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
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:
Each of these has further subtypes.
Drawing paper: The size of drawing paper should be less
than drawing board and paper should be fixed properly.
Drawing board: It is a plane and smooth surface use for
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.
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.
French Curves: They are used to draw irregular curves
such as ellipse, hyperbola and parabola.
Drafter: It is useful tool for drawing parallel lines at any
inclination. It has scale as well as protractor inbuilt.
Protractor: It is use to measure and layout angles.
Set Square: It is also known as triangle. They comes in
flavors of 30, 60, 30 and 45, 90, 45.
It is useful tool for drawing parallel lines at any
inclination. It has scale as well as protractor
They are used to draw irregular curves such as
ellipse, parabola and hyperbola.
The left edge and right edge of a
drawing board has a true straight
For right-handed people, the lefthand edge of the board is called the
working edge because the T-square
head slides against it.
For left-handed people, the righthand edge of the board is called the
working edge because the T-square
head slides against it.
The T-square is made of a long strip
called the blade, fastened at right
angles to a shorter piece called the
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
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
Drafting tape is used to fasten the
drawing paper to the drawing board.
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.
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.
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
Medium leads are used for general
purpose line work in technical
Soft leads are used for various
kinds of art work. These leads are
too soft to be useful in mechanical
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.
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
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
Scales are usually made of plastic or
boxwood and are either triangular of flat in
Sheet size: The preferred
sizes of drawing sheet as
recommended by the
bureau of Indian standards
are given below as per
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.
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
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
The scales generally used
for general engineering
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:
Scale of chords
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
Main Line Types
Cutting Plane Lines
• Thick broken line that is terminated with short 90
• Shows where a part is mentally cut in half to better
see the interior detail.
• 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.
• Thin lines capped on the ends with arrowheads and
broken along their length to provide a space for the
• They indicate length.
• Thin line consisting of alternating long and short
• Used to represent the center of round or cylindrical
features, or the symmetry of a feature.
• Thin line usually drawn at a 45 degree angle.
• Indicates the material that has been cut through in a
• 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.
• Dark, heavy lines.
• Used to represent the outline or contour of the object
• Define features you can see in a particular view.