Drawing instruments, materials and standard conventions
Drawing instruments, materials and standard conventions
This domain tests whether you can set up a drawing sheet and use instruments to produce clean, standard-compliant work. The examiner looks for correct instrument choice, neat sheet layout and conventional line types rather than artistic effects.
Core rules
- Use a drawing board with a straight edge; check the T-square stock against the board edge before drawing horizontals. Set squares (45° and 30°–60°) must slide along the T-square blade, not be held freehand.
- Sharpen pencils to a long cone: H or 2H for construction and projection lines, HB for final outlines and lettering. Compass leads should be sharpened on sandpaper to a chisel point.
- An A3 sheet normally has a 20 mm binding margin on the left and 10 mm margins on the other three sides; the title block sits at the lower right. In India the first-angle projection symbol is standard.
- Visible outlines are continuous thick lines; hidden edges are short dashes; centre lines are long-short chains; dimension, extension and hatching lines are thin. Keep line widths in a consistent ratio, for example 0.5 mm thick and 0.25 mm thin.
- Keep instruments clean; erase construction lines lightly after inking, and never use a soft eraser on wet ink.
Worked example
To lay out an A3 landscape sheet, measure 20 mm from the left edge and 10 mm from the top, right and bottom. Draw the border with a 0.5 mm line. Place the title block in the lower-right corner, leaving room for the scale and projection symbol. Reason: the wider left margin is the filing edge, and the lower-right title block is read without turning the sheet.
Traps
Using the T-square on a damaged board edge, letting a set square slip, using a soft pencil for construction lines, and drawing hidden edges as thick continuous lines all lose marks. Also check that the sheet is fixed with tape at all four corners so it cannot shift.