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 / ApplicationplacesA / 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