ENGINEERING DRAWING (CHAPTER -2)


๐Ÿ“˜ ENGINEERING DRAWING

Chapter 2 – Drawing Instruments and Their Uses

2.1 Introduction

For preparing accurate engineering drawings, special drawing instruments are required. These instruments help to draw straight lines, circles, arcs, curves, and angles precisely according to international standards.
Proper knowledge and correct handling of instruments are essential for producing neat and accurate work.

2.2 Types of Drawing Instruments

(A) Drawing Board

  • Made of well-seasoned softwood or plywood.

  • Surface: Smooth, free from warping.

  • Standard Sizes (as per IS:1444):

    • Full size: 1000 × 700 mm

    • Half size: 700 × 500 mm

    • Quarter size: 500 × 350 mm

  • Use: Base for fixing drawing sheet with clips or tape.

(B) Drawing Sheet

  • Made of good quality paper (cartridge or ivory paper).

  • Standard sizes: A0 to A4 (ISO/BIS).

  • Fixing method:

    • With clips (T-square kept on left edge).

    • Or using masking tape at corners.

(C) Pencils

  • Types: Graphite pencils of different grades.

  • Hardness and darkness indicated by grade:

Pencil Grade Use
6H – 4H Construction lines, very thin lines
2H – H Dimensioning, center lines
HB General purpose drawing
B – 2B Freehand sketching, lettering
3B – 6B Dark shading, bold lines

  • Nowadays, mechanical pencils (0.5 mm, 0.7 mm leads) are also used for neatness.

(D) T-Square

  • Made of wood, celluloid, or plastic.

  • Has head (rested against board edge) and blade (long straight part).

  • Use: Drawing horizontal lines and guiding set-squares.

(E) Set Squares

Two types commonly used:

  1. 45° Set-square – with angles 45°, 45°, 90°

  2. 30°-60° Set-square – with angles 30°, 60°, 90°

  • Use: Drawing vertical lines, inclined lines (30°, 45°, 60°), perpendiculars, etc.

(F) Protractor

  • Semi-circular or circular instrument graduated 0° to 180° (or 0° to 360°).

  • Use: Measuring or constructing angles.

(G) Compass

  • Made of steel or plastic.

  • Used with pencil or pen to draw circles and arcs.

  • Types:

    • Bow compass (precise, spring type).

    • Beam compass (for large circles).

(H) Dividers

  • Similar to compass but with two pointed legs.

  • Use:

    • Transferring measurements from scale to drawing.

    • Dividing a line into equal parts.

(I) French Curve

  • Made of celluloid or plastic with irregular curves.

  • Use: Drawing smooth freeform curves (non-circular).

(J) Mini Drafter

  • A modern instrument that combines T-square, set-square, protractor, and scale.

  • Fixed to the drawing board by a clamp.

  • Provides straight lines at any angle.

(K) Scales (Rulers)

  • Graduated in millimeters and centimeters.

  • Types:

    • Plain scale

    • Diagonal scale

    • Vernier scale

    • Comparative scale

  • Use: Measuring distances and constructing scaled drawings.

(L) Other Instruments

  1. Eraser – For removing pencil lines.

  2. Erasing shield – Thin metal sheet with slots; erases small parts without spoiling rest of drawing.

  3. Drawing pins / clips – For fixing sheet.

  4. Templates – Plastic sheets with pre-cut shapes (circles, ellipses, hexagons, etc.) used for repeated drawing.

2.3 Care of Drawing Instruments

  • Keep instruments clean and dry.

  • Don’t drop compasses or dividers (points get damaged).

  • Keep pencils sharp.

  • Store instruments in a proper box/case.

  • Use light pressure while drawing (avoid damaging paper).

2.4 Summary of Chapter

  • Instruments include drawing board, sheet, pencils, T-square, set-squares, compass, dividers, protractor, French curve, mini drafter, scales.

  • Modern practice uses mini drafters and CAD software.

  • Proper care and maintenance ensure long life and accuracy.


Comments

Post a Comment

Popular posts from this blog

INTRODUCTORY CONCEPTS ( PARTS -2)

Image
               INTRODUCTORY CONCEPTS                                PART-02 * About Protractor:- ๐Ÿ“ เคช्เคฐोเคŸ्เคฐैเค•्เคŸเคฐ (Protractor) เคนिंเคฆी เคฎें: เคช्เคฐोเคŸ्เคฐैเค•्เคŸเคฐ เคเค• เค‡ंเคœीเคจिเคฏเคฐिंเค— เค”เคฐ เคœ्เคฏाเคฎिเคคि เคฎें เค‰เคชเคฏोเค— เค•िเคฏा เคœाเคจे เคตाเคฒा เคฎाเคช เค‰เคชเค•เคฐเคฃ เคนै, เคœिเคธเค•ा เคช्เคฐเคฏोเค— เค•ोเคฃ (Angle) เคจाเคชเคจे เค”เคฐ เคฌเคจाเคจे เค•े เคฒिเค เค•िเคฏा เคœाเคคा เคนै। เคฏเคน เค†เคฎเคคौเคฐ เคชเคฐ เค…เคฐ्เคงเคตृเคค्เคค (180°) เคฏा เคชूเคฐ्เคฃ เคตृเคค्เคค (360°) เค•े เค†เค•ाเคฐ เค•ा เคฌเคจा เคนोเคคा เคนै। เค‡เคธเคฎें เคกिเค—्เคฐी (°) เคฎें เคฎाเคช เค•ी เค—เคˆ เคธ्เค•ेเคฒ เคฌเคจी เคนोเคคी เคนै, เคœैเคธे 0° เคธे 180° เคฏा 0° เคธे 360° เคคเค•। เค‡เคธเค•ा เค‰เคชเคฏोเค— เคฎुเค–्เคฏ เคฐूเคช เคธे เคก्เคฐॉเค‡ंเค—, เคกिเคœ़ाเค‡เคจ, เคฎैเค•ेเคจिเค•เคฒ เคก्เคฐाเคซ्เคŸिंเค— เค”เคฐ เค‡ंเคœीเคจिเคฏเคฐिंเค— เคก्เคฐॉเค‡ंเค— เคฎें เค•िเคฏा เคœाเคคा เคนै। เค‡ंเคœीเคจिเคฏเคฐिंเค— เคฎें เคตिเคถेเคท เคช्เคฐเค•ाเคฐ เค•े เคช्เคฐोเคŸ्เคฐैเค•्เคŸเคฐ เคฎिเคฒเคคे เคนैं, เคœैเคธे Bevel Protractor , เคœिเคธเค•ा เค‰เคชเคฏोเค— เคฌเคนुเคค เคธเคŸीเค• เค•ोเคฃ เคจाเคชเคจे เค”เคฐ เคธेเคŸ เค•เคฐเคจे เค•े เคฒिเค เคนोเคคा เคนै। เค‰เคชเคฏोเค— (Applications): เค•ोเคฃ เคฎाเคชเคจे เคฎें เค•ोเคฃ เคฌเคจाเคจे เคฎें เคฎเคถीเคจ เคชाเคฐ्เคŸ्เคธ เคฏा เคก्เคฐॉเค‡ंเค— เคฎें เคธเคŸीเค• เคฎाเคช เคฒेเคจे เคฎें In English: A Protractor (Protector) is an engineering and geometry meas...
Read more

ENGINEERING DRAWING (CHAPTER 12)

๐Ÿ“˜ ENGINEERING DRAWING Chapter 12 – Isometric Projection 12.1 Introduction In orthographic projection, we need multiple views (FV, TV, SV) to represent an object. But sometimes we need a single pictorial view that shows the 3D appearance . This is achieved by Isometric Projection . ๐Ÿ‘‰ “Isometric” = equal measure (from Greek iso = equal, metron = measure). 12.2 Principle of Isometric Projection Object is imagined inside a transparent cube . Cube is tilted so that one of its body diagonals is perpendicular to the plane of projection. As a result: All three principal axes (X, Y, Z) are equally inclined (120° apart) . Scale along each axis is equally reduced (isometric scale) . 12.3 Isometric Axes and Planes Isometric Axes → Three lines meeting at a point at 120° angles . One vertical, two inclined at 30° to horizontal. Isometric Planes → Planes formed by any two isometric axes. They appear as parallelograms instead of squares....
Read more

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 Universal Language – It is understood across countries irrespective of spoken language. Communic...
Read more