ENGINEERING DRAWING (CHAPTER -1)


๐Ÿ“˜ ENGINEERING DRAWING

Chapter 1 – Introduction to Engineering Drawing

1.1 What is Engineering Drawing?

Engineering Drawing is a graphic language of engineers and technicians.
It is the universal language of engineering through which ideas, designs, and specifications are conveyed clearly and accurately.

Unlike freehand sketches, engineering drawing follows international standards so that a drawing made in one country can be understood by engineers anywhere in the world.

  • Definition:
    “Engineering Drawing is a language of lines, symbols, and notes used by engineers to convey information about objects, machines, structures, and systems.”

  • Example:
    A machine designer in India can prepare a drawing of a gear, and the same drawing can be manufactured in Germany or Japan without confusion if proper drawing standards are followed.

1.2 Importance of Engineering Drawing

  1. Universal Language – It is understood across countries irrespective of spoken language.

  2. Communication Tool – It conveys exact shape, size, and specifications of objects.

  3. Manufacturing Guide – A machinist produces parts by following engineering drawings.

  4. Legal Document – Approved engineering drawings act as legal documents for production.

  5. Error Reduction – Clear drawings reduce chances of mistakes in manufacturing.

1.3 Difference Between Freehand Sketching and Engineering Drawing

Aspect Freehand Sketch Engineering Drawing
Accuracy Rough & not to scale Accurate & to scale
Tools Used Pencil, paper only Instruments (scale, compass, etc.)
Standards No strict standard Follows BIS/ISO standards
Application Idea representation Manufacturing & construction

1.4 Types of Engineering Drawing

  1. Machine Drawing

    • Deals with machine parts (nuts, bolts, shafts, gears).

    • Example: Drawing of an engine crankshaft.

  2. Production Drawing

    • Contains full details needed for manufacturing (dimensions, materials, tolerances).

  3. Assembly Drawing

    • Shows how different parts fit together.

    • Example: Motor assembly drawing.

  4. Civil/Building Drawing

    • Used in construction (plans, elevations, sections).

  5. Electrical Drawing

    • Symbols and wiring diagrams for circuits.

  6. Structural Drawing

    • Bridges, dams, trusses, frames.

1.5 Standards in Engineering Drawing

  • BIS (Bureau of Indian Standards) – Indian Standard (SP:46, IS:10711).

  • ISO (International Organization for Standardization).

  • ANSI (American National Standards Institute).

๐Ÿ‘‰ These standards define line thickness, symbols, projection methods, sheet sizes, and dimensioning rules.

1.6 Sheet Sizes (as per ISO and BIS)

  • Drawing sheets are designated as A0, A1, A2, A3, A4.

  • Size is based on A0 = 1 m² area.

  • Each next size is half of the previous.

Sheet Size (mm × mm)
A0 841 × 1189
A1 594 × 841
A2 420 × 594
A3 297 × 420
A4 210 × 297

1.7 Method of Projection

Two main methods of projection used:

  1. First Angle Projection (European method, used in India)

  2. Third Angle Projection (American method)

๐Ÿ‘‰ Symbols are placed in title block to indicate which system is used.

1.8 Summary of Chapter

  • Engineering Drawing is the language of engineers.

  • It ensures clear communication in design and manufacturing.

  • Different types include machine, civil, electrical, production, assembly drawings.

  • It follows international standards (BIS/ISO).

  • Sheet sizes and projection methods are standardized.


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