in the root or corner with equal coverage of both plates. The second weld pass penetrates one-half on the first weld bead and one-half on the horizontal part. The third weld pass was laid from the second weld pass up to the vertical part. Goodheart-Willcox Publisher Figure 12-20. This is a keyhole as seen looking down into a bevel-groove butt joint. The enlarged keyhole shows that both pieces are being melted. Chapter 12 SMAW: Flat Welding Position 179 Copyright Goodheart-Willcox Co., Inc.