4. 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 converge and

5. 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 projectionPerspective projection Plane of projection

6. Disadvantage of Perspective Projection Perspective projection is not used by engineer for manu- facturing of parts, because 1) It is difficult to create. 2) It does not reveal exact shape and size. Width is distorted

8. 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 4 512 34

9. 1. Multiview drawing Orthographic projection technique can produce either 1. Multiview drawing that each view show an object in two dimensions. 2. Axonometric drawing 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

10. 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

11. Multiview Drawing It represents accurate shape and size. Advantage Disadvantage Require practice in writing and reading. Multiviews drawing (2-view drawing) Example

12. ORTHOGRAPHIC PROJECTIONS : Horizontal Plane (HP), Vertical Frontal Plane ( VP ) Side Or Profile Plane ( PP) Different Reference planes are FV is a view projected on VP. TV is a view projected on HP. SV is a view projected on PP. And Different Views are Front View (FV), Top View (TV) and Side View (SV) IT IS A TECHNICAL DRAWING IN WHICH DIFFERENT VIEWS OF AN OBJECT ARE PROJECTED ON DIFFERENT REFERENCE PLANES OBSERVING PERPENDICULAR TO RESPECTIVE REFERENCE PLANE

14. Orthographic Projections are a collection of 2-D drawings that work together to give an accurate overall representation of an object. Defining the Six Principal Views or Orthographic Views

15.  A.I.P.  to Vp &  to Hp  A.V.P.  to Hp &  to Vp PLANES PRINCIPAL PLANES HP AND VP AUXILIARY PLANES Auxiliary Vertical Plane (A.V.P.) Profile Plane ( P.P.) Auxiliary Inclined Plane (A.I.P.)

16. Object PICTURE PLANE Observer

20. Glass Box Approach

26. Third-angle Projection First-angle Projection First and Third Angle Projections  First Angle  Third Angle

27. Conventional Orthographic Views Height Depth Width Front View Top View/Plan Right Side View

28. Lines on an engineering drawing signify more than just the geometry of the object and it is important that the appropriate line type is used. Line Thickness For most engineering drawings you will require two thickness', a thick and thin line. The general recommendation are that thick lines are twice as thick as thin lines. A thick continuous line is used for visible edges and outlines. A thin line is used for hatching, leader lines, short centre lines, dimensions and projections. Line Styles Other line styles used to clarify important features on drawings are: Thin chain lines are a common feature on engineering drawings used to indicate centre lines. Centre lines are used to identify the centre of a circle, cylindrical features, or a line of symmetry. Dashed lines are used to show important hidden detail for example wall thickness and holes..

29. Precedence of Lines  Visible lines takes precedence over all other lines  Hidden lines and cutting plane lines take precedence over center lines  Center lines have lowest precedence 0.6 mm 0.3 mm 0.6 mm

30. For Example: 1. Visible 2. Hidden 3. Center

31. Dimensioning A dimensioned drawing should provide all the information necessary for a finished product or part to be manufactured. An example dimension is shown below. Dimensions are always drawn using continuous thin lines. Two projection lines indicate where the dimension starts and finishes. Projection lines do not touch the object and are drawn perpendicular to the element you are dimensioning. All dimensions less than 1 should have a leading zero. i.e..35 should be written as 0.35

32. Types of Dimensioning  Parallel Dimensioning  Parallel dimensioning consists of several dimensions originating from one projection line.

33. Superimposed Running Dimensions Superimposed running dimensioning simplifies parallel dimensions in order to reduce the space used on a drawing. The common origin for the dimension lines is indicated by a small circle at the intersection of the first dimension and the projection line.

34. Chain Dimensioning Combined Dimensions A combined dimension uses both chain and parallel dimensioning.

35. Dimensioning of circles  (a) shows two common methods of dimensioning a circle. One method dimensions the circle between two lines projected from two diametrically opposite points. The second method dimensions the circle internally.  (b) is used when the circle is too small for the dimension to be easily read if it was placed inside the circle.

36. Dimensioning Radii  All radial dimensions are proceeded by the capital R. (a)shows a radius dimensioned with the centre of the radius located on the drawing. (b) shows how to dimension radii which do not need their centres locating.

37. Tolerancing  It is not possible in practice to manufacture products to the exact figures displayed on an engineering drawing. The accuracy depends largely on the manufacturing process. A tolerance value shows the manufacturing department the maximum permissible variation from the dimension.  Each dimension on a drawing must include a tolerance value. This can appear either as:  a general tolerance value applicable to several dimensions. i.e. a note specifying that the General Tolerance +/- 0.5 mm.  or a tolerance specific to that dimension

38. Unidirectional System values read from bottom only (Preferred when?) Aligned System values read from bottom and Right side

39. CORRECTINCORRECT

40. Dimensioning a circular arc.

42. Omit unnecessary dimensions.

43. Use of enlarged view to clarify dimensions.

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