Theroy

Engineering drawing can be considered as the universal language of engineers that allows them to communicate complex ideas, designs, and technical information effectively. Engineering drawings play a crucial role in manufacturing, construction, and various industries to ensure accurate and standardized production or implementation of designs.

Some of the tools used in engineering drawing are mentioned below:

Drawing Board-

1. It is a rectangular board made up of well-seasoned softwood, having a thickness of about 25 mm. The drawing board is provided with two battens to prevent its twisting.

2. One edge of the board is used as a working edge for T-squares. Nowadays, mini drafters are used in place of T-squares.

3. The board is available in various sizes depending on the size of the drawing paper to be used.

Drawing Sheet-

1. It is the medium on which engineering drawings can be made. These sheets are available in the following standard sizes:

Paper Size	Length (mm)	Width (mm)
A0	1189	841
A1	841	594
A2	594	420
A3	420	297
A4	297	210
A5	210	148

2. Border lines are drawn to provide a clear working space. The space on the left side is more for the means of binding or filing.

Title Block-

A title block is placed at the bottom right-hand corner of the drawing sheet, having a standard size of 185 mm × 65 mm (ISO standard). However, an alternative size of 150 mm × 50 mm (institutional) may be used where space is limited, irrespective of the sheet designation. The title block includes the following details:

• Name of the firm • The drawing title • Scale of the drawing • Drawing number • Initials with dates of person who have designed and approved the sheet. • Symbols denoting the method of projection.

Mini drafter

1. A mini drafter is a drawing instrument which is a combination of T-squares, scales, set squares and protractors.

2. One end of the drafter is fastened using a screw to the longer edge of the drawing board. While another end of the drafter consists of an adjustable head having a protractor.

3. Two scales having blades set at right angles to each other are fitted to the head of drafter. The scales are provided with markings for construction.

4. A mini drafter is used to construct vertical, horizontal and inclined parallel lines of the desired dimensions.

Pencils

1. The quality and the grade of a pencil greatly determine the accuracy and appearance of the drawing. Different grades of pencils can be obtained depending on their hardness and softness.

2. Pencils with softer grades are denoted by B, 2B, 3B, etc. Similarly, pencils with harder grades are indicated with H, 2H, 3H, etc.

3. Border lines are drawn with HB pencil of medium grade.

4. Visible outlines and edges are drawn with a pencil of H or 2H grade. The construction lines,extension lines, leader lines, and hatching lines are drawn with a pencil of 3H grade.

Set square-

1. Set squares is a triangular drawing instrument with one of the angles set at 90°. Set squares of 45° and 30°-60° are widely used in schools and colleges.

2. In combination with T-squares, 30°-60° set squares are used for constructing vertical and horizontal lines at 30° and 60°. Similarly, 45° set squares are used to draw horizontal and vertical lines at 45°. The combination of two set squares helps in constructing lines at angles of 15°, 75°, 105°, etc.

3. Set squares also help in dividing circles into six, eight, twelve and twenty-four equal parts.

Compass-

1. A compass is used to draw circle and arcs

2. A large compass is generally used which has a knee-joint in one leg where the pencil can be adjusted. It is used for constructing bigger circles and for larger dimensions.

Lines-

Different types of lines are used in engineering drawing which are described as follows: