ENGINEERING DRAWING
Jan Lexver C. Tiangco
Charlie L. Hernandez
VISION
Laguna University shall be a socially responsive educational
institution of choice providing holistically developed
individuals in the Asia-Pacific Region.
MISSION
Laguna University is committed to produce academically
prepared and technically skilled individuals who are socially
and morally upright citizens.
Department of Mechanical Engineering
MISSION
The Department of Mechanical Engineering of Laguna
University is committed to produce academically prepared
and technically skilled mechanical engineers who are socially
and morally upright citizens.
VISION
The Department of Mechanical Engineering of Laguna
University is envisioned to be the provincial college of choice
producing well-equipped mechanical engineers who
specializes on energy management.
Table of Contents
Module 1: Drawing Instruments and their uses
Introduction
Learning Objectives
Lesson 1. Role of Engineering Drawing
Lesson 2. Drawing Instrument and Aids
Assessment Task 1
1
1
1
2
2
13
Module 2: Sheet Lay-out and free-hand Sketching
Introduction
Learning Objectives
Lesson 1. Drawing Sheet
Lesson 2. Types of Machine Drawings
Lesson 3. Free-hand sketching
Assessment Task 2
15
15
15
16
19
20
22
Module 3: Lines and Lettering
Introduction
Learning Objectives
Lesson 1. Types of Lines
Lesson 2. Lettering
Assessment Task 3
23
23
23
24
27
34
Module 4: Dimensioning
Introduction
Learning Objectives
Lesson 1. Dimensioning
Assessment Task 4
35
35
35
36
46
Course Code: ENG’G 101
Course Description: This course is designed for undergraduate engineering
students with emphasis on problem solving related to social problems that are called
upon to address by engineers and scientists. It discusses various data collection
methods and the appropriateness of using a specific method for a given situation.
This also addresses the relationship of probability to statistics, presenting students
with the information they need to grasp how "chance" plays a role in statistical
analysis.
Course Intended Learning Outcomes (CILO):
At the end of the course, students should be able to:
1. Applying statistical methods to data processing
2. Model studies addressing various variables
3. Solve problems with probability
Course Requirements:
Assessment Tasks
Major Exams
- 60%
- 40%
Periodic Grade
100%
Computation of Grades:
PRELIM GRADE
= 60% (Activity 1-4) + 40% (Prelim exam)
MIDTERM GRADE = 30%(Prelim Grade) + 70 %[60% (Activity 5-7) + 40% (Midterm exam)]
FINAL GRADE
= 30%(Midterm Grade) + 70 %[60% (Activity 8-10) + 40% (Final exam)]
MODULE 1
DRAWING INSTRUMENTS AND THEIR USES
Introduction
Engineering drawing is a two-dimensional representation of the structures in three
dimensions. In general, it offers the necessary details about the object's shape, size, surface
quality, material, manufacturing process, etc. It is the graphic language that helps a qualified
person to interpret objects from (Bhatt, 2011).
For any other country, sketches produced in one country may be used, regardless of
the language spoken. Thus, computer drawing is called computer's universal language. To be
communicative, every language should obey certain laws such that it conveys the same
message to everyone. Likewise, if drawing practice is to function as a form of communication,
it must obey certain rules. To this end, the Bureau of Indian Standards (BIS) adapted the
International Standards on Drawing Code of Practice. Certain international requirements
include: Germany's DIN, Britain's BS and America's ANSI (Bhatt, 2011).
Learning Outcomes
At the end of this module, students should be able to:
1.
Define drawing instruments and their uses.
2.
Know what instruments are to be used in a certain task.
1
Lesson 1. Role of Engineering Drawing
The ability to read drawing in any field is the most significant skill of all the skilled
people. This approach is shorter and simpler compared with the verbal or written explanation.
Many of the applications are: structural engineering design drawing, mechanical engineering
system drawing, electrical and electronics engineering circuit diagrams, computer graphics
for all (Bhatt, 2011).
The course in general is designed to impart the following skills:
1. Ability to read and prepare engineering drawings.
2. Ability to make free - hand sketching of objects.
3. Power to imagine, analyzed and communicate, and
4. Capacity to understand other subjects:
Lesson 2. Drawing Instruments and Aids
The Instruments and other aids used in drafting work are listed below (Bhatt, 2011):

Drawing board

T-square

Set of squares

Set of scales

Protractor

French curves

Templates

Drawing paper

Drawing pencils

Eraser

Drawing Pins, clips and adhesive tapes

Drafting machine
2
Drawing Board
The drawing board is rectangular in shape and is made of well-seasoned soft wood
strips about 25 mm thick. Two battens clean it to the back to avoid warping. Each of the
board's edges acts as the working edge on which the T-square is designed to move. And it
should be absolutely clear. For certain boards this edge is grooved along its length, and within
this groove is installed a perfectly straight ebony edge. It gives the T-square a real and longer
lasting guide to move on.
Table 1.1 Drawing board size
Fig. 1.1. Drawing Board
Drawing board in various sizes is made. The selection of the drawing paper depends
on the scale. Table 1.1 prescribes the sizes of draw boards that the Indian Standards Bureau
recommends (IS: 1344-1989). The last two types of drawing boards are more convenient to
use in schools and universities. For architecture and manufacturing firms' drawing rooms,
large boards are used. The drawing board is placed on the bed, and the working side is on
the left side of the student. This is safer if the Table top falls down to the student. If a Table
such as this is not usable, it can be obtained by putting a suitable piece of wood under the
longer, distant edge of the board.
T-square
A T-square consists of rough wood. It is made up of two sections-the stock and the
blade-connected together by the screws and pins in right angles. The stock is put next to the
working edge of the board and must be slide on as required. The blade is on the board top.
3
Its distant edge is usually beveled and should therefore be absolutely straight. Always uses
the closer side of the blade. The blade length is chosen to match the drawing board scale.
Celluloid or plastic with engraving scale is also available nowadays in the T-Square. Celluloid
or plastic with graved scale is also used in the T-square nowadays.
Figure 1.2. T-Square
Uses
(i) The T-square is used in horizontal line drawing. The T-square is placed on the
working edge of the board with the left hand and the line is drawn from left to right
as shown in the Fig. 1.3. The pencil should be slightly sloping towards the line (i.e.
right), while the pencil point must be as near to the working edge of the blade as
possible. By slide the stock to the desired positions, horizontal parallel fines are
drawn.
Figure 1.3. T-Square used in Horizontal Line Drawing
4
(i)
The working edge of the T-square is often used to draw vertical, inclined or
mutually parallel lines as a basis for the set-squares. You have to rotate a pencil
when drawing lines for uniform lead wear. Never using the T-square on edge other
than the working edge of the board. And when not in use it should always be kept
on board (Bhatt, 2011).
(ii)
Testing the straightness of the working edge of the T-square: mark any two points
A and B (Fig. 1-4) wide apart and, through them, carefully draw a line with the
working edge. Flip the T-square upside down as shown by dotted lines, and draw
another line with the same edge that passes through the same two points. If the
edge is faulty then the lines won't fit. The mistake should be corrected by making
the faulty edge prepared or sand-papered (Bhatt, 2011).
Figure 1.4. Straightness of the Working Edge of the T-Square
Set of Squares
Set squares are made of wood, tin, celluloid or plastic. Those made of transparent
celluloid or plastic are commonly used as they retain their shape and accuracy for a longer
period of time. In general, two forms of set-squares are used. The set-square is triangular in
shape, one of the angles being the right angle. The 30 ° -60 ° set-square of 250 mm in length
and the 45 ° set-square of 200 mm in length are convenient sizes for use in schools and
colleges.
5
Figure 1.5. Set of Squares
Uses (Bhatt, 2011)
(i)
Set-squares are used for drawing all straight lines with the exception of
horizontal lines normally formed by a T-square. With the T-square and the
set-square, vertical lines can be drawn.
(ii)
In combination with the T-square, lines at an angle of 30 ° or 60 ° with
vertical or horizontal lines may be drawn at an angle of 30 ° -60 ° set-square
and an angle of 45 ° set-square. The two set-squares used simultaneously
with the T-square will produce lines with angles of 15 °, 75 °, 105 °, etc.
(iii)
Parallel straight lines in any position, not very far apart, as well as lines
perpendicular to any line in or outside any given point, may also be drawn
with the two set-squares.
(iv)
The circle may be divided into six, eight, twelve and twenty-four equal parts
by means of the squares and the squares.
Set of Scales
Scales are made of wood, steel, celluloid or cardboard or plastic. Stainless-steel
scales are longer lasting. Scales can be flat or cross-sectionally triangular. The flat scales are
15 cm long and 2 cm high, or 30 cm long and 3 cm wide. Their thickness is typically around 1
mm. Larger-thickness scales have their longer edges beveled. That helps to accurately mark
measurements from the scale to the drawing paper. All the longer sides of the scales are
marked with centimeter segments, which are subdivided into millimeters.
6
Figure 1.6. Ruler
The scale is used to convert an object's real or relative dimensions into the picture. It
is placed on the line with its edge on which measurements are to be marked and the marking
is done with a fine pencil point, looking from exactly above the appropriate division. The scale
should never be used for drawing lines as straight-edges. The eight-scale set of cardboard
scales is available. As shown in Table 1.2, these are classified from M7 to MB
Table 1.2 Cardboard Scales
Scale on one edge
M1
M2
M3
M4
M5
M6
M7
M8
1:1
1:2:
1:10
1:50
1:200
1:300
1:400
1:1000
1:20 1:100
1:500
1:600
1:800
1:2000
5
Scale on the other
1:2
1:5
edge
7
Table 1.3 Scales for Use on Technical Drawings (Is: 46-1988)
Category
Enlargement scales
Recommended scales
50:1
20:1
5:1
2:1
Full size
Reduction scales
10:1
1:1
1:2
1:5
1:10
1:20
1:50
1:100
1:200
1:500
1:1000
1:2000
1:5000
1:10000
Protractor
Protractor is made of celluloid, wood, tin or. Clear celluloid Protractors are widely used.
They are flat in shape and are circular or semi-circular. The most popular type of protractor is
semi-circular and has a diameter of about 100 mm. The circumferential edge is divided to 1 °,
numbered at every 10 ° interval and visible from both ends. The semi-circle diameter (viz.
straight-line 0-180 °) is called the protractor base, and its center O is identified with a line
perpendicular to it
The protractor is used to draw or calculate certain angles as the set-squares cannot
be drawn. Via the protractor a circle can be broken into any number of equal sections.
Figure 1.7 Protractor
French Curves
French curves come in various forms (Fig. 1.8). First a series of points are plotted
along the desired path, and then the most suitable curve is rendered along the curve's edge.
8
A flexible curve consists of a lead bar inside rubber which bends conveniently through any
collection of points to draw a smooth curve (Bhatt, 2011).
(a)
French curve
(b) Flexible curve
Fig 1.8 French and Flexible Curve
Templates
These are aids used for drawing small features such as circles, arcs, triangular,
square and other shapes and symbols used in various science and engineering fields
(Fig.1.9).
Fig 1.9 Templates
9
Drawing Paper
Drawing papers are available in many
varieties. For ordinary pencil-drawings, the
paper selected should be tough and strong. It
should be uniform in thickness and as white as
possible. When the rubber eraser is used on it,
its fibers should not disintegrate. Good quality of
paper with smooth surface should be selected
for drawings which are to be inked and
preserved for a long time. It should be such that
the ink does not spread. Thin and cheap quality
paper may be used for drawings 1 from which
tracings are to be prepared. The standard sizes
of drawing papers; recommended by the Bureau
of Indian: Standards (B.I.S.). are given in Table
2.1 (Venkata Reddy, 2008).
Fig 1.10 Drawing Paper Size
Surface area of AO size is one square meter. Successive format sizes (from AO to
AS) are obtained by halving along the length or doubling along the width. The areas of the
two subsequent sizes are in the ratio 1 :2. See Fig. 1.10 (Venkata Reddy, 2008).
Drawing Pencils
Pencils with leads with varying degrees with hardness or grades are on the market.
The lead's hardness or softness is shown by 3H, 2H, H, HB, B, 2B, 3B, etc. The HB grade
denotes medium durability of lead used for general purposes. The hardness decreases as
numeral value increases before letter H. As the numeral value increases before B (Fig.1.11)
the lead becomes softer (Bhatt, 2011).
10
Figure 1.11 Graphite Scales
The grade selection depends on the line quality for drawing. Grade H or 2H pencils
should be used to finish a pencil drawing, as these offer a straight black line. Smoother grade
pencils are used to render drawings. For lettering and measurements HB grade is
recommended. In lieu of wooden pencils today mechanical pencils are commonly used. If
these are used it is possible to save much of the sharpening time. The pen 's number 0.5,0.70
shows the line thickness obtained with the lead and the diameter of the lead. Recommended
micro-tip pencils with 0.5 mm thick leads with following grades (Venkata Reddy, 2008).
Figure 1.12 Mechanical Pencil

HB Soft grade for Border lines, lettering and free sketching

H Medium grade for Visible outlines, visible edges and boundary lines

2H Hard grade for construction lines, Dimension lines, Leader lines, Extension lines,
Centre lines, Hatching lines and Hidden lines.
Eraser
Soft Indian rubber is the most suitable form of eraser for
drawings on pencils. It ought not to ruin the paper's color. Careful
preparation
should
prevent
regular
rubber
use.
11
Drawing Pins, clips and adhesive tapes
The drawing paper is fixed to the drawing board. In general, the needle part of the pin
is made of steel, and the head can be of mild steel or brass. Pins of approximately 15 mm to
20 mm diameter, and flat heads of approximately 1 mm thickness made of brass are
convenient since they rust not. The pins should be placed in order to position the heads on
the paper surface. Instead of pins, clips or tapes are typically used. (Fig. 1.14) (Bhatt, 2011).
Figure 1.14 Drawing Pins, Clips and Adhesive Tapes
Drafting Machine
Within the drafting system the uses and advantages of the T-square, set-squares,
scales, and the protractor are combined. It is clamped to the much longer edge of the drawing
board using a screw. An adjustable head is fitted at the opposite end with protractor markings.
Two transparent celluloid blades are connected to the head precisely in right angles to each
other.
Figure 1.15 Drafting Machine
12
Assessment Task 1
Directions: Multiple Choices. Write the letter of the correct answer.
1. A measuring tool used to layout an angle or an arc.
A. Compass B. Divider C. Protractor D. Tape ruler
2. The most popular type of measuring tools, usually 6 or 12 inches in length.
A. Tape ruler B. Triangle C. Ruler D. Scale
3. Its main purpose is to reduce or enlarge the dimension of size on a drawing.
A. Tape ruler B. Triangle C. Ruler D. Scale
4. It is used for drawing vertical and oblique lines.
A. Ruler B. Scale C. Triangle D. T- Square
5. It provides an easy means for accurately measuring curved surfaces.
A. Compass B. Divider C. Protractor D. Tape ruler
6. These are used for the purpose of measuring dimensions.
A. Cutting Tools B. Measuring Tools C. Lining Tools D. Testing Tools
7. This is used as guide in drawing horizontal lines.
A. Ruler B. Scale C. Triangle D. T- Square
8. This instrument is used to draw circles, arcs, radii, and parts of many symbols.
A. Compass B. Divider C. Protractor D. Tape ruler
13
9. It is a concave, spring-steel blade ranging from 1/4" to 1" wide and 6 to about 300 ft in
length
A. Meter stick B. Tape ruler C. Triangle D. Ruler
10. It helps a drafter keep the proportions accurate.
A. Ruler B. Scale C. Triangle D. T- Square
11. A drafting tool used for drawing horizontal lines
A. Compass B. Triangle C. T- square D. Triangular Scales
12. Drafting material used for fastening the drawing paper on the drawing table
A. Compass B. Divider C. Masking Tape D. Triangle
13. The main function of this tool is to reproduce the measurements of an object to any
size.
A. Compass B. Protractor C. Triangle D. Triangular Scales
14. This drafting tool is used to protect the rest of the drawing when removing
unnecessary lines.
A. Erasing Shield B. Eraser C. Masking Tape D. Pencil Sharpener
15. This drafting tool is used when drawing vertical lines.
A. Compass B. Triangle C. Triangular Scales D. Ruler
References:
Bhatt, ND., (2011) Engineering Drawing, Gujarat, India, 15th ed.
Venkata Reddy, K., (2008) Textbook of Engineering Drawing, Tirupati, India, 2nd ed.
14
MODULE 2
SHEET LAY-OUT AND FREE-HAND SKETCHING
Introduction
Engineering drawings are prepared on drawing sheets of regular scale. The proper
form and size of the object can be visualized not just from the perception of its views but also
from the various types of lines used, proportions, notes, scale etc. The drawings must be
drawn for uniformity as per the common procedure (Bhatt, 2011).
Imagine an architect who wants to design a building, a mechanical engineer who wants
to design a machine or part of a system; an industrial engineer who wants to design a layout
of a plant; how does he / she starts designing? Practically everything begins with freehand
sketch and brings their idea in. Freehand sketching is one of the most successful forms of
conveying to a worker a pictorial or verbal concept. Sketching may be graphical, may
communicate new ideas, or may be instructive in conveying ideas to drafters. Upon finalizing
these ideas, principles, and information for a project, detailed technical sketches are created
using tools so that parts can be designed or built. Ingenious often use freehand drawings to
explain, analyze and document conceptual ideas and concepts (Bhatt, 2011).
Learning Outcomes
At the end of this module, students should be able to:
1. To be able to make a proper sheet layout; and
2. To be able to sketch multi-view and pictorial representation.
15
Lesson 1. Drawing Sheet (Venkata Reddy, 2008)
Sheet sizes: The preferred sizes of the drawing sheets recommended by the Bureau of
Indian Standards (B.I.S.) are given below as per SP: 46 (2003). Refer Fig. 1.10
Table 2.1 Drawing Sheet Sizes
Sheet
Trimmed size
Untrimmed size
Designation
(mm)
(mm)
A0
841 x 1189
880 x 1230
A1
594 x 841
625 x 880
A2
420 x 594
450 x 625
A3
297 x 420
330 x 450
A4
210 x 297
240 x 330
A5
148 x 210
165 x 240
The layout of the drawing on a drawing sheet should be done in such a manner as to
make its reading easy and speedy. Fig. 2.1 (a) and Fig. 2.1 (b) shows an A1 size sheet layout.
All dimensions are in millimeters.
Margin: Margin is provided in the drawing sheet by drawing margin lines [Fig. 2.1 (a)]. Prints
are trimmed along these lines. After trimming, the prints would be of the recommended
trimmed sizes of the trimmed sheets.
Border lines: Clear working space is obtained by drawing border lines as shown in [Fig. 2.1
(a)]. More space is kept on the left-hand side for the purpose of filing or binding if necessary.
When prints are to be preserved or stored in a cabinet without filing, equal space may be
provided on all sides (Fig. 2.3).
Borders and frames: SP: 46 (2003) recommend the borders of 20 mm width for the sheet
sizes AO and A 1, and 10 mm for the sizes A2, A3, A4 and AS. Frame shows the clear space
available for the drawing purpose (Venkata Reddy, 2008).
16
Orientation mark: Four centering marks are drawn as shown in Fig. 2.1 (b) to facilitate
positioning of the drawing for the reproduction purpose. The orientation mark will coincide with
one of centering marks which can be used for the orientation of drawing sheet on the drawing
board.
Grid reference system (zones system): The grid reference system is drawn on the sheet
to permit easy location on the drawing such as details, alterations or additions. The rectangle
of grid along the length should be referred by numerals 1, 2, 3 ... etc. and along the width by
the capital letters A, B, C, D etc. as shown in Fig. 2.1 (b).
Figure 2.1 (a) Layout of the Drawing on a Drawing Sheet
17
Figure 2.1 (b) Grid Reference System
Title Block: Space for the title block must be provided in the bottom right-hand corner of the
drawing sheet as shown in Fig. 2.1 (a) and Fig. 2.1 (b). The size of the title block as
recommended by the B.I.S. is 185 mm x 65 mm for all designations of the drawing sheets.
Fig. 2.2 shows the simplest type of a title block. All title blocks should contain at least the
particulars as shown in Table 2.2.
Figure 2.2 Title Block Format
18
Table 2.2 Particulars of title block
1
Name of the firm
2
Title of the drawing
3
Scale
4
Symbol for the method of projection
5
Drawing number
6
Initials with dates of persons who have designed, drawn, checked,
standards
and approved.
7
No. of sheet and total number of sheets of the drawing of the object
Figure 2.3 Student’s Sample Title Block
Lesson 2. Types of Machine Drawings
(Bhatt, 2011)
Machine drawings are prepared for various purposes and they are further classified as under:
Production drawing: a production drawing is legal document of company. It is used by the
technicians on the shop-floor for manufacturing the parts. It must provide information about
part number, dimensions, tolerance, surface finish, material and stock size, manufacturing
19
process, special finishing process if required, and no. off required for each assembly. It is
further sub-classified as:

Part drawing or detailed drawing

Assembly drawing
Exploded Assembly drawing: It represents the details of machine in a pictorial form as it is
assembled. It helps the mechanics for dismantling machine for repairing purpose.
Schematic Assembly drawing: This type of assembly drawing is used for explaining working
principle of any machine.
Drawing for instruction manual: This is assembly drawing without dimensions. Each part of
machine is numbered so that it can be easily dismantled or assembled if required. This is also
used for explaining working principle of each part.
Drawing for installation: This is assembly drawing with overall dimensions. It is used for the
preparation of foundation for installing machine.
Drawing for catalogue: Special assembly drawings are prepared for catalogues, with overall
and principal dimensions.
Tabular drawing: This is part drawing. It is used when components of same shape but
different dimensions are to be manufactured.
Patent: It is generally assembly drawing either in pictorial form or principal view of
orthographic projection of machine. It is used for obtaining patent of the machine.
Lesson 3. Free-hand sketching (Bhatt, 2011)
Sketching or freehand is the first step to a scale drawing, i.e. a drawing drawn using
instruments. A designer initially documents his ideas in the form of sketches that later become
sketches. Likewise, views of real objects are drawn free hand in the first instance. Scale
drawings from these sketches are then prepared. Ideas and concepts may be represented in
phrases, but with the aid of sketches the explanation becomes more descriptive. Sketching is
therefore of great importance in engineering. Sketching is often done hands-free. It's just a
freehand drawing in right proportions, just not to scale. A diagram should be made to give us
20
a good picture of the structure to be created, full details and a real impression. It never should
be drawn too low. The size of a sketch should be so large that it clearly includes all features
of the object, their measurements, explanatory notes, etc. Sketching skill can only be obtained
with continuous practice.
Sample Title block
The following drawing template title blocks are to be used in the assessment activities.
Figure 2.3 LU Student’s Title Block
21
Assessment Task 2
Directions: Use the standard margins, border lines, etc. shown in Fig. 2.1 (a) and Fig. 2.1
(b) and use the title block format in Fig. 2.3
1. Draw the following figures (dimensions are in mm) in an A2 size sheet.
Plate No. 1
Plate No. 3
Plate No. 2
Plate No. 4
Plate No. 5
References:
Bhatt, ND., (2011) Engineering Drawing, Gujarat, India, 15th ed.
Venkata Reddy, K., (2008) Textbook of Engineering Drawing, Tirupati, India, 2nd ed.
22
MODULE 3
LINES AND LETTERING
Introduction
A drawing involves numbers, phrases, and lines. Although we generally consider
numbers and words as meaning only, lines do have something to say. Drawing is meant to
express accurate, unique dates, not generalizations. That line illustrates something about the
object which was drawn to an experienced draftsman. There is significance of a split or gap
in a line, a dotted line, a dark line or one that is not to dark all. Much as the correct words are
used in the English textbook to render accurate sentences; in Engineering Graphics, the
specifics of the various objects are represented through various types of lines. Every line has
to convey a definite meaning and sense (Bhatt, 2011)..
Writing names, measurements, notes and other relevant information on a drawing is
called lettering. It's an integral part of a painting. However, a drawing can be made precise
and clean. The presentation is spoiled and often, bad lettering impairs the usefulness.
Therefore, lettering should be done correctly in a simple, legible and standardized design.
This should be in a basic and straightforward format, so that it can be done easily and
efficiently. Training followed by ongoing efforts will boost skill and style of lettering. Bad
lettering marks an otherwise strong drawing in appearance (Bhatt, 2011).
Learning Outcomes
At the end of this module, students should be able to:
1. To be able identify different line functions; and
2. To be able to sketch engineering lettering.
23
Lesson 1. Types of Lines (Bhatt, 2011)
Much as the correct words are used in the English textbook to render accurate
sentences; in Engineering Graphics, the specifics of the various objects are represented
through various types of lines. Every line has to convey a definite meaning and sense.
Outlines (A): Lines drawn to represent visible edges and surface boundaries of objects are
called outlines or principal lines. They are continuous thick or wide lines (Fig. 3.2).
Margin lines (A): They are continuous thick or wide lines along which the prints are trimmed
[Fig. 2.1 (a)].
Dimension lines (B): These lines are continuous thin lines. They are terminated at the outer
ends by pointed arrowheads touching the outlines, extension lines or center lines (Fig. 3.2).
Extension or projection lines (B): These lines also are continuous thin lines. They extend
by about 3 mm beyond the dimension lines (Fig. 3.2).
Construction lines (B): These lines are drawn for constructing Figures. They are shown in
geometrical drawings only. They are continuous thin light lines.
Hatching or section lines (B): These lines are drawn to make the section evident. They are
continuous thin lines and are drawn generally at an angle of 45° to the main outline of the
section. They are uniformly spaced about 1 mm to 2 mm apart (Fig. 3.2).
Leader or pointer lines (B): This leader line is drawn to connect a note with the feature to
which it applies. It is a continuous thin line (Fig. 3.2).
Border lines (B): This rectangular working space is determined by drawing the border
lines [Fig. 2.1 (a)]. They are continuous thin lines.
Short-break lines (C): These lines are continuous, thin and wavy. They are drawn freehand
and are used to show a short break, or irregular boundaries (Fig. 3.3).
Long-break lines (D): These lines are thin ruled lines with short zigzags within them. They
are drawn to show long breaks (Fig. 3.3).
24
Hidden or dotted lines (E or F): Interior or hidden edges and surfaces are shown by hidden
lines. They are also called dotted lines. They are of medium thickness and made up of short
dashes of approximately equal lengths of about 2 mm spaced at equal distances of about 1
mm. When a hidden line meets or intersects another hidden line or an outline, their point of
intersection or meeting should be clearly shown (Fig. 3.2).
Centre lines (G): Center lines are drawn to indicate the axes of cylindrical, conical or
spherical objects or details, and also to show the centers of circles and arcs. They are thin,
long, chain lines composed of alternately long and dot spaced approximately 1 mm apart. The
long dashes are about 9 to 12 mm. Centre lines should extend for a short distance beyond
the outlines to which they refer. For the purpose of dimensioning or to correlate the views they
may be extended as required. The point of intersection between two center lines must always
be indicated. Locus lines, extreme positions of movable parts and pitch circles are also shown
by this type of line (Fig. 3.2 and Fig. 3.3).
Cutting-plane lines (H): The location of a cutting plane is shown by this line. It is a long,
thin, chain line, thick at ends only (Fig. 3.2).
Chain thick (J): These lines are used to indicate special treatment on the surface.
Chain thick double-dots (K): This is chain thin double-dot line.
Figure 3.1 Types of Lines
25
Figure 3.2 Section & Leader Lines
Figure 3.3 Other Lines
Precedence of Lines (Bhatt, 2011)
1. When a Visible Line coincides with a Hidden Line or Center Line, draw the Visible Line.
Also, extend the Center Line beyond the outlines of the view.
2. When a Hidden Line coincides with a Center Line, draw the Hidden Line.
3. When a Visible Line coincides with a Cutting Plane, draw the Visible Line.
4. When a Center line coincides with a Cutting Plane, draw the Center Line and show the
Cutting Plane line outside the outlines of the view at the ends of the Center Line by thick
dashes.
26
Table 3.1 Types of Lines and their Applications (Bhatt, 2011)
Lesson 2. Lettering (Bhatt, 2011)
Lettering is defined as writing of titles, sub-titles, dimensions, etc., on a drawing.
Importance of Lettering
The size and other information in the drawing are indicated for the development of the
engineering part as per the drawing. It is achieved in notes and measurements format. Key
characteristics of lettering are legibility, clarity and speed of execution. Usage of drawing
software to letter is more time consuming. Free hand lettering should be done with ease.
27
Training followed by ongoing efforts will boost skill and style of lettering. Bad lettering marks
an otherwise good drawing.
Writing names, measurements, notes and other relevant information on a drawing is called
lettering. It's an integral part of a painting. However, a drawing can be made precise and clean.
The presentation is spoiled and often, bad lettering impairs the usefulness. Therefore, lettering
should be done correctly in a simple, legible and standardized design. This should be in a
basic and straightforward format, so that it can be done easily and efficiently.
Note: The use of drawing devices in lettering requires considerable time, and should therefore
be avoided. Careful and consistent practice can achieve productivity in the art of lettering.
Single-stroke letters: The Bureau of Indian Standards recommends one-stroke letters for
use in engineering drawing (IS: 9609-2001). They are the basic types of letters used in most
engineering drawings. The term single stroke does not indicate that the letter should be written
in a single stroke without raising the pencil. In addition, it means that the letter line thickness
should be as one stroke in the pencil. From left to right and vertical or inclined lines from top
to bottom, the horizontal lines of letters should be drawn.
Single-stroke letters are of two types:
a.
vertical
b.
inclined
Inclined letters lean to the right, the slope being 75° with the horizontal. The size of a letter is
described by its height. According to the height of letters, they are classified as:
(i)
Lettering 'A' (refer to Table 3.2 and Fig. 3.8)
(ii)
Lettering 'B' (refer to Table 3.3 and Fig. 3.8).
28
𝐇
Table 3.2 LETTERING A (𝐃 = )
𝟏𝟒
𝐇
Table 3.3 LETTERING B (𝐃 = )
𝟏𝟎
The height of the capital letter is divided into 14 components in the letter 'A' form, while
it is divided into 10 components in the letter 'B.' The height of the letters and numerals for
concept drawing can be chosen according to the drawing scale from 2.5, 3.5, 5 , 7, 10, 14 and
20 mm. The height-to-width ratio varies, but for most letters it is 6:5.
29
Letters are generally written in large letters. Various letter sizes are used for various
purposes.
The main titles are typically written in size between 6 and 8 mm, subtitles in size of 3
mm to 6 mm, whereas notes, statistics, etc. are written in sizes between 3 and 5 mm. The
drawing number is written in numerals from 10 to 12 mm in the title column. Fig. 3.4 shows
single-stroke vertical capital letters and Figures with approximate proportions (Bhatt, 2011).
Figure 3.4 Single-Stroke Vertical Capital Letter
Inclined capital letters and Figures are shown in Figure in one-stroke. 3.5. For
architectural sketches, the lower-case letters are normally employed. Lower case vertical and
inclined alphabets are shown in Fig. 3.6 and Fig. 3.7. The width of most letters is the same as
the height (Bhatt, 2011).
Figure 3.5 Single-Stroke Inclined Capital Letter
30
Figure 3.6 Single-Stroke Vertical Lower-Case Letter
Figure 3.7 Single-Stroke Inclined Lower-Case Letter
Figure 3.8 Lettering Proportions
The shape, pitch, scale, shade and spacing should be uniform in all letters. All letters
should be uniform in shape and slope in a drawing. Thin and light guidelines should first be
drawn for the conservation of uniformity of dimensions, and then letters can be made between
them. Each letter must have the same shade as the contours of the drawings, i.e. deeply
black.
31
H or HB pencil grade is therefore recommended for this reason. The spacing does not
always be equal between two characters. The letters should be so spaced that they don't look
too close or too distant.
When judging by the eye, the background areas should be kept approximately equal
between the letters. The distance between words must be at least equal to and compatible
with the height of the letters. See Fig. See Fig. 3.8.
This lettering should be done when read horizontally from the top, i.e. when the
drawing is seen from the lower side.
Both subtitles should be underneath the respective views, but not too close. Letters
should be underlined to make them more prominent, with the exception of the dimensional
Figures.
Gothic letters: Stems of single-stroke letters, if given more thickness, form what are known
as gothic letters. These are mostly used for main titles of ink-drawings. The outlines of the
letters are first drawn with the aid of instruments and then filled-in with ink. The thickness of
the stem may vary from 1/5 to 1/10 of the height of the letters. Fig. 3.9 shows the alphabet
and Figures in gothic with thickness equal to 1/7 of the height.
Figure 3.9 Stems of Single-Stroke Letters
32
Figure 3.10 Recommended Sequences for Making Single Stroke Alphabet
33
Assessment Task 3
Directions: Use the standard margins, border lines, etc. shown in Fig. 2.1 (a) and Fig. 2.1 (b)
and use the title block format in Fig. 2.3. Use A2 size sheet.
1. (Plate no. 6) Write freehand, in single-stroke vertical capital letters of 10 mm height, the
Laguna University Mission: All letters should intensely black.
2. (Plate no. 7) Write freehand, in single-stroke vertical lower-case letters of 10 mm height,
the Laguna University Vision: All letters should intensely black.
3. (Plate no. 8) Write freehand, in single-stroke inclined capital letters of 10 mm height, the
Department of Mechanical Engineering Mission: All letters should intensely black.
4. (Plate no. 9) Write freehand, in single-stroke inclined lower-case letters of 10 mm height,
the Department of Mechanical Engineering Vision: All letters should intensely black.
5. (Plate no. 10) Write freehand, in single-stroke vertical letters of 10 mm height, the following
paragraph:
“I am an Engineer. In my profession, I take deep pride. To it, I owe solemn obligations.
As an engineer, I pledge to practice integrity and fair dealing, tolerance and respect, and to
uphold devotion to the standards and dignity of my profession. I will always be conscious
that my skill carries with it the obligation to serve humanity by making the best use of the
Earth's precious wealth.
As an engineer, I shall participate in none but honest enterprises. When needed, my skill
and knowledge shall be given, without reservation, for the public good. In the performance
of duty, and in fidelity to my profession, I shall give my utmost.”
Note: letters should intensely black.
References:
Bhatt, ND., (2011) Engineering Drawing, Gujarat, India, 15th ed.
Venkata Reddy, K., (2008) Textbook of Engineering Drawing, Tirupati, India, 2nd ed.
34
MODULE 4
DIMENSIONING
Introduction
In addition to displaying the true form of an object, any drawing, whether of a
magnitude or a drawing by hand, must supply the exact length, width, height, the sizes and
locations of holes, grooves etc. and all other information relevant to the construction of that
object (Bhatt, 2011).
According to Bhatt (2011), the drawing of a part must also include details on the size
definition in addition to the full shape description. Which are given by the distances between
the surfaces, the position of holes, surface finish, material quality, etc. Such features are
represented in a drawing using shapes, symbols, figures and notes.
Dimensioning is used to describe an area such that the features of the component can
be identified in size and position. This module provides basic guidelines for good dimensional
action (Bhatt, 2011).
Learning Outcomes
At the end of this module, students should be able to:
1. Learn the basic rules for good dimensioning; and
2. Be able to correctly dimension engineering drawings.
35
Lesson 1. Dimensioning (Bhatt, 2011)
Types of dimensions
Two types of dimensions needed on a drawing are:
(i)
size or functional dimensions and
(ii)
location or datum dimensions (shown by letters F and L respectively).
The first shows measurements, in other words. Height, distance, height, depth, size etc.
Later shows the exact locations or positions of different building details within the piece. The
letter F is functional, while the letter F is non-functional.
Figure 4.1 Types of Dimensions
Dimensioning terms and notations
Dimension line (Fig. 4.2): Dimension line is a thin continuous line. It is terminated by
arrowheads touching the outlines, extension lines or center lines.
Extension line (Fig. 4.2): An extension line is also a thin continuous line drawn in extension
of an outline. (Formerly, the 8.1.S. had recommended that a gap of about 1 mm should be
kept between the extension line and an outline or object boundary.) It extends by about 3 mm
beyond the dimension line.
36
Arrowhead (Fig. 4.2): An arrowhead is positioned on each end of a line of measurements.
The point end impacts a contour, extension or middle line. The arrowhead scale will be equal
to the thickness of the contours. The arrowhead length should be approximately three times
its width. It is drawn freely with two strokes towards its pointing end. The gap between them
is completely filled. The Fig shows various styles of arrow heads. 4.3. 4. For engineering
design, the closed and filled arrowhead is commonly used. Remark (Fig. 4.2):
Note offers information on a particular task process. It is situated outside a view but adjacent
to the element. It is drawn so that it can be read from the bottom edge when the drawing is
shown.
Leader (Fig. 4.2): A leader or a pointer is a slim line connecting a note or a dimension Figure
to the function. One end of the leader ends in a flashpoint or a line. The arrowhead touches
the contour, while the point is within the contour of the body [Fig. 4.3 and Fig. 4.3 and Fig.
4.4].
At the bottom of the first or last letter of the note, the other end of the leader is
terminated in a horizontal line. The leader is never pushed vertically, horizontally or curved. It
is drawn to the line at a suitable angle of not less than 30 °. This is drawn radially when pointing
to a circle or arc. Common leaders should never be used for more than one function.
Figure 4.2 Leader
Figure 4.3 Arrowhead
37
Figure 4.4 Arrowhead
Placing of dimensions
The two systems of placing dimensions are:
(1) Aligned system and
(2) Unidirectional system.
Aligned system (Fig. 4.5): The orientation is perpendicular to the dimensional line in the
balanced framework so that it can be viewed from the bottom or from the right edge of the
drawing board. The measurements should be positioned near to the middle and above but
without the lines of dimension.
Fig 4.5 Aligned System
Fig 4.6 Unidirectional System
Unidirectional system (Fig. 4.6): All measurements are put in the unidirectional framework
to be read from the bottom of the drawing board. The lines are split at the center to insert the
measurements. This device is used primarily on large models, such as planes, cars and so
on, because reading measurements from the right-hand side is uncomfortable.
38
Unit of dimensioning
All measurements will be in millimeters to the extent practicable, omitting the mm
abbreviation. Even when measurements in millimeters are not convenient and another unit is
used, only dimensional Figures are written. Nevertheless, a footnote as 'all measurements
are in centimeters' is put in a prominent location near the heading mark. The dimensional
Figures (as mentioned above) should be from 3 mm to 5 mm in height. The decimal point in
a dimension should be very distinct and written according to the Figure's bottom line (Fig.
4.20). The decimal point must always precede a zero if the dimension is less than unity.
General rules for dimensioning (Bhatt, 2011)
(1) Dimensions should be performed in such a way that no further calculation or inference of
any dimension or direct measurement is required from the drawing.
(2) All dimensions should be given, but none more than once should be given.
(3) Where its use is more clearly seen, a dimension should be put on the image.
(4) Dimensions should be put outside the views so that they are simpler and easier to interpret
inside.
(5) It is necessary to avoid mutual crossing of dimensional lines and sizing between hidden
lines. Any other drawing line can be crossed by dimensional ones.
(6) Never can an outline or a middle line be used as a dimensional line. An extension line to
a middle line can be extended (Fig. 4.6).
(7) It is recommended to have synchronized dimensioning method.
Practical hints on dimensioning (Bhatt, 2011)
(1) Lines of proportions should be drawn at least 8 mm away from and from the outlines.
(2) Dimensions can be put in a series in one of two ways:
39
(i) Dimensioning of continuous chain or chains (Fig. 4.7): Dimensions are formed in a straight
line. Overall, outside the smaller measurements is placed. One of the smaller (most important)
dimensions is normally omitted.
(ii) Positive or parallel measurements (Fig. 4.8): from a specific base line all dimensions are
shown. This approach prevents cumulative error. This is a superior form.
(3) Smaller measurements should be put closer to the view, and larger so as not to cross the
lines of extension. The extension lines may be crossed (Fig. 4.9) or the outlines may be
crossed (Fig. 4.6).
Figure 4.7 Continuous Chain
Figure 4.9 Smaller Measurements
Figure. 4.8 Parallel Measurements
Figure 4.10 Arrowhead Outside
40
(4) When a number of parallel dimension lines are to be shown near each other, the
dimensions should be staggered (Fig. 4.9).
(5) Dimensions should be shown where the shape is easily identified.
(6) The arrowheads will usually be drawn within the dimensional characteristic limits. But if
the room is too small, it can be placed outside (Fig. 4.10). An arrowhead may also be replaced
with a circle. The dimension Figure may be written above the extended part of the dimension
line due to lack of space but, preferably, on the right (Fig. 4.10).
(7) The proportions of cylindrical sections in the views where they are used as rectangles
should be positioned as far as possible (Fig. 4.11). The diameter dimension should always be
followed by the symbol 0. The cylinder dimension should not be given as a radius.
Fig. 4.12 indicates various methods for dimensioning different circle sizes. Dimensions should
be shown in just one image, in another image the same dimension should not be replicated.
Holes in the view in which they appear as circles should be measured (Fig. 4.13). This should
be positioned by its central points.
All measurements for a particular operation, such as boiling hole diameter and depth (Fig.
4.11), or the threaded hole size and depth (Fig. 4.22), should be given in one view only (Bhatt,
2011).
Fig 4.11 Cylindrical Sections
Fig 4.12 Different Circle Sizes
41
In case of a large-size bore or a pitch circle, the dimension may be shown by a
diagonal diameter (Fig. 4.14). But (in aligned system) a dimension should not be placed
within 30° zone of the vertical center line as shown by the shaded space in Fig. 4.14 (Bhatt,
2011).
Fig 4.13 Holes
Fig 4.14 Diagonal Diameter
Holes on pitch circles when equally spaced should be dimensioned as shown in Fig.
4.14. When holes are not equally or uniformly spaced on the pitch circle, they should be
located by angles with one of the two main center lines (Fig. 4.15) (Bhatt, 2011).
Arcs of circles should be dimensioned by their respective radii. Dimension line for the
radius should pass through the center of the arc. The dimension Figure must be preceded by
the letter R. Fig. 4.16 shows different methods of showing the radii of arcs (Bhatt, 2011).
Fig 4.15 Holes On Pitch Circle
Fig 4.16 Radius
Fig 4.17 Square Section
42
(8) Letters SQ should precede the dimension for a rod of square cross-section (Fig. 4.17).
The word SPHERE should be placed before the dimension (radius R or diameter 0) of a
spherical part (Fig. 4.18).
(9) Angular dimensions may be given by any one of the methods shown in Fig. 4.19. (10) Fig.
4.20 shows a method of dimensioning a countersunk hole. The maximum diameter is also
sometimes given.
Fig 4.18 Sphere
Fig. 4.19 Angle
Fig. 4.20 Countersunk
(11) Methods of dimensioning a chamfer is shown in Fig. 4.21
Fig 4.21 Dimensioning a Chamfer
(12) Designation and size, along with the useful length must be given while dimensioning an
external screw thread (Fig. 4.22). In case of internal screw thread, in addition to the size and
type, the depth of the drilled hole before tapping must also be given (Fig. 4.23).
(13) Left-hand thread and multiple-start thread should be dimensioned as shown in Fig. 4.24
and Fig. 4.25 respectively.
(14) A slope or taper is defined as unit alteration in a specified length. The specified length is
measured along the base line in case of flat pieces and along the axis in case of shafts.
43
(15) Fig. 4.26 shows the method of indicating slope on a flat piece. It is written parallel to the
sloping line.
Flat taper =
H−h
L
=
1
20
Flat taper dimensioning (Fig. 4.22 – Fig. 4.25)
Fig. 4.22
Fig. 4.23
Fig. 4.24
Fig. 4.25
(16) The taper on a shaft is indicated along the center line and is accompanied by one or both
the diameters (Fig. 4.27).
Taper on diameter =
D−d
L
=
1
10
(17) Fig. 4.28 shows method of dimensioning for frustum. It is drawn obliquely but parallel to
each other.
Taper on diameter dimensioning (Fig. 4.22 – Fig. 4.25)
Fig. 4.26 Scale
Fig. 4.27 Slope
Fig. 4.28 Size
(18) Fig. 4.29 shows method of dimensioning chords, arcs and angles.
(19) Study carefully Fig. 4.30 for correct dimensioning. Incorrect dimensioning is shown by
cross (X) in the Figure.
44
Figure 4.29 Dimensioning Chords, Arcs and Angles
Figure 4.30 Correct and Incorrect Dimensioning
45
Assessment Task 4
Directions: Use the standard margins, border lines, etc. shown in Fig. 2.1 (a) and Fig. 2.1
(b) and use the title block format in Fig. 2.3. Use A2 size sheet.
1. (Plate no. 11) The orthographic views of the objects are drawn according to the Firstangle projection method to 1: 1 scale size and shown below. Insert dimensions.,
46
Directions: Use the standard margins, border lines, etc. shown in Fig. 2.1 (a) and Fig.
2.1 (b) and use the title block format in Fig. 2.3. Use A2 size sheet.
1. (Plate no. 13) For the object shown below, insert dimensions from the printed scales
below the objects.
References:
Bhatt, N.D., (2011) Engineering Drawing, Gujarat, India, 15th ed.
Venkata Reddy, K., (2008) Textbook of Engineering Drawing, Tirupati, India, 2nd ed.
47