Root Gap Calculator
Calculate optimal root gap and root face for groove weld fitup.
Typical Root Gap by Process
| Process | Open Root | With Backing |
|---|---|---|
| GTAW | 0-3mm | 3-5mm |
| SMAW | 2-4mm | 5-6mm |
| GMAW Short Arc | 2-3mm | 5-6mm |
| FCAW | 3-5mm | 5-8mm |
| SAW | N/A | 0-6mm |
Root Gap Fundamentals
Why Root Gap Matters
- Penetration: Proper gap ensures complete root fusion
- Burn-Through: Excessive gap causes melt-through and drop-through
- Lack of Fusion: Too tight prevents adequate root penetration
- Fit-up Stress: Forcing closed gap creates residual stress
Root Face (Land)
- Purpose: Prevents burn-through, supports weld pool
- Typical Size: 1.5-3mm (1/16" - 1/8")
- Variation: Thinner for GTAW, thicker for SMAW
Fitup Best Practices
- Consistency: Maintain uniform gap along joint length
- Tack Welds: Properly sized and spaced to prevent closure
- Hi-Lo: Minimize mismatch, typically 1.5mm max for pressure work
- Cleaning: Remove mill scale, rust, and contaminants from joint faces