Informationabouttheshape,Size,Featuresand

1.INTRODUCTION

Whatistechnicaldrawing?

Itisaformalandprecisewayofcommunicating

informationabouttheshape,size,featuresand

precisionofphysicalobjects.

Auniversallanguageofengineeringusedinthe

designprocessforsolvingproblems,quicklyand

accuratelyvisualizingobjects,andconducting

analysis.

Agraphicalrepresentationofobjectsandstructures.

Itcanbedonebyusingfreehand,mechanical,or

computermethods

Whousetechnicaldrawing?

SketchingorDrawing

Wewilltreat"sketching"and"drawing"asone.

"Sketching"generallymeansfreehanddrawing.

"Drawing"usuallymeansusingdrawinginstruments,

fromcompassestocomputerstobringprecisiontothe

drawings.

Manualdraftingtoolsfortechnical

drawing

Mechanicalpencils:0.7and

0.5mm,or0.5and0.3mm

combinations;Pencilgrades

–HBandH,orFand2H

combinations)

Compassandonedivider

Onesetof45-and30/60-

degreetriangles

Scales(oneEnglishunitand

oneMetricunit)

Irregularcurve(Frenchcurve)

Protractor

Onegooderaser

Useofdraftingtools–afewexamples

Pencilgrades

2.LINES

2.1.Generalinformation

Generally,technicaldrawingistheexpressionofbodies

(ormatters)bylines.

Piecesarecomposedofvariablegeometriccomponent.

Sidesandsurfacesofthesecomponentsarevisiblebut

someofthemcannotbeseenbecausetheyarebehind

thebacksides.

Toobtainfullandpreciseinfoaboutthepiece,drawing

shouldbedonebyusingvariablelines(insteadofusing

samelines).Moreover,theselinesshouldbedrawnat

samethicknessandshapebyeveryone.Theshapesand

thicknessesoflinesaregiveninTS88.

·Samelineshapesand

thicknessesareusedinthis

drawing.Thereforeitisvery

difficulttohaveanideaof

theshapesanddimensions

ofthepiece.

A-A

A A

· Thisfigureshowsthesamepiece,whichisdrawnbyusing

variablelinesdifferinshapesandthicknesstoshowvisible

andinvisiblelines,axisanddimensions.Inthisway,one

haveanfullideaofthepiece.

Typeoflines / Applicationplaces
A / Continuousline
(thick) / A1-Surroundingsandsidesofthematters.
A2-Endofthescrew

2.2-Typeoflines

Accordingtothe“TS88technicaldrawingstandard”publishedat1978,

linesareclassifiedas9types:

tool.

D1-Invisiblesurroundingandsidesofthematter.

Dashline(thin)*

E1-Axislinesofsymmetricaldrawing

Dashlinewithpoint(thin)E2-Infrontofsectionplanes

Sectionplanewiththickendsand

F1-Todrawthetracesatsectionplane

thinmidpoints.

G-Tostatetheplacewhichwillprocessed

Dashlinewithpoint(thick)

Dashlinewithtwopoints

(thin)

additionally.(tocoat,toharden,etc.)

H1-Toshowthesurroundingsofneighborpieces

H2-Tostatethesecondarysituationofmoving

pieces.Tostatethecenterofgravity

2.3-Drawingoflines

a-Thicknessoflinesshouldbedrawnaccordingtothe

standards.

b-Atfreehanddrawing:

ContinuousandthicklinesshouldbedrawnbyBor2B

pencil.

ContinuousandthinlinesshouldbedrawnbyHor2H

pencil.

c-Dashlinesshouldbedrawnatequalspacesand

thickness.They shouldbe3∼6mm,or0,8~1,5mm

accordingtothesizeofthe picture.

d-Dashlineswithpointshouldbedrawnaccordingtothesizeofthe

picturewithbelowmentionedsizes.

7....15111

11111

111

f-Intersectedcontinuouslinesshouldnotbeoverflowedor

uncompletedattheinterceptpoints.Thicknessesshouldbesame

andcornersshouldbesharp.

g-Junctionsofcirclearcsandlinesshouldbetangent.

h-Minimumspaceoftwoparallellinesshouldnotbeless

thantwotimesofthethicklines.

d:Thicknessoflines.

3-GEOMETRICALDRAWINGS

Anymatterisoccurredbygeometricalelementslikepoints,

linesandplanes.Belowpictureshowsthistypeofmatter:

Plane

surface

Line

Arc

Point

Ellipse

surface

Curvedline

surface

Tangents

HelixSphere

cover

Square

prism

Intercept

lines

Parallel

lines

Narrow

angle

Inclined

line

Cone

Wide

angle

Cylinder

a.Point:Itisanon-dimensionalgeometricalelement.

Itisoccurredbyinterceptionofvariouslines.

b.Line:Itisa1Dgeometricalelementoccurredbymovingofapointin

variousdirection.Thepicturebelowillustrateslines,drawninvarious

directions,andother geometrical elements occurred by these

lines.

Parallel

lines

HorizontalVertical

NarrowWide

angleangle

VerticalIntercept

lines

Zigzag

Curved

line

lineVerticallines

lineCurved

line

c.Plane: Aplaneisoccurredbyatleastthreepoints

orconnectionofonepointandoneline.Aplaneisalways2D.When

thenumberofelementformingaplaneincreases,shapeandname

oftheplanewillchange.

Theconnectionofthreepointsatcertainconditionsformtriangle.

Theconnectionoffourpointsatcertainconditionsformsquare.

Theconnectionofinfinitepointsatcertainconditionsformcircle.

TriangleSquareCircle

Infinitepoint

3.1-Geometricaldrawings

relatedwithlines

3.1.1-Drawingofparallellines

3.1.1.1-Drawingparallellinewith

compasses

a.Drawingparallellinetoalinefrom

anyPpoint(outsidefromtheline):

I.Way:

1. AcceptpointPascenter.Openthe

compasswitharcR,interceptABline

andobtainpointC.

2. AcceptpointCascenter,don’t

movethecompass.Drawanother

arcthatcrosspointPandintercept

ABline,obtainpointD.

3. OpenthecompassasPDarc.Put

the compass to point C and

interceptarcb,findpointE.

4. ConnectthepointPwithpointE.

PabE

II.Way:

1. Drawanylinecrossing

pointP,interceptingline

AB.

2. AcceptpointCascenter.Openthe

compassasCP,drawanarc,obtain

pointD.

3. AcceptpointPandDascenter,

respectivelyandfindpointEwith

interceptedarcs.

4. ConnectpointPandE.

b.Drawingaparallellinetoalinewithaknown

distance,“a”.

1. Openthecompassas“a”.

2. MarkanyCandDpointsonAB

line.

3. DrawtwoarcsbyacceptingCand

Dpointsascenter,respectively.

4. DrawEFtangenttothesearcs.

CDB

3.1.2-Drawingofverticallines

a-Drawingofvertical

lineswithcompass:

Todrawverticallinefrom

thepointonaline:

DPG

1. AcceptPpointascenter.

DrawDandGpointonline

AB.

2. ByacceptingDandGpointsas

center,respectively,drawtwoarcs

thatareinterceptedoutsidefromAB

lineandformF

3. ConnectpointDandF.

b.Drawingaverticallineattheendofaline:

I.way:

1. AcceptpointPascenter.

DrawarcRandmark

pointB.

2. Don’tmovecompassangle,accept

pointBascenter,drawanarc

crossingpointPandpreviousarc.

ObtainpointC.

3. ConnectpointBandCandprolong

thisnewline.

4. AcceptpointCascenter,drawan

arcinterceptingBCline.Markpoint

Dattheintersectionpoint.

5. ConnectpointPandD. B

II.Way:

1. AcceptpointPascenter.Open

thecompassasRamountand

markpointB.

2. Don’tmovethecompass;accepting

B,CandDascenter,respectively;

drawthearcsintersectingeach

other.ObtainpointE.

3. ConnectpointPandE.

c.Drawingaverticallinetoalinefromanoutside

location

1. AcceptpointPascenter.

Drawanarccrossingline

AB.MarkpointsCandD.

2. AcceptpointCandDascenter,

respectively. Draw two arcs

interceptingeachother.Markpoint

3. ConnectpointEandP.

3.1.3-Dividethelinestoequalpieces:

Dividingalinetotwo,four

andeightequalpieces:

1. Openthecompassaslittlemore

thanhalfoftheline.

AC=CB

2. AcceptpointAandBascenter,

respectively.Drawintersectingtwo

arcs.

3. Connecttheinterceptingpointand

obtainpointC.Inthisway,youcan

dividethelineABtotwoequal

4. RepeatthesameprocedureforAC

line.ObtainpointD.

AD=DC

5. RepeatthesameprocedureforAD

line,obtainpointE.

AE=E

3.2-GEOMETRICALDRAWINGS

RELATEDWITHANGLES

3.2.1-Typesof

angles:

Verticalangle

Accordingtothesituation

oflinescrossingeach

other,threetypesof

anglesoccur.These

anglesareseenatthe

sidepictures.

Armsoftheangle

Wideangle

3.2.2-Drawingoftriangles

3.2.2.1-Equilateraltriangle

a.Drawingofequilateraltriangle-onesidegiven.(with

compass):

1. AB side is known. Open the

compassasAB.Drawtwoarcsby

consideringAandBascenter,

respectively.ObtainpointC.

2. ConnectpointCwithAandB.

b. Drawingofequilateraltriangleinacircle(or,

divingacircletothreeequalpieces):

1. Openthecompassasradius(R)of

thecircle.

2. Accepttheintersectingpointofthe

circlewithlateralorverticalaxisof

thecircleascenter.Drawanarc,

crossingthecircleattwopoints..

3. ThelengthbetweenAandBpoints,

obtainedfrompreviousstep,isthe

beamlength.

4. PointC,whichistheoppositeofthe

center,isconnectedwithAandB

points.

3.2.2.2-Perpendiculartriangle

a.Drawingofaperpendiculartriangleofwhichtwo

perpendicularsidesaregiven:

1. DrawsideAB.

2. DrawaverticallineatpointA.

3. MarkACsidewiththehelpof

compassatthisverticalline.Obtain

pointC.

4. ConnectpointCwithpointB.

b. Drawingaperpendiculartriangleina

circle.

1. DrawacirclewithradiusR..

2. Markanypointonthecircle,asA.

3. ConnectthepointAwithpointsBand

C,whicharethecrossingofcirclewith

radius..

4-DRAWINGHANDOUTSINDEX

Projection

Orthographicormultiviewdrawings

Pictorialdrawings

Isometric

Oblique

Perspective

Dimensioning

Sectioning

4.1.Projection

Thegoalinengineeringgraphics,whetheritisfreehandsketchingorCAD,

istorepresentaphysicalobject.Objectscanbeshownas3-Dprojectionsor

Multiviewprojections.3-Dprojectionsareusefulinthattheyprovidean

imagethatissimilartotheimageinthedesigner’smind’seye.But3-D

projectionsareoftenweakinprovidingadequatedetailsoftheobject,and

thereisoftensomedistortionoftheobject.Forinstance,acircularhole

becomesanellipseinanisometric3-Dprojection.Multiviewprojectionsare

usedtoovercometheweaknessesof3-Dprojections.Multiviewprojections

areacollectionofflat2-Ddrawingsofthedifferentsidesofanobject

Projectionistherepresentationofafigureorsolidonaplaneasit

wouldlookfromaparticulardirection,

Twodefinitionareusedinprojection:

Orthographicprojection

Pictorialprojection

4.1.1.Orthographicormultiview

projection

Orthographicprojectionisamethodofproducinganumberofseparate2Dinter-relatedviews,which

aremutuallyatrightanglestoeachother.Usingthisprojection,eventhemostcomplex

shapecanbefullydescribed.Thismethod,however,doesnotcreateanimmediatethree-dimensional

visualpictureoftheobject,asdoespictorialprojection.Orthographicprojectionisbasedon

twoprincipalplanes—onehorizontal(HP)andonevertical(VP)—intersectingeachotherandforming

rightanglesandquadrantsasshowninFigure3.1.

4.1.1.Orthographicormultiviewprojection

Imaginethatyouhaveanobjectsuspendedbytransparentthreads

insideaglassbox,asinfigure4.

Drawtheobjectoneachofthreefacesasseenfromthat

direction.Unfoldthebox(figure5)andyouhavethethree

views.Wecallthisan"orthographic"or"multiview"

drawing.

Figure6showshowthethreeviewsappearonapieceof

paperafterunfoldingthebox.

Question:Whichviewsshouldonechooseforamultiviewdrawing?

Answer:Theviewsthatrevealeverydetailabouttheobject.

Threeviewsarenotalwaysnecessary;weneedonlyasmanyviewsasarerequiredto

describetheobjectfully.Forexample,someobjectsneedonlytwoviews,whileothers

needfour.Thecircularobjectinfigure7requiresonlytwoviews.

4.1.2PictorialDrawings

Showsanobjectlikeyouwouldseeina

photograph

Giveathreedimensionalviewofaroomor

structure

Threecommontypes

Isometric

Oblique

Perspective

PictorialSketchofKitchen

a-IsometricDrawing

Therepresentationofthemachinedblock(figure1)asanobjectin

figure2iscalledanisometricdrawing.

Inanisometricdrawing,theobject'sverticallinesaredrawn

vertically,andthehorizontallinesinthewidthanddepthplanesare

shownat30degreestothehorizontal.Whendrawnunderthese

guidelines,thelinesparalleltothesethreeaxesareattheirtrue

(scale)lengths.Linesthatarenotparalleltotheseaxeswillnotbe

oftheirtruelength.

IsometricofaCube

Anyengineeringdrawingshouldshoweverything:

acompleteunderstandingoftheobjectshouldbe

possiblefromthedrawing.Iftheisometricdrawing

canshowalldetailsandalldimensionsonone

drawing,itisideal.

However,iftheobjectinfigure2hadaholeonthe

backside,itwouldnotbevisibleusingasingle

isometricdrawing.Inordertogetamorecomplete

viewoftheobject,anorthographicprojectionmay

beused.

b-ObliqueDrawings

Thefrontviewisdrawnlikeitwouldbeusingorthographic

projection

Thefrontviewshowsallfeatureswithtrueshapeandsize

Thetopandsideviewarethenprojectedbackfromthe

frontview

Viewscanbeatanyangle

15,30or45degreesarecommon

Twotypesofobliquedrawings

cavalier

cabinet

Usefulwhenthefrontcontainsmoredetailsandfeatures

thanthesideview

Amentalimagecanbecreatedmorequicklythanwith

orthographicalone

CavalierOblique

Theentiredrawingusesthesamescale

Sometimescreatesadistortedappearance

CabinetOblique

Measurementsontherecedingaxesarereducedbyhalf

Morevisuallyrealisticrepresentation

Oftenusedfordrawingcabinets

c-PerspectiveDrawings

Themostrealisticofall

pictorialdrawings

Recedinglinesinthe

drawing“meet”ata

vanishingpointinsteadof

beingparallel

Eliminatesdistortionatthe

backpartofpictorial

drawings

Twotypes

parallel(one-point)

perspective

angular(twopoint)

perspective

ParallelPerspective(OnePoint)

Onefaceoftheobjectisshownasthefrontview

Linesparalleltothefrontviewremainparallel

Linesthatareperpendiculartothefrontviewconvergeat

aSINGLEVANISHINGPOINT

AngularPerspective(Two-Point)

Similartoisometricdrawings

Oneedgeoftheobjectisplaceinfront

Thetwofacesthatmeetatthisedgerecedeto

DIFFERENTVANISHINGPOINTS

Alllinesparalleltoeachfacegotothedifferentvanishing

points

AngularPerspectiveDrawing

4.2.Dimensioning

Wehave"dimensioned"theobjectintheisometricdrawinginfigure8.Asageneral

guidelinetodimensioning,trytothinkthatyouwouldmakeanobjectanddimensionit

inthemostusefulway.Putinexactlyasmanydimensionsasarenecessaryforthe

craftspersontomakeit-nomore,noless.Donotputinredundantdimensions.

4.3.Sectioning

Therearemanytimeswhentheinteriordetailsofanobjectcannotbeseen

fromtheoutside(figure9).

Wecangetaroundthisbypretendingtocuttheobjectonaplaneand

showingthe"sectionalview".Thesectionalviewisapplicabletoobjectslike

engineblocks,wheretheinteriordetailsareintricateandwouldbevery

difficulttounderstandthroughtheuseof"hidden"lines(hiddenlinesare,by

convention,dotted)onanorthographicorisometricdrawing.

Imagineslicingtheobjectinthemiddle

REFERENCES

BağcıM.BağcıC.,“TeknikResimI-II”,1982.

MITOpenCourseWare:

http://www.ocw.mit.edu/NR/rdonlyres/Mechanical-Engineering/2-

007Spring-2005/929103E2-EBAD-40DE-88BF-

E2258E0FEC49/0/drawings.pdf-2006-11-09

http://www.mkn.itu.edu.tr/~mkimrak/MAK112E_dersnotu.htm

www.tech.plymouth.ac.uk/dmme/dsgn131/DSGN131_Course_Notes.pdf