3. INTRODUCTION
Engineering drawing is a technique of creating graphical
representation that contains all necessary information
such as dimensions, specifications and notes, using which
an abstract concept can be transformed into real world
object. Application of engineering drawing are valid for
e.g.: Shipping industry, manufacturing, construction and
many more.
Some important concept of engineering drawing is like
projection. The word projection means to throw forward. It
is a process of plotting an object in an imaginary plane.
Projection has two types:
1. Parallel projection
2. Perspective projection
Each of these has further subtypes.
4. DRAWING INSTRUMENTS
1. Drawing paper: The size of drawing paper should be less
than drawing board and paper should be fixed properly.
2. Drawing board: It is a plane and smooth surface use for
drawing purpose.
3. T-square: It is a T shape drawing tool whose edge slide
along width of drawing board with the help of stop. It is
useful in drawing straight line.
4. Compass: It is used for drawing circles and arcs. The
divider is little different with both legs made of steel and
use for transferring distance.
5. DRAWING INSTRUMENTS
5. French Curves: They are used to draw irregular curves
such as ellipse, hyperbola and parabola.
6. Drafter: It is useful tool for drawing parallel lines at any
inclination. It has scale as well as protractor inbuilt.
7. Protractor: It is use to measure and layout angles.
8. Set Square: It is also known as triangle. They comes in
flavors of 30, 60, 30 and 45, 90, 45.
7. DRAFTER
It is useful tool for drawing parallel lines at any
inclination. It has scale as well as protractor
inbuilt.
8. FRENCH CURVES
They are used to draw irregular curves such as
ellipse, parabola and hyperbola.
9. DRAWING BOARD
Drawing Boards
The left edge and right edge of a
drawing board has a true straight
edge.
For right-handed people, the left-
hand edge of the board is called the
working edge because the T-square
head slides against it.
For left-handed people, the right-
hand edge of the board is called the
working edge because the T-square
head slides against it.
T-Squares
The T-square is made of a long strip
called the blade, fastened at right
angles to a shorter piece called the
head.
10. T-SQUARE
The drawing paper should be placed
close to the working edge of the
board to reduce any error resulting
from the bending of the blade of the
T-square.
The paper should also be placed
close enough to the upper edge of
the board to permit space at the
bottom of the sheet for using the
T-square.
Drafting tape is used to fasten the
drawing paper to the drawing board.
11. DRAWING PENCILS
Drawing Pencils
High-quality drawing pencils should be used in technical drawing, never ordinary writing pencils.
Many makes of mechanical pencils are available together with refill leads in all grades. Choose
a mechanical pencil that feels comfortable in your hand.
12. DRAWING LEADS
Drawing Leads
The first consideration in the selection of a grade of lead is the type of line work required. For
light construction lines and guide lines for lettering use a hard lead. For all other line work, the
lines should be BLACK. The lead chosen should be soft enough to produce jet black lines but
hard enough not to smudge.
HARD MEDIUM SOFT
9H 8H 7H 6H 5H 4H 3H 2H H F HB B 2B 3B 4B 5B 6B 7B
Hard leads are used where extreme
accuracy is required. Generally
these leads are used for
construction lines.
Medium leads are used for general
purpose line work in technical
drawing.
Soft leads are used for various
kinds of art work. These leads are
too soft to be useful in mechanical
drafting.
13. SET SQUARE
Triangles
Most inclined lines are drawn at standard
angles using the 45º x 45º triangle and
the 30º x 60º triangle.
In addition to drawing angles of 90º, 45º,
30º, and 60º, triangles can be combined
to draw angles of 15º increments.
14. COMPASS
Giant Bow Sets
Giant bow sets contain various
combinations of instruments.
Giant Bow Compass
The giant (large) bow compass has a center
wheel and can be adjusted simply by opening or
closing the legs of the compass while turning the
center wheel.
15. SCALE
Scales
Scales are instruments used in making
technical drawings full size or at a given
reduction or enlargement.
Types of scales include metric scales,
engineers’ scales, decimal scales,
mechanical engineers’ scales, and
architects’ scales.
Scales are usually made of plastic or
boxwood and are either triangular of flat in
shape.
16. SHEET LAYOUT
Sheet size: The preferred
sizes of drawing sheet as
recommended by the
bureau of Indian standards
are given below as per
SP:46(2003).
Sheet Designation Trimmed
size (mm)
Untrimmed
size (mm)
A0 841*1189 880*1230
A1 594*841 625*880
A2 420*594 450*625
A3 297*420 330*450
A4 210*297 240*330
A5 148*210 165*240
17. SHEET LAYOUT
Margin: Margin is provided in the drawing sheet by
drawing margin lines. Prints are trimmed along this lines.
Border lines: Clear working space is obtained by drawing
border lines. More space is kept on the left-hand side for
the purpose of filling or binding if necessary.
Borders and frames: SP:46(2003) recommends the
borders of 20mm width for the sheet sizes A0 and A1, and
10mm for sizes A2, A3, A4 and A5.
18. SHEET LAYOUT
Title Block: Space for title
block must be provided in
the bottom right-hand
corner of the drawing sheet.
The size of the title block as
recommended by the B.I.S
is 185mm*65mm for all
designations of the drawing
sheet. All title blocks
should contain at least the
particulars as shown in the
figure:
19. SCALES
A scale is defined as the
ratio of the linear
dimensions of element of
the object as represented
in a drawing to the actual
dimensions of the same
element of the object
itself.
The scales generally used
for general engineering
drawings are:
1) Reducing
scales
1:2 1:10 1:5
1:20 1:50 1:100
1:200 1:500 1:1000
1:2000 1:5000 1:10000
2) Enlarging
scales
50:1 20:1 10:1
5:1 2:1
3) Full size
scales
1:1
20. SCALES
Representative fraction: The ratio of length of
the object represented on drawing to the actual
length of the object represented is called RF.
If RF>1 then the drawing is enlarged.
If RF<1 then the drawing is reduced view.
The different types of scales are:
1. Plain scale
2. Diagonal scale
3. Comparative scale
4. Vernier scale
5. Scale of chords
21. LINES
Lines are predominant and fundamental drawing
element in every drawing.
Various types of lines are used to represent different
objects like visible lines are used for drawing outlines of
visible edges and surface line which represent the object.
These are drawn in bold dark and continuous lines.
Hidden lines are shown with medium thick lines
consisting of short dashes and use to represent invisible
ages and surface boundary.
Centre lines are thin lines drawn with ultimate long
dashes and dots and are used for representing
symmetrical objects. Then there are dimension and
cutting lines.
22. Main Line Types
Lines
Hidden Lines
Center Lines
Dimension Lines
Extension Lines
Leader Lines
Cutting Planes
Section Lines
Phantom Lines
Viewing Planes
Break Lines
Visible Lines
24. Cutting Plane Lines
• Thick broken line that is terminated with short 90
degree arrowheads.
• Shows where a part is mentally cut in half to better
see the interior detail.
25. Extension Lines
• Thin lines used to establish the extent of a dimension.
• Can also be used to show extension of a surface to a
theoretical intersection as shown in (b).
• Begin 1.5mm from the object and extend to 3mm
beyond the last dimension.
• They should not cross dimension lines.
26. Dimension Lines
• Thin lines capped on the ends with arrowheads and
broken along their length to provide a space for the
dimension numeral.
• They indicate length.
27. Center Lines
• Thin line consisting of alternating long and short
dashes.
• Used to represent the center of round or cylindrical
features, or the symmetry of a feature.
28. Section Lines
• Thin line usually drawn at a 45 degree angle.
• Indicates the material that has been cut through in a
sectional view.
Section
Line
29. Hidden Lines
• Light, narrow, short, dashed lines.
• Shows the outline of a feature that can not be seen in
a particular view.
• Used to help clarify a feature, but can be omitted if
they clutter a drawing.
30. Visible/Object Lines
• Dark, heavy lines.
• Used to represent the outline or contour of the object
being drawn.
• Define features you can see in a particular view.
