420 Modern Welding often used. In addition, the tip is usually pointed in the direction the torch is traveling. If even a small tip size seems too large, change the tip angle to 15°–20°, as shown in Figure 14-21. This lowered angle effectively increases the thickness of the metal being cut. On very thin metal, holding the tip near vertical produces too much preheating. The resulting cut is very poor. Many welders actually rest the edge of the tip on the metal during this process. Be careful to keep the end of the preheating inner cone just above the metal. 14.6.2 Cutting Thick Steel Steel over 1/2″ (13mm) thick should be cut by holding the torch so the tip is perpendicular to the surface of the base metal being cut. Figure 14-22 shows the position of the cutting torch tip orifi ce when cutting thick steel. A cut is normally started at the edge of the stock. The torch may be moved from left to right, or from right to left. Figure 14-23 shows the progress of a cut in thick steel. Either direction is good if it permits the welder to look into the kerf and check cutting prog- ress. If a line of travel is chalked on the metal, torch movement from right to left enables a right-handed welder to most easily follow the guidelines on the metal. When cutting thick steel, remember that the thicker the steel, the greater the time that is required to raise the temperature of the steel high enough to make clean cuts. Note in Figure 14-24A that the heat must be applied in a broad area around the cut. After the steel has been heated to a dull cherry red, cutting begins when the oxygen jet is opened by pressing on the cutting lever. See Figure 14-24B. As soon as the cutting action starts, move the torch tip at a steady rate. See Figure 14-25. To start a cut faster on thick plate, the welder begins at the corner of the metal by slanting the torch in the direction opposite the direction of travel, as shown in Figure 14-26A. As the corner is cut, the welder moves the torch to a vertical position, until fi nally the total thickness is cut, as shown in Figure 14-26B. The welder may then proceed with the cut. Two other methods are used to start cuts. One is to nick the edge of the metal, where the cut is to start, with a cold chisel. The sharp edges of the nick heat up and oxidize rapidly when the cutting torch is applied. This makes it possible to start cutting without preheating the entire edge of a thick plate. The second method is to place an iron fi ller rod under the preheating fl ames at the edge of a thick plate. The fi ller rod reaches the cherry red temperature Figure 14-21. Recommended procedure for cutting thin steel. Notice that the two preheat fl ames are in line with the kerf (cut). Direction torch movement 15°–20° Figure 14-22. A recommended technique for cutting thick steel. Note the position of the torch tip preheat orifi ces in relation to the line of the cut. Two preheat fl ames are in the line of the torch progress. This position enables one preheat fl ame to be ahead of the cut, two fl ames to heat the sides of the cut, and one fl ame to heat down in the kerf. Section A-A Front view Travel 90° A A Side view 90°