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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 AB 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 AB 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 setof 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 StandardsOrganization 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 paperof 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 Titleblock 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 isthe 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 areused 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 • MetricMechanical 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 • Weuse 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 • Dashedlines, 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.
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- 18. Basic Line Types Typesof 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.
- 20. Visible lines representfeatures 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
- 21. LINE CONVENTION Precedence ofcoincide lines. Hidden line drawing. Center line drawing.
- 22. PRECEDENCE OF LINE Visible line Orderof importance Hidden line Center line
- 23. Hidden arcs shouldstart on a center line. HIDDEN LINE PRACTICE
- 24. HIDDEN LINE PRACTICE Hiddenline should join a visible line, except it extended from the visible line. Correct No ! Join Leave space
- 25. Correct No ! Hiddenline should join a visible line, except it extended from the visible line. Leave space Leave space HIDDEN LINE PRACTICE
- 26. Hidden line shouldintersect to form L and T corners. Correct No ! L T HIDDEN LINE PRACTICE
- 27. CENTER LINE PRACTICE Incircular 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
- 28. Leave the gapwhen 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
- 29. Centerlines Locate the centerof circles and the axis of cylindrical features.
- 30. Example : Lineconventions in engineering drawing
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- 32. PROJECTION METHOD Perspective Oblique Orthographic AxonometricMultiview Parallel
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- 35. PROJECTION THEORY The projectiontheory 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).
- 36. Line of sightis 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
- 37. Plane of projectionis 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
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- 39. 5 Orthographic projection isa 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
- 40. ORTHOGRAPHIC VIEW Orthographic viewdepends 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
- 41. Orthographic projection techniquecan 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
- 42. Axonometric (Isometric) Drawing Easyto 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
- 43. Multiview Drawing It representsaccurate shape and size.Advantage Disadvantage Require practice in writing and reading. Multiviews drawing (2-view drawing)Example
- 44. 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.
- 45. Types of ParallelProjection • 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
- 46. Types of OrthographicProjection • 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
- 47. MULTIVIEW PROJECTION Three principledimensions 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.
- 48. 1. Revolve theobject with respect to observer. TO OBTAIN MULTIVIEW REPRESENTATION OF AN OBJECT 2. The observer move around the object.
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- 51. Multiview Drawings First- andThird-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
- 52. • Controls theplacement 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
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- 59. OBSERVER MOVE AROUND Frontview Right side view Top view
- 60. THE GLASS BOXCONCEPT Bottom view Left side view Rear view
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- 63. A B PROJECTION OF POINT(S) AF BR AT BF AR BT AFAR AT BF BR BT Equal distance
- 64. A B AF BF BRAR AT BT BR AR AFBF AT BT True length NORMAL LINE True lengthPoint Equal length PROJECTION OF LINE
- 65. A B AF BF BRAR AT BT INCLINEDLINE Foreshortened BR AR AF BF Foreshortened AT BT True length A Equal length PROJECTION OF LINE
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- 67. B C A PROJECTION OF PLANE BFAF,CF CRAR,BR AT CT NORMAL PLANE Equal length Edge Edge True size CR AR,BR AF,CF BF AT BT CT BT
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- 70. PROJECTION OF OBJECT Theviews are obtained by projecting all object features to the picture plane. You have to project the remaining surfaces which are invisible too !
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- 73. Straight Line 1. Holdthe 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
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- 75. Nearly vertical inclined line Nearlyhorizontal inclined line
- 76. 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
- 77. 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
- 78. 1. Place thelittle 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
- 79. Arc Method 1 :Starting with a square Method 2 : Starting with a center line
- 80. Steps in Sketching 1.Block in main shape. 2. Locate the features. 3. Sketch arcs and circles. 4. Sketch lines.
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