Chapter 4 Review Questions (Auto Body Repair and Finishing Text)

Transcription

1 Chapter 4 Review Questions (Auto Body Repair and Finishing Text) Name: Date: Blk: 1. Q. Explain the terms "elasticity" and "elastic limit" as they refer to automotive sheet metal. 2. Q. Explain with diagrams the physical changes that take place when sheet metal is bent. 3. Q. When metal is bent in its cold state, the area of the bend becomes work hardened. Why? 4. Q. a. Explain how the molecule movement is different when the panel is stamped compared to a bend made by hand or because of an accident. b. What determines the amount of work hardening in a panel? 5. Q. Define the terms "bumping", "metal finishing" & "filling" 6. Q. Why is it important to straighten damaged areas as much as possible before "filling" them over? 7. Q. What three variables govern the force exerted by the hammer on the metal? 8. Q. When dollying why is it not usually necessary to lift the hammer for the next hammer blow?

2 9. Why should a light flat faced dinging hammer be used for most metal-straightening operations? 10. Q. Explain the principals of the hammer and dolly straightening action. 11. Q. What variables determine the lifting action of the dolly against the metal? 12. Q. a. Explain the results obtained by: i. heavy, hammer on -dolly blows ii. hammer off-dolly blows iii. light, hammer on-dolly blows i. ii. iii. b. what type of dolly should be used with each method? i. ii. iii. 13. Q. What prevents a dent or damaged area from springing back to its original position? 14. Q. a. Where are the ridges and channels usually found in a damaged area? b. What type of metal is usually found between the ridges and channels? 15. Q. Why is the point of contact in a damaged area usually the most severely damaged? 16. Q. Explain the correct procedure for removing the under seal, or sound deadener, from the underside of a panel.

3 17. Q. Why should the underseal be removed before beginning the dollying operations? 18. Q. Draw a diagram of a minor dent. List the identifiable areas. Indicate in sequence where the dolly should be placed and the hammer blows directed to remove the dent. 19. Q. a. What three methods are used to detect high and low spots in the metal? b. How should the hand be held and moved on the metal when checking for high and low spots? 20. Q. Why is it possible to hold the file at an angle to the direction of travel and still obtain the correct cut? 21. Q. Explain how the body file is held and pushed when filing i. A flat panel: ii. a crowned panel 22. Q. What is the purpose of Cross and X filing a panel? 23. Q. Why should the first and final file scratch patterns be made lengthwise along the length of the panel? 24. Q. What type of impressions are raised by: i. a blunt pick; ii. a sharp pick? 25. Q. What type of pick should a beginner use to raise the low spots? why?

4 26. Q. Why should solder or body fillers not be levelled by the grinder? 27. Q. Why should an area of metal not be continually ground? 28. Q. List 3 safety rules that should be followed while using the grinder. 29. Q. How far should the back side of the disc be off the metal? 30. Q. Why should too much pressure not be applied to the grinder while grinding? 31. Q. a. Explain the two methods in which the disc grinder is used b. For what purpose is each method used? 32. Q. Why is a disc cut in a square, hexagon or octagon shapes sometimes used to grind welds or rough areas? 33. Q. Why are the front and rear of the vehicle purposely designed to fold and crush when they are involved in an accident? 34. Q. How thick is 20 gauge steel in thousands of an inch and in mm? 35. Q. A stamped panel has more "resistance to bending" than sheet metal in its cold-rolled form. Explain why. 36. Q. Explain the difference between low carbon steel, high-strength steel, and high-strength low-alloy steel. 37. Q. List an advantage and disadvantage of using high-strength steel.

5 38. Q. How must the high-strength steel be welded? Why? 39. Q. Why is a crowned panel stronger than a flat panel? 40. Q. What are three factors that govern the strength of any panel? 41. Q. Why must any flanges and ridges in a panel always be straightened first? 42. Q. List the correct order in which the areas of a panel should be straightened. 43. Q. a. Lis and explain the two types of buckles that are found in sheet metal damage. b. Which type is the hardest to repair? Why? 44. Q. a. Describe direct and indirect damage conditions. b. When both types of damage are present, which type should be repaired first? Why? 45. Q. List an advantage and a disadvantage of using a mechanical jack in place of a hydraulic jack. 46. Q. Explain how the pressure is released on a mechanical jack. 47. Q. List the four main components of the hydraulic jack and explain the purpose of each. 48. Q. Why must the ram plunger be fully returned before oil is added to the pump? 49. Q. List the three types of hydraulic-jack rams and explain where the oil enters each one.

6 50. Q. Why are the extension tubes designed to bottom against the attachments when they are connected together? 51. Q. Why should the extensions be installed on the fixed end of the ram for a long push? 52. Q. Why should the ram plunger never be over-extended? 53. Q. Explain what is meant by a combination-crowned panel. 54. Q. a. Explain the movement of the metal when a pressure force is exerted directly against a high-crowned panel. b. At what point does this same force start to exert a tension force on the surrounding elastic metal? 55. Q. Explain what effect pressure or tension will have on a high-crowned panel when it travels in a direction parallel to the high crown. Why? 56. Q. Are the forces in a low-crowned panel more of the pressure or tension type? Why? 57. What types of forces and buckles will be present in the high and low crowned areas of a damaged combination-crowned panel? Why? 58. Q. Explain the straightening procedures for: i. a high-crowned area; ii. A low-crowned area; iii. A combination-crowned area. 59. Q. Why, when prying out a crease, should only a small area be pried at a time? 60. Q. A crease should be worked out from the shallowest to the deepest end. Why?