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Bridge Course

Introduction TO ENGINEERING( MECHANICAL ENGINEERING )

Lecture No . 1 , 2 and 3

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Introduction

Engineering Graphics is a language ofcommunication between engineers oninternational basis.

The beauty of this tool of communicationis that it transfers 100% informationbetween technical peoples.

Graphical presentation is more than anessay for describing the same thing.

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Lecture -4Drawing Instruments

and simple geometry

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Instruments for DrawingFollowing drawing instruments are required

for preparing a neat and correct drawing.

Basic Instruments.(i) Drawing board (ii) Drawing sheet

(iii) Drawing pencil (iv) Drawing clips

(v) Eraser (vi) Eraser shield

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Instruments for Drawing Straight Lines.(i) T- square. (ii) Set- squares

Instruments for Drawing Curved Lines.(i) Large size compass (ii) Small bow

(iii) French curve

Instruments for Measuring Distance.

(i) Large size divider (ii) Small bow divider

(iii) Scales

Instruments for Measuring Angles.

(i) Protractors (ii) Set-squaresSpecial Tool. Mini drafter

http://2.bp.blogspot.com/-h_OHPnRSzZM/T_hkf76R0LI/AAAAAAAAGYU/xRYnis2-Ij4/s1600/drawing+board.png

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Fig. 1 The top surface of the board is perfectly smooth and level. Fig. 2

Bottom of the drawing board. A drawing board is rectangular in shape

and is made of well seasoned soft wood such as oak or pine. Astraight ebony edge is fitted on the left side on the board against which

the head of the T- square moves

Fig. 1 Drawing Board (Top) Fig. 2 Drawing Board (Bottom)

Drawing Board

http://2.bp.blogspot.com/-h_OHPnRSzZM/T_hkf76R0LI/AAAAAAAAGYU/xRYnis2-Ij4/s1600/drawing+board.pnghttp://2.bp.blogspot.com/-h_OHPnRSzZM/T_hkf76R0LI/AAAAAAAAGYU/xRYnis2-Ij4/s1600/drawing+board.png

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T- Square

It is composed of a long strip called blade, which is screwedrigidly at right angle to a shorter piece called head or

stock. It is made of mahogany or pear wood, which is harder

than the board wood. The head also has an ebony edge which

slides against the working edge of the board. T- Square is

used for making horizontal, vertical, inclined or parallel lineson the drawing sheet.

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How to Clamp Paper to Drafting Board Using Clips

1. Place the paper close to the tables left edge.

2. Move the paper until its lower edge place about the top edge of T-square.

3. Align the top edge of the paper with T-square blade.

4. Attach the papers corners with tape/clips .

5. Move T-square down to smooth the paper.6. Attach the remaining papers corners with tape/clips.

Clips

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Neatness, quality and accuracy of the drawing greatly depends upon the type

and conditions of the pencil used for drawing.

(a) Hard : 9H to 4H

(b) Medium : 3H to B (3H, 2H, H, F, HB and B)

(c) Soft : 2B to 7B

Following pencils should be used for drawing work in class:

2H Pencil - For drawing outlines, Centre lines, Break lines, etc.

H Pencil - For dimensioning, arrowheads, hatching lines, lettering,

sketching, circles, arcs, etc.

Micro tip pencil - 0.5mm for drawing outlines and 0.8mm for shading and

sketching

Drawing Pencil.

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ISO A Drawing Sizes mm)A4 210 X 297A3 297 X 420A2 420 X 594A1 594 X 841A0 841 X 1189

Sizes of drawing sheet typically comply with either of two

different standards, ISO (World Standard) or ANSI/ASME

Y14(American), according to the following tables:

ISO paper sizes

http://en.wikipedia.org/wiki/ISO_standardhttp://en.wikipedia.org/wiki/ANSI/ASME_Y14.1http://en.wikipedia.org/wiki/ANSI/ASME_Y14.1http://en.wikipedia.org/wiki/File:A_size_illustration.svghttp://en.wikipedia.org/wiki/File:A_size_illustration.svghttp://en.wikipedia.org/wiki/ANSI/ASME_Y14.1http://en.wikipedia.org/wiki/ANSI/ASME_Y14.1http://en.wikipedia.org/wiki/ANSI/ASME_Y14.1http://en.wikipedia.org/wiki/ANSI/ASME_Y14.1http://en.wikipedia.org/wiki/ISO_standard

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1.Start circle.Apply enough pressure to the needle,

holding compass handle between thumb and index

fingers.

2. Complete circle.Revolve handle clockwise.

Using the Compass

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Using a Circle Template1. Draw two perpendicular lines that pass through center

of a circle to be drawn.

2. Place the template till all marking coincide with center

lines.

3. Tracing the circle. (Hold the pencil normal to the paper.)

Center of a circle to be drawn

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Draw a Horizontal Line

1. Press the T-square head against the left edge of the table.

2. Smooth the blade to the right.

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Draw a Horizontal Line3. Lean the pencil at an angle about 60owith the paper in the

direction of the line and slightly toed in.

4. Draw the line from left to right while rotating the pencil

slowly.

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Draw a line at 45owith horizontal

2. Draw the line in the direction as shown below.

1. Place 45otriangle on the T-square edge and press them

firmly against the paper.

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A

B

Draw the line passing through

two given points

1. Place the pencil tip at one of the points.

2. Place the triangle against the pencil tip.

A

B

Given

3. Swing the triangle around the pencil tip

until its edge align with the second point.

4. Draw a line.

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To Bisect a Line

1. Swing two arcs of any radius greater than half-length of

the line with the centers at the ends of the line.

2. Join the intersection points of the arcs with a line.

(not to scale)

A

B

r1

Given

A

B

r1

3. Locate the midpoint.

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To Bisect an Angle

2. Swing the arcs of any radius from the intersection

points between the previous arc and the lines.

3. Draw the line.

1. Swing an arc of any radius whose centers at the vertex.

(not to scale)

r1

Given

A

B

C

A

B

C

r2

r2

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PROBLEM :To make 12 equal parts of circle.

2

3

5

4

6

7

8

9

10

11

12

1

PROBLEM :To make 08 equal parts of circle.

3

2

8

7

4

5

6

1

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How to Keep Your Drawing CleanDo Dont

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Lecture - 5Dimensioning and

geometrical construction

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Dimensioning componentsExtension linesDimension lines

(with arrowheads)

Leader lines

Dimension figures

Notes :- local note

- general note

Drawn with

4Hpencil

Lettered with

2Hpencil.

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indicate the location on the objects features that are dimensioned.

Extension lines

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Dimension linesindicate the direction and extent of a dimension, and inscribe dimension f igures.

10 27

43

13

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indicate details of the feature with a local note.

Leader lines

10 27

43

13

10 Drill, 2 HolesR16

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30

30

30

30

EXAMPLE : Dimension of lengthusing al ignedmethod.

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30

30

30

30

3030

30

30

EXAMPLE : Dimension of lengthusing unidi rect ionalmethod.

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To draw a regularhexagon given thedistance acrosscorners, draw a circlehaving a diameterequal to the distanceacross corners

Step off the radiusround it to give six

equally spaced points. Join these points to

form the hexagon.

DRAWING LINES

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Lecture - 6

Introduction toOrthographic Projection

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ORTHOGRAPHIC

PROJECTIONS

CONCEPT OF 1STAND 3RDANGLE

PROJECTION METHODS

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Projection systems

1. Firstangle system

2. Thirdangle system

First Quadrant

Third

Quadrant

- European country

- ISO standard India

- Canada, USA,

Japan, Thailand

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Orthographic views

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Orthographic views1stangle system 3rdangle system

Foldingline

Foldingline

Foldingline

Foldingline

Orthographic views

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Orthographic views

1stangle system 3rdangle system

Front View

Front View

Right Side View

Right Side View

Top View

Top View

Projection symbols

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First angle

system

Third angle

system

Projection symbols

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prepare Orthographic views (First angle method)

for the parallel key from the isometric drawing as

below

Given Iso.view

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prepare Orthographic views (First angle method)

from the isometric drawing as below

Given Iso.view

Orthographicviews

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Given Iso.view

prepare Orthographic views (First angle method)

from the isometric drawing as below