Engineeringl drawing lecture

Engineering Drawing
Course Instructor Engr. Sajid Yasin

Lecture Schedule
Lecture Timings
Tuesday (Theory)
Room D2
08:00 AM-:10:00 AM
Friday (Lab)
F3
10:00 AM-:12:00 PM

Textbooks
“Shawna Lockhart,
“Tutorial Guide to AutoCAD”,
Prentice Hall”
A.C. Parkinson, "First Year Engineering Drawing".
N.D. Bhatt, Engineering Drawing

Method of Assessment
Type Marks
Mid-semester Exam 30
End-semester Exam 40
Quiz 10
Assignments 10
Attendance 10
Total 100
*75%Attendance Mandatory

Problem
Identification
Preliminary
Ideas
Design
Refinement
Analysis
Optimization
Documentation
Typical Engineering Design Cycle

Graphics in Design Process
 Technical Graphics is a real and
complete language used in the design
process for:
1. Visualization
2. Communication
3. Documentation

Visualization
 Visualization is the ability to mentally picture
things that are not there.
 Ability to visualize problem solutions and
communicate them through sketches is one of
the most important skill of a designer.

Communication
 Refinement of your initial sketches so that your
design solution can be communicated to others
without ambiguity.
 Usually done by creating a three-dimensional
(3D) model

Documentation
 Is a process to permanently record that solution.
 2D-drawing follow strict standard practices.
 These standards are the language used to
communicate graphically

Drawing
 A drawing is a graphical representation of
objects and structures and is done using
freehand, mechanical or computer methods.
 A drawing serves as a graphic model or
representation of real object or idea.

 It refers basically to the use of drawings to
represent design ideas, configurations and
specifications and to use analysis required for
an engineering project.
Engineering Graphics

Engineering Drawing
 An engineering drawing is a set of drawings that
communicates an idea, design, schematic or model.
 Engineering drawing is a universal graphic
language, known as the Language of Engineers.
 It is used by engineers to develop and record their
ideas and transmit them to others for execution.
 Engineering drawing can express the complete
information about any object with exactness and
details.
Different Types of Drawing
For e.g. mechanical engineers need productions
drawing to manufacture a component or assembly.

Standards
 Standards are sets of rules that govern how
technical drawing are presented.
 Drawing standards are used so that drawings
convey the same meaning to everyone who
reads them.
 Some common standards are:
 ANSI: American National Standard Institute
 ASME: American Society of Mechanical Engineers.
 ISO: International Standard Organization.
 JIS: Japanese Standards
 MIL: U.S. Military

Drawing Sheets
 Trimmed paper of a size A0 ~ A4.
A4
A3
A2
A1
A0
Standard Sheet Size(JIS)
A4 210 x 297
A3 297 x 420
A2 420 x 594
A1 594 x 841
A0 841 x 1189
(Dimensions in millimeters)

Orientation of Drawing Sheet
1. Type-X (A0~A3)  2. Type-Y (A4 only)
Sheet size c (mm) d (mm)
A4 10 25
A3 10 25
A2 10 25
A1 20 25
A0 20 25

Instruments
 In order to create a manual engineering drawings
various instrument are used.
a) Drawing Board
b) Compass
c) T-Square
d) Set-Square
e) Scales (Rulers)
f) French Curves
g) Pencils

Drawing Boards
 Size:
1000(mm) x 1500(mm)

Compass
 The compass is used to draw circles, arcs and
intersection point. of varying diameters.

T-Square
 T-Square is used for drawing parallel
horizontal lines and
 As a base for set squares, for drawing vertical,
inclined or mutually parallel lines.
 The stock of the T-square moves overthe
working edge of the drawing board.
 The working edge
of the blade should
be perfectly straight.
Stock Drawing Edge
Blade

Set Squares
 A set square or triangle is an object used in
technical drawing, with the aim of providing a
straight edge at a particular point to a baseline.
 The simplest form of set square is a triangular
piece of transparent plastic.
Drawing
parallel lines.
Perpendicular
lines.

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.

Scales (Ruler)
 The international organization that established
the metric standard is ISO. The system is called
the International System of Units.
 Mostly use millimeter scale
 Inch
 Conversion (Inch to mm)
 1” (1 inch) = 25.4 mm
mm

French Curves
 They are made mostly of plastic and come in
various shapes.
 French curves are used for drawing curves which
cannot be French curves are use for drawing
curves which cannot be drawn with a compass.
 The curves should be drawn with a single stroke,
so that no corners are formed.
 They are used for drawing many non-circular curves on
graphic charts and or plotting motion, forces and
engineering graphs.

Drawing Pencils
 High-quality drawing pencils should be used in
technical drawing,
 Choose a mechanical pencil that feels
comfortable in your hand.

Drawing Pencils
 The following will be used in labs.. 1 H 2 H HB

Common Line Types
 Visible Lines: Represent the outline of the object
Continuous thick lines.
 Hidden Lines: Used to show the hidden part of the
drawings.
2mm 1mm
 Center Lines: Used to indicate the axes of cylinder, cone
 Phantom Lines: Used to indicate an alternate position of
a moving component.

Common Line Types
 Cross Section Lines: Used to show the edges of
a cutting plane.
 Dimension Lines: Thin continuous lines.
Terminate with an arrow head.
Dimensions (mm or inch)
 Extension Lines: Are continuous lines used in
dimension lines. A gap should be maintain
these lines and the visible lines of an object.

Types of Lines (Assignment #1)

Title Box
Name: A B C 8
Reg #: 2019XXX 8
Title : ………………… 8
Date : 19 Sep 2019 8
100
Note: All dimensions are in mm.

Drawing Scales
 Scale is the ratio of the linear dimension of an
element of an object shown in the drawing to the
real linear dimension of the same element of
the object.
Length, size
Size in drawing Actual size
:

Drawing Scales
 Designation of a scale consists of the word
“SCALE” followed by the indication of its ratio,
as follow
 Dimension numbers shown in the drawing are
correspond to “true size” of the object and they
are independent of the scale used in creating
that drawing.
Scale Size
SCALE 1:1 for full size
SCALE X:1 For enlargement scales
(X > 1)
SCALE 1:X For reduction scales (X > 1)

LETTERING Rules
 Always use a sharp edge pencil.
 Make all lettering the same size.
 Use engineering paper (A3, A2 etc)
 Single stroke letters
 General Proportions of letters
 No fix standards for proportions of standards
 It should be such that it looks pleasant to eyes
LETTERS
LETTERS
LETTERS
(Normal)
(compressed)
(Extended)
Proportions

Pencil Techniques
 The best pencil for lettering on most surfaces
are the 1H, 2H, and HB grades.
 Hold your pencil in the position shown. It should
make approximately a 60o angle with the
paper.

LETTERING
 The style of engineering lettering we will use in
the lab is Single Stroke Gothic Lettering
 Lettering is drawn freehand and are drawn
within light horizontal guidelines. Typically
lettering is 1/8” high.
 All lettering uses upper case letters. Lower
case letters are rarely used in technical
drawings.
 There are three aspects of good lettering:
proportions and forms of the letters,
composition and spacing, and practice.

Lettering Techniques
Guidelines:
• Note the letters width to height
ratio is 3/4 (like the "B") to 1 (like
the "A" or the "O"). In some cases,
like the "W", the ratio is actually
greater than 1.
• Also note, the letters are drawn on
horizontal guidelines. The
guidelines used for the figure
were originally 3/16" (the height
of the letters) with 1/16" of space
between each line.
• Spacingbetweenletters should
be consistent and not too tight.

Using Drawing Tools
& Applied Geometry

TOPICS
Preparation of Tools.
Using of Tools
Applied Geometry

1. Place the paper close to the table’s left edge.
2. Move the paper until its lower edge place about the top
edge of T-square.
Fastening Paper to Drafting Board

Fastening Paper to Drafting Board
3. the top edge of the paper with T-square blade.
4. Attach the paper’s corners with tape.
5. Move T-square down to smooth the paper.
6. Attach the remaining paper’s corners with tape.

Sharpening the Pencil
1. Remove the wood with penknife while expose a
lead about 8-10 mm.
2. Polish the lead into a conical shape with a
sandpaper.
3. Clean the lead with tissue paper.

needle lead
Preparing the Compass
1. Sharpen the lead with a sandpaper.
2. Adjust the needle and the lead so that the tip of
the needle extends slightly more than the lead.

Straight line
Arc, Circle
4. Circle template
1. T-square
2. Triangles
3. Compass
Tools Shape to be drawn
Function of the Tools

Using the Compass
1. Locate the center of the circle by two
intersecting lines.
2. Adjust the distance between needle and lead to
a distance equal to radius of the circle.
3. Set the needle point at center.

4. Start circle. Apply enough pressure to the
needle, holding compass handle between thumb
and index fingers.
5. Complete circle. Revolve handle clockwise.
Using the Compass

Draw a Horizontal Line
1. Press the T-square head against the left edge of the table.
2. Smooth the blade to the right.

Draw a Horizontal Line
3. Lean the pencil at an angle about 60o with the paper in the
direction of the line and slightly “toed in”.
4. Draw the line from left to right while rotating the pencil slowly.

Draw a Vertical Line
1. Set T-square as before. Place any triangle on T-square edge.
2. Slide your left hand to hold both T-square and triangle in
position.

Draw a Vertical Line
3. Lean the pencil to the triangle.
4. Draw the line upward while rotating the pencil slowly.

Draw a line at 45o with horizontal
2. Draw the line in the direction as shown below.
1. Place 45o triangle on the T-square edge and press them
firmly against the paper.

1. Place 30o-60o triangle on the T-square edge and press
them firmly against the paper.
2. Draw the line in the direction as shown below.
Draw a line at angle 30o and 60o

Drawing Lines at Standard Angles
HORIZONTAL 0°HORIZONTAL 0°
90°VERTICAL

0 deg.
15 deg.
30 deg.
45 deg.
60 deg.
75 deg.
90 deg.
= 30 + 45 deg
Already
demonstrated.
= 30 + 45 deg
Already
demonstrated.
Draw the lines at 15o increment

A
B
Draw the line passing through two given points
1. Place the pencil tip at one of the points.
2. Place the triangle against the pencil tip.
A
B
Given
3. Swing the triangle around the pencil tip
until its edge align with the second point.
4. Draw a line.

To Bisect a Line
1. Swing two arcs of any radius greater than half-length of
the line with the centers at the ends of the line.
2. Join the intersection points of the arcs with a line.
(not to scale)
A
B
r1
Given
A
B
r1
3. Locate the midpoint.

To Bisect an Angle
2. Swing the arcs of any radius from the intersection
points between the previous arc and the lines.
3. Draw the line.
1. Swing an arc of any radius whose centers at the vertex.
(not to scale)
r1
Given
A
B
C
A
B
C
r2
r2

To draw the line parallel to a given line and
passes through a given point
Given
+
C

To draw the line parallel to a given line and
passes through a given point
Given
+
C
Repeat

To draw the line parallel to a given line with
a specified distance
Given distance = r
r

r
To draw the line parallel to a given line with
a specified distance
Given distance = r

To draw the line perpendicular to a given
line at a given point
+
C
Revolve method

+
C
Revolve method

+
C
Adjacent-sides method

+
C

Using Compass
r1
+
C
r2
r2 > r1
A
B
D

line from a point not on the line
+
C

+
C
Repeat

Using compass
r2
+ C
r2
r1
Note:
You can also use revolve method. How ? Try by yourself !!!
B
A
D

+
C
To draw a line making 15o with a given line
and pass through a given point.
Given

+
C
Given

FILLET AND ROUND
Sharp corner
Fillet
Round
Round

FILLET AND ROUND
To draw the arc, we must find the location of the center of
that arc.
How do we find the center of the arc?

To draw an arc of given radius tangent to
two perpendicular lines
Given arc radius r
r
r

two perpendicular lines
Given arc radius r
center of the arc
Starting point
Ending point

two lines
Given arc radius r
+
+
r
r

two lines
Given arc radius r
T.P.1
T.P.2

C
To draw a line tangent to a circle at a point
on the circle
Given

To draw a line tangent to a circle from a
point outside the circle
Given
C
mark a tangent point

When circle tangent to other circle
C1
C2
Tangent point
R1
R2
The center of two circles and tangent point must lie on the
same straight line !!!

To draw a circle tangent to two circles I
+
C2
Given
+
C1
C
+
Example

+
+
C1
C2
R + R1
Given Two circles and the radius of the third circle = R
R + R2
R1
R2
C
center of the arc
To draw a circle tangent to two circles I
R

C2
R2
When circle tangent to other circle
C1
Tangent point
R1
The center of two circles and tangent point must lie on the
same straight line !!!

Given
+
C1
+
C2
C +
To draw a circle tangent to two circles II
Example

+ +
C1
C2
R – R2
To draw a circle tangent to two circles II
R – R1
R1
R2
C
R

+C1
+C2
To draw a circle tangent to two circles III
R + R2
R – R1
R1
R2
C

Keep Your Drawing Clean
Do Don’t

Basic Drafting Skills
003.03
Demonstrate correct drawing
procedures

Drawing the Border
TITLE BLOCK AREA
.38
.50
7.63
8.50
.38 10.25 .38
11.00
Recommended layout for
A size sheet

Drawing the Title Block
 Title block contains information such as drafter,
date, and scale
→ Dimensions shown are recommended and may be varied to
accommodate the user’s requirements
INFORMATION RELATED
TO PREPARATION OF
DRAWING INCLUDES
NAME OF DRAFTER,
ENGINEER, CHECKER,
ISSUE DATE, ETC.
COMPANY NAME
AND ADDRESS
TITLE
SIZE CAGE CODE DWG NO. REV
SCALE SHEET
1.75
3.25
4.25
6.25
.382.38
3.88
.25
.63
1.38
2.00

Centering a Single View Drawing
5.50
1.50
3.00
8.75
1.75 1.75 1.75 1.75

Step 1
4.38 4.38
2.75
2.75

Step 2
1.50
3.00
1.75 1.75 1.75 1.75

Step 3

Step 4

Scale Drawings
 Measurements can be full size or in
some exact proportion to full size
 Triangular scales are typically used to
allow for more scales per stick
 Scales are noted on drawings as
→ Drawn units = actual units
→ Drawn units : actual units

Reading a Mechanical Scale
16 0 1 2
FRACTIONAL INCH SCALE (FULL SIZE)
1
16
1
4
1
8
1
2
1 2 3
16

Reading a Mechanical Scale
FRACTIONAL INCH SCALE (HALF SIZE)
0 1
44 42
2
40
3
1
2
3
8
71
4
1 2
2
1

Reading a Decimal Scale
DECIMAL INCH SCALE (FULL SIZE)
50
(.0
2)
0
2 4 6 8
1
2 4 6
1.50.74 1.12

Reading a Decimal Scale
DECIMAL INCH SCALE (HALF SIZE)
HALF
SIZE
0 1 2 3 4 5 6 7 8
1.70.50 5.903.20

Reading a Metric Scale
1:1 SCALE (1mm DIVISIONS)
m
m
1:1
0 10 20 30 40 50 60 70 80
42246 66

Reading a Metric Scale
HALF SCALE (2mm DIVISIONS)
m
m
1:2
0 20 40 60 80 100 120 140 160
282 62 110

Measuring Angles w/ a Protractor
 Angles are measured in units called degrees
 A circle is divided into 360 parts (360°)
→ Each part is 1°
 An angle of 43° is measured with a protractor
43°

Alphabet of Lines
 Construction lines
→ Thin and light
→ .020” (0.5mm)
→ Hard lead (4H)
 Visible lines
→ Thick and dark
→ .028” (0.7mm)
→ Softer lead (F or HB)

Alphabet of Lines
 Hidden lines
→ Thin and dark
→ .020” (0.5mm)
→ .125” (3mm) long dashes w/
.030” (1mm) spaces in between
.0625"
.125"

Alphabet of Lines
 Center Lines
→ Thin and dark
→ .020” (3mm)
→ .125” (0.5mm) dash in center w/
.030” (0.1mm) spaces between
longer lines
.125"
.0625".75" - 1.5"

Alphabet of Lines
 Dimension, Extension, Leader Lines
→ Thin and dark
→ .020” (0.5mm)
6.125”

Alphabet of Lines
Thickness
Thick
(.028”/.07mm)
Thin
(.020”/.05mm)
Darkness
Dark
(F or HB)
Visible Lines
Hidden Lines
Center Lines
Dimension Lines
Extension Lines
Leader Lines
Light
(F or HB)
Construction Lines
Guidelines

Graphical means of expression of technical
details without the barrier of a language.
Universal language for engineers
Engineering Drawing
Drawing
Describing any object/ information diagrammatically

Diagrams/sketches/pictures – communication skills
• We grasp information easily if it is illustrated with
diagrams, sketches, pictures, etc.
LCA - the world's smallest, light weight, multi-role
supersonic combat aircraft of the world

AIRBUS A380
Source: http://img.stern.de/_content/53/96/539645/A380_500_artikel_500.jpg
Details: largest passenger jet. 80m wingspan and a tail that stands as high
as a seven-storey building, carries more than 550 passengers.

It would just be impossible to communicate all
necessary details about the LCA/ Airbus A380
verbally or in writing – Illustration
(picture/drawing) is useful.
• A picture/drawing is worth a thousand words..
• The LCA/Airbus A380 would be impossible to
create without computer graphics and drawing
models.
•Drawings are the road maps which show how to
manufacture products and structures.

Impossible to describe the details
of the building

Difficult to describe the details of the machine

Drawing is important for all branches of
engineering.

Graphical representation of an object – Drawing
• Engineering drawing – A drawing of an object
that contains all information
-like actual shape, accurate size,manufacturing
methods, etc., required for its construction.
-No construction/manufacturing of any (man -
made) engineering objects is possible without
engineering drawing.

What will you learn in this course?
You will learn - How industry communicates technical
information.
• Visualization – the ability to mentally control visual
information.
• Graphics theory – geometry and projection techniques.
• Standards – set of rules that govern how parts are made
and technical drawings are represented.
• Conventions – commonly accepted practices and methods
used for technical drawings.
• Tools – devices used to create technical drawings and
models.
• Applications – the various uses for technical drawings.

Engineering drawing is completely different
from artistic drawing, which are used to
express aesthetic, philosophical, and
abstract ideas.

Computer has a major impact on the methods used to
design and create technical drawings.
Design and drafting on computer are cheap and less time
consuming.
Why we go for manual drawing?
Engineering Drawing
Manual Drawing CADD

Computer cannot replace the drafting board and
equipment as a learning tool.
Once you have learned the basics of mathematics, now
after class 12, you are allowed the use of calculator
and computer.
If basic fundamentals are clear, better use can be
made of the power of the software.
To be an expert in technical drawing, this first course
on Engineering (manual) Drawing is the first step.
Why we go for manual drawing?

Items required for drawing Items required for drawing
Drawing board
Drawing sheet
Mini-drafter/drafting machine/ T- sqaure
Instrument box containing compass, divider, etc.
Scales
Protractor
French curves
Drawing pencils
Eraser
Drawing clip/pin/adhesive tape
Sharpener
Duster

Drawing board must be placed on the table
with working edge always to be at the left
side.
Working edge

Last two sizes are normally used for student drawing

Mini-drafter – a miniature version of the drafting machine

Mini-drafter fixed on drawing board

Set the protractor
head with reference
mark indexing zero
degree.
Fix the clamp of the
mini-drafter at the top
left corner either along
the top horizontal edge
of the board or along
the left vertical edge of
the board.
….contd
Clamping mini drafter

•Place the drawing sheet underneath the scales
of the mini-drafter,
•Fix the drawing sheet to the drawing board
with the scales of the mini-drafter aligned
either with the vertical or the horizontal
borderlines of the drawing sheet.
Clamping mini drafter….. contd

Standard sizes of drawing sheets as per BIS
A2 size

Layout of drawing sheets
• Standard form of arrangement
• Important particulars are included
• Facilitate quick reading of important particulars – quick
references are located easily – drawings are prepared at
various locations and shared
Grids along the horizontal edges – Numerals
• Grids along vertical edges – Capital letters
• 25 mm < Length of the grid < 75 mm
•

Numbering and lettering start from the corner of
the sheet opposite to the title box and are repeated
on the opposite sides
Numbers and letters are written upright
• Repetition of letters or numbers like AA, BB, etc.,
if they exceed that of the alphabets.
Borders – space left all around in between the
trimmed edges of the sheet- A minimum of 10 mm

Grid reference system –
For all sizes of drawing sheets for easy location of
drawing within the frame. The length and the width
of the frames are divided into even number of
divisions.
Number of divisions for a particular sheet depends
on complexity of the drawing – Not to be followed in
this course.

Title box – An important feature – a must in every drawing
sheet – for technical and administrative details
• Location - Bottom right corner – 185 mm x 65 mm (BIS)
• Divided into two zones
• Identification zone
• Registration or identification number
• Drawing title
• Name of the legal owner of the drawing, i.e., name of the
firm or the company
Contd…

Additional information zone
• Indicative items –symbol indicating the system of
projection, main scale of drawing, etc.
• Technical items – method of indicating surface
texture, geometric tolerances, etc.
• Administrative items
Title box….. contd

Layout of the title box to be adopted in this course
INDIAN INSTITUTE OF TECHNOLOGY KHARAGPUR
TITLE:
SCALE:
NAME:
ROLL NO:
PLATE NO:
EVALUATED BY
110 75
20
10
15
10
10

Drawing Pencils
Wooden pencils – are graded and designated by numbers and letters
Mechanical clutch pencils – Not allowed
• 7B, 6B, 5B, 4B, 3B, 2B, B - in decreasing order of softness and
blackness
• HB to F – Medium grade
• H, 2H, 3H, 4H, 5H, 6H, 7H, 8H, 9H – increasing order of
hardness.
Drawings are done using 2H pencils and finished with H
and HB pencils – to be practiced in this course.

Grades and designation of wooden pencils

Pencil drawing –
In finished drawing, all lines (except construction lines-
used to construct the drawing) should be dense, clean and
uniform.
Construction line should be drawn very thin and should be
hardly visible in the finished drawing ( they should not be
erased).

Uses of different types of lines in a given drawing

Examples of good and poor drawing techniques for
lines and arcs

Lettering – Writing of titles, sub-titles, dimensions,
scales and other details on a drawing
• Essential features of lettering – legibility, uniformity,
ease, rapidity, and suitability for microfilming/
photocopying/any other photographic processes
• No ornamental and embellishing style of letter
Plain letters and numerals which are clearly
distinguishable from each other in order to avoid any
confusion even in case of slight mutilations

Lettering – BIS: 9609
• Single stroke lettering for use in engineering
drawing – width of the stem of the letters and
numerals will be uniformly thick equal to thickness of
lines produced by the tip of the pencil.
• Single stroke does not mean – entire letter
written without lifting the pencil/pen

Lettering types
• Lettering A – Height of the capital letter is divided into
14 equal parts
• Lettering B – Height of the capital letter is divided into
10 equal parts

Heights of Letters and Numerals
• Height of the capital letters is equal to the height
of the numerals used in dimensioning
• Height of letters and numerals – different for
different purposes

Specifications of A -Type Lettering

Specifications of B -Type Lettering

Standards and Conventions
No effective communication without an agreed upon
standard of signs or symbols.
Standards and conventions are the alphabet of technical
drawing, and plane, solid, and descriptive geometry are the
science(grammar) which underlies the graphics language.

Following the standard rules (grammar) of any language
(Hindi/English) – communication of thought between
people becomes easier.
If words in a sentence were presented randomly –
understanding becomes very difficult.
For effective communication of technical (graphics)
information– set of standards and conventions – a must.
Standards and Conventions – very important

Conventions – commonly accepted practices, rules,
or methods.
Dashed lines are used
to represent hidden
features of an
engineering drawing..
Hidden lines – location
of drilled hole’s
diameter, in a view
where the hole cannot
be directly seen.

Drawings are dimensioned using an accepted set of
standards such as placing the dimension text such that
it is read from the bottom of the sheet.
Standards – set of rules that govern how technical
drawings are represented..

Drawing standards
ANSI – American National Standards Institute
ANSI Y14.1 1980 (R1987) – Drawing sheet size
and format
ANSI Y 14.2M-1979 (R1987) – Line conventions
and lettering
ANSI Y14.5M-1982(R1988) – Dimensioning and
tolerances
ANSI Y 14.3-1975(R1987) – Multi view and sectional view drawings
ISO – International Standards Organization
JIS – Japanese Standards
BIS – Bureau of Indian Standards

Units of Measure
International systems of units (SI) – which is based on
the meter.
Millimeter (mm) - The common SI unit of measure on
engineering drawing.
Individual identification of linear units is not required if
all dimensions on a drawing are in the same unit (mm).
The drawing shall however contain a note:
ALL DIMENSIONS ARE IN MM. (Bottom left
corner outside the title box)

Dimensioning
Indicating on a drawing, the size of the object and
other details essential for its construction and
function, using lines,numerals, symbols, notes, etc.
Dimensions indicated on a drawing should be those
that are essential for the production, inspection and
functioning of the object and should not be mistaken
as those that are required to make the drawing of an
object.

Dimensioning of an
object is
accomplished by
dimensioning each
element to indicate
its size (size
dimensions) and
relative location
(location dimensions)
from a center line,
base line or finished
surface.

Each feature is
dimensioned
and positioned
only once.
Each feature is
dimensioned
and positioned
where its
shape shows.

Size dimensions – give the size of the component.
Solid:
Every solid has three dimensions,each of the geometric
shapes making up the object must have its height,
width, and depth indicated in the dimensioning.

Basic geometric shapes used in drawing

Prism – most common shape
requires three dimensions -
give two dimensions on the
principal view and one
dimension on the other
views.

Cone – requires
two dimensions –
diameter of the base
and altitude on the
same view and
length – both are
shown preferably on
the rectangular view.

Right pyramids –
requires three
dimensions –
dimensions of the
base and altitude.

Spheres – requires
only one dimension – diameter.

Location dimensioning
After the basic geometric shapes have been
dimensioned for size, the location of each relative to the
others must be given.
Locations must be established in height, width and
depth directions.
Rectangular faces are positioned with reference to
their faces, cylinder and conic shapes with reference to
their center lines and their ends.

Size and Location dimensioning

Terminology for
dimensioning practice
Dimension – numerical
value that defines
the size or geometric
characteristics of a
feature – size 3.5 mm
and space between
lines of text 1.5 mm.

Dimensions showing the
sizes of features, such
as width, height and
depths of the parts and
the diameter of the hole
Dimensions showing the
location and orientations
of features, such as
location of the center of
the hole

Basic dimension – a numerical value defining
theoretically exact size of a feature.
Reference dimension – a numerical value enclosed in
parenthesis, provided for information only and not
directly used in the fabrication of the part – is a
calculated size used to show the intended design size
of a part.

Dimension line
A thin, solid line that shows the extent and direction of
a dimension. Dimension lines are broken for insertion of
the dimension numbers.
Should be placed at least
10 mm away from the
outline and all other
parallel dimensions should
be at least 6 mm apart,
or more if space permits.

Arrows – 3 mm wide and should be 1/3rd as wide as
they are long - symbols placed at the end of dimension lines
to show the limits of the dimension. Arrows are uniform in
size and style, regardless of the size of the drawing.

Extension line – a thin, solid line perpendicular to a
dimension line, indicating which feature is associated
with the dimension.
Visible gap – there should be a visible gap of 1.5 mm
between the feature’s corners and the end of the
extension line.

Leader line
− A thin, solid line used to indicate the feature with
which a dimension, note, or symbol is associated.
− Generally a straight line drawn at an angle that is
neither horizontal nor vertical.
− Terminated with an arrow touching the part or detail.
− On the end opposite the arrow, the leader line will
have a short, horizontal shoulder. Text is extended
from this shoulder such that the text height is
centered with the shoulder line.

Diameter symbol – φ - a symbol which precedes a
numerical value, to indicate that the dimension shows
the diameter of a circle.
Radius symbol – R 0.5

Various types of dimension lines

Important elements of a dimensioning

Aligned method Unidirectional method

How to begin your drawing?
•Clean the drawing board and all the drawing
•instruments using duster.
•Fix the drawing sheet on the drawing board.
•Fix the mini-drafter in a convenient position.
•Draw border lines using HB pencil..
•Complete the title box using HB pencil .
•Plan spacing of drawings b/n two problems/views
beforehand.
•Print the problem number on the left top and then
•commence the drawing work.

Thank you
Source:
Engineering Graphics Communication, Gary R. Betoline, IRWIN
Graphics Series
Engineering Drawing: plane and Solid Geometry, N.D. Bhatt, Charotar
Publishing House, Anand

LETTERING
 Most common font used in drafting is

Approved Gothic lettering for
Engineering Drawings

Reasons for using single-stroke
Gothic lettering
 Saves time in production
 Easy to read and provides drawing
consistency
 Easier to learn and use

Lettering is drawing, not writing

Recommended Strokes for Vertical
Uppercase Letters

Lettering Rules
1. The type of lettering recommended by ANSI
for mechanical drafting is single stroke
gothic (vertical freehand lettering).
2. The minimum recommended lettering size on
engineering drawings is .125 inches (1/8”).
3. All dimension numerals, notes and other
lettered information should be the same
height except for titles, drawing numbers and
other captions. Titles and subtitles, for
example, may be 0.5 inch (1/2”) and.25 inches
(1/4”) high respectively.

Lettering Rules Continued
4. The composition or spacing of letters in words and
between words in a sentence should be such that the
individual letters are uniformly spaced with
approximately equal background areas. This requires
the letters such as I, N or S be spaced slightly father
apart from their adjacent letters than L, A, or W.
5. A minimum recommended space between letters in
words is approximately .0625 inches (1/16”).
6. The space between words in a note or sentence should
be about the same at the height of the letters. The
horizontal space between sentences in a note or
paragraph should be equal to twice the height of
lettering.

7. All notes should be lettered
horizontally on the sheet.
8. Use H, HB pencils for lettering. Try
them all, but use the one that gives
you the best results.
9. Many drafters prefer using a .5 mm
automatic pencil for lettering.

10.Place a clean paper under your hand
when lettering to prevent smudging.
11.As a rule of thumb, curved letters can
be placed close together and straight
letters should be placed further apart.

Use a Piece of Clean Paper to
Prevent Smudging

Spacing of Fractions and
Decimals

DIMENSIONING
1
Dimension Lines (DL)
Position of DL

DIMENSIONING
2
Alignment of DL DL of Small Features
Dimensioning Angles Dimensioning Circles

DIMENSIONING
4
Correct Practice of Dimensioning
Drawing should
only carry
dimensions needed
to manufacture

Rules for Dimensioning
1. Dimensions should be placed outside the
views
2. Dimension line should not cross each other
3. As far as possible dimension should not be
shown between dotted lines
4. Dimension line should be placed at least 8
mm from the outlines and from one another
5. Dimension figures are placed perpendicular
to dimension line
6. Dimension figure should be easily readable
from bottom and right edge of paper

Assignment
• Get your instruments sorted- buy them
or borrow them

Engineeringl drawing lecture

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