Undercut is the horizontal inside corner joint usually is a(n) ____

Undercut is the horizontal inside corner joint usually is a(n) ____

• A. Depression in the lower piece
• B. Depression along the upper edge of the weld on the vertical piece
• C. Depression along the outer edge of the horizontal piece
• D. Overhang of the metal at the toe of the weld

Answer: (B)

Undercut is a groove melted into the base metal at the weld toe that remains unfilled by weld metal. In a horizontal inside corner joint, this defect commonly appears as a depression along the upper edge of the weld where it meets the vertical piece. The geometry of the inner corner concentrates heat at that edge, and if the weld bead doesn’t fully fill the groove, a notch forms along the upper edge of the vertical member. This weakens the joint by removing material at the weld toe rather than adding metal to fill the corner. Other descriptions describe different issues: a depression in the lower piece would not be the typical location for undercut in this joint, a depression along the outer edge of the horizontal piece is another defect, and an overhang at the toe is excess weld extending beyond the edge, not an undercut.

Undercut is a groove melted into the base metal at the weld toe that remains unfilled by weld metal. In a horizontal inside corner joint, this defect commonly appears as a depression along the upper edge of the weld where it meets the vertical piece. The geometry of the inner corner concentrates heat at that edge, and if the weld bead doesn’t fully fill the groove, a notch forms along the upper edge of the vertical member. This weakens the joint by removing material at the weld toe rather than adding metal to fill the corner.

Other descriptions describe different issues: a depression in the lower piece would not be the typical location for undercut in this joint, a depression along the outer edge of the horizontal piece is another defect, and an overhang at the toe is excess weld extending beyond the edge, not an undercut.