first lecture drawing

04/08/23Engineering Drawing &

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Computer Aided DrawingCode:

Spring 2010

Lecture 1

Nazeer Ahmed AnjumB. Sc (hnr) UET Taxila

M. Sc UET Taxila

Cell No. 0300-5397864

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Marks Distribution

TOTAL MARKS = 100Assignment = 10%Quizzes = 10%Mid Term = 20%Lab. Work = 20%Final = 40%

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INTRODUCTION Outline

Drawing Instruments

Line Types Used in Engineering drawing

Lettering and Drafting Techniques

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Drawing Instruments

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DRAWING INSTRUMENTS

1. Tee Square (T-Square)2. Pencils (HB, H, 2H)3. French Curves or Irregular Curves 4. Adhesive Tape (Paper Tape)5. Handkerchief, duster, Dusting

Brush or Tissue

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DRAWING INSTRUMENTS

6. Set-Squares7. Rubber or Eraser8. Instruments Box9. Erasing Shield10.Protractor11.Pencil Sharpener12.Drawing Sheet13.Sketch Book

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Drawing Board:- It is a plane square

or rectangular piece of wood with a smooth surface.

Size of drawing board varies from 9”×12” – 48”×72”.

Suitable size for student is 20”×24”.

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T-Square

It is used to draw straight lines on the drafting sheet.

It consists of A long strip called blade. Short piece called head. The inner and outer

edges of blade and head are called working edges.

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Drawing Sheet:-

It is a white sheet of paper having enough grains or teeth against which the lead of the pencil may easily work.

The color of the sheet preferred is light cream or buff.

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Drafting Tape (Scotch Tape):-

It is a colorless sticking tape used to fix the sheet on the drawing board.

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Triangles or Set-Square

Two triangles are used in drawing.

A triangle with angles 45°,45° and 90° is called 45 degree triangle.

The other has 30°,60° and 90° angles and is called 30-60 degree triangle.

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Compasses and Dividers:-

Compasses are used to draw circles.

It consists of Two moving arms. One fixed with a

compass needle. The other arm may hold

another needle, pencil, pen etc.

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Pencils:-

It is a basic instrument used for making drawing on the sheet.

It is made of graphite lead .

Pencils are made of various hardness.

Hardness of the pencil is specified by its grade, 9H to 7B.

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Small Knife and Sandpaper:-

It is used to make the required shape of the lead and foam is used for its final cleaning.

It is a small wooden strip pasted with a sandpaper on one side and a small foam on the other end.

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Erasing Shield It is used to remove

extra lines after the completion of a drawing without disturbing the required lines.

It is a thin metallic plate with designs of various shapes.

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Set of Circles (Circle Template)

It is a thin sheet of plastic with circular openings of various sizes.

It is used to draw curves tangent to other circles or simply for drawing the circles.

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French Curves These are used to

draw different curves for the already plotted points and the freehand curves may be changed into smooth curves.

These are made of plastic sheets.

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Starting An Engineering Drawing

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Drawing a Panel:-

Panel is the subscription corner of the drawing, usually drawn at the right bottom of the drawing sheet.

Border of about 1” is left from all sides of the drawing sheet.

Scale: Dwg Name: Checked by & Grade Name: Roll No. Angle of ProjectionBahria University Deptt: Electrical

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Division of Sheet

Front view

Top view

Side view

A= X-(L+W) B= Y-(H+W) 3 3H= Height of object A=Horizontal Spacing L= Length of object B=Vertical SpacingW= Width of object

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Lines:- If we say that Engineering Drawing is

the language of Engineers then lines are the literature of this language.

Lines are the continuous association of points.

Lines are classified:- According to Thickness. According to Shape. According to Darkness.

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Lines used in Engineering Drawings:--

Outlines.Dashed lines.Centre lines.Dimension lines.Construction lines.Hatching lines.Cutting plane lines.Break lines.

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Lines drawn to represent visible edges and surface boundaries. These are also called principal lines.

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Interior or hidden edges and surfaces are shown by dashed lines. Also called dotted lines. They are of medium thickness. They are short dashed lines of about 3-4mm with 1mm distance between them.

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These lines indicate axes of cylindrical, conical or spherical objects and the centers of circles. These are medium thick lines consisting of long and short dashes, long dashes of 6-8mm and 1mm distance between them.

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These are continuous thin lines terminated at the outer ends by pointed arrow-heads.

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These are thin lines drawn during the drawing to help in drawing complex geometrical structures.

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These are thin lines drawn parallel to each other at about 3mm. These lines show the presence of material while object is cut through.

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These lines show the location of the cutting plane. It is thin & long chain line with two small dashes of about 3-4mm and a long dash of about 6-8mm width.

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These lines show imaginary boundaries of the object or to skip up very long part of the object of similar width.Long break line

Short break line

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Lettering and Drafting Techniques :

Two methods of lettering are available to the Mechanical/electronics drafter.

1. Freehand lettering.

2. Lettering accomplished with lettering guide.

• All lettering on a diagram must be of high quality and legible regardless of the final reduction size requirement of the drawing.

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Styles of Lettering :

The predominant lettering style for Mechanical drawings is the single-stroke, uppercase, commercial Times New Roman.

Single stroke means that the required thickness or weight of each letter is formed using one stroke.

• Uppercase indicates that all letters are capitalized.

• Times New Roman style is one in which all strokes of each letter are even.

(stroke : a line made by single movement of pen or brush in writing or painting.)

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Styles of Lettering :

• Either vertical or inclined letters are acceptable, but preferable are vertical characters.

• Only one type of lettering, either vertical or inclined, should appear on a drawing.

• Notes, either general or localized, are placed on a drawing to align to the bottom of the drawing.

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Vertical Letters and Numerals

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Inclined Letters and Numerals

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Fractions and Mixed Numbers.

Fractions and mixed numbers are drawn with a horizontal bar as shown.

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Spacing and Sizes :

•Spacing between words should not be less than the height of one letter.

•Spacing between lines should not be less than the height of letters.

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Lettering Aids.

Ames guide provides guidelines as illustrated on right.

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Lettering Aids

•This figure shows the use of guide in conjunction with a T-square.

Guidelines should be light enough that they will not reproduce when the drawing is copied.

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LOCI OF POINTSLocus:- A locus (Plural Loci) is a path of

a point which moves in space.

Locus of a Point:- The locus of a point ‘P’ moving in a plane about another point ‘O’ in such a way that its distance from it is constant is a circle of radius equal to OP.

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LOCI OF POINTS The locus of a point ‘P’ moving in a

plane in such a way that its distance from a fixed line AB is constant, is a line through ‘P’, ||e to the fixed line.

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LOCI OF POINTS When the fixed line is an arc of a circle,

the locus will be another arc drawn through ‘P’ with the same center.

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LOCI OF POINTS

The locus of a point equidistant from two fixed points A & B in same plane is the perpendicular bisector of the line joining the two points.

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LOCI OF POINTS

The locus of a point equidistant from two fixed non-parallel straight lines AB & CD will be a straight line bisecting the angle b/w them.

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ExampleDraw the locus of a point equidistant

from a fixed straight line & a fixed point.

SolutionLet AB be the given straight line & C be the given point.

CP 1 2 3 4DFrom C draw a perpendicular

to AB at D, Bisect CA at P, P is the locus point.Make a number of points 1, 2, 3, etc., on PC & through them draw lines ||e to AB.

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Example Cond….

Now taking center C and radius D1, draw an arc cutting the line through 1 at P1 and P1’. Again with the same center & radius D2, draw an arc cutting the line through 2 at P2 & P2

’. Similarly, obtain points & through them a smooth curve which is the required locus of P.

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ASSIGNMENT

1. Draw a point equidistant from two given circles of unequal diameters.

2. Draw the loci of Crank Mechanism.

first lecture drawing

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