Drawing Instruments, Materials and Basic Conventions
What the exam tests
The Drawing Instruments, Materials and Basic Conventions domain checks whether you can set up a sheet, use instruments correctly, and apply BIS line conventions without being told. Expect questions on T-squares, set squares, compass, divider, French curve, protractor, pencil grades, sheet sizes, title block, and the meaning of continuous, dashed, chain and cutting-plane lines.
Core rules
- Use a 2H or H pencil for construction and guide lines; use HB or B for final visible outlines and lettering where a darker line is required.
- A T-square draws horizontal lines only when its stock bears on the drawing board's working edge; never use it as a straightedge at an angle.
- Set squares give 30°, 45°, 60° and 90°; combined with the T-square they give 15° increments.
- Compass draws circles; divider transfers distances. Do not load a divider with graphite and use it as a compass.
- Border, title block and line conventions follow the drawing sheet layout; visible outlines are continuous thick, hidden edges dashed, centre lines chain thin.
Worked example
To draw a horizontal line 120 mm long through a point P, place the T-square stock against the board edge, slide it until the blade passes P, hold the blade, and draw left to right with a sharp 2H pencil. For a vertical through P, keep the T-square fixed and slide a 45° set square along the blade until its vertical edge passes P.
Traps
Using a blunt pencil or excessive pressure makes line widths inconsistent. Drawing hidden edges as continuous lines, or centre lines as dashed lines, loses convention marks. Do not erase construction lines until the final check, and never dimension to a construction line instead of the finished feature.