424 Modern Welding Copyright Goodheart-Willcox Co., Inc. With the proper equipment, extremely thick steel can be cut, Figure 15-27. Be sure to read and carefully fol- low all manufacturers’ tables and safety charts prior to attempting this type of cutting operation. 15.5.3 Piercing and Cutting Holes Holes can be pierced in steel plates and pipe rapidly and with accurate results. The term pierce means to produce a relatively small hole (in comparison to the size of the metal surface) through a steel plate or pipe. Piercing is commonly performed to start shape cut- ting away from the edges of a plate or pipe. To begin the process, hold the cutting torch with the tip perpendicular to the surface of the metal, and preheat the spot to be cut until it is a bright cherry red. After the metal is brought up to the proper temperature (1400°F, or 760°C), turn on the oxygen jet very slowly. Refer to Figure 15-28. At the same time, raise the nozzle enough to prevent the slag from being blown back into the nozzle orifi ces. More heat is required to preheat the surface for piercing than for starting a cut on an edge. Therefore, use a cutting tip that is at least one size larger than is recom- mended in Figure 15-9 for the metal thickness being cut. Until the steel plate is melted through the bottom sur- face, molten metal is blown upward by the pressure of the cutting oxygen. A B ESAB Welding and Cutting Products Figure 15-27. Very thick steel can be cut with the OFC process. A—A skilled welder uses a cutting torch to make an accurate cut on 8″ (20 cm) thick steel. B—Massive steel beams from the World Trade Center being cut. ESAB Welding and Cutting Products A B ESAB Welding and Cutting Products Figure 15-26. Special torches and tips are used for cutting very thick metal. A—A high-pressure cutting tip designed to accommodate the higher oxygen volume and pressure. B—The long torch body typically has feet to enable the welder to hold the torch steady while reaching and cutting. ESAB Welding and Cutting Products