Chapter 26 Oxyfuel Gas Cutting 397 Copyright Goodheart-Willcox Co., Inc. • Cutting tip size. • Oxygen pressure. • Torch forward speed. • Steady torch movement. • Torch tip angle. • Distance of preheat fl ames from the base metal. Figure 26-8 shows an example of a good cut along with examples of poorly-made, unacceptable cuts. The characteristics of each cut are also given. Goodheart-Willcox Publisher Figure 26-7. Correct alignment of the preheating orifices on the cutting line. At least two preheating orifices should align with the cutting line. Goodheart-Willcox Publisher Figure 26-6. The effect of using too much oxygen when cutting steel. Notice how the kerf widens at the bottom of the plate to create a bell-mouthed kerf. AWS Figure 26-8. Typical edge conditions resulting from oxyfuel gas cutting operation: (1) A good cut in 1″ (25 mm) plate. The edge is square, and the drag lines are essentially vertical and not too pronounced. (2) The preheat flames were too small for this cut and the cutting speed was too slow, causing bad gouging at the bottom. (3) The preheating flames were too long, with the result that the top surface melted over. The cut edge is irregular and there is an excessive amount of adhering slag. (4) The oxygen pressure was too low, causing the top edge to melt over because of the slow cutting speed. (5) The oxygen pressure was too high and the nozzle size too small, resulting in loss of control of the cut. (6) The cutting speed was too slow, with the result that the irregularities of the drag lines are emphasized. (7) The cutting speed was too fast, resulting in a pronounced break in the drag line and an irregular cut edge. (8) The torch travel was unsteady, resulting in a wavy and irregular cut edge. (9) The cut was lost and not carefully restarted, causing bad gouges at the restarting point. Steel plate Slag Bell-mouthed kerf Preheating flame orifice Cutting line (axis) Cutting oxygen orifice