Engineering Drawing

What is an Engineering Drawing ?

“An Engineering Drawing is a technical (not artistic) drawing which

clearly defines and communicates a design to other interested parties.
Other parties may have an interest in design collaboration,
procurement / purchasing, costing, manufacturing, quality control,
marketing, handling / packaging.”
Drawing:
• The way of conveying the ideas through the systematic lines on the
paper.
• The art of representation of an object by systematic lines on a paper.
Classification:
1. ArtisticDrawing(Free-handorModelDrawing):
The art of representation of an object by the artist by his imagination or
by keeping the object before him.
e.g. paintings, cinema posters, advertisement boards, etc.
2. EngineeringDrawing(InstrumentDrawing):
The art of representation of engineering objects.
e.g. buildings, roads, machines, etc.
 Artistic Drawing

The art of representation of an object by the artist by his imagination or by

keeping the object before him.

e.g. paintings, cinema posters, advertisement boards, etc.

 Typesof Engineering Drawing:
i. Geometrical Drawing:
e.g. geometrical objects - rectangle, square, cube, cone, cylinder, etc.
a. Plain Geometrical Drawing:
Two dimensional drawing having only length and breadth. e.g. square, triangle, etc.
b. Solid Geometrical Drawing:
Three dimensional drawing having length, breadth and thickness. e.g. cube, prism,
etc.
ii. MechanicalEngineeringorMachine Drawing:
e.g. mechanical engineering objects – machines, machine parts, etc.

iii. CivilEngineeringDrawing:
e.g. civil engineering objects – roads, buildings, bridges, dams, etc.

iv. Electrical &ElectronicsEngineeringDrawing:

e.g. electrical and electronics objects – transformers, wiring diagrams.
 Engineering Drawing

The art of representation of engineering objects.

e.g. buildings, roads, machines, etc.
Role of Graphics

• Visualization
• Communication
• Documentation
Applications of Engineering Drawing
Ships
Applications of Engineering Drawing
Manufacturing of Automobiles
Applications of Engineering Drawing
Construction
 Effectiveness of Engineering Drawing
1. Try to write a description of
this object.
2. Test your written description
by having someone attempt
to make a sketch from your
description.

You can easily understand that …

The word languages are inadequate for describing the size, shape and
features completely as well as concisely.
 Composition of ED Language
Graphic language in “engineering application” use lines to represent
the surfaces, edges and contours of objects.

The language is known as “drawing” or “drafting” .

A drawing can be done using freehand, instruments or computer

methods.
Freehand drawing
The lines are sketched without using instruments other than pencils and
erasers.

Example
Instrument drawing
Instruments are used to draw straight lines, circles, and curves concisely
and accurately. Thus, the drawings are usually made to scale.

Example
 Computer drawing
The drawings are usually made by CAD software such as FreeCAD,
AutoCAD, solid works , CATIA, PRO – E, etc.

Examples
Example of CAD
Example of CAD
Example of CAD
Example of CAD
 Simple CAD/CAE/CAM Product Lifecycle

Design Analysis Manufacturing

CAD CAE CAM
 Elements of Engineering Drawing
Engineering drawing are made up of graphics language and word
language.

Graphics Describe a shape

language (mainly).

Word Describe size, location

and
language
specification of the
object.
 Basic Knowledge for Drafting

Graphics Word
language language

Line Projection Geometric

types method construction Lettering
Traditional Drawing
Tools
 Drawing Instruments

1. Drawing Board 12. Drawing Pencils – H, 2H, HB

2. Drawing Sheet 13. Sand Paper
3. Drawing Sheet Holder 14. Eraser (Rubber)
4. Set-squares – 45o and 30o – 60o 15. Drawing Pins and Clips
5. Large size Compass 16. Cello Tape
6. Small bow Compass 17. Duster or Handkerchief
7. Large size Divider 18. Drafting Machine / Mini Drafter
8. Small bow Divider 19. Sketch Book (Medium size)
9. Scales – 6” and 12” 20. Roller Scale
10. Protractor 21. Pencil Sharpener
11. French Curve 22. Sheet Folder
TECHNICAL DRAWING BOARD
 DRAWING TOOLS

1. T-Square 2. Triangles
 DRAWING TOOLS

2H or HB for thick line

4H for thin line

3. Adhesive Tape 4. Pencils

 DRAWING TOOLS

5. Pencil Eraser 6. Compass

 DRAWING TOOLS

9. Circle Template 10. Tissue paper

 DRAWING TOOLS

11. Sharpener 12. Clean paper

 Layout of Drawing Sheet

15
150

Title Block

50

15
25 15

All the dimensions are in millimeters.

SAMPLE OF DRAWING SHEET
SAMPLE OF ENGINEERING DRAWING
 Title Block (Sample)

NAME: PUNJAB ENGINEERING

10

COLLEGE

20
SID:
10

BRANCH: LINES
10

10
SHEET NO.: & CHECKED BY:
10

10
DATE: LETTERING
10

10
50 50 50

NOTES:
All the dimensions are in millimeters.
Sheet Size
 LINES
Line Thickness:
Thickness varied according to the use of pen or pencil and the size & type of the drawing.
For pencil, the lines can be divided into two line-groups:

Line-group
Thickness Lines
(mm)
0.2 Medium Out lines, dotted lines, cutting plane lines

0.1 Thin Centre lines, section lines, dimension lines, extension lines,
construction lines, leader lines, short-break lines and long-break
lines.

Important Notes:
In the finished drawing, all lines except construction lines should be dense, clean and uniform.
Construction lines should be drawn very thin and faint and should be hardly visible.
 Types of Lines
Lines Description General Applications
A Continuous thick A1 Visible outlines
A2 Visible edges
B Continuous thin B1 Imaginary lines of intersection
(straight / curve) B2 Dimension lines
B3 Projection lines
B4 Leader lines
B5 Hatching or section lines
B6 Outlines of revolved sections in plane
B7 Short centre lines
C Continuous thin C1 Limits of partial or interrupted views and
(free-hand) sections
C2 Short-break lines
D Continuous thin D1 Long-break lines
(straight with zigzags)
 Lines Description General Applications
E Dashed thick E1 Hidden outlines
E2 Hidden edges
F Dashed thin F1 Hidden outlines
F2 Hidden edges
G Chain thin G1 Centre lines
G2 Lines of symmetry
G3 Trajectories
H Chain thin, thick at ends H1 Cutting planes
and changes of direction

J Chain thick J1 Indication of lines or surfaces to which a

special treatment applies
K Chain thin double-dashed K1 Outlines of adjacent parts
K2 Alternative and extreme positions of
movable parts
K3 Centroidal lines
 G1
H1 G3

P P

E1
80o

K2
A1 90
J1
B2 B4
B5
Ø10

C1
D1

Application of various types of lines according to B.I.S.

 Lettering
Writing of titles, dimensions, notes and other important particulars on a drawing is lettering
Classification:
1. Single-stroke Letters:
The thickness of the line of the letter is obtained in one stroke of the pencil.
Recommended by B.I.S.
It has two types:
i. Vertical
ii. Inclined (slope 75o with the horizontal)
• The ratio of height to width varies but in most of the cases it is 6:5.
• Lettering is generally done in capital letters.
• The lower-case letters are generally used in architectural drawings.
• The spacing between two letters should not be necessarily equal.
• The letters should be so placed that they do not appear too close together
too much apart.
• The distance between the words must be uniform and at least equal to
the height of the letters.
• Lettering, except the dimension figures, should be underlined to make
them more prominent.
Size of Alphabets for Drawing:
Main titles -----------------------------------------6-8 mm
Sub titles ------------------------------------------3-6 mm
Notes, dimension figures, etc. ---------------3-5 mm
Drawing no. --------------------------------------10-12 mm
 ABCDEFGHIJKLMN
d/2 d

OPQRSTUVWXYZ
1234567890

abcdefghijklmnopqrstuvwxy
z
 Dimensioning
The art of writing the various sizes or measurement on the finished drawing of an object.
Types of Dimensioning:
i. Size or Functional Dimensions (S):
It indicates sizes.
e.g. length, breadth, height, diameter, etc.
ii. Location or Datum Dimensions (L):
It shows location or exact position of various constructional details within the object.

L L S

S
L
 Notations of Dimensioning

Symbol
Note 2 Holes, Ø12

Leader
(at 30o,45o,60o)

90

Extension line Dimension line Arrow-head

Dimension figure

X
3X
1. Dimension line:
Thin continuous line used to indicate the measurement.
2. Extension line:
Thin continuous line extending beyond the outline of the object.
3. Arrow-head:
Used to terminate the dimension line. Length : width ratio is 3:1.
Space filled up.
4. Note:
Gives information regarding specific operation relating to a feature.
5. Leader:
Thin continuous line connecting a note or a dimension figure with the feature to which it is applied.
Terminated by arrow-head or dot.
6. Symbol:
The representation of any object by some mark on the drawing.
 Units of Dimensioning

As far as possible all dimensions should be given in millimeters omitting

the abbreviation mm.
If another unit is used, only the dimension figures should be written. But
a foot note such as ‘All the dimensions are in centimeters’ is inserted in a
prominent place near the title box.
e.g. 15.50
0.75 (Zero must precede the decimal point.)
15.50 ± .75 ( Zero is omitted.)
 The ways of Placing the Dimensions in a Series

20
20 15 25
35

60

Chain Parallel
 The ways of Placing the Dimensions in a Series

15 15

30 30
90 60 45 30 0 15 30

Combined Progressive
 The ways of Placing the Dimensions in a Series

1. Chain Dimensioning:
Dimensions are arranged in a straight line.
2. Parallel Dimensioning:
All the dimensions are shown from a common base line.
The smaller dimension is placed nearer the view.
3. Combined Dimensioning:
Chain and parallel dimensioning used simultaneously.
4. Progressive Dimensioning:
One datum or surface is selected which reads as zero. All the dimensions are referred to that point
or surface.
 Types of Dimensioning
1. Aligned System
In the aligned system the
dimensions are placed perpendicular to the
dimension line in such a way that it may be
read from bottom edge or right hand edge
of the drawing sheet.
2. Unidirectional System
In the unidirectional system, the
dimensions are so oriented such that they
can be read from the bottom of the
drawing.
 Some Important Rules for Dimensioning

1. All the dimensions necessary for the correct functioning of the part should be expressed directly on
the drawing.
2. Every dimension should be given, but none should be given more than once.
3. A dimension should be placed on the view where its use is shown more clearly.
4. Dimensions should be placed outside the view, as far as possible.
5. Mutual crossing of dimension lines and dimensioning between hidden lines should be avoided. Also
it should not cross any other line of the drawing.
6. An outline or a centre line should never be used as a dimension line. A centre line may be
extended to serve as an extension line.
7. Aligned system of dimensioning is recommended.
8. Dimension lines should be drawn at least 8 mm away from the outlines and from each other.
9. The extension line should be extended by about 3 mm beyond the dimension line.
10. When the space is too narrow, the arrow-head may be placed outside.
Also a dot may be used to replace an arrow-head.
10
15 10 15 15 10

11. The various methods of dimensioning different sizes of circles are as

follows: Ø20 Ø20
Ø10

12. Arcs of circles should be dimensioned by their respective radii.

R8

R3

R6
13. Radii of a spherical surface and square cross section of a rod is shown
as below:
Sphere R20 SQ24

14. Angular dimension may be given as follows:

25o

45
40

Length of Chord of Arc

15. Method of dimensioning of Chamfer:
2×45o

16. Dimensioning of Tapered Surface:

H
h

Slope or Taper = (H-h)/L