introductiontoengineeringgraphics-170307045101.docx

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.”
13/01/2017 Introduction to Engg. Graphics 1

What is Engineering Drawing

Role of Graphics
• Visualization
• Communication
• Documentation

Role of Graphics
1200 CE, 73 meter high minar with 14.32 meter diameter at the base
and 2.75 meter diameter at the peak. It has inside stair with 379 steps.

Applications of Engineering Drawing
Ships

Manufacturing of Automobiles

Construction

Introduction
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. Artistic Drawing
2. Engineering Drawing

1. 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.

2. Engineering Drawing
The art of representation of engineering objects.
e.g. buildings, roads, machines, etc.

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

Drawing Instruments

Use of Drawing Instruments

150
Title Block
30 20
Layout of Drawing Sheet
All the dimensions are in millimeters.
19/01/2017 Type of Lines, Dimensioning and Lettering 14
50
20
20

50 50 50
Title Block (Sample)
19/01/2017
NOTES:
All the dimensions are in millimeters.
Name an
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k-pen. 15
CHECKED BY:
GRADE:
SHEET NO.: 01
SUB. DATE:
LINES
&
LETTERING
SEM. & SEC.:
ROLL NO.:
NAME:
10
10
10
10
10
10
10
10
20

Sheet Size

Line Thickness:
LINES
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
(mm)
Thickness Lines
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
1
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
9/01/2017
Continuous thin
(straight with zigzags)
Type of Lines, Dimensio
D1
ning an
Long-break lines
d Lettering 18

Lines
E
F
G
Description
Dashed thick
Dashed thin
Chain thin
General Applications
E1 Hidden outlines
E2 Hidden edges
F1 Hidden outlines
F2 Hidden edges
G1 Centre lines
G2 Lines of symmetry
G3 Trajectories
H Chain thin, thick at ends H1
and changes of direction
Cutting planes
J Chain thick J1
K Chain thin double-dashed K1
K2
K3
Indication of lines or surfaces to which a
special treatment applies
Outlines of adjacent parts
Alternative and extreme positions of
movable parts
Centroidal lines
19/01/2017 Type of Lines, DimensionK
in
4
g andP
La
er
tt
te
srs
in
it
g
uated in front of the cutting plane 19

80o
K2
J1
C1
G1
H1
G3
P P
E1
A1 90
Ø10
D1
Application of various types of lines according to B.I.S.
B5
B2 B4

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
OPQRSTUVWXYZ
1234567890
abcdefghijklmnopqrstuvwxy
z
d/2
d

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
L
S

Notations of Dimensioning
Note
Symbol
2 Holes, Ø12
Leader
(at 30o,45o,60o)
90
Extension line Dimension line
Dimension figure
Arrow-head
19/01/2017 Type of L
A
in
re
ro
s,
w
D
-h
im
ee
an
dsioning and Lettering 27
3X
X

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.
19/01/
I2
t0
s
1
a
7ves time and labour. Type of Lines, Dimensioning and Lettering 28

Units of Dimensioning
As for 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.)

20 15 25
20
35
60
The ways of Placing the Dimensions in a Series
Chain Parallel

60 45 30 0 15 30
Combined Progressive
15 15
30 30
90

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.

1. Aligned System
Types of Dimensioning
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 for 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.

R3
R6
Type of Lines, Dimensioning and Lettering
15 10 15 15 10
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
11. The various methods of dimensioning different sizes of circles are as
follows:
Ø10
Ø20
12. Arcs of circles should be dimensioned by their respective radii.
R8
19/01/2017 35
Ø20

SQ24
13. Radii of a spherical surface and square cross section of a rod is shown
as below:
Sphere R20
14. Angular dimension may be given as follows:
45
19/01/2017 Length of Chord Type of Lines, Dimensioning and LettL
er
e
in
ng
gth of Arc 36
40
25
o

15. Method of dimensioning of Chamfer:
2×45o
16. Dimensioning of Tapered Surface:
Slope or Taper = (H-h)/L
L
h
H

SCALES
FOR FULL SIZE SCALE
R.F.=1 OR ( 1:1 )
MEANS DRAWING
& OBJECT ARE OF
SAME SIZE.
Other RFs are described
as
1:10, 1:100,
1:1000, 1:1,00,000
USE FOLLOWING FORMULAS FOR THE CALCULATIONS IN THIS TOPIC.
A REPRESENTATIVE FACTOR (R.F.) =
DIMENSION OF DRAWING
DIMENSION OF OBJECT
=
LENGTH OF DRAWING
ACTUAL LENGTH
=
AREA OF DRAWING
V ACTUAL AREA
= 3
VOLUME AS PER DRWG.
V ACTUAL VOLUME
B LENGTH OF SCALE = R.F. MAX. LENGTH TO BE MEASURED.
SIMILARLY IN CASE OF TINY OBJECTS DIMENSIONS MUST BE INCREASED
FOR ABOVE PURPOSE. HENCE THIS SCALE IS CALLED ENLARGING SCALE.
HERE THE RATIO CALLED REPRESENTATIVE FACTOR IS MORE THAN UNITY.
DIMENSIONS OF LARGE OBJECTS MUST BE REDUCED TO ACCOMMODATE
ON STANDARD SIZE DRAWING SHEET.THIS REDUCTION CREATES A SCALE
OF THAT REDUCTION RATIO, WHICH IS GENERALLY A FRACTION..
SUCH A SCALE IS CALLED REDUCING SCALE
AND
THAT RATIO IS CALLED REPRESENTATIVE FACTOR.

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