- Case of drawing instruments
- Drawing surface (boardor table)
- Drafting edge(T-square, parallel edge)
- Triangles (30°, 45° )
- Scales (inch)
- Drawing Pencils (H,2H,3H)
- Drafting Tape
- Eraser
- Dry cleaning pad
- Erasing Shield
- Drawing Sheet (regular, scholar)
Introduction
What is Engineering Drawing ?
A fully developed language in its own right: A graphical language that Engineers understand all over the world irrespective of the native tongue. Communication between "DESIGNER and MANUFRACTURER".
Engineering Drawing Requirements
• Unambiguous and Clear
• Complete
• Language Independent
• Conforms to standards
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| Drawing surface(Board or Table) |
Drawing surface (board or table):
Drawing board is rectangular in shape and is made of strips of well-seasoned soft wood about 25mm thick.
One of the edges of the board is used as "working edge" on which the T-square is made to slide. It should, therefore, be perfectly straight.
board:
1) handle the drawing board carefully,so that top flat surface of the board should not be spoiled.
2) fasten an extra sheet on the board to keep the board clean.
The stock is placed adjoining the working edge of the board and is made to slide on it as and when required.
The t-square is used for drawing horizontal lines, (the stock of the t-square is held firmly with the left hand against the working edge of the board, and the line is drawn from left to right. The pencil should be held slightly inclined in the direction of line (i.e. to the right, while the pencil point should be as close as possible to the working edge of the blade.)
The working edge of the t-square is also used as a base for set-squares to draw vertical, inclined or mutually parallel lines.
1) clean the blade of t-square with moist cloth to remove pencil graphite lead.
2) t-square should be hang on the nail against the wall or table when it is not being used.
3) do not use t-square as a hammer.
4) do not use the edge of the t-square as a guide for cutting the paper with a knife.
Set squares are used for drawing all straight lines except the horizontal lines which are usually drawn with t-square.Vertical lines can be drawn with the t-square and the set-square.
The two set squares used simultaneously along with the t-square will produce lines making angles of 15, 75, 105 degrees.
Parallel straight lines in any position as we as lines perpendicular to any line from any given point within or outside it can be drawn with the two set squares.
A circle can be divided in six, eight, twelve and twenty four parts by using set squares and t-square.
2) forty five degree set-square
but thirty-sixty degree set-squares of 250mm and forty five degree set-squares of 200mm are more suitable for general work.
Use of drawing board
The flat surface of the board is used to hold the drawing sheet while the drawing is being made.Cares in handling of drawing board
The following are the cares for handling the drawingboard:
1) handle the drawing board carefully,so that top flat surface of the board should not be spoiled.
2) fasten an extra sheet on the board to keep the board clean.
Drafting edge (T-square, parallel edge)
It consists of two parts, the stock and the blade, joined together at right angle to each other by means of screws and pins.The stock is placed adjoining the working edge of the board and is made to slide on it as and when required.
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| T-Square |
The working edge of the t-square is also used as a base for set-squares to draw vertical, inclined or mutually parallel lines.
Cares in handling of T-square
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| Care in handling of T-Square |
2) t-square should be hang on the nail against the wall or table when it is not being used.
3) do not use t-square as a hammer.
4) do not use the edge of the t-square as a guide for cutting the paper with a knife.
Triangles (30o, 45o)
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| Triangles |
The two set squares used simultaneously along with the t-square will produce lines making angles of 15, 75, 105 degrees.
Parallel straight lines in any position as we as lines perpendicular to any line from any given point within or outside it can be drawn with the two set squares.
A circle can be divided in six, eight, twelve and twenty four parts by using set squares and t-square.
Types of set- squres
1)Thirty-sixty degree set-square2) forty five degree set-square
Sizes of set-squares
The set –squares can be available in different suitable lenghts,but thirty-sixty degree set-squares of 250mm and forty five degree set-squares of 200mm are more suitable for general work.
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| Different Scales |
Scales
all measurements of lenghts or distance on a drawing are made with the scales.
the scales are either flat and triangular and the material used in their construction may be wood,metal etc.
Uses of scales
The following are the uses of scales:
1) it is used to prepare drawing.
2) it is ued to set off dimensions.
3) it is used to measure distance directly.
Drawing Pencils
Drawing pencils are available in vanous grades of hardness or softness. Hard pencils range from grades H. 2H to 9H(the hardest). Soft pencils range from grades B. 2B to 6B(the softest).
Between H and B pencils are the HB and F. All of these pencils are available in the market.
With HB. 2B. and H pencils, the student can easily make vanations in the lightness or darkness of his lines even if the pressure of the pencil on the paper is the same for each grade pencil.
Pencil Points
Pencil points may be sharpened into three different shapes:
A the conical,
B the chisel, and
C. the elliptical.
The conical pointed soft pencil can make different thicknesses of lines by varying the pressure of the pencil against the paper surface. A hard pencil with a similar point can make different thicknesses of lines by varying the shape of its point. A dull point makes a broad line while a fine point makes a fine line.
This is why soft pencils are preferred to hard pencils in sketching.
The chisel point, on the other hand, makes wide lines depending on the width of the point. It is generally used in shading a penciled outline drawing.
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