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TECHNICAL SKETCHING C H A P T E R T H R E E. Technical Drawing with Engineering Graphics, 14/e Giesecke, Hill, Spencer, Dygdon, Novak, Lockhart, Goodman.

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Presentation on theme: "TECHNICAL SKETCHING C H A P T E R T H R E E. Technical Drawing with Engineering Graphics, 14/e Giesecke, Hill, Spencer, Dygdon, Novak, Lockhart, Goodman."— Presentation transcript:

1 TECHNICAL SKETCHING C H A P T E R T H R E E

2 Technical Drawing with Engineering Graphics, 14/e Giesecke, Hill, Spencer, Dygdon, Novak, Lockhart, Goodman © 2012, 2009, 2003, Pearson Higher Education, Upper Saddle River, NJ All Rights Reserved. OBJECTIVES After studying the material in this chapter, you should be able to: 1. Define the terms vertex, edge, plane, surface, and solid. 2. Identify four types of surfaces. 3. Identify five regular solids. 4. Draw points, lines, angled lines, arcs, circles, and ellipses. 5. Apply techniques that aid in creating legible well-proportioned freehand sketches. 6. Apply techniques to draw irregular curves. 7. Create a single-view sketch. 8. Create an oblique sketch. 9. Create perspective sketches. 10. Create an isometric sketch of an object. Shaded Sketch Showing Details of Wire Placement. (Courtesy of Quantum Design.)

3 Technical Drawing with Engineering Graphics, 14/e Giesecke, Hill, Spencer, Dygdon, Novak, Lockhart, Goodman © 2012, 2009, 2003, Pearson Higher Education, Upper Saddle River, NJ All Rights Reserved. UNDERSTANDING SOLID OBJECTS Three-dimensional figures are referred to as solids. Solids are bounded by the surfaces that contain them. These surfaces can be one of the following four types: Planar Single curved Double curved Warped Regardless of how complex a solid may be, it is composed of combinations of these basic types of surfaces.

4 Technical Drawing with Engineering Graphics, 14/e Giesecke, Hill, Spencer, Dygdon, Novak, Lockhart, Goodman © 2012, 2009, 2003, Pearson Higher Education, Upper Saddle River, NJ All Rights Reserved. UNDERSTANDING SKETCHING TECHNIQUES break down complex shapes into simpler geometric primitives Look for the essential shapes of objects And use construction lines

5 Technical Drawing with Engineering Graphics, 14/e Giesecke, Hill, Spencer, Dygdon, Novak, Lockhart, Goodman © 2012, 2009, 2003, Pearson Higher Education, Upper Saddle River, NJ All Rights Reserved. SKETCHING TECHNIQUES The contours of an object are the main outlines that separate it from the surrounding space. One way to think about the contours of objects is to look at the contrast between the positive and negative space. Positive space is the space occupied by the object. Negative space is the unoccupied space around it.

6 Technical Drawing with Engineering Graphics, 14/e Giesecke, Hill, Spencer, Dygdon, Novak, Lockhart, Goodman © 2012, 2009, 2003, Pearson Higher Education, Upper Saddle River, NJ All Rights Reserved. VIEWPOINT AND SHADING As you sketch objects, keep in mind that you want to maintain a consistent viewpoint, like a camera does. Adding shading to your sketch can give it a more realistic appearance because it represents the way the actual object would reflect light. Hatching and stippling

7 Technical Drawing with Engineering Graphics, 14/e Giesecke, Hill, Spencer, Dygdon, Novak, Lockhart, Goodman © 2012, 2009, 2003, Pearson Higher Education, Upper Saddle River, NJ All Rights Reserved. EDGES AND VERTICES Edges An edge of the solid is formed where two surfaces intersect. Edges are represented in drawings by visible or hidden lines. Vertices A vertex (plural, vertices) of a solid is formed where three or more surfaces intersect.. Points and Lines A point is used to represent a location in space but has no width, height, or depth.

8 Technical Drawing with Engineering Graphics, 14/e Giesecke, Hill, Spencer, Dygdon, Novak, Lockhart, Goodman © 2012, 2009, 2003, Pearson Higher Education, Upper Saddle River, NJ All Rights Reserved. POINTS AND LINES A point is used to represent a location in space but has no width, height, or depth. A line is used in drawings to represent the edge of a solid object.

9 Technical Drawing with Engineering Graphics, 14/e Giesecke, Hill, Spencer, Dygdon, Novak, Lockhart, Goodman © 2012, 2009, 2003, Pearson Higher Education, Upper Saddle River, NJ All Rights Reserved. ANGLES An angle is formed by two intersecting lines. A common symbol for angle is. Showing Angles

10 Technical Drawing with Engineering Graphics, 14/e Giesecke, Hill, Spencer, Dygdon, Novak, Lockhart, Goodman © 2012, 2009, 2003, Pearson Higher Education, Upper Saddle River, NJ All Rights Reserved. DRAWINGS AND SKETCHES The following are important skills to keep in mind for sketches and drawings: 1.Accuracy. No drawing is useful unless it shows the information correctly. 2. Speed. Time is money in industry. Work smarter and learn to use techniques to speed up your sketching and CAD drawings while still producing neat accurate results. 3. Legibility. A drawing is a means of communicating with others, so it must be clear and legible. Give attention to details. Things that may seem picky and small as you are drawing may be significant and save money or even lives when the product is built. 4. Neatness. If a drawing is to be accurate and legible, it must also be clean.

11 Technical Drawing with Engineering Graphics, 14/e Giesecke, Hill, Spencer, Dygdon, Novak, Lockhart, Goodman © 2012, 2009, 2003, Pearson Higher Education, Upper Saddle River, NJ All Rights Reserved. FREEHAND SKETCHING Freehand sketches are a helpful way to organize your thoughts and record ideas. They provide a quick, low-cost way to explore various solutions to design problems so that the best choices can be made.

12 Technical Drawing with Engineering Graphics, 14/e Giesecke, Hill, Spencer, Dygdon, Novak, Lockhart, Goodman © 2012, 2009, 2003, Pearson Higher Education, Upper Saddle River, NJ All Rights Reserved. TECHNIQUE OF LINES The chief difference between a drawing and a freehand sketch lies in the character or technique of the lines. line patterns A good freehand line is not expected to be as rigidly straight or exactly uniform. A good freehand line shows freedom and variety, whereas a line drawn using CAD or instruments should be exact.

13 Technical Drawing with Engineering Graphics, 14/e Giesecke, Hill, Spencer, Dygdon, Novak, Lockhart, Goodman © 2012, 2009, 2003, Pearson Higher Education, Upper Saddle River, NJ All Rights Reserved. GOOD AND POOR TECHNIQUE

14 Technical Drawing with Engineering Graphics, 14/e Giesecke, Hill, Spencer, Dygdon, Novak, Lockhart, Goodman © 2012, 2009, 2003, Pearson Higher Education, Upper Saddle River, NJ All Rights Reserved. LINEWEIGHTS Even in freehand drawings, thick lines should be twice the width of thin lines. Thicknesses do not have to be exact, but there should be an obvious difference between thick and thin lines. Because visible lines and cutting- plane lines are the two thick line patterns, other lines should be distinctly thinner in comparison. To draw thick and thin lines freehand, you might like to keep two pencils handy, one that is razor sharp for thin lines and another that is dulled, to create thicker lines. As the sharp point becomes dulled, switch it with the dull pencil, and sharpen the other, so that there is always one sharp and one dulled point ready to use.

15 Technical Drawing with Engineering Graphics, 14/e Giesecke, Hill, Spencer, Dygdon, Novak, Lockhart, Goodman © 2012, 2009, 2003, Pearson Higher Education, Upper Saddle River, NJ All Rights Reserved. SKETCHING STRAIGHT LINES Most of the lines in an average sketch are straight lines. With practice, your straight lines will naturally improve, but these basics may help you improve quickly. Hold your pencil naturally, about 1" back from the point, and approximately at a right angle to the line to be drawn. Draw horizontal lines from left to right with a free and easy wrist and arm movement. Draw vertical lines downward with finger and wrist movements.

16 Technical Drawing with Engineering Graphics, 14/e Giesecke, Hill, Spencer, Dygdon, Novak, Lockhart, Goodman © 2012, 2009, 2003, Pearson Higher Education, Upper Saddle River, NJ All Rights Reserved. STRAIGHT LINE TIPS

17 Technical Drawing with Engineering Graphics, 14/e Giesecke, Hill, Spencer, Dygdon, Novak, Lockhart, Goodman © 2012, 2009, 2003, Pearson Higher Education, Upper Saddle River, NJ All Rights Reserved. STRAIGHT LINE TIPS CONTINUED…

18 Technical Drawing with Engineering Graphics, 14/e Giesecke, Hill, Spencer, Dygdon, Novak, Lockhart, Goodman © 2012, 2009, 2003, Pearson Higher Education, Upper Saddle River, NJ All Rights Reserved. STRAIGHT LINE TIPS CONTINUED…

19 Technical Drawing with Engineering Graphics, 14/e Giesecke, Hill, Spencer, Dygdon, Novak, Lockhart, Goodman © 2012, 2009, 2003, Pearson Higher Education, Upper Saddle River, NJ All Rights Reserved. STRAIGHT LINE TIPS CONTINUED…

20 Technical Drawing with Engineering Graphics, 14/e Giesecke, Hill, Spencer, Dygdon, Novak, Lockhart, Goodman © 2012, 2009, 2003, Pearson Higher Education, Upper Saddle River, NJ All Rights Reserved. STRAIGHT LINE TIPS CONTINUED…

21 Technical Drawing with Engineering Graphics, 14/e Giesecke, Hill, Spencer, Dygdon, Novak, Lockhart, Goodman © 2012, 2009, 2003, Pearson Higher Education, Upper Saddle River, NJ All Rights Reserved. METHODS FOR SKETCHING CIRCLES

22 Technical Drawing with Engineering Graphics, 14/e Giesecke, Hill, Spencer, Dygdon, Novak, Lockhart, Goodman © 2012, 2009, 2003, Pearson Higher Education, Upper Saddle River, NJ All Rights Reserved. METHODS FOR SKETCHING ARCS

23 Technical Drawing with Engineering Graphics, 14/e Giesecke, Hill, Spencer, Dygdon, Novak, Lockhart, Goodman © 2012, 2009, 2003, Pearson Higher Education, Upper Saddle River, NJ All Rights Reserved. METHODS FOR SKETCHING ELLIPSES

24 Technical Drawing with Engineering Graphics, 14/e Giesecke, Hill, Spencer, Dygdon, Novak, Lockhart, Goodman © 2012, 2009, 2003, Pearson Higher Education, Upper Saddle River, NJ All Rights Reserved. MAINTAINING PROPORTIONS The most important rule in freehand sketching is to keep the sketch in proportion, which means to accurately represent the size and position of each part in relation to the whole. To maintain proportions, first determine the relative proportions of height to width and lightly block them in. You can mark a unit on the edge of a strip of paper or use your pencil to gauge how many units wide and high the object is.

25 Technical Drawing with Engineering Graphics, 14/e Giesecke, Hill, Spencer, Dygdon, Novak, Lockhart, Goodman © 2012, 2009, 2003, Pearson Higher Education, Upper Saddle River, NJ All Rights Reserved. ONE-VIEW DRAWINGS Frequently, a single view supplemented by notes and dimensions is enough information to describe the shape of a relatively simple object. Note how thickness of the material is given as “0.25 BRASS” So, an additional view is not needed to dimensionally give the material thickness.

26 Technical Drawing with Engineering Graphics, 14/e Giesecke, Hill, Spencer, Dygdon, Novak, Lockhart, Goodman © 2012, 2009, 2003, Pearson Higher Education, Upper Saddle River, NJ All Rights Reserved. PICTORIAL SKETCHING A pictorial sketch represents a 3D object on a 2D sheet of paper by orienting the object so you can see its width, height, and depth in a single view.

27 Technical Drawing with Engineering Graphics, 14/e Giesecke, Hill, Spencer, Dygdon, Novak, Lockhart, Goodman © 2012, 2009, 2003, Pearson Higher Education, Upper Saddle River, NJ All Rights Reserved. AXONOMETRIC DRAWINGS Various types of pictorial drawings are used extensively in catalogs, sales literature, and technical work. They are often used in patent drawings; in piping diagrams; in machine, structural, architectural design, and in furniture design; and for ideation sketching. Axonometric (Courtesy of Douglas Wintin.)

28 Technical Drawing with Engineering Graphics, 14/e Giesecke, Hill, Spencer, Dygdon, Novak, Lockhart, Goodman © 2012, 2009, 2003, Pearson Higher Education, Upper Saddle River, NJ All Rights Reserved. PROJECTION METHODS The four principal types of projections: a Multiview b Axonometric c Oblique d Perspective

29 Technical Drawing with Engineering Graphics, 14/e Giesecke, Hill, Spencer, Dygdon, Novak, Lockhart, Goodman © 2012, 2009, 2003, Pearson Higher Education, Upper Saddle River, NJ All Rights Reserved. ISOMETRIC DRAWINGS STEPS…

30 Technical Drawing with Engineering Graphics, 14/e Giesecke, Hill, Spencer, Dygdon, Novak, Lockhart, Goodman © 2012, 2009, 2003, Pearson Higher Education, Upper Saddle River, NJ All Rights Reserved. OBLIQUE SKETCHING STEPS…

31 Technical Drawing with Engineering Graphics, 14/e Giesecke, Hill, Spencer, Dygdon, Novak, Lockhart, Goodman © 2012, 2009, 2003, Pearson Higher Education, Upper Saddle River, NJ All Rights Reserved. PERSPECTIVE DRAWING ONE-POINT STEPS…

32 Technical Drawing with Engineering Graphics, 14/e Giesecke, Hill, Spencer, Dygdon, Novak, Lockhart, Goodman © 2012, 2009, 2003, Pearson Higher Education, Upper Saddle River, NJ All Rights Reserved. PERSPECTIVE DRAWING TWO-POINT STEPS…

33 Technical Drawing with Engineering Graphics, 14/e Giesecke, Hill, Spencer, Dygdon, Novak, Lockhart, Goodman © 2012, 2009, 2003, Pearson Higher Education, Upper Saddle River, NJ All Rights Reserved. SHADING Shading can make it easier to visualize pictorial drawings, such as display drawings, patent drawings, and catalog drawings. Methods of Shading Ordinary multiview and assembly drawings are not shaded.

34 C H A P T E R F O U R GEOMETRIC CONSTRUCTION

35 Technical Drawing with Engineering Graphics, 14/e Giesecke, Hill, Spencer, Dygdon, Novak, Lockhart, Goodman © 2012, 2009, 2003, Pearson Higher Education, Upper Saddle River, NJ All Rights Reserved. OBJECTIVES 1. Identify the geometry that makes up basic 2D drawings. 2. Use board drafting or 2D CAD skills to create technical figures. 3. Describe the advantages of CAD contrasted with drawing with manual instruments

36 Technical Drawing with Engineering Graphics, 14/e Giesecke, Hill, Spencer, Dygdon, Novak, Lockhart, Goodman © 2012, 2009, 2003, Pearson Higher Education, Upper Saddle River, NJ All Rights Reserved. GEOMETRY REVIEW Triangles Quadrilaterals Polygons Circles Arcs

37 Technical Drawing with Engineering Graphics, 14/e Giesecke, Hill, Spencer, Dygdon, Novak, Lockhart, Goodman © 2012, 2009, 2003, Pearson Higher Education, Upper Saddle River, NJ All Rights Reserved. BISECTING A LINE OR CIRCULAR ARC Triangle and T-Square System Compass system

38 Technical Drawing with Engineering Graphics, 14/e Giesecke, Hill, Spencer, Dygdon, Novak, Lockhart, Goodman © 2012, 2009, 2003, Pearson Higher Education, Upper Saddle River, NJ All Rights Reserved. BISECTING A LINE WITH TRIANGLE AND T-SQUARE From endpoints A and B, draw construction lines at 30°, 45°, or 60° with the given line. Then, through their intersection, C, draw a line perpendicular to the given line to locate the center D…

39 Technical Drawing with Engineering Graphics, 14/e Giesecke, Hill, Spencer, Dygdon, Novak, Lockhart, Goodman © 2012, 2009, 2003, Pearson Higher Education, Upper Saddle River, NJ All Rights Reserved. TRIANGLES Inclined lines can be drawn at standard angles with the 45° triangle and the 30° x 60° triangle. The triangles are transparent so that you can see the lines of the drawing through them. A useful combination of triangles is the 30° x 60° triangle with a long side of 10" and a 45° triangle with each side 8" long.

40 Technical Drawing with Engineering Graphics, 14/e Giesecke, Hill, Spencer, Dygdon, Novak, Lockhart, Goodman © 2012, 2009, 2003, Pearson Higher Education, Upper Saddle River, NJ All Rights Reserved. ANY ANGLE IN 15° INCREMENTS With only a 30° x 60° triangle and a 45° triangle, you can draw any angle in 15° increments The bottom of the triangle in each case is resting on the blade of the T-square. Twenty-four 15° sectors are possible with just these two triangles used singly or in combination.

41 Technical Drawing with Engineering Graphics, 14/e Giesecke, Hill, Spencer, Dygdon, Novak, Lockhart, Goodman © 2012, 2009, 2003, Pearson Higher Education, Upper Saddle River, NJ All Rights Reserved. PROTRACTORS For measuring or setting off angles other than those obtainable with triangles, use a protractor. Plastic protractors are satisfactory for most angular measurements Nickel silver protractors are available when high accuracy is required

42 Technical Drawing with Engineering Graphics, 14/e Giesecke, Hill, Spencer, Dygdon, Novak, Lockhart, Goodman © 2012, 2009, 2003, Pearson Higher Education, Upper Saddle River, NJ All Rights Reserved. ANGLES… BISECTING AN ANGLE TRANSFERRING AN ANGLE

43 Technical Drawing with Engineering Graphics, 14/e Giesecke, Hill, Spencer, Dygdon, Novak, Lockhart, Goodman © 2012, 2009, 2003, Pearson Higher Education, Upper Saddle River, NJ All Rights Reserved. DRAWING A LINE PARALLEL TO A LINE AND AT A GIVEN DISTANCE For CurvesT-square Method

44 Technical Drawing with Engineering Graphics, 14/e Giesecke, Hill, Spencer, Dygdon, Novak, Lockhart, Goodman © 2012, 2009, 2003, Pearson Higher Education, Upper Saddle River, NJ All Rights Reserved. DRAWING A LINE THROUGH A POINT AND PERPENDICULAR TO A LINE When the Point Is Not on the LineWhen the Point Is on the LineT-square Method

45 Technical Drawing with Engineering Graphics, 14/e Giesecke, Hill, Spencer, Dygdon, Novak, Lockhart, Goodman © 2012, 2009, 2003, Pearson Higher Education, Upper Saddle River, NJ All Rights Reserved. TRIANGLES… DRAWING A TRIANGLE WITH SIDES GIVEN DRAWING A RIGHT TRIANGLE WITH HYPOTENUSE AND ONE SIDE GIVEN

46 Technical Drawing with Engineering Graphics, 14/e Giesecke, Hill, Spencer, Dygdon, Novak, Lockhart, Goodman © 2012, 2009, 2003, Pearson Higher Education, Upper Saddle River, NJ All Rights Reserved. LAYING OUT AN ANGLE Tangent Method Sine Method Chord Method Many angles can be laid out directly with the triangle or protractor.

47 Technical Drawing with Engineering Graphics, 14/e Giesecke, Hill, Spencer, Dygdon, Novak, Lockhart, Goodman © 2012, 2009, 2003, Pearson Higher Education, Upper Saddle River, NJ All Rights Reserved. DRAWING AN EQUILATERAL TRIANGLE Alternative Method

48 Technical Drawing with Engineering Graphics, 14/e Giesecke, Hill, Spencer, Dygdon, Novak, Lockhart, Goodman © 2012, 2009, 2003, Pearson Higher Education, Upper Saddle River, NJ All Rights Reserved. DRAWING A SQUARE You can use the AutoCAD Polygon command to draw squares. The Rectangle command is another quick way to make a square in AutoCAD. T-square Method Diameters Method Inscribed Circle Method

49 Technical Drawing with Engineering Graphics, 14/e Giesecke, Hill, Spencer, Dygdon, Novak, Lockhart, Goodman © 2012, 2009, 2003, Pearson Higher Education, Upper Saddle River, NJ All Rights Reserved. DRAWING A REGULAR PENTAGON Dividers Method Geometric Method

50 Technical Drawing with Engineering Graphics, 14/e Giesecke, Hill, Spencer, Dygdon, Novak, Lockhart, Goodman © 2012, 2009, 2003, Pearson Higher Education, Upper Saddle River, NJ All Rights Reserved. DRAWING A HEXAGON Each side of a hexagon is equal to the radius of the circumscribed circle Use a compass Centerline Variation Steps

51 Technical Drawing with Engineering Graphics, 14/e Giesecke, Hill, Spencer, Dygdon, Novak, Lockhart, Goodman © 2012, 2009, 2003, Pearson Higher Education, Upper Saddle River, NJ All Rights Reserved. DRAWING AN OCTAGON Given an inscribed circle, or distance “across flats”, use a T-square or straightedge and a 45° triangle to draw the eight sides tangent to the circle. Given a circumscribed square, (the distance “across flats”) draw the diagonals of the square. Then, use the corners of the square as centers and half the diagonal as the radius to draw arcs cutting the sides

52 Technical Drawing with Engineering Graphics, 14/e Giesecke, Hill, Spencer, Dygdon, Novak, Lockhart, Goodman © 2012, 2009, 2003, Pearson Higher Education, Upper Saddle River, NJ All Rights Reserved. FINDING THE CENTER OF A CIRCLE This method uses the principle that any right triangle inscribed in a circle cuts off a semicircle. Another method, slightly longer, is to reverse the procedure. Draw two nonparallel chords and draw perpendicular bisectors. The intersection of the bisectors will be the center of the circle.

53 Technical Drawing with Engineering Graphics, 14/e Giesecke, Hill, Spencer, Dygdon, Novak, Lockhart, Goodman © 2012, 2009, 2003, Pearson Higher Education, Upper Saddle River, NJ All Rights Reserved. DRAWING TANGENTS TO TWO CIRCLES AutoCAD software provides a convenient object snap for finding tangency.

54 Technical Drawing with Engineering Graphics, 14/e Giesecke, Hill, Spencer, Dygdon, Novak, Lockhart, Goodman © 2012, 2009, 2003, Pearson Higher Education, Upper Saddle River, NJ All Rights Reserved. DRAWING AN ARC TANGENT TO A LINE OR ARC AND THROUGH A POINT Tangents

55 Technical Drawing with Engineering Graphics, 14/e Giesecke, Hill, Spencer, Dygdon, Novak, Lockhart, Goodman © 2012, 2009, 2003, Pearson Higher Education, Upper Saddle River, NJ All Rights Reserved. DRAWING AN ARC TANGENT TO TWO LINES AT RIGHT ANGLES For small radii, such as 1/8R for fillets and rounds, it is not practicable to draw complete tangency constructions. Instead, draw a 45° bisector of the angle and locate the center of the arc by trial along this line

56 Technical Drawing with Engineering Graphics, 14/e Giesecke, Hill, Spencer, Dygdon, Novak, Lockhart, Goodman © 2012, 2009, 2003, Pearson Higher Education, Upper Saddle River, NJ All Rights Reserved. DRAWING AN ARC TANGENT TO TWO LINES AT ACUTE OR OBTUSE ANGLES

57 Technical Drawing with Engineering Graphics, 14/e Giesecke, Hill, Spencer, Dygdon, Novak, Lockhart, Goodman © 2012, 2009, 2003, Pearson Higher Education, Upper Saddle River, NJ All Rights Reserved. DRAWING AN ARC TANGENT TO AN ARC AND A STRAIGHT LINE

58 Technical Drawing with Engineering Graphics, 14/e Giesecke, Hill, Spencer, Dygdon, Novak, Lockhart, Goodman © 2012, 2009, 2003, Pearson Higher Education, Upper Saddle River, NJ All Rights Reserved. DRAWING AN ARC TANGENT TO TWO ARCS

59 Technical Drawing with Engineering Graphics, 14/e Giesecke, Hill, Spencer, Dygdon, Novak, Lockhart, Goodman © 2012, 2009, 2003, Pearson Higher Education, Upper Saddle River, NJ All Rights Reserved. DRAWING AN ARC TANGENT TO TWO ARCS AND ENCLOSING ONE OR BOTH

60 Technical Drawing with Engineering Graphics, 14/e Giesecke, Hill, Spencer, Dygdon, Novak, Lockhart, Goodman © 2012, 2009, 2003, Pearson Higher Education, Upper Saddle River, NJ All Rights Reserved. DRAWING AN OGEE CURVE Connecting Two Parallel LinesConnecting Two Nonparallel Lines

61 Technical Drawing with Engineering Graphics, 14/e Giesecke, Hill, Spencer, Dygdon, Novak, Lockhart, Goodman © 2012, 2009, 2003, Pearson Higher Education, Upper Saddle River, NJ All Rights Reserved. THE CONIC SECTIONS The conic sections are curves produced by planes intersecting a right circular cone. Four types of curves are produced: the circle, ellipse, parabola, and hyperbola, according to the position of the planes.

62 Technical Drawing with Engineering Graphics, 14/e Giesecke, Hill, Spencer, Dygdon, Novak, Lockhart, Goodman © 2012, 2009, 2003, Pearson Higher Education, Upper Saddle River, NJ All Rights Reserved. DRAWING A FOCI ELLIPSE

63 Technical Drawing with Engineering Graphics, 14/e Giesecke, Hill, Spencer, Dygdon, Novak, Lockhart, Goodman © 2012, 2009, 2003, Pearson Higher Education, Upper Saddle River, NJ All Rights Reserved. DRAWING A CONCENTRIC CIRCLE ELLIPSE If a circle is viewed with the line of sight perpendicular to the plane of the circle… …the circle will appear as a circle, in true size and shape

64 Technical Drawing with Engineering Graphics, 14/e Giesecke, Hill, Spencer, Dygdon, Novak, Lockhart, Goodman © 2012, 2009, 2003, Pearson Higher Education, Upper Saddle River, NJ All Rights Reserved. DRAWING A PARALLELOGRAM ELLIPSE The intersection of like-numbered lines will be points on the ellipse. Locate points in the remaining three quadrants in a similar manner. Sketch the ellipse lightly through the points, then darken the final ellipse with the aid of an irregular curve.

65 Technical Drawing with Engineering Graphics, 14/e Giesecke, Hill, Spencer, Dygdon, Novak, Lockhart, Goodman © 2012, 2009, 2003, Pearson Higher Education, Upper Saddle River, NJ All Rights Reserved. ELLIPSE TEMPLATES These ellipse guides are usually designated by the ellipse angle, the angle at which a circle is viewed to appear as an ellipse.

66 Technical Drawing with Engineering Graphics, 14/e Giesecke, Hill, Spencer, Dygdon, Novak, Lockhart, Goodman © 2012, 2009, 2003, Pearson Higher Education, Upper Saddle River, NJ All Rights Reserved. IRREGULAR CURVES The curves are largely successive segments of geometric curves, such as the ellipse, parabola, hyperbola, and involute.

67 Technical Drawing with Engineering Graphics, 14/e Giesecke, Hill, Spencer, Dygdon, Novak, Lockhart, Goodman © 2012, 2009, 2003, Pearson Higher Education, Upper Saddle River, NJ All Rights Reserved. DRAWING AN APPROXIMATE ELLIPSE For many purposes, particularly where a small ellipse is required, use the approximate circular arc method.

68 Technical Drawing with Engineering Graphics, 14/e Giesecke, Hill, Spencer, Dygdon, Novak, Lockhart, Goodman © 2012, 2009, 2003, Pearson Higher Education, Upper Saddle River, NJ All Rights Reserved. DRAWING A PARABOLA The curve of intersection between a right circular cone and a plane parallel to one of its elements is a parabola.

69 Technical Drawing with Engineering Graphics, 14/e Giesecke, Hill, Spencer, Dygdon, Novak, Lockhart, Goodman © 2012, 2009, 2003, Pearson Higher Education, Upper Saddle River, NJ All Rights Reserved. DRAWING A HELIX A helix is generated by a point moving around and along the surface of a cylinder or cone with a uniform angular velocity about the axis, and with a uniform linear velocity about the axis, and with a uniform velocity in the direction of the axis

70 Technical Drawing with Engineering Graphics, 14/e Giesecke, Hill, Spencer, Dygdon, Novak, Lockhart, Goodman © 2012, 2009, 2003, Pearson Higher Education, Upper Saddle River, NJ All Rights Reserved. DRAWING AN INVOLUTE An involute is the path of a point on a string as the string unwinds from a line, polygon, or circle.

71 Technical Drawing with Engineering Graphics, 14/e Giesecke, Hill, Spencer, Dygdon, Novak, Lockhart, Goodman © 2012, 2009, 2003, Pearson Higher Education, Upper Saddle River, NJ All Rights Reserved. DRAWING A CYCLOID A cycloid is generated by a point P on the circumference of a circle that rolls along a straight line Cycloid

72 Technical Drawing with Engineering Graphics, 14/e Giesecke, Hill, Spencer, Dygdon, Novak, Lockhart, Goodman © 2012, 2009, 2003, Pearson Higher Education, Upper Saddle River, NJ All Rights Reserved. DRAWING AN EPICYCLOID OR A HYPOCYCLOID Like cycloids, these curves are used to form the outlines of certain gear teeth and are therefore of practical importance in machine design.


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