Branch: : INFORMATION TECHNOLOGY

TOPIC : :introduction of egPresented by: Acharya Mansi Akshay Dhanani Aandhi Aasif Ankoliya RitenGuided by: Jay Shah

DRAWING INSTRUMENTSSHEET LAYOUTSCALESLINES

Engineering drawing is a technique of creating graphical representation that contains all necessary information such as dimensions, specifications and notes, using which an abstract concept can be transformed into real world object. Application of engineering drawing are valid for e.g.: Shipping industry, manufacturing, construction and many more.

Some important concept of engineering drawing is like projection. The word projection means to throw forward. It is a process of plotting an object in an imaginary plane. Projection has two types:

1. Parallel projection2. Perspective projection Each of these has further subtypes.

1. Drawing paper: The size of drawing paper should be less than drawing board and paper should be fixed properly.

2. Drawing board: It is a plane and smooth surface use for drawing purpose.

3. T-square: It is a T shape drawing tool whose edge slide along width of drawing board with the help of stop. It is useful in drawing straight line.

4. Compass: It is used for drawing circles and arcs. The divider is little different with both legs made of steel and use for transferring distance.

5. French Curves: They are used to draw irregular curves such as ellipse, hyperbola and parabola.

6. Drafter: It is useful tool for drawing parallel lines at any inclination. It has scale as well as protractor inbuilt.

7. Protractor: It is use to measure and layout angles.8. Set Square: It is also known as triangle. They comes

in flavors of 30, 60, 30 and 45, 90, 45.

Typical Drawing Equipment

Objectives in Drawing

1. Accuracy

2. Speed

3. Legibility

4. Neatness

It is useful tool for drawing parallel lines at any inclination. It has scale as well as protractor inbuilt.

They are used to draw irregular curves such as ellipse, parabola and hyperbola.

Drawing Boards

The left edge and right edge of a drawing board has a true straight edge.

For right-handed people, the left-hand edge of the board is called the working edge because the T-square head slides against it.

For left-handed people, the right-hand edge of the board is called the working edge because the T-square head slides against it.

T-Squares

The T-square is made of a long strip called the blade, fastened at right angles to a shorter piece called the head.

The drawing paper should be placed close to the working edge of the board to reduce any error resulting from the bending of the blade of the T-square.

The paper should also be placed close enough to the upper edge of the board to permit space at the bottom of the sheet for using the T-square.

Drafting tape is used to fasten the drawing paper to the drawing board.

Drawing Pencils

High-quality drawing pencils should be used in technical drawing, never ordinary writing pencils.

Many makes of mechanical pencils are available together with refill leads in all grades. Choose a mechanical pencil that feels comfortable in your hand.

HARD MEDIUM SOFT

9H 8H 7H 6H 5H 4H 3H 2H H F HB B 2B 3B 4B 5B 6B 7B

Hard leads are used where extreme accuracy is required. Generally these leads are used for construction lines.

Medium leads are used for general purpose line work in technical drawing.

Soft leads are used for various kinds of art work. These leads are too soft to be useful in mechanical drafting.

Drawing Leads

The first consideration in the selection of a grade of lead is the type of line work required. For light construction lines and guide lines for lettering use a hard lead. For all other line work, the lines should be BLACK. The lead chosen should be soft enough to produce jet black lines but hard enough not to smudge.

TrianglesMost inclined lines are drawn at standard angles using the 45º x 45º triangle and the 30º x 60º triangle.

In addition to drawing angles of 90º, 45º, 30º, and 60º, triangles can be combined to draw angles of 15º increments.

ScalesScales are instruments used in making technical drawings full size or at a given reduction or enlargement.

Types of scales include metric scales, engineers’ scales, decimal scales, mechanical engineers’ scales, and architects’ scales.

Scales are usually made of plastic or boxwood and are either triangular of flat in shape.

Margin: Margin is provided in the drawing sheet by drawing margin lines. Prints are trimmed along this lines.

Border lines: Clear working space is obtained by drawing border lines. More space is kept on the left-hand side for the purpose of filling or binding if necessary.

Borders and frames: SP:46(2003) recommends the borders of 20mm width for the sheet sizes A0 and A1, and 10mm for sizes A2, A3, A4 and A5.

Title Block: Space for title block must be provided in the bottom right-hand corner of the drawing sheet. The size of the title block as recommended by the B.I.S is 185mm*65mm for all designations of the drawing sheet. All title blocks should contain at least the particulars as shown in the figure:

Main Line Types

Lines

Hidden Lines

Center Lines

Dimension Lines

Extension Lines

Leader LinesCutting Planes

Section Lines

Phantom Lines

Viewing Planes

Break Lines

Visible Lines

Dimension Lines• Thin lines capped on the ends with arrowheads and

broken along their length to provide a space for the dimension numeral.

• They indicate length.

Center Lines• Thin line consisting of alternating long and short

dashes.• Used to represent the center of round or cylindrical

features, or the symmetry of a feature.

Section Lines

• Thin line usually drawn at a 45 degree angle.• Indicates the material that has been cut through in a

sectional view.

Section Line

Hidden Lines• Light, narrow, short, dashed lines.• Shows the outline of a feature that can not be seen in

a particular view.• Used to help clarify a feature, but can be omitted if

they clutter a drawing.