Chapter 26 Oxyfuel Gas Cutting 401 Copyright Goodheart-Willcox Co., Inc. Exercise 26-3 Manually Cutting Beveled Edges— Using Steel Angle 1. Obtain a piece of mild steel to cut that measures at least 1/4″ × 6″ × 6″ (6 mm × 150 mm × 150 mm). 2. Obtain a piece of angle iron that measures at least 1″ × 1″ × 7″ (25 mm × 25 mm × 175 mm). Also, obtain a clamp or clamps to attach the angle iron. 3. Using soapstone or chalk, mark out five lines on the surface of the plate to be cut 1″ (25 mm) apart. Refer to the following figure. 4. Select the correct cutting tip. Install the tip in the torch. 5. Position the steel angle on its legs, as shown in Figure 26-13. 6. Turn on the station and set the correct pressures. Light the torch and adjust for neutral preheating flames. 7. Hold the cutting torch tip on the incline of the steel angle iron. The centerline of the tip should be aligned with the line to be cut. The preheating flames should be about 1/16″–1/8″ (1.5 mm– 3.0 mm) above the metal. Do not apply too much force to the angle iron since it is not clamped in place, because this may cause it to shift or move. 8. Squeeze the oxygen cutting valve when the metal turns an orange-red color (1500°F/816°C). The cut will begin. 9. Progress at a constant rate to complete the cut. 10. Repeat the process for the next four lines. 6″ (150 mm) 1″ (25 mm) 1″ (25 mm) 1″ (25 mm) 1″ (25 mm) 1″ (25 mm) 1″ (25 mm) 6″ (150 mm) Cutting Machines Oxyfuel gas cutting machines make high-quality cuts at a faster rate than manual fl ame cutting. Cutting machines are often used to make long cuts. They are also used to cut multiple pieces with close tolerances. The basic types of cutting machines are: • Motor-driven carriage and track. • Motor-driven beam-mounted torch. Motor-Driven Carriage and Track A motor-driven carriage uses a variable-speed motor to carry a cutting torch along a straight or curved track. See Figure 26-14. This same type carriage is used to cut and bevel pipe. The speed of the motor can be adjusted to control the speed of the cut. Torch movement and fl ame height are consistent because the torch moves along a track. High-quality cuts can be made using a track- mounted carriage. The cutting torch used on a motor-driven carriage has a different appearance from a manual cutting torch. It still has conventional oxygen and acetylene valves. The cutting oxygen is also controlled with an oxygen fi nger valve. Using the rack-type gear on the cutting machine allows the welder to adjust the fl ame height by moving the torch up and down. The torch can also be adjusted horizontally to align it with the cutting line. In/out adjuster Counterweight Carriage Up/down adjuster Speed control Cutting torch Track Goodheart-Willcox Publisher Figure 26-14. The parts of a motor-driven carriage.