COLLEGE OF ENGINEERING AND INDUSTRIAL TECHNOLOGY

(BIT Department)

MODULE WEEK 1 & 2

in
DRAWING 101

PREPARED BY:
MARIN DEXTER L. EJAR
ELVIR B. DADOR
ALFRED D. GALLO
INSTRUCTOR
I. OVERVIEW

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September 18, 2020
 TECHNICAL DRAWING & SKETCHING
A technical drawing has all the information for manufacturing a part or welding and building
an assembly. The info includes dimensions, part names and numbers, etc. So once a
manufacturing engineer gets the drawing, he can start the production process without a second
thought.
First, we have to pause for a second and address our own customers here to avoid confusion.
The drawings you submit for instant pricing and manufacturing in our system do not need any
of this. The same applies to 3D models. CAD files and drawings made according to our
design tips include all the necessary information for making your product. The only time we
ask for a drawing is if you want to specify tolerances.
Still, knowing all the rules and basics of formatting is an absolute must in the industry, as
traditional manufacturing companies still need detailed drawings.

A few decades ago, you would have had to sit down at a drawing board covered with papers
of different size, rulers, callipers, etc. Today, all these instruments are still good for manual
drafting but no contemporary manufacturer really wants such drawings.
Why? Because most of the machinery uses CNC systems that can read the information
straight from the files and produce a cutting program accordingly. Drawings done by hand
would just add a lot of manual work for manufacturing engineers.
So, we are left with only one option really – every engineer should use CAD (computer aided
design) software because of its many advantages.
You can, of course, use CAD for making drawings from scratch. But the easier option is to
first make a 3D model and create the drawings from that, as the programs generate the views
with only a few clicks. All you need to do is add the dimensions. Having models also makes
updating the drawings for revisions simple.1

BLUEPRINT READING AS A UNIVERSAL LANGUAGE

Blueprints provide a universal language by which all information about an object is

furnished to the craftspeople, technicians, designers, assemblers, machine operators, and
programmers, as well as after-market repairs and maintenance persons. Blueprint reading
refers to the process of interpreting a drawing. An accurate mental picture of how the
object will look when completed can be formed from the information presented. Training
in blueprint reading includes developing the ability to visualize various manufacturing
and fabricating processes required to make a part and to apply the basic principles of
drafting that underlie the use of different lines, surfaces, and views. The training also
includes how to apply dimensions, take measurements, and visualize how the inside of a
part or mechanism looks. An understanding of universal measurements and other
standards, symbols, signs, and techniques the draftsperson/designer uses to describe a
part, unit, or mechanism completely must be developed. Technicians also develop
fundamental skills in making sketches so that data relating to dimensions, notes, and
other details needed to construct or assemble a part can be recorded on a sketch.

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September 18, 2020
 II. CONTENT
UNIT 1- BASES for BLUEPRINT READING and SKETCHING

1.1 -COMMON ELEMENTS IN DRAFTING

1.2 -INDUSTRIAL PRACTICES RELATING TO DRAWINGS
1.3 -DRAWING STORAGE PROCEDURE
1.4 –HARDCOPY and SOFTCOPY DRAWING

COMMON ELEMENTS IN DRAFTING

Technical drawing reveals that a part or an assembly of many parts must

be clearly and accurately represented by applying principles, techniques, and other
common elements of drafting, as follows:
shape and details of an object.
■ Dimensions that give the size and location of parts, shapes, and assemblies.
■ Sections that are used to expose internal construction details when an
object is cut apart by imaginary cutting planes.
■ Processes that are represented by symbols and notes for purposes of
identifying how each part is to be produced.
■ Geometric positioning that deals with placing and accuracy of geometric
objects in relationship to one another.
■ Notes and other non-graphical information clearly lettered (printed).
■ Tolerances that deal with accuracy related to form and size and position of
finished surfaces, where high precision is required.
■ Materials that are used for making parts, including information about
weight, strength, and hardness.
■ Computer-aided drafting (CAD) applications, where appropriate.
■ Technical sketching techniques for preparing line and form engineering
and technical sketches to complement precise engineering drawings.

INDUSTRIAL PRACTICES RELATING TO DRAWINGS

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 Drawing Reproduction Processes
Traditionally, a blueprint of an original drawing, which may be made on high-
quality paper, vellum, and acetate or polyester film, is produced by exposing the drawing
to a strong light source. Some of the light is held back by the drawn lines as it passes
through a transparent tracing onto a sensitized blueprint paper. After exposure, the
blueprint paper is passed through a developer fluid, washed by water, moved through a
fixative (to set the color), rewashed, and dried. This blueprint (except for slight shrinkage
during the drying stage) is an exact duplicate but in negative form. The term blueprint
originally referred to a blue and white reproduction of a drawing.

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September 18, 2020
 Today, it is used loosely in modern industrial language to include any type
of reproduction of a technical drawing, including computer-created ones. The highest
quality reproductions are made by plotters of various types: the flatbed plotter that holds
the paper (usually A-size or B-size) on a flat surface while a pen moves in two directions;
a drum plotter where the paper is attached to a rotating drum producing horizontal (“X”
axis) lines as a pen moves across the drum to reproduce vertical (“Y” axis) lines; or a
multigrip plotter that uses small rubber rollers to grip the paper at the edges, as opposed
to having the paper attached to the circumference of the drum. Simultaneous moving of
the drum and the pen on both of these produces curves and angle lines. The size of the
paper used in the drum plotter is limited by the width and the circumference of the drum,
which can be designed to use up through E-size or AO drawings. Today, most plotters
operate by commands from a computer. They can hold any number of pens up to 20 and
produce very accurate continuous line drawings with varying lineweight and color.
Printers are also used to reproduce drawings. They are generally less expensive than
plotters but are not as accurate because they can only simulate lines by printing a closely
spaced series of dots. Another method of reproduction known as diazo continues to be
popular. This process projects light through the original drawing, which is in direct
contact with the recipient paper or transparency. That paper is then developed with an
ammonia process to show the image, usually in black, brown, or blue. A variety of paper
weights and finishes as well as transparencies can be used in diazo. Copying machines,
similar to ones used for typical office copying, have also been designed to handle
blueprints and engineering prints of varying sizes. There are several advantages to these
machines—they are relatively inexpensive, they do not require coated copy materials or
chemicals, and the size of the drawing can be enlarged or reduced as desired. Another
style of copy machine is also used. It uses a wide-bed page scanner coupled with a wide
format printer. In this type of copy system, resolution is limited to that of the scanner,
typically 300 dots per inch. Typical wide-bed printer resolution is around 1200 dots per
inch. This means that the smallest line the printer can create is 0.00083.

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 Drawing Storage Procedures

Original manually created drawings are seldom sent to the shop, job site, or
laboratory. Instead, exact reproductions (called blueprints or whiteprints) are made of the
original. Duplicate copies are usually distributed among all individuals who are involved
in planning, manufacturing, assembling, or other work with a part or unit. The original
drawings are filed for record purposes and for protection. The options available for
storage of drawings and blueprints have increased as technology has advanced.
Microfilm has been one of the most widely used procedures for many years and is still
used in some places today. In this method, a greatly reduced photographic reproduction is
made on film and then mounted into cardboard aperture cards. These cards are easy to
file and keep track of. Many feel that they are also more durable. Blueprints are also
saved in special storage devices, including flat-drawer files, files designed for vertical
hanging, or tubes. Drawings stored in these ways must also be available for rapid and
convenient retrieval; therefore, prints are often folded and stored in standard office file
cabinets. If properly organized, this method does provide rapid retrieval and security. For
many companies, the preferred storage method is electronic, whether the drawing is
produced by hand or by CAD (Computer Aided Drafting). With CAD, the drawing can
be saved directly to a disk or it can be produced as hardcopy (blueprint) by one of several
types of printers. Scanners of various types can be used to convert handmade drawings
into computer files for disk storage. Computer files can be stored on a number of
different types of media. Common electronic storage media include USB flash drives,
3.5’’ floppy disks, hard drives, optical disks, and magnetic tape. Generally, when a
drawing is being edited, it is saved frequently to a hard drive located on a network server.
A large company will have two network servers: a primary server and a backup server.
Companies typically prefer documents to be saved on the server, not on the user’s
computer hard drive. Hard drive failure on individual computers is common and costly,
so companies store the information on the servers. Adjustments can be made to the
drawing by sketching the comments. The drawing can then be scanned back into the
computer and be sent back to the original draftsperson. The comments could then be
taken into account in the revised CAD file. Some consider electronic storage to be
superior to former methods because it reduces deterioration and the possibility of loss.
Also, when drawings are saved as hard copies (prints), there is inevitable wear and tear
on them, which compromises the quality of any reproduction. Drawings saved
electronically can be consistently reproduced with the same quality. It is also possible to
revise and correct drawings which have been saved on magnetic media (magnetic tape,
hard drives). However, disks and computer systems can develop problems and the
longevity of magnetic media or optical disks has not been proven; therefore, there
continues to be a need for a choice.

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 Hardcopy and Softcopy Drawings
The term blueprint or print identifies drawings that may be produced by
drafting room techniques or are computer-generated. Blueprint reading traditionally
involves the physical handling of a sheet on which a drawing is reproduced, but it also
refers to drawings as they appear on computer screens. The latter is called softcopy. The
drawing sheet is sometimes referred to as hardcopy and is a permanent copy of a
drawing. Hardcopy may be produced on conventional blueprinting equipment or it may
be computer-generated. Drawings in hardcopy form may be reproduced in one color or
an assortment of colors. CAD/CAM Some industries tie their engineering and
manufacturing departments together using a CAD/ CAM linkup over a computer
network. CAM stands for computer-aided manufacturing. In this process, the drafting
department designs a product on a computer. After completion, the drawing is converted
to coordinate data and then stored. Additional software called a post processor then
converts the stored coordinate data into a usable format for the machines in the
manufacturing department. Hardcopy is not produced unless someone needs to study the
drawing away from a computer terminal.

CAD/CAM Some industries tie their engineering and manufacturing

departments together using a CAD/ CAM linkup over a computer network. CAM stands
for computer-aided manufacturing. In this process, the drafting department designs a
product on a computer. After completion, the drawing is converted to coordinate data and
then stored. Additional software called a post processor then converts the stored
coordinate data into a usable format for the machines in the manufacturing department.
Hardcopy is not produced unless someone needs to study the drawing away from a
computer terminal.

TECHNICAL INFORMATION SUPPLIED ON DRAWINGS

The positive form blueprint of the guide pin

■ Name of the part (guide pin)
■ Quantity needed (6)
■ Drawing number (BP–1)
■ Dimensional tolerance (± 1/64’’)
■ Material (cold drawn steel)

UNIVERSAL SYSTEMS OF MEASUREMENT

Drawings contain dimensions that identify measurements of straight and curved
lines, surfaces, areas, angles, and solids. Linear or straight line measurements between
two points, lines, or surfaces are most widely used. Every linear measurement begins at a
particular reference point and ends at a measured point.

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September 18, 2020
 The straight line distance between these two points is the line of measurement. It
represents the actual required dimension and is referred to as the basic size. A basic size
is sometimes represented on a drawing by this symbol. The basic size is enclosed within
the symbol as, for example, 1.625. The degree of accuracy to which a part is to be
machined, fitted, formed, or assembled relates to its basic size.

Basic Units of Linear Measurement

Dimensions appear on drawings in one or a combination of two different units of

measurement, as in the case where inch and metric units are used together. Customary
inch (British–United States standard) dimensions are given as fractional parts of an inch
or as decimal inch values. The inch is subdivided into equal parts, called fractional parts
or decimal (mils) parts. Figure 1-9A illustrates commonly used fractional parts of an inch
(1/640, 1/320, 1/160, 1/80, 1/40, and 1/20). The graduations on the steel rule in Figure 1–
9B show decimal parts of an inch (.0100 [ten mils], .0500 [fifty mils], .1000 [100 mils],
and .5000 [500 mils].

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 Metric Linear Units of Measurement

Standard units of linear measurement in the SI metric system are all related to the
meter. For most practical purposes, the meter is equal to 39.37 inches. Metric dimensions
are generally given on a drawing in millimeters, as a multiple of the meter. Common
steel rules are graduated in whole and half millimeters, as shown in Figure 1–10. The
millimeter (mm) is the SI metric linear unit of measurement for engineering drawings.
Conversion tables are readily available to change a dimension in one system to a
mathematical equivalent in the second system.

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 III. EVALUATION

Name: _________________________________ Course /Year/Section_________

Date: _______________ Score: ______________________

1. Name one difference between picture drawings or photographs and a technical

drawing of an object.
__________________________________________________________________
2. Tell briefly why blueprints provide a universal language.
_________________________________________________________________
3. Name two organizations that develop drafting standards.
A _________________________________________________________________
B _________________________________________________________________

4. List three common elements of drafting that are used to produce technical drawings.
A _________________________________________________________________
B _________________________________________________________________
C__________________________________________________________________

5. State one reason why printers are not as accurate as plotters for reproducing technical
drawings.
___________________________________________________________________

6. Name two reproduction methods other than plotters and printers.

A. _________________________________________________________________
B._________________________________________________________________

7. Provide two advantages of disk storage over storage of original drawings on paper.
A _________________________________________________________________
B_________________________________________________________________

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8. Explain the difference between hardcopy and softcopy.
__________________________________________________________________

9. Name the end points to every linear measurement.

____________________________________________________________________

10. Describe what the term “line of measurement” means.

____________________________________________________________________

11. Tell what function a basic size dimension serves.

___________________________________________________________________

12. Briefly explain how an off-site computer can be used to modify a drawing held at
another computer location.
___________________________________________________________________

13. Name the two major linear measurement systems.

A _________________________________________________________________
B_________________________________________________________________

14. Give an example of a fractional part of the basic unit of measurement in each system.
A _______________________________________________________________
B ________________________________________________________________

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September 18, 2020