SECTIONALSECTIONAL

ORTHOGRAPHIC

PROJECTIONSPROJECTIONS

Why sectional Orthographic projections are used?

I. To understand inner details of complex object:When the object is complex from inside thereWhen the object is complex from inside, therewill be many hidden lines in the projections and it will be difficult to understand the orthographicwill be difficult to understand the orthographicprojections. Therefore, to understand the details of the complex object sectionaldetails of the complex object, sectional orthographic Projections are used.

II To understand the materials of object :II. To understand the materials of object : If object is made of two or more materials, then it can be understood clearly by sectionalcan be understood clearly by sectional orthographic projections.

Orthographic projections of complexOrthographic projections of complex

objects are drawn after imagining it as an

object cut by an imaginary cutting plane/planes

parallel to principal planes passing through the

details of the objectdetails of the object.

An imaginary plane by which the object is cut

is known as cutting plane or section plane.

P ti f th bj t b t tti lPortion of the object between cutting plane

and observer is imagined to be removed and g

then the object is viewed by the observer and

projection is drawn.

P j ti f t bj t i kProjection of cut object is known as

sectional view or sectional projection.p j

Generally hidden lines are not drawn in

sectional view.

In sectional views, the Shape of the section,

visible edges and contours of object behindvisible edges and contours of object behind

the section plane are drawn.

When one view is drawn sectional, other views

are drawn as if the object is not cut and the

object exists as a wholeobject exists as a whole.

It means other views are not affected by

taking section in one view, but Cutting plane

line is shown in non sectioned view to locate theline is shown in non sectioned view to locate the

section plane and arrows are drawn to show the

direction of sight.

Cutting plane line

Cutting plane line is also known as line of

section or trace of the cutting plane.

The portion of the object cut by cutting plane and

touching the cutting plane is shown by

drawing hatching or section lines in them.

Hatching or section lines are drawn thinner thanHatching or section lines are drawn thinner than

object lines.

Normally hatching or section lines are drawn

at 45˚.

Hatching lines are evenly spaced at aboutHatching lines are evenly spaced at about

2 to 3 mm apart.

H t hiobserver

Cutting plane or section planeParallel to H.P

Hatching

Parallel to H.P.

Sectional T VSectional T.V.

X

Portion between observer and plane (Upper half portion)

i i i d t b d

F.V.

is imagined to be removed.

Sectioned portion will be as shown in fig.

BackTrue shape of sectioned portion will be

seen in T.V

Various cutting planes or section planes

Cutting plane Parallel to Principal vertical

plane.

C tti l P ll l t P i i l h i t lCutting plane Parallel to Principal horizontal

plane.plane.

Cutting plane Parallel to profile plane.

Cutting plane Parallel to Principal vertical planeCutting plane Parallel to Principal vertical plane

Wh bj t i t b l ll l tWhen an object is cut by a plane parallel to

Principal vertical plane then:p p

The real or true shape of the section is observed

in F.V.

Section plane ill be seen as a c tting plane lineSection plane will be seen as a cutting plane line

in T.V.

Cutting plane line

T.V.

Sectional F.V.

Object

observerback

Sectioned object

Vertical cuttingplane

Sectional F.V.

ObserverT.V.

observer

Sectioned object

observerBack

C tti l P ll l t P i i l h i t l lCutting plane Parallel to Principal horizontal plane

When an object is cut by a plane parallel to Principal j y p p p

horizontal plane then:

The real or true shape of the section is observed

i T Vin T.V.

Section plane will be seen as a cutting plane linep g p

in F.V.

observer Cutting planeline

Horizontal cuttingplane

F.V.F.V.

Sectional T.V.

Sectioned object

C tti l P ll l t fil lCutting plane Parallel to profile plane

When an object is cut by a plane parallel to profilej y p p p

plane then:

The real or true shape of the section is observed

i id iin side view.

Section plane will be seen as a cutting plane linep g p

in T.V.

A

A Sectioned object

X

Cutting plane line

Sectional R.H.S.V F.V.

A

T.V.X ASectioned object

Sectioning rule for machine elements like :Sectioning rule for machine elements like :

Ribs rivets webs shafts pins nuts boltsRibs, rivets, webs, shafts, pins, nuts, bolts, washers, keys and cotter.

Whenever, the cutting plane is passing through

above machine elements and if cutting plane

contains the axis of above machine elements,

then they are not sectioned.then they are not sectioned.

However, when the cutting plane is cutting,

Elements perpendicular to the axis of the

Above Machine elements, section is taken

and in the projection hatching lines are drawn.

If tti l d t i l d i thIf cutting plane does not include axis then

These elements are hatchedThese elements are hatched.

Sectioning of Rivets

CORRECT WRONG

30 DEEP

F.V.

X

T.V.T.V.

30 DEEP

Sectional F.V.X

T.V.

F.V.

AC

R=MOTC

C CM

OR

CM

P

A

F.V.

XA

Sectional T.V.

O

R=MO

C CM

O

R

Rib MRib

F.V.Sectional L.H.S.V.A

C

C

XA

RULES OF HATCHING:

1) A f t l t i l t b ti1) Area of a metal or a material, cut by a section

plane is shown by hatching lines in projection.plane is shown by hatching lines in projection.

It is executed by thin lines normally at an angle of

45˚ to the axis or to the main outlines of the

ti lsectional area.

(2) If the axis of the boundary of section is at 45˚then(2) If the axis of the boundary of section is at 45 then the vertical or horizontal hatching lines are drawn.

Axis at 45˚

Axis at 45˚

(3) Separate area of a section of a single(3) Separate area of a section of a single component are hatched in the same mannermanner. CLICK FOR EXAMPLE

(4) Hatching lines on a second part, adjacent to the first are at an angle of 45˚adjacent to the first are at an angle of 45 but in the opposite direction. Hatching li thi d t dj t t fi t tlines on a third part adjacent to first two are drawn at an angle of 30˚ or 60˚. Sometimes spacing or pitch of the hatching lines is varied to separate it from g pthe adjacent parts.

Hatching more than two adjacent components g j p

C

hatched45˚at 60˚B

45

A hatched

(2) D45˚at 30˚on D(2) D45 on D

(5) If hatching is required on a large section(5) If hatching is required on a large section

area, it is avoided. It is limited to a zone

following the contour of the sectioned area

required to be hatched.

Large area

(6) If hatching is required on a very thin section(6) If hatching is required on a very thin section

area, it is avoided. Complete section is shown

entirely black. Thin space is left between

adjacent section of the same type.

(7) As far as possible avoid dimensioning inside ( ) p g

hatched area, but, if not possible, hatching

lines may be interrupted for the dimensioning.

(8) Hatched area can never have dashed or

dotted boundary.dotted boundary.

Figure shows isometric view of agmachine component. Draw its

(1)Front view, Top view & L.H.S

15

(1)Front view, Top view & L.H.SView, using 3rd angle methodof projections.

50

(2) Sectional Front view, Topview & L.H.S.V., using 3rd

5, gangle method of projections.

15

10

604030525

30

12

5

50 50

Top View

50

15

Front ViewL.H.S.View

B

It will be nearer to V.P.

R i d li f h

It will be nearer to V.P.in 1st angle method &against the vertical

A

Retained split of the machine parts

plane in 3rd anglemethod.

10

30

604030

1525

30

5A

50 50

Top View

AA

Sectional Front View -ABL.H.S. ViewB

Figure shows the pictorialview of a machine component.D i f ll i i

AADraw its following views asper First angle method ofprojections

6060

projections(1) Front view from X direction.(2) Sectional top view-AA

00AA

(2) Sectional top view-AA(3) L.H.S. View

2020002020

XXXX

Sketch shows the assumed cut model (retained part ofthe machine component / split against the observer) dueto horizontal section plane passing through AB.

002020

XXXX

Ø30, 7deep Ø20Ø20

00AA6060

2020

AAAA

AA AA66

2020

120120F.V.F.V.

L.H.S.V.L.H.S.V.

28281414 AA

Sectional T.V.Sectional T.V.--AAAA

XX

φφ3030B

Figure shows the pictorial viewof a machine components.Draw its following views,using 3rd angle method ofprojectionsprojections.

(1) Front view from arrow X

6060

(2) Top View

(3) Sectional R H S V - AB(3) Sectional R.H.S.V - AB202022

XXA

Retained split, will benearer to VP in 1st

Bnearer to V.P. in 1st

angle method &against the verticalgplane in 3rd anglemethod.

No hatching inthis area as notcontained in thecontained in thesection plane

R i d li f h

A

Retained split of the machine parts

AAB

B

B

6060

9090

A

2020 2020

99

4040T V

XXA

44

AAT.V.

8080

S C

2020

AAF.V.

Full SEC.R.H.S.V

PROBLEM

Sketch, shows isometric view of a machine part.Draw itsDraw its (1) Full Sectional F.V. (sectional F.V.)

(2) T.V.

(3) R.H.S.V.U thi d l th d f th hiUse third angle method of orthographicprojection. Dimension the view as per thep j palign system.

R30AGiven Given

IsometricIsometric R30Isometric Isometric viewview

R20

BL=100, D=100 & H= 100L=100, D=100 & H= 100

AR20

BBAA

30AA

TOP VIEWTOP VIEW60

B

12

60

45

100 12

R.H.S. VIEWR.H.S. VIEW

100BB

SEC. FRONT VIEWSEC. FRONT VIEW

PROBLEM - 1

The following figure shows theisometric view of a machine componentisometric view of a machine componentDraw its1)F ll ti l F t i1)Full sectional Front view (sectional F.V.)2)Top view3)L.H.S view

Use First angle method of projections anddi i i i li d t ldimensioning using aligned system only

R 25R 25

Φ 25 ,10 deep

R 2510 Ø251055

25 60°10 10

20 60SECTIONAL FRONT VIEW -AB

L.H.S. VIEW -AB

Φ 2510

70

Φ 25

45

45

10

12.5

TOP VIEW

R 2510 Ø2510

55

25 6010 101

FRONT VIEW L.H.S. VIEW

20 60

70

Φ 25

45

45

10

12.5

TOP VIEW

AimAim::--SketchSketch--11,, showsshows IsometricIsometric ViewView ofof aamachinemachine partpart.. DrawDraw itsits followingfollowingorthographicorthographic viewsviews usingusing thirdthird angleangle

SOLUTION`SOLUTION`

g pg p gg ggmethodmethod ofof projections,projections, givinggiving dimensionsdimensions..(1) Sectional F.V.(1) Sectional F.V.--AAAA(2) T V(2) T V(2) T.V.(2) T.V.(3) L.H.S.V(3) L.H.S.V

AA TOP VIEWTOP VIEWR35R35

AAAA3030

AA

88

AATOP VIEWTOP VIEW

Ö20Ö20

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002 HOLES,Ö 142 HOLES,Ö 14

6565

4`4`

100

100

AA

1414

AA AALEFT HAND SIDE VIEWLEFT HAND SIDE VIEW SECTIONAL FRONT VIEW AASECTIONAL FRONT VIEW AA

XX

SCALE:SCALE:-- 1:11:1SYMBOL OF PROJECTION METHOD, NOT SHOWNSYMBOL OF PROJECTION METHOD, NOT SHOWN

SketchSketch--11

SOLUTION`SOLUTION`Aim:Aim:--SketchSketch--1, shows Isometric View of a 1, shows Isometric View of a machine part. Draw its following machine part. Draw its following

th hi i i thi d lth hi i i thi d lorthographic views using third angle orthographic views using third angle method of projections, giving dimensions.method of projections, giving dimensions.(1) Sectional F.V.(1) Sectional F.V.--AAAA(2) T.V.(2) T.V.

SCALE:SCALE:-- 1:11:1

AAAA

R35R35

( )( )(3) L.H.S.V(3) L.H.S.V

3030

AATOP VIEWTOP VIEW

SCALE:SCALE: 1:11:1

88Φ20Φ20

R35R35AA

1414

88

Φ20Φ20Φ36Φ36Φ36Φ36

100

1002 HOLES,Ö 142 HOLES,Ö 14

AALEFT HAND SIDE VIEWLEFT HAND SIDE VIEW SECTIONAL FRONT VIEW AASECTIONAL FRONT VIEW AA

SYMBOL OF PROJECTION METHOD, NOT SHOWNSYMBOL OF PROJECTION METHOD, NOT SHOWN

XXAA

Types of sectional view

(1) Full sectional View ( )

(2) Half sectional View .

(1) Full section:

The sectional view obtained after removing oneThe sectional view obtained after removing one

half portion of the object through its centre line p j g

by an imaginary cutting plane is known as full

sectional view.

If it happens to be elevation (front view),If it happens to be elevation (front view),

it is known as Full sectional elevation or

Full sectional front view. Normally the word

‘f ll’ i itt d‘full’ is omitted.

If it happens to be plan (top view), it is knownIf it happens to be plan (top view), it is known

as full Sectional plan or full sectional top view.

Similarly there can be full sectional side view.

N ll th d ‘f ll’ i itt dNormally the word ‘full’ is omitted.

Important points:

hidden lines should not be drawn in sectional viewview

Visible lines behind the cutting plane should beVisible lines behind the cutting plane should beshown.

The portions which are actually cut by cutting l h ld b h t h dplane should be hatched.

The position of the cutting plane should be shown by using cutting plane line.

SPECIALSECTIONSSECTIONS

HALF SECTIONHALF SECTION

HALF SECTIONAL F.V.-AB HALF SECTIONALLEFT S V BCLEFT S.V.-BC

BB

A

CTOP VIEW

(2) Half sectional view:(2) Half sectional view:

When the object is symmetrical about its centrej y

line, from outside as well as from inside, half

sectional view is preferred.

The main usefulness of the half section is in

assembly drawing where it is often required toassembly drawing where it is often required to

show both internal and external construction of

the object on the same view.

i) Half sectional front view :

The sectional view obtained after removing

th f t t ti f th bj t b tthe front quarter portion of the object by two

imaginary cutting planes at right angles to g y g p g g

each other is known as half sectional

elevation or half sectional front view.

The half sectional front view may be left or

right depending upon the left or right frontright depending upon the left or right front

quarter portion of the object is removed.

ii) Half sectional top view:

sectional top view. The sectional view

bt i d ft i th t t tiobtained after removing the top quarter portion

of the object by two imaginary cutting planes atof the object by two imaginary cutting planes at

right angles to each other is known as half

sectional plan or half

Th h lf ti l t i b l ft i htThe half sectional top view may be left or right

depending upon the left or right top quarterdepending upon the left or right top quarter

portion of the object is removed.

Similarly there can be half sectional side view.

OFFSETOFFSET S C OSECTION

OFFSET SECTION: The path of the cutting planeis bent to pass through features not located in ais bent to pass through features not located in astraight line, i.e. it is offset to pass through bothprinciple features of the object Example is shownprinciple features of the object. Example is shownbelow.

Section lines are to be staggered Rto be staggered as shown at R

R

B

B

SPECIAL SECTIONSSPECIAL SECTIONS

REMOVED &REVOLVED SECTIONS

REVOLVEDSECTIONSECTION

REMOVED SECTION

REVOLVED REVOLVEDREVOLVEDSECTION

REVOLVEDSECTION

REMOVEDSECTION

REVOLVED SECTION

REMOVED SECTION

REMOVED SECTIONS

Partial (broken localPartial (broken, local or Zonal) Sectionor Zonal) Section.

Partial (broken, local or Zonal) Section.

This is used to show only a desired features of thebj t N tti l li dobject . No cutting plane lines are necessary, and

it shown by wavy line

Tap- bolt fastenerPartial (broken, local or Zonal)

pulleylocal or Zonal)

Section.

shaft

Shaft and pulley partly broken out to show internal fasteningg

SPECIAL SECTION

Cross hatching of adjacent parts

Part 1

Part 2Part 3

SPECIAL SECTION

Hatching more than two adjacent components at (2)

Part C

P B(hatched45Part B(at 60 )

45

Part A hatched

Part D45

at 30on DPart D45 o

A B

F.V.

SEC.T.V.Two vertical plates ,fastened by a horizontalrivet is shown in its F.V. & T.V., cut by horizontalsection plane. Note: the rivet is shown in section inT.V.

AimAim::--SketchSketch--11,, showsshows IsometricIsometric ViewView ofof aamachinemachine partpart.. DrawDraw itsits followingfollowingorthographicorthographic viewsviews usingusing thirdthird angleangle

SOLUTION`SOLUTION`

g pg p gg ggmethodmethod ofof projections,projections, givinggiving dimensionsdimensions..(1) Sectional F.V.(1) Sectional F.V.--AAAA(2) T V(2) T V(2) T.V.(2) T.V.(3) L.H.S.V(3) L.H.S.V

AA TOP VIEWTOP VIEWR35R35

AAAA3030

AA

88

AATOP VIEWTOP VIEW

Ö20Ö20

Φ20Φ20Φ36Φ36

ÖÖ

Ö36Ö36

002 HOLES,Ö 142 HOLES,Ö 14

6565

4`4`

100

100

AA

1414

AA AALEFT HAND SIDE VIEWLEFT HAND SIDE VIEW SECTIONAL FRONT VIEW AASECTIONAL FRONT VIEW AA

XX

SCALE:SCALE:-- 1:11:1SYMBOL OF PROJECTION METHOD, NOT SHOWNSYMBOL OF PROJECTION METHOD, NOT SHOWN

SketchSketch--11

SOLUTION`SOLUTION`Aim:Aim:--SketchSketch--1, shows Isometric View of a 1, shows Isometric View of a machine part. Draw its following machine part. Draw its following

th hi i i thi d lth hi i i thi d lorthographic views using third angle orthographic views using third angle method of projections, giving dimensions.method of projections, giving dimensions.(1) Sectional F.V.(1) Sectional F.V.--AAAA(2) T.V.(2) T.V.

SCALE:SCALE:-- 1:11:1

AAAA

R35R35

( )( )(3) L.H.S.V(3) L.H.S.V

3030

AATOP VIEWTOP VIEW

SCALE:SCALE: 1:11:1

88Φ20Φ20

R35R35AA

1414

88

Φ20Φ20Φ36Φ36Φ36Φ36

100

1002 HOLES,Ö 142 HOLES,Ö 14

AALEFT HAND SIDE VIEWLEFT HAND SIDE VIEW SECTIONAL FRONT VIEW AASECTIONAL FRONT VIEW AA

SYMBOL OF PROJECTION METHOD, NOT SHOWNSYMBOL OF PROJECTION METHOD, NOT SHOWN

XXAA

AA

AAAA

XX

B

XX

A

BB

A

AimAim::--SketchSketch--11,, showsshows IsometricIsometric ViewView ofof aamachinemachine partpart.. DrawDraw itsits followingfollowingorthographicorthographic viewsviews usingusing thirdthird angleangle

SOLUTION`SOLUTION`

g pg p gg ggmethodmethod ofof projections,projections, givinggiving dimensionsdimensions..(1) Sectional F.V.(1) Sectional F.V.--AAAA(2) T V(2) T V(2) T.V.(2) T.V.(3) L.H.S.V(3) L.H.S.V

AA TOP VIEWTOP VIEWR35R35

AAAA3030

AA

88

AATOP VIEWTOP VIEW

Ö20Ö20

Φ20Φ20Φ36Φ36

ÖÖ

Ö36Ö36

002 HOLES,Ö 142 HOLES,Ö 14

6565

4`4`

100

100

AA

1414

AA AALEFT HAND SIDE VIEWLEFT HAND SIDE VIEW SECTIONAL FRONT VIEW AASECTIONAL FRONT VIEW AA

XX

SCALE:SCALE:-- 1:11:1SYMBOL OF PROJECTION METHOD, NOT SHOWNSYMBOL OF PROJECTION METHOD, NOT SHOWN

SketchSketch--11