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### Dimensioning

1. Table of Contents • Copy a Segment • Copy an Angle • Bisect a Segment (Perpendicular Bisector) • Bisect an Angle
2. Copy a Segment A B 1) Since a segment is a part of a line, we’ll start by drawing a ray that is somewhat longer than our intended segment, and call the starting point A’. A’ 2) Place the Needle end of the compass on point A, and adjust its length to match the distance AB. 3) Without changing the width of the compass, put the Needle end of the compass on point A’, and draw the arc to cross your ray. Label the point of intersection B’. You’ve just copied AB to A’B’ B’
3. Copy An Angle A B 1) Since an angle is two rays with a common vertex we’ll start by drawing a ray and call ray B’A’. A’ 2) Place the Needle end of the compass on point B, and make an arc that crosses over from BA to BC. 3) Without changing the width of the compass, put the Needle end of the compass on point B’, and draw the arc crossing B’A’ long enough to more than cross where B’C’ will be. B’ C4) Now go back to the original angle, and put your needle on the point of intersection of AB and the arc. Measure the distance along the arc to the ray BC. 5) Without changing the width of the compass, put your needle on the point of intersection of the arc and B’A’. Make an arc that crosses the first arc you drew on this new angle. 6) Draw a ray from B’ thru the point of intersection of the two arcs. Label a point on the ray as C’. You’ve copied the angle ABC as A’B’C’. C’
4. Bisecting a Segment A B 1) Place the needle of your compass on A. Make its width more than half-way to B, and make a half-circle. 2) Without changing the width of the compass, put the needle of your compass on B. Make a half-circle that overlaps the first one. 3) Draw a line that connects the two points of intersection of the two half-circles. That new line is both a bisector of the segment AB, and is perpendicular to AB. 4) Leave your construction marks to show your work, and draw additional marks to indicate both perpendicular AND bisector.
5. Bisecting an Angle A B 1) Place the needle of your compass on B. Draw an arc that crosses both BA and BC. 3) Place the needle of the compass on D, and set the width to match more than half the distance to E. Make a half-circle. 5) Draw a line that connects the two points of intersection of the two half-circles. That new line is both a bisector of the angle ABC. C D E 2) Label the intersection of the arc and BA “D”, and the intersection of the arc and BC “E”. 4) Leave the compass width as it is. Place the needle of the compass on E, and make a half-circle overlapping the previous half-circle.
6. Introduction Standards are set of rules that govern how technical drawings are represented. Drawing standards are used so that drawings convey the same meaning to everyone who reads them.
7. ISO International Standards Organization Standard Code ANSI American National Standard InstituteUSA JIS Japanese Industrial StandardJapan BS British StandardUK AS Australian StandardAustralia Deutsches Institut für NormungDINGermany Country Code Full name TS Turkish StandardTurkey
8. Drawing Sheet Trimmed paper of a size A0 ~ A4. Standard sheet size (ISO) A4 210 x 297 A3 297 x 420 A2 420 x 594 A1 594 x 841 A0 841 x 1189 A4 A3 A2 A1 A0(Dimensions in millimeters)
9. Drawing space Drawing space Title block d d c c c Border lines 1. Type X (A0~A4) 2. Type Y (A4 only) Orientation of drawing sheet Title block Sheet size c (min) d (min) A4 10 25 A3 10 25 A2 10 25 A1 20 25 A0 20 25
10. Drawing Scales Scale is the ratio of the linear dimension of an element of an object shown in the drawing to the real linear dimension of the same element of the object. Size in drawing Actual size Length, size :
11. Scale • Scales are used to measure distances on technical drawings. • Types of scales – Mechanical Engineers Scale (Fractional divisions) – Civil Engineer’s Scale (Division of 10) – Metric Scale – Architectural Scale (Fractional divisions) – Combination Scale
12. Mechanical Engineer’s Scale • Mechanical Drawings are drawn in inches. • 16 Divisions per inch • Scales – 1:1 Full Size – 1:2 Half Size – 1:4 Quarter Size – 1:8 One Eight Size
13. Civil Engineer’s Scale • Civil Drawings are drawn in feet as the base unit. • Scales commonly used – 1”:10’ 1”:100’ – 1”:20’ 1”:200’ – 1”:30’ 1”:300’ – 1”:40’ 1”:400’ – 1”:50’ 1”:500’ – 1”:60’ 1”:600’
14. Metric Scale • Metric Mechanical Drawings are drawn in inches. • Metric Civil Drawings are drawn in meters. • Scale – 1:1 Full Size – 1:2 Half Size – 1:5 Fifth Size – 1:10 Tenth Size
15. Drawing Scale • We use scale in drawing to represent objects in the appropriate size on our drawing sheet. – We can represent large objects on a B-Size sheet using scale. (1” = 50’) – We can represent small objects on B-Size Sheet using scale. (4:1) • What are some examples that you might want to represent in a drawing?
16. Hidden Lines • Dashed lines, lighter (thinner) than object lines. • Used in orthographic projection views to represent edges that are “hidden” from the line of sight for a view. • Not used in isometric or oblique views.
17. Line Convention
18. Basic Line Types Types of Lines Appearance Name according to application Continuous thick line Visible line Continuous thin line Dimension line Extension line Leader line Dash thick line Hidden line Chain thin line Center line NOTE : We will learn other types of line in later chapters.
19. Visible lines represent features that can be seen in the current view Meaning of Lines Hidden lines represent features that can not be seen in the current view Center line represents symmetry, path of motion, centers of circles, axis of axisymmetrical parts Dimension and Extension lines indicate the sizes and location of features on a drawing
20. LINE CONVENTION Precedence of coincide lines. Hidden line drawing. Center line drawing.
21. PRECEDENCE OF LINE Visible line Order of importance Hidden line Center line
22. Hidden arcs should start on a center line. HIDDEN LINE PRACTICE
23. HIDDEN LINE PRACTICE Hidden line should join a visible line, except it extended from the visible line. Correct No ! Join Leave space
24. Correct No ! Hidden line should join a visible line, except it extended from the visible line. Leave space Leave space HIDDEN LINE PRACTICE
25. Hidden line should intersect to form L and T corners. Correct No ! L T HIDDEN LINE PRACTICE
26. CENTER LINE PRACTICE In circular view, short dash should cross at the intersections of center line. For small hole, center line is presented as thin continuous line. Center line should not extend between views. Leave space Leave space
27. Leave the gap when centerline forms a continuation with a visible or hidden line Leave space Leave space Leave space Leave space Center line should always start and end with long dash. CENTER LINE PRACTICE
28. Centerlines Locate the center of circles and the axis of cylindrical features.
29. Example : Line conventions in engineering drawing
30. PROJECTION METHOD
31. PROJECTION METHOD Perspective Oblique Orthographic Axonometric Multiview Parallel
32. Types of Projection
33. Types of Projection
34. PROJECTION THEORY The projection theory is based on two variables: 1) Line of sight 2) Plane of projection (image plane or picture plane) The projection theory is used to graphically represent 3-D objects on 2-D media (paper, computer screen).
35. Line of sight is an imaginary ray of light between an observer’s eye and an object. Line of sight Parallel projection Line of sight Perspective projection There are 2 types of LOS : parallel convergeand
36. Plane of projection is an imaginary flat plane which the image is created. The image is produced by connecting the points where the LOS pierce the projection plane. Parallel projection Perspective projection Plane of projection Plane of projection
37. Orthographic Projection
38. 5 Orthographic projection is a parallel projection technique in which the parallel lines of sight are perpendicular to the projection plane MEANING Object views from top Projection plane 1 2 3 4 51 2 3 4
39. ORTHOGRAPHIC VIEW Orthographic view depends on relative position of the object to the line of sight. Two dimensions of an object is shown. Three dimensions of an object is shown. Rotate Tilt More than one view is needed to represent the object. Multiview drawing Axonometric drawing
40. Orthographic projection technique can produce either 1. Multiview drawing that each view show an object in two dimensions. 2. Axonometric drawing that show all three dimensions of an object in one view. Both drawing types are used in technical drawing for communication. NOTES ORTHOGRAPHIC VIEW
41. Axonometric (Isometric) Drawing Easy to understand Right angle becomes obtuse angle. Circular hole becomes ellipse. Distortions of shape and size in isometric drawing Advantage Disadvantage Shape and angle distortion Example
42. Multiview Drawing It represents accurate shape and size.Advantage Disadvantage Require practice in writing and reading. Multiviews drawing (2-view drawing)Example
43. Perspective Projection • Perspective – The most realistic of the pictorial drawing styles because it is closest to the way that we see. – An ordinary photograph shows the view in perspective. • We will not cover this view in this class. – You can study it on you own. See Chapter 16 in you text. – A drawing class would be another option.
44. Types of Parallel Projection • Orthographic projections are a type of parallel projection – Orthographic (right angle) projections have parallel projectors that are perpendicular (90 degrees) to the plane of projection – In orthographic projection objects can be presented at true size or scaled at a proportion of their true size
45. Types of Orthographic Projection • Multiview projection – A two dimensional representation of a three dimensional object. – It shows one or more necessary views of an object • Front, Rear, Top, Bottom, Right or Left
46. MULTIVIEW PROJECTION Three principle dimensions of an object … Width Depth Height Width Height Depth Depth … can be presented only two in each view. Adjacent view(s) is needed to fulfill the size description.
47. 1. Revolve the object with respect to observer. TO OBTAIN MULTIVIEW REPRESENTATION OF AN OBJECT 2. The observer move around the object.
48. Multi-view drawing
49. Multiview Drawings First- and Third-Angle Projection • There are two main systems used for projecting and unfolding the views: – Third-angle projection which is used in the United States, Canada and some other countries – First-angle projection which is primarily used in Europe and Asia • You should understand both methods
50. • Controls the placement of views • Depicted on drawings by the truncated cone symbol • Third Angle • United States and Great Britain • Top view - above front view. • Right side - right of front view • Same as “Glass box” unfolding • First Angle • Rest of world • Top view - below front view. • Right side - left of front view • We will only use third-angle projections in EF101 Projection Types
51. Multiview Drawings Third-angle Projection
52. Multiview Drawings First-angle Projection
53. Isometric Drawings
54. Glass Box
55. Unfolding Glass Box
56. View Relationships
57. OBSERVER MOVE AROUND Front view Right side view Top view
58. THE GLASS BOX CONCEPT Bottom view Left side view Rear view
59. Height Width Depth History
60. Orthographic Projection of Object Features
61. A B PROJECTION OF POINT(S) AF BR AT BF AR BT AF AR AT BF BR BT Equal distance
62. A B AF BF BRAR AT BT BR AR AF BF AT BT True length NORMAL LINE True lengthPoint Equal length PROJECTION OF LINE
63. A B AF BF BRAR AT BT INCLINED LINE Foreshortened BR AR AF BF Foreshortened AT BT True length A Equal length PROJECTION OF LINE
64. A B AF BF BR AR AT BT OBLIQUED LINE A Equal length B Foreshortened Foreshortened Foreshortened BR AR AF BF AT BT PROJECTION OF LINE
65. B C A PROJECTION OF PLANE BF AF,CF CRAR,BR AT CT NORMAL PLANE Equal length Edge Edge True size CR AR,BR AF,CF BF AT BT CT BT
66. B C BF AF CR AR,BR AT CT INCLINED PLANE A Equal length BT C CF Edge CR AR,BR Foreshortened BT CT AT AF CF Foreshortened BF PROJECTION OF PLANE
67. B C BF AF CR AR AT CT OBLIQUED PLANE A Equal length BT C CF B BR Foreshortened CR AR BR AF BF CF Foreshortened AT BT CT Foreshortened PROJECTION OF PLANE
68. PROJECTION OF OBJECT The views are obtained by projecting all object features to the picture plane. You have to project the remaining surfaces which are invisible too !
69. s s s PROJECTION OF OBJECT
70. Freehand Sketching
71. Straight Line 1. Hold the pencil naturally. 2. Spot the beginning and end points. 3. Swing the pencil back and forth between the points, barely touching the paper until the direction is clearly established. 4. Draw the line firmly with a free and easy wrist-and-arm motion
72. Horizontal line Vertical line
73. Nearly vertical inclined line Nearly horizontal inclined line
74. Small Circle Method 1 : Starting with a square 1. Lightly sketching the square and marking the mid-points. 2. Draw light diagonals and mark the estimated radius. 3. Draw the circle through the eight points. Step 1 Step 2 Step 3
75. Method 2 : Starting with center line Step 1 Step 2 Step 3 1. Lightly draw a center line. 2. Add light radial lines and mark the estimated radius. 3. Sketch the full circle. Small Circle
76. 1. Place the little finger (or pencil’ s tip) at the center as a pivot, and set the pencil point at the radius-distance from the center. 2. Hold the hand in this position and rotate the paper. Large Circle
77. Arc Method 1 : Starting with a square Method 2 : Starting with a center line
78. Steps in Sketching 1. Block in main shape. 2. Locate the features. 3. Sketch arcs and circles. 4. Sketch lines.
79. Example
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