Engineering Drawing

Chapter 1 Introduction

Contents Engineering drawing Drawing standards Drawing sheet Scale Lettering Line types

Engineering Drawing The words of the language, as they are written or spoken, do not seem to play any role in my mechanism of thought. The psychical entities which seem to serve as elements in thought are certain signs and more or less clear images which can be “voluntarily” reproduced and combined--this combinatory play seems to be the essential feature in productive thought before there is any connection with logical construction in words or other kinds of signs which are communicated to others

--Albert Einstein Contents

Effectiveness of Graphic Language 1. Try to write a description of this object. 2. Test your written description by having someone attempt to make a sketch or visualize from your description. You can easily understand that …

The word language is inadequate for describing the size,

shape and features completely as well as concisely.

Graphic Language in Engineering Drawing “Engineering drawing” or “blueprint” uses lines to represent the features of an object. Features of an object are surface (include plane) and edge. Surface Edge

Ways to Create an Engineering Drawing A drawing can be created in 3 ways 1. Freehand sketch

2. Using typical drawing instruments 3. Using a computer

Create a Drawing : Freehand sketch The lines are drawn using only pencil and erasers on a blank or grid paper.

Example

Pictorial sketch

Orthographic sketch

Create a Drawing : Using instruments Drawing instruments are used to draw straight lines, circles, and curves concisely and accurately. Drawings are usually made to scale. Example

Create a Drawing : Using a computer Computer aided drafting (CAD) software is used. Example

2D drawing

Solid modeling

Elements of a Drawing A clear and precise engineering drawing requires both graphics and word languages.

Graphics language Describe a shape (mainly).

Word language Describe an exact size, location and specification of the object.

Text on drawings : Example Dimensions & Notes

General notes

Title block

Knowledge and Skills Require Engineering Drawing Word language

Graphics language Geometric construction Using line types

Projection method

Dimensions & Notes

Visualization

Visualization is the ability to mentally picture things that do not exists. Contents

Drawing Standard

Drawing sheet

Scale

Lettering

Line types

Contents

Definition and Necessity Drawing standards are set of rules that govern how technical drawings are represented. Drawing standards are used so that drawings convey the same meaning to everyone who reads them.

Drafting Equipment To prepare engineering drawing, special drawing instruments are required. • Drawing Paper (A3) • Set of Pencils (HB, 2H, 3H) • Eraser • Adhesive Tape • Tee-Square • Scale / Ruler • Compass • Set-Square 45° • Set-Square 30 °-60 ° • Protractor- 180 ° or 360 ° • French curves • Circle master • Drawing Board

Type Of Lines & Pencils Pencils • 2 types of pencils are used: Mechanical & Drawing • Advantages of Mechanical Pencils; – – – –

Could maintain the constant length and thickness of the lines Easy refill Permits the lead to be used till the end Less expensive on the long run

• Drawing Pencils are made of graphite and polymer binder or clay at different concentration. • Drawing Pencils are graded based on the different composition. 16

Type Of Lines & Pencils cont… • Drawing Pencil Grades; – 9H, 8H, 7H, 6H, 5H, 4H – Hard; only used for high accuracy like graphical computations, charts & diagrams. Used to draw lines in Engineering Drawing, however limited. – 3H, 2H, H, F, HB, B – Medium; Used for general purpose works in technical drawings such as sketching, arrowheads, & letterings. – 2B, 3B, 4B, 5B, 6B, 7B – Soft; these are too soft to be used in drawings as they easily smudged and difficult to erase the traces.

17

Drawing Standards • Drawing standards differs depending region. • Different standards are different drawing rules. • When a designer works with an engineering drawing they must be familiar with the precise meaning of; – Various line styles – Abbreviations – Drawing simplifications

• Standards are developed both privately by companies and by internationally recognized institutions. • 2 common standards used in Engineering Drawings are – British Standard Institution: BS 8888 (Superseded BS 308) – American National Standards Institute: Y14 series 18

Drawing Standards Cont… •

Exp. Of Sub-Standards in ANSI Y.14;

– Started in 1975 in Detroit, MI, and revised every 5 years or so. • • • • • • • • • • •

ANSI Y14.1 Drawing Sheet Size and Format ANSI Y14.2 Line Conventions and Lettering ANSI Y14.3 Multi and Sectional View Drawings ANSI Y14.4 American Drafting Standards Manual ANSI Y14.5 Dimensioning and Tolerance ANSI Y14.6 Screw Thread Representation ANSI Y14.7 Gear Drawing Standard ANSI Y14.8 Castings ANSI Y14.9 Forgings ANSI Y14.1 Metal Stampings ANSI Y14.13 to Section 36 Springs, electrical, Title and Notes, … 19

Standard Code Country Thailand USA

Code

Full name

มอก./TIS สำนักงำนมำตรฐำนผลิตภัณฑ์อตุ สำหกรรม ANSI

American National Standard Institute

Japan

JIS

Japanese Industrial Standard

UK

BS

British Standard

Australia

AS

Australian Standard

Germany

DIN

Deutsches Institut für Normung

ISO

International Standards Organization

Examples of JIS Standard Contents

Code number JIS Z 8311

Sizes and Format of Drawings

JIS Z 8314

Scales

JIS Z 8312

Line Conventions

JIS Z 8313

Lettering

JIS Z 8315

Projection methods

JIS Z 8316

Presentation of Views and Sections

JIS Z 8317

Dimensioning

Drawing Standard Drawing Sheet

Drawing standard

Contents

Drawing Sheet : Standard size Trimmed paper of

a size A0 ~ A4. Standard sheet size (JIS) A4 A3 A2 A1 A0

210 x 297 297 x 420 420 x 594 594 x 841 841 x 1189

A4 A3 A2

A1

A0 (Dimensions in millimeters)

Drawing Sheet : Orientation & Margin c

1. Type X (A0~A4)

Border d lines

c

c

Drawing space

Sheet size

Title block 2. Type Y (A4 only) d Drawing space

Title block

A4 A3 A2 A1 A0

c (min) d (min) 10 10 10 20 20

25 25 25 25 25

Layout of Drawing • The preferred size of drawing sheets are given in table below. 10mm 120 mm

75 mm

7mm

NAME:

15 mm

CLASS: TITLE: SCALE: DATE:

Drawing Standard Drawing Scale

Drawing standard

Contents

Drawing Scales : Definition Length, size

Scale is a ratio between the linear dimension of a drawn representation of an object and the actual object.

1

Drawing

:

2

Actual

Drawing Scales : Designation Designation of a scale consists of the word “SCALE” followed by the indication of its ratio, as follows SCALE 1:1 for full size SCALE X:1 (X > 1) for an enlargement scales SCALE 1:X (X > 1) for a reduction scales

Drawing scale is commonly found in a title block.

Drawing Scales : Notes Dimension numbers shown in the drawing represent the “true size” of an object and they are independent of

the drawing scale used.

Drawing Scales : Standard scale Standard reducing scales are 1:2, 1:5, 1:10, 1:20, 1:50, 1:100 Standard enlarging scales are 2:1, 5:1, 10:1, 20:1, 50:1, 100:1

Drawing Standard Lettering

Drawing standard

Contents

Recommendation Text’s style on the drawing

must have the following

Examples GOOD

2 properties Not uniform in style.

Legibility - Shape

Not uniform in height.

- Space between letters - Space between words

Uniformity - Size (or text height) - line thickness

Not uniformly vertical.

Not uniform in thickness of stroke.

Inappropriate space between letters

Style (this course) Gothic vertical style.

Begin the sentence, phrase or word with a capital letter. Text height 2~3 mm.

Space between lines of text is about of text height. Height of the lower-case letter is about 2/3 of that of a

capital letter.

Basic Strokes Straight

Slanted

Horizontal

Curved

Examples “I” letter 1

“A” letter 2

1

“B” letter 1

4

3 3 2

5

6

Upper-caseStrokes Letters &Sequence Numerals Suggested Straight line letters

Curved line letters & Numerals

Lower-case Letters

Stroke Sequence : Upper-case I

L

E

H

T

F

Skip section

Stroke Sequence : Upper-case V

X

W

Skip section

Stroke Sequence : Upper-case N

M

K

Y

A

4

Z

Skip section

Stroke Sequence : Upper-case O

Q

C

G

Skip section

Stroke Sequence : Upper-case D

U

R

J

P

B

Skip section

Stroke Sequence : Upper-case 1

2

5

7

Skip section

Stroke Sequence : Upper-case S

0

8

9

3

6

Skip section

Stroke Sequence : Lower-case l

i

Skip section

Stroke Sequence : Lower-case v

w

x

k

z

Skip section

Stroke Sequence : Lower-case j

y

f

t

r

Skip section

Stroke Sequence : Lower-case c

o

a

b

d

p

q

e

Skip section

Stroke Sequence : Lower-case g

u

n

m

h

s

Skip section

Word Composition Space between the letters depends on the adjacent

contour of the letters. Non-uniform spacing

DRAWING

Uniform spacing

D R A W IN G

Word having non-uniform spacing is more readable.

Word Composition

DRAWING Contour

Contour can be denoted as “straight”, “slant” and “curve”. Adjacent contour can be : II, IN, IM, IP etc.

2. straight-curve (or curve-straight) : IO, QR etc.

3. straight-slant (or slant-straight)

: IV, IW etc.

4. curve-curve

: OO, OG etc.

5. slant-curve (or curve-slant)

: VO, WG, VC etc.

6. slant-slant

: VW, VX etc.

Spacing

1. straight-straight

Sentence Composition Leave the space between words equal to the space requires for writing a letter “O”.

Example

ALL ODIMENSIONS OARE OIN MILLIMETERS OUNLESS OTHERWISE O SPECIFIED.

Drawing Standard Line Types

Drawing standard

Contents

Basic Line Types & Name according to application Thickness

Thick

Thin Visible line

Style

Continuous Dash Chain 1. Visible line

1. Dimension line 2. Extension line 3. Leader line Hidden line Center line

represent features that can be seen in the current view.

2. Dimension line Extension line indicate the sizes and location of features. Leader line 3. Hidden line

represent features that can not be seen in the current view.

4. Center line

represents symmetry, path of motion, centers of circles,

axis of axisymmetrical parts

Example

Contents

Example Of Eng. Drawing