1. Dr Simin Nasseri Southern Polytechnic State University 1 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Chapter 7 Engineering Graphics I Dr Simin Nasseri Southern Polytechnic State University

2. Dr Simin Nasseri Southern Polytechnic State University 2 1.Sketching is an important method of quickly communicating design ideas. 2.Sketching is a way of thinking as it is a method of recording ideas and communicating to others. 3.Most new designs are first recorded using design sketches.

3. Dr Simin Nasseri Southern Polytechnic State University 3 Figure 7.1 3 Methods for creating drawings: Sketches Using T- squares, triangles, etc. CAD produced drawings

4. Dr Simin Nasseri Southern Polytechnic State University 4 Figure 7.3 A technical sketch: Producing a rough, preliminary drawing representing a product or structure.

5. Dr Simin Nasseri Southern Polytechnic State University 5 Figure 7.26 Sketching the idea (ideation sketch) Subsequent document sketch

6. Dr Simin Nasseri Southern Polytechnic State University 6 Figure 7.4 Multi-view sketch: Good for someone who understands technical drawings

7. Dr Simin Nasseri Southern Polytechnic State University 7 Figure 7.5 Pictorial view: Good for communicating the design. Suitable for nontechnical people.

8. Dr Simin Nasseri Southern Polytechnic State University 8 Figure 7.8 Grid papers: Square paper ( 4 to 10 lines per inch) Isometric grid paper Perspective grid paper: To create pictorial sketches

9. Dr Simin Nasseri Southern Polytechnic State University 9 Figure 7.9

10. Dr Simin Nasseri Southern Polytechnic State University 10 Figure 7.10 The line is built up from a sequence of 2, 3 or more passes with a pencil.

11. Dr Simin Nasseri Southern Polytechnic State University 11 Figure 7.11

12. Dr Simin Nasseri Southern Polytechnic State University 12 Figure 7.12 Hold your pencil correctly, and have a relaxed grip. Use a strip of paper to draw lines parallel to the edges of the paper.

13. Dr Simin Nasseri Southern Polytechnic State University 13 Figure 7.13 How to draw a circle: Each side of the square is equal to the diameter of the circle. Draw the diagonals and mark the midpoints. On the diagonals mark 2/3 of the distance between the center and each corner. Connect all the points. An alternative method

14. Dr Simin Nasseri Southern Polytechnic State University 14 Figure 7.14 Examples of poorly drawn circles (with flat arcs and sharp corners)

15. Dr Simin Nasseri Southern Polytechnic State University 15 Figure 7.15 Contour sketch: Observe the outline of the object while sketching, Improves your sketching ability.

16. Dr Simin Nasseri Southern Polytechnic State University 16 Practice: Look at an object and try to sketch it upside down. (Sketch the outline of the object by concentrating on the geometric forms not the names of the parts).

17. Dr Simin Nasseri Southern Polytechnic State University 17 Sketching techniques: 1- Proportion is important. It is the ratio between any two dimensions of an object. Figure 7.22

18. Dr Simin Nasseri Southern Polytechnic State University 18 Figure 7.18 2- Draw the bounding box. 1- Consider the correct proportion. 3- Draw the construction lines. These are every light thin lines representing the details of the object. 4- Finish the sketch with darker lines.

19. Dr Simin Nasseri Southern Polytechnic State University 19 Figure 7.19 You can use construction line to find the center of squares or rectangles.

20. Dr Simin Nasseri Southern Polytechnic State University 20 Figure 7.21 Sketching identically proportioned squares

21. Dr Simin Nasseri Southern Polytechnic State University 21 Figure 7.23 Grid paper is used to scale an object.

22. Dr Simin Nasseri Southern Polytechnic State University 22 Figure 7.24 Sketching at a distance: 1.Stand at a distance, 2.Hold a pencil at arm’s length in front of you, 3.Align the tip of the pencil with one edge of a feature, 4.Mark the length of the feature with your thumb, 5.Translate the same length to your sketch. 6.Repeat this for other lengths. Don’t change your position.

23. Dr Simin Nasseri Southern Polytechnic State University 23 Figure 7.28 Most common types of projections: Isometric

24. Dr Simin Nasseri Southern Polytechnic State University 24 Most common types of projections: 1.Multiview (Showing 2 dimensions) 2.Pictorial (Showing 3 dimensions) OR Most common types of projections: 1.Parallel 2.Perspective projections

25. Dr Simin Nasseri Southern Polytechnic State University 25 Figure 7.29 Perspective projection Although it is more realistic, it is for larger objects like a house or bridge. Is this projection multiview or pictorial? Is it a parallel projection or perspective?

26. Dr Simin Nasseri Southern Polytechnic State University 26 Figure 7.30 Isometric projection: A type of parallel projection that represents all 3 dimensions in one image. Practice: Draw a chair.

27. Dr Simin Nasseri Southern Polytechnic State University 27 Figure 7.31

28. Dr Simin Nasseri Southern Polytechnic State University 28 Figure 7.32 Isometric representations of circles

29. Dr Simin Nasseri Southern Polytechnic State University 29 Figure 7.33 Practice: Draw a circle on profile and top planes.

30. Dr Simin Nasseri Southern Polytechnic State University 30 Figure 7.34

31. Dr Simin Nasseri Southern Polytechnic State University 31 Practice: 2- Sketch the isometric semicircle, shown here. 1- Sketch this cylinder using the method you learned:

32. Dr Simin Nasseri Southern Polytechnic State University 32 Figure 7.35 Practice: Rotate the object and sketch it again.

33. Dr Simin Nasseri Southern Polytechnic State University 33 Figure 7.36 Isometric sketches of common objects.

34. Dr Simin Nasseri Southern Polytechnic State University 34 Figure 7.52 Use a piece of scrap paper and mark one half of the major axis (AC) and one half of the minor axis (AB). Place A on the center and mark two points representing C and two points representing B (draw major and minor axes). Place C on the minor axis and hold B on the minor axis at any time, then place a mark at point A. Repeat this and connect all the points.