Lesson Notes By Weeks and Term v3 - Junior Secondary 1
Board Practice
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Board Practice
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Subject: Basic Technology
Class: Junior Secondary 1
Term: 2nd Term
Week: 3
Theme: Drawing Practice
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Fix drawing sheet to the board Sharpen pencils to conical point and knife edge Draw border,horizontal and verticallines Place and draw the title block. Write freehand legibleletters and numerals.
Drawing Board: A flat, smooth surface (usually wood or pressed wood) used as a base for technical drawing. It must have a perfectly straight working edge for the T-square.
Types:* Portable boards (smaller, often A3 or A2 size) suitable for classroom use, and larger boards (often with parallel motion mechanisms) for professional use.
Care:* Keep clean and free from scratches.
T-square: An instrument used for drawing horizontal lines and for supporting set squares to draw vertical or inclined lines.
Parts:* The "stock" (head) and the "blade." The stock runs along the working edge of the drawing board.
Use:* Always held firmly against the left edge of the drawing board (for right-handed users) or right edge (for left-handed users).
Set Squares: Triangular drawing instruments, typically made of clear plastic. They are used in conjunction with the T-square to draw vertical and inclined lines.
Types:* 45-degree set square (for 45, 90, 135 degrees), and 30/60-degree set square (for 30, 60, 90, 120, 150 degrees). Combinations of set squares can produce other angles.
Use:* Place on top of the T-square blade.
Pencils: Graded by hardness. Hard Grades (H, 2H, 3H, etc.):* Produce light, thin lines, used for construction lines and initial layouts. 2H is commonly used for light lines. Medium Grades (HB, F):* General purpose, for lettering and visible lines. HB is common for general writing and outlining. Soft Grades (B, 2B, 3B, etc.):* Produce dark, thick lines, often used for sketching or final outlines. (Less common in technical drawing for precise lines). Nigerian Context
Example:* For architectural plans of a compound house, 2H might be used for initial room layouts, while HB is used for final wall lines, and B for darker outlines of doors.
Drawing Sheet: Standard sizes include A4 (210 x 297 mm), A3 (297 x 420 mm), A2 (420 x 594 mm). For JSS1 board practice, A3 or A2 are most suitable to allow space for exercises.
Masking Tape/Thumbtacks: Used to fix the drawing sheet to the board. Masking tape is generally preferred as it causes less damage to the board and sheet. Correct pencil sharpening is crucial for producing consistent line work.
Conical Point: Use a sharpener (manual or mechanical) to remove wood from the pencil end, creating a sharp, pointed lead. For higher precision, gently rub the lead on fine sandpaper or a sharpening block while rotating the pencil, to achieve a needle-sharp point.
Use: Primarily for general sketching, lettering, and marking points.
Knife Edge (Chisel Point): Using a utility knife or razor blade, carefully shave off the wood from one side of the pencil for about 10-15mm, exposing a long length of lead. Flatten the exposed lead on a sharpening block or sandpaper to create a flat, chisel-shaped edge. Rotate 90 degrees and flatten the other side to make it a uniform 'knife' edge.
Use: Ideal for drawing long, consistent lines against a T-square or set square, as it provides a constant line thickness without needing frequent rotation. This is highly recommended for lines in technical drawing. Safety
Note: Emphasize extreme caution when using a utility knife. Supervise closely. A correctly fixed sheet ensures all lines drawn are parallel or perpendicular to each other and to the board's edge.
Preparation: Ensure the drawing board surface is clean and smooth.
Placement: Place the drawing sheet on the board, leaving a margin of space from the working edge (usually the left edge for right-handed users).
Alignment with T-square: Place the T-square stock firmly against the working edge of the board. Bring the blade of the T-square up to the bottom edge of the drawing sheet. Gently adjust the sheet until its bottom edge is perfectly aligned with the top edge of the T-square blade.
Securing (Bottom Corners): While holding the T-square and sheet firmly, apply a small piece of masking tape (approximately 25mm long) to the bottom-left corner and then the bottom-right corner of the sheet, pressing it firmly to the board.
Securing (Top Corners): Without moving the T-square, lift the T-square slightly and apply tape to the top-left and top-right corners. Ensure the sheet remains flat and taut without wrinkles. Border lines define the drawing area and provide a clean finish.
Standard margins are typically: Left Edge: 20mm (to allow for binding or filing). Top, Bottom, Right Edges: 10mm.
Procedure: Measure 20mm from the left edge of the sheet and mark a few points along this line. Using a set square placed on the T-square, draw a light vertical line through these points. Measure 10mm from the top edge of the sheet and mark a few points. Using the T-square, draw a light horizontal line through these points. Repeat for the bottom and right edges (10mm from each). Darken the border lines using a suitable pencil (e.g., HB) once confident of their accuracy.
Understanding board practice extends beyond the classroom and is fundamental to many professional fields in Nigeria.
Architecture and Building Construction: Nigerian architects and building engineers rely heavily on precise technical drawings (blueprints) for designing houses, schools, hospitals, and commercial buildings. Accurate board practice ensures that floor plans, elevations, and sections are drawn to scale, clearly communicating design intentions to masons, carpenters, and other artisans on a construction site. Errors in basic drawing can lead to costly mistakes in building projects, for example, incorrect room dimensions or misaligned walls in a multi-story building in Lagos. Engineering (Civil, Mechanical, Electrical): In Nigeria's growing industrial sector, engineers use technical drawings to design everything from car parts and machinery to bridges and electrical circuits. A civil engineer designing a road network in Abuja needs precise line work to ensure correct alignment and gradients. Mechanical engineers in Port Harcourt's oil and gas sector use technical drawings for pipe fitting and equipment assembly. Electrical engineers in Enugu use them for wiring diagrams and panel layouts. The neatness and accuracy learned in board practice directly contribute to the safety and functionality of these engineered products.
Vocational Skills and Entrepreneurship: Artisans such as furniture makers (e.g., crafting tables and chairs in Aba), fashion designers (creating patterns for clothing), and welders (designing metal gates) can significantly improve the quality and efficiency of their work by first sketching and dimensioning their designs using technical drawing principles. Accurate drawing skills acquired through board practice enable them to plan their work effectively, minimize material waste, and produce high-quality products that meet client specifications, thereby enhancing their market competitiveness in Nigeria.