book for knowledge

8/12/2019 book for knowledge

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Graphical means of expression of technicaldetails without the barrier of a language.

Universal language for engineers

Engineering Drawing

Drawing

Describing any object/ information diagrammatically


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Diagrams/sketches/pictures communication skills

We grasp information easily if it is illustrated withdiagrams, sketches, pictures, etc.

LCA - the world's smallest, light weight, multi-role

supersonic combat aircraft of the world


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AIRBUS A380Source: http://img.stern.de/_content/53/96/539645/A380_500_artikel_500.jpg

Details:largest passenger jet. 80m wingspan and a tail that stands as high

as a seven-storey building, carries more than 550 passengers.


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It would just be impossible to communicate allnecessary details about the LCA/ Airbus A380

verbally or in writing Illustration(picture/drawing) is useful.

A picture/drawing is worth a thousand words..

The LCA/Airbus A380 would be impossible to

create without computer graphics and drawingmodels.

Drawings are the road maps which show how to

manufacture products and structures.


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Impossible to describe the detailsof the building


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Difficult to describe the details of the machine


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Electrical circuit


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Drawing is important for all branches of

engineering.


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Graphical representation of an object Drawing

Engineering drawingA drawing of an objectthat contains all information

-like actual shape, accurate size,manufacturing

methods,etc., required for its construction.

-No construction/manufacturing of any (man -

made) engineering objects is possible withoutengineering drawing.


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What will you learn in this course?

You will learn- How industry communicates technical

information. Visualizationthe ability to mentally control visualinformation.

Graphics theorygeometry and projection techniques. Standardsset of rules that govern how parts are madeand technical drawings are represented.

Conventions commonly accepted practices and methods

used for technical drawings.

Tools devices used to create technical drawings andmodels.

Applicationsthe various uses for technical drawings.


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Engineering drawing is completely differentfrom artistic drawing, which are used toexpress aesthetic, philosophical, andabstract ideas.


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Computer has a major impact on the methods used todesign and create technical drawings.

Design and drafting on computer are cheap and less timeconsuming.

Why we go for manual drawing?

Engineering Drawing

Manual Drawing CADD


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Computer cannot replace the drafting board andequipment as a learning tool.

Once you have learned the basics of mathematics, nowafter class 12, you are allowed the use of calculator

and computer.If basic fundamentals are clear, better use can bemade of the power of the software.

To be an expert in technical drawing, this first course

on Engineering (manual) Drawing is the first step.

Why we go for manual drawing?


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Items required for drawing Items required for drawing

Drawing board

Drawing sheet

Mini-drafter/drafting machine/ T- sqaure

Instrument box containing compass, divider, etc.

Scales

Protractor

French curves

Drawing pencils

EraserDrawing clip/pin/adhesive tape

Sharpener

Duster


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Drawing board must be placed on the tablewith working edge always to be at the leftside.

Working edge


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Last two sizes are normally used for student drawing


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Mini-drafter a miniature version of the drafting machine


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Mini-drafter fixed on drawing board


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Set the protractorhead with referencemark indexing zerodegree.

Fix the clamp of themini-drafter at the topleft corner either alongthe top horizontal edgeof the board or along

the left vertical edge ofthe board.

.contd

Clamping mini drafter


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Place the drawing sheet underneath the scalesof the mini-drafter,

Fix the drawing sheet to the drawing boardwith the scales of the mini-drafter alignedeither with the vertical or the horizontal

borderlines of the drawing sheet.

Clamping mini drafter.. contd


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T- square

Another tool


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Some drawing instruments


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Standard sizes of drawing sheets as per BIS

A2 size


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Layout of drawing sheets

Standard form of arrangement

Important particulars are included

Facilitate quick reading of important particulars quick

references are located easily drawings are prepared atvarious locations and shared

Grids along the horizontal edgesNumerals

Grids along vertical edges Capital letters 25 mm < Length of the grid < 75 mm


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Numbering and lettering start from the corner of

the sheet opposite to the title box and are repeatedon the opposite sides

Numbers and letters are written upright

Repetition of letters or numbers like AA, BB, etc.,

if they exceed that of the alphabets.

Bordersspace left all around in between the

trimmed edges of the sheet- A minimum of 10 mm


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Grid reference system

For all sizes of drawing sheets for easy location ofdrawing within the frame. The length and the widthof the frames are divided into even number ofdivisions.

Number of divisions for a particular sheet dependson complexity of the drawing Not to be followed inthis course.


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Title boxAn important feature a must in every drawingsheet for technical and administrative details

Location - Bottom right corner 185 mm x 65 mm (BIS)

Divided into two zones

Identification zone

Registration or identification number

Drawing title

Name of the legal owner of the drawing, i.e., name of thefirm or the company

Contd


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Additional information zone

Indicative items symbol indicating the system of

projection, main scale of drawing, etc.

Technical items method of indicating surfacetexture, geometric tolerances, etc.

Administrative items

Title box.. contd


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Lay out of a drawing sheet


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Layout of the title box to be adopted in this course

INDIAN INSTITUTE OF TECHNOLOGY KHARAGPUR

TITLE:

SCALE:

NAME:

ROLL NO:

PLATE NO:EVALUATED BY

11075

20

10

15

10

10


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Drawing Pencils

Wooden pencilsare graded and designated by numbers and letters

Mechanical clutch pencilsNot allowed

7B, 6B, 5B, 4B, 3B, 2B, B - in decreasing order of softness andblackness

HBto F Medium grade

H, 2H,3H, 4H, 5H, 6H, 7H, 8H, 9H increasing order of

hardness.

Drawings are done using 2H pencils and finished with H

and HB pencils to be practiced in this course.


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Grades and designation of wooden pencils


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Pencil drawing

In finished drawing, all lines (except construction lines-used to construct the drawing) should be dense, clean anduniform.

Construction line should be drawn very thin and should be

hardly visible in the finished drawing ( they should not beerased).


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Line types


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Line types.CONTD


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Uses of different types of lines in a given drawing


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Uses of different types of lines in a given drawing


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Examples of good and poor drawing techniques for

lines and arcs


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Lettering Writing of titles, sub-titles, dimensions,scales and other details on a drawing

Essential features of lettering legibility, uniformity,ease, rapidity, and suitability for microfilming/photocopying/any other photographic processes

No ornamental and embellishing style of letter

Plain letters and numerals which are clearlydistinguishable from each other in order to avoid any

confusion even in case of slight mutilations


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Lettering BIS: 9609

Single stroke lettering for use in engineeringdrawing width of the stem of the letters andnumerals will be uniformly thick equal to thickness oflines produced by the tip of the pencil.

Single stroke does not mean entire letterwritten without lifting the pencil/pen


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Lettering types

Lettering AHeight of the capital letter is divided into

14 equal parts Lettering BHeight of the capital letter is divided into10 equal parts

H i ht f L tt d N l


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Heights of Letters and Numerals

Height of the capital letters is equal to the heightof the numerals used in dimensioning

Height of letters and numerals different fordifferent purposes


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Specifications of A -Type Lettering


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Specifications of B -Type Lettering


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Standards and Conventions


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Standards and Conventions

No effective communication without an agreed uponstandard of signs or symbols.

Standards and conventions are the alphabet of technicaldrawing, and plane, solid, and descriptive geometry are thescience(grammar) which underlies the graphics language.


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Following the standard rules (grammar) of any language

(Hindi/English) communication of thought betweenpeople becomes easier.

If words in a sentence were presented randomly understanding becomes very difficult.

For effective communication of technical (graphics)informationset of standards and conventions a must.

Standards and Conventions very important


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Conventions commonly accepted practices, rules,

or methods.

Dashed lines are usedto represent hiddenfeatures ofan

engineering drawing..

Hidden lines location

of drilled holesdiameter, in a viewwhere the hole cannotbe directly seen.

St d d t f l th t h t h i l


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Drawings are dimensioned using an accepted set ofstandards such as placing the dimension text such thatit is read from the bottom of the sheet.

Standardsset of rules that govern how technicaldrawings are represented..


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Drawing standards

ANSI American National Standards Institute

ANSI Y14.1 1980 (R1987) Drawing sheet size

and format

ANSI Y 14.2M-1979 (R1987) Line conventions

and lettering

ANSI Y14.5M-1982(R1988) Dimensioning and

tolerances

ANSI Y 14.3-1975(R1987) Multi view and sectional view drawings

ISO International Standards OrganizationJIS Japanese Standards

BIS Bureau of Indian Standards


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Units of Measure

International systems of units (SI) which is based on

the meter.Millimeter (mm) -The common SI unit of measure onengineering drawing.

Individual identification of linear units is not required ifall dimensions on a drawing are in the same unit (mm).

The drawing shall however contain a note:

ALL DIMENSIONS ARE IN MM. (Bottom left

corner outside the title box)


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Dimensioning

Indicating on a drawing, the size of the object andother details essential for its construction andfunction, using lines,numerals, symbols, notes, etc.

Dimensions indicated on a drawing should be thosethat are essential for the production, inspection andfunctioning of the object and should not be mistaken

as those that are required to make the drawing of anobject.


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Dimensioning of anobjectis

accomplished bydimensioning eachelement to indicateits size (size

dimensions) andrelative location(location dimensions)from a center line,base line or finishedsurface.


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Each feature isdimensionedand positionedonly once.

Each feature isdimensionedand positioned

where itsshape shows.


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Size dimensions give the size of the component.

Solid:

Every solid has three dimensions,each of the geometricshapes making up the object must have its height,

width, and depth indicated in the dimensioning.


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Basic geometric shapes used in drawing


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Prismmost common shape

requires three dimensions-give two dimensions on the

principal view and onedimension on the otherviews.

Cylinder


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Cylinder


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Conerequires

two dimensions

diameter of the base

and altitude on the

same view and

length both are

shown preferably on

the rectangular view.


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Right pyramids

requires three

dimensions

dimensions of the

base and altitude.


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Spheres requires

only one dimension diameter.


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Location dimensioning

After the basic geometric shapes have been

dimensioned for size, the location of each relative to theothers must be given.

Locations must be established in height, width and

depth directions.

Rectangular faces are positioned with reference to

their faces, cylinder and conic shapes with reference to

their center lines and their ends.


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Size and Location dimensioning


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Terminology fordimensioning practice

Dimension numericalvalue that defines

the size or geometriccharacteristics of a

feature size 3.5 mmand space between

lines of text 1.5 mm.


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Dimensions showing the

sizes of features, suchas width, height anddepths of the parts andthe diameter of the hole

Dimensions showing the

location and orientationsof features, such aslocation of the center ofthe hole


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Dimension line

A thin, solid line that shows the extent and direction ofa dimension. Dimension lines are broken for insertion ofthe dimension numbers.

Should be placed at least10 mm away from the

outline and all otherparallel dimensions should

be at least 6 mm apart,or more if space permits.

Arrows 3 mm wide and should be 1/3rd as wide as


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Arrows 3 mm wideand should be 1/3rd as wide as

they are long - symbols placed at the end of dimension line

to show the limits of the dimension. Arrows are uniform in

size and style, regardless of the size of the drawing.


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Extension line a thin, solid line perpendicular to a

dimension line, indicating which feature is associatedwith the dimension.

Visible gapthere should be a visible gap of 1.5 mmbetween the features corners and the end of the

extension line.


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Leader line

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

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

Terminated with an arrow touching the part or detail.

On the end opposite the arrow, the leader line willhave a short, horizontal shoulder. Text is extended

from this shoulder such that the text height iscentered with the shoulder line.


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Diameter symbol - a symbol which precedes anumerical value, to indicate that the dimension showsthe diameter of a circle.

Radius symbol R 0.5


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Various types of dimension lines


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Important elements of a dimensioning


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Important elements of a dimensioning


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Dimensioning of angles


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Correct way of dimensioning


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Aligned method Unidirectional method

How to begin your drawing?


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How to begin your drawing?

Clean the drawing board and all the drawing

instruments using duster.Fix the drawing sheet on the drawing board.

Fix the mini-drafter in a convenient position.

Draw border lines using HB pencil..

Complete the title box using HB pencil .

Plan spacing of drawings b/n two problems/views

beforehand.Print the problem number on the left top and then

commence the drawing work.


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Thank you

Source:

Engineering Graphics Communication, Gary R. Betoline, IRWINGraphics Series

Engineering Drawing: plane and Solid Geometry, N.D. Bhatt, CharotarPublishing House, Anand

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