Subject:

Engineering Graphics

Branch: MechanicalClass: B2Semester: 2nd

Year: 2014Topic: Introduction

Group members Enrollment no

Prajapati Ashvinkumar 130980119079

Prajapati Hardik 130980119080

Prajapati Jay 130980119081

Prajapati Kaushik 130980119082

Introduction

Engineering means “Applied science” Graphics means “drawings” “Language of Engineers” It is a way for communicating Engineer’s ideas, designs and

thoughts to others. The communication of ideas through the graphical language. It’s helps to reduce the time, increase the accuracy of the

object to be manufacture.

Freehand drawing

The lines are sketched without using instruments other

than pencils and erasers.

Example

Instrument drawing

Instruments are used to draw straight lines, circles, and

curves concisely and accurately. Thus, the drawings are usually

made to scale.

Example

ISO International Standards Organization

Standard Code

ANSI American National Standard InstituteUSA

JIS Japanese Industrial StandardJapan

BS British StandardUK

AS Australian StandardAustralia

Deutsches Institut für NormungDINGermany

Country Code Full name

India BIS Bureau of Indian Standards

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)

Drawing Scales

Scale is the ratio of the linear dimension of an element of 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

:

Drawing Scales

Designation 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 reduction 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.

Visible lines represent features that can be seen in the

current view

Meaning of Lines

Hidden lines represent features that can not be seen in

the current view

Center line represents symmetry, path of motion, centers

of circles, axis of axisymmetrical parts

Dimension and Extension lines indicate the sizes and

location of features on a drawing

Example : Line conventions in engineering drawing

Text on Drawings

Text on engineering drawing is used :

To communicate nongraphic information.

As a substitute for graphic information, in those instance where text can communicate the needed information more clearly and quickly.

Uniformity - size- line thickness

Legibility - shape- space between letters and words

Thus, it must be written with

DIMENSIONING METHOD

Aligned Dimensioning Unidirectional Dimensioning

Objectives in Drawing

Typical Drawing Equipment

Objectives in Drawing

1. Accuracy

2. Speed

3. Legibility

4. Neatness

Drawing board

It’s a rectangular wooden board 22 mm of thick and size is 650*470 mm

Drawing board must be placed on the table with working edge always to be at the left side.

Working edge

Mini drafter

It’s a combined form of T-square ,Set square Protractors and scale. One end of the drafter is Clamped at the left top end.

Drawing Pencils

High-quality drawing pencils should be used in technical drawing, never ordinary writing pencils.

HB(soft grade) – used for lettering, freehand sketching

H ( medium grade ) - used for visible outlines, edges

2H(hard grade) - used for dimension line, hidden line

Drawing sheets

The basic principle involved in arriving at the sheet size is x1:x2 = 1:√2

X1,X2 are sides of the sheet

The surface area of A0 size sheet is one square meter.

T-square

Some drawing instruments

Layout of drawing sheets

Standard form of arrangement

Important particulars are included

Facilitate quick reading of important particulars – quick references are located easily – drawings are prepared at various locations and shared

Borders

space left all around in between the trimmed edges of the sheet a minimum of 10 mm

Line types

Engineering scales

Dimensions of large objects must be reduced to accommodate

on standard size drawing sheet.

This reduction creates a scale of that reduction ratio.

This ratio is called reducing scale

Full scale 1:1

Reducing scale 1:2,1:5,1:10

Enlarging scale 2:1,5:1,10:1

Geometric construction

Point : A point is not a thing, but a place. We indicate the

position.

Line joining of two point but no breath and think

Polygon :it’s a plane figure more than 4 straight lines

Depending on the number of sides the regular polygon are

classified as

1) Rectangle, 2) Pentagon, 3) Hexagon, 4) Heptagon,

5) Octagon, 6) Nonagon.

3-1024 sides is name as polygon.

Vertical plane –when the observer is viewing it from the

front.

It shows only two dimension length and height.

Horizontal plane – when the observer is viewing it from top.

It shows only breath.

Vertical & horizontal plane

Orthographic projection

Four quadrant

First angle projection

It’s in first quadrant. Top view comes below to the front view

Third angle projection

It’s in third quadrant Top view comes above the front view

ENGINEERING CURVES