Engineering Drawing
Engineering Drawing by Er Amit sir
CH-1 Drawing instruments and their uses
Introduction of drawing
For any drawing or construction of building ,instruments have take an important role.with the help of an instrument we prepare drawing easily and accurately. The accuracy of any drawing depends on the quality of instruments.good quality instrument gives good drawing.
Drawing instruments-
Drawing instruments which are used for drawing purpose are given bellow.
1-Drawing board
2-T-suare
3-Set squares 30 to 60 degree & 45 degree
4-Drawing instrument geometry box which have containing instruments large size compass with interchangeable pencil and pen , small bow compass,large size divider,small bow divider,small bow ink pen , inking pen
5-Protractor
6-Scales
7-Drawing papers
8-Drawing pencils
9-Eraser
10-Duster
11-Drafting Machine
Drawing board-
The shape of drawing board is rectangular and this board is made of strings of well seasoned soft wood about 25mm thick. It is claeted at the by two battens to prevent warping. drawing board is made in various sizes , its use depends upon the drawing paper to be used. The size of drawing boards recommended by the Bureau of Indian Standards (IS: 1444-1989).
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Fig-Drawing board
NOTE-
1- For the school and college mostly B2, B3 boards are used.
2-Large size boards are used in drawing offices of engineers .
3-For proper drawing the table face sloping towards the students
2 T-SQUARE
»T-SQOURE is an important tool for drawing ,it is made by hard quality wood .
It consists of two parts Stock and Blade, both parts are joining together at right angle to each other.
Use of T-Square
2-The T-Square is held by one hand and draw
the lines by other hand
3-The working edge is also use for draw the
vertical lines
4-for testing the straightness of the line mark
any two points A and B
5- T-Square should never be used on edge other
than the working edge of the board
3-Set -Squares
The set squares are made of wood, tin and plastic .commonly celluloid or plastic are used because they retain their shape and accuracy for a longer time.
There are two types of set squares are used
1-A set square triangular in shape which have angle 45-90-45 degree and 250 mm edge length
2- A set square triangular in shape which have angle 30-90-60 degree and 200 mm edge length
Use of Set Squares
1- Set squares are used for drawing all straight line except the horizontal line because horizontal line draw with T-Squares .
2-vertical lines can be drawn by the help of T-Squares and Set-Squares
3-By using of set squares a circle can be divided in so many parts.
4- It can draw perpendicular lines easily .
4- DRAWING INSTRUMENT BOX
The drawing instrument tools contains so many tools which are given bellow
1-Large size compass
2-Small bow compass
3-Large size divider
4-Small bow divider
5-Lengthening bar
6-Small bow ink pen
7- Inking pen
1-Large size compass
a- This compass is used for drawing circles and arc of a circles
b-It consists two legs hinged together at it upper end
c-Pointed needle is fitted at the lower end of the leg
d-Circle up to 120 mm diameter cam be drawn with the leg of compass
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Large size compass |
2-Small bow compass
a-By the help of small bow compass we draw the small circles and arcs
b-when large number of circles of the same diameter are drawn then we use small bow compass
c-In this compass used H or HB pencil to make line or circle in proper darkness.
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Small bow compass |
Use of large size divider
1-It is used to provide curved or straight lines in two desired number of equal parts.
2-It is used to transfer the dimensions from one part of the drawing to another part
of the drawing.
3-It is used to set the distance from the scale to drawing.
This device is very important for drawing because it provide exact dimensions and measurements.
4-Small bow divider-
The small bow divider is adjusted by nut at the top of the instrument ,it is very convenient for marking
minute divisions and large number of short equal distance.
5- Lengthening bar
Lengthening bar is used for circle of more than 150 mm radius
It is used when the lower part of pencil leg is detached and the
lengthening bar inserted inits place.
By this bar the length of the compass can be increased which
made big radius .
6-Small bow ink pen-
It is also an important tool for drawing ,it is used for drawing small circles and arc in link
7-Inking -Pen
Inking-Pen is used for drawing straight lines and non circular arcs in link .
It consists of a pair of steel nibs fitted to a holder made of metal.
Ink is fitted between two nibs to about 6 mm length.
Scale
1- Scale is a measuring instrument by which we measure the distances .
2- It is made of wood ,steel,celluloid or plastic or card board.
3- Stainless steel scale are more durable .
4- Scales are (15 cm long and 2 cm wide ) or (30 cm long and 3 cm wide )
5- Scales are in common use is 1 mm thick.
6- The card board scale are available in a set of 8 scales 
Protractor
1- protractor of transparent celluloid are common use ..
2-It is also made of wood and tin.
3- They are flat and circular and or semicircular in shape.
4- It have 0 - 180 degree angle presentation in both sides
5- Its center o is mention at that point 90 degree exist at the top
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| Protractor |
Drawing Paper
1- Drawing paper are available in many varieties
2- For ordinary pencil drawing the paper selected should be tough and strong
3-It should be uniform in thickness and have good whiteness
4- when the rubber eraser are used on the paper it fibers should not disintegrate
Note-Size of drawing papers are given bellow
A 0 (841 mm x 1189 mm)
A 1 (594 mm x 841 mm)
A 2 (420 mm x 594 mm)
A 3 (297 mm x 420 mm)
A 4 (210 mm x 297 mm)
A 5 (148 mm x 210 mm)
Decreasing order of size is given as-
A0 > A1 >A2 > A3> A4> A5
A0 is big size A5 is small size
Drawing Pencil
(H ,2H,3H,4H)etc
1- The quality and appearance of a drawing depend upon the quality of pencils used
2- Beginning of a drawing should be made with H or 2H pencil ,using it very lightly because of after drawing extra lines can be erase easily
3- H and HB pencils are more suitable for lettering and dimension
Eraser
1-Soft rubber is the most suitable Eraser for pencil drawing.
2- It does not spoil the surface of the paper.
Duster
Duster should be used for cleaning the surface to drawing board before we start the drawing
If duster not available then we use piece of towel
Drafting machine
1- Drafting machine is called MD in short
2-In this machine T-Square , Set Square, Scales and Protractor are assembled
3- By the help of this machine we draw Horizontal, vertical lines with accuracy
4-It is the main instrument of drawing in drawing board
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Drafting machine
Ch-2 Sheet Layout for Drawing
Sheet Layout
There are some important terms which decide the proper drawing and sheet layout .
All terms are given below-
1- Sheet Size
2- Margin
3-Border Lines
4-Orientation mark
5-Grid reference system
6- Title Block
7- scaling of drawing
1-Sheet Size
Sheet size of drawing is recommended by the Bureau of Indian standards (B.I.S.)are given below
A 0 (841 mm x 1189 mm)
A 1 (594 mm x 841 mm)
A 2 (420 mm x 594 mm)
A 3 (297 mm x 420 mm)
A 4 (210 mm x 297 mm)
A 5 (148 mm x 210 mm)
For Engineering drawing purpose generally use A 1 (594 mm - 841 mm) size
All dimensions are in -mm
2-Margin
Margin is provided in the drawing sheet before make a drawing
Margin gives the trimmed size of the drawing sheet.
Margin is generally taken (10mm-20mm)
3-Border Lines
Border line sketch 10 mm- 20 mm inside from the margin line in drawing sheet.
according to SP: 46 (2003)
Border are 20 mm width for sheet size A0 and A1
Border are 10 mm width for sheet size A2 ,A3,A4,A5
For Engineering drawing purpose generally use A1 sheet
4-Orientation mark
Centering marks on the drawing sheet for the purpose of facilitate positioning of the drawing for reproduction purpose.
There are minimum four centering marks in a drawing sheet
The orientation mark will coincide with one of centering marks which can be used for the orientation of the drawing board
5-Grid reference system
The aim of grid system on the sheet to permit easy location on the drawing such as detail ,additions
Grid along the length should be 1,2,3,4,5......etc
Grid along the width should be A,B,C,D,E......etc as shown in fig 2-1 b
6-Title block
The size of title block according to B.I.S. is 185 mm X 65mm for drawing sheet.
vertical partition of sheet from right side is 20mm , 25mm and 10mm as in given fig 2-2
Horizontal partition of sheet from top is 10mm,7mm,7mm,7mm,7mm,7mm,20mm
7-Scaling of drawing
Scaling of drawing is an important thing by which we can draw the big size plan in a small drawing
sheet.
Reducing scale 1:2 ,1:5, 1:20 ,1:1000 etc
Enlarging scale 50:1 ,20:1 ,10:1 etc
full size scale is 1:1
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