Chapter 01 Introduction To Engineering Drawing

8/11/2019 Chapter 01 Introduction To Engineering Drawing

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Chapter 1Overview of an

Engineering Drawing


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TOPICS

Drawing standards

Projection methods

Orthographic projection

Graphics language

Engineering drawing


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TOPICS

Traditional Drawing Tools

Freehand Sketching

Lettering


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GRAPHICSLANGUAGE


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1. Try to write a description ofthis object.

2. Test your written description

by having someone attemptto make a sketch from yourdescription.

Effectiveness of Graphics Language

The word languages are inadequate for describing thesize , shape and features completely as well asconcisely.

You can easily understand that


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Graphic language in engineering application usel ines to represent the surfaces , edges and con tou r s

of objects.

A drawing can be done using freehand , in s t rumen ts or co m p u te r methods.

Composition of Graphic Language

The language is known as drawing or draf t ing .


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Freehand drawing The lines are sketched without using instruments other

than pencils and erasers.

Example


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Instrument drawing Instruments are used to draw straight lines, circles, and

curves concisely and accurately. Thus, the drawings areusually made to scale.

Example


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Computer drawing The drawings are usually made by commercial software

such as AutoCAD, solid works etc.

Example


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EngineeringDrawing


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Elements of Engineering Drawing

Engineering drawing are made up of graphics lang uageand wo rd langu age .

Graphicslanguage

Describe a shape(mainly).

Wordlanguage

Describe size, location and

specification of the object.


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Basic Knowledge for Drafting

Graphics

language

Word

language

Linetypes

Geometricconstruction Lettering

Projectionmethod


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PROJECTIONMETHOD


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PROJECTION METHOD

Perspective

Oblique Orthographic

Axonometric Multiview

Parallel


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PROJECTION THEORY

The projection theory is based on two variables:

1) Line of sight

2) Plane of projection (image plane or picture plane)

The projection theory is used to graphically represent

3-D objects on 2-D media (paper, computer screen).


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Plane of projection is an imaginary flat plane whichthe image is created.

The image is produced by connecting the points where

the LOS pierce the projection plane.

Paral lel pro ject ion Persp ect ive pro ject ionPlane of projection Plane of projection


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Disadvantage ofPerspective Projection

Perspective projection is n o t

used by engineer for manu-

facturing of parts, because

1) It is difficult to create.

2) It does not reveal exact

shape and size.Width is distorted


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OrthographicProjection


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5

Orthographic projection is a parallel projection techniquein which the parallel lines of sight are perpendicu lar to the

projection plane

MEANING

Object views from top

Projection plane

1

2

3

4

5 1 2 3 4


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ORTHOGRAPHIC VIEWOrthograph ic v iew depends on relative position of the object

to the line of sight.

Two dimensions of anobject is shown.

Three dimensions of an object is shown.

Rotate

Tilt

More than one view is neededto represent the object.

Mult iv iew drawing

Axo nom et r ic d rawing


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Orthographic projection technique can produce either

1. Mult iv iew drawing

that each view show an object in two dimensions.2. Axo nom et r ic d rawing

that show all three dimensions of an object in one view.

Both drawing types are used in technical drawing forcommunication.

NOTES

ORTHOGRAPHIC VIEW


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Axonometric (Isometric) Drawing

Easy to understand

Right angle becomes obtuse angle.

Circular holebecomes ellipse.

Distortions of shape and size in isometric drawing

Advantage

Disadvantage Shape and angle distortion

Example


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Drawing Standard


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Introduction

Standards are set of rules that govern how technicaldrawings are represented.

Drawing standards are used so that drawings conveythe same meaning to everyone who reads them.


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ISO International S tandards Organization

Standard Code

ANSI American National S tandard InstituteUSAJIS J apanese Industrial S tandardJapan

BS British S tandardUK

AS Australian S tandard AustraliaDeutsches Institut f r NormungDINGermany

Country Code Full name

. Thailand


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Partial List of Drawing Standards

. 210 2520 :

. 440 .1 2541 1

. 446 .4 2532

. 1473 2540

Code number Contents

: http://library.tisi.go.th/data/lib_resources/pdf/catalog-online49/tis/02_ICS.pdf


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Partial List of Drawing Standards

JIS Z 8311 Sizes and Form at of Draw ing s

JIS Z 8312 Line Convent ions

JIS Z 8313 Letter ing

JIS Z 8314 Scales

JIS Z 8315 Projection methods

JIS Z 8316 Presentation of Views and SectionsJIS Z 8317 Dimensioning

Code number Contents


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Drawing Sheet

Trimmed paper ofa size A0 ~ A4.

Standard sheet size (JIS )

A4 210 x 297 A3 297 x 420 A2 420 x 594

A1 594 x 841 A0 841 x 1189

A4

A3

A2

A1

A0(Dimensions in millimeters)


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Drawing space Drawingspace

Title block

d

d

c

c

cBorderlines

1. Type X (A0~A4) 2. Type Y (A4 only)

Orientation of drawing sheet

Title block

Sheet size c (min) d (min)

A4 10 25 A3 10 25 A2 10 25 A1 20 25

A0 20 25


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Drawing Scales

Scale is the ratio of the linear dimension of an elementof an object shown in the drawing to the real linear

dimension of the same element of the object.

Size in drawing Actual size

Length, size

:


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Drawing ScalesDesignation of a scale consists of the word SCALE

followed by the indication of its ratio , as follow

SCALE 1:1 for full size

SCALE X:1 for enlargement scales (X > 1)SCALE 1: X for reduct ion scales (X > 1)

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.


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Basic Line Types

Types of Lines AppearanceName according

to application

Continuous thick line Visible line

Continuous thin line Dimension lineExtension line

Leader line

Dash thick line Hidden line

Chain thin line Center line

NOTE : We will learn other types of line in later chapters.


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Visib le l ines represent features that can be seen in thecurrent view

Meaning of Lines

Hidden l ines represent features that can not be seen in

the current view

Center lin e represents symmetry, path of motion, centers

of circles, axis of axisymmetrical parts

Dim ens ion and Extens ion l ines indicate the sizes and

location of features on a drawing


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Example : Line conventions in engineering drawing


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TraditionalDrawing Tools


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DRAWING TOOLS


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3. Adhesive Tape 4. Pencils

H or HB for thick line

4H for thin line

DRAWING TOOLS


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5. Sandpaper 6. Compass

DRAWING TOOLS


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7. Pencil Eraser 8. Erasing Shield

DRAWING TOOLS


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9. Circle Template 10. Tissue paper

DRAWING TOOLS


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11. Sharpener 12. Clean paper

DRAWING TOOLS


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ABCDEFGHIJKLMNOPQRSTUVWXYZABCDEFGHIJKLM

NOPQRSTUVWXYZABCDEF

ABCDEFGHIJKLMNOPQRST

UVWXYZABCDEFGHIJKLMNOPQRSTUVWXYZABCDEF

Lettering


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Text on DrawingsText on engineering drawing is used :

To communicate nongraphic information.

As a substitute for graphic information, in those instancewhere text can communicate the needed information

more clearly and quickly.

Unifo rmi ty - size- line thickness

Legib i l i ty - shape- space between letters and words

Thus, it must be written with

l


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Example Placement of the text on drawing

Dimension & Notes

NotesTitle Block


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Basic Strokes

Straight Slanted CurvedHorizontal

1 1 2

3

Examples : Application of basic stroke

I letter A letter 1

2

3

4 5

6

B letter


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Suggested Strokes Sequence

Straight lineletters

Curved lineletters

Curved lineletters &Numerals

Upper-case letters & Numerals


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Stroke Sequence

I LT

F

E H


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N M K Z

Y A

Stroke Sequence

4


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OQ C G

Stroke Sequence


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S k S


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6

8 9

0 Stroke Sequence

S 3


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S k S


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Stroke Sequencev w x k

z

S k S


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Stroke Sequence j y f

r

t

S k S


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Stroke Sequencec o a b

d p q e

St k S


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Stroke Sequenceg n m h

u s

W d C iti


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Word CompositionLook at the same word having different spacing between letters.

JIRAPONGJ I GOR NP A

Which one is easier to read ?

A) Non-uniform spacing

B) Uniform spacing

Word Composition


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Word Composition

JIRAPONG \ / \ | )( ) | ( |

Space between the letters depends on the contour of

the letters at an adjacent side.

Spacing

Contour | | | | General conclusions are:

Good spacing creates approximately equal b ack g ro u n d

area between letters.

Space between Letters


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1. Straight - Straight

2. Straight - Curve

3. Straight - Slant

4. Curve - Curve




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6. Slant - Slant5. Curve - Slant

7. The letter L and T

slant slant

slant

straight


Example : Good and Poor Lettering


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GOOD

Not uniform in style.

Not uniform in height.

Not uniformly vertical or inclined.

Not uniform in thickness of stroke.

Area between letters not uniform.

Area between words not uniform.

Example : Good and Poor Lettering

Sentence Composition


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Leave the space between words equal to the spacerequires for writing a letter O.

Example

Sentence Composition

ALL DIMENSIONS ARE INMILLIMETERS

O O OO UNLESS

OTHERWISE SPECIFIED.O


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FreehandSketching

Straight Line


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Straight Line

1. Hold the pencil naturally.

2. Spot the beginning and end points.

3. Swing the pencil back and forth between the points, barely

touching the paper until the direction is clearly established.

4. Draw the line firmly with a free and easy wrist-and-arm

motion


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Horizon tal l ine Vertic al l ine


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Nearly vert ic alinc l ined l ine

Nearly h or izo n talinc l ined l ine

Small Circle


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Small CircleMethod 1 : Starting with a square

1. Lightly sketching the square and marking the mid-points.

2. Draw light diagonals and mark the estimated radius.

3. Draw the circle through the eight points.

Step 1 Step 2 Step 3


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Large Circle


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1. Place the little finger (or pencil s tip) at the center as a

pivot, and set the pencil point at the radius-distance fromthe center.

2. Hold the hand in this position and rotate the paper.

Large Circle

Arc


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ArcMethod 1 : Starting with a square

Method 2 : Starting with a center line

Steps in Sketching


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Steps in Sketching

1. Block in main shape.

2. Locate the features.

3. Sketch arcs and circles.

4. Sketch lines.

E l


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Example

Chapter 01 Introduction To Engineering Drawing

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