Chapter 15 Oxyfuel Gas Cutting 425 Copyright Goodheart-Willcox Co., Inc. To cut larger holes in steel plate, the typical steel cut- ting method described in this chapter is recommended. Cutting a very large hole is best done with an automatic machine or with a radius bar attachment clamped to the torch head. Pro Tip Before freehand cutting a large hole or any other shape in steel plate, draw the shape on the surface of the metal with special chalk. You can then follow the outline for an accurate cut. 15.5.4 Shape Cutting Cutting torches are most commonly used to cut straight lines however, clean cuts can be made by skilled welders following any pattern or curvature. This is referred to as shape cutting. Shape cutting can be done freehand with a variety of special cutting attachments, such as a circle cut- ting guide or by setting up an automated cutting torch. Manual freehand oxyfuel gas cutting on both plate and pipe in the horizontal and vertical positions is required for advanced welder certifi cation. Shape cut- ting in the horizontal position is diffi cult and requires much practice. See Figure 15-28. 15.5.5 Cutting Bevels Another important torch cutting operation is the cutting of bevels (also called chamfers) for bevel and V-groove joints on the edges of steel plate prior to welding. See Figure 15-29. Thicker pieces of steel must have the beveled edge prep- aration so the weld penetrates through the thickness of the metal. Goodheart-Willcox Publisher Figure 15-28. This welding student is shape cutting a circle and a square in 3/8″ (10 mm) steel plate in the horizontal position. A—Heating the base metal with preheat flames to prepare for piercing a hole. B—The cutting oxygen lever is pressed to pierce the metal just inside the line of the shape. Cutting then continues along the predrawn lines. A B Goodheart-Willcox Publisher A B Goodheart-Willcox Publisher Figure 15-29. A—A method of obtaining a beveled edge on thick metal plate using a cutting torch. Note the alignment of the cutting tip holes. Two are in line with the kerf and one on each side. B—A steel angle (angle iron) is effectively used as a guide to make a beveled cut. Goodheart-Willcox Publisher