Lesson Notes By Weeks and Term v5 - Grade 10

Lesson Video

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Performance objectives

• Identify and use at least five common drawing instruments.
• Draw horizontal, vertical, and inclined lines correctly.
• Apply standard single-stroke lettering techniques.
• Differentiate and apply at least four standard line types.
• Produce a simple drawing demonstrating these skills.

Lesson summary

Engineering Graphics and Design (EGD) is a visual language. Just like knowing grammar and vocabulary is crucial for writing English, understanding drawing instruments, lettering, and line types is fundamental for creating clear and accurate technical drawings. These skills are essential not only for succeeding in EGD but also for future careers in fields like architecture, engineering (civil, mechanical, electrical), construction, design, and even some artistic professions. Imagine planning the construction of a new RDP house in your community - precise drawings created with these tools are the foundation!

Lesson notes

Drawing Instruments: Drawing Board: A flat, stable surface used as a base for creating drawings. Often made of wood or a similar material. In South Africa, you might see makeshift drawing boards in informal workshops. The key is a perfectly flat surface.

T-Square: A long, flat blade attached to a head that slides along the edge of the drawing board. Used to draw horizontal lines and as a reference for setting angles. The head must sit flush against the edge of the drawing board to ensure accuracy.

Set Squares (Triangles): Typically 45°-45°-90° and 30°-60°-90° triangles. Used with the T-square to draw vertical and inclined lines at specific angles. Understanding how to combine them is key to creating other angles.

Pencils: Different grades of pencils (e.g., 2H, HB, 2B) are used for different purposes. Harder leads (2H) are used for light construction lines, while softer leads (2B) are used for darker, final lines. Never use a regular writing pencil.

Eraser: A soft, pliable eraser is used to remove pencil lines without damaging the drawing paper. A kneaded eraser is useful for lifting graphite without rubbing, preventing smudging.

Compass: Used to draw circles and arcs. Ensure the pencil lead is sharpened to a chisel point for accurate drawing.

Divider: Similar to a compass but with two pointed legs. Used to transfer distances and divide lines or circles into equal parts. Useful for scaling dimensions.

Scale Rule: A ruler calibrated with different scales. Used to create drawings that are proportionally larger or smaller than the actual object. Essential for architectural drawings (e.g., 1:50, 1:100).

Protractor: Used to measure and draw angles.

Lettering: Single-Stroke Gothic: The standard lettering style used in technical drawings. It emphasizes simplicity and legibility. All letters are formed with a single stroke of the pencil for each line segment.

Letter Height: Consistent letter height is crucial for readability. Use light guidelines to maintain uniformity. A good starting height is 5mm.

Letter Spacing: The space between letters should be visually uniform. Avoid overcrowding or excessive spacing. Consider the shapes of adjacent letters when determining spacing.

Word Spacing: Maintain consistent spacing between words, typically equal to the height of the letters.

Example: Practice writing your name and surname repeatedly using single-stroke gothic lettering, focusing on maintaining consistent height and spacing.

Line Types: Standard line types convey specific information in a drawing. It is crucial to understand the meaning of each line.

Visible (Object)

Line: Thick, dark, continuous lines representing the visible edges of an object. Shows the outline of the part you're drawing.

Hidden Line: Dashed lines of medium thickness representing edges that are hidden from view. The dashes should be of uniform length and spacing. Shows features behind the face of the object.

Center Line: A long-short-long dashed line of medium thickness indicating the center of a circle, arc, or symmetrical feature. A very important reference line.

Dimension Line: Thin, continuous lines with arrowheads at both ends, indicating the extent of a dimension. The dimension value is placed above or along the line.

Extension Line: Thin, continuous lines extending from a point on the object to the dimension line. A small gap should be left between the object and the start of the extension line.

Construction Line: Very light, thin lines used for laying out a drawing. These lines should be drawn lightly enough to be easily erased.

Example: Draw a simple rectangle and then add hidden lines to represent a hole drilled through the back that can't be seen from the front. Add a center line to show the location of the hole. Add dimension and extension lines to indicate the size of the rectangle.

Drawing Techniques: Sharpening Pencils: Properly sharpening pencils is essential for accurate drawing. Use a pencil pointer to create a conical point for fine lines or a chisel point for broad lines.

Line Weight: Varying line weight (thickness) helps to emphasize important features and create visual clarity. Visible lines should be thicker than hidden lines or dimension lines.

Parallel Lines: Use the T-square and set squares to draw parallel lines accurately. Position the set square against the T-square and slide it along the T-square to create parallel lines.

Perpendicular Lines: Use the T-square and set squares to draw perpendicular lines accurately. The 90° angle of the set square ensures perpendicularity. Guided Practice (With Solutions)

Question 1: Identify the drawing instrument being described: "This instrument is used to draw circles and arcs. It has two legs, one with a needle point and the other with a pencil lead." Solution: Compass

Commentary: This question tests the basic recognition of drawing instruments based on their function.

Question 2: Draw three horizontal lines of 50mm length each, using a T-square and pencil.