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 convergeand
engineering108.com
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 projection Perspective projection
Plane of projection Plane of projection
engineering108.com
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
engineering108.com
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
51 2 3 4
engineering108.com
9. 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
engineering108.com
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
engineering108.com
11. Multiview Drawing
It represents accurate shape and size.Advantage
Disadvantage Require practice in writing and reading.
Multiviews drawing (2-view drawing)Example
engineering108.com
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
engineering108.com
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
engineering108.com
15.
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.)
engineering108.com
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..
engineering108.com
29. • Visible lines takes precedence over all other lines
• Hidden lines and cutting plane lines take precedence over
center lines
• Center lines have lowest precedence
Precedence of Lines
0.6 mm
0.3 mm
0.6 mm
engineering108.com
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
engineering108.com
32. Types of Dimensioning
• Parallel Dimensioning
• Parallel dimensioning consists of several dimensions
originating from one projection line.
engineering108.com
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.
engineering108.com
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.
engineering108.com
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.
engineering108.com
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
engineering108.com
38. Unidirectional System
values read from bottom only
(Preferred when?)
Aligned System
values read from bottom and
Right side
engineering108.com
45. Vision to spread knowledge
• Send interesting contents about particular subjects , articles on global stuffs,
engineering materials to us which will be helpful to your friends and others.
• We member of PROJECT FUNDA, provide a medium to make all this world wide
through your great support. We request you to join this project and make tutorial of
at least one chapter of your choice, that will help you to blow your name and your
knowledge over the world.
engineering108.com
46. Thank You
For more tutorials on engineering subjects visit is at engineering108.com
engineering108.com