Drawing standards, conventions and graphical literacy
This domain tests whether you can set up a sheet and apply line conventions so a drawing reads unambiguously, and whether you can read technical graphics produced by someone else. Typical questions ask you to identify a line type, choose a sheet size, complete a title block or explain why a drawing is ambiguous.
Sheet layout and line groups
- ISO A-series: A0 is 841 x 1189 mm; each smaller size halves the larger dimension, so A4 is 210 x 297 mm.
- Frame margin, title block in the bottom right corner, parts list directly above the title block.
- ISO 128 pairs a thick line (0.5 or 0.7 mm) with a thin line (0.25 or 0.35 mm). Thick continuous = visible outlines; thin continuous = dimension, extension, leader and hatching lines; thin dashed = hidden edges; thin long-dash-dot = centre lines and pitch circles; thick long-dash-dot = cutting planes; thin zigzag = limits of partial views.
- Lettering to ISO 3098: vertical capitals, consistent height, no ornate strokes.
Projection and graphical literacy
First-angle drawings put the plan below the elevation; third-angle drawings put it above. The truncated-cone symbol in the title block declares which system applies. Graphical literacy means reading units, scales and limit tables, and extracting maximum, minimum and typical values from a chart.
Worked example
An A3 bracket drawing uses 0.7 mm outlines. Choose 0.35 mm for dimension, extension, hatching and centre lines, and 0.35 mm dashed for hidden detail. If the sheet is reduced to A4 at 71 percent, all widths shrink together; you do not redraw the thin lines thinner.
Traps
Hidden edges drawn as thick continuous lines; dimension lines drawn thick; holes shown without centre lines; a title block missing scale or projection symbol; outlines that stop short of a corner instead of meeting cleanly.