When stick welding, the cause of an undercut can be due to a number of factors. These include:
• Incorrect electrode angle - if the electrode is not held at the correct angle (usually around 15 degrees), it can result in an undercut.
• Electrode tip too far away from work piece - if the electrode tip is too far away from the work piece, it can also cause an undercut.
• incorrect current setting - if the current is set too low, it can cause an undercut.