Lecture 01 (Introduction).pdf

8/11/2019 Lecture 01 (Introduction).pdf

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Graphical means of expression oftechnical details without the

ENGINEERING DRAWING

7

arr er o a anguage.

Universal language for Engineers



Sl. No. Item Quantity1 Mini-drafter (or T-Square) 1

2 Engineering Drawing Box 1

3 French curves 1 set

4 Set-square 1 set

5 Protractor 1

6 Drawing Clip 1 set

List of tools required for the drawing practice session

10

-

8 Lead (HB, H & 2H) 1 each set

9 Eraser 1

10 Sand paper/cello tape 1

11 Blade / pencil sharpener 112 Drawing Sheet 1 per session

Students without Engineering Drawing Box will not be allowed toattend the practical session.

School Instrument box is not allowed.



Mini-drafter

11



Set-square

13

French Curves

Drawing Clips



14

Scale set



15

Engineering Drawing Box



16



Pencils

17



Designation Length x Width

(mm)

Recommended foruse with sheet

sizes

D0 1500 x 1000 A0

Dimensions of Engineer’s Drawing Boards

18

xD2 700 x 500 A2

D3 500 x 500 A3D0 and D1 for drawing offices, for students use – D2



Standard sizes of drawing sheets as per BIS

Designation Size

(mm)A0 841 x 1189

19

A2 420 x 594

A3 297 x 420

A4 210 x 297



DrawingSheet

Sizes

20



Drawing sheet Layout

21



Title Block

22



LINES AND LETTERING*

LINES

Lines are the basic feature of a drawing. A line maybe straight, curved, continuous, segmented, thin,

thick, etc., each having its own specific sense.

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Line strokes refer to the directions of drawing

straight and curved lines

*standard given in BIS : SP-46, 2003

Available in //intranet.iitg.ernet.in/bis_asp/start.shtml



Line Strokes

Vertical and inclined lines are drawn from top to bottom,

horizontal lines are drawn from left to right. Curved lines

are drawn from left to right or top to bottom.

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Line types

Illustration Application

Thick Outlines, visible edges, surfaceboundaries of objects, margin lines

Continuous thinDimension lines, extension lines,section lines leader or pointer lines,construction lines, boarder lines

Continuous thin wavy Short break lines or irregular

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oun ary nes – rawn ree an

Continuous thin with zig-zagLong break lines

Short dashes, gap 1, length 3 mm Invisible or interior surfaces



Line types

Illustration Application

Short dashes Center lines, locus lines

Alternate long and shortdashes in a proportion of 6:1,

Long chain thick at end and

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Cutting plane lines

Continuous thick border lineBorder



Uses of different types of lines in a given drawing

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Units of Measurement

International systems of units (SI) – which is based

on the meter.

Millimeter (mm) - The common SI unit of measure onen ineerin drawin .

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Individual identification of linear units is notrequired if all dimensions on a drawing are in thesame unit (mm).

The drawing shall however contain a note: ALLDIMENSIONS ARE IN MM. (Bottom left corneroutside the title box)



Dimensioning

Indicating on a drawing, the size of the object and

other details essential for its construction andfunction, using lines, numerals, symbols, notes, etc.

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Dimensions indicated on a drawing should be thosethat are essential for the production, inspection andfunctioning of the object.

Dimensions indicated should not be mistaken asthose that are required to make the drawing of anobject.



An example

30



Extension line – a thin, solid line

perpendicular to a dimension line,

indicating which feature is associated with

the dimension.

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Visible gap – there should be a visible

gap of 1.5 mm between the feature’s

corners and the end of the extension line.



Leader line

A thin, solid line used to indicate the feature withwhich a dimension, note, or symbol isassociated.

Generally a straight line drawn at an angle that isneither horizontal nor vertical.

Terminated with an arrow touching the part or

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detail.

On the end opposite the arrow, the leader line willhave a short, horizontal shoulder. Text isextended from this shoulder such that the text

height is centered with the shoulder line.



Arrows

3 mm wide and should be 1/3rd as wide as they arelong - symbols placed at the end of dimension lines toshow the limits of the dimension. Arrows are uniformin size and style, regardless of the size of the drawing.

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Spacing of Dimensions

34



Placing of Dimensions

Orientation of Dimensioning Text

35



Dimensioning of angles

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Dimensioning of Circular Features

A circle should be dimensioned by giving its diameterinstead of radius. The dimension indicating a

diameter should always be preceded by the symbol ø,

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Dimensioning a Length

Depends on Available Space

38



Dimensioning Radii

Arcs of Circle Precede with ‘R’ to distinguish from length

39



RULES OF DIMENSIONING

1. Between any two extension lines, there must be one and only onedimension line bearing one dimension.

2. As far as possible, all the dimensions should be placed outside theviews. Inside dimensions are preferred only if they are clearer andmore easily readable.

3. All the dimensions on a drawing must be shown using either AlignedSystem or Unidirectional System. In no case should, the two systems

be mixed on the same drawing.

4. The same unit of length should be used for all the dimensions on a

drawing. The unit should not be written after each dimension, but anote mentioning the unit should be placed below the drawing.

5. Dimension lines should not cross each other. Dimension lines should

also not cross any other lines of the object.

6. All dimensions must be given.

7. Each dimension should be given only once. No dimension should beredundant.

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8. Do not use an outline or a centre line as a dimension line. A centre line

may be extended to serve as an extension line.

9. Avoid dimensioning hidden lines.

10. For dimensions in series, adopt any one of the following ways.

i. Chain dimensioning (Continuous dimensioning) All thedimensions are aligned in such a way that an arrowhead of onedimension touches tip-to-tip the arrowhead of the adjacentdimension. The overall dimension is placed outside the other

.

ii. Parallel dimensioning (Progressive dimensioning) All thedimensions are shown from a common reference line. Obviously,

all these dimensions share a common extension line. This methodis adopted when dimensions have to be established from aparticular datum surface

iii. Combined dimensioning When both the methods, i.e., chaindimensioning and parallel dimensioning are used on the samedrawing, the method of dimensioning is called combineddimensioning.

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•Single stroke refers to the thickness obtained in one stroke of a pencilor ink pen .

•It does not mean that the pencil or pen should not be lifted whilecompleting a particular letter.

Lettering types

• Lettering A – Height of the capital letter is divided into 14 equal parts

• Lettering B – Height of the capital letter is divided into 10 equal parts

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Specifications Value Size (mm)

Capital letter height h 2.5 3.5 5 7 10 14 20

Lowercase letter height a = (5/7)h - 2.5 3.5 5 7 10 14

Thickness of lines b = (1/14)h 0.18 0.25 0.35 0.5 0.7 1 1.4

Specifications of A -Type Lettering

characters

c = (1/7)h 0.35 0.5 0.7 1 1.4 2 2.8

Min. spacing b/n words d = (3/7)h 1.05 1.5 2.1 3 4.2 6 8.4

Min. spacing b/n baselines e = (10/7)h 3.5 5 7 10 14 20 28

Ratio of height to width varies, but in most cases is 6:5Ratio of height to width varies, but in most cases is 6:5

Geometric Construction



Geometric Construction

• Construction of primitive geometricforms (points, lines and planes etc.)that serve as the building blocks for

.

• Defining the position of the object in

space

Some

Primitive geometric forms Primitive Geometric Forms

Some

Lines and Planes



Lines and Planes



Curved surfaces



Definition

A scale is defined as the ratio of the lineardimensions of the object as represented in a

drawing to the actual dimensions of the

same.

Scale

N it



Necessity

• Drawings drawn with the same size as the objects arecalled full sized drawing.

• It is not convenient, always, to draw drawings of theobject to its actual size. e.g. Buildings, Heavy

, , , .

• Hence scales are used to prepare drawing at

•

Full size• Reduced size

• Enlarged size



Types of Scale• Engineers Scale :

The relation between the dimension on the drawingand the actual dimension of the object is mentioned

numerically (like 10 mm = 15 m).

• Graphical Scale:

Scale is drawn on the drawing itself. This takes care

of the shrinkage of the engineer’s scale when thedrawing becomes old.

T f G hi l S l



Types of Graphical Scale

• Plain Scale

• Diagonal Scale

• Vernier Scale

• Comparative scale



Representative fraction (R.F.)

en a cm ong ne n a raw ng represen s

meter length of the object,

100

1

1001

1

1

1. ===

cm x

cm

m

cmF R

Pl i l



Plain scale

• A plain scale consists of a line divided into suitable

number of equal units. The first unit is subdivided

into smaller parts.

• The zero should be placed at the end of the 1st main.

• From the zero mark, the units should be numbered

to the right and the sub-divisions to the left.

•

The units and the subdivisions should be labeledclearly.

• The R.F. should be mentioned below the scale.



Di l S l



Diagonal Scale

• Through Diagonal scale, measurements can be up

to second decimal (e.g. 4.35).

• Diagonal scales are used to measure distances in a

un an s mme a e wo su v s ons; e.g. m,

cm & mm, or yard, foot & inch.

• Diagonal scale can measure more accurately than

the plain scale.

Diagonal scale Concept



Diagonal scale…..Concept

• At end B of line AB, draw a perpendicular.

• Step-off ten equal divisions of any length alongthe perpendicular starting from B and ending

at C.

• Number the division points 9,8,7,…..1.

.

• Through the points 1, 2, 3, etc., draw linesparallel to AB and cutting AC at 1, 2, 3, etc.

• Since the triangles are similar; 11 = 0.1 AB,

22 = 0.2AB, …. 9

9 = 0.9AB.

• Gives divisions of a given short line AB inmultiples of 1/10 its length, e.g. 0.1AB, 0.2AB,0.3AB, etc.

Construct a Diagonal scale of RF = 3:200 (i.e. 1:66 2/3) showing



g ( ) g

meters, decimeters and centimeters. The scale should measure up

to 6 meters. Show a distance of 4.56 meters

• Length of the scale = (3/200) x 6 m = 9 cm

• Draw a line AB = 9 cm . Divide it in to 6 equal parts.

• Divide the first part A0 into 10 equal divisions.

• At A draw a perpendicular and step-off along it 10 equal

divisions, ending at D.



Vernier scale Concept



Vernier scale…. Concept• Length A0 represents 10 cm and is divided in to 10 equal parts

each representing 1 cm.

• B0 = 11 (i.e. 10+1) such equal parts = 11 cm.

• Divide B0 into 10 equal divisions. Each division of B0 will beequal to 11/10 = 1.1 cm or 11 mm.

• Difference between 1 art of A0 and one art of B0 = 1.1 cm -1.0cm = 0.1cm or 1 mm.

Question: Draw a Vernier scale of R.F. = 1/25 to read up

t 4 t O it h l th 2 39 d 0 91



to 4 meters. On it show lengths 2.39 m and 0.91 m

•

• Draw a 16 cm long line and divide it into 4 equal parts. Each part is1 meter. Divide each of these parts in to 10 equal parts to showdecimeter (10 cm).

• Take 11 parts of dm length and divide it in to 10 equal parts. Each of

these parts will show a length of 1.1 dm or 11 cm.

• To measure 2.39 m, place one leg of the divider at A on 99 cm mark

and other leg at B on 1.4 mark. (0.99 + 1.4 = 2.39).

• To measure 0.91 m, place the divider at C and D (0.8 +0.11 = 0.91).

Question: Draw a Vernier scale of R.F. = 1/25 to read up

to 4 meters On it sho lengths 2 39 m and 0 91 m



to 4 meters. On it show lengths 2.39 m and 0.91 m

•

• Draw a 16 cm long line and divide it into 4 equal parts. Each part is1 meter. Divide each of these parts in to 10 equal parts to showdecimeter (10 cm).

• Take 11 parts of dm length and divide it in to 10 equal parts. Each of

these parts will show a length of 1.1 dm or 11 cm.

• To measure 2.39 m, place one leg of the divider at A on 99 cm mark

and other leg at B on 1.4 mark. (0.99 + 1.4 = 2.39).

• To measure 0.91 m, place the divider at C and D (0.8 +0.11 = 0.91).

Lecture 01 (Introduction).pdf

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