In oxy arc cutting, what is the heat source that initiates the cutting?

• A. Arc between cutting rod and steel
• B. Flame of fuel gas
• C. Electric current along the work
• D. Pressure of oxygen

Answer: (A)

In oxy arc cutting, the heat to start the cut comes from the electric arc between the cutting rod (carbon electrode) and the steel. This arc concentrates intense heat at the metal surface, bringing it up to its ignition temperature. Once preheated, a high-velocity stream of oxygen oxidizes the hot metal, continuing the cut. The flame of fuel gas isn’t used in this process, and the fuel gas flame would belong to oxy-fuel cutting, not oxy arc. The pressure of oxygen helps sustain the cut but doesn’t provide the initial heating, and electric current along the workpiece doesn’t create the heat that starts the cut.