Introduction to Engineering Graphics Basics

GE4106-ENGINEERING GRAPHICS
Dr. S. PRATHAP SINGH
Assistant Professor
Department of Mechanical Engineering
OBJECTIVE
 To develop in students, graphic skills for communication of concepts, ideas and design of Engineering
products
 To expose them to existing national standards related to technical drawings.
CONCEPTS AND CONVENTIONS (Not for Examination)
UNIT 1 Plane Curves and Freehand Sketching
UNIT 2 Projection of Points, Lines and Plane Surface
UNIT 3 Projection of Solids
UNIT 4 Projection of Sectioned Solids and Development of surfaces
UNIT 5 Isometric and Perspective Projections

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DRAWINGS
(A Graphical Representation)
 The art of representation of an object by systematic lines on a paper is called Drawing.
Classification of Drawing
Artistic Drawing Engineering Drawing
 Free hand or Model Drawing
 To communicate ideas, moods, or styles in a visually
appealing
 No strict rules for scale, projection, or dimensioning.
(Expressive, imaginative, not bound by standards) (Exact, measurable, standard-based)
 A technical language of lines, symbols, and notations
used to convey the shape, size, features, and
specifications of an object accurately and
unambiguously.

ENGINEERING DRAWING
 “The universal language of engineers” – a way to communicate ideas, designs, and technical information
through drawings and symbols.
Why is it Important?
 Converts concepts into visual form.
 Ensures clear communication between engineers, manufacturers, and builders.
 Reduces errors in design and production.
"If you can draw it, you can build it."
Key Characteristics:
 Accuracy – follows exact dimensions and tolerances.
 Standards-based – uses conventions like ISO, BIS, or ASME.
 Scalable – can be drawn full-size, reduced, or enlarged with proper scale notation.
 Clear & Unambiguous – readable by anyone trained in engineering drawing.

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APPLICATIONS OF ENGINEERING DRAWING
Manufacturing & Production
Machine part fabrication Assembly instructions Tool and die design
Civil & Structural Engineering
Building construction Infrastructure projects Site layout planning

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APPLICATIONS OF ENGINEERING DRAWING
Electrical & Electronics Engineering
Circuit diagrams Control panel layouts Product enclosures
Research & Prototyping
Concept visualization
Reverse engineering
Drawings communicate new designs to stakeholders before fabrication.
Engineers create drawings from existing parts for replication or improvement.

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DRAWING INSTRUMENTS
DRAWING SHEETS
 Drawing sheets are made up of thick paper with smooth surface and are available in standard sizes.
Designation Trimmed size (mm)
A0 841 x 1189
A1 594 x 841
A2 420 x 594
A3 297 x 420
A4 210 x 297
 Title block is a rectangular block.
 It is an important feature of
drawing.
 It should be placed in the bottom
right corner of the drawing sheet.

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DRAWING INSTRUMENTS
DRAWING BOARD
 Drawing board is usually of rectangular shape.
 It is generally of well-seasoned soft wood.
1. Standard Sizes (IS 1444:1989)
920 mm x 650 mm
650 mm x 470 mm
500 mm x 350 mm
2. Thickness – 22 mm

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DRAWING INSTRUMENTS
MINI DRAFTER
 A drafting machine is used by a professional draftsman to prepare drawings.
 A miniature version of the drafting machine is known as “Mini-drafter”.
 It combines the functions of T-Square, Set-Squares, Scales, Protractor, and Clinograph.
Clamping screw
Double Parallel Bars
Right angled scales
Knob

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DRAWING INSTRUMENTS
MINI DRAFTER
 Set the reference mark on the protractor head to read 0 and tighten the knob.
 Clamp the drafter to the left-side top edge of the drawing board, such that the horizontal scale is parallel to the
horizontal edge of the drawing sheet.
 Now, one can draw horizontal and vertical lines.
 To draw inclined lines, the scale should be indexed to the required angle.

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DRAWING INSTRUMENTS
INSTRUMENT BOX
 Large compass – to draw circles from 30 mm to 120 mm diameter
 Lengthening bar – attachment used to draw circles of more than 125 mm.
 Small Bow compass – to draw circle of diameter up to 30 mm.
 Dividers (Large and small) – transferring dimensions and dividing lines or curves into number of equal parts.

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DRAWING INSTRUMENTS
SET SQUARES & PROTRACTOR CUM PROCIRCLE

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DRAWING INSTRUMENTS
DRAWING PENCILS
 Accuracy and appearance of a drawing depends on the quality of pencil.
 The grade of a pencil lead is marked on the pencil.
HB denotes medium grade.
Increase in hardness is shown by value put in front of H such as 2H, 3H etc.,
Softer pencils are marked as 2B, 3B, 4B etc.
Beginning of a drawing may be made with H or 2H.
For lettering and dimensioning, H and HB pencils are used.
HB – Border lines, free hand sketching, title block, arrow heads,
lettering, object lines and numbering.
H – Finishing lines, outlines, visible lines and hidden/invisible lines.
2H – Construction lines, dimension lines, section lines and Centre
lines.

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DRAWING INSTRUMENTS
OTHER INSTRUMENTS
 Drawing clips & Adhesive tape
 Sharpener  Eraser
 French curves

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DRAWING STANDARDS
SCALES
 If the actual linear dimensions of an object are shown in its drawing,
the scale used is said to be full size scale.
 Very big objects can not be represented in its drawing to their full
size.
 A reducing scale of 1:10 means that 10 units length on the object is
represented by 1 unit length on the drawing.
 On the other hand, enlarging scale (Eg. 10:1) is used to represent
smaller objects in their drawings.
 For all drawings, scale used must be mentioned.
SCALE 1:1 Full size
SCALE X:1 Enlargement scales (X > 1)
SCALE 1:X Reduction scales (X > 1)

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DRAWING STANDARDS
LINES
 IS 10714 (Part 20) : 2001& SP 46 : 2003
 The details of the various objects are drawn by different line types.
 Each line in a drawing has a meaning and sense to convey.
Line Type Applications
Continuous wide line Visible edges, visible outlines, main representations in
a diagram.
Continuous narrow line Dimension lines, extension lines, Leader lines,
Reference lines, Projection lines, hatching,
Construction/guide lines, imaginary lines.
Dashed narrow line
Hidden lines, hidden edges, hidden outlines.
Long-dashed dotted line
Centre lines, axes, lines of symmetry. Cutting planes.

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DRAWING STANDARDS
LINES
Line Type Applications
Visible lines
To represent features that can be seen in
the current view
Hidden lines
To represent features that can not be seen
in the current view
Center line
To represents symmetry, path of motion,
centers of circles, axis of axisymmetrical
parts
Dimension and
Extension lines
To indicate the sizes and location of
features on a drawing

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DRAWING STANDARDS
LETTERING
 Lettering is defined as writing of titles, sub-titles, dimensions, etc.
 Use of drawing instruments for lettering consumes more time.
 Hence, Lettering should be done freehand with speed.
 BIS and ISO Conventions - IS9609 (Part 0) : 2001 and SP 46 : 2003
 Lettering in a drawing should use upper-case (CAPITALS).
 Lower-case letters are used in writing the abbreviations like mm, etc.
 Size of letters – height of the capital letters and numerals.

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DRAWING STANDARDS
DIMENSIONING
 Expression of size features on a drawing using lines, symbol, figures, notes, etc. is called dimensioning.

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DRAWING STANDARDS
PRINCIPLES OF DIMENSIONING
 All necessary dimensions required to describe a component clearly and completely shall be written in
drawings directly.
 Each feature shall be dimensioned only once in a drawing, i.e. dimensions marked in one view need not be
repeated in another view.
 Dimension should be placed on the view where the shape is best seen.

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DRAWING STANDARDS
 Dimensions should be expressed in one unit only (preferably in mm) without showing the unit symbol.
 As far as possible, dimensions should be placed outside the view.
 Dimensions should be taken from visible outlines rather than from hidden lines.
 No gap should be left between the feature and the start of the extension line.

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DRAWING STANDARDS
 Crossing of centre lines should be done by a long dash and not a short dash.

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DRAWING STANDARDS
ARRANGEMENT OF DIMENSION

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UNIT 1 PLANE CURVES AND FREEHAND SKETCHING
Basic Geometrical constructions, Curves used in engineering practices: Conics – Construction of ellipse, parabola
and hyperbola by eccentricity method – Construction of cycloid – construction of involutes of square and circle –
Drawing of tangents and normal to the above curves. Visualization concepts and Free Hand sketching: Visualization
principles –Representation of Three-Dimensional objects – Layout of views- Freehand sketching of multiple views
from pictorial views of objects
 Construction of ellipse by eccentricity method
 Construction of parabola by eccentricity method
 Construction of hyperbola by eccentricity method
 Construction of cycloid
 Construction of epicycloid
 Construction of hypocycloid
 Construction of involutes of square and circle
 Freehand sketching
Drawing of tangents and normal to the curves

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UNIT 1 PLANE CURVES AND FREEHAND SKETCHING
CONICS

Introduction to Engineering Graphics Basics

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