mec 111 technical drawing

8/13/2019 Mec 111 Technical Drawing

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UNESCO-NIGERIA TECHNICAL &

VOCATIONAL EDUCATION REVITALISATION

PROJECT-PHASE II

YEAR I- SEMESTER I

THEORY/PRACTICAL

Version 1: December 2008

NATIONAL DIPLOMA IN

MECHANICAL ENGINEERING TECHNOLOGY

TECHNICAL DRAWING

COURSE CODE: MEC112


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MECHANICAL ENGINEERING TECHNOLOGYTECHNICAL DRAWING MEC 112)

TABLE OF CONTENTSWEEK 1

1.0 : INTRODUCTION

1.1: INTRODUCTION TO DRAWING EQUIPMENTS

1.1.1: T-SQUARE

1.1.2: SET SQUARE

1.1.3: COMPASS

1.1.4: DRAWING TABLE

1.1.5: IRREGULAR CURVES (FRENCH CURVES)

1.1.6: PROTRACTOR

1.1.7: DRAWING PENCIL:

1.1.8: ERASER:

1.2: LINES

1.2.1: LINES AND LINE STYLES

1.2.2: LINE THICKNESS

1.2.3: LINE STYLES

1.2.4: BREAK LINES

1.2.5: LEADERS

1.2.6: DATUM LINES

1.2.7: PHANTOM LINES

1.2.8: STITCH LINES

1.2.9: CENTER LINES

1.2.10: EXTENSION LINES

1.2.11: OUTLINES OR VISIBLE LINES

1.2.12: CUTTING-PLANE/VIEWING-PLANE LINES

1.2.13: HIDDEN LINES

1.2.14: SECTIONING LINES

1.2.15: DIMENSION LINES

1.3: DIMENSIONING - AN OVERVIEW


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1.3.1: PARALLEL DIMENSIONING

1.3.2: SUPERIMPOSED RUNNING DIMENSIONS

1.3.3: CHAIN DIMENSIONING

1.3.4: COMBINED DIMENSIONS

1.3.5: DIMENSIONING BY CO-ORDINATES

1.3.6: SIMPLIFIED DIMENSIONING BY CO-ORDINATES

1.3.7: DIMENSIONING SMALL FEATURES

1.3.8: DIMENSIONING CIRCLES

1.3.9: DIMENSIONING HOLES

1.3.10: DIMENSIONING RADII

1.3.11: SPHERICAL DIMENSIONS

1.3.12: TOLERANCE

1.4 : LINE STYLES

1.5 : TASK SHEET 1

WEEK 2

2.1: PLANNING YOUR ENGINEERING DRAWING

2.2: LAYOUT OF DRAWING PAPER

2.3: COMMON INFORMATION RECORDED ON THE TITLE BLOCK

2.4. TITLE BLOCK SAMPLE

2.5: DRAWING SHEETS/PAPERS

2.6 : DRAWING SCALES

2.7: LETTERING METHOD

2.8: TASK SHEET 2

WEEK 3

3.1: GEOMETRICAL DRAWINGS

3.2: STRAIGHT LINES AND ANGLES

3.3: TRIANGLE

3.4: TASK SHEET 3


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WEEK 4

3.5: QUADRILATERALS

3.5.1. SQUARE

3.5.2. RECTANGLE

3.5.3. PARALLELOGRAM

3.5.4. RHOMBUS

3.5.5 TRAPEZIUM

3.5.6. TRAPEZOID

3.6: CONSTRUCTION OF QUADRILATERALS

3.7: CIRCLES

3.7.1: TYPES OF CIRCLES

3.7.2: PROPERTIES OF A CIRCLE

3.7.3: CONSTRUCTION INVOLVING CIRCLES

3.8: TASK SHEET 4

WEEK 5

3.7.3: CONSTRUCTIONS INVOLVING CIRCLES

4.0: TANGENCY

4.1: CONSTRUCTION OF TANGENT

5.0: POLYGONS

5.1: CONSTRUCTION OF POLYGONS

5.2: TASK SHEET 5

WEEK 6

6.0 ELLIPSE:

6.1 PROPERTIES OF AN ELLIPSE


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6.2 CONSTRUCTION OF ELLIPSE USING CONCENTRIC CIRCLES

METHOD

6.3 CONSTRUCTION OF ELLIPSE USING RECTANGULAR

METHOD

6.4 CONSTRUCTION OF ELLIPSE USING TRAMMEL METHOD

6.5 CONSTRUCTION OF NORMAL AND THE TANGENT TO AN

ELLIPSE, AND TO FIND THE FOCI.

6.7 TASK SHEET 6

WEEK 7

7.0 ISOMETRIC PROJECTION:

7.1 HOW TO DRAW IN ISOMETRIC PROJECTION:

7.2 TASK SHEET 7

WEEK 8

8.0 ORTHOGRAPHIC PROJECTION

8.1 THREE VIEW OF AN OBJECT IN FIRST AND THIRD ANGLE

PROJECTIONS

8.2 THE MAIN FEATURES OF THE SIX VIEW OF AN OBJECT

8.3 ONE POINT PERSPECTIVE

8.4 TWO POINT PERSPECTIVE8.5 THREE POINT PERSPECTIVE

8.6 TASK SHEET 8.1

WEEK 9

8.7 MULTI-VIEWS DRAWING USING 1ST

& 3RD

ANGLE OF

PROJECTION

8.7.1 MULTI VIEWS PROJECTION


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8.8 THE DIFFERENCES BETWEEN 1ST

& 3RD

ANGLE OF

PROJECTION

8.8.1 FIRST-ANGLE PROJECTION

8.8.2 THIRD-ANGLE PROJECTION

8.9 TASK SHEET 8.2

WEEK 10

9.0 ABBREVIATIONS AND SYMBOLS USED ON MECHANICAL AND

ELECTRICAL DRAWINGS.

9.1 INTRODUCTION

9.2 TECHNICAL DRAWING SYMBOLS

9.3 MECHANICAL CONVENTIONS

9.4 ELECTRICAL CONVENTIONS

9.5 LINES AND BLOCK DIAGRAMS

9.5.1 BLOCK DIAGRAM METHOD

9.5.2 LINE DIAGRAM METHOD

9.6 PNEUMATIC SYSTEM

9.7 HYDRAULIC SYSTEM

9.8 PNEUMATIC SYMBOLS

9.9 TASK 10

WEEK 11

10.0 MISSING VIEW IN ORTHOGRAPHIC

10.1 FIRST ANGLE OF PROJECTION:

10.2 THIRD ANGLE OF PROJECTION

10.3 TASK SHEET 11

WEEK 12

11.0 FREE HAND SKETCH

11.1 INTRODUCTION:


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11.2 GENERAL NOTES BEFORE SKETCHING:

11.3 TASK SHEET 12

WEEK 13

12.0 SKETCHING THE VIEWS FROM AN ACTUAL OBJECT

12.1 OBLIQUE SKETCHING

12.2 TASK SHEET 13

WEEK 14

13.0 INTERSECTION AND DEVELOPMENT

13.1 CONSTRUCTION OF SOLID WITH INTERPENETRATION

13.2 TWO DISSIMILAR SQUARE PRISMS MEETING AT RIGHT

ANGLES.

13.3 TWO DISSIMILAR SQUARE PRISMS MEETING AT AN ANGLE.

13.4 TWO DISSIMILAR HEXAGONAL PRISMS MEETING AT AN

ANGLE.

13.5 TWO DISSIMILAR CYLINDERS MEETING AT RIGHT ANGLES.

13.6 TWO DISSIMILAR CYLINDERS MEETING AT AN ANGLE.

13.7 TASK SHEET 14

WEEK 15

14.0 DEVELOPMENT

14.1 TASK SHEET 15


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(Fig.1.1)

WEEK1:

1.0 INTRODUCTIONTechnical drawing is concerned mainly with using lines, circles, arcs etc., to illustrategeneral configuration of an object, however, it is very important that the drawing

produced to be accurate and clear.

The ability to read and understand drawings is a skill that is very crucial for technical

education students; this text aims at helping students to gain this skill in a simple and

realistic way, and gradually progressed through drawing and interpreting different

level of engineering drawings.

Some basic equipments are necessary in order to learn drawing, here are the main

ones.

1.1 INTRODUCTION TO DRAWING EQUIPMENTS

1.1.1:T-SQUARE

A T-square is a technical drawing instrument

primarily guides for drawing horizontal lines on

adrafting table,it also used to guide the triangle

that is used to draw vertical lines. The name T-

square comes from the general shape of the

instrument where the horizontal member of the

T slides on the side of the drafting table.(Fig.1.1)

1.1.2: SET SQUARE

A set square or triangle is a tool used to draw

straight vertical lines at a particular planar angle to

abaseline.The most common form of Set Square isa triangular piece of transparent plastic with the

centre removed. The outer edges are typically

beveled.These set squares come in two forms, both

right triangles: one with 90-45-45 degree angles,

and the other with 90-60-30 degree angles. (Fig.1.2)

(Fig.1.2)
http://en.wikipedia.org/wiki/Drafting_tablehttp://en.wikipedia.org/wiki/Baselinehttp://en.wikipedia.org/wiki/Plastichttp://en.wikipedia.org/wiki/Bevelhttp://en.wikipedia.org/wiki/Right_trianglehttp://en.wikipedia.org/wiki/Right_trianglehttp://en.wikipedia.org/wiki/Bevelhttp://en.wikipedia.org/wiki/Plastichttp://en.wikipedia.org/wiki/Baselinehttp://en.wikipedia.org/wiki/Drafting_table


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1.1.3: COMPASS

Compasses are usually made of metal, and consist of

two parts connected by a hinge which can be adjusted.

Typically one part has a spike at its end, and the other

part a pencil.Circles can be made by pressing one legof the compasses into the paper with the spike, putting

the pencil on the paper, and moving the pencil around

while keeping the hinge on the same angle.Theradius

of the circle can be adjusted by changing the angle of

the hinge. (Fig.1.3)

(Fig.1.3)

1.1.4: DRAWING TABLE

It is a multi-angle desk which can be used in different

angle according to the user requisite. The size suites

most paper sizes, and are used for making and

modifying drawings on paper with ink or pencil.

Different drawing instruments such as set of squares,

protractor, etc. are used on it to draw parallel,

perpendicular or oblique lines. (Fig.1.4)

(Fig.1.4)

1.1.5: IRREGULAR CURVES (FRENCH

CURVES)

French curves are used to draw oblique curves other

than circles or circular arc; they are irregular set of

templates. Many different forms and sizes of curve are

available. (Fig.1.5)

(Fig.1.5)
http://en.wikipedia.org/wiki/Metalhttp://en.wikipedia.org/wiki/Hingehttp://en.wikipedia.org/wiki/Pencilhttp://en.wikipedia.org/wiki/Paperhttp://en.wikipedia.org/wiki/Anglehttp://en.wikipedia.org/wiki/Radiushttp://en.wikipedia.org/wiki/Set_squarehttp://en.wikipedia.org/wiki/Protractorhttp://en.wikipedia.org/wiki/Protractorhttp://en.wikipedia.org/wiki/Set_squarehttp://en.wikipedia.org/wiki/Radiushttp://en.wikipedia.org/wiki/Anglehttp://en.wikipedia.org/wiki/Paperhttp://en.wikipedia.org/wiki/Pencilhttp://en.wikipedia.org/wiki/Hingehttp://en.wikipedia.org/wiki/Metal


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1.1.6: PROTRACTOR

Protractor is a circular or semi-circular tool for

measuring angles. The units of measurement used aredegrees. Some protractors are simple half-discs. More

advanced protractors usually have one or two swinging

arms, which can be used to help measuring angles.

(Fig.1.6)

(Fig.1.6)

1.1.7: DRAWING PENCIL

Is a hand-heldinstrument containing an interior strip of

solid material that produces marks used to write and

draw, usually on paper. The marking material is most

commonly graphite, typically contained inside a

wooden sheath. Mechanical pencils are nowadays more

commonly used, especially 0.5mm thick (Fig.1.7a/

Fig.1.7b)

(Fig.1.7a)

Fig 7.1b
http://en.wikipedia.org/wiki/Anglehttp://en.wikipedia.org/wiki/Degree_%28angle%29http://en.wikipedia.org/wiki/Instrumenthttp://en.wikipedia.org/wiki/Writinghttp://en.wikipedia.org/wiki/Drawinghttp://en.wikipedia.org/wiki/Paperhttp://en.wikipedia.org/wiki/Graphitehttp://en.wikipedia.org/wiki/Graphitehttp://en.wikipedia.org/wiki/Paperhttp://en.wikipedia.org/wiki/Drawinghttp://en.wikipedia.org/wiki/Writinghttp://en.wikipedia.org/wiki/Instrumenthttp://en.wikipedia.org/wiki/Degree_%28angle%29http://en.wikipedia.org/wiki/Angle


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1.1.8: ERASER

Erasers are article ofstationery that is used for removingpencil

writings. Erasers have made of rubbery material, and they areoften white. Typical erasers are made of rubber, but more

expensive or specialized erasers can also containvinyl,plastic,

orgum-like materials. (Fig.1.8)

(Fig.1.8)

1.2: LINES

1.2.1: LINES AND LINE STYLES

1.2.2: LINE THICKNESSFor most engineering drawings you will require two thicknesses, a thick and

thin line. The general recommendations are that thick lines are twice as thick

as thin lines.

A thick continuous line is used for visible edges and

outlines.

A thin line is used for hatching, leader lines, short centre

lines, dimensions and projections.

1.2.3: LINE STYLESOther line styles used to clarify important features on drawings are:

1.2.4: BREAK LINES

Short breaks shall be indicated by solid freehand lines. For long breaks, full ruled

lines with freehand zigzags shall be used. Shafts, rods, tubes, etc.,

1.2.5: LEADERS

Leaders shall be used to indicate a part or portion to which a number, note, or other

reference applies and shall be an unbroken line terminating in an arrowhead, dot, or

wavy line. Arrowheads should always terminate at a line; dots should be within the

outline of an object.

1.2.6: DATUM LINES

Datum lines shall be used to indicate the position of a datum plane and shall consist of

one long dash and two short dashes, evenly spaced.
http://en.wikipedia.org/wiki/Stationeryhttp://en.wikipedia.org/wiki/Pencilhttp://en.wikipedia.org/wiki/Rubberhttp://en.wikipedia.org/wiki/Vinylhttp://en.wikipedia.org/wiki/Plastichttp://en.wikipedia.org/wiki/Gumhttp://en.wikipedia.org/wiki/Gumhttp://en.wikipedia.org/wiki/Plastichttp://en.wikipedia.org/wiki/Vinylhttp://en.wikipedia.org/wiki/Rubberhttp://en.wikipedia.org/wiki/Pencilhttp://en.wikipedia.org/wiki/Stationery


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1.2.7: PHANTOM LINES

Phantom lines shall be used to indicate the alternate position of parts of the item

delineated, repeated detail, or the relative position of an absent part and shall be

composed of alternating one long and two short dashes, evenly spaced, with a long

dash at each end.

1.2.8: STITCH LINES

Stitch lines shall be used to indicate the stitching or sewing lines on an article and

shall consist of a series of very short dashes, approximately half the length of dash or

hidden lines, evenly spaced. Long lines of stitching may be indicated by a series of

stitch lines connected by phantom lines.

1.2.9: CENTER LINESCenter lines shall be composed of long and short dashes, alternately and evenly

spaced, with a long dash at each end. Center lines shall cross without voids. See

Figure below, Very short center lines may be unbroken if there is no confusion with

other lines. Center lines shall also be used to indicate the travel of a center.

1.2.10: EXTENSION LINES

Extension lines are used to indicate the extension of a surface or to point to a location

outside the part outline. They start with a short, visible gap from the outline of the part

and are usually perpendicular to their associated dimension lines.

1.2.11: OUTLINES OR VISIBLE LINES

The outline or visible line shall be used for all lines on the drawing representing

visible lines on the object;

1.2.12:CUTTING-PLANE/VIEWING-PLANE LINES

The cutting-plane lines shall be used to indicate a plane or planes in which a section is

taken. The viewing-plane lines shall be used to indicate the plane or planes from

which a surface or surfaces are viewed. On simple views, the cutting planes shall be

indicated as shown below

1.2.13: HIDDEN LINES

Hidden lines shall consist of short dashes, evenly spaced. These lines are used to show

the hidden features of a part. They shall always begin with a dash in contact with the

line from which they begin, except when such a dash would form a continuation of afull line. Dashes shall touch at corners, and arcs shall begin with dashes on the tangent

points.


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1.2.14: SECTIONING LINES

Sectioning lines shall be used to indicate the exposed surfaces of an object in a

sectional view. They are generally thin full lines, but may vary with the kind ofmaterial shown in section.

1.2.15: DIMENSION LINES

Dimension lines shall terminate in arrowheads at each end. They shall be unbroken

except where space is required for the dimension. The proper method of showing

dimensions and tolerances is explained in Section 1.7 of ANSI Y14.5M-1982.

1.3: DIMENSIONING - AN OVERVIEW

A dimensioned drawing should provide all the information necessary for a finished

product or part to be manufactured. An example dimension is shown below.

Dimensions are always drawn using continuous thin lines. Two projection lines

indicate where the dimension starts and finishes. Projection lines do not touch the

object and are drawn perpendicular to the element you are dimensioning.

In general units can be omitted from dimensions if a statement of the units is included

on your drawing. The general convention is to dimension in mm's.

All dimensions less than 1 should have a leading zero. i.e. .35 should be written as

0.35


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1.3.1: PARALLEL DIMENSIONING

Parallel dimensioning consists of several dimensions originating from oneprojection line.

1.3.2: SUPERIMPOSED RUNNING DIMENSIONS

Superimposed running dimensioning simplifies parallel dimensions in order to

reduce the space used on a drawing. The common origin for the dimensionlines is indicated by a small circle at the intersection of the first dimension and

the projection line. In general all other dimension lines are broken. The

dimension note can appear above the dimension line or in-line with the

projection line.

1.3.3: CHAIN DIMENSIONING

Chains of dimension should only be used if the function of the object won't be

affected by the accumulation of the tolerances. (A tolerance is an indication of


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the accuracy the product has to be made to. Tolerance will be covered later in

this chapter).

1.3.4: COMBINED DIMENSIONS

A combined dimension uses both chain and parallel dimensioning.

1.3.5: DIMENSIONING BY CO-ORDINATES

Two sets of superimposed running dimensions running at right angles can be

used with any features which need their centre points defined, such as holes.


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1.3.6: SIMPLIFIED DIMENSIONING BY CO-ORDINATES

It is also possible to simplify co-ordinate dimensions by using a table to

identify features and positions.

1.3.7: DIMENSIONING SMALL FEATURES

When dimensioning small features, placing the dimension arrow between projection

lines may create a drawing which is difficult to read. In order to clarify dimensions on

small features any of the above methods can be used.

1.3.8: DIMENSIONING CIRCLES


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All dimensions of circles are proceeded by this symbol; . There are several

conventions used for dimensioning circles:

(a) Shows two common methods of dimensioning a circle. One method dimensions

the circle between two lines projected from two diametrically opposite points. The

second method dimensions the circle internally.

(b) Is used when the circle is too small for the dimension to be easily read if it was

placed inside the circle. A leader line is used to display the dimension.

(c) The final method is to dimension the circle from outside the circle using an arrow

which points directly towards the centre of the circle.

The first method using projection lines is the least used method. But the choice is up

to you as to which you use.

1.3.9: DIMENSIONING HOLES

When dimensioning holes the method of manufacture is not specified unless they

necessary for the function of the product. The word hole doesn't have to be added

unless it is considered necessary. The depth of the hole is usually indicated if it isn'tindicated on another view. The depth of the hole refers to the depth of the


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1.3.10: DIMENSIONING RADII

Cylindrical portion of the hole and not the bit of the hole caused by the tip of the drip.

All radial dimensions are

proceeded by the capital R. All

dimension arrows and lines should

be drawn perpendicular to the

radius so that the line passes

through the centre of the arc. All

dimensions should only have one

arrowhead which should point to

the line being dimensioned. There

are two methods for dimensioning

radii.

(a) Shows a radius dimensioned

with the centre of the radius

located on the drawing.

(b) Shows how to dimension radii which do not need their centres locating.

1.3.11: SPHERICAL DIMENSIONS

The radius of a spherical surface (i.e. the top of a drawing pin) when dimensioned

should have an SR before the size to indicate the type of surface.

1.3.12: TOLERANCE

It is not possible in practice to manufacture products to the exact figures displayed on

an engineering drawing. The accuracy depends largely on the manufacturing process

used and the care taken to manufacture a product. A tolerance value shows the

manufacturing department the maximum permissible variation from the dimension.

Each dimension on a drawing must include a tolerance value. This can appear either

as:

A general tolerance value applicable to several dimensions. i.e. a notespecifying that the General Tolerance +/- 0.5 mm.

or a tolerance specific to that dimensionThe method of expressing a tolerance on a dimension as recommended by the British

standards is shown below:

Note the larger size limit is placed above the lower limit.


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All tolerances should be expressed to the appropriate number to the decimal points for

the degree of accuracy intended from manufacturing, even if the value is limit is a

zero for example.

1.4: LINE STYLES

Line styles are used to clarify important features on drawings, and they are as shown

below. (Fig.1.9)

FIGURE 1.9Line styles and types

Line styles are used to graphically represent physical objects, and each has its own

meaning, these include the following:

Visible lines- are continuous lines used to draw edges directly visible froma particular angle.

Hidden lines- are short-dashed lines that may be used to represent edgesthat are not directly visible.

Centerlines- are alternately long- and short-dashed lines that may be usedto represent the axis of circular features.

Cutting plane - are thin, medium-dashed lines, or thick alternately long-and double short-dashed that may be used to define sections forsection views.

Section lines- are thin lines in a parallel pattern used to indicate surfaces insection views resulting from "cutting." Section lines are commonly referred to

as "cross-hatching."
http://en.wikipedia.org/wiki/Cross_section_%28geometry%29http://en.wikipedia.org/wiki/Cross_section_%28geometry%29


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FIGURE 1.10

Here is an example of an engineering drawing (Fig.1.10). The different line types are

colored for clarity. Black = object line and hatching. Red= hidden lines

Blue= center lines Magenta= phantom line or cutting plane

Fig.1.10Illustrating types of Lines used in an engineering Drawing.


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1.5: TASK (1)

Using the right drawing tools copy the drawings shown in Fig. 1.11 to 1.14:

Fig.1.11 Fig.1.12

Fig. 1.13 Fig. 1.14


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WEEK 2:

2.0 PLANNING YOUR ENGINEERING DRAWING

2.1: PLANNING YOUR ENGINEERING DRAWING

Before starting your engineering drawing you should plan how you are going to make

best use of the space. It is important to think about the number of views your drawing

will have and how much space you will use of the paper.

Try to make maximum use of the available space. If a view has lots of detail, try and make that view as large as possible. If

necessary, draw that view on a separate sheet.

If you intend to add dimensions to the drawing, remember to leave enoughspace around the drawing for them to be added later.

If you are working with inks on film, plan the order in which you are drawingthe lines. For example you don't want to have to place your ruler on wet ink

2.2: LAYOUT OF DRAWING PAPER

It is important that you follow some simple rules when producing an engineering

drawing which although may not be useful now, will be useful when working in

industry. All engineering drawings should feature an information box (title block).

2.3: COMMON INFORMATION RECORDED ON THE TITLE

BLOCK

2.3.1. TITLE:-The title of the drawing.

2.3.2. NAME:-The name of the person who produced the drawing. This is important for

quality control so that problems with the drawing can be traced back to their

origin.

TITLE

BOADER LINE MARGINS


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2.5: DRAWING SHEETS/PAPERS

The standard sizes of drawing papers used for normal purposes should be as follows:

Designation size in millimetersA0 841 x 1189

A1 594 x 841

A2 420 x 594

A3 297 x 420

A4 210 x 297

A5 148 x 210

A6 105 x 148

A1

A2

A3

A4

A5

A6

A6

2.6: DRAWINGS SCALES

Generally, it is easier to produce and understand a drawing if it represent the true sizeof the object drawn. This is of course not always possible due to the size of the object

to be drawn, that is why it is often necessary to draw enlargements of very small

objects and reduce the drawing of very large ones, this is called SCALE.

However, it is important when enlarging or reducing a drawing that all parts of the

object are enlarged or reduced in the same ratio, so the general configuration of the

object is saved. Thus, scales are multiplying or dividing of dimensions of the object.

The scale is the ratio between the size represented on the drawing and the true size of

the object.

A0


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Scale= Dimension to carry on the drawing True Dimension of the object.

Examples:

1. Dimension carried on the drawing = 4mm.True dimension= 40mm

Scale = 4 40 = 1:10

2. Calculating drawing dimension of a line having a true dimension of 543 mm toa scale of 1/10.

If a true dimension of 10mm is represented as 1mm, a true dimensionof 543mm is represented as X

Then 10 mm ----------------

1 mm543 mm----------------X mm

We have 1/10= x 543 or X= 54.3mm.Therefore, a true dimension of 543mm is represented to a scale of 1/10 by a

length of 54.3mm.

2.6.1: AN EXAMPLE OF SCALING A DRAWING

2.7: LETTERING METHODS

Lettering is more as freehand drawing and rather of being writing. Therefore the six

fundamental strokes and their direction for freehand drawing are basic procedures forlettering.


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There are a number of necessary steps in learning lettering, and they include the

following:

Knowledge of proposition and form of letters and the orders of the stroke.Knowledge of the composition the spacing of letters and words.Persistent practices.

Capital letters are preferred to lower case letters since they are easier to read on

reduced size drawing prints although lower case letters are used where they from of a

symbol or an abbreviation.

Attention is drawn the standard to the letters and characters. Table (2.1) below give

the recommendation for minimum size on particular drawing sheets:

Application Drawing Sheets Size Minimum character height

Drawing numbers, etc. A0, A1, A2 and A3

A4

5 mm

3 mm

Dimension and notes A0

A1, A2, A3 and A4

3.5 mm

2.5 mm

Table (2.1) Recommendations for minimum size of lettering on drawing sheets

The spaces between lines of lettering should be consistent and preferably not less than

half of the character height.

There are two fundamental methods of writing the graphic languages freehand and

with instruments. The direction of pencil movements are shown in Fig. 2.1 and

Fig.2.2.

Fig. (2.1)Vertical Capital Letters & Numerals


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Fig.(2.2)Vertical lower case letter.

2.8 TASK (2):

On a drawing sheet copy the following text in Fig (2.3) using the correct lettering

methods:

Fig (2.3)


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WEEK 3-

3.1: GEOMETRICAL DRAWINGS

3.1.1. Point:It is a non-dimensional geometrical element. It is occurred by Interception ofvarious lines.

3.1.2. Line:It is a 1D geometrical element occurred by moving of a point in various direction.The picture below illustrates lines, drawn in various directions, and other geometrical

elements occurred by these lines.

3.1.3. Plane:A plane is occurred by at least three points or connection of one point and one line.A

plane is always 2D. When the number of element forming a plane increases, shape and

name of the plane will change.

3.2: STRAIGHT LINES AND ANGLES

3.1

Fig. 3.2

Fig. 3.5

Fig. 3.3

Fig. 3.4

Fig. 3.6


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Fig 3.7

Fig 3.9

Fig 3.8

Fig 3.12 Fig 3.13

Fig 3.10

Fig 3.11


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3.3: TRIANGLE

The triangle is a plane figure bounded by three straight sides, the connection of three points at

certain conditions form triangle.

There different type of triangles such as:

1. Scalene tri angle:is a triangle with three unequal sides2. I sosceles tr iangle:is a triangle with two sides and hence two angles equal.3. Equilateral triangle:is a triangle with all the sides and hence all the three angles equal.4. Right-angled tri angle:is a triangle containing one right angle. The side opposite the

right-angle is called the hypotenuse.

3.3.1: CONSTRUCTION OF TRIANGLES

A

B C

Triangle

3 Point

Scalene tr iangle I sosceles triangle

Equilateral

triangle

Right-angled

triangle

Fig. 3.15

Fig. 3.14


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3.4 TASK (3)

1. Construct the following using a pairs of compasses:- 900, 600, 300, 450, 67.50, and 150

2. Line ABis 120mm long divide this line into Ratio 5:3:7.

3. Construct a perpendicular line to line AB60mm long from a point P30mm above the line

and 35mm from B.

4. Construct an equilateral triangle with sides 60 mm long.

5 Construct an isosceles triangle that has a perimeter of 135 mm and an altitude of 55 mm.

6 Construct a triangle with base angles 60 and 45 and an altitude of 76 mm.

7. Construct a triangle with a base of 55 mm, an altitude of 62 mm and a vertical angle of371/2.

8. Construct a triangle with a perimeter measuring 160 mm and sides in the ratio 3:5:6.

9. Construct a triangle with a perimeter of 170 mm-and sides in the ratio 7:3:5.

10. Construct a triangle given that the perimeter is 115 mm, the altitude is 40 mm and the

vertical angle is 45.

Fig. 3.16Fig. 3.16


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Fig 4.3

WEEK 4-

3.5: QUADRILATERALS

QUADRILATERALS:A quadrilateral is a plane figure bounded by four straight sides, the connection

of four points at certain conditions form quadrilaterals.

Below are some examples of quadrilaterals:

3.5.1.squareis a quadrilateral with all four sides of equal length and all its angles are right angles.

3.5.2. rectangleis a quadrilateral with its opposite sides of equal length and all its angles a right

angle.

3.5.3. parallelogramis a quadrilateral with opposite sides equal and therefore parallel.

3.5.4. rhombusis a quadrilateral with all four sides equal.

3.5.5trapeziumis a quadrilateral with one pair of opposite sides parallel.

3.5.6. trapezoidis a quadrilateral with all four sides and angles unequal.

.

3.6: Construction of quadrilaterals3.6.1 Construction of a Parallelogram given

two sides and an angle.1. Draw AD equal to the length of one of the sides.

2. From A construct the known angle.3. Mark off AB equal in length to the other known

side

4. With compass point at B draw an arc equal in

radius to AD.

5. With compass point at D draw an arc equal in

radius to AB. ABCD is the requiredparallelogram

A

B

D

C

Square

4 Point

Fig 4.1

SQUARE RECTANGLE PARALELLOGRA

RHOMBUSTRAPEZIUM

TRAPEZOID

Fig 4.2

a b c

fed


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Fig. 4.5

Fig. 4.4

Fig. 4.6


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3.7: CIRCLES

A circle is a locus of a point which moves so that its always a fixed distance from another

stationary point. The connection of infinite points at certain conditions form circle.

3.7.1: PROPERTIES OF A CIRCLE

3.7.2: Construction involving circles

A

Circle

Infinite point

NOMAL

To draw a tangent to a circle from any point on the

circumference.

1. Draw the radius of the circle.

2. at any point on the circumference of the circle, the

tangent and then radius are perpendicular to each

other. Thus the tangent is found by constructing

an angle of 900

from the point where the radiuscrosses the circumference.

Concentric circles Eccentric circles

Types of circles


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TASK 4

1. Construct a square of side 50 mm. Find the mid-point of each side by construction and join

up the points with straight lines to produce a second square.

2. Construct a square whose diagonal is 68 mm. 12. Construct a square whosediagonal is 85 mm.

3. Construct a parallelogram given two sides 42 mm and 90 mm long, and the angle

between them 67. 14. Construct a rectangle which has a diagonal 55 mm long and

one side 35 mm long.

4 Construct a rhombus if the diagonal is 75 mm long and one side is 44 mm long.

5 Construct a trapezium given that the parallel sides are 50 mm and 80 mm long and are 45

mm apart.


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WEEK 5

3.7.3: CONSTRUCTIONS INVOLVING CIRCLES

5.1.1. To construct the

circumference of a circle, given the

diameter.1. Draw a semi circle of the given

diameter AB, center O.

2. From B mark off three times thediameter, BC.

3. From O draw a line at 300to OA tomeet the semi circle in D.

4. From D draw a line perpendicular toOA to meet OA in E.

5. Join EC, EC is the requiredcircumference.

5

4.0: TANGENCY

4.1: CONSTRUCTION OF TANGENT

To construct a tangent from a

point P to a circle, center O

1. Joint OP.2. Erect a semi-circle on to cut

the circle in A. PA produced is

the required tangent.

FIG. 5.1

FIG. 5.4

FIG. 5.2

FIG. 5.3


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5.0: POLYGONS

A polygon is a plane figure bounded by more than four straight sides. There are two classes of polygons,regular and irregular polygons.

A regular polygon is one that has all its sides equal and therefore all its exterior angles equal and its interiorangles equal.

An irregular polygon is the one that has unequal sides and also unequal angles (both interior and exterior).

Polygons are frequently referred to have particular names. Some of these are listed below.

A pentagonis a plane figure bounded by five sides.A hexagonis a plane figure bounded by six sides.A heptagonis a plane figure bounded by seven sides.

An octagonis plane figure bounded by eight sides.

A nonagonis a plane figure bounded by nine sides.A decagonis a plane figure bounded by ten sides.Etc.

CONSTRUCTION OF POLYGONS:

pentagonhexagon

octagon

Fig. 5.7Fig. 5.8


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Method 3:1. Draw a line GA equal in length to one of the side2. Bisect GA.3. From A construct an angle of 450to intersect the bisector at point 4.4. From G construct an angle of 600to intersect the bisector at point 6.5. Bisect between points 4 and 6 to give point 5. Point 4 is the centre of a circle

containing a square: point 5 is a the centre of a circle containing a pentagon.

Point 6 is the centre of a circle containing a hexagon. By marking off pointsat similar distances the centers of circles containing any regular polygon canbe obtained.

6. Mark off point 7 so that 6 to 7 = 5 to 6 etc.7. With centre at point 7 draw a circle, radius 7 to A (=7 to G).8. Step off the sides of the figure from A to B, B to C, etc. ABCDEFG is the

required heptagon.

Fig 5.9

Fig. 5.10

Fig. 5.11


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5.2: TASK SHEET 5

1. Construct a regular hexagon, 45 mm side.

2. Construct a regular hexagon if the diameter is 75 mm. 19. Construct a regular hexagon

within an 80 mm diameter circle. The corners of the hexagon must all lie on the

circumference of the circle.

3. Construct a square, side 100 mm. Within the square, construct a regular octagon. Fouralternate sides of the octagon must lie on the sides of the square. 21. Construct the

following regular polygons:

a pentagon, side 65 mm,

a heptagon, side 55 mm,

a nonagon, side 45 mm,

a decagon, side 35 mm.

4 Construct a regular pentagon, diameter 82 mm.

5 Construct a regular heptagon within a circle, radius 60 mm. The corners of the heptagon

must lie on the circumference of the circle.

Fig. 5.12


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WEEK 6

6.0: ELLIPSE:

An ellipse is the locus of a point which moves sothat its distance from a fixed point (called the

focus) bears a constant ratio, always less than 1, to

its perpendicular distance from a straight line

(called directrix).

6.1 PROPERTIES OF AN ELLIPSE:An ellipse has two foci, major axis, minor axis and

two directrices.

6.2 CONSTRUCTIONS OF ELLIPSE:

A. To construct an ellipse usingconcentric circles method.1. Draw two concentric circles, radii = half (1/2)

major and half (1/2) minor axes.

2. divide the circle into a number of sectors.(12 0r 8).

3. where the sector lines cross the smallercircle, draw the horizontal lines cross thelarger circle, draw the vertical line to meetthe horizontal lines.

4. draw a neat curve through the intersections.B. To construct an ellipse using

rectangular method.1. Draw a rectangle, length and breadth equal to

the major and minor axes2. Divide the two shorter sides of the rectangle

in the same even numbers of equal parts.Divide the major axis into the same numberof equal parts.

3. from the points where the minor axis crosses the edge of the rectangle, draw the intersectinglines as shown in figure 6.3

4. Draw a neat curve through the intersections.

Fig. 6.1

Fig. 6.2

Fig. 6.3


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C. To construct an ellipse using trammel method.A trammel is a piece of stiff paper or card with a straight edge.

1. Mark the trammel with a pencil so that half the major and minor axes are marked from thepoint P

2. keep B on the minor axis ,A on the major axis and slide the trammel.3. mark at frequent intervals the position of P. Figure 6.4 shows the trammel in position for

plotting the top half of the ellipse; to plot the bottom half , A stays on the major axis and B goesabove the major axis, still on the minor axis.

D. To construct the normal and the tangent of an ellipse, and to find thefoci.

1. Normal:Normal at any point P. Draw two lines from P, one to each focus and bisect theangle thus formed. This bisector is a normal to the ellipse.

2. Tangent: Tangent at any point P. since the tangent and normal are perpendicular to eachother by definition, construct the normal and erect a perpendicular to it from P. this

perpendicular is the tangent.3. Foci: Foci with compasses set at a radius of half (1/2) major axis, center at the point where

the minor axis crosses the top (or the bottom) of the ellipse, strike an arc to cut the majoraxis twice, these are the foci.

Fig. 6.4

Fig. 6.5

FOCI

TANGENT

Fig. 6.6


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TASK SHEET 6

1. Fig. T6.1 shows an elliptical fish-pond for a small garden. The ell ipse is 1440 mm long and

720 mm wide. Using a scale of 1/12 draw a true elliptical shape of the pond. (Do not

draw the surrounding stones.)All construction must be shown.

2 Fig. T6.2 shows a section, based on an ellipse, for a handrail which requires cutting to

form a bend so that the horizontal overall distance is increased from 112 mm to 125

mm. Construct the given figures and show the tangent construction at P and P1.Show the true shape of the cut when the horizontal distance is increased from 112 mm

to 125 mm.

FIG. T6.1

FIG T6.2


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WEEK 7:

7.0: ISOMETRIC PROJECTION

Isometric is a mathematical method of

constructing a three dimensional (3D)

object without using perspective.

Isometric was an attempt to make

drawings more and more realistic.

The mathematics involved mean that all

lengths when drawn at 30 degrees can be

drawn using their true length.

An isometric drawing shows two sides of

the object and the top or bottom of theobject (FIG. 7.1). All vertical lines are

drawn vertically, but all horizontal lines

are drawn at 30 degrees to the horizontal.

Isometric is an easy method of

constructing a reasonable 3D images.

(Fig. 7.1)

7.1 HOW TO DRAW IN ISOMETRIC

PROJECTION:

To draw in isometric you will need a 30/60

degree set square (FIG. 7.2). Follow the steps

below to draw a box in isometric.

(Fig. 7.2)

1.Draw the Front vertical edge of the cube 2.The sides of the box are drawn at 30 degrees to thehorizontal to the required length.


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3.Draw in the back verticals 4.Drawn in top view with all lines drawn 30

degrees to the horizontalNote: All lengths are drawn as actual lengths in standard isometric.

Figures 7.3 to 7.6 illustrate four (4) isometric pictorial drawing of components, study

the drawing and by using scale 1:1 re-draw them.

Note: Al l dimensions are in mm

Fi . 7.3 Fi . 7.4

Fi . 7.5 Fi . 7.6


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TASK SHEET (7)

Figures T7.1 to T7.4 shows four (4) isometric pictorial drawing of components,

study the drawing and by using proper drawing tools and scale 1:1 re-draw the

isometric pictorial drawings.


Fig. T7.1 Fig.T7.2

Fig. T7.3 Fig. T7.4


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WEEK 8

8.0: ORHTOGRAPHIC PROJECTION

Orthographic projection is a mean of representing a three-dimensional object

(Fig.8.1) in two dimensions (2D). It uses multiple views of the object, from points of

view rotated about the object's center through increments of 90.

The views are positioned relative to each other

according to either of two schemes: first-Angleor

third-Angleprojection. In each, the appearances of

views may be thought of as being projected onto

planes that form a transparent "box" around the

object. Figure (8.2) demonstrate the views of an

object using 1St

. Angle and 3rd

. Angle projections.

(Fig. 8.1)- Orthographic projection

Fig. (8.2)- Illustrating the difference between 1st. and 3

rd. Angles projection
http://en.wikipedia.org/wiki/Dimensionhttp://en.wikipedia.org/wiki/Dimensionhttp://en.wikipedia.org/wiki/Dimensionhttp://en.wikipedia.org/wiki/Dimension


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8.1 THREE VIEW OF AN OBJECT IN FIRST AND THRID

ANGLE OF PROJECTIONS

Figures (8.3 to 8.6) shows isometric pictorial drawing of a number of components,

study the drawing and using 1stand 3rdangle of projection and a scale of 1:1 draw the

following:

A front view in direction "A". Side view in direction "B". Top view in direction "C". Note: Al l dimensions are in mm

Fig. (8.3) Fig. (8.4)

Fig. (8.5) Fig. (8.6)


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8.2 THE MAIN FEATURES OF THE SIX VIEW OF AN

OBJECT

8.2.1 INTRODUCTION

Any object can be viewed from six mutually perpendicular directions, as shown in

Figure (8.7) below. Thus, six views may be drawn if necessary. These six views are

always arranged as shown below, which the American National Standard arrangement

of views. The top, front, and bottom views line up vertically, while the rear, left-side,

front, and right-side views line up horizontally.

Fig. (8.7)


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Fig. (8.8)

If the front view is imagined to be the object itself, the right-side view is obtained by

looking toward the right side of the front view, as shown by the arrow RS. Likewise,

if the right-side view is imagined to be the object, the front view is obtained by

looking toward the left side of the right-side view, as shown by the arrow F.

The same relation exists between any two adjacent views.

Obviously, the six views may be obtained either by shifting the object with respect to

the observer, as we have seen, or by shifting the observer with respect to the object

Fig. (8.8).


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8.3 ONE POINT PERSPECTIVE:

Using one point perspective (Fig.8.9),

parallel lines converge to one pointsomewhere in the distance. This point

is called the vanishing point (VP).

This gives objects an impression of

depth.

(Fig.8.9)

The sides of an object diminish

towards the vanishing point. All

vertical and horizontal lines though

are drawn with no perspective. I.e.

face on.

One point perspective though is of

limited use, the main problem being

that the perspective is too pronounced

for small products making themlooking bigger than they actually are.

(Fig 8.10)

(Fig 8.10)

Although it is possible to sketch

products in one point perspective, the

perspective is too aggressive on the

eye making products look bigger than

they actually are.(Fig 8.11).

(Fig 8.11)


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8.4 TWO POINT PERSPECTIVE

Two Points Perspective is a much more

useful drawing system than the simpler

One Point Perspective. Objects drawn in

two point perspective have a morenatural look (Fig 8.12).

In two point perspective the sides of the

object vanish to one of two vanishing

points on the horizon. Vertical lines in

the object have no perspective applied to

them.

By altering the proximity of the

vanishing points to the object, you canmake the object look big or small (Fig.

8.13).

(Fig. 8.12 )

(Fig 8.13)

Fig (8.13) Shows affect of different locations of Vanishing Points


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8.5 THREE POINT PERSPECTIVE

Three points perspective is a development of

two points perspective. Like two point it has

two vanishing points somewhere on the

horizon. But three points perspective also has avanishing point somewhere above or below the

horizon which the vertical vanish to.

The nearer the vanishing point is to the object,

the bigger the object looks. Look at these

buildings (FIG.8.14), all the vanishing points

are too close. This has caused an excessive

amount of vertical perspective. Learning how

to apply vertical perspective is the key to

making your drawings realistic.

(Fig 8.14)

In general most designers create drawings with a

vanishing point far below the horizon so that thedepth added to the verticals is only slight. In

many cases the vanishing point is not even on

the paper (FIG. 8.15). Learning how to apply

vertical perspective will make your drawings

more and more realistic.

(FIG.8.15)


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8.6 TASK SHEET (8.1)

Figures (T13a to T13d) shown are isometric pictorial drawings for a number of

components, study the drawing and using 1stand 3rdangle of projection with scale of

1:1 draw the following:

A front view in direction "A". Side view in direction "B". Top view in direction "C".


Fig. (T8.1a) Fig. (T8.1b)

Fig. (T8.3c) Fig. (T8.4d)


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WEEK (9):

8.7 MULTI-VIEWS DRAWING USING 1ST

& 3RD

ANGLE OF

PROJECTION

8.7.1 Multi views projection:

Multi views projection is a mean of producing the true shape and dimension of all

details of three-dimensional object or two-dimensional plane surface such as tile

drawing paper. For this reason, this method of projection is universally used for the

production of working drawing, which is intended for manufacturing purposes.

Fig. 9.1- Multi-views projection

In multi-views projection, the observer looks directly at each face of the object and

draws what can be seen directly (90 Degree rays). Consecutively, other sides are also

seen and drawn in the same way (Fig. 9.1).

Hence, there are two system of multi-views projection that is acceptable as British

standard (Fig. 9.2), these are known as:

1. First Angle (1stAngle) or European projection.2. Third Angle (3rdAngle) or American projection.


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Fig.9.2- Different Angles of projections


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8.8 THE DIFFERENCES BETWEEN 1st & 3

rd ANGLE OF

PROJECTION

8.8.1 FIRST-ANGLE PROJECTION

In first-angle projection, each view of

the object is projected in the direction

(sense) of sight of the object, onto the

interior walls of the box Fig.9.3.

Fig.9.3

A two-dimensional representation of the object

is then created by "unfolding" the box, to view

all of the interiorwalls Fig.9.4.

Fig.9.4

Fig.9.5


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8.8.2 THIRD-ANGLE PROJECTION

In third-angle projection, each view of

the object is projected opposite to thedirection (sense) of sight, onto the

(transparent) exterior walls of the box

Fig.9.6

Fig.9.6

A two-dimensional representation of the

object is then created by unfolding the box, to

view all of the exteriorwalls Fig.9.7.

Fig.9.7

Fig.9.8


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8.9 TASK (8.2)

1. Figures T8.2a and T8.2b show two (2) isometric pictorial drawing of

components, study the drawing and by using scale 1:1 draw the following:

Fig. (T8.2a) use 1st

angle of projection draw,1- Front view 2 -Side view 3-Top view.

Fig. T8.2a

Fig (T8.2b) use 3stangle of projection draw,1- Front view 2-Side view 3 - Topview

Fig. T8.2b


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2. Fig T8.2c and T8.2d show two (2) isometric pictorial drawing of components,study the drawing and by using scale 1:1 and third angle of projection draw

the following:- Front view- Side view - Top view

Fig T8.2c

Fig T8.2d


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WEEK -10

9.0: ABBREVIATIONS AND SYMBOLS USED ON

MECHANICAL AND ELECTRICAL DRAWINGS.

9.1: INTRODUCTION

There is a number of common engineering terms and expression, which are frequently

replaced by abbreviation or symbols on drawing, to save space and drafting time. This

will include the electrical, electronic, pneumatic and hydraulic symbols (Table

10.1).

9.2: TECHNICAL DRAWING SYMBOLS

Table (10.1)


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9.3: MECHANICAL CONVENTION

There are many common engineering features which are difficult to draw in full. In

order to save drafting time and spaces on drawing, these features are represented in

simple conventional form as show in Table 10.2 below.

Table (10.2)


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9.4: ELECTRICAL CONVENTION

Table (10.3)


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9.9 TASK (10)

1) The drawing in Figure (10.6) illustrates assembled mechanical parts, study the

drawing then list the items below accordingly.

Fig. (10.6)

2) The drawing in Figure (10.7) illustrates a pneumatic/Hydraulic diagram, study the

drawing then list the items in a tabular form below accordingly.

Figure (10.7)


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3) The drawing in Figure (10.8) illustrates an electrical circuit, study the drawing and

then list the items below accordingly.

Figure (87)

Figure (10.8)


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WEEK11:

10.0 MISSING VIEW

In orthographic projection, the object has principle dimensions, width, height, and

depth which are fixed terms used for dimensions of the three views.

Note that the front view shows only the height and width of the object, the top view

shows the depth and width only. In fact, any one view of three-dimensional object can

show only two dimensions, the third dimension will be found in an adjacent view Fig.

(11.1).

Fig. (11.1).

Note that:

The top view is the same width as front view. The top view is placed directly above or below the front view depending

on the angle of projection (1stor 3rd).

The same relation exists between front and side view, same height. The side view is placed directly right or left to the front view, (right side

view or left side view).


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10.1 FIRST ANGLE OF PROJECTION:The Fig. (11.2) is a pictorial drawing of given object, three-views of which arerequired using first angle of projection. Each corner of the object is given a number as

shown. At I the top view and the front view are shown, with each corner properly

numbered in both views. Each number appears twice, once in the top view and again

front view.

Fig. (11.2)

At I point 1 is visible in both views, therefore placed outside the corner in both views.

however point 2 is visible in the top view and number is placed outside, while in the

front view it is invisible and placed inside.


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10.2 THIRD ANGLE OF PROJECTION:

Fig. (11.3)

Fig. (11.4)


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Fig (11.5)

Fig (11.6)


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10.3 TASK SHEET (11)

Complete the drawing shown in Fig (T11) to produce the third missing view

Fig. T11


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WEEK (12):

11.0 FREEHAND SKETCHING

11.1 INTRODUCTION:

Free-hand sketching is used extensively during the early design phases as an

important tool for conveying ideas, guiding the thought process, and serving as

documentation. Unfortunately there is little computer support for sketching. The first

step in building a sketch understanding system is generating more meaningful

descriptions of free-hand.

One of the advantages of freehand sketching is it require only few simple items such

as

1. Pencil (soft pencil i.e. HB).2. Paper (A3 & A4).3. Eraser.

When sketches are made on the field, where an

accurate record is required, a sketching pad with

clipboard are frequently used (Fig.12.1). Often

clipboard is employed to hold the paper.

(Fig. 12.1)

11.2 General notes before

sketching:

1. The pencil should be held naturally,about 40mm from general direction of

the line down.

2. Place the paper rotated position so thehorizontal edge is perpendicular to the

natural position of your forearm.3. When ruled paper is being used for

sketching try to locate the sketched line

on ruling line

(Fig.12.2).

4. Use your imagination and common sensewhen choosing the most suitable angle of

view.

(Fig. 12.2)


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1) Demonstration of sketching technique of horizontal and vertical lines (Fig. 12.3)

2) Demonstration the sketching technique of circles (Fig. 12.4)

3) Demonstration the sketching technique of an arc (Fig. 12.5)


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4) Demonstration the sketching technique of an ellipse (Fig. 12.6):

5) Demonstration the sketching technique of an arc (Fig. 12.7):


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11.3 Task sheet (12)

1) Use A4 sheet with a pencil and try to draw the lines as shown in Fig. T12.1 below.

Fig. T12.1

2) Use A4 sheet with a pencil and try to draw the component shown in Fig. T12.2

below.

Fig. T12.2


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WEEK13:

12.0 SKETCHING THE VIEWS FROM AN ACTUAL OBJECT

In industry a complete and clear description of the shape and size of an object is

necessary to be able to make it. In order to provide all dimensions and information

clearly and accurately a number of views are used. To sketch these views from an

actual object the following steps should be followed:

1. Look at the object carefully and choose the right position that shows the best three

main views (Fig. 13.1).

(Fig. 13.1)

2. Estimate the proportions carefully, sketch

lightly the rectangles of views and set them

according to the projection method (1st

or 3rd

angle) chosen.

3. Hold the object, keeping the front view

toward you (Fig. 13.2), and then start sketching

the front view.

(Fig. 13.2)


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4. To get the top view, revolve the object so as

to bring the top toward you, then sketch the top

view (Fig. 13.3)

(Fig. 13.3)

5. To get the right side view, revolve the object

so as to bring the side view in position relative

to the front view, and then sketch the side view

(Fig. 13.4)

(Fig. 13.4)

6. make sure the relationships between all

views are carried out correctly (Fig. 13.5)

(Fig. 13.5)


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12.1 OBLIQUE SKETCHING:

Another method for pictorial is sketching the

oblique sketching. To made an oblique sketch

from an actual object follow these steps:

1. hold the object vertically, making sure most

circular features in front of you (Fig. 13.6)

(Fig. 13.6)

2. Sketch the front face of the object in

suitable proportional dimensions (Fig. 13.7)

(Fig. 13.7)

3. Sketch the receding lines parallel to each

other or a convenient angle between (30-

45) with horizontal, these lines may in full

length to sketch a caviller oblique or may be

one half sizes to sketch cabinet oblique.

(Fig. 13.8)

4. Complete the required sketch as

explained for isometric sketch previously.

(Fig. 13.9)


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12.2 TASK SHEET 13

Fig. T13 shows an isometric pictorial drawing of a component; study the drawing

and then using scale 1:1 draw the following:

An isometric pictorial drawing (freehand). The following views (freehand).

A front view. Side view. Top view.


Fig. T13


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WEEK 14

13.0 INTERSECTION AND DEVELOPMENT:

When two solid interpenetrate, a line of intersection is formed. Many object are formed by acollection of geometrical shapes such as cubes, cones, spheres, cylinders, prisms, pyramids, etc,

and where any two of these shapes meet, some sort of curves of intersections or interpenetrations

are formed. It is necessary to be able to draw these curves to complete drawings in orthographic

projection or to draw patterns and developments.

Construction:

Interpenetration:13.1 CONSTRUCTION OF SOLID WITH

INTERPENETRATION

13.2 Two dissimilar square prisms

meeting at right angles. Fig. 14.1The end elevation shows where corners 1 and 3

meet the larger prism and these are projected across

to the front elevation the plan shows where corners

2 and 4 meet the larger prism and this is projected

up to the front elevation.

13.3 Two dissimilar square prisms

meeting at an angle. Fig 14.2The front elevation shows where corners one 1 and

3 meet the larger prism. The plan shows where

corners 2 and 4 meet the larger prism and this isprojected down to the front elevation.

3RD

ANGLE PROJECTION

Fig 14.1

Fig 14.2


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13.4 Two dissimilar hexagonal prisms

meeting at an angle. Fig. 14.3The front elevation shows corners 3 and 6 meet the

larger prism. The plan shows corners 1,2,4, and 5meet the larger prism and these are projected up to

the front elevation.

13.5 Two dissimilar cylinders meeting

at right angles. Fig.14.4The smaller cylinder is divided in to 12 equal

sector on the front elevation and on plan, the plan

shows where these sectors meet the largercylinder and these intersections are projected

down to the front elevation to meet there

corresponding sector at 1,2,3,etc

Fig 14.3

Fig 14.4


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3.6 Two dissimilar cylindersmeeting at an angle. Fig 14.5

The method is identical with above

principle. The smaller cylinder is

divided in to 12 equal sector on the

front elevation and on plan, the planshows where these sectors meet the

larger cylinder and these intersections

are projected down to the front

elevation to meet there corresponding

sector at 1,2,3,etc

Fig 14.5


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13.7 TASK SHEET (14)


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WEEK 15

14.0 DEVELOPMENT

Many articles such as cans, pipes, elbows, boxes, etc are manufactured from thin sheet materials.

Generally a template is produced from an orthographic drawing when small quantities are required.

The figures below illustrate some of the more commonly used development in pattern marking. An

example of an elbow joint is shown developed in fig. 15.1. The length of the circumference has been

calculated and divided into twelve equal parts. A part plan, divided into six parts, has the division

lines projected up to the joint, then across to the appropriate point on the pattern. It is normal practice

on a development drawing to leave the joint along the shortest edge; however, on part B the pattern

can be cut more economically if the joint on this half is turned through 180.

A typical interpenetration curve is given in fig. 15.2. The

development of part of the cylindrical portion is shown viewedfrom the

inside. The chordal distances on the inverted plan have been plotted on

either side of the centre line of the hole, and the corresponding heights

have been projected from the front elevation. The method of drawing

pattern for the branch is identical to that shown for the two piece elbow

in fig. 15.1

An example of radial-line development is given in fig. 15.3. The

dimensions required to make the development are the circumferenceof the base and the slant height of the cone. The chordal distances

from the plan view have been used to mark the length of arc required

for the pattern; alternatively, for a higher degree of accuracy, the

angle can be calculated and then subdivided. In the front elevation, lines

0 1 and 07 are true lengths, and distances OG and OA have been plotted

directly onto the pattern. The lines 02 to 06 inclusive are not true

lengths, and, where these lines cross the sloping face on the top of the

conical frustum, horizontal lines have been projected to the side of the

cone and been marked B, C, D, E, and F. True lengths OF, OE, OD, OC,

and OB are then marked on the pattern. This procedure is repeated for the

other half of the cone. The view

Fig 15.2

Fig 15.1


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on the sloping face will be an ellipse,

Part of a square pyramid is illustrated in

fig. 15.4. The pattern is formed by

drawing an arc of radius OA and

stepping off around the curve the

lengths of the base, joining the pointsobtained to the apex O. Distances OF

The development of part of a hexagonal

pyramid is shown in fig. 15.5. The

method is very similar to that given in

the previous example, but note that lines

OB, OC, OD, OE, and OF are true

lengths obtained by projection from the

elevation.Fig. 15.6 shows an oblique cone

which is developed by triangulation,

where the surface is assumed to beformed from a series of triangularshapes. The base of the cone is dividedinto a convenient number of parts (12 in this case) numbered 0-6 and projected to the frontelevation with lines drawn up to the apex A. Lines OA and 6A are true-length lines, but theother five shown all slope at an angle to the plane of the paper. The true lengths of lines IA,2A, 3A, 4A, and 5A are all equal to the hypotenuse of right-angled triangles where the height is

the projection of the cone height and thebase is obtained from the part plan viewby projecting distances 131, B2, B3,B4, and B5 as indicated.

Assuming that the join will be madealong the shortest edge, the pattern isformed as follows. Start by drawing line

6A, then from A draw an arc on eitherside of the line equalin length to the true length 5A. From

point 6 on the pattern, draw an arc equalto the chordal distance between successive

points on the plan view. This curve willintersect the first arc twice at the pointsmarked 5. Repeat by taking the truelength of line 4A and swinging anotherarc from point A to intersect with chordalarcs from points 5. This process iscontinued as shown on the solution.

Fig. 15.7 shows the development of partof an oblique cone where the procedure

described above is followed. The points ofintersection of the top of the cone withlines 1A, 2A, 3A, 4A, and 5A aretransferred to the appropriate true-lengthconstructions, and true-length distancesfrom the apex A are marked on the patterndrawing.A plan and front elevation is given in

fig. 15.8 of a transition piece which is

formed from two halves of oblique

cylinders and two connecting triangles.

The plan view of the base is divided

Fig 15.3

Fig 15.4


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into 12 equal divisions, the sides at the top

into 6 parts each. Each division at the

bottom of the front elevation is linked

with a line to the similar division at the

top. These lines, P l, Q2, etc., are all the

same length. Commence the patternconstruction by drawing line S4 parallel to

the component. Project lines from points 3

and R, and let these lines intersect with

arcs equal to the chordal distances C,

from the plan view, taken from points 4

and S. Repeat the process and note the

effect that curvature has on the distances

between the lines projected from points P,

Q, R, and S. After completing the pattern

to line Pl, the triangle is added by

swinging an are equal to the length Bfrom point P, which intersects with the arc

shown, radius A. This construction for

part of the pattern is continued as

indicated.

Fig. 15.5

Fig 15.6

RAD C

Fig 15.7


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Fig T15.1

Fig T15.2

14.1 TASK SHEET (15)1. Fig T15.1 shows three pipes, each of

50 mm diameter and of negligible

thickness, with their axes in the same

plane and forming a bend through 90.

Draw:(a) the given view, and (b) the

development of pipe K, using TT as

the joint line.

2. Fig. T15.2 shows the plan and

elevation of a tin-plate dish. Draw the

given views and construct a

development of the dish showing each

side joined to a square base. The planof the base should be part of the

development.

mec 111 technical drawing

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