Lesson Notes By Weeks and Term v5 - Grade 10

Lesson Video

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Performance objectives

• Identify and correctly use at least five common drawing instruments.
• Apply standard lettering techniques for neat and legible text.
• Differentiate between and accurately draw at least four different line types.
• Create a simple drawing incorporating these skills.

Lesson summary

Engineering Graphics and Design (EGD) isn't just about pretty pictures; it's a visual language used by engineers, architects, and designers to communicate ideas clearly and accurately. In South Africa, with its growing infrastructure and manufacturing sectors, understanding EGD principles is crucial. From designing affordable housing in Khayelitsha to planning new Gautrain extensions, EGD skills are in high demand. This week, we'll focus on the fundamental building blocks: drawing instruments, lettering techniques, and different types of lines. Mastering these basics will enable you to create accurate and professional drawings, essential for conveying your designs effectively.

Lesson notes

2.1 Drawing Instruments: Accuracy in EGD starts with the right tools. Understanding their function and proper use is paramount.

Drawing Board: A stable, flat surface is essential. Ensure it is clean and free from imperfections. Size should be appropriate for the drawings you intend to create.

T-Square: Used to draw horizontal lines and to guide set squares. Hold the head firmly against the edge of the drawing board.

Important: Check that the T-square is truly square to the board.

Set Squares: Typically 45°-45°-90° and 30°-60°-90° triangles. Used in conjunction with the T-square to draw vertical and inclined lines.

Compass: Used to draw circles and arcs. Ensure the pencil lead is sharpened to a fine chisel point, and the compass point is secure. Maintain consistent pressure for smooth curves.

Example: Drawing a circular base for a cylindrical water tank design.

Dividers: Used to transfer distances and divide lines into equal segments.

Scales: (Rulers, scale rulers): Used to measure distances accurately. A scale ruler allows you to work with scaled drawings (e.g., 1:50, 1:100) directly without complex calculations. Imagine designing a house on a small piece of paper but ensuring the actual house can be built to the right dimensions.

Pencils: Different grades (H, HB, B) are used for different purposes. Harder pencils (H grades) are for light construction lines, while softer pencils (B grades) are for darker, final lines. HB is a good general-purpose pencil. Sharpness is crucial; invest in a good pencil sharpener.

Eraser: Use a soft, non-abrasive eraser to remove unwanted lines cleanly.

Templates: Pre-cut shapes (circles, squares, etc.) for drawing repetitive features quickly and accurately.

Protractor: Used to measure and draw angles. 2.2 Lettering: Lettering in EGD must be clear, legible, and standardized. SANS 0111 (South African National Standard) specifies the guidelines.

General Principles: Use single-stroke lettering (no shading or outlines). Maintain consistent letter height, spacing between letters and words, and line thickness.

Letter Height: The standard height for capital letters is generally 3.5 mm or 5 mm, depending on the drawing size.

Spacing: The spacing between letters should be visually equal, not mechanically measured. Spacing between words should be approximately the width of a capital letter.

Style: Use a simple, upright (vertical) or inclined (slanted) style. Avoid fancy or ornate fonts.

Example: Labeling the components of a simple circuit diagram. Instead of writing it however you wish, the labels have to have uniform height and style. 2.3 Line Types: Different line types convey different information on a drawing. SANS standards dictate how these lines must be drawn.

Visible Line (Continuous Thick): Represents visible edges and outlines of an object. Drawn thick and solid. This line shows you what you can see.

Hidden Line (Dashed): Represents edges and outlines that are hidden from view. Drawn as short, evenly spaced dashes.

Think about pipes behind a wall: you can't see them, so you represent them with a dashed line. Centre Line (Long Dash - Short Dash - Long Dash): Indicates the centre of a circle, arc, or symmetrical feature. Drawn as a thin line with alternating long and short dashes. Cutting Plane Line (Long Dash - Double Short Dash - Long Dash): Indicates the location of a cutting plane used to create a sectional view. Drawn thick at the ends and where it changes direction. Dimension Line (Continuous Thin with Arrows): Indicates the length of a dimension. Drawn thin with arrowheads at each end.

Extension Line (Continuous Thin): Extends from the object to the dimension line. Drawn thin.

Construction Line (Continuous Very Thin): Lightly drawn lines used for setting up a drawing. These should be barely visible and are erased when the drawing is complete.