In oxy-acetylene ‘‘back-hand’’ (rightward) gas welding technique, what range of angles between the welding torch and the workpiece is generally recommended for proper puddle control and penetration?

Introduction / Context:

Gas welding uses two principal torch manipulations—fore-hand (leftward) and back-hand (rightward). The recommended torch angle is different for each because the direction of heat flow, puddle protection, and filler addition change with technique. Choosing the correct angle range ensures steady molten pool control and proper penetration without excessive oxidation or undercutting.

Given Data / Assumptions:

• Back-hand (rightward) oxy-acetylene welding on mild steel plate of moderate thickness.
• Neutral flame and standard nozzle selection.
• Operator maintains normal travel speed.

Concept / Approach:

In the back-hand technique, the torch points toward the completed weld and heat is directed more into the thicker, already-heated metal, aiding penetration. The commonly recommended torch angle to the work is around 40°–50° for back-hand welding, whereas fore-hand typically uses a lower angle (≈30°–40°). Holding too steep or too shallow an angle affects shielding, puddle support, and bead shape.

Step-by-Step Solution:

Verification / Alternative check:

Training manuals list 30°–40° for fore-hand and 40°–50° for back-hand as baseline angles, corroborating the recommended values for typical joints.

Why Other Options Are Wrong:

• 30°–40°: more characteristic of fore-hand technique.
• 50°–60° and 60°–70°: too steep; risk narrow bead and excessive oxidation/undercut.
• 20°–30°: too shallow; poor puddle coverage and inconsistent penetration.

Common Pitfalls:

• Confusing torch angles between fore-hand and back-hand methods.
• Overcompensating angle to correct travel speed errors, leading to defects.

Final Answer:

40°–50°