Copyright Goodheart-Willcox Co., Inc. 432 Modern Welding 4. The offset between the entry point of the cutting jet at the top of the kerf and its exit point at the bottom of the kerf is called _____. A. slag B. drag C. slip D. chamfer 5. True or False? During cutting, the welder should move the torch away from the body rather than toward it in order to see into the kerf. 6. Placing an iron fi ller rod under the preheating fl ames at the edge of a thick plate _____. A. effectively increases the thickness of metal being cut B. decreases oxidation of the base metal C. is a method of starting a cut faster D. All of the above. 7. True or False? A pipe’s diameter determines what size cutting tip is needed to cut that pipe. 8. True or False? It is possible to cut a piece to length and to place a bevel on the metal at the same time. 9. True or False? The torch tip should be kept perpendicular to the pipe surface while cutting a pipe with a diameter of less than 4″ (100 mm). 10. Which statement about the oxyfuel gas gouging process is false? A. It uses a larger-diameter cutting tip orifi ce than oxyfuel gas cutting. B. It uses a lower oxygen cutting pressure than oxyfuel gas cutting. C. It cuts a V-shaped groove into the base metal surface. D. It can be used to open up a defect (crack) in a part. Apply and Analyze 1. In the oxyfuel gas cutting process, what is the purpose of the preheat fl ames after the cutting has begun? 2. In the oxyfuel gas cutting process, when is the cutting oxygen valve opened? 3. When adjusting pressures before lighting a cutting torch, why is it necessary to check the pressures with the torch cutting oxygen lever in the fully open position? 4. What oxygen and acetylene working pressures are used for cutting 1/2″ (13 mm) plate steel with a positive-pressure torch? 5. List two conditions that can cause the slag stream to excessively lag behind the torch tip. 6. Why is it necessary to provide a higher oxygen working pressure with a cutting torch than with a welding torch? 7. What is the cause of a bell-mouthed kerf? 8. How should the cutting torch be held, in relation to the work, when thin sheet steel is being cut? 9. How should the cutting torch be held, in relation to the work, when thick sheet steel is being cut? 10. What determines the size tip to be used for cutting pipe? 11. When piercing a hole in a plate, how is the torch held in relation to the base metal? 12. How do the requirements for preheat when piercing compare with preheat requirements for starting a cut on the edge of a plate? 13. Although automatic cutting machines are self-operating, what initial adjustments must be made by the operator to properly set up the machine? 14. Why should acetylene never be used at a pressure greater than 15 psig (103 kPa)? 15. Why is it important to know what material is to be cut before performing OFC? Critical Thinking 1. Automatic and semiautomatic cutting operations require very expensive equipment in comparison to manual cutting equipment. What are the various cost-saving factors that must be considered in deciding whether or not to invest in automatic or semiautomatic equipment? 2. What are the three necessary components required for a fi re to continue to burn (known as the fi re triangle)? Explain how the continuous oxyacetylene cutting of steel is accurately described as burning steel. Experiment 1. Turn on an oxyacetylene cutting outfi t and light the preheating fl ames. Adjust the oxygen and acetylene torch valves to produce carburizing fl ames, neutral fl ames, and fi nally oxidizing fl ames. Experiment with opening the cutting oxygen lever to see how it affects the preheating fl ames. Record the characteristics of each type of fl ame.