Undercut Limits Calculator

Determine undercut acceptance per AWS D1.1 and other codes.

Leave blank if continuous

AWS D1.1 Undercut Limits

Condition Max Depth Length Limit
Static - Primary 1/32" (0.8mm) OR 1/16" (1.6mm)* No limit if depth OK
Static - Secondary 1/16" (1.6mm) No limit
Cyclic Loading 0.01" (0.25mm) No undercut preferred

*1/16" allowed for 2" in any 12" weld length per AWS D1.1

Understanding Undercut

What is Undercut?

Undercut is a groove melted into the base metal adjacent to the weld toe or root that is left unfilled by weld metal. It creates a stress concentration that can reduce fatigue life.

Causes of Undercut

  • Excessive Current: Too hot melts base metal faster than it fills
  • Fast Travel Speed: Insufficient time to fill toe area
  • Improper Angle: Arc directed at plate edge instead of joint
  • Wrong Electrode Size: Electrode too large for joint
  • Incorrect Technique: Poor manipulation or weave pattern

Prevention Methods

  • Reduce welding current (typically 5-10%)
  • Slow travel speed, especially at weld toes
  • Pause at toe areas during weave
  • Adjust electrode angle to direct heat into joint
  • Use smaller electrode diameter