Republic of the Philippines
BULACAN AGRICULTURAL STATE COLLEGE
Pinaod, San Ildefonso, Bulacan
Course Code & Title: ENSC 102 (COMPUTER-AIDED DRAFTING)
Sem. / School Year: 2nd Semester / SY 2021 – 2022
Prepared By: Engr. Gladys Ann S. Plaza
LEARNING GUIDE IN COMPUTER-AIDED DRAFTING
GENERAL OBJECTIVES
This lecture notes will enable the students to:
1. Define the terms related to computer-aided drafting systems;
2. Identify the important tools used to create technical drawings in CAD;
3. Create electronic drawings (e-drawing) using CAD; and
4. Appreciate the usefulness of the knowledge and skills in computer aided drafting as applied in
his/her professional development.
PART-I INTRODUCTION TO TRADITIONAL ENGINEERING DRAWING
INTRODUCTION
Engineering drawing known as the language of engineers is widely used means of
communication among the designer, engineers, draftsmen and craftsmen in the industry. The
translation of ideas into practice without the use of graphic language is really beyond
imagination. The word graphics means dealing with the expression of ideas by drawing lines or
curves on a surface. Like other languages, drawing is also a language that can be learned and
used like other languages. Basically, engineering drawing is the graphic language of engineers. It
is a graphic representation of thinking, planning and language of every technical person who
uses to communicate his ideas clearly to other engineers. Before starting manufacturing or
construction work, product to be developed or plan of housing society respectively is firstly
drawn on a rough paper. The purpose of this drawing is to define physical shape completely and
accurately of particular object by means of lines etc., regarding the object. In the age of
automation, engineering drawing has grown keeps and bounds. Without the fundamental
knowledge of technical drawing, a student would not be successful in an industry. Engineering
drawing has plenty of applications, especially in modern industries.
Role of Engineering Drawing
The ability to read drawing is the most important requirement of all technical people in
any profession. As compared to verbal or written description, this method is brief and more clear.
Some of the applications are: building drawing for civil engineers, machine drawing for
mechanical engineers, circuit diagrams for electrical and electronics engineers, computer
graphics for one and all.
Types of Engineering Drawing
1. Artistic Drawing: The drawing representing any object or idea which is sketched in free hand
using imagination of artist and in which proper scaling and dimensioning is not maintained is
called an artistic drawing. Example: Painting, Posters, artsetc.
Republic of the Philippines
BULACAN AGRICULTURAL STATE COLLEGE
Pinaod, San Ildefonso, Bulacan
Figure 1. Artistic drawing
2. Technical/Engineering Drawing: can be defined as a graphical language used by engineers
and other technical personnel associated with the engineering profession which fully and clearly
defines the requirements for engineered items.
Figure 2. Technical drawing
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BULACAN AGRICULTURAL STATE COLLEGE
Pinaod, San Ildefonso, Bulacan
Difference Between Artistic and Engineering Drawing
Types of Technical Drawings
Technical drawings are based on the fundamental principles of projections. A projection
is a drawing or representation of an entity on an imaginary plane or planes. This projection
planes serves the same purpose in technical drawing as is served by the movie screen. A
projection involves four components:
1. The actual object that the drawing or projection represents
2. The eye of the viewer looking at the object
3. The imaginary projection plane
4. Imaginary lines of sight called Projectors
The two broad types of projections, both with several subclassifications, are parallel projection
and perspective projection.
Parallel Projection
Parallel Projection is a type of projection where the line of sight or projectors are parallel and are
perpendicular to the picture planes. It is subdivided in to the following three categories:
Orthographic, Oblique and Axonometric Projections.
Orthographic projections: are drawn as multi view drawings, which show flat
representations of principal views of the subject.
Oblique Projections: actually show the full size of one view.
Axonometric Projections: are three-dimensional drawings, and are of three different
varieties: Isometric, Dimetric and Trimetric.
Figure 3. Orthographic multi view drawing
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BULACAN AGRICULTURAL STATE COLLEGE
Pinaod, San Ildefonso, Bulacan
Figure 4. Oblique drawing
Figure 5. Axonometric drawing
Perspective Projection
Perspective projections are drawings which attempt to replicate what the human eye actually sees
when it views an object. There are three types of perspective projections: Onepoint, Two-point
and Three-point Projections.
Republic of the Philippines
BULACAN AGRICULTURAL STATE COLLEGE
Pinaod, San Ildefonso, Bulacan
Figure 6. Perspective drawing
Purpose of Technical Drawings
To appreciate the need for technical drawings, one must understand the design process.
The design process is an orderly, systematic procedure used in accomplishing a needed design.
Any product that is to be manufactured, fabricated, assembled, constructed, built, or
subjected to any other types of conversion process must first be designed. For example, a house
must be designed before it can be built.
Application of Technical Drawing
Technical drawings are used in many different applications. They are needed in any
setting, which involves design, and in any subsequent forms of conversion process. The most
common applications of technical drawings can be found in the fields of manufacturing,
engineering and construction.
For instance, Surveyors, civil engineers, sanitarians use technical drawings to document
such works as the layout of a new subdivisions, or the marking of the boundaries for a piece of
property. Contractors and construction personnel use technical drawings as their blue prints in
converting architectural and engineering designs in to reality.
Chapter I: DRAWING TOOLS/EQUIPMENTS AND THEIR USE
To record information on paper instruments and equipments are needed. Engineering
drawing is entirely a graphic language hence instruments are essentially needed. Drawing must
be clear, neat and legible in order to serve its purpose. Hence it is extremely important for
engineers to have good speed, accuracy, legibility and neatness in the drawing work.
All drawings are made by means of various instruments. The quality of drawing depends to a
large extent on the quality, adjustment and care of the instruments.
1. Drawing Paper
Drawing paper is the paper, on which drawing is to be made. All engineering drawings
are made on sheets of paper of strictly defined sizes, which are set forth in the U.S.S.R standards.
The use of standard size saves paper and ensures convenient storage of drawings. Now a day, A3
and A4 are the most commonly used paper sizes. The U.S.S.R standard establishes five preferred
sizes for drawings as tabulated bellow:
Republic of the Philippines
BULACAN AGRICULTURAL STATE COLLEGE
Pinaod, San Ildefonso, Bulacan
Description of the size of drawing paper
Title block is a rectangular frame that is located at the bottom of the sheet. It is
recommended that space should be provided in all title blocks for such information as description
of title of the drawing, dates, designer (drawer), and name of enterprise or educational institute,
size (scale)
Figure 1. Sample Title block figures
figure
Republic of the Philippines
BULACAN AGRICULTURAL STATE COLLEGE
Pinaod, San Ildefonso, Bulacan
2. Triangles (setsquares)
They are used to construct the most common angles (i.e. 30° , 45° , 60° ) in technical
drawings. The 45° x 45° and 300° x 60° triangles are the most commonly used for ordinary
work.
Figure 2. triangles or set squares
3. T- square
It is used primarily to draw horizontal lines and for guiding the triangles when drawing
vertical and inclined lines. It is manipulated by sliding the working edge (inner face) of the head
along the left edge of the board until the blade is in the required position.
Figure 3. Tee-Square
4. French curve
It is used to draw irregular curves and arcs in the drawing. It is made of transparent
plastic material and available in different shapes and sizes. Its edge must be perfectly smooth.
The shape varies according to the shape of irregular curve.
Figure 4. French Curve
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BULACAN AGRICULTURAL STATE COLLEGE
Pinaod, San Ildefonso, Bulacan
5. Protractor
It is used for laying out and measuring angle.
Figure 5. Protractor
6. Circle Master
Circle master is used to draw of small size circles which are not possible to draw by
compass. It consists of different size of circles. It is also used to increase the speed of drafting. It
is made of plastic material in various sizes as shown in Fig. 6.
Figure 6. Circle Master
7. Scale (ruler)
A number of kinds of scales are available for varied types of engineering design.
Figure 7. Scale (ruler)
8. Pencil
The student and professional man should be equipped with a selection of good, well-
sharpened pencil with leads of various degrees of hardness such as: 9H, 8H, 7H, and 6H (hard);
5H & 4H (medium hard); 3H and 2H (medium); and H& F (medium soft). Standards for line
quality usually will govern the selection. For instance;
Republic of the Philippines
BULACAN AGRICULTURAL STATE COLLEGE
Pinaod, San Ildefonso, Bulacan
♦ 6H is used for light construction line.
♦ 4H is used for re-penciling light finished lines (dimension lines, center lines, and invisible
object lines)
♦ 2H is used for visible object lines
♦ F and H are used for all lettering and freehand work.
Figure 8. Pencil
9. Compass
It is used to draw circles and arcs both in pencil and ink. It consists of two legs pivoted at
the top. One leg is equipped with a steel needle attached with a screw, and other shorter leg is,
provided with a socket for detachable inserts.
A bow compass is
The large compass is used for drawing small
used to draw circles circles and arcs up to
and circular arcs. It 25 mm diameter. This
consists of two legs compass is used by
pivoted at the top. A structural engineers
pointed needle is fitted when a large number
at the lower end of one of small circles of the
leg, while the other leg same diameter are to
a pencil lead is be drawn.
inserted.
Large Compass Bow Compass
Figure 9
10. Divider
Used chiefly for transferring distances and occasionally for dividing spaces into equal
parts. i.e. for dividing curved and straight lines into any number of equal parts, and for
transferring measurements.
The large divider is
used for dividing
The bow divider is
straight lines and
used for dividing small
circles into desired
circles or arcs and
number of equal parts.
number of small equal
It is also used for
distances.
transferring distance
from one part of
drawing to another
part of the drawing. It
has two legs, with
steel points at both the
lower ends instead of
pencil point.
Large Divider Bow Divider
Figure 10
Republic of the Philippines
BULACAN AGRICULTURAL STATE COLLEGE
Pinaod, San Ildefonso, Bulacan
11. Drawing Board
A drawing board is a flat, smooth board on which to attach paper for making drawings or
designs. Traditionally they are made of timber however modern day boards are constructed out
of plastic. The board can be purchased in A4 size although they are more commonly found in
schools as an A3 size format.
Figure 11. Drawing Board
12. Eraser
Used for erasing or rubbing out unwanted pencil lines on your drawings. They are often
used with the aid of an erasing shield.
13. Sharpener and Sand Paper Pad
A pencil sharpener is used to sharpen a pencil.
Sharpener of good quality should be used which can sharpen to at least 10 millimeter
lead. After this, sandpaper pad needs to be used to make its shape better.
The use of sand paper pad should be done frequently to keep the required shape of the
pencil end.
14. Scotch Tape or Drawing Pin.
Transparent Tape is used for sticking the drawing sheet on the drawing board, which is
known as Scotch Tape.
This tape is applied at the corners of the sheet.
Drawing pins can also be used for sticking the sheet. However, the drawing pins spoil the
surface of the drawing board.
That is why the pins are not preferred.
Republic of the Philippines
BULACAN AGRICULTURAL STATE COLLEGE
Pinaod, San Ildefonso, Bulacan
EXERCISE 1
1. Explain in your own words the sentence; “engineering drawing is the graphic language of
engineers.” it must be compose of 250 words.
2. What is graphic communication?
3. Explain the different application of technical drawing.
4. Name the different types of instruments used in engineering practice.
5. How will you keep your drawing neat and clean?
6. Name the different grade of pencils used in engineering drawing in tabulated form.
7. Why do we need a title block in an engineering drawing?
