Engineering Drawing and Essential Instruments

Importance of Engineering Drawing

A subcategory of technical drawings is an engineering drawing, which we can define as engineering drawing as a graphical representation with the goal to convey all of the information required to manufacture a product or a component. This is the engineering drawing definition.

Standardized language and symbols are used in engineering drawings. This simplifies the interpretation of the drawings and eliminates the possibility of personal interpretation.

What is Engineering Drawing?

Engineering drawings are detailed diagrams that display all of the details and specifications required to produce a particular object or product. It is a graphical language that communicates ideas and facts, not just a drawing.

An engineering drawing, rather than an image, is used to illustrate the size and shape of a product and can include details such as appropriate variants, load limits, materials, and any other information that may aid in a full understanding of the product.

Types of Drawings Instruments [Instruments Used in Engineering Drawing]

To create tidy and precise drawings, engineering drawing instruments are used. These drawing instruments have specific names and are part of the essential engineering drawing materials.

The standard of the instruments used to prepare the Drawings has a greater impact on the accuracy of the Drawings.

The following is a list of appropriate Drawing Instruments and other materials

1. Drawing Board
2. T-Square or Drafter (Drafting machine)
3. Set Squares
4. Protractor
5. Drawing Instrument Box
6. Drawing Sheet
7. Drawing Pencils
8. Drawing Pins/Clips
9. Compass
10. French Curve
11. Scales (Ruler)
12. Roll & Draw
13. Circle Master
14. Sharpener
15. Eraser
16. Duster or Handkerchief

1. Drawing Board

The drawing board is made of 25 mm thick strips of well-seasoned softwood. Two battens are cleated at the back to keep it from warping.

One of the rectangular board’s shorter edges has a perfectly straight ebony edge that is used as a working edge for moving the T-square when making drawings.

Drawing boards come in a variety of sizes. The drawing board you choose is determined by the size of the drawing paper you’ll be using. The Bureau of Indian Standards (B.I.S.) has proposed the following sizes for drawing boards.

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2.1. T-Square

Strong wood is used to make T-squares, which are important engineering graphics instruments and are among the key drawing instruments in engineering drawing.

A T-square is made up of two parts: the stock and the blade, which are connected at right angles by screws and pins. Set squares are used to draw parallel lines, vertical lines, or inclined lines at 30°, 60° to the horizontal using the working edge of a T-square.

2.2. Drafting Machine (or Drafter)

The advantages and uses of T-square, set square, scales, and protractors are combined in a drafting machine. A screw provided in the Drafter is used to lock one end of the Drafter to the left top end of the Drawing board.

At the other end of the Drafter, an adjustable head with a Protractor is mounted. The adjustable head is fitted with two blades made of translucent celluloid material that are completely perpendicular to each other.

Parallel, horizontal, vertical, and inclined lines are all drawn with these blades. The blades are often parallel to the board’s edges. The use of a drafting machine reduces the amount of time it takes to prepare a drawing.

3. Set Squares

Plastic or celluloid are the most popular materials used to make set squares. They are triangular in shape, with one right-angle triangle as a corner.

A pair of set squares (30°–60°) and 45° (a 45° set square is usually used with a Protractor) make it easier to mark angles. They’re used to draw lines at 30°, 60°, and 45° angles to the vertical and horizontal.

4. Protractor

Protractors, a crucial piece of engineering drawing equipment, are used to calculate or label angles between 0 and 180 degrees.

They have a semicircular shape (diameter 100mm) and are made of plastic or celluloid, which has a longer life span. Protractors with a circular shape that can mark and measure from 0 to 360 degrees are also available on the market

 5. Drawing Instrument Box

It consists of the following components:

1. Large size compasses,
2. Large size divider,
3. Small size bow pen, bow divider, and
4. Lengthening bar.

6. Drawing Sheet

They come in a wide range of colors and textures, and good quality paper with a smooth surface should be chosen for drawings that can be kept for a long time. The Bureau of Indian Standards (B.I.S.) has given the following sizes for drawing sheets.

7. Drawing Pencils

The consistency of the pencil used to create a drawing determines the accuracy and appearance of the drawing. The lead grade of a Pencil is shown on the Pencil. The abbreviation HB stands for “medium grade.”

Harder pencils are labeled with a value in front of H, such as 2H, 3H, and so on. Softer pencils are labeled with 2B, 3B, 4B, and so on. A 3B pencil is softer than a 2B pencil, and a 4B pencil is softer than a 3B pencil, and so on.

The letter H or the number 2H may be used to start a drawing. H and HB Pencils are used for lettering and dimensioning.

8. Drawing Pins and Clips

These two are used to fix the drawing sheet in place on the drawing board.

9. Compass

Circles and arcs of circles is done with a compass. The compass has two hinged legs on one hand.

The lower end of one of the legs is fitted with a pointed needle, while the other end has a provision for inserting pencil lead. The legs of the compass are held straight to draw circles up to 120mm in diameter.

11. French Curve

These have an unusual cross-section and were used to draw small arcs and long splines that a drafter couldn’t draw. They are made of plastic or steel.

11. Scales (Ruler)

A ruler, also known as a rule or line gauge, is a tool used to calculate distances and/or rule straight lines in geometry, technical drawing, printing, and engineering/building.

For technical drawings, you’ll need to use this tool frequently. The scales come in a variety of materials, including plastic, wood, and steel. A steel rule is commonly used to design engineering drawings.

12 Roll and Draw

Roll & Draw is an incredibly useful method for easily generating charts and parallel lines. It’s also known as “the best friend of a draftsman.”

It’s also a multipurpose drawing tool that allows you to quickly and easily draw quadrants, triangles, circles, angles, crosshatching, and vertical and horizontal parallel lines in centimeters.

13. Circle Master

Circle Master is a useful template-type drawing instrument that allows you to quickly draw circles of various radiuses. It does away with the use of a compass since a circle with a fixed radius can be drawn. It’s a flat or circular plate with various-sized holes punched on the top.

If you try to draw a circle with a radius other than the radius punched, you’ll need to use a different drafting instrument because the radius of a circle can’t be changed.

14. Sharpener

A pencil sharpener is a device that shaves the worn surface of a pencil to sharpen the writing edge.

15. Eraser

An eraser is a tool that is used to remove pencil marks from paper or sheets.

16. Duster or Handkerchief

To clean the paper on which the drawing is being done, a duster or handkerchief is often used. They come in a variety of colors and sty.

FAQ: Engineering Drawing and Essential Instruments

What is an engineering drawing?

An engineering drawing is a detailed diagram that displays all the specifications required to produce a particular object or product. It is a graphical language that communicates ideas and facts, illustrating the size, shape, materials, and other relevant details necessary for understanding and manufacturing the product.

Why are standardized language and symbols important in engineering drawings?

Standardized language and symbols in engineering drawings simplify the interpretation of the drawings and eliminate the possibility of personal interpretation, ensuring clarity and consistency in the communication of technical information.

What are the main instruments used in engineering drawing?

The main instruments used in engineering drawing include:

1. Drawing Board
2. T-Square or Drafter (Drafting Machine)
3. Set Squares
4. Protractor
5. Drawing Instrument Box
6. Drawing Sheet
7. Drawing Pencils
8. Drawing Pins/Clips
9. Compass
10. French Curve
11. Scales (Ruler)
12. Roll & Draw
13. Circle Master
14. Sharpener
15. Eraser
16. Duster or Handkerchief

What is the purpose of a drawing board?

A drawing board provides a stable and flat surface for creating drawings. It is typically made of well-seasoned softwood and comes in various sizes according to the drawing paper used. The board includes a perfectly straight working edge for guiding the T-square.

How is a T-square used in engineering drawing?

A T-square, made of strong wood, is used to draw parallel lines, vertical lines, or inclined lines at 30°, 60° to the horizontal. It consists of a stock and a blade connected at right angles and is essential for maintaining the accuracy of lines in drawings.

What is the advantage of using a drafting machine?

A drafting machine combines the functions of a T-square, set square, scales, and protractor. It allows for efficient and precise drawing of parallel, horizontal, vertical, and inclined lines, reducing the time required to prepare a drawing.

What are set squares and how are they used?

Set squares, typically made of plastic or celluloid, are triangular tools used to draw lines at specific angles (30°, 60°, and 45°) to the vertical and horizontal. They are essential for marking precise angles in engineering drawings.

What are the standard sizes of drawing sheets?

According to the Bureau of Indian Standards (B.I.S.), the standard sizes for drawing sheets are:

1. A0: 1189 × 841 mm
2. A1: 841 × 594 mm
3. A2: 594 × 420 mm
4. A3: 420 × 297 mm
5. A4: 297 × 210 mm
6. A5: 210 × 148 mm

How are drawing pencils classified and used?

Drawing pencils are classified based on the hardness of their lead. The abbreviation HB stands for “medium grade.” Harder pencils are labeled with H (e.g., 2H, 3H) and are used for fine lines and details, while softer pencils are labeled with B (e.g., 2B, 3B) and are used for shading and thicker lines.

What is the purpose of a compass in engineering drawing?

A compass is used to draw circles and arcs of circles. It has two hinged legs: one with a pointed needle and the other with a provision for inserting pencil lead. The compass allows for precise creation of circular shapes and measurements.

How is a French curve used in engineering drawing?

A French curve, made of plastic or steel, is used to draw small arcs and long splines that cannot be drawn with a drafter. It has an irregular cross-section suitable for creating various curved lines in drawings.

What is the function of a Circle Master?

A Circle Master is a template-type drawing instrument used to quickly draw circles of various fixed radii. It consists of a plate with holes of different sizes, eliminating the need for a compass for standard-sized circles.

Why is a sharpener important in engineering drawing?

A sharpener is used to maintain the fine point of drawing pencils, ensuring accuracy and precision in creating detailed and clean lines in engineering drawings.

How is an eraser used in engineering drawing?

An eraser is used to remove unwanted pencil marks from paper or sheets, allowing for corrections and adjustments in the drawing.

What is the purpose of a duster or handkerchief in engineering drawing?

A duster or handkerchief is used to clean the drawing surface, removing any debris or pencil shavings that could interfere with the quality of the drawing.