422 Modern Welding Copyright Goodheart-Willcox Co., Inc. A B C 1/16″ to 1/8″ (1.5 mm to 3 mm) Goodheart-Willcox Publisher Figure 15-20. Progress of a cut in thick steel. A—Preheat flames are 1/16″ to 1/8″ (1.5 mm to 3 mm) from the metal surface. The torch is held in this spot until the metal becomes cherry red. B—The torch is moved slowly to maintain the rapid oxidation, even though the cut is only partway through the metal. C—As the cut is made through the entire thickness, the bottom of the kerf lags slightly behind the top edge. A B Goodheart-Willcox Publisher Goodheart-Willcox Publisher Figure 15-21. An OFC operation on a thick steel I-beam. A—The beam is preheated to a dull cherry red color with a welding torch prior to being cut. B—After the beam is preheated, a cutting attachment is installed on the torch. The operator presses the cutting lever, which opens the cutting oxygen orifice. A B Goodheart-Willcox Publisher Goodheart-Willcox Publisher Figure 15-22. Guiding the cutting torch through the left hand. The cut is being made from the right to left. A—The left hand is held near the torch head. B—The torch is being slid through the left hand as cut progresses.