ZIMSEC O Level · Technical Graphics and Design · Form 1
Equipment
Drawing board and T-square (or a parallel motion board), set squares (45° and 30°/60°), protractor, compasses and dividers, scale rule, pencils (2H for construction lines, HB for outlines and lettering), eraser and templates.
Care of equipment
Keep edges clean and undamaged, sharpen pencils to a fine point, keep compasses tight, and store instruments safely.
Types of lines (to standard conventions)
- Thick continuous: visible outlines and edges.
- Thin continuous: construction, dimension and projection lines, hatching.
- Thin short dashes: hidden detail.
- Thin chain (long dash, short dash): centre lines and lines of symmetry.
- Thick chain at the ends: cutting planes for sections.
Lettering
Use single-stroke capital letters of uniform height (often 5 mm for notes, 7 mm for titles) between light guidelines.
Title block
Every drawing has a title block: title, name, scale, projection symbol, date and drawing number.
Scales
Full size 1 : 1; reduction 1 : 2, 1 : 5; enlargement 2 : 1.
Exam tip: Line quality is marked: outlines must be clearly darker than construction lines.
Check yourself
- Which pencil grade is used for construction lines?
- What type of line shows hidden detail?
- What does a scale of 1 : 2 mean?
Show answers
- 2H.
- Thin short dashes.
- The drawing is half the real size.
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