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.

A

A

·Samelineshapesand

thicknessesareusedinthis

drawing.Thereforeitisvery

difficulttohaveanideaof

theshapesanddimensions

ofthepiece.

A-A

AA

·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.

D

Dashline(thin)*

E1-Axislinesofsymmetricaldrawing

E

Dashlinewithpoint(thin)E2-Infrontofsectionplanes

F

Sectionplanewiththickendsand

F1-Todrawthetracesatsectionplane

thinmidpoints.

G-Tostatetheplacewhichwillprocessed

G

H

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.Theyshouldbe3∼6mm,or0,8~1,5mm

accordingtothesizeofthepicture.

D1

d-Dashlineswithpointshouldbedrawnaccordingtothesizeofthe

picturewithbelowmentionedsizes.

E1

7....15111

H1

G1

10

11111

10

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,andothergeometricalelementsoccurredbythese

lines.

Parallel

lines

HorizontalVertical

NarrowWide

angleangle

VerticalIntercept

lines

Zigzag

Curved

line

line

lineVerticallines

lineCurved

line

c.Plane:Aplaneisoccurredbyatleastthreepoints

orconnectionofonepointandoneline.Aplaneisalways2D.When

thenumberofelementformingaplaneincreases,shapeandname

oftheplanewillchange.

Theconnectionofthreepointsatcertainconditionsformtriangle.

Theconnectionoffourpointsatcertainconditionsformsquare.

Theconnectionofinfinitepointsatcertainconditionsformcircle.

A

A

D

A

B

TriangleSquareCircle

C

BC

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.

P

AB

2.AcceptpointCascenter,don’t

movethecompass.Drawanother

arcthatcrosspointPandintercept

ABline,obtainpointD.

3.OpenthecompassasPDarc.Put

thecompasstopointCand

interceptarcb,findpointE.

4.ConnectthepointPwithpointE.

PabE

R

r

R

AB

DC

II.Way:

1.Drawanylinecrossing

pointP,interceptingline

AB.

2.AcceptpointCascenter.Openthe

compassasCP,drawanarc,obtain

pointD.

3.AcceptpointPandDascenter,

respectivelyandfindpointEwith

interceptedarcs.

4.ConnectpointPandE.

P

AB

PE

A

C

D

B

b.Drawingaparallellinetoalinewithaknown

distance,“a”.

1.Openthecompassas“a”.

2.MarkanyCandDpointsonAB

line.

3.DrawtwoarcsbyacceptingCand

Dpointsascenter,respectively.

AB

a

EF

4.DrawEFtangenttothesearcs.

A

aa

CDB

3.1.2-Drawingofverticallines

a-Drawingofvertical

lineswithcompass:

Todrawverticallinefrom

thepointonaline:

A

DPG

B

1.AcceptPpointascenter.

DrawDandGpointonline

AB.

2.ByacceptingDandGpointsas

center,respectively,drawtwoarcs

thatareinterceptedoutsidefromAB

lineandformF

3.ConnectpointDandF.

F

b.Drawingaverticallineattheendofaline:

I.way:

1.AcceptpointPascenter.

DrawarcRandmark

pointB.

P

2.Don’tmovecompassangle,accept

pointBascenter,drawanarc

crossingpointPandpreviousarc.

ObtainpointC.

3.ConnectpointBandCandprolong

thisnewline.

4.AcceptpointCascenter,drawan

arcinterceptingBCline.Markpoint

Dattheintersectionpoint.

5.ConnectpointPandD.B

R

C

R

D

R

P

II.Way:

E

1.AcceptpointPascenter.Open

thecompassasRamountand

markpointB.

C

R

D

R

2.Don’tmovethecompass;accepting

B,CandDascenter,respectively;

drawthearcsintersectingeach

A

B

P

other.ObtainpointE.

3.ConnectpointPandE.

C

E

D

A

B

P

c.Drawingaverticallinetoalinefromanoutside

location

1.AcceptpointPascenter.

Drawanarccrossingline

AB.MarkpointsCandD.

P

2.AcceptpointCandDascenter,

respectively.Drawtwoarcs

interceptingeachother.Markpoint

E.

3.ConnectpointEandP.

A

C

D

B

E

3.1.3-Dividethelinestoequalpieces:

Dividingalinetotwo,four

andeightequalpieces:

1.Openthecompassaslittlemore

thanhalfoftheline.

A

C

AC=CB

B

2.AcceptpointAandBascenter,

respectively.Drawintersectingtwo

arcs.

3.Connecttheinterceptingpointand

obtainpointC.Inthisway,youcan

dividethelineABtotwoequal

4.RepeatthesameprocedureforAC

line.ObtainpointD.

A

D

C

AD=DC

B

5.RepeatthesameprocedureforAD

line,obtainpointE.

A

EC

AE=E

D

B

3.2-GEOMETRICALDRAWINGS

RELATEDWITHANGLES

3.2.1-Typesof

angles:

A

Verticalangle

Accordingtothesituation

oflinescrossingeach

other,threetypesof

anglesoccur.These

0

BC

anglesareseenatthe

sidepictures.

A

2

ı

B

A

Armsoftheangle

2

BC

Wideangle

3.2.2-Drawingoftriangles

3.2.2.1-Equilateraltriangle

a.Drawingofequilateraltriangle-onesidegiven.(with

compass):

C

1.ABsideisknown.Openthe

compassasAB.Drawtwoarcsby

R

R

consideringAandBascenter,

respectively.ObtainpointC.

A

I

B

C

2.ConnectpointCwithAandB.

A

II

B

b.Drawingofequilateraltriangleinacircle(or,

divingacircletothreeequalpieces):

1.Openthecompassasradius(R)of

thecircle.

2.Accepttheintersectingpointofthe

circlewithlateralorverticalaxisof

thecircleascenter.Drawanarc,

C

R

crossingthecircleattwopoints..

R

3.ThelengthbetweenAandBpoints,

obtainedfrompreviousstep,isthe

beamlength.

4.PointC,whichistheoppositeofthe

center,isconnectedwithAandB

points.

A

B

3.2.2.2-Perpendiculartriangle

a.Drawingofaperpendiculartriangleofwhichtwo

perpendicularsidesaregiven:

1.DrawsideAB.

2.DrawaverticallineatpointA.

3.MarkACsidewiththehelpof

compassatthisverticalline.Obtain

pointC.

4.ConnectpointCwithpointB.

A

A

A

C

C

B

B

b.Drawingaperpendiculartriangleina

circle.

1.DrawacirclewithradiusR..

A

2.Markanypointonthecircle,asA.

3.ConnectthepointAwithpointsBand

C,whicharethecrossingofcirclewith

radius..

CB

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:

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

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

DSGN131_Course_Notes.pdf