This document discusses various drawing instruments and materials used to create technical drawings. It describes: 1) Common drawing tools like drawing boards, T-squares, set squares, protractors, and their uses. 2) Recommended sizes for drawing boards, sheets, and other materials. 3) How each tool is constructed and used to draw straight lines, angles, and curves accurately.

1. Chapter- 1A
DRAWINGINSTRUMENTS
ANDTHEIR USES
DrawingInstrumentsare usedtoprepare neatand accurate Drawings.Toa greaterextent,the accuracy
of the Drawingsdependonthe qualityof instrumentsusedtoprepare them.The followingisthe list
of DrawingInstrumentsandothermaterialsrequired.
a) DrawingBoard
b) T-square or Drafter (Draftingmachine)
c) SetSquares
d) Protractor
e) DrawingInstrumentBox
f) DrawingSheet
g) DrawingPencils
h) DrawingPins/Clips
a) DrawingBoard:
Drawingboard ismade fromstripsof well seasonedsoftwoodgenerally25mm thick.Itis cleated
at the backby two battenstopreventwarping.One of the shorteredgesof the rectangularboardis
providedwithperfectlystraightebonyedge whichisusedasworkingedge onwhichthe T-square is
moved
while makingDrawings.
Battens
Workingedge
(ebony)
Fig.1A.1
Note:WhenMinidrafter(Draftingmachine) isusedtoprepare Drawings,the workingedge isnot
used.2ComputerAidedEngineeringDrawing
Drawingboard size:

2. Drawingboardsare made in varioussizes.The selectionof Drawingboarddependsonthe size of
drawingpaperused.The sizesof DrawingboardrecommendedbyBureauof IndianStandards(B.I.S) is
given
below
Standardsize of Drawingboards
DesignationSize (mm) DesignationSize(mm)
B0 1500 × 1000 B3 500 × 350
B1 1000 × 700 B4 250 × 350
B2 700 × 500
b) T-square :
T-squaresare made from hardwood.A T-square consistsof twoparts namelythe stockandthe
blade joinedtogetheratrightanglestoeach otherby meansof screwsand Pinsasshowninfigure 1A.2.
The
stock ismade to slide alongthe workingedge andthe Blade movesonthe Drawingboard.
Workingedge
Blade
Stock
Screws
Fig.1A.2
The workingedge of T-square isusedto draw parallel lines,vertical linesorinclinedlinesat30
°
, 60
o
to the horizontal usingsetsquares.
Draftingmachine (orDrafter):
In a Draftingmachine,the usesandadvantagesof T-square,setsquare,scales,protractorsare

3. combined.One endof the Drafterisclampedat the lefttopendof the Drawingboardby a screw
provided
inthe drafter.
An adjustable headwithaProtractorisfittedat the otherendof the Drafter.Twobladesmade of
transparentcelluloidmaterialare fitted tothe adjustable headandare perfectlyperpendiculartoeach
other.
These bladesare usedtodraw parallel,horizontal,vertical andinclinedlines.The bladesalwaysmove
parallel
to the edgesof the board. Use of Draftingmachine helpsinreducingthe time requiredtoprepare
Drawing.DrawingInstrumentsandtheirUses3
Scale
Scale
Potractor
Angle
Drawingsheet
Drawingboard
Parallel bararm
Parallel bararm
Fig.1A.3
c) SetSquares:
Setsquaresare generallymade fromPlasticorcelluloidmaterial. Theyare triangularinshape with
one corner,a rightangle triangle.A pairof setsquares(30
°
–60
°
) and 45
°

4. (45
°
set square are generallyprovidedwithProtractor) facilitatemarkingof anglesasshowninfigures1A.4
and 1A.5.
Theyare usedto drawlinesat30
°
, 60
°
and 45
°
to the vertical andhorizontal.
mm
1234567891011
mm
1 2 3 4 5 6 7 8 9 1 0 11
mm
1234567891011
mm
1 2 3 4 56
Fig.1A.4. 45 Set Square
0
Fig.1A.5. 30 60 SetSquare
0 0
−4 ComputerAidedEngineeringDrawing
mm
1234567891011

5. mm
1
2 3 4 5 6 7 8 9 10 11
180 170160 150 140130 120 110 100
80 70 60 50 40 30 20 10 0
180
170
160
150
140
130120
110
100
80
7060
50
4030
20100
90
Fig.1A.6. 45 SetSquare withProtractor
0
d) Protractor:
Protractors are usedto mark or measure anglesbetween0and180
°
. Theyare semicircularinshape

6. (of diameter100mm) and are made of Plasticor celluloidwhichhasmore life.Protractorswithcircular
shape
capable of markingand measuring0to 360
°
are alsoavailable inthe market.
180 170 160 150 140 130 120 110 100
80 70 60 50 40 30 20 10 0
180
170160
150
140
130
120
110
100
80
70
60
50
40
30
20
10
0
90
Fig.1A.7

7. e) DrawingInstrumentBox :
It consistsof the following
a) Large size compasses,
b) Large size divider,
c) Small size bowpen,bowdivider,and
d) Lengtheningbar
f) Drawingsheet:
Theyare available inmanyvarietiesandgoodqualitypaperwithsmoothsurface shouldbe selected
for Drawingswhichare to be preservedforlongertime.Sizesof DrawingSheetsrecommendedby
Bureau
of IndianStandards(B.I.S) isgivenbelow,DrawingInstrumentsandtheirUses5
Standardsize of Drawingsheet
DesignationSize (mm) DesignationSize (mm)
A0 1189 × 841 A3 420 × 297
A1 841 × 594 A4 297 × 210
A2 594 × 420 A5 210 × 148
g) DrawingPencils:
The accuracy and appearance of a Drawingdependsonthe qualityof Pencil usedtomake Drawing.The
grade of a Pencil leadismarkedonthe Pencil.HBdenotesmediumgrade.Increaseinhardness
isshownby value putinfrontof H such as 2H, 3H etc.,Softerpencilsare markedas2B, 3B, 4B etc. A
Pencil marked3Bis softerthan2B and Pencil marked4Bis softerthan3B andso on. Beginningof a
Drawingmay be made withH or 2H. For letteringanddimensioning,Hand HB Pencilsare used.
h) DrawingPinsand clips:
These are usedto fix the Drawingsheetonthe Drawingboard.
Compass:
Compassisusedfor drawingcirclesandarcs of circles.The compasshastwo legshingedatone

8. end.One of the legshasa pointedneedle fittedatthe lower endwhere asthe otherendhasprovision
for
insertingpencillead.Circlesupto120mm diametersare drawnbykeepingthe legsof compassstraight.
For
drawingcirclesmore than150 mm radius,a lengtheningbarisused.Itisadvisable tokeepthe needle
end
about1mm longcomparedtothat of pencil endsothat while drawingcircles,whenthe needle endis
pressed
it goesinside the drawingsheetbyasmall distance (approximately1mm).Referfig.1A.8.