What is Weld Capping & Practical Welding Tips

2026-06-02

Basic Introduction

A full weld has three parts. The root pass makes sure the metal joins well. The fill pass smooths the groove. The capping pass is the last top layer.

Capping changes how the weld looks and if it passes visual checks. It keeps the weld size correct. It makes clean weld lines. It also covers small flaws on the surface. Good capping helps the weld pass all inspections.

Pre-Work

Clean away slag, rust and dirt 20mm around the weld area. Grind the fill pass so it sits 0.5–1mm lower than the base metal. Use 3.2mm welding rods. Set the electric current 10–30A lower than the current for fill work. Keep the arc short, between 0.5mm and 1.5mm. Check the edges of the groove.

Key Skills

Weaving: Move the rod in straight lines or small crescent shapes. Stop for 0.5–1 second at both sides. This helps the metal join TIGhtly. Weld slowly and keep a steady pace.

Prevent undercut: Do not use strong current. Do not move too fast. Hold the rod at a 70–80 degree angle. Grind small flaws smooth. Reweld the area if the flaw is serious.

Joint treatment: Start the arc 10mm in front of the old weld hollow. Warm the metal for a short time. Use a short arc to fill the weld hollow. For multiple weld lines, place weld joints 5–10mm apart.

Different positions:

Flat: Keep the same speed and rod movement range.

Horizontal: Move the rod in small swings. Stay a little longer on the upper side.

Vertical: Tilt the rod slightly. Move a bit faster.

Overhead: Use an extra short arc and low current.

6G pipe: Change speed and rod movement to fit the pull of gravity.

Common Issues & Fixes

Undercut: Use lower current. Stop at weld sides. Move more slowly.

Slag & rough surface: Clean the area completely. Keep your hand steady while welding.

Uneven weld height/width: Match current and moving speed. Keep the same rod movement range.

Bad joints: Follow standard steps to start the arc and fill weld hollows. Place joints apart from each other.

Learn to control the melted metal and keep steady movements. Practice flat welding first. Then learn other welding positions. Pay attention to small details to make good welds.