Drawing Instruments, Equipment and Materials
This domain tests whether you can select, set up, use and maintain the standard equipment of the drawing office, and whether your choice of instrument and pencil grade produces the line quality a marker expects.
Board, straightedge and set squares
Clamp the paper with masking tape near the corners, leaving the lower right area free for a title block. For right-handed work the T-square stock is held firmly against the left edge of the board; the blade then gives true horizontals, and set squares sliding on the blade give 90°, 45°, 30° and 60°. A damaged board edge or a slack stock produces lines that are not truly parallel, so check the stock before every drawing. Never cut on the board and never use the T-square as a hammer or a ruler for cutting.
Pencil grades and linework
Grades run from 9H (hardest, faintest) to 9B (softest, blackest). Use 2H for construction, projection and centre lines; H for hatching and lettering guide lines; HB or B for visible outlines and arrowheads. A conical point suits general linework; a chisel point gives even thick lines and lettering strokes. Blunt leads give woolly lines that smudge.
Paper and scales
ISO A-series paper has a side ratio of 1:√2. A0 is 841 × 1189 mm, A1 594 × 841, A2 420 × 594, A3 297 × 420 and A4 210 × 297 mm. Scales are plain, diagonal (reads to a second decimal place) or comparative, and the representative fraction is RF = drawing length ÷ actual length.
Worked example
A boundary wall 6 m long is to be drawn at 1:50. RF = 1/50 = 0.02; drawing length = 6000 mm × 0.02 = 120 mm. On a plain scale 120 mm long, mark 100 mm as the first major division, subdivide the left division into 10 parts (each 2 mm, representing 100 mm on site) and mark 0, 1, 2, 3 m to the right.
Traps that cost marks
Measuring along the drawing with the scale itself (it smudges and bends); using HB for construction lines so they cannot be distinguished from outlines; a blunt compass needle that wanders; drawing on the wrong edge of the board; using a set square alone to draw a horizontal.