Lesson Notes By Weeks and Term v3 - Junior Secondary 1
Drawing Instruments and Materials
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Drawing Instruments and Materials
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Subject: Basic Technology
Class: Junior Secondary 1
Term: 2nd Term
Week: 3
Theme: Drawing Practice
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Identify, drawinginstruments and materials Demonstratecorrecttechniques for handling drawinginstruments and materials Construct shapeswith drawinginstruments and materials Care for drawinginstruments and materials
This section provides detailed explanations of common drawing instruments and materials, their uses, and basic care instructions.
A. Drawing Instruments
1. Drawing Board: Description: A smooth, flat, rigid board, usually made of wood (like plywood or MDF) or plastic, with a perfectly straight working edge. It provides a stable surface for drawing. Sizes vary, commonly A3 or A2 for JSS level.
Uses: Provides a firm, flat, and true surface on which to fix the drawing paper for accurate drafting. The straight edge is essential for the T-square.
Care: Keep clean and dry. Avoid scratching or denting the surface. Store flat or upright in a designated safe place to prevent warping.
2. T-Square: Description: A T-shaped instrument consisting of a long blade and a shorter head (stock) fixed at a 90-degree angle. Made of wood, plastic, or metal.
Uses: Used in conjunction with the drawing board's edge to draw horizontal parallel lines. It can also serve as a base for set squares to draw vertical or inclined lines.
Care: Handle by the head or blade, avoiding the working edges. Do not use it as a hammer or ruler to cut directly along. Keep the edges clean and free from nicks. Store flat or hung by the head.
3. Set Squares: Description: Triangular drawing instruments, typically made of transparent plastic. Common types are the 45-degree set square (two 45° angles and one 90° angle) and the 30/60-degree set square (one 30° angle, one 60° angle, and one 90° angle).
Uses: Used for drawing lines at specific angles (45°, 30°, 60°, 90°) and, in combination, other angles (e.g., 15°, 75°, 105°, 120°). When placed against a T-square, they help draw vertical and inclined lines.
Care: Keep clean. Avoid dropping them as the edges can chip, making them inaccurate. Store flat to prevent warping.
4. Protractor: Description: A semicircular or circular instrument, usually made of transparent plastic, marked with degrees (0° to 180° or 0° to 360°).
Uses: Used for measuring and laying out angles.
Care: Keep clean and free from scratches. Store carefully to avoid damaging the markings.
5. Compasses: Description: Consists of two hinged legs, one with a needle point and the other with a pencil or pen holder. Types include bow compasses (for smaller circles) and larger compasses.
Uses: Used for drawing circles and arcs of various radii. Dividers (similar to compasses but with two needle points) are used for transferring measurements or dividing lines.
Care: Ensure the needle point is sharp and the pencil lead is firm and sharp. Keep the joint lubricated if necessary. Store with legs closed.
6. French Curves: Description: Irregularly shaped templates, usually made of plastic, with various curved edges.
Uses: Used for drawing smooth, non-circular curves that cannot be drawn with a compass. Useful in technical illustrations, architectural drawings (e.g., curved walls), and automotive design.
Care: Handle carefully to avoid breaking or chipping. Keep clean.
7. Drawing Pencils: Description: Pencils specifically graded for technical drawing, ranging from very hard (H, 2H, 3H...) to medium (HB, B) to very soft (2B, 3B...). Harder leads (H) produce lighter, finer lines, while softer leads (B) produce darker, thicker lines.
Uses: H, 2H (Harder leads): For construction lines, guidelines, and light details.
HB (Medium lead): For general-purpose drawing, lettering, and outlines. B, 2B (Softer leads): For final outlines, shading, and bold lines.
Care: Sharpen with a knife or sandpaper block to a long conical point, exposing about 10-15mm of lead. Do not use standard sharpeners that create short, blunt points. Store pencils carefully to prevent lead breakage.
8. Eraser (Rubber): Description: Made of soft rubber or plastic material.
Uses: Used to remove unwanted pencil lines or smudges without damaging the paper surface. Kneadable erasers are good for lifting lead without rubbing.
Care: Keep clean. Do not use dirty erasers as they can smudge the drawing. Cut off dirty portions if necessary.
9. Scale Rule (Ruler): Description: A triangular or flat ruler with multiple calibrated edges, often used for drawing at different scales (e.g., firmly with one hand.
5. Place an HB or H pencil against the upper edge of the T-square's blade.
6. Draw a line from left to right (for right-handers) with consistent pressure and pencil angle.
7. Repeat steps 3-6 to draw parallel horizontal lines.
Example 2: Drawing Vertical Lines Procedure:
1. Follow steps 1-3 from Example 1 (for horizontal lines).
2. Place a 90° edge of either the 45° or 30/60° set square firmly against the top edge of the T-square's blade.
3. Hold the T-square and set square firmly with one hand.
4. Place an HB or H pencil against the vertical edge of the set square.
5. Draw a line from bottom to top (or top to bottom, but bottom to top is often cleaner for ink/pencil smudges).
6. Repeat steps to draw parallel vertical lines by sliding the set square along the T-square.
Example 3: Drawing a Square (e.g., 50mm side)
Procedure:
1. Draw a horizontal base line (50mm long) using the T-square and pencil. Mark the two endpoints, say A and B.
2. Place a set square (e.g., 45° or 30/60°) against the T-square, aligning its 90° edge with the base line at point A.
3. Draw a vertical line upwards from A.
4. Repeat step 2-3 at point B, drawing another vertical line upwards.
5. Measure 50mm along the vertical line from A (let's call it C) and from B (let's call it D).
6. Using the T-square, draw a horizontal line connecting C and D to complete the square.
7. Alternative for step 5 & 6: After drawing vertical lines from A and B, slide the T-square up to 50mm from the base line and draw a horizontal line to intersect the two vertical lines.
Example 4: Drawing a Circle (e.g., 30mm diameter) * Procedure:
1. Mark the center point on the drawing paper.
2. Using a ruler, set the compass radius to 15mm (half of 30mm diameter).
3. Place the needle point of the compass firmly on the center point.
4. Rotate the compass (holding it by the top knob) gently and smoothly to draw a full circle with the pencil lead. Ensure consistent pressure to produce a clear, even line. that create short, blunt points. Store pencils carefully to prevent lead breakage.
8. Eraser (Rubber): Description: Made of soft rubber or plastic material.
Uses: Used to remove unwanted pencil lines or smudges without damaging the paper surface. Kneadable erasers are good for lifting lead without rubbing.
Care: Keep clean. Do not use dirty erasers as they can smudge the drawing. Cut off dirty portions if necessary.
9. Scale Rule (Ruler): Description: A triangular or flat ruler with multiple calibrated edges, often used for drawing at different scales (e.g., 1:1, 1:2, 1:5, 1:10, 1:100, etc.). Standard rulers (30cm) are also used.
Uses: Used for measuring distances and drawing straight lines to scale.
Care: Keep clean and free from nicks on the edges. Do not use as a cutting guide with a sharp knife, as this can damage the edge.
B. Drawing Materials
1. Drawing Paper: Description: Smooth, good quality paper that can withstand erasure without tearing or roughing the surface. Available in various sizes (A4, A3, A2, etc.) and weights.
Uses: The primary surface on which technical drawings are made.
Care: Keep flat, dry, and clean. Store in a portfolio or designated cabinet to prevent creasing or damage. Avoid touching the drawing area with oily hands.
2. Masking Tape/Drawing Clips: Description: Masking tape is a low-tack adhesive tape. Drawing clips are small metal clips.
Uses: Used to secure the drawing paper firmly to the drawing board, preventing it from slipping during drawing. Masking tape is preferred as it doesn't leave marks or tear paper upon removal.
Care: Remove tape carefully to avoid tearing the paper. Do not reuse masking tape.
3. Sandpaper Block: Description: A small block of wood with a piece of sandpaper glued to one side.
Uses: Used to sharpen pencil leads to a long, conical point after using a knife, or to maintain a sharp point during drawing without frequent re-sharpening with a knife.
Care: Keep clean and replace sandpaper when worn out. Ensure dust from sharpening does not fall on the drawing.
C. Correct Techniques for Handling Instruments T-Square: Always hold the head firmly against the working edge of the drawing board. Slide it up and down gently, ensuring constant contact. Draw lines from left to right for right-handers, and right to left for left-handers, always against the top edge of the blade.
Set Squares: Place firmly against the T-square's blade. Hold it with one hand while drawing along its edge with the other. Ensure the set square does not slip.
Pencils: Hold the pencil firmly but not too tightly. Maintain a consistent angle (around 60° to the paper) while drawing to produce uniform line weight. Rotate the pencil slightly as you draw long lines to keep the point sharp and wear it evenly.
Compasses: Hold the compass by the top knob. Ensure the needle point is firmly anchored at the center point. Apply gentle, consistent pressure while rotating to draw circles.
Eraser: Use a clean eraser with light, controlled strokes to avoid smudging or damaging the paper. Use an erasing shield (a thin metal template with various cutouts) to protect surrounding lines when erasing specific parts.
D. Constructing Basic Shapes (Examples)
Example 1: Drawing Horizontal Lines Procedure:
1. Fix drawing paper onto the drawing board using masking tape or clips.
2. Place the T-square on the drawing board, ensuring its head is firmly against the left (or right) edge of the board.
3. Slide the T-square to the desired vertical position.
4. Hold the T-square firmly with one hand.
5. Place an HB or H pencil against the upper edge of the T-square's blade.
6. Draw a line from left to right (for right-handers) with consistent pressure and pencil angle.
7. Repeat steps 3-6 to draw parallel horizontal lines.
Example 2: Drawing Vertical Lines Procedure:
1. Follow steps 1-3 from Example 1 (for horizontal lines).
2. Place a 90° edge of either the 45° or 30/60° set square firmly against the top edge of the T-square's blade.
3. Hold the T-square and set square firmly with Phase 1: Introduction and Identification (15 minutes)
Teacher Activities: Displays a collection of various drawing instruments and materials (real objects if available, otherwise clear diagrams/posters). Asks students if they recognize any of the items and what they think they are used for. Briefly explains the relevance of technical drawing in everyday life in Nigeria (e.g., constructing houses, designing clothes, making furniture).
Introduces the lesson topic: "Drawing Instruments and Materials." Presents each instrument/material one by one, naming it clearly.
Student Activities: Observe the displayed instruments and materials. Participate in the initial discussion, sharing prior knowledge or guesses about the tools. Listen attentively as the teacher introduces each item. Write down the names of the instruments as they are introduced.
Phase 2: Explanation of Uses and Handling Techniques (20 minutes)
Teacher Activities: For each identified instrument/material, explains its specific use(s) in technical drawing. Demonstrates the correct technique for handling and using each instrument: How to hold the T-square and slide it on the board. How to position and hold set squares against the T-square. How to hold and sharpen pencils (using a knife and sandpaper block). How to set and use a compass for drawing circles/arcs. How to use an eraser effectively. How to secure paper to the drawing board. Emphasizes common mistakes and how to avoid them (e.g., not letting the T-square head lift off the board, not dropping set squares).
Student Activities: Observe the teacher's demonstrations carefully. Take notes on the uses of each instrument and the correct handling techniques. If possible, practice holding some non-sharp instruments (e.g., T-square, set square) without drawing on paper to mimic the handling. Ask clarifying questions regarding handling techniques.
Phase 3: Practical Application - Constructing Shapes (30 minutes)
Teacher Activities: Distributes drawing paper, pencils (HB, H), rulers, T-squares, set squares, and compasses to student groups or individuals (depending on availability). Guides students through step-by-step construction of basic shapes on paper: Drawing horizontal parallel lines using a T-square. Drawing vertical parallel lines using a T-square and set square. Drawing a simple square (e.g., 50mm x 50mm). Drawing a circle of a specified radius (e.g., 30mm diameter). Circulates among students, providing individual guidance, correcting techniques, and reinforcing proper usage. Encourages peer-to-peer learning within groups.
Student Activities: Set up their drawing materials on their workspaces. Follow the teacher's instructions to practice drawing horizontal and vertical lines. Attempt to construct a square and a circle, applying the learned handling techniques. Seek assistance from the teacher or peers when encountering difficulties.
Phase 4: Care and Maintenance (10 minutes)
Teacher Activities: Initiates a discussion on the importance of caring for drawing instruments. Explains specific care and maintenance practices for each instrument/material (e.g., cleaning, storage, sharpening pencils, protecting edges). Emphasizes that proper care extends the life of the instruments and ensures accuracy in drawing.
Student Activities: Contribute ideas on how to care for the instruments. Take notes on the recommended care and maintenance procedures. Discuss the impact of poor care on the quality of drawings and the longevity of the tools.
Phase 5: Wrap-up and Assessment (5 minutes)
Teacher Activities: Conducts a quick Q&A session to recap key instruments, uses, handling, and care. Assigns homework or sets the stage for the next lesson.
Student Activities: Participate in the recap Q&A. Ensure their workspace is tidy and instruments are put away correctly.
Architecture and Building Construction (Housing/Infrastructure): In Nigeria, skilled draftsmen and architects use these instruments to create detailed building plans for residential houses, schools, hospitals, and commercial structures. Accurate drawings ensure that builders construct safe and functional buildings, minimizing errors and material waste. For example, a student learning to draw a square can connect it to drawing the outline of a room or a foundation slab for a new building in their community. Product Design and Manufacturing (Local Industries): Whether it's designing simple farm tools, furniture (e.g., for local carpenters in Akwa Ibom or Abia State), or even patterns for textiles and fashion (e.g., for tailors in Lagos or Kano), technical drawing skills are fundamental. The ability to precisely draw and dimension components ensures that products are functional, aesthetically pleasing, and can be manufactured consistently. A student using a compass to draw circles can relate it to designing a round stool top or a specific part of a machine. Mapping and Urban Planning (Community Development): Basic drawing instruments are used in cartography and urban planning to create maps and layout plans for towns and cities. These plans guide the placement of roads, drainage systems, markets, and public facilities. Understanding how to draw lines and shapes with precision can be linked to sketching a layout of their school compound or a small section of their village, highlighting the importance of organized development.